| The mandatory implementation of the Energy Efficiency Design Index(EEDI)requirements,as well as the minimum propulsion power requirements of the ship’s main engine for the navigation safety considerations,have further enhanced the efficiency and accuracy requirements for performance prediction in ship’s scheme design stage.It also strengthens the importance of design optimization regarding speed performance in ship products development.Under this background,this paper has carried out research on the prediction techniques of the ship rapidity performance and the associated navigation safety problem.The ship performance in both calm water and wave conditions are predicted based on the computational fluid dynamics(CFD)technology and the experimental method,and the reliability of the technique has been verified by comparing with the sea trial data.The research will contribute to the industry on the carbon emission reduction requirements of EEDI and the more stringent carbon emissions reduction regulations in the making by IMO.Further,it is expected that the study may provide technical reference and reserves for the formation of a generally recognized calculation method or a relevant industrial standards.In terms of calm water condition,numerical analysis models for propeller open water characteristics,ship resistance and self-propulsion performance are established.The numerical simulation,model test and sea trial are performed based on a new building 110,000 DWT oil tanker(Aframax oil tanker),all the above results are compared and discussed.Furthermore,the stern profile optimization of the Aframax tanker is carried out,and the ship-propeller coupling performance of different modification is analyzed.In terms of wave condition,in response to the current industry’s concerns about minimum propulsion power in adverse conditions and speed losses due to wind and waves,the wave added resistance calculation method is studied,and the influence of wave added resistance calculation errors on speed losses,together with the minimum propulsion power are analyzed.Besides,the numerical simulation method of ship self-propulsion under random sea conditions is studied,and the accuracy of this method is verified by physical model tests.The main work of this paper is summarized as follows:(1)Interpreting the relevant IMO documents,systematically reviewing the development history and calculation method of the Ship Energy Efficiency Index(EEDI),investigating the research progress of ship rapidity prediction in actual sea conditions and dissecting the specific problems faced by the engineering community.(2)Focusing on the characteristics of the ship’s physical rapidity problem,the model test method for predicting wave resistance increase under regular wave condition,the model test method for ship self-propelled in irregular wave,the test data analysis method and the power forecast method are studied.Furthermore,based on the CFD numerical simulation platform and model algorithm,the basic control equations and boundary conditions of the flow field are studied,and the key issues of rapidity and propulsion numerical simulation,such as flow field viscosity,free liquid surface,moving boundary,regular and irregular waves,and the corresponding numerical simulation methods,such as turbulence model and fluid volume function method in CFD numerical method,dynamic mesh technology,and numerical wave generation(elimination)technology have been studied and explained in detail.(3)Engineering numerical simulation models and evaluation methods of the propeller open water performance,ship resistance and self-propulsion are established.The results derived from numerical simulation,towing tank experiment and sea trial monitoring are analyzed and compared.Based on the research,the stern profile of Aframax oil tanker is transformed,and the ship propeller integrated analysis and scheme optimal selection are carried out.(4)For the determination of the speed losses due to wind and waves in the EEDI calculation and the calculation of the minimum propulsion power during navigation in severe sea conditions,the research on the calculation method of ship wave added resistance is carried out.First,by conducting grid effectiveness analysis,a grid generation method that takes into account computational efficiency and accuracy is established.The wave added resistance transfer function of typical ship speed and wave length is calculated,and the wave added resistance of ships in certain random sea conditions is predicted by spectral analysis method.Then,a physical model experiment of wave added resistance is carried out,and the numerical analysis results are compared with this experimental results.Besides,the calculation method of speed losses and minimum propulsion power based on wave added resistance are studied,and it is verified that the calculation method proposed in this paper has reliable engineering accuracy when used for predicting the speed losses and minimum propulsion power.(5)At present,there are few research achievement on the self-propulsion simulation with regards to irregular waves.As a research focus,based on the general CFD software platform,this paper proposes a simulation method for the ship’s self-propulsion in random waves.A multilevel motion mode is used to handle the six-degree-of-freedom motion of the ship in waves and the superimposed rotation of the propeller relative to the hull.The background domain,hull domain,and the propeller rotation domain grid and their interfaces generation method are discussed in detail.In addition,the difference in calculation accuracy and efficiency between sliding mesh method and overset mesh method for simulating propeller motion is studied,and engineering application suggestions are given. |
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