Research On Implicit Surface Modeling And Volume Mesh Generation

With the development of computer technology,the CFD method has been attracting more and more attention.How to accurately and efficiently simulate various flow phenomena through the CFD method has become the focus and difficulty of fluid mechanics research.In the field of marine and marine engineering,it is also a hot spot to evaluate the hydrodynamic performance of various ships and marine structures by means of the CFD method.For the CFD method,geometric modeling and mesh generation are the basis for numerical simulation of the flow field.The quality of geometric models and mesh generation will directly affect the accuracy of CFD computation.For this reason,the geometric modeling and volume mesh generation methods for CFD preprocessing are studied in this paper.In this paper,under the framework of boundary-fitted and non boundary-fitted methods,geometric modeling and mesh generation methods are introduced first.The Cartesian mesh is a hot topic at present.Compared with the body-fitted mesh,the Cartesian mesh is more suitable for processing multi body movement and large deformation.The implicit surface model has natural advantages in identifying inside and outside regions of the objects and describing complex structures.In this paper the background Cartesian mesh based radial basis function implicit surface construction method is introduced.The surface is expressed as the isosurface of an implicit function.Surface modeling can be achieved by extracting the isosurface.Besides,background mesh refinement technology is introduced to obtain more surface points in local areas,so as to better describe detail of the surface and improve the quality of surface modeling.In view of the mesh generation,the volume mesh generation technology based on radial basis function is developed in this paper.The surface mesh and the mesh generated by advancing the boundary grid points are treated as boundary conditions of the volume mesh generation.The radial basis function is used to determine positions of grid points inside the boundary.Whether the surface mesh is structured or unstructured,volume mesh can be generated.Since the volume mesh generated using this method bears characteristics of structured mesh in normal direction of thesurface,it is suitable for simulation of the boundary layer flow.In addition,according to the characteristics of the hull,surface and volume mesh generation methods are developed for application in ship and ocean engineering.The hull surface mesh generation method is based on Hermite spline interpolation.The hull is divided into a few zones and surface mesh is generated in each zone according to the shape of the zone.Surface mesh of the hull is obtained by combining the surface mesh in each zone.Volume mesh generation is based on the idea of the advancing front method.On the basis of surface mesh,the initial advancing mesh is generated first.Then the grid points are advanced along their normal directions.Finally,grid points are connected according to certain mesh topology.The effectiveness of the methods are validated with surface and volume mesh generation of the KCS hull.