A CFD METHOD WITH CARTESIAN GRIDS AND COMPLEX GEOMETRIES DEFINED BY CELL POROSITIES

摘要

A CFD method for automotive cooling air flow applications based on structured cartesian grids and a cell based porosity approach to represent geometry is described. Steady Navier-Stokes equations with turbulence models are solved with a finite difference method using narrow-stencil upwind differencing. Fans and heat exchangers are represented by experimentally based models. The differencing scheme is a three dimensional implementation of a technique described in two dimensions by Sidlikover and Brandt[l]. The CFD code has been optimized and parallelized for RISC computers, vectorized parallel computers, and massively parallel computers. Geometry is represented by a series of triangular elements, but other representations could be used with the method. A completely automated preprocessor calculates porosities which represent intersections of the grid with the geometry. The porosities define an approximate surface representation of the actual geometry. Wall functions based on normal distances to surfaces and actual surface areas are used for wall boundary conditions.