Study On The Rapid CFD Modeling Of Ship Based On NURBS Representation

CFD calculation is the main numerical method for predicting the hydrodynamic performance in the early stage of hull surface design.At present,CFD preprocessing is usually completed by commercial grid software or secondary development based on it.In the process of ship design,local modification of hull surface is often made,leading to high repeatability and low efficiency in similar ship form's CFD modeling process.Non-uniform rational B spline(NURBS)is a mathematical tool frequently used for hull surface design and representation.However,there is no report about the research on rapid CFD modeling based on design model represented by NURBS.To a certain extent,the design of hull surface and the analysis of hydrodynamic performance are disjointed.Therefore,in the field of ship design,the degree of integration of hull surface design and CFD analysis is of great significance to the new ship form development and ship optimization design.In this paper,we firstly start with the plane curve based on NURBS,and develop a speed-generating program of CFD modeling by curve being the boundary of fluid domain.Taking the problem of flows around circular cylinder as an example,CFD mesh is generated rapidly.Then a rapid modeling program is developed to generate the structured grids based on ship surface represented by NURBS.It can generate the grids simulating the fluids around the simple ship forms,and is applied to the Wigley and Series-60 ship based on NURBS separately.The mesh is automatically generated through a small amount of parameters by user.The obtained mesh is calculated by the commercial software FLUENT.It is proved that the rapid modeling program can be used to generate the mesh model rapidly.In order to develop the rapid modeling program,we should obtain the whole fluid domain's discrete grid nodes based on the hull surface represented by NURBS in the ARX programming environment.Then,the grid nodes and cells are numbered,and every grid cell is defined to generate the structured grids which can be calculated by the CFD software.For a simple ship form with flat bottom,the rapid CFD modeling program can achieve the transformation of the hull surface represented by NURBS to the mesh model,and generate the corresponding CFD grids by inputing a small amount of control parameters rapidly.The modeling program developed in this paper makes a good foundation for the rapid CFD modeling of complex ship form based on NURBS representation.