A Hybrid Grid Generation Using Unstructured Prismatic and Cartesian Grids

Abstract

A hybrid gri d generation method based on prismatic and Cartesian grid is being developed. The main objective is to generate grid around c omplicated geometry for compressible and viscou s flow simulation , especially that with high Reynolds number . The method is based on unstructured grid, which treats cells as arbitrary, unstructured polyhedra. By invoking a combination of Cartesian, prismatic, and cut cell generation modules, user can produce grid for specific simulation needs. At present, development is focused on pris matic grid generation. An advancing layer strategy that incorporates a number of advancing steps to make a prismatic layer is discussed, along with a smoothing technique. Results seem to be favorable, although computation can be time consuming. 1. Introduct ion As CFD plays an increasingly greater role in flow analysis and design, it is demanded to handle even more realistic cases. One of the cases that still pose a computational challenge is simulation of viscous flow at high Reynolds number. At this condit ion isotropic grids normally employed in inviscid and low - Reynolds -number flow simulation will perform very poorly, especially in region close to body surface. When the grid is non -body -fitted, as in the case of Cartesian grid, the situation becomes worse , due to irregularity in cell size at body surface. This is true even when anisotropic grid is employed. Thus a hybrid grid method to carry out such simulation is being developed in National Aerospace Laboratory (NAL), Japan. This study is the continuatio n of the previous in anisotropic Cartesian grid for inviscid flows. 1