Numerical generation of composite three dimensional grids by quasilinear elliptic systems

摘要

A technique is presented for constructing a boundary-conforming grid throughout a general three-dimensional flow region as a composite of subregion grids. Each subregion grid is generated numerically by solving a quasilinear system of elliptic equations. The boundary values represent nodal points in a quasi-two-dimensional grid that covers the curved surface bounding the subregion, and are generated numerically by a modified elliptic system. The boundary values are used to compute grid control parameters that are contained in the elliptic systems. This provides flexible control over the distribution of grid points in the interior of the region, in that the interior grid distribution is governed by the distribution of points on the boundary as well as by the boundary's geometric shape. A primary feature of the technique is that the composite three-dimensional grid remains both continuous and smooth across the surface of the juncture between any two adjoining subregions. The present paper elucidates the details of the method and of its implementation, and displays numerical results for both surface grids and space grids. Comprehensive results are displayed for a three-dimensional grid about a simple wing-body combination. A numerical example is presented of a surface grid on a NACA 0012 airfoil, with high resolution of the wingtip region.