Grid Auto-Generation Technique And Its Application On The Numerical Prediction Of Ship Hydrodynamic Performance

In recent years, with the rapid development of computer science and numerical mathematics, researches on problems of fluid mechanics have stepped into the Computational Fluid Dynamics (CFD) era, especially when the commercial CFD packages are getting mature now. As an important branch of hydrodynamics, more and more attention is paid to CFD methodology. In the field of naval architecture, it makes great sense to improve the calculation accuracy and efficiency of CFD technique. And a definite trend is to apply CFD methodology in ship hull optimization and novel hullform development, namely to develop the optimal hull form on the basis of numerical simulations from the viewpoint of hydrodynamic performance.Grid generation is one of the most significant aspects for numerical computation, and grid quality plays an essential role in the calculation precision of final results. It needs much professional knowledge and expertise to generate the high-quality computational grids. Generally, it takes a ship CFD engineer a lot of time and effort to generate a set of high-quality computing grids, which hinders further application of CFD in ship engineering. Furthermore, in the process of introducing CFD method into the field of shape optimization and novel hullform development, a large amount of time is spent in generating meshes for hullforms that are similar in geometry, which decreases efficiency greatly.In order to improve the efficiency of naval CFD computation and numerical shipform optimization, hybrid grid auto-generation software HIGOT and structured grid auto-generation software SUGOT are developed on the basis of the general CFD preprocessor Gambit. The applications, HIGOT and SUGOT, starting with the IGES files which describe the hull shape, make the batch files according to the information of vertexes, edges and faces, start Gambit to run the batch files automatically and then update the information of vertexes, edges and faces by themselves. Based on the hull characteristic, the computation requirements and so on, the grid auto-generation software can control to accomplish the division of computational domain, the grid generation and the setting of boundary conditions by parameterizing.This paper makes use of the IGES files of the KVLCC2M model and two container ship models to validate the software's robustness. To KVLCC2M hull, the grid dependence research of CFD drag prediction and maneuverability prediction is carried out. To TEU3100, ship stern deformation's influence over drag, maneuverability and propulsive performance is deeply investigated. To another container ship model, the strengths and weaknesses of hybrid grid and structured grid on the free surface prediction are discussed.It is proved that the softwares HIGOT and SUGOT can generate the CFD computation grids of ordinary ships automatically, and they can save the time of mesh generation greatly, which is taken as the basis of simulation based design of ship hulls.