Improvement And Application Of Hull Form Surface Deformation Method Based On Radial Basis Interpolation

Ship hull optimization,as an important means of energy-saving ship type research and development,has attracted more and more attention at home and abroad.The deformation method of the hull surface is a key part,which determines the success of ship hull optimization.Among the many methods of hull surface deformation,Radial Basis Function(RBF)interpolation can better achieve smooth surface deformation.Our team focused on in-depth research on the RBF method in the early stage,but there are still the following problems:(1)The shape parameter of the basis function is the key to the deformation of the surface and affects the quality of the deformation.The existing research seldom considers the influence of the shape parameter on the deformation;(2)In practical engineering applications,constraints such as general layout are often considered.When there are many constraints,the efficiency of using radial basis function interpolation deformation is low;(3)Radial basis function interpolation deformation is suitable for the deformation of local surfaces,and cannot be used for the deformation of global surfaces.This paper focuses on the following researches on the above-mentioned issues.(1)Comparative study of basis functions.In the research of surface deformation method based on RBF interpolation,the choice of basis function is the key to the interpolation deformation.The paper compares the error and smoothness of typical basis functions to obtain the optimal basis function and broaden the selection range of basis functions.(2)Radial basis interpolation solution method based on conjugate gradient method.In the previous research of the team,the LU decomposition method was mainly used to solve the coefficient equation system constructed during the interpolation process,and the solution rate was low.To solve this problem,the paper converts the constructed coefficient matrix into a positive definite matrix,and uses Cholesky decomposition to reduce the condition number,and finally uses the conjugate gradient method to solve the problem to improve the efficiency of the radial basis function interpolation deformation method.(3)The deformation method of the hull surface based on the cross-sectional area curve.Aiming at the problem that the RBF interpolation surface deformation method cannot achieve global deformation,a hull surface deformation method based on the Sectional Area Curve(SAC)is proposed,which realizes the automatic generation of the hull surface.(4)Application of surface deformation method based on SAC and RBF in ship type optimization.The surface deformation program based on SAC and RBF is embedded in the multidisciplinary comprehensive optimization platform for ship hydrodynamic performance(SHIPMDO-WUT)developed by the team,taking the standard Series 60(S60)ship type and the standard kriso Container Ship(KCS)ship type as an example,and realizing global and local type optimization.