Final Report Summary - STREAMLINE (Strategic Research For Innovative Marine Propulsion Concepts)
Executive Summary:
The objectives of the STREAMLINE project were to:
● Demonstrate radically new propulsion concepts delivering a step-change improvement of at least 15% efficiency over the current state-of-the-art.
● Investigate how to fully optimise current state-of-the-art systems including conventional screw propeller systems, pods and water jets.
● Develop advanced CFD tools and methods to optimise the hydrodynamic performance of the new ship propulsion systems, particularly by analysis of the integrated hull and propulsor.
● Characterise the operational aspects of each of the radically new propulsion concepts
These aims were addressed by focusing on 3 main areas:
WP1 - New Propulsion Concepts which included:
i. Large area propulsion system,
ii. Biomechanical system
iii. Distributed thrust system.
● WP2 - Optimisation of State-of-the-Art Propulsion which included: i) advanced screw propeller systems, ii) high-efficiency water jet at low speeds and iii) advanced pods.
● WP3 - CFD Methods and Tools.
The four year project completed in February 2014 with the following key outcomes:
● Analysis and tank tests have shown the Large Area Propeller achieving an efficiency improvement of between 12.5% and 15% with respect to the baseline.
● Large scale demonstrator testing of the biomechanical system was not possible during the project. However, significant CFD modelling was performed which indicates that the Walvisstaart propulsor in a vertical position is producing effective self-propulsion.
● CFD analysis and model tests indicate that the final performance of the vessel fitted with distributed propulsion was improved by approximately 25%.
● Results from the advanced screw concept indicate that large improvements of hydrodynamic performance are achievable and this concept would be viable to new builds.
● The work on the water jets has shown that although low speed performance can be improved, there is a significant detrimental impact on performance at high speed. However changes to the concept have been identified that could potentially improve the performance of the inlet leading to better high speed performance.
● The advanced pod concept was shown to have significant potential for improved efficiency,. With the predicted power for the contra-rotating propeller being 13.5% lower than the reference ship.
● A number of CFD tools were developed in STREAMLINE which have been shown to have the capability to be used for design tools within industry, with a reduction in computational effort and the operator skill required along with a corresponding increase in the ability to model complex geometries .
Project Context and Objectives:
Increasing environmental concerns and soaring oil prices are creating a new focus on fuel efficiency for the marine industry. Low emissions with demands for more advanced vessels than ever before drives the need for radically new propulsion concepts delivering a step-change in efficiency. STREAMLINE has been the response of the marine community to this demand.
The STREAMLINE project was broken down into 3 main areas:
● WP1 - New Propulsion Concepts;
● WP2 - Optimisation of State-of-the-Art Propulsion;
● WP3 - CFD Methods;
2.1. WP1 - New Propulsion Concepts
The first major objective of STREAMLINE has been to demonstrate radically new propulsion concepts, delivering a step-change improvement in efficiency of up to 15% over the current state-of-the-art.
The aim of STREAMLINE was to develop these concepts in both design and operational analysis to maximise the potential efficiency increases and translated potential cost saving to the end user.
This work package was split into three smaller work packages to develop three individual concepts:
● WP11 – Novel Application of the Large Area Propeller
● WP12 – Biomechanical Systems
● WP13 – Distributed Thrust
2.2. WP2 - Optimisation of State-of-the-Art Propulsion
In addition to considering new and more efficient propulsion concepts, there are many opportunities to optimise existing propulsion technologies and it is widely believed that reductions in fuel consumption and noxious emissions can be obtained.
The second major objective of STREAMLINE was to investigate different methods to fully optimise current state-of-the-art (SoA) systems including conventional screw propeller systems, pods, rudders and hull configurations, and water jets:
● For conventional screw propellers, and using advanced CFD tools; the study included the optimisation of blade shape and of special components such as propeller ducts, as well as inflow improving devices such as pre-swirl stators, vortex generators, equalizing ducts and rudder configurations by introducing twisted rudder designs. The performance of the optimized configurations was verified through an extensive experimental campaign and the reliability of CFD-based design tools developed within the project was assessed.
● For advanced pods; STREAMLINE focussed on the benefits of using pods in contra-rotating concepts (CRP), both improving the CRP-pod concept (single podded screw behind a main propeller) and the integrated contra-rotating pod (ICP). Using the new tools developed within the project, STREAMLINE investigated the use of the podded propulsor in different configurations on the ship’s hull, where previously the high risks of ventilation could not be properly assessed and avoided.
● For water jets the aim was to deliver higher propulsive efficiency over a wider range of operational conditions.
This work package was split into three smaller and more focussed work packages:
● WP21 – Advanced Screw Propeller Systems
● WP22 – High-Efficiency Water Jet at low speed
● WP23 – Advanced Pods
2.3. WP3 - CFD Methods
To achieve its first two objectives, STREAMLINE had to have access to new tools and methods for modelling performance aspects of propulsion technologies.
Consequently, the third major objective for STREAMLINE was to continue the development of advanced CFD tools and methods to optimise the hydrodynamic performance of the new ship propulsion systems. The CFD tools developed were used throughout the STREAMLINE project.
This work package was split into five smaller work packages to develop the CFD methods and tools:
WP31 - Development of Fixed-grid / Rotating-grid Coupling
WP32 - Grid Adaption
WP33 - Prediction of cavitation
WP34 - RANS / BEM Coupled Method
WP35 - Design Optimisation
Project Results:
3.1. WP11 – Novel application of the Large Area Propeller
By increasing the propeller diameter the propulsive efficiency is increased, but the size is limited by hull restrictions, and the difficulty is how this concept is applied to a vessel.
3.1.1. Design, optimisation, analysis and model testing
STREAMLINE has developed ways in which the Large Area Propeller can be configured on a vessel which are outside the conventional constraints of design. For example, placing the propeller below the baseline, and aft of the transom decreases the margin against ventilation.
The Inclined Keel Hull concept (IKH) has also been developed, where the propeller is in a conventional position under the ship, but there is an incline to the hull of 0.5 degrees.
Moving the propeller aft and increasing the area indicated a great potential for power reduction. From the resistance and self-propulsion tests it was found that the LAP for the optimised conventional variant of the 8000 DWT tanker showed some 13.5 % lower power consumption compared to the original design at design speed and up to 17%, at full power.
From these original results, attempts to further improve the configuration were then analysed. Firstly, systematic changes of the skeg/boss were carried out and an elongated boss stretching back to the propeller was found to be best, with a power reduction of 1% compared to the original hull with a long shaft to the propeller. This hull was then model tested at SSPA. Thereafter, a study was made of a bracket configuration, where one of the brackets was systematically turned to yield a pre-swirl of the inflow to the propeller. It was found that the power can be reduced compared to the case with brackets aligned with the flow, but the reduction was not large enough to compensate for the additional friction of the brackets.
As an alternative to the shafted propeller, a study was then carried out with a POD propulsion system and a modified hull.
Systematic changes of the hull in front of the POD resulted in a small reduction of power, as did the introduction of stabilizing fins instead of the skeg. However, the improvements were within 0.5%. The computed results indicated a gain in power between the best POD case and the original optimised hull by approximatley 3%.
Validations were completed, both for the computational technique with a zonal approach, used in all systematic computations, and a technique where the viscous free surface is modelled in the RANS code (VOF technique). Comparing the original propeller/hull configuration with the optimised hull/extra- large area propeller, the reduction in propulsive power was 15.0% for the zonal approach and 13.4% for the VOF approach. This should be compared with the gain of 14.2% in the SSPA tests. There is thus good correspondence between all three results. Full scale computations (zonal approach) indicated a somewhat smaller gain: 12.5% which should be compared with 13.5% for the extrapolated SSPA data obtained from the ITTC scaling procedure.
Ventilation studies were finally carried out using the ISIS-CFD flow solver by ECN/CNRS. A validation study was first carried out for a generic test case reported by RRHRC, where a propeller was run at a different submergences and rates of revolution below the free surface in a tunnel. Qualitative agreement with the data was achieved. Thereafter, seakeeping computations were carried out for the optimised 8000t tanker with the extra-large propeller at different sea states corresponding to tests at SSPA.
These tests verified that the assumed high efficiency for the concept can be expected in full scale. A reduction in propulsive power of about 15 % compared to the original design is a very big improvement. The tests also revealed that there is no problem with cavitation or high pressure pulses to be expected, manoeuvring properties are also good.
3.1.2. Inclined keel hull concept
The Inclined Keel Hull studies have addressed many of the operators concerns; propeller above baseline, moderate trim within capacity of existing on board ballast systems and propeller shaft speed within range of existing engines. The results from model test verification revealed a 4.3% maximum saving in the delivered power whilst the saving was 4% at the design speed. The findings confirmed the numerical predictions for power saving and hence supporting the worthiness of the IKH concept for the design applications of large commercial vessels.
3.1.3. Optimised Configurations Single screw propulsion
The objective was to perform power prediction using physical or real propeller geometry rotating in real time, which included full transient calculation.
Four different aft ships propulsion arrangements have been studied:
1. Single screw,
2. Twin screw Azipull,
3. Twin skeg – twin screw with conventional propellers,
4. Single screw with CRP (Contra Rotating Propeller - Azipull thruster behind a single screw propeller).
The selection of an optimal aft ship configuration for a specific application or operational profile type becomes ever more important to reduce fuel consumption and emissions and at least to add value to the ship owner.
The delivered power results of the sliding mesh CFD calculations are compared against their respective model test result. No model test results are available for the contra rotating propeller configuration (CRP) though. The results are normalised with the model test results for the single screw configuration – the reference vessel.
The ranking between the various aft ship configurations are obviously different in model test and CFD. It is difficult to state what effects explains the deviation. Some reasons could be:
● CFD analyses are performed in full scale and are compared with scaled model test results. There might be uncertainties in the scaling procedures from model test.
● The meshes in the CFD models might not have sufficient resolution in critical areas and there could be inaccuracy in the numerical schemes.
● Certain flow phenomena might not be captured in the CFD models, either by mesh or numerical schemes. There might be deviation in the geometry used in model test and CFD.
Before start of analysis the CRP configuration was believed to be the most efficient propulsion concept. With an aft propeller regaining the energy from the swirl of the front propeller, higher propulsion efficiency is expected. From the CFD results we actually see that the CRP hull has the highest delivered power. One reason is that the hull resistance is higher since there is more curvature in the aft body to make room for the propulsion system.
Different trends in the CFD results compared model tests and some uncertainties about the model tests make it difficult to rank the configurations. Having to choose figures for the LAP benchmark, the model test results will be used for the twin azipull (gain +3%) and the twin skeg (-1%). For the CRP the CFD results have to be used (gain -4%)
3.2. WP12 - Biomechanical System – The Walvistaart Pod
As a radical move away from conventional propellers, STREAMLINE has researched and developed the Walvisstaart Pod concept (WSP).
The main ship dimensions of the design are fixed at the typical Inland Waterways ship dimensions:
Loa = 110.00 m, Beam = 11.45 m, Depth = 5.55 m, at a maximum draught of 3.55 m.
The hull lines were optimised by MARIN using a non-linear potential flow programme RAPID. This programme computes the wave pattern and the inviscid flow along the hull to fully non-linear boundary conditions on the water surface. In the calculations, the dynamic trim and sinkage of the vessel have been computed and the hull attitude has been adjusted accordingly, to take into account their effect on the wave making.
A feasibility study of the direct drive system was completed. Comparisons were made between three different drive systems:
● Mechanical transmission: Using a diesel and connecting to a reduction gearbox.
● Hybrid Transmission: Using a diesel generator to drive a electro servo drive system.
● Direct Drive: Using a diesel generator and electro magnets to drive the blades.
Comparisons were made on these three systems in:
● Efficiency
● Reliability
● Design
● Cost
● Maintainability
● Flexibility
● and Safety.
It was concluded that the direct drive system is the most suitable solution for a rotating main wheel with four blades. This system was demonstrated to be the most efficient and economical manner to transmit the power to the blades. The main advantage being that this system would not require much maintenance, unlike the other concepts. This is due to the absence of mechanical parts.
Once the hull lines and the feasibility study had been completed, a detailed design of the WSP was completed, which included the following design points:
● The required efficiency improvement of 20-30%;
● Deformation at gearwheels and sealing;
● Lifetime of bearings and gearwheels;
● Stress and deformation of drive components;
● The ability to produce and mount the designed components;
● Cooling of the direct drive system;
● Sealing of the pod;
● Lubrication of the gearing;
● Control systems.
Within the original description of work, the operational testing of a full scale version of the Walvisstaart Pod was envisaged. The previous work completed in the detailed design was planned to be fed into the manufacturing process for the construction of the Pod and a suitable vessel, this would have been conducted outside the project and would have been funded by Walvisstaart. After the project completion, this vessel would have then been used by Walvisstaart to demonstrate the viability of their design and operational performance of the system. However, as a result of the financial crisis, Walvisstaart were unable to raise the necessary funding and the work was therefore not completed.
The structure of the work package was therefore changed to focus on the following aspects:
● Detailed design of the WSP in model scale;
- Hydrodynamic aspects,
- The blade motion patterns,
● Model scale WSP vessel design;
● Model scale construction, testing and evaluation.
● CFD computations to find operational performance and to validate the results.
3.2.1. Model scale design and testing
As the WSP is a complex system, MARIN first did a feasibility study to investigate if such complex system could be developed within the available time and budget. MARIN has completed work on the early design of the model test set-up. Within this design stage the following areas have been researched:
● How to measure the forces and dynamic loads applied to the blades;
● Electric mechanical drive and Direct electric drive;
● Scaling;
● Tolerance of the gears;
● Loading;
● Accuracy required.
There were uncertainties in the complex rotation of the blades, control systems, system tolerances, rotating reference disk, as well the level required for measurement accuracies. These uncertainties posed serious risks for the viability of the study which could have been solved if more time was available in the STREAMLINE project. As a result, the model scale design and testing by MARIN was discontinued.
3.2.2. CFD computations of operational performance
The aim was to apply the potential of enhanced CFD-based modelling developed within STREAMLINE to the WSP concept in full scale conditions.
Three progressive subtasks were therefore devised:
● Feasibility studies from 2D simplified model
This step was mandatory to precisely evaluate the risk in terms of possible CFD limitations. The dynamics of the WSP were precisely defined concerning the laws of motion in time of the rotating and oscillating bodies.
● Create a 3D numerical model of the ship and WSP. Precise definition of the ship and location of the WSP have to be defined relative to the ship hull.
● Simulation: model scale in design condition at prescribed trim & sinkage.
This CFD demonstrator, although not compared to measurements from model scale tests, shows that the considered Walvisstaart propeller in a vertical position is producing effective thrust and self-propulsion can be obtained. However, better knowledge of the flow is missing, particularly with regards to the impact of the shedding of strong vortical structures on the efficiency. Considering the flow complexity with interactions between the blades (vortices and boundary layers), the other uncertainty is in the turbulence modelling and the limitation in RANS approach. This is why it is mandatory for numerical simulations involving such complex geometries and flow conditions to be validated with model tests results.
3.3. WP13 - Distributed Thrust
Highly loaded propulsors that deliver poor efficiency are a feature common in many ship types including inland waterways vessels, fast ships and tug boats. An emerging alternative to the large area propulsor concepts highlighted earlier is to distribute thrust over multiple propulsors arranged around the ship hull:
The objectives of this area of research were to:
● Develop new methodologies to better predict air suction - a major factor affecting the hull design and size of the propulsors - and in this way improve propulsion efficiency.
● Carry out CFD modelling to derive the optimal distribution of multiple thrusters around the hull.
● Validate the distributed thrust concept with its optimal propulsors configuration through model testing.
● Evaluate the efficiency gains measured against benchmarks
The findings of WP13 have been assessed by the comparison with the experimentally investigated benchmark ship and the fully developed distributed thrust concept:
● CFD optimisation of the bare hull reduced the resistance by 22%, which is more than the 16% predicted.
● The developed of the hull displaces 3% more water, which can be exploited by a higher payload.
● CFD codes from WP3 to predict ventilation of the propellers were applied and validated successfully in this WP.
● A required thrust reduction of 38% has been found. However, due to a poor efficiency of the applied rudder propellers and stock propellers this significant thrust reduction leads to a power reduction of only 7%.
With the knowledge achieved within STREAMLINE work packages and the foreground knowledge gained, it was deemed feasible to exploit more than the thus far determined 7% power reduction; in particular when taking into account that the thrust demand was reduced by 38%. Therefore, the optimisation of the used rudder propellers was decided upon.
With the optimisation of the rudder propellers, the open water efficiency of the rudder propellers was improved by 21.5%, consequently the final performance of the vessel was improved by approximately 25%, while providing an increased cargo carrying capacity of 3%.
3.4. WP21 - Advanced Screw Propeller Systems
A primary aim of the STREAMLINE project was to develop and evaluate innovative marine propulsion concepts to achieve significant alleviation of environmental impact as well as reduction of operational costs. Nevertheless, it has been shown that enhanced CFD modelling/design techniques represent a powerful means to pursue consistent improvements of standard screw-propellers efficiency, without incurring major modifications to the overall propulsion layout.
The aim of this work package has been to explore the potential of enhanced CFD-based modelling and design techniques to achieve a new generation of high-performance screw propeller systems, these included:
● Vortex Generator (VG)
● Pre-swirl Stators (PSS)
● Boundary Layer Alignment Device (BLAD)
The analysis of model test results has allowed STREAMLINE to draw the following main conclusions for each of the design modifications addressed:
Optimised hull aft body and integrated propeller (H2+P2)
Results demonstrate that a totally new hull aft body design obtained by advanced CFD tools can determine large improvements of hydrodynamic performance. In this case, modified hull lines have been designed to fit a larger diameter propeller while preserving hull displacement and tip clearance of the baseline design. Delivered power at full scale (PDs) has been increased by 8.7%, and the inflow to the propeller is more homogeneous with lower pressure pulses and vibratory loads with respect to the baseline.
Tip-raked propeller (P3)
A tip-raked propeller (P3) optimised for the original hull form has achieved an increased open water efficiency of more than 3%. Unfortunately, efficiency gain at advance ratio corresponding to ship cruise speed is marginal and hence no improvement of delivered power PDs is observed while design propeller RPM is reduced about 1%.
Twisted rudders and pre-swirl stators
Two optimised propeller/rudder layouts (R1LE and R2) based on the twisted-rudder concept determine a reduction of PDs of approximately 1%. Similar power gains are obtained by introducing a pre-swirl stator (PSS) with 3 fins on portside.
3.4.1. WP21 Advanced Screw Propeller systems
3.4.2. Operational analysis
The operational analysis review indicates that the simplicity of the modifications to improve hydrodynamic performance of the reference vessel would mean that very little change would occur to the vessel. This in turn makes all the different ‘Advanced Screw Propeller systems’ concepts practically feasible options due to their inherent passive functioning for both new building or retrofitting purposes.
3.4.3. Cost-benefit analysis
Cost benefit analysis indicates that among the different ‘Advanced Screw Propeller System’ concepts, the P2 Propeller option combined with hull modification (H2) is more economically viable, but can only be applied to new builds. Out of the remaining concepts, which are all indeed retro-fit options, twisted rudder R1 is more economically viable.
3.5. WP22 - High-Efficiency Waterjet at low speeds
Water jet systems have been used for propulsion of vessels in the whole speed range up to, and even beyond 55 knots, with main applications in the speed range 25-45 knots. For lower speeds than 25 knots the industry relies mostly on propulsion systems based on conventional propeller technology. The combined needs of reduced fuel consumption, lower emissions and increasing demand for high vessel speeds leads to the need for new conceptual designs handling dual design targets both at high and low speed.
It has been the aim of STREAMLINE to investigate the potential to design high efficiency waterjet systems based on variable inlet/outlet geometries using existing and new actuation technology.
A number of different concepts have been evaluated until a single concept which was promising and realistic was found and was then taken forward to final design. This concept had an auxiliary channel that could be either active or passive.
Model testing in a towing tank, cavitation tunnel tests, as well as CFD simulations have been carried out and the final design to evaluate the classification and operational aspects of the concept.
During initial model tests in the cavitation tunnel it was shown that significant improvements in low speed efficiency were displayed, however at high speed the performance has not been as intended with a reduction in efficiency compared to the baseline.
Using the towing tank facilities at SSPA, both towing tank and self-propulsion tests were carried out. The results showed a good collaboration with the results previously obtained in the cavitation tunnel at the higher speeds which meant that the baseline inlet performed better than the new design, both with the auxiliary channel opened and closed. During bollard pull testing, no differences were displayed between the inlets but this is likely a consequence of the towing tank tests being performed at atmospheric conditions where the pump and inlet cavitation does not block the pump in the same way as it would do in the reduced pressure in the cavitation tunnel.
The numerical simulations of the bare hull resistance and self-propulsion tests showed a good agreement with the cavitation tunnel and towing tank tests, but some deviations were found in the results. These deviations in the results may have been due to a short fall in the simulations.
The operational and cost benefit analysis showed that the performance increase at low speed did not compensate for the losses at high speed, and thus there is no incitement for an operator to invest in the design, this is due to the increased production cost not being recuperated through the reduced fuel consumption. Improvements to the concept have been identified that could potentially improve the performance of the inlet but this would be at an additional cost in the manufacturing process.
3.6. W23 - Advanced Pods
Pod units have been used for ship propulsion for more than a decade, but are still a ‘novel’ propulsive unit compared to the conventional propeller on a shaft. In order to be a real competitor to conventional propulsion, both the total vessel efficiency and the propulsive efficiency have to be increased.
One solution is to use the pod in a contra-rotating concept. Another is to put a pod unit behind a conventional main propeller (Contra-rotating Pod, CRP). A second more promising solution (from an efficiency point of view) is to design a ‘true’ contra-rotating pod unit having two propellers close together either pushing or pulling (Integrated Contra-rotating Pod, ICP).
Within STREAMLINE the hydrodynamic performance of propulsive systems, based on contra-rotating propellers and podded propellers, has been analysed through computational modelling. This computational analysis has been performed by means of the hybrid RANSE/BEM model developed by CNR-INSEAN. The methodology aims at combining the capability of RANSE to describe viscous flows around ship hulls and the capability of inviscid flow BEM models to predict reduced computational effort propeller forces. The Cavitation and ventilation behaviour of podded propulsors in service conditions has also been studied using a computational model developed by CNRS providing an improved knowledge on the interaction of cavitation and ventilation, the assessment of ventilation risks in the design phase has been improved.
Through computational modelling and scale model testing, the savings for the CRP and the ICP have been considerable, compared to the reference ship used. The predicted power for the CRP is 13.5% lower than the reference ship, and the corresponding figure for the ICP is 11%.
Due to these results, throughout the third period, the ICP and CRP concepts were further developed. The reduction in power consumption compared to the previous ICP was 1% and compared to the reference RoRo ship it is in the order of 12%.
The manoeuvre simulations for the CRP also showed that it is possible to control the ship in all weather conditions tested when running in normal conditions, i.e. both propellers running and pod used for steering. The conditions tested covered wind velocities up to 22.6 m/s mean wind and significant wave heights up to 5.6 m. With one propeller stopped, it was demonstrated that it is still possible to control the ship in weather conditions up to Bft8, only using the pod.
3.6.1. Operational Analysis
With a conventional propeller and pod working together, they offer an improved propulsive efficiency, enhanced manoeuvrability, redundancy and flexibility with respect to the changing operating conditions. Both CRP and ICP will be more expensive and complicated in installation and operation.
A single propulsion unit cannot offer the same level of redundancy as the combination of pod and propeller though the manoeuvrability and flexibility will be similar. In the short term, CRP is considered to be much more realistic and practicable, cost effective and more reliable than ICP. However, in the long term, ICP may become cost effective when it gains popularity and becomes part of mainstream technology.
3.6.2. Cost-Benefit Analysis
Cost benefit analysis considering a twin screw reference ship indicates that CRP is economically superior compared to that of the conventional propulsion system, whereas the ICP is economically inferior compared to that of the conventional propulsion system.
3.7. WP3 Advanced CFD Tools
The tools developed within STREAMLINE have been used throughout the project and have been an integral part in the development of the operational technologies. STREAMLINE has shown that CFD tools have the capability to be used as design tools within industry, with a reduction in computational effort and the operator skill level required.
With these new CFD capabilities designers are now able to search for the limits in propeller design. The tools developed within the project are being used today in commercial projects by the STREAMLINE partners.
The following codes were used throughout WP3:
FreSCo+
The finite-volume simulation procedure FreSCo+ has been enhanced to address the specific aspects of advanced propulsion units and their hydrodynamic interplay with the hull as well as (in)flow manipulating devices. Extensions implemented and applied refer to a conservative overset-grid-coupling technology for unstructured moving/deformable grids. The enhancements have been demonstrated to provide the required flexibility and predictive accuracy to investigate problems featuring complex dynamics, e.g. cycloidal/biomechanical propellers or propeller/rudder-interaction. Due to the complex relative motion and dynamics of advanced propulsion units working in behind conditions, the parallel efficiency suffers a from static parallel environment. Accordingly, attention has also been given to dynamic load balancing aspects to improve the speed-up of the implementation which is a major aspect of the industrial usability. Moreover, local grid refinement strategies and vortex supporting techniques have been included under the aegis of STREAMLINE. Grid-refinement criteria have been formulated in accord with an adjoint-based optimisation approach to secure that the actual simulation goal is supported by the grid-refinement process. All aspects have been harmonised with important existing features, e.g. RANS/BEM coupling, gradient-based optimisation, 6 DOF and seaway models etc.
ISIS-CFD
A research code to simulate fully unstructured viscous flows devoted to ship hydrodynamics has been developed. The main results have been the validation of the existing potential capabilities of the code though the various industrial cases proposed in various WP at both model and full scale. STREAMLINE has demonstrated the capability to compute very complex geometries with the propeller in waves through the sliding grid technique from a unique hexahedral unstructured grid and 6 D.o.F (Degrees of Freedom) resolution. This provides an optimum use of grid points and CPU with automatic grid refinement, with load balancing suitable for free-surface capturing, cavitation modelling and other physical based criteria. This has demonstrated a reduced CPU time from a simplified propeller model (BEM model, AD model) and quasi-static approach.
PRO-INS
A Boundary Element Method solver for the hydrodynamic analysis of marine propulsion systems has been developed. This solver includes general interfaces to be coupled with ship viscous-flow solvers operating in hybrid RANS/BEM mode, and with numerical optimisation models to perform shape optimisation studies. The solver can be applied to analyse various types of marine propulsors: fixed-pitch, variable-pitch propellers, ducted propellers, podded propellers.
Chi-Navis
A finite-volume viscous-flow solver based on RANS, DES, LES solutions of the unsteady Navier-Stokes equations. Solver features include: dynamic overlapping grids, level-set free surface model, library of turbulence models, 'body-force' propeller models, multi-body 6 DOF dynamics; multi-paradigm parallelisation. This provides very accurate viscous flow predictions, describing marine vehicles in arbitrary motions. Overlapping grids allow the building of high-quality computational grids at reduced effort; DES and LES allow the description of complex turbulent and vortical structures; propellers can be explicitly solved or modelled via hybrid RANSE/BEM scheme.
Kurgan
A hydroacoustic solver based on the numerical solution of the Ffowcs-Williams and Hawkings equations. This solver is based on a Boundary Element Method generalised to include volume integral contributions. The solver allows the analysis of propagation and scattering of hydrodynamic noise sources on marine vehicles including the effects of the propulsion system. The methodology provides a unique approach to detect broadband noise sources associated to flow turbulence and vortical structures. Interfaces with CFD solvers based on RANS and DES/LES have been developed.
HyPPO
A computational platform for general purpose numerical optimization problems. The platform includes a variety of computational schemes for single-objective or multi-objective optimization, robust optimization, and local as well as global search algorithms. This numerical optimisation platform is very general. Ship performance optimisation can be studied as a shape optimisation problem through new techniques. These numerical optimisation models can be easily interfaced with CFD solvers like "Chi-Navis" and "PRO-INS".
3.8. WP31 Development of Fixed-grid/Rotating-grid Coupling
The development of CFD tools to simulate the propulsor action behind a ship hull, and interaction of these objects. This work package was split into three CFD methods:
● Task 31.1 - Mesh coupling using a sliding grid approach (CNRS, MARIN)
● Task 31.2 - Mesh coupling using overlapping grids (TUHH, HSVA)
● Task 31.3 - Comparisons of various coupling strategies and error (CNRS, MARIN, HSVA, TUHH)
Sliding grid capability in ReFRESCO and ISIS-CFD has been developed. This will provide an extension to the existing software whereby it may be implemented as a design tool to provide a more accurate result in propeller modelling for propellers behind stationary ships or stators.
With the development and implementation of the overlap grid feature in FreSCO+, this provides the capability of simulating objects moving against each other in domains made of multiple grids.
3.9. WP 32 Grid Adaption
The work package covers the development in automatic grid adaption during the CFD computation to simulate flow details such air suction, cavitation, pressure fluctuations, erosion or the footprint of vortex generators, and the interaction of these conditions on different thrusters or propulsors.
STREAMLINE has demonstrated an improved grid refinement technology in ReFRESCO, Fresco+, ISIS-CFD, and OpenFOAM software, allowing for a higher grid resolution locally in highly transient flows, this will be effective for large scale parallel computations, and thus improved predictive capability
Compressible viscous flow code with cavitation modelling capability has been improved; this provides the most complete computational model of cavitating flow phenomena developed to date. It also allows for the study into the effect of vapour compressibility in the collapse of the cavity, and the acoustic effects on the near and far field.
3.10. WP33 Prediction of cavitation
The work package covers the development of state-of-the-art cavitation modelling, and the investigation of CFD methods to define a direct characterization of pressure fluctuations and its harmful consequences on marine propulsion systems in terms of erosion risk for propellers and rudders.
Cavitation modelling capability in ReFRESCO and ISIC-CFD has been developed, providing the ability to predict cavitation.
Propeller-induced pressure fluctuations and radiated noise have been investigated by the novel Ffowcs-Williams and Hawkings methodology implemented into the Kurgan code and by a Kirchhoff-Helmholtz methodology implemented into the Excalibur code.
The following software codes were used throughout WP33:
● ISIS-CFD
● ReFRESCO
● PRO-INS
● Chi-Navis
● Kurgan
● Excalibur
● OpenFOAM
3.11. WP34 RANS / BEM Coupled Method
The work package covers the development of efficient RANS / BEM coupling to provide a cost effective approach to investigating hull-propeller interaction and to predict self-propulsion conditions with sufficient accuracy.
A RANS-BEM coupling software code has been developed, providing fast computations of resistance and propulsion characteristics of hull-propeller combination. The implementation and improvement of the RANS / BEN interface has also been developed, providing an improved simulation procedure using the newly developed RANS-BEM coupling software code.
The following software codes were used throughout WP34:
● ISIS-CFD, Chi-Navis, Parnassos, FRESCO+ (RANSE)
● PRO-INS, QCM, PROCAL (BEM)
3.12. WP35 Design Optimisation
The work package covers the development and assessment of numerical optimisation techniques and automated design procedures, by the improvement of existing numerical optimisation tools. It also includes the revision and update of design procedures to increase the impact of simulation tools and technologies.
The software code for the optimisation of the strategy for ship-propeller interaction has been developed. This provided the optimisation of the aft bodies of ships, taking into account the propeller-hull interaction propellers.
The software code for ‘Free Form Deformation Technique’ has been developed. This provides an optimisation process that reduces the required use of licensed third party software, reducing the required user interaction.
PRO-INS and HyPPO codes were used throughout WP35.
Potential Impact:
5. Impact and Exploitation of Results
5.1. WP11 - Large Area Propeller
Through the research carried out within the STREMLINE project, Rolls-Royce is proposing to further develop the large area propeller technology in 2 parallel development projects. The results generated by the STREAMLINE developed methods and tools have been very important in the decision making process to exploit the Large Area Propeller technology beyond the STREAMLINE project.
The first project to exploit the technology is within the LEANShip consortia, where we aim at demonstrating the Large Area Propeller technology on a series vessel together with a European ship operator, yard and research organisation. The aim is to optimise the vessel and a large area propeller within the current design space with minor modifications required. With these constraints we expect to improve the propulsive efficiency up to 10%.
The second project to exploit the technology is through a UK funded Rolls-Royce led demonstrator. In this project we aim at fully exploit the potential of the large area propeller where we expect an improvement in propulsive efficiency of between 15-20% across several vessel types.
5.2. WP12 - Walvistaart Pod
Through the research carried out within STREAMLINE the project has demonstrated, with the use of CFD tools developed within the project, that the concept has the potential to provide the efficiency and power improvements envisaged over a conventional propeller system. The feasibility study conducted by MARIN showed that although the production and testing of a model was not achievable within STREAMLINE, it would be achievable as a future project.
Despite the advancements made within STREAMLINE, the Walvistaart Pod is still in the ‘concept’ phase. Therefore, there is still a requirement for further development of this technology, this will include:
● Analysis of the 2D, and 3D computations.
● Model scale testing must be completed to validate the CFD conclusions.
Once the concept has been developed the CFD computations have been validated and the system has displayed the results that are envisaged, it is planned that the WS group will:
● Complete financing of inland navigation ship.
● Find a producer for the POD.
● Order and build a vessel.
● Extensive test trials with a vessel.
● Continue to improve design in particular size and weight.
● Develop seagoing POD.
● Develop a smaller POD for Yacht industries.
5.3. WP13 - Distributed Thrust
The concept has shown good improvements beyond the SoA, with potential operational cost reductions of up to 10%, and potential fuel savings of up to 25%. STREAMLINE has demonstrated that the concept has applications within the European Maritime Market within inland shipping, with the potential to reduce road congestion and meet CO2 regulations and targets.
DST will be raising proposals in the first call of H2020 2014 within MG4.1 and MG4.4 for the further development of what has been achieved within the STREAMLINE project.
The STREAMLINE Benchmark Ship is being used within National German funded projects:
● Skate
● Wake
CNRS will use 2 Phase CFD Code in research projects to predict the air suction of the propulsion systems. The functionality of the code is now fully integrated into the commercial code licence, and can be used commercially.
ZF will be integrating the improved housing geometry for their rudder propeller designs. A project is now being derived to optimise the hydrodynamic performance of the azimuth thruster. Within this project, further development of the rudder propellers developed within STREAMLINE will be conducted with the aim to:
● Optimise the shape of the thruster.
● Improve the thruster body resistance and improve the wake field in the behind condition.
● Reduce running costs of the thruster.
● Improve the influence of the propeller on hull.
The research carried out and results obtained within the STREAMLINE project will be applied to the entire ZF thruster range.
5.4. WP21 - Advanced Screw Propeller Systems
With a combined optimisation of both the hull and propeller, the aim of increasing efficiency propulsive power reductions of by 8-9% have been displayed, with the potential of reducing operational cost and environmental impact.
The STREAMLINE Tanker Data set developed within STREAMLINE is at present being used within FP7 projects GRIP and SONIC. This is being used as a reference case, and therefore having a valued impact on present EC funded projects and their results.
The simulation based designs and optimisation tools developed for the hull propulsors are the subject of proposals being applied for within H2020, these include:
● Optimised Propeller;
● Twisted rudder, with combination of the ESDs within the to the propeller inflow.
Retrofit solutions with a combination of ESDs within the propeller inflow are also being addressed in H2020 projects for the application of optimised rudder and propeller configurations.
5.5. WP22 – Water jet at low speed
Following the results obtained within STREAMLINE, further analysis of the concept is required. The aim is therefore to expand of the scope of the design for the whole water jet system. The concept may be taken further and adapted for the ferry operations, from this further developments will be made in:
● The improvement of operations at low speed;
● An increase in power demand at high speed;
● An evaluation of total fuel consumption.
Experimental and numerical tools, verified through STREAMLINE, will be utilised for any future development and optimisation of the concept.
5.6. WP23 – Advanced Pods
Further development of the CRP and ICP concepts by SSPA will be dependent upon the market conditions; therefore SSPA may be bringing the CRP concept forward into H2020 proposals. At present the design of the CRP concept is being used by Rolls Royce in the design and build of a small vessel.
The ventilation experiments in a depressurised environment, conducted by MARIN have been:
● Used in demonstrations to large groups of customers
● Applied in several commercial projects (PODs and regular propellers)
● Applied in offshore industry (thruster ventilation)
5.7. WP31 – Development of Fixed Grid and Rotating Grid Coupling
Advancements within the development of the sliding interface and the overset-grid methodology have been significant.
These sliding interface techniques are being utilised within the following FP7 projects and joint industry projects, having a valued impact on present EC funded projects and the results there of:
● GRIP
● Refit2Save
● THRUST
The use of sliding interface techniques are being used for the development and design of Tidal Turbines by MARIN. This is being proposed within HORIZON 2020 project ‘RESTORE’, for the further development of this technology within the commercial sector.
The existing sliding interface technology implemented by ECN/CNRS in their in-house research flow solver ISIS-CFD was used and validated throughout the STREAMLINE project. It is available in the commercial version FINETM/Marine and mainly used in marine industry to take account for propeller effects.
5.8. WP32 – Grid Adaption
The Grid Adaptation techniques are being used within Commercial and Defence projects by MARIN. These techniques have now been developed further to include pressure fluctuations on the hull. They are also being used within the FP7 project SONIC to determine underwater radiated noise.
The Automatic Grid Refinement technique by ECN/CNRS in their in-house research flow solver ISIS-CFD was used and validated throughout the STREAMLINE project. It is available in the commercial version FINETM/Marine and used in the marine industry, mainly for sea transport, and also from naval architects for sailing boats.
5.9. WP33 - Prediction of Cavitation
The ventilation and erosion prediction solvers developed within STREAMLINE are being used to perform virtual experiments, and are being used in the decision making process at the design stage of new systems. These computational models developed are also being used at present within the assessment of innovative concepts for new projects.
5.10. WP34 - RANS/BEM Coupled Method
Hybrid solvers have now been shown to be suitable for application as software for industrial design, and are being used within new projects by CNR- INSEAN addressing the greening of marine transports as well as the development of marine current turbines. These tools are also being used by HSVA within Commercial, National and EU projects on a daily basis.
Since 2013 the RANS-BEM Coupled Method developed within STREAMLINE has been used within commercial projects by MARIN, as well as within the FP7 project GRIP.
MARIN will be utilising these design studies within H2020 projects and will use this methodology in the design on their propulsion systems.
5.11. WP35 – Design Optimisation
Tools developed within STREAMLINE are being used with National Projects by HSVA, and commercial projects by MARIN for both hull and duct techniques. MARIN have now extended these methods to include free-surface waves and will be utilising these techniques in future projects. The numerical optimization platform developed by CNR-INSEAN is currently used in commercial projects and will be proposed for R&D projects under H2020.
List of Websites:
www.streamline-project.eu
The objectives of the STREAMLINE project were to:
● Demonstrate radically new propulsion concepts delivering a step-change improvement of at least 15% efficiency over the current state-of-the-art.
● Investigate how to fully optimise current state-of-the-art systems including conventional screw propeller systems, pods and water jets.
● Develop advanced CFD tools and methods to optimise the hydrodynamic performance of the new ship propulsion systems, particularly by analysis of the integrated hull and propulsor.
● Characterise the operational aspects of each of the radically new propulsion concepts
These aims were addressed by focusing on 3 main areas:
WP1 - New Propulsion Concepts which included:
i. Large area propulsion system,
ii. Biomechanical system
iii. Distributed thrust system.
● WP2 - Optimisation of State-of-the-Art Propulsion which included: i) advanced screw propeller systems, ii) high-efficiency water jet at low speeds and iii) advanced pods.
● WP3 - CFD Methods and Tools.
The four year project completed in February 2014 with the following key outcomes:
● Analysis and tank tests have shown the Large Area Propeller achieving an efficiency improvement of between 12.5% and 15% with respect to the baseline.
● Large scale demonstrator testing of the biomechanical system was not possible during the project. However, significant CFD modelling was performed which indicates that the Walvisstaart propulsor in a vertical position is producing effective self-propulsion.
● CFD analysis and model tests indicate that the final performance of the vessel fitted with distributed propulsion was improved by approximately 25%.
● Results from the advanced screw concept indicate that large improvements of hydrodynamic performance are achievable and this concept would be viable to new builds.
● The work on the water jets has shown that although low speed performance can be improved, there is a significant detrimental impact on performance at high speed. However changes to the concept have been identified that could potentially improve the performance of the inlet leading to better high speed performance.
● The advanced pod concept was shown to have significant potential for improved efficiency,. With the predicted power for the contra-rotating propeller being 13.5% lower than the reference ship.
● A number of CFD tools were developed in STREAMLINE which have been shown to have the capability to be used for design tools within industry, with a reduction in computational effort and the operator skill required along with a corresponding increase in the ability to model complex geometries .
Project Context and Objectives:
Increasing environmental concerns and soaring oil prices are creating a new focus on fuel efficiency for the marine industry. Low emissions with demands for more advanced vessels than ever before drives the need for radically new propulsion concepts delivering a step-change in efficiency. STREAMLINE has been the response of the marine community to this demand.
The STREAMLINE project was broken down into 3 main areas:
● WP1 - New Propulsion Concepts;
● WP2 - Optimisation of State-of-the-Art Propulsion;
● WP3 - CFD Methods;
2.1. WP1 - New Propulsion Concepts
The first major objective of STREAMLINE has been to demonstrate radically new propulsion concepts, delivering a step-change improvement in efficiency of up to 15% over the current state-of-the-art.
The aim of STREAMLINE was to develop these concepts in both design and operational analysis to maximise the potential efficiency increases and translated potential cost saving to the end user.
This work package was split into three smaller work packages to develop three individual concepts:
● WP11 – Novel Application of the Large Area Propeller
● WP12 – Biomechanical Systems
● WP13 – Distributed Thrust
2.2. WP2 - Optimisation of State-of-the-Art Propulsion
In addition to considering new and more efficient propulsion concepts, there are many opportunities to optimise existing propulsion technologies and it is widely believed that reductions in fuel consumption and noxious emissions can be obtained.
The second major objective of STREAMLINE was to investigate different methods to fully optimise current state-of-the-art (SoA) systems including conventional screw propeller systems, pods, rudders and hull configurations, and water jets:
● For conventional screw propellers, and using advanced CFD tools; the study included the optimisation of blade shape and of special components such as propeller ducts, as well as inflow improving devices such as pre-swirl stators, vortex generators, equalizing ducts and rudder configurations by introducing twisted rudder designs. The performance of the optimized configurations was verified through an extensive experimental campaign and the reliability of CFD-based design tools developed within the project was assessed.
● For advanced pods; STREAMLINE focussed on the benefits of using pods in contra-rotating concepts (CRP), both improving the CRP-pod concept (single podded screw behind a main propeller) and the integrated contra-rotating pod (ICP). Using the new tools developed within the project, STREAMLINE investigated the use of the podded propulsor in different configurations on the ship’s hull, where previously the high risks of ventilation could not be properly assessed and avoided.
● For water jets the aim was to deliver higher propulsive efficiency over a wider range of operational conditions.
This work package was split into three smaller and more focussed work packages:
● WP21 – Advanced Screw Propeller Systems
● WP22 – High-Efficiency Water Jet at low speed
● WP23 – Advanced Pods
2.3. WP3 - CFD Methods
To achieve its first two objectives, STREAMLINE had to have access to new tools and methods for modelling performance aspects of propulsion technologies.
Consequently, the third major objective for STREAMLINE was to continue the development of advanced CFD tools and methods to optimise the hydrodynamic performance of the new ship propulsion systems. The CFD tools developed were used throughout the STREAMLINE project.
This work package was split into five smaller work packages to develop the CFD methods and tools:
WP31 - Development of Fixed-grid / Rotating-grid Coupling
WP32 - Grid Adaption
WP33 - Prediction of cavitation
WP34 - RANS / BEM Coupled Method
WP35 - Design Optimisation
Project Results:
3.1. WP11 – Novel application of the Large Area Propeller
By increasing the propeller diameter the propulsive efficiency is increased, but the size is limited by hull restrictions, and the difficulty is how this concept is applied to a vessel.
3.1.1. Design, optimisation, analysis and model testing
STREAMLINE has developed ways in which the Large Area Propeller can be configured on a vessel which are outside the conventional constraints of design. For example, placing the propeller below the baseline, and aft of the transom decreases the margin against ventilation.
The Inclined Keel Hull concept (IKH) has also been developed, where the propeller is in a conventional position under the ship, but there is an incline to the hull of 0.5 degrees.
Moving the propeller aft and increasing the area indicated a great potential for power reduction. From the resistance and self-propulsion tests it was found that the LAP for the optimised conventional variant of the 8000 DWT tanker showed some 13.5 % lower power consumption compared to the original design at design speed and up to 17%, at full power.
From these original results, attempts to further improve the configuration were then analysed. Firstly, systematic changes of the skeg/boss were carried out and an elongated boss stretching back to the propeller was found to be best, with a power reduction of 1% compared to the original hull with a long shaft to the propeller. This hull was then model tested at SSPA. Thereafter, a study was made of a bracket configuration, where one of the brackets was systematically turned to yield a pre-swirl of the inflow to the propeller. It was found that the power can be reduced compared to the case with brackets aligned with the flow, but the reduction was not large enough to compensate for the additional friction of the brackets.
As an alternative to the shafted propeller, a study was then carried out with a POD propulsion system and a modified hull.
Systematic changes of the hull in front of the POD resulted in a small reduction of power, as did the introduction of stabilizing fins instead of the skeg. However, the improvements were within 0.5%. The computed results indicated a gain in power between the best POD case and the original optimised hull by approximatley 3%.
Validations were completed, both for the computational technique with a zonal approach, used in all systematic computations, and a technique where the viscous free surface is modelled in the RANS code (VOF technique). Comparing the original propeller/hull configuration with the optimised hull/extra- large area propeller, the reduction in propulsive power was 15.0% for the zonal approach and 13.4% for the VOF approach. This should be compared with the gain of 14.2% in the SSPA tests. There is thus good correspondence between all three results. Full scale computations (zonal approach) indicated a somewhat smaller gain: 12.5% which should be compared with 13.5% for the extrapolated SSPA data obtained from the ITTC scaling procedure.
Ventilation studies were finally carried out using the ISIS-CFD flow solver by ECN/CNRS. A validation study was first carried out for a generic test case reported by RRHRC, where a propeller was run at a different submergences and rates of revolution below the free surface in a tunnel. Qualitative agreement with the data was achieved. Thereafter, seakeeping computations were carried out for the optimised 8000t tanker with the extra-large propeller at different sea states corresponding to tests at SSPA.
These tests verified that the assumed high efficiency for the concept can be expected in full scale. A reduction in propulsive power of about 15 % compared to the original design is a very big improvement. The tests also revealed that there is no problem with cavitation or high pressure pulses to be expected, manoeuvring properties are also good.
3.1.2. Inclined keel hull concept
The Inclined Keel Hull studies have addressed many of the operators concerns; propeller above baseline, moderate trim within capacity of existing on board ballast systems and propeller shaft speed within range of existing engines. The results from model test verification revealed a 4.3% maximum saving in the delivered power whilst the saving was 4% at the design speed. The findings confirmed the numerical predictions for power saving and hence supporting the worthiness of the IKH concept for the design applications of large commercial vessels.
3.1.3. Optimised Configurations Single screw propulsion
The objective was to perform power prediction using physical or real propeller geometry rotating in real time, which included full transient calculation.
Four different aft ships propulsion arrangements have been studied:
1. Single screw,
2. Twin screw Azipull,
3. Twin skeg – twin screw with conventional propellers,
4. Single screw with CRP (Contra Rotating Propeller - Azipull thruster behind a single screw propeller).
The selection of an optimal aft ship configuration for a specific application or operational profile type becomes ever more important to reduce fuel consumption and emissions and at least to add value to the ship owner.
The delivered power results of the sliding mesh CFD calculations are compared against their respective model test result. No model test results are available for the contra rotating propeller configuration (CRP) though. The results are normalised with the model test results for the single screw configuration – the reference vessel.
The ranking between the various aft ship configurations are obviously different in model test and CFD. It is difficult to state what effects explains the deviation. Some reasons could be:
● CFD analyses are performed in full scale and are compared with scaled model test results. There might be uncertainties in the scaling procedures from model test.
● The meshes in the CFD models might not have sufficient resolution in critical areas and there could be inaccuracy in the numerical schemes.
● Certain flow phenomena might not be captured in the CFD models, either by mesh or numerical schemes. There might be deviation in the geometry used in model test and CFD.
Before start of analysis the CRP configuration was believed to be the most efficient propulsion concept. With an aft propeller regaining the energy from the swirl of the front propeller, higher propulsion efficiency is expected. From the CFD results we actually see that the CRP hull has the highest delivered power. One reason is that the hull resistance is higher since there is more curvature in the aft body to make room for the propulsion system.
Different trends in the CFD results compared model tests and some uncertainties about the model tests make it difficult to rank the configurations. Having to choose figures for the LAP benchmark, the model test results will be used for the twin azipull (gain +3%) and the twin skeg (-1%). For the CRP the CFD results have to be used (gain -4%)
3.2. WP12 - Biomechanical System – The Walvistaart Pod
As a radical move away from conventional propellers, STREAMLINE has researched and developed the Walvisstaart Pod concept (WSP).
The main ship dimensions of the design are fixed at the typical Inland Waterways ship dimensions:
Loa = 110.00 m, Beam = 11.45 m, Depth = 5.55 m, at a maximum draught of 3.55 m.
The hull lines were optimised by MARIN using a non-linear potential flow programme RAPID. This programme computes the wave pattern and the inviscid flow along the hull to fully non-linear boundary conditions on the water surface. In the calculations, the dynamic trim and sinkage of the vessel have been computed and the hull attitude has been adjusted accordingly, to take into account their effect on the wave making.
A feasibility study of the direct drive system was completed. Comparisons were made between three different drive systems:
● Mechanical transmission: Using a diesel and connecting to a reduction gearbox.
● Hybrid Transmission: Using a diesel generator to drive a electro servo drive system.
● Direct Drive: Using a diesel generator and electro magnets to drive the blades.
Comparisons were made on these three systems in:
● Efficiency
● Reliability
● Design
● Cost
● Maintainability
● Flexibility
● and Safety.
It was concluded that the direct drive system is the most suitable solution for a rotating main wheel with four blades. This system was demonstrated to be the most efficient and economical manner to transmit the power to the blades. The main advantage being that this system would not require much maintenance, unlike the other concepts. This is due to the absence of mechanical parts.
Once the hull lines and the feasibility study had been completed, a detailed design of the WSP was completed, which included the following design points:
● The required efficiency improvement of 20-30%;
● Deformation at gearwheels and sealing;
● Lifetime of bearings and gearwheels;
● Stress and deformation of drive components;
● The ability to produce and mount the designed components;
● Cooling of the direct drive system;
● Sealing of the pod;
● Lubrication of the gearing;
● Control systems.
Within the original description of work, the operational testing of a full scale version of the Walvisstaart Pod was envisaged. The previous work completed in the detailed design was planned to be fed into the manufacturing process for the construction of the Pod and a suitable vessel, this would have been conducted outside the project and would have been funded by Walvisstaart. After the project completion, this vessel would have then been used by Walvisstaart to demonstrate the viability of their design and operational performance of the system. However, as a result of the financial crisis, Walvisstaart were unable to raise the necessary funding and the work was therefore not completed.
The structure of the work package was therefore changed to focus on the following aspects:
● Detailed design of the WSP in model scale;
- Hydrodynamic aspects,
- The blade motion patterns,
● Model scale WSP vessel design;
● Model scale construction, testing and evaluation.
● CFD computations to find operational performance and to validate the results.
3.2.1. Model scale design and testing
As the WSP is a complex system, MARIN first did a feasibility study to investigate if such complex system could be developed within the available time and budget. MARIN has completed work on the early design of the model test set-up. Within this design stage the following areas have been researched:
● How to measure the forces and dynamic loads applied to the blades;
● Electric mechanical drive and Direct electric drive;
● Scaling;
● Tolerance of the gears;
● Loading;
● Accuracy required.
There were uncertainties in the complex rotation of the blades, control systems, system tolerances, rotating reference disk, as well the level required for measurement accuracies. These uncertainties posed serious risks for the viability of the study which could have been solved if more time was available in the STREAMLINE project. As a result, the model scale design and testing by MARIN was discontinued.
3.2.2. CFD computations of operational performance
The aim was to apply the potential of enhanced CFD-based modelling developed within STREAMLINE to the WSP concept in full scale conditions.
Three progressive subtasks were therefore devised:
● Feasibility studies from 2D simplified model
This step was mandatory to precisely evaluate the risk in terms of possible CFD limitations. The dynamics of the WSP were precisely defined concerning the laws of motion in time of the rotating and oscillating bodies.
● Create a 3D numerical model of the ship and WSP. Precise definition of the ship and location of the WSP have to be defined relative to the ship hull.
● Simulation: model scale in design condition at prescribed trim & sinkage.
This CFD demonstrator, although not compared to measurements from model scale tests, shows that the considered Walvisstaart propeller in a vertical position is producing effective thrust and self-propulsion can be obtained. However, better knowledge of the flow is missing, particularly with regards to the impact of the shedding of strong vortical structures on the efficiency. Considering the flow complexity with interactions between the blades (vortices and boundary layers), the other uncertainty is in the turbulence modelling and the limitation in RANS approach. This is why it is mandatory for numerical simulations involving such complex geometries and flow conditions to be validated with model tests results.
3.3. WP13 - Distributed Thrust
Highly loaded propulsors that deliver poor efficiency are a feature common in many ship types including inland waterways vessels, fast ships and tug boats. An emerging alternative to the large area propulsor concepts highlighted earlier is to distribute thrust over multiple propulsors arranged around the ship hull:
The objectives of this area of research were to:
● Develop new methodologies to better predict air suction - a major factor affecting the hull design and size of the propulsors - and in this way improve propulsion efficiency.
● Carry out CFD modelling to derive the optimal distribution of multiple thrusters around the hull.
● Validate the distributed thrust concept with its optimal propulsors configuration through model testing.
● Evaluate the efficiency gains measured against benchmarks
The findings of WP13 have been assessed by the comparison with the experimentally investigated benchmark ship and the fully developed distributed thrust concept:
● CFD optimisation of the bare hull reduced the resistance by 22%, which is more than the 16% predicted.
● The developed of the hull displaces 3% more water, which can be exploited by a higher payload.
● CFD codes from WP3 to predict ventilation of the propellers were applied and validated successfully in this WP.
● A required thrust reduction of 38% has been found. However, due to a poor efficiency of the applied rudder propellers and stock propellers this significant thrust reduction leads to a power reduction of only 7%.
With the knowledge achieved within STREAMLINE work packages and the foreground knowledge gained, it was deemed feasible to exploit more than the thus far determined 7% power reduction; in particular when taking into account that the thrust demand was reduced by 38%. Therefore, the optimisation of the used rudder propellers was decided upon.
With the optimisation of the rudder propellers, the open water efficiency of the rudder propellers was improved by 21.5%, consequently the final performance of the vessel was improved by approximately 25%, while providing an increased cargo carrying capacity of 3%.
3.4. WP21 - Advanced Screw Propeller Systems
A primary aim of the STREAMLINE project was to develop and evaluate innovative marine propulsion concepts to achieve significant alleviation of environmental impact as well as reduction of operational costs. Nevertheless, it has been shown that enhanced CFD modelling/design techniques represent a powerful means to pursue consistent improvements of standard screw-propellers efficiency, without incurring major modifications to the overall propulsion layout.
The aim of this work package has been to explore the potential of enhanced CFD-based modelling and design techniques to achieve a new generation of high-performance screw propeller systems, these included:
● Vortex Generator (VG)
● Pre-swirl Stators (PSS)
● Boundary Layer Alignment Device (BLAD)
The analysis of model test results has allowed STREAMLINE to draw the following main conclusions for each of the design modifications addressed:
Optimised hull aft body and integrated propeller (H2+P2)
Results demonstrate that a totally new hull aft body design obtained by advanced CFD tools can determine large improvements of hydrodynamic performance. In this case, modified hull lines have been designed to fit a larger diameter propeller while preserving hull displacement and tip clearance of the baseline design. Delivered power at full scale (PDs) has been increased by 8.7%, and the inflow to the propeller is more homogeneous with lower pressure pulses and vibratory loads with respect to the baseline.
Tip-raked propeller (P3)
A tip-raked propeller (P3) optimised for the original hull form has achieved an increased open water efficiency of more than 3%. Unfortunately, efficiency gain at advance ratio corresponding to ship cruise speed is marginal and hence no improvement of delivered power PDs is observed while design propeller RPM is reduced about 1%.
Twisted rudders and pre-swirl stators
Two optimised propeller/rudder layouts (R1LE and R2) based on the twisted-rudder concept determine a reduction of PDs of approximately 1%. Similar power gains are obtained by introducing a pre-swirl stator (PSS) with 3 fins on portside.
3.4.1. WP21 Advanced Screw Propeller systems
3.4.2. Operational analysis
The operational analysis review indicates that the simplicity of the modifications to improve hydrodynamic performance of the reference vessel would mean that very little change would occur to the vessel. This in turn makes all the different ‘Advanced Screw Propeller systems’ concepts practically feasible options due to their inherent passive functioning for both new building or retrofitting purposes.
3.4.3. Cost-benefit analysis
Cost benefit analysis indicates that among the different ‘Advanced Screw Propeller System’ concepts, the P2 Propeller option combined with hull modification (H2) is more economically viable, but can only be applied to new builds. Out of the remaining concepts, which are all indeed retro-fit options, twisted rudder R1 is more economically viable.
3.5. WP22 - High-Efficiency Waterjet at low speeds
Water jet systems have been used for propulsion of vessels in the whole speed range up to, and even beyond 55 knots, with main applications in the speed range 25-45 knots. For lower speeds than 25 knots the industry relies mostly on propulsion systems based on conventional propeller technology. The combined needs of reduced fuel consumption, lower emissions and increasing demand for high vessel speeds leads to the need for new conceptual designs handling dual design targets both at high and low speed.
It has been the aim of STREAMLINE to investigate the potential to design high efficiency waterjet systems based on variable inlet/outlet geometries using existing and new actuation technology.
A number of different concepts have been evaluated until a single concept which was promising and realistic was found and was then taken forward to final design. This concept had an auxiliary channel that could be either active or passive.
Model testing in a towing tank, cavitation tunnel tests, as well as CFD simulations have been carried out and the final design to evaluate the classification and operational aspects of the concept.
During initial model tests in the cavitation tunnel it was shown that significant improvements in low speed efficiency were displayed, however at high speed the performance has not been as intended with a reduction in efficiency compared to the baseline.
Using the towing tank facilities at SSPA, both towing tank and self-propulsion tests were carried out. The results showed a good collaboration with the results previously obtained in the cavitation tunnel at the higher speeds which meant that the baseline inlet performed better than the new design, both with the auxiliary channel opened and closed. During bollard pull testing, no differences were displayed between the inlets but this is likely a consequence of the towing tank tests being performed at atmospheric conditions where the pump and inlet cavitation does not block the pump in the same way as it would do in the reduced pressure in the cavitation tunnel.
The numerical simulations of the bare hull resistance and self-propulsion tests showed a good agreement with the cavitation tunnel and towing tank tests, but some deviations were found in the results. These deviations in the results may have been due to a short fall in the simulations.
The operational and cost benefit analysis showed that the performance increase at low speed did not compensate for the losses at high speed, and thus there is no incitement for an operator to invest in the design, this is due to the increased production cost not being recuperated through the reduced fuel consumption. Improvements to the concept have been identified that could potentially improve the performance of the inlet but this would be at an additional cost in the manufacturing process.
3.6. W23 - Advanced Pods
Pod units have been used for ship propulsion for more than a decade, but are still a ‘novel’ propulsive unit compared to the conventional propeller on a shaft. In order to be a real competitor to conventional propulsion, both the total vessel efficiency and the propulsive efficiency have to be increased.
One solution is to use the pod in a contra-rotating concept. Another is to put a pod unit behind a conventional main propeller (Contra-rotating Pod, CRP). A second more promising solution (from an efficiency point of view) is to design a ‘true’ contra-rotating pod unit having two propellers close together either pushing or pulling (Integrated Contra-rotating Pod, ICP).
Within STREAMLINE the hydrodynamic performance of propulsive systems, based on contra-rotating propellers and podded propellers, has been analysed through computational modelling. This computational analysis has been performed by means of the hybrid RANSE/BEM model developed by CNR-INSEAN. The methodology aims at combining the capability of RANSE to describe viscous flows around ship hulls and the capability of inviscid flow BEM models to predict reduced computational effort propeller forces. The Cavitation and ventilation behaviour of podded propulsors in service conditions has also been studied using a computational model developed by CNRS providing an improved knowledge on the interaction of cavitation and ventilation, the assessment of ventilation risks in the design phase has been improved.
Through computational modelling and scale model testing, the savings for the CRP and the ICP have been considerable, compared to the reference ship used. The predicted power for the CRP is 13.5% lower than the reference ship, and the corresponding figure for the ICP is 11%.
Due to these results, throughout the third period, the ICP and CRP concepts were further developed. The reduction in power consumption compared to the previous ICP was 1% and compared to the reference RoRo ship it is in the order of 12%.
The manoeuvre simulations for the CRP also showed that it is possible to control the ship in all weather conditions tested when running in normal conditions, i.e. both propellers running and pod used for steering. The conditions tested covered wind velocities up to 22.6 m/s mean wind and significant wave heights up to 5.6 m. With one propeller stopped, it was demonstrated that it is still possible to control the ship in weather conditions up to Bft8, only using the pod.
3.6.1. Operational Analysis
With a conventional propeller and pod working together, they offer an improved propulsive efficiency, enhanced manoeuvrability, redundancy and flexibility with respect to the changing operating conditions. Both CRP and ICP will be more expensive and complicated in installation and operation.
A single propulsion unit cannot offer the same level of redundancy as the combination of pod and propeller though the manoeuvrability and flexibility will be similar. In the short term, CRP is considered to be much more realistic and practicable, cost effective and more reliable than ICP. However, in the long term, ICP may become cost effective when it gains popularity and becomes part of mainstream technology.
3.6.2. Cost-Benefit Analysis
Cost benefit analysis considering a twin screw reference ship indicates that CRP is economically superior compared to that of the conventional propulsion system, whereas the ICP is economically inferior compared to that of the conventional propulsion system.
3.7. WP3 Advanced CFD Tools
The tools developed within STREAMLINE have been used throughout the project and have been an integral part in the development of the operational technologies. STREAMLINE has shown that CFD tools have the capability to be used as design tools within industry, with a reduction in computational effort and the operator skill level required.
With these new CFD capabilities designers are now able to search for the limits in propeller design. The tools developed within the project are being used today in commercial projects by the STREAMLINE partners.
The following codes were used throughout WP3:
FreSCo+
The finite-volume simulation procedure FreSCo+ has been enhanced to address the specific aspects of advanced propulsion units and their hydrodynamic interplay with the hull as well as (in)flow manipulating devices. Extensions implemented and applied refer to a conservative overset-grid-coupling technology for unstructured moving/deformable grids. The enhancements have been demonstrated to provide the required flexibility and predictive accuracy to investigate problems featuring complex dynamics, e.g. cycloidal/biomechanical propellers or propeller/rudder-interaction. Due to the complex relative motion and dynamics of advanced propulsion units working in behind conditions, the parallel efficiency suffers a from static parallel environment. Accordingly, attention has also been given to dynamic load balancing aspects to improve the speed-up of the implementation which is a major aspect of the industrial usability. Moreover, local grid refinement strategies and vortex supporting techniques have been included under the aegis of STREAMLINE. Grid-refinement criteria have been formulated in accord with an adjoint-based optimisation approach to secure that the actual simulation goal is supported by the grid-refinement process. All aspects have been harmonised with important existing features, e.g. RANS/BEM coupling, gradient-based optimisation, 6 DOF and seaway models etc.
ISIS-CFD
A research code to simulate fully unstructured viscous flows devoted to ship hydrodynamics has been developed. The main results have been the validation of the existing potential capabilities of the code though the various industrial cases proposed in various WP at both model and full scale. STREAMLINE has demonstrated the capability to compute very complex geometries with the propeller in waves through the sliding grid technique from a unique hexahedral unstructured grid and 6 D.o.F (Degrees of Freedom) resolution. This provides an optimum use of grid points and CPU with automatic grid refinement, with load balancing suitable for free-surface capturing, cavitation modelling and other physical based criteria. This has demonstrated a reduced CPU time from a simplified propeller model (BEM model, AD model) and quasi-static approach.
PRO-INS
A Boundary Element Method solver for the hydrodynamic analysis of marine propulsion systems has been developed. This solver includes general interfaces to be coupled with ship viscous-flow solvers operating in hybrid RANS/BEM mode, and with numerical optimisation models to perform shape optimisation studies. The solver can be applied to analyse various types of marine propulsors: fixed-pitch, variable-pitch propellers, ducted propellers, podded propellers.
Chi-Navis
A finite-volume viscous-flow solver based on RANS, DES, LES solutions of the unsteady Navier-Stokes equations. Solver features include: dynamic overlapping grids, level-set free surface model, library of turbulence models, 'body-force' propeller models, multi-body 6 DOF dynamics; multi-paradigm parallelisation. This provides very accurate viscous flow predictions, describing marine vehicles in arbitrary motions. Overlapping grids allow the building of high-quality computational grids at reduced effort; DES and LES allow the description of complex turbulent and vortical structures; propellers can be explicitly solved or modelled via hybrid RANSE/BEM scheme.
Kurgan
A hydroacoustic solver based on the numerical solution of the Ffowcs-Williams and Hawkings equations. This solver is based on a Boundary Element Method generalised to include volume integral contributions. The solver allows the analysis of propagation and scattering of hydrodynamic noise sources on marine vehicles including the effects of the propulsion system. The methodology provides a unique approach to detect broadband noise sources associated to flow turbulence and vortical structures. Interfaces with CFD solvers based on RANS and DES/LES have been developed.
HyPPO
A computational platform for general purpose numerical optimization problems. The platform includes a variety of computational schemes for single-objective or multi-objective optimization, robust optimization, and local as well as global search algorithms. This numerical optimisation platform is very general. Ship performance optimisation can be studied as a shape optimisation problem through new techniques. These numerical optimisation models can be easily interfaced with CFD solvers like "Chi-Navis" and "PRO-INS".
3.8. WP31 Development of Fixed-grid/Rotating-grid Coupling
The development of CFD tools to simulate the propulsor action behind a ship hull, and interaction of these objects. This work package was split into three CFD methods:
● Task 31.1 - Mesh coupling using a sliding grid approach (CNRS, MARIN)
● Task 31.2 - Mesh coupling using overlapping grids (TUHH, HSVA)
● Task 31.3 - Comparisons of various coupling strategies and error (CNRS, MARIN, HSVA, TUHH)
Sliding grid capability in ReFRESCO and ISIS-CFD has been developed. This will provide an extension to the existing software whereby it may be implemented as a design tool to provide a more accurate result in propeller modelling for propellers behind stationary ships or stators.
With the development and implementation of the overlap grid feature in FreSCO+, this provides the capability of simulating objects moving against each other in domains made of multiple grids.
3.9. WP 32 Grid Adaption
The work package covers the development in automatic grid adaption during the CFD computation to simulate flow details such air suction, cavitation, pressure fluctuations, erosion or the footprint of vortex generators, and the interaction of these conditions on different thrusters or propulsors.
STREAMLINE has demonstrated an improved grid refinement technology in ReFRESCO, Fresco+, ISIS-CFD, and OpenFOAM software, allowing for a higher grid resolution locally in highly transient flows, this will be effective for large scale parallel computations, and thus improved predictive capability
Compressible viscous flow code with cavitation modelling capability has been improved; this provides the most complete computational model of cavitating flow phenomena developed to date. It also allows for the study into the effect of vapour compressibility in the collapse of the cavity, and the acoustic effects on the near and far field.
3.10. WP33 Prediction of cavitation
The work package covers the development of state-of-the-art cavitation modelling, and the investigation of CFD methods to define a direct characterization of pressure fluctuations and its harmful consequences on marine propulsion systems in terms of erosion risk for propellers and rudders.
Cavitation modelling capability in ReFRESCO and ISIC-CFD has been developed, providing the ability to predict cavitation.
Propeller-induced pressure fluctuations and radiated noise have been investigated by the novel Ffowcs-Williams and Hawkings methodology implemented into the Kurgan code and by a Kirchhoff-Helmholtz methodology implemented into the Excalibur code.
The following software codes were used throughout WP33:
● ISIS-CFD
● ReFRESCO
● PRO-INS
● Chi-Navis
● Kurgan
● Excalibur
● OpenFOAM
3.11. WP34 RANS / BEM Coupled Method
The work package covers the development of efficient RANS / BEM coupling to provide a cost effective approach to investigating hull-propeller interaction and to predict self-propulsion conditions with sufficient accuracy.
A RANS-BEM coupling software code has been developed, providing fast computations of resistance and propulsion characteristics of hull-propeller combination. The implementation and improvement of the RANS / BEN interface has also been developed, providing an improved simulation procedure using the newly developed RANS-BEM coupling software code.
The following software codes were used throughout WP34:
● ISIS-CFD, Chi-Navis, Parnassos, FRESCO+ (RANSE)
● PRO-INS, QCM, PROCAL (BEM)
3.12. WP35 Design Optimisation
The work package covers the development and assessment of numerical optimisation techniques and automated design procedures, by the improvement of existing numerical optimisation tools. It also includes the revision and update of design procedures to increase the impact of simulation tools and technologies.
The software code for the optimisation of the strategy for ship-propeller interaction has been developed. This provided the optimisation of the aft bodies of ships, taking into account the propeller-hull interaction propellers.
The software code for ‘Free Form Deformation Technique’ has been developed. This provides an optimisation process that reduces the required use of licensed third party software, reducing the required user interaction.
PRO-INS and HyPPO codes were used throughout WP35.
Potential Impact:
5. Impact and Exploitation of Results
5.1. WP11 - Large Area Propeller
Through the research carried out within the STREMLINE project, Rolls-Royce is proposing to further develop the large area propeller technology in 2 parallel development projects. The results generated by the STREAMLINE developed methods and tools have been very important in the decision making process to exploit the Large Area Propeller technology beyond the STREAMLINE project.
The first project to exploit the technology is within the LEANShip consortia, where we aim at demonstrating the Large Area Propeller technology on a series vessel together with a European ship operator, yard and research organisation. The aim is to optimise the vessel and a large area propeller within the current design space with minor modifications required. With these constraints we expect to improve the propulsive efficiency up to 10%.
The second project to exploit the technology is through a UK funded Rolls-Royce led demonstrator. In this project we aim at fully exploit the potential of the large area propeller where we expect an improvement in propulsive efficiency of between 15-20% across several vessel types.
5.2. WP12 - Walvistaart Pod
Through the research carried out within STREAMLINE the project has demonstrated, with the use of CFD tools developed within the project, that the concept has the potential to provide the efficiency and power improvements envisaged over a conventional propeller system. The feasibility study conducted by MARIN showed that although the production and testing of a model was not achievable within STREAMLINE, it would be achievable as a future project.
Despite the advancements made within STREAMLINE, the Walvistaart Pod is still in the ‘concept’ phase. Therefore, there is still a requirement for further development of this technology, this will include:
● Analysis of the 2D, and 3D computations.
● Model scale testing must be completed to validate the CFD conclusions.
Once the concept has been developed the CFD computations have been validated and the system has displayed the results that are envisaged, it is planned that the WS group will:
● Complete financing of inland navigation ship.
● Find a producer for the POD.
● Order and build a vessel.
● Extensive test trials with a vessel.
● Continue to improve design in particular size and weight.
● Develop seagoing POD.
● Develop a smaller POD for Yacht industries.
5.3. WP13 - Distributed Thrust
The concept has shown good improvements beyond the SoA, with potential operational cost reductions of up to 10%, and potential fuel savings of up to 25%. STREAMLINE has demonstrated that the concept has applications within the European Maritime Market within inland shipping, with the potential to reduce road congestion and meet CO2 regulations and targets.
DST will be raising proposals in the first call of H2020 2014 within MG4.1 and MG4.4 for the further development of what has been achieved within the STREAMLINE project.
The STREAMLINE Benchmark Ship is being used within National German funded projects:
● Skate
● Wake
CNRS will use 2 Phase CFD Code in research projects to predict the air suction of the propulsion systems. The functionality of the code is now fully integrated into the commercial code licence, and can be used commercially.
ZF will be integrating the improved housing geometry for their rudder propeller designs. A project is now being derived to optimise the hydrodynamic performance of the azimuth thruster. Within this project, further development of the rudder propellers developed within STREAMLINE will be conducted with the aim to:
● Optimise the shape of the thruster.
● Improve the thruster body resistance and improve the wake field in the behind condition.
● Reduce running costs of the thruster.
● Improve the influence of the propeller on hull.
The research carried out and results obtained within the STREAMLINE project will be applied to the entire ZF thruster range.
5.4. WP21 - Advanced Screw Propeller Systems
With a combined optimisation of both the hull and propeller, the aim of increasing efficiency propulsive power reductions of by 8-9% have been displayed, with the potential of reducing operational cost and environmental impact.
The STREAMLINE Tanker Data set developed within STREAMLINE is at present being used within FP7 projects GRIP and SONIC. This is being used as a reference case, and therefore having a valued impact on present EC funded projects and their results.
The simulation based designs and optimisation tools developed for the hull propulsors are the subject of proposals being applied for within H2020, these include:
● Optimised Propeller;
● Twisted rudder, with combination of the ESDs within the to the propeller inflow.
Retrofit solutions with a combination of ESDs within the propeller inflow are also being addressed in H2020 projects for the application of optimised rudder and propeller configurations.
5.5. WP22 – Water jet at low speed
Following the results obtained within STREAMLINE, further analysis of the concept is required. The aim is therefore to expand of the scope of the design for the whole water jet system. The concept may be taken further and adapted for the ferry operations, from this further developments will be made in:
● The improvement of operations at low speed;
● An increase in power demand at high speed;
● An evaluation of total fuel consumption.
Experimental and numerical tools, verified through STREAMLINE, will be utilised for any future development and optimisation of the concept.
5.6. WP23 – Advanced Pods
Further development of the CRP and ICP concepts by SSPA will be dependent upon the market conditions; therefore SSPA may be bringing the CRP concept forward into H2020 proposals. At present the design of the CRP concept is being used by Rolls Royce in the design and build of a small vessel.
The ventilation experiments in a depressurised environment, conducted by MARIN have been:
● Used in demonstrations to large groups of customers
● Applied in several commercial projects (PODs and regular propellers)
● Applied in offshore industry (thruster ventilation)
5.7. WP31 – Development of Fixed Grid and Rotating Grid Coupling
Advancements within the development of the sliding interface and the overset-grid methodology have been significant.
These sliding interface techniques are being utilised within the following FP7 projects and joint industry projects, having a valued impact on present EC funded projects and the results there of:
● GRIP
● Refit2Save
● THRUST
The use of sliding interface techniques are being used for the development and design of Tidal Turbines by MARIN. This is being proposed within HORIZON 2020 project ‘RESTORE’, for the further development of this technology within the commercial sector.
The existing sliding interface technology implemented by ECN/CNRS in their in-house research flow solver ISIS-CFD was used and validated throughout the STREAMLINE project. It is available in the commercial version FINETM/Marine and mainly used in marine industry to take account for propeller effects.
5.8. WP32 – Grid Adaption
The Grid Adaptation techniques are being used within Commercial and Defence projects by MARIN. These techniques have now been developed further to include pressure fluctuations on the hull. They are also being used within the FP7 project SONIC to determine underwater radiated noise.
The Automatic Grid Refinement technique by ECN/CNRS in their in-house research flow solver ISIS-CFD was used and validated throughout the STREAMLINE project. It is available in the commercial version FINETM/Marine and used in the marine industry, mainly for sea transport, and also from naval architects for sailing boats.
5.9. WP33 - Prediction of Cavitation
The ventilation and erosion prediction solvers developed within STREAMLINE are being used to perform virtual experiments, and are being used in the decision making process at the design stage of new systems. These computational models developed are also being used at present within the assessment of innovative concepts for new projects.
5.10. WP34 - RANS/BEM Coupled Method
Hybrid solvers have now been shown to be suitable for application as software for industrial design, and are being used within new projects by CNR- INSEAN addressing the greening of marine transports as well as the development of marine current turbines. These tools are also being used by HSVA within Commercial, National and EU projects on a daily basis.
Since 2013 the RANS-BEM Coupled Method developed within STREAMLINE has been used within commercial projects by MARIN, as well as within the FP7 project GRIP.
MARIN will be utilising these design studies within H2020 projects and will use this methodology in the design on their propulsion systems.
5.11. WP35 – Design Optimisation
Tools developed within STREAMLINE are being used with National Projects by HSVA, and commercial projects by MARIN for both hull and duct techniques. MARIN have now extended these methods to include free-surface waves and will be utilising these techniques in future projects. The numerical optimization platform developed by CNR-INSEAN is currently used in commercial projects and will be proposed for R&D projects under H2020.
List of Websites:
www.streamline-project.eu
