Calculation For Resistance Of A Ship With Bulbous Bow And Comparison With Experimental Data

Ship resistance research has always been the hot spot that scholars pay attention to.At present,there are a lot of CFD commercial software can be used in the study of ship resistance.How to choose the appropriate software for the ship resistance prediction and design optimization is a very important problem.A ship model with bulbous bow and transom stern is used as the object of study in this paper.Total resistance is measured at 9 speeds by towing tank.At the same time,ANSYS CFX and SHIPFLOW are used in numerical simulation of resistance respectively.Numerical simulation results are compared with experimental data to analyze the similarities and differences between these two software in different aspects.This paper reviews three basic methods of studying ship resistance,and summarizes the development of ship resistance research at home and abroad.The causes and classification of ship resistance are studied theoretically.The principle of ship model test is introduced in this research.While towing tank test is conducted in Vienna Model Basin Ltd.The open water test,resistance and self-propulsion tests are carried out.The resistance values of the ship model under different speeds are recorded by the above experiment.Hexahedral cells were generated for the whole calculation domain using POINTWISE.The generated grids are imported into ANSYS CFX for numerical simulation.Volume of Fluid(VOF)method is employed for studying free surface.Total resistance is calculated every 0.5 knot(kn)(except 15.5 kn and 16.5 kn),when ship speed is [15kn,20kn].Numerical simulation results are compared with experimental data in these 9 situations.A series of visual flow field pictures can be get from the results.Another numerical simulation software SHIPFLOW is used to calculate the resistance of the ship model in this paper.ZONAL method is used in SHIPFLOW and is combined with the potential flow and viscous flow to calculate the resistance.The parameter commands of modules were set.The total resistance coefficients and friction resistance coefficients were acquired by calculation.Friction resistance coefficients are compared with theoretical values which calculated by 1957-ITTC formula.And total resistance values are compared with experimental data.Finally,through the accuracy of the total resistance calculation results,the details of the flow field and the consumption of resources,the similarities and differences between ANSYS CFX and SHIPFLOW are analyzed in this case.Results indicate that the CFD calculation values of the two commercial software are consistent with the experimental values and they are able to satisfy the engineering application of ship resistance prediction.And in the complete ship-speed range,the average errors of ANSYS CFX and SHIIFLOW are 0.9% and 7.3%.Calculation precision and application scope of the former are superior to those of the latter while the calculation efficiency and pre-processing operation of the latter are superior to those of the former,and both of them are able to capture the details of flow field.