Green Retrofitting through Improved Propulsion

Final Report Summary - GRIP (Green Retrofitting through Improved Propulsion)

Executive Summary:
The GRIP consortium set out to improve the general understanding of the working mechanisms of Energy Saving Devices (ESDs). Improved understanding would lead to better ESD designs resulting in a higher potential fuel saving for the world wide fleet. It was an objective of GRIP to reduce the fuel consumption of ships with ESDs on average by 5%, with reductions for individual ships up to 10%. For the demonstrator vessel, a handymax bulk carrier, a fuel saving of 6.8% over the speed range was demonstrated during dedicated speed trials. This fuel saving is well above the projected average fleet wide fuel saving.

With the Early Assessment Tool (EAT) a first estimate of the potential ESD fuel saving for a specific ship with given propeller details. With the EAT and the calculation of the potential fuel savings, we are able to better estimate the RoI upon retrofitting the vessel with an ESD. The EAT requires relatively little input and results in a quick and quite accurate first estimate of the fuel saving for the generic ESD type. The results should merely be used as a first judgement to continue the detailed design of the ESD. The EAT furthermore provides an estimate of the costs for installing the ESD. Detailed investigations into the working mechanisms of various ESDs such as; Propeller Boss Cup Fins (PBCF), Pre-Swirl Stators (PSS), hub-cup rudder bulb and rudder fins suitable for a large variety of vessels have led to a better understanding of these ESDs:

This better understanding can be utilised by the GRIP partners to further improve their ESD designs. Better ESD designs will make it more attractive for ship owners and operators to install an ESD on their vessel.

European ship yards will benefit from the re-engineering methods evaluated in the GRIP projects to determine the exact hull shape if no detailed drawings are available. With this exact hull shape, the ESD can be optimised. Using the anteSIM tool, retrofitting processes for European yards can be optimised to become more attractive to do the ESD retrofit.

As there are regulations on ESD design, from a structural point of view, the structural issues are often not studied in detail. Within GRIP the load variations, flutter, MIV, VIV and fatigue of ESDs have been studied and documented. Methods to evaluate the strength of both upstream and downstream ESDs have been developed.

For the demonstration vessel, dedicated speed trials have been performed by the GRIP consortium. As no of the partners have a direct benefit of the ESD over or under performing, these trial results may be regarded as an independent evaluation of the ESD performance. Furthermore the GRIP consortium have given insight in the reliability of speed trials for various conditions and methods to evaluate the ESD performance at full scale.

The GRIP partners have worked together very successfully to achieve high end independent results with great value for the European maritime industry. During the GST’15 conference in Copenhagen, the project results were presented to the wide maritime industry with over 45 attendants to the GRIP special session.

Project Context and Objectives:
The GRIP project has addressed the urgent need from industry for retrofitting ESD solutions for existing ships. The high demand for retrofitting is driven largely by four factors:
• the reduction of CO2 emissions,
• the historically high fuel prices,
• upcoming regulations and
• the lifetime extension of existing ships.

However, application of energy saving devices (ESD) is hampered by uncertainty over actual benefits, uncertainty over actual ship hull lines and the high cost of the actual retrofitting.

2.1. Drivers
2.1.1. Emissions
Within the Kyoto protocol, developed countries agreed to reduce their overall emissions of a basket of six greenhouse gases (GHG) by 5.2% below 1990 levels over the period 2008-2012, with differentiated, legally binding targets. The then 15 EU Member States adopted a collective target to reduce EU emissions by 8%. Under this ‘bubble’ arrangement the EU’s target is distributed between Member States to reflect their national circumstances, requirements for economic growth and scope for further emissions reductions. Each Member State has a legally binding target, with for instance the UK undertaking to reduce its emissions by 12.5%1. By 2050, a total reduction of 60% is aimed for.

shipping’s emissions is expected to rise to 12 to 18% in 2050. Therefore, much pressure is applied to the shipping industry to make its transport ‘greener’.
2.1.2. Regulations
The International Maritime Organisation (IMO) has defined a regulatory framework related to the energy efficiency of ships. This framework is based on two energy efficiency measures namely; the Energy Efficiency Design Index (EEDI) and the Ship Energy Efficiency Management Plan (SEEMP).
The basic principle of the EEDI (MEPC.1/Circ. 681) is to calculate an attained index for a new ship and to compare it to a required index. The overall attained index corresponds to the installed power divided by the ship speed and the amount of transported cargo. Reducing the ship speed is an obvious way to reduce the EEDI, but may be difficult to apply due to travel time constraints. Another possibility is to use an ‘innovative energy efficient technology’ which allows the main engine power to be reduced without reducing the design speed. The efficiency of such technology needs to be assessed by calculations and/or model tests and by measurements at sea. The SEEMP encourages the identification and implementation of ship specific measures to increase the ship energy efficiency (MEPC.1/Circ. 683). Among the suggested measures, the guidance on best practices set out in the SEEMP circular explicitly mentions ‘optimum propeller and propeller inflow considerations’, using ‘arrangements such as fins and/or nozzles’.
2.1.3. Fuel price
The price of fuel has varied over the last few years. However, looking back over the last 15 years, a clear trend is visible: the oil prices are increasing significantly despite the cyclic variations.
2.1.4. Lifetime extension
An effect of the current financial situation is the extension of the lifetime of ships. It is very difficult for ship owners to get financing for new ships. Most ship owners therefore opt for extending the lifetime of their fleet. Many of these ships were designed to last for 20 years with an expectation of replacement after this time. Although these ships were designed according to the state-of-the-art in the 1980s and 1990s, most are not considered state-of-the-art by current standards. Adaptation of the hull lines is not a feasible option, as this is the financial equivalent of building a new ship. Therefore, the only viable options for saving energy and money and reducing emissions is by replacing the engine, the propeller or by improving the efficiency of the propeller by changing the flow in the aft body using ESDs.

2.2. Uncertainties
2.2.1. Performance improvement
As discussed earlier, ESDs are appendages to the ship hull, the rudder or the propeller. These potentially improve the inflow and outflow of the propeller. ESDs are designed to prevent energy losses in the propulsion system or to recover some of these losses. Figure 2 shows an example of a pre-swirl stator which introduces rotation into the flow that counter balances the rotation induced by the propeller, thus recovering part of the energy loss. Another approach is to use Flow Improving Fins. Figure 3 shows an example of these fins in combination with a Vane Wheel. The fins align the flow and generate swirl where the Vane Wheel is intended to absorb and neutralise the rotation created by the propeller/fin combination. This configuration is intended to lead to more efficient propulsion, though generally at the cost of increased resistance.

A drawback of adding devices to the hull or rudder is that they also increase the frictional resistance of the ship. The real benefit of any propulsion improvement device can only be exploited once a sound trade-off between additional resistance and improved propulsive efficiency can be obtained. There are many devices which tackle the friction and hull/rudder interaction problems and are based on different energy recovery mechanisms.

It remained uncertain as to whether these devices actually improved the performance of the complete hull-propeller system, and if so why. Some devices showed great promise in model tests, but failed in full-scale validations. For other devices, manufacturers claim proof of large improvements on real-size ships, but these claims cannot be verified by independent
observers. Therefore, there is an urgent need for understanding the flow mechanisms involved in the potential energy saving of a device, both on model scale and on the actual ship scale.

2.2.2. Ship geometry
A perhaps unexpected uncertainty in retrofitting a ship with energy saving devices is the actual shape of the ship hull. The optimal energy saving device is very sensitive to the actual hull shape. Unfortunately, many ship owners do not know the accurate geometry of the ship hull. Ships change ownership quite often, diffusing existing information. Furthermore, many Far Eastern ship yards do not disclose the actual ship geometry to the ship owner, enforcing the ship owner to return to the original yard for fitting appendages. To make the ship owners independent of the original construction yard, methods are needed to determine the exact geometry of the ship.

2.2.3. Retrofitting process
Another obstacle for retrofitting ships is the costs of the investment. The actual costs of the energy saving device are rather modest compared to the profit lost due to downtime in the dock which is very large. In the previous century, ships docked every year for anti-fouling cleaning. Nowadays, ships are cleaned in harbour, and many ship owners dock their ships at intervals of up to 7 years. This implies that for retrofitting an additional docking period is needed, thus raising the costs for the retrofit considerably and often turning the balance for the return-on-investment (RoI). More efficient retrofitting processes are therefore needed but without endangering the accuracy of the retrofitted device.

GRIP aimed to provide a significant reduction in fuel consumption in shipping operations through retrofitting of ESDs to existing ships. On average, fuel consumption was to be reduced by 5% with reductions for individual ships of up to 10%. This in turn resulted in reduced exhaust gas emissions. Furthermore, the project planned to enable European ship yards to be competitive in retrofitting ships. Hence the project provided economic and environmental benefits. To achieve this, the following objectives identified:

• Objective 1: To provide ship owners with an assessment tool for quick decision making on retrofitting a ship.
• Objective 2: To allow ship owners to determine their ship’s hull lines independently from the original (usually Far Eastern) ship yard, to get the most optimal device from designers.
• Objective 3: To provide an optimised and numerically modelled retrofitting process for ship yards.
• Objective 4: To characterise the physical mechanisms behind the different available energy saving devices, as a basis for an advanced design procedure.
• Objective 5: To design new optimal energy saving devices for the ship types contributing most to the CO2 emissions from international shipping.
• Objective 6: To validate the predicted gains of designed ESD with full scale sea trials.

Project Results:
This chapter gives an overview of how the projects objectives were met and which results contributed to achieving the objectives.

3.1. Objective 1: Retrofit decision making tool
The objective to develop a retrofit decision making tool was met in GRIP WP1 by partners Wärtsilä, MARIN, Acciona, Fincantieri, HSVA, VICUS and Uljanik. A retrofit decision making tool is often used in an early stage of the assessment of the investment.

The goals of the retrofit decision making tool were to
• Define a framework of vessel types and ESDs and define reference cases
• Set up a database of reliable ESD performance data;
• Develop an early stage calculation tool for ESD benefit;
• Develop a model for estimation of ESD cost;
• Develop and implement Early Assessment Tools:
► A web-based tool for public use;
► A project member tool for more in-depth calculations in an early stage

A survey has been carried out to define the structure of the Early Assessment Tool (EAT) and to make a selection of the ESDs and vessel types that will be researched within GRIP.

An overview of both the fuel consumption per vessel type and their share within the world fleet has been made. Within the guidelines as described in the Description of Work, vessel types were selected to be researched within GRIP. Selected ship types are: container vessels, bulk carriers, tankers, ferries/ropax and short sea shipping cargo vessels. Those ships are the large fuel consumers within the merchant fleet, while the coaster type ships have a dominant share within European shipping traffic.

For the selection of Energy Saving Devices to be analysed within GRIP, a set of assessment criteria were defined. Based on these considerations three types/groups of ESDs were chosen;
• Pre-swirl stator
• Upstream duct
• Propeller Hub Slip Stream loss Recovery Devices (PBCF, hub cap rudder bulb, small stator fin)

A structure for the EAT has been created as shown in Figure 4. This tool will answer the question whether an ESD is viable as retrofit for a given vessel or not. Said assessment will include a Selection Tool, a Database, a Cost Model, a Hydro model and a Business Economic Tool. The Early Assessment Tool will consist of two versions; a web based tool (iEAT) for public use and a project member tool (EAT) for in depth calculations in an early stage.

In total, the database contains 130 review sheets. Some basic statistical analysis was performed on the data. The average Energy Saving Ratios and the standard deviations in the results have been calculated for each of the ESDs. Within the different datasets for the specific ESDs, also subdivisions based on the source of information (model test, full scale measurement, CFD, etc.) and the assigned quality level have been made. The results are shown in Figure 5.

For the power saving tool five different ESD’s were selected to be implemented. For each ESD a parametric model was created. The models do not consider specific ESD geometries, but are generalized for each type of ESD that is selected.

• Pre swirl stator: This model is parametrically scaled with the propeller diameter. The particulars from the lifting line code are used to calculate an adapted wake field and the reduction in required power.
• Pre ducts: As for the Pre swirl stator.
• Hub cap- rudder bulb: This model uses the thrust loading coefficient of the propeller to determine the change in required power.
• Propeller boss cap with fins: This model depends on the pitch unloading at the root of the propeller, so the pitch value at the root with respect to the maximum pitch.
• Small rudder fins: This model depends on the number of fins and the fin angle. Since the model should be a general ESD, the number of fins and fin angle are restricted to one value.
The models were validated using reference cases that are gathered by the different partners in this task. Validation from CFD calculations and model test results were used to validate the power reduction for the different ESDs. The results of the validation are satisfactory; only for the Pre swirl stator and the Pre duct some tuning was needed. Because the Benefit Tool only uses generalized models of the different ESDs and a limited number of ship particulars, the accuracy of the tool is limited. For this reason an uncertainty range is given for each ESD, depending on the reliability of the tool and the ESD itself. The uncertainty is between plus and minus 0.5% to plus and minus 2%, depending on the type of ESD.

A cost model has been set up, for estimation of costs involved when installing an ESD as retrofit. Cost types involved are engineering, manufacturing and installation. The cost model and its results are validated by real case examples.

Two versions of the Early Assessment Tool have been created: a web-based tool for public use and a project member tool for more in-depth calculations in an early stage. Target users of the public version are the technical staff of ship owners, consultants et cetera. This tool is meant to give guidance in a preliminary selection of ESDs.

Both the stand-alone and internet-based software tool have been completed. The stand-alone tool is provided with an installer. It is built on the Quaestor knowledge-based engineering framework, a tool developed and used by MARIN. The EAT contains a workflow around the ESD Database the Benefit tool and the Cost model.

The EAT enables the calculation of the Return on Investment (ROI) for a chosen ESD and a chosen ship type. Besides this final result, some intermediate goals can be computed: the power savings in the Benefit Tool or the costs in the Cost Tool.

In addition, the EAT facilitates access to the literature that has been used in building the models for the tool. The tool provides a search function for the database containing the publications.

The iEAT is the online version of the EAT. It is also a much lighter version regarding the calculations. It is built on the Quaestor knowledge-based engineering framework, a tool developed and used by MARIN. Quaestor is run on a Windows machine that is contacted by an Apache Server. Together, they provide the web-pages that represent the GUI of the iEAT. The iEAT makes it possible to calculate the Return on Investment for a chosen ESD and a chosen ship type. The iEAT is accessible at http:// http://www.grip-ieat.eu/. User name is ‘EATuser’ and password is ‘EAT*’. There are 2 web pages available to the user within the iEAT: one for input and one for output. A series of 8 ESDs are supported: hull fins/spoiler, pre swirl stator, pre duct, duct surrounding propeller, contra rotating devices, hub cap-rudder bulb, post swirl stator and combined systems.

3.2. Objective 2: Hull re-engineering
The objective to develop techniques to determine the actual ship geometry was met in GRIP WP 4 by partners CMT, IMAWIS, Fincantieri, Acciona and Uljanik. Concepts and technologies for the detection and collection of digital geometric information have been developed, which are necessary for the retrofitting process.

The approach executed to perform the reverse engineering of hull structure was distributed as:
i. Defining the reverse engineering state of the art
ii. Analysing and benchmarking of the reverse engineering technologies
iii. Concept for measurement of data model generation
iv. Performing measurement and validating the reverse engineering technology

The technologies that were considered for performing the reverse engineering measurement and re-engineering of the hull structure are shown in Figure 6.

After defining the reverse engineering technologies, the benchmarking of relevant application cases, according to the identified criteria, was done.

At the selection of the suitable measurement systems it was shown that Photogrammetry and Photo-modelling were suitable technologies to measure the possible application cases. Photogrammetric systems with a high mobility can be used for complex structures and where a high accuracy is needed. Photo modelling are primary applicable for the fast capture of complex geometries with a relatively low requirements concerning the accuracy of measurements.

The results of the selection of suitable measurement systems are shown in Figure 7 for two application cases. The criteria will be evaluated for each measurement technology or GRIP object by using 3 levels: Low, Medium and High.
The laser scanner was chosen as a third measurement technology to use during the GRIP project. With this system a fast and easy recording of the ESD is possible with a high accuracy. After the selection of the suitable reverse engineering technology to be validated in the GRIP project, a concept for the data preparation and transfer during the full scale demonstration. The recommendations provided by the partners were incorporated in order to grant a smooth a process as possible.

The laser scanner was chosen as a reverse engineering technology to be used during the full scale demo. The laser scanner was validated on its measurement and model generation during the assembly of the Pre-Swirl Stator Fins at Rijeka, Croatia. After the installation of the ESD on the vessel a 3D laser scanner was used in dry dock to digitise the hull shape, exact location of the stator and final stator geometry on the vessel. Figure 9 shows the scanner in operation in the dry dock. A number of positions were taken from where the laser scanned the ship and stator. Using reference points the scans could be combined to provide a complete 3D point cloud of the propeller, stator and hull. These Point Cloud models were then used in conjunction with the 3D CAD design drawings to compare the dimensional accuracy of the Stator Fin assembly.

Figure 10 shows a comparison of the measured shape of the ESD with the design. This shows that the fins were installed too far ahead (orange and yellow) and have a slightly different pitch (blue). Different cross sections were made to get a detailed list of deviations of the installed fins with the design. The final geometric shape and location of the ESD on the vessel was determined and used in the final CFD calculations for the prediction of fuel saving potentials of the ESD. It was concluded that 3D laser scanning technique is ideally suited to the evaluation of the final assembly of ESDs after installation.

The results of the laser scanner were used in WP 5 and WP 6 to validate the design and compare the calculations with the performance measurements of the vessel.

Partners in GRIP have compared state of the art methods and applied the most optimal to a demonstration case. The GRIP project has progressed the state of the art by a thorough documentation of the comparison of various methods to re-engineering methods.

3.3. Objective 3: Optimised retrofitting process
The objectives were to develop techniques to optimise the ship yard retrofitting process by better planning with the aid of simulation studies. The following solutions have been developed:
• Retrofit concept based on efficient manufacturing/assembly processes as well as the preparation processes such as planning and control; and
• Tools which will support the shipyard and owner in the planning phase of the retrofitting process as well as in the execution.
In order to perform the implementation of advanced planning techniques of a retrofitting process using simulation, the tasks carried out in the project were as follows
i. Define the list of planning processes involved while performing a retrofitting order
ii. Develop a simulation concept for the implementation of advanced planning in shipyards
iii. Develop and/or adapt simulation tools to perform retrofitting activities
iv. Validate the developed concept, simulation tools and simulation model

Business Process Models were developed, representing the administration and planning stages of a retrofitting order. The technical processes involved in retrofitting ESD in a ship were also incorporated in the business process model. The administrative business process
model was modelled with the principle of classifying the process into four stages. They are Contract Negotiation Phase, Order Planning Phase, Production Process Planning Phase and Production Process Execution Phase. For each stage, a dedicated process model was developed providing details on the activities to be performed, personnel required, resources required and information. An example is given in Figure 11.
With the business process model, the possible areas of application of simulation tools, in order to aid and improve the planning process was discussed and defined along with the project partners. Table 1 shows the list of tasks which were listed as possible improvement in the planning wherein simulation can be used.

The Simulation Toolkit Shipbuilding (STS_Toolset) was utilised in the development of the simulation models which would be used in the project. During the development of the simulation models some adaptations and modifications were required for some of the existing toolsets, so as to be utilised for the required purpose of simulating the retrofitting activity in GRIP. Listed in Table 2, are simulation tools that were utilised, adapted and/or modified during the implementing simulation of retrofitting activities.
Considering the versatility in operating styles, sizes and business strategies of different types of shipyards, there was a request from the shipyard partners in the project to provide a solution wherein the need for a simulation expert to perform simulation studies is minimal.

Based on the feedback and also on the experience CMT had gained from other projects such as RETROFIT, a Two Stage Simulation Concept was developed consisting of a first stage using anteSIM and a second stage using detailed simulation with Plan Simulation.

In the first stage of the study the simulation will be executed in anteSIM, a software tool based on a java platform. In the second stage of the study the simulation was executed with a combination of anteSIM and Tecnomatix Plant Simulation. The differentiation between the two stages lies in the level of detail of the data input and output that can be obtained at the end of the simulation. In order to realise the two stage concept, CMT developed the planning tool anteSIM.

The three main components, also shown in Figure 13 including the interaction, that are involved in the execution of the two different stages of the simulation concept are:
• anteSIM – Planning Tool
• Simulation Database
• Plant Simulation

AnteSIM is a software tool that initially was developed in the java platform in cooperation with SimoFIT. SimoFIT is a cooperation work in performing outfitting simulation studies in the maritime and civil industry.

The Simulation Database has been utilised to save all the information that would be required and provided in the anteSIM for performing simulation studies. The simulation database has been used as a platform to develop the libraries for process patterns, resources, product structure, etc. Development and populating such information in the libraries of the simulation database would aid in fast accessing of the information required for simulation and thereby performing the simulation studies as fast as possible.

Plant Simulation is a discrete event simulation software developed by Siemens – Tecnomatix. To incorporate the software in the shipbuilding industry, Center of Maritime Technologies (CMT), Flensburger Schiffbau GmbH & Co. KG (FSG) and other partners founded the Simulation Cooperation in the Maritime Industries (SimCoMar) which is dedicated to continuously developing the simulation toolset STS (Simulation Toolkit for Shipbuilders). STS helps planners in the shipyards to configure, simulate and to the highest possibility represent the activities and resources of a typical shipyard. In the simulation concept explained in Figure 12, the Plant Simulation software would be utilised only in the second stage model of the simulation concept. Figure 14 shows the simulation model which was utilised in the GRIP project to perform simulation studies on the Pre-Swirl Stator Fins assembled at VIKTOR LENAC, Croatia.

In order to validate the developed tools and simulation concept, the flow of activities, resources required, constraints in execution of activities, positional information and other required details were collected during the assembly process of the Pre-Swirl Stator Fins at VIKTOR LENAC shipyard. The information from the assembly process was used to perform 30 simulation runs to find an optimal flow of processes and thereby optimal planning of resources for the Pre-Swirl Stator fins assembly. Scenarios were developed by changing the available resources for the retrofitting orders. The lead time of the retrofitting order and the utilisation rates of all the resources utilised in the pre-swirl stator fin assembly was analysed. A detailed description of the scenarios, simulation study and its results are explained in deliverable D6.4.

State of the art methods have been applied to optimise the retrofitting process. Application of these methods have resulted in an advice to WP 6 partners responsible for the retrofitting procedure. GRIP has progressed beyond the state of the art by applying such methods to an ESD retrofitting procedure. This further improves the confidence in such systems for yard optimisation.

3.4. Objective 4: Characterise physical mechanisms
To better understand the physical mechanisms of various types of Energy Saving Devices from numerical analysis, one needs to know the applicability and reliability of the distinct numerical models one could use for the analysis of the flow. For the design problem however, different tools will have to be used, as a full and reliable analysis is often too time consuming and requiring details that are not yet available. Consequently, the main objectives in WP2 were to identify the governing physical mechanisms, to determine the applicability and uncertainty of different numerical models and then to choose or simplify the numerical models for the design process and demonstrate its effectively.

The approach followed to find the phyiscal mechanisms and acceptable models to represent these mechanisms through the design and analysis phase features three stages: A literature review, a computational uncertainty exploration, including the capability of the numerical models to represent the governing mechanisms, and finally the more design oriented tasks such as geometry generation and an evaluation of different design approaches.

Prior to the start of the GRIP project, there was no convincing literature explaining clearly the mechanisms for the different types of Energy Saving Devices (EDSs). Task 2.1 (Definition of improved approach for ESD analysis and design) and Task 2.2 (Numerical Uncertainty) contributed considerably to our current understanding of these mechanisms, by analyzing the flow and energy losses behind a ship, followed by the search for numerical models to capture these. To this end, Pre-Ducts, PreSwirl Stators and Rudder bulbs were numerically analysed. In addition, a propeller in an inclined flow without hull was analysed to study the ability of Boundary Element Methods (BEM) and RANS codes of capturing the effects of an inclined flow (flow with essentially a uniform axial flow component and a fluctuating tangential flow or swirl component). It was concluded here that BEM codes predict a significantly smaller effect of swirl than RANS codes. From an analysis of a rudder bulb system with a RANS-BEM model, it was concluded that the effect of the rudder bulb was probably not completely included in the BEM model, possibly leading to an under prediction of the effect on torque.

The hypothesis that the effect of Pre-Ducts can largely be attributed to an acceleration of the flow through the propeller disk, similar to the duct of a shrouded propeller, was tested on an axisymmetric body using a RANS-RANS model for the hull-propeller modelling. It occurred from this study that the acceleration effect on the propulsive efficiency is negligible. Hence it was concluded that asymmetry in the flow field is needed to make the PreDuct improve the efficiency.

Using the insight on working mechanisms and the limitations of the different computational models for the hull-propeller-ESD configuration, an evaluation of ESD design procedures was made in Task 2.4. Noticeable examples of exploratory work on design methods are the design of a PreDuct (see Figure 15) and the design of a rudder bulb (Figure 17).

It was concluded from the pilot study on design methods using RANS-RANS with Frozen rotor, that this might be a promising model for the design work. However, in WP5, where various design studies were made, it was concluded that the Frozen rotor model does not yield reliable values and even design trends may be wrong. As a consequence this model was discarded later.
An adjoint solver was used in the design of a rudder bulb to find the way one would want to pursue. Using this gradient search method one can find the sensitivity for changes in the hull-rudder geometry. Figure 17 shows an example indicating the sensitivity for minimization of the total resistance.
For the design problem to be solved, it was noted that important constraints related to the matching of propeller and engine, limit the optimisation. The application of an ESD usually changes the propeller characteristics and the required thrust by the hull. This means that the original propeller is not likely to be the most efficient propeller any more, or that the engine gets overloaded. To make a fair comparison of the benefit of the ESD, the propeller should again require the same engine loading in terms of torque-rotation rate relation as the original propeller. This implies that the engine can then be loaded in a different working point (Q,n), but should follow the same Q-n line. The constraints imposed by the need that propeller and engine match their loads, leads to four design scenario’s or cases.

It appeared from a case study on the design of a PreSwirl Stator that the constrained design cases 1 and 2, where the original propeller was used, power savings of around 3% could be attained. The two design cases 3 and 4 where a new propeller design was made, could result in power savings of around 7%.

The main problem for an engineer to design an ESD is to evaluate loads applied on the structure in sailing conditions. In general, CFD computations on this type of structure are performed in a steady flow and calm water. But in reality, the ship motions on waves change the flow direction and this variation should be taken into account to estimate loads.

In order to consider the seakeeping behaviour of the ship, the procedure, developed and tested during the GRIP project, is the following:
1) Perform CFD computations in steady flow to optimize design and power gain estimation,
2) Apply a methodology to evaluate maximal forces applied on the ESD in navigation conditions and to define a Design Wave leading to these forces,
3) Perform a second CFD computation using the Design Wave defined in step 2,
4) Carry out a structural analysis with Finite Element using forces determined in stage 2 or pressure distribution provided by CFD computations in stage 3.
This is also shown in Figure 19.

The first stage of the above procedure is to perform CFD computations in steady flow following recommendations and requirements described in objective 5.

The second stage used a methodology developed by Bureau Veritas and VICUS to define the design wave leading to the maximum forces applied on an ESD. This methodology is based on the study of the local flow incidence variation and the estimation of the inertia loads on the ESD. The global workflow of this methodology is presented in Figure 20. The goal of this method is to define the design wave to perform CFD computations in considering the worst realistic sea state for ESD structure. The first step of this methodology consists in hydrodynamic computations of the ship hull for a specified velocity, using potential codes. For this first step, hull ship meshing, ship velocity and draught depending on the loading case are required. The outputs of this first analysis are Response Amplitude Operators (RAO) of fluid velocities calculated for all ship motions and for all wave headings. The second step is a long term spectral analysis over the ship life and using a wave scatter diagram. The output is the definition of an Equivalent Design Wave for the target RAO defined in step 1. The third step transforms spectral analysis into time domain to calculate the non-linear ship response in time domain on the Equivalent Design Wave. The output is an Irregular Design Wave (IDW) that will be used for CFD analysis. Moreover, from lift and drag coefficients, we are able to compute lift and drag forces in post-processing. In the fourth step, the Finite Element Model (FEM) of the ESD structure is loaded by pressure distributions provided by CFD computation, using an interface specifically developed in GRIP for this application. Following this methodology, the designer will have an estimation of loads applied on its structure in two stages, the first one, global lift and drag forces, to define a preliminary design, the second one, pressure distributions, to validate the final design.

In the third stage, a new CFD computation is performed with the Equivalent Design Wave provided by the previous stage. The objective of this stage is to simulate a CFD computation with the sea state leading to maximal forces applied on the ESD.

At the end, two solutions exist to assess the ESD structure using the Finite Element method (see two examples of FEM in Figure 21). The first one uses the maximal forces determined at stage 2. This approach is adapted to validate a preliminary design. The second solution is to load a Finite Element Model of the ESD with pressures provided by CFD computation at stage 3. In addition, the fatigue assessment, based on the static analysis and cyclic loads estimated by the strength assessment methodology, is to be conducted to ensure that the ESD connection to the hull will not fail during the life of the vessel.

Hydro/structure coupling leads to a modification of the mechanical properties by changing the natural frequencies and damping of the structure. Vibration induced by fluid flow can be classified by the nature of the fluid-structure interaction. In steady flow, the mutual interaction between fluid and structure leading to increasingly large vibration amplitudes is the most commonly observed scenario. In unsteady flow, turbulence forces are the dominant source of structural vibration excitation.

For these reasons, three types of vibration due to fluid/structure interaction are to be investigated (see Figure 22):
• Motion Induced Vibration (MIV) also called flutter
• Vortex Induced Vibration (VIV)
• Turbulence Induced Vibration(TIV)

MIV or flutter is a dynamic instability, where the coupling of hydrodynamic forces with structure's natural modes of vibration (bending + twisting) produces rapid periodic motion of increasing amplitudes, which can lead to the collapse of the structure. The negative hydrodynamic damping exceeds then the structural damping. The classical flutter phenomenon is a 2 degrees of freedom phenomenon. In the framework of GRIP project, Bureau Veritas has developed software able to compute the natural frequencies of the structure depending on fluid velocities and the associated damping. A quasi-static solving allows to plot corresponding curves and to determine the fluid velocity of the coupling modes and then the possibility of flutter appearance.

Turbulence and Vortex shedding are viscous hydrodynamic phenomena that can occur when a fluid flows around a structure. They may generate unsteady hydrodynamic excitation forces leading to vibration of the structure. The simulation of these phenomena is difficult however an analytical method can be used to estimate the frequency range in which VIV and TIV are likely to appear and compared with numerical results.

At the start of the GRIP project, no methods to evaluate the strength issues related to ESDs existed. The GRIP partners have successfully demonstrated a method to evaluate the forces on ESDs and evaluate the strength and fatigue. This is a considerable step beyond the state of the art.

3.5. Objective 5: Design optimal Energy Saving Devices
In GRIP project, the actual design and optimisation of Energy Saving Devices (ESDs) have been performed for several ship types, which contribute most to the fuel consumption of the world fleet. Examples demonstrating new ideas of ESDs are the asymmetric rudder bulb designed for a bulk carrier and the “BSD” - a pre-duct for a tanker respectively, see Figure 14 . Also the more “established” ESDs have been intensively investigated, such as Propeller Boss Cup Fins (PBCF), Pre-Swirl Stators (PSS), hub-cup rudder bulb and rudder fins suitable for a large variety of vessels.

Probably the most important results obtained are the ESDs designed for the full scale validation vessel. The selected validation vessel by GRIP consortium is a newly built handymax bulk carrier named “VALOVINE”, built at GRIP partner Uljanik shipyard.

Since only one ESD design could have been realised and tested in full scale, as a unique opportunity for the CFD partners – MARIN, HSVA and VICUS – decided to participate in this design competition to design an ESD for this ship.

Since the schedule for this ship was very tight and the deadline for the hydrodynamic design needed to be set earlier than originally planned, the actual design period was less than 3 weeks. The designs made by different partners (see Figure 24) needed to be evaluated and only one design would be selected for manufacturing. To evaluate the ESD hydrodynamic designs, cross-checks were performed by all partners to minimise the influence of modelling and numerical errors by different computations and codes on the ranking of the ESDs. For the ESD selection, the hydrodynamic performance of the ESD is the most, but not the only important factor. Other aspects, such as cavitation risk, structural, manufacture and installation aspects, needed to be considered. Therefore, a rather complex evaluation matrix was established and a face to face meeting with all experts involved was organized for the final ESD selection.

It became apparent that the PSS designed by HSVA has showed the best performance and passed the cavitation risk, structural and final assembly checks; it was therefore selected by the GRIP Consortium as the ESD for the full scale validation trails. The design of the PSS and its evaluation has been conducted directly in full scale by HSVA, more details can be found in D5.1.

After selection of the ESD, the study on manufacturing feasibility was started. Due to the tight time schedule, this study has been more or less conducted in parallel to the construction plan phase. During this period, it became apparent that the PSS had to be shifted 30 cm forward due to some installation restrictions. This was a design change at a very late stage, and no time was left to repeat the ESD optimisation for the new position. Changing the installation position of an ESD would mean that the ESD would work under completely different condition than originally designed for. Using the paramatric model of ESD developed in the earlier project phase (Task 2.3: Geometrical prarmatisation and grid defornation), this change could be quickly implemented through shifting only the root sections of the PSS forward whilst keeping the high radius region the original position. This modification of introducing some rake to the PSS has the advantage that a new optimisation of the PSS would not be necessary since the high raduis region of PSS encounters roughly the same inflow as before so that the performance of the PSS should remain almost the same. A later check through RANS analysis confirmed this assumption showing that the ESD performance had hardly changed. With the manufacturing constraints analysed in the feasibility assessment, the final design was successfully produced and assembled giving credit to the close and good collaberation of different invovled partners.

Up to this point, it was not yet clear whether the ESD designed for the design condition/draft would give any benefit under the trial condition/heavy ballast draft during the sea trials. Further evaluation on the ESD performance under different opererational conditions including the trial condition has been conducted. Figure 25 shows the performance predicitons at different conditions, where the highest power gain has been observed for the design condition as expected. The power saving ratio for both off-design conditions are 1% off, but the margin (more than 4%) seems to be still large enough to be observed at trials. The operational profile for this ship has been estimated according to the available information and best knowledge. Together with the wind and wave statistics, the PSS life cycle aspects and long term prediction on fuel consumption behaviours have been derived, which results in an economic savings of 138 k€/year when weather effect, operational profile and load conditions are considered. This corresponds to a relative annual saving of 4.47%. Assuming that the PSS installed on a ship costs about 80 k€, the return of investment is accomplished in less than a year, namely 7 months in this case.

A similar analysis has also been performed for a PBCF installed on a container vessel from Fincantieri shipyard. An even higher economic saving of 172 k€/year has been obtained for this vessel. The return of investment is even shorter, being about 5 months in this case. In general, the interest of the installation of a certain ESD will increase as the share of energy used in propulsion, or the sailing share vs. port time increases.

State of the art numerical methods have been applied to the design cases, with special attention to the full scale validation vessel. Direct comparison between various methods and approaches is a step beyond the state of the art and valuable in the further development of numerical methods.
3.6. Objective 6: Validation of optimised ESD
In order to validate the fuel saving predictions of an ESD, full scale data must be collected of the actual device build and mounted to a vessel. During the GRIP project the validation of the CFD calculations and energy saving predictions were made by means of dedicated speed/power trials on a handymax bulk carrier build by Uljanik Shipyard. This vessel, the MV Valovine, was tested twice; once before the installation of the PSS, and once direct after installation in similar environmental conditions.

Apart from power savings, measurement equipment was developed to gain more in-depth insight in the working principles of the device by measuring change in flow field into the propeller plane as a consequence of the ESD.

In order to evaluate the fuel saving properties of the ESD speed/power trials were planned following ITTC guidelines. To determine whether speed/power trials are capable of providing sufficient accuracy to identify the 4-5% power saving predicted from CFD calculations, a sensitivity study was made. This identified instrumentation requirements and restrictions regarding environmental conditions during the trails. Moreover, it identified whether the comparison should be made on a single vessel, (before & after installation of the ESD), whether sister ships could be used or that the ESD could be installed during a regular dry docking of an existing vessel.

When comparing sister ships, the uncertainty in performance from variations in the build of the vessels, measurement uncertainties and uncertainties in the correction of trial results to benchmark conditions apply. The uncertainty of such data is difficult to determine; based on the measured performance of a number of sister vessels, it is not possible to identify the magnitude of each factor individually. Yet, analysis of trial results of six sister vessels identified that the comparison of an ESD on sister ships cannot give the required accuracy in the order of 1% or better. The combined uncertainty from the aforementioned parameters is too large; if changes in performance are to be identified with some confidence, performance improvements should be measured in the order of 10% to be confident that the effect of the ESD sec is in the order of 5%. Only when trials are done on the same vessel, the uncertainties from build tolerances and the systematic bias error of the torque sensor can be avoided. The separation of the effects of hull cleaning and conservation (during a regular dry dock) and the effects of the installed ESD are hereby important. The inability to quantify fouling and its effects on performance makes the evaluation of an ESD using trials before and after a regular scheduled dry dock meaningless. It is concluded that ESD evaluation trials should be made using trials whereby the ESD installed during a dedicated dry dock where the propeller and hull remains untouched.

To compare two trials executed in non-ideal environmental conditions, corrections must be made to account for difference in wind, waves, and differences in displacement. These corrections come with an uncertainty. The uncertainty in performance from measurement errors was determined using a sensitivity analysis. A sensitivity study was made for a bulk carrier to identify the consequences of measurement errors in wind speed, wave height, draft, shaft torque and ship speed. Case studies were made for different trial speeds and sea conditions. This analysis showed that when two trials are done on a vessel in sea state 3, the uncertainty in power between the trials becomes 2%. In other words; in order to identify power savings due to e.g. an ESD on a vessel, trials should be done in environmental conditions better than sea state 3. At sea state 2 (BF3) the uncertainty reduces to 1%. In collaboration with Uljanik it was therefore decided to perform trials on the MV Valovine (yard number 491), a handymax size bulk carrier, and to install the ESD on a separate dry docking a few days later. On April 5th 2014, the first speed trials took place in the Adriatic Sea, in the vicinity of Rijeka, Croatia

Directly after the first speed trials the vessel went in dry dock at Uljanik Viktor Lenac Shipyard in Rijeka. Here the ESD was installed.

Trials were done under fair weather conditions; wind around 1.6m/s with waves of approx. 12cm. As a result the corrections for wind and waves were small and consequently the uncertainty from measurement errors small.

A power reduction of 6.8% was determined as a result of the installation of the ESD. Due to a higher propeller loading a slight reduction in propeller RPM to reach the same ship speed was determined of 3.2%. The uncertainty in power was estimated as +/- 1% due measurement errors in speed, power, draft, wind and waves.

The trials are seen as a unique trial evaluation with exceptionally low uncertainty. Dedicated dry dockings where only an ESD is installed are rarely done in practice due to the high costs and requirement of off-hire of the vessel. Furthermore, the exceptionally fair weather conditions in the Adriatic sea and the use of the same instrumentation and trial team for both trials resulted in highly reliable performance data. These results form a clear proof that pre-swirl stator fins can indeed result in large fuel savings.

Once the PSS has been installed during a dry dock period of one week, the 3D as-built geometry has been measured by the project partner IMAWIS using the laser scan technique. A comparison between the measured in-situ geometry and the original geometry used in CFD, shown in Figure 27, discloses some difference in longitudinal position, twist and thickness of the fins, whilst the angular positions of the fins have been kept very well. Furthermore some difference in the ship stern region has also been detected. This makes it almost impossible to compare the results from the original CFD model with the validation trial results. Therefore HSVA decided to repeat the RANS performance evaluation of ESD under trial condition using the measured 3D as-built geometry. A new CAD model has been generated using the cloud points from the laser scan measurement. Subsequently, full scale numerical mesh has been generated based on the in-situ geometry, which reflects the increased thickness of the PSS blade around the root sections and the blunt tip etc., as shown in Figure 26. Figure 26 also reveals the challenges during the installation since the space between middle and lower fin is extreme marginal.

Figure 27 shows the full scale CFD power prediction for the whole speed range. As can be seen, the trends have been predicted very well for both cases without and with the PSS. However there is some discrepancy in term of the absolute power between trial and CFD. Also the power saving effect of ESD is under-predicted by CFD. Though the reasons are not quite clear, there are certain defects in the numerical models of CFD, which are not reflecting the reality. One of these models has been considered, the propeller blade roughness model, which has led to an improvement of CFD power saving prediction by 1% due to PSS in this case. Also, the power saving effect by PSS is predicted about 5.3% on average by CFD and 6.8% measured at sea trials. The gap between CFD and trial in the absolute power has been reduced to a large extent, now below 8% all over the speed range, as shown in Figure 27. Further the CFD results have confirmed the reduction of the strength of propeller hub vortex due to the presence of the PSS as also observed in the sea trials using high speed camera, see Figure 28 for streamlines passing through the hub region together with the pressure distribution on the stern and rudder. Figure 29 shows a still of the propeller with tip and hub vortex cavitation during the speed trial in ballast conditions. Figure 30 shows the same propeller under similar conditions but with the ESD installed. In this case no cavitating hub vortex was observed, which confirms CFD predictions. Both figures show good comparison in results between full scale and CFD.

Perhaps the greatest advantage of CFD over model tests, besides providing an unprecedented insight in the flow, was the ability to simulate a ship directly at full scale. However, in practice ESDs are often model-tested and ranked under model tests conditions which might be misleading if an ESD is suffering a strong scale effect. In general, it can be said that all ESDs suffer scale effects, since they are installed in the vicinity of the hull, propeller or rudder and operating more or less in the region of boundary layer, which is very much dependent on the Reynolds number. Consequently, such ESD designs performed in model scale have to be normally adapted to full scale applications in the practice. The scale effects of different ESD types have been investigated in GRIP project by different partners. The influences of the scale effects are however found multi-folded. The results indicate that the pre-stream devices which are installed in the vicinity of ship stern before the propeller see both positive and negative effects in model scale. The positive side is that the invoked additional resistance (or the thrust requirement increase) due to the ESD is somewhat smaller in model scale due to the fact that the ESD is operating in a thicker boundary layer and the interaction between ESD and hull is smaller in this case. The negative side due to the actually same reason is that the functioning (e.g. pre-swirl) effect of the ESD becomes also smaller in model scale which can be observed as a smaller increase of the propeller efficiency. With the cancelling-out of both sides, it is therefore hard to say whether a pre-stream ESD is performing better or worse in model or full scale. What can however be concluded is that the working points of an ESD have been shifted or changed in model scale comparing to full scale operation, so that it is recommended that the ESD should be designed or adapted in full scale whenever possible.

To further evaluate the changes in flow field predicted from CFD a flow measurement device was developed to be used during sea trials. The success of such a device depends, amongst others, on practical issues: it should be possible to install the device from the ship during a single dry dock. Removal of the device should not require divers or dockings. This means that no systems underneath the waterline can be installed. Any systems installed inside the ship must be small enough to fit between the frames and stiffeners onboard (spacing approx. 600x600mm). Furthermore, the system should be capable of measuring the flow up to a few meters away from the hull in a highly unsteady environment. The system should be capable to withstand strong vibrations, salt water and be portable enough to be transported through man-holes in the double bottom tanks. At the moment of writing there are no off-the-shelve systems available which comply with these requirements. However, within the EU project EFFORT (2002-2005) MARIN developed a Laser Doppler Velocimetry device specifically for flow measurements onboard ships. This system was however not operational and required several repairs and system replacements. During the GRIP project these repairs were made and important components replaced. Successful flow measurements were made with the system under laboratory conditions. The performance of LDV systems is however strongly dependent on water turbidity and robustness to withstand the strong vibrations of the hull plating directly above the cavitating propeller. Due to a number of causes outside the influence of the GRIP project, the available time for in-situ tests with the LDV system onboard (Figure 33) was limited. As a result of the time pressure during the measurement campaign and limited trouble shooting possibilities no successful measurement results could be obtained. However, the system will be further validated and improved by MARIN over the coming years to allow flow measurements on ships in the near future. GRIP is the first project delivering well documented and independent full scale evaluation of the performance improvements of an ESD. Methods have been well documented including the uncertainty of the measurements. This is an incredible step beyond the state of the art and valuable for the maritime industry.

Furthermore, the GRIP consortium have made progress in full scale measurements of the flow in the vicinity of the propeller. Unfortunately the objective to measure the flow was not fully met, however significant steps have been made with which the measurement of the flow is a small step away.

Potential Impact:
GRIP has made significant steps in understanding the working mechanisms of ESDs. The increased understanding has lead to improved ESD designs with higher efficiency gains resulting in a further reduction of the CO2 emissions from shipping.

Increased design knowledge, together with hull re-engineering technologies and optimised retrofitting processes, improve the position of the European ship yards for retrofitting ESDs to existing ships. This has a positive influence on jobs in the maritime industry and the position of the European maritime industry with respect to its competitors.

In this chapter, the impact of each objective reached is discussed including a summary of the dissemination activities undertaken to improve the impact of each met objective. A full list of all dissemination activities can be found in section A2 - GRIP Dissemination Activities.

4.1. Objective 1: Retrofit decision making tool
One of the main impacts the GRIP consortium want to achieve is to make the use of energy saving devices more widespread. One of the measures undertaken by GRIP to achieve this is the development of an Early Assessment Tool (EAT). Using this EAT, ship owners and operators can evaluate the optimal ESD for their vessel including the payback period.

In Work Package 1 the EAT was developed consisting of a benefit tool and a cost tool. The benefit tool calculates the benefit of an ESD from a hydrodynamic point of view resulting in a first estimate of the potential fuel saving. The EAT is available to all GRIP partners for use in their consultancy work.

As the EAT is not publically available, a simplified internet version was developed which is publically available through the website. Some simplifications have been made in the iEAT with respect to the EAT so that the calculations could be made available through a website. The iEAT is free of use.

Both the EAT and the iEAT have been validated and showed good correspondence between the (i)EAT predictions and more detailed calculations.

Furthermore a database with ESD performance results was developed from public available data. In total, the database contains 130 review sheets. Some basic statistical analysis was performed on the data. The average Energy Saving Ratios and the standard deviations in the results have been calculated for each of the ESDs. Within the different datasets for the specific ESDs, also subdivisions based on the source of information (model test, full scale measurement, CFD, etc.) and the assigned quality level have been made.

With the EAT and the iEAT, ship owners and operators can make a very quick evaluation of the potential fuel saving for a ship, class and entire fleet. An evaluation can be made within a couple of minutes giving a first indication of the potential fuel savings. This will give a hint if further design is worthwhile. The iEAT and the EAT will have a significant impact on the number of ESD applications. A reliable first estimate of the potential fuel saving will give the ship owners and operators more confidence in assigning the next step of detailed design and installation of the ESD.

A simplified version of the EAT was made available on internet to all European ship yards as a first assessment of the performance of the ESD. The website is: http://www.grip-ieat.eu

4.2. Objective 2: Hull re-engineering
For most existing vessels, the exact hull form is unknown as not every yard makes the hull lines available to the owners. This means that ship owners will have to go back to the original, often far Eastern, ship yards for retrofitting. To make the use of ESDs widespread and to stimulate the European maritime industry, a method needed to be developed in which the hull form could be re-engineered. With these re-engineered lines, ESDs can be designed for any ship by European ship yards.

GRIP has spent considerable effort on methods to re-engineer the hull lines of existing ships. Various methods have been investigated amongst which methods to determine the hull shape from inside the ship, under water measurements to photo and laser modelling of the ship while in dry dock. During the full scale demonstration, the laser modelling technique was used to measure the ship hull and the ESD in dry dock. All methods have been extensively evaluated documented in the GRIP project.

During the utilisation of the reverse engineering technology it has become apparent that a critical point in the evaluation of geometric data is the transfer of the product data into the various CAD-systems or other evaluation software. By the use of different software for measuring and evaluating, the number of the used formats is very high. This has the consequence that during the transfer between the formats, information or the structure of the data can be lost. Therefore, the used formats have to be defined before the work starts through communication between all involved partners. After reverse engineering of the hull form, better ESD designs can be made based on the true shape of the ship and appendages.

During the measurement campaign it was identified that the requirements of the evaluation of the reverse engineering measurement should be already clarified during the planning phase. It was found that geometric measurements can be evaluated in very different ways. Sometimes a protocol with test values or an Excel sheet with coordinates is sufficient, another time a 3D model or CAD data are required. To find out what result is demanded a clarifying discussion with the subsequent user is essential. The format for exporting the data is significant for the exchange with shipyards or design offices and should be coordinated with the involved parties. This topic is also discussed in detail in Deliverable 4.1. To accomplish the both points above it is necessary to have the right software. So it must be ensured that they can edit the data in the right way and can export the correct formats. For example some software cannot work with NURBS which is normally elemental for creating CAD models or sometimes they can only export specific formats.

With this, the GRIP consortium have considerably enforced the position of the European maritime industry with respect to retrofitting ESDs on existing vessels. Using the re-engineering techniques, European ship yards can determine the exact hull shape to be used in optimising ESDs. This will subsequently increase the applications of ESDs as better designs can be made, improving the energy saving capacity.

Dissemination of the results connected to this objective has been done. One paper was submitted in the TRA 2014 at Paris, titled “Efficient Retrofitting – How planning tools and reverse engineering methodologies can improve repair shipyards’ performance”.
The exploitable products from the GRIP project in the field of reverse engineering are,
• Benchmark procedure for selecting suitable measurement technology
• Measurement concept for capture of geometric ship hull data (planning, execution and validation of 3D-measurements)
• Modelling and transfer of measurement data to product data (CAD-Model)

4.3. Objective 3: Optimised retrofitting process
Similar to the impact related to objective 2 in the previous section, the impact of the optimised retrofitting process is to improve the position of the European maritime industry to conduct retrofitting of ESDs. By optimising the retrofitting process, the retrofitting can be done more efficiently making the European ship yards more attractive.

The execution of a retrofitting activity or any shipyard activity in a shipyard involves the integrated use of resources extending to different departments in the shipyard. Planning of resources in each of the department is very important not only for successful completion of an order but also for balance utilisation of the resources. The Simulation Tools will be a very helpful tool in making more precise planning. In order to implement the Simulation Tools, it is imperative to know the flow of planning processes which constituents to the final planning of all resources. It is therefore recommended as performed in the GRIP Project, that the shipyard processes be graphically represented in a flow chart, under different phases of the planning (Contract Negotiation, Order Planning, Production Planning and Production Process Planning). By performing such segregation of the processes, it will aid the shipyards to decide the possible areas of planning optimisation with the aid of simulation.

The data management is one of the important and time consuming parts of the planning optimisation with Simulation Tool. In order to aid the shipyard in the data collection and data handling, the anteSIM tool can be used.
The Implementation of Simulation Tools by Shipyards in planning has been made easier with the development of the two stage simulation concept which utilises either only the planning tool anteSIM or a combination of anteSIM and Plant Simulation. This concept was so developed that no simulation expert is required to perform the simulation studies. The concept developed allows the shipyards to use the Simulation as an external service utility.

The next stage of the development in the Simulation Tools and anteSIM planning tool would be to have more close contact with Shipyards, so as to aid them in providing solutions for improving their planning activities with the aid of simulation. By doing so, new needs of the shipyards planning activities could be further realised, as different shipyards have different planning methodology, and hence forth the further development of the Simulation Tools and anteSIM planning tool could be performed in parallel, so that its functionalities does not confine to the needs of only few shipyards with specific work methodology.

From End User’s perspective, ULJ were of the opinion that the presented results of Simulation runs were considered to provide valuable insight into Simulations as well as into usage of Reverse Engineering with Simulations. They consider that the solutions developed in the project are a good way to test baseline assumptions regarding resources, search for real bottlenecks, but also way to avoid overcapacity in any form. They also felt that the tools would be utmost importance in closely monitoring the planning requirements.

Using the anteSIM software, ship yards will be able to optimise and structure the retrofitting process. Furthermore, GRIP has shown the potential energy saving from ESDs making retrofitting ships with well designed ESDs attractive. European yards will become more attractive for retrofitting vessels as the optimised process leads to a more efficient process. This will subsequently lead to more ESDs being installed at European ship yards, maintaining or even increasing jobs within the industry.

Dissemination of the results connected to this objective has been done. One paper was submitted in the TRA 2014 at Paris, titled “Efficient Retrofitting – How planning tools and reverse engineering methodologies can improve repair shipyards’ performance”.

The exploitable products from the GRIP project from the simulation field are,
• Use of Business Process Model in future research projects
• The anteSIM software will be used as an aiding tool for the planning process.
• The database schema will be used to harmonise in collection planning data from shipyard specific planning databases.
• Simulation Model of ULJ will be used in future simulation studies of ULJ planning in future research projects.
• The definition of the Scenarios during the validation process will be used during future simulation studies

4.4. Objective 4: Characterise physical mechanisms
GRIP set out to radically decrease the uncertainty involved in the process by using state-of-the-art hydrodynamic studies to prove the worth of the designs of ESDs. This will increase the understanding of the energy saving resulting in better ESD designs which subsequently will result in more ESDs as the energy saving further increases. Improved understanding of the physical mechanisms furthermore provide the opportunity for completely new ESD concepts utilising the energy saving mechanisms to the fullest. By this, the CO2 emissions of European shipping can be reduced by up to 5%.

GRIP has provided a proper understanding of Energy Saving Devices in general, and in particular of the PreSwirl Stator, the Pre-Duct, the Rudder bulb and the Propeller Boss Cap Fins. A generic mechanism that we have observed in all effective ESDs is the reduction of rotational energy losses in the wake which could be achieved by either PreSwirl Devices (such as Pre Swirl Stator of Pre-Duct) or Post Swirl Devices (such as rudder bulb or Propeller Boss Cap Fins). Our understanding of the mechanisms has also been instrumental to the selection of analysis tools and simplifications of the model where desired. This has resulted in the recommendation that a full RANS-RANS modelling of the hull-propeller-ESD configuration using a rotating propeller is needed to fully quantify the effects of an ESD.

The limitations in the modelling of the aftship with a RANS-BEM model for the hull and propeller respectively have been identified. When these limitations are correctly accounted for during the early design process, this RANS-BEM model offers good opportunities to reduce the computational time significantly

The impact of our improved understanding of the mechanisms is also apparent in the effectiveness and efficiency of the design process. With the understanding of the physical mechanisms and the limitations of the various computational tools and models, we are now able to distinguish efficient computational models for the different phases of the design. RANS-BEM models have been demonstrated to be useful in the early design phase of Pre-Swirl stators. In later phases but also for other devices such as Propeller Boss Cap Fins or Rudder Bulbs, the use of RANS-RANS models is still preferred, due to the importance of viscosity in the flow or due to the difficulty of coupling a BEM method to the RANS method with due inclusion of interaction effects. It has been demonstrated that a RANS-RANS modelling of hull-propeller-ESD with a so called frozen rotor model (one chooses one or a few fixed blade positions) might lead to erroneous trends in the design, which was demonstrated for a PreDuct design. This computational model should consequently be treated with extreme care or if possible, probably be avoided

The methodology developed within the GRIP project allows to evaluate forces applied on an ESDs during navigation. The methodology takes into account the operational profile of the ship, the position and orientation of the profile, and the effect of the ship loading case. The study of the state art shows that ESD structure is sensible to Flow Induced Vibrations (FIV): Motions Induced Vibration (MIV), Vortex Induces Vibrations (VIV) and Turbulence Induces Vibration (TIV). For a Pre-Swirl Stator, the flutter (MIV) has been identified as the main risk of FIV. In this context, a numerical tool has been developed in order to evaluate the risk of flutter. The weak point of the ESD is the fatigue crack at the hull connection. The forces versus number of cycles can be evaluated with the methodology determined in the GRIP project. The importance of the connection design has been highlighted through several finite element models.

The CFD calculations done in Work Package 2 and 5 on the hydrodynamic mechanisms of ESDs have given insight into the working of these ESDs. It has been shown that pr devices improve the propeller blade efficiency for the upcoming blade while for the down going blade such device would have only a minor effect. This knowledge provided new insights in the design of ESDs and a new concept (the BSD) was tested for numerous ship types with varying success. In the design cases, considerable energy saving potential was shown up to 5% and in some cases even up to 10%. On average, the CO2 emissions of ships can be reduced by 5% if custom designed ESDs were to be installed, making use of the knowledge gained in GRIP.

Dissemination
The participation of Europort2013 and GST215 conferences and publication in Naval Architect and ISP are the main part of the external dissemination of GRIP results for Bureau Veritas. However, internal Bureau Veritas communication means (newsletter, Bulletin Technique) have been used to inform Bureau Veritas experts about ESD technology progress throughout GRIP project.
4.5. Objective 5: Design optimal Energy Saving Devices
As for objective 4, the impact of objective 5 is to decrease the uncertainty involved in the ESD design process through demonstration designs for selected ships. The demonstration designs increase the insight in ESD designs as the interaction between ESD and hull is different for every ship. This will result in yet again improved ship ESD designs.

Within GRIP, several types of ESDs have been actually designed and optimised for targeted vessels. Some new ideas of ESDs haven probed and proved their potentials for further applications. One ESD type – a Pre-Swirl Stator - has actually been manufactured, installed and evaluated on a handymax bulk carrier, demonstrated a 6.8% power savings in sea trials. This has fully fulfilled the initial objective of the project. Further, this validation case has enforced the design team to work closely with the yard and the classification society so that manufacturing limitations, strength, vibration and installation constraints can be fed back in the design, charactering a typical industrial retrofitting scenario.

It is expected that the careful way in which the computations and the designs have been made, will contribute to the credibility of similar CFD computations on ESDs, where at the same time, it is also demonstrated that a less than optimum modelling of the hull-ESD-propeller configuration (e.g. frozen rotor approach with only one propeller position considered) may even lead to wrong trends or design decisions.

Design optimisation process driven by automatic algorithm could allow engineer to find the global optimum of geometry of ESDs. The automatic design optimisation process involves different tools in the design loop: the parametric modeller, the grid generation tool, the self-propulsion simulations and the newly developed adjoint RANS solver to indicate the direction of the geometry changes. Such a design process has been demonstrated in the GRIP project, but still needs further development for industry applications.

Through the scale effect analyses of different types of ESD, the conclusion can be drawn that ESD designs should be conducted directly in full scale whenever possible; if the ESD design needs to be tested first in model scale, a later adaptation to full scale is often necessary.

GRIP reveals that it is extremely important and beneficial that the design of an ESD should be a collaboration between designer (both hydrodynamic and structural), ship yard and classification society so that manufacturing limitations, strength, vibration and installation constraints can be considered in the hydrodynamic design. Using a sensitivity analysis the requirements regarding manufacturing and installation tolerances can be determined which helps the yard in the final delivery of the ESD.

The design cases for the various ships have resulted in specific insights for the PSS, Pre-Duct, rudder bulb and PBCF. The parametric variations of both the ship and the ESD covered by the range of design cases, provides firsthand knowledge on early design choices and rules of thumb which lead to the starting point for a detailed ESD design. All this will lead to better custom designed ESDs for ships resulting in higher efficiency improvements and a larger positive impact on the environment.

Dissemination of the results connected to this objective has been done. Several journal and conference papers have been submitted, which can be found in the tables of dissemination A1 and A2.
The exploitable products from the GRIP project in the field of hydrodynamic designs of ESDs are:
• Developed ESD design procedure and methodology for each ESD type
• Improved procedure for ESD performance evaluation
• Improved knowledge on scale effects of ESDs
• Application of suitable numerical methods in hull-propeller-ESD interaction

4.6. Objective 6: Validation of optimised ESD
As for objective 4 and 5, achieving objective 6 adds to the reduced uncertainty in ESD design. This will result in better ESD designs custom made for each ship. Achieving objective 6 was done through full scale validation trials of a dedicated ESD design.

The validation of the ESD by means of the trials are considered as a unique case; dedicated dry dockings where only an ESD is installed are rarely done in practice due to the high costs and requirement for off-hire of the vessel. The exceptionally fair weather conditions in the Adriatic sea in combination with the use of the same instrumentation and trial team for both trials resulted in highly accurate performance data. Moreover, the trials were done by an independent team with no commercial interest. This combination results in a unique showcase to the industry and gives an objective proof that pre-swirl stator fins can be highly efficient. This should give the industry confidence in ESDs and support them in their decision to retrofit ships with ESDs in general.

In Work Package 6 one of a kind dedicated speed trials were done by an independent party providing top quality unique results. Not only do the results contribute significantly to the confidence in ESD design and ESD performance, also valuable guidelines were given to grasp the uncertainty of speed trials related estimating performance of an ESD. This unique data set is of primary importance to the maritime industry regaining confidence in the performance of ESDs.

During the Green Ship Technology Conference in Copenhagen, 2015, the trials and results were presented and published for a large group of ship owners, to emphasise the proven savings that can be made using pre-swirl Energy Saving Devices, and to show how ESDs can and should be validated using full scale trials. A paper is written in the International Shipbuilding Progress giving further details on the trials and results. Furthermore, as the results and cavitation observations can be shared publicly, the results will be used in future presentations and workshops to indicate the proven benefits of ESDs.

List of Websites:
http://www.grip-project.eu/

Final Report Summary - GRIP (Green Retrofitting through Improved Propulsion)

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