A DUAL MESH APPROACH TO ENHANCE ACCURACY OF THE BOUNDARY CONDITIONS FOR UNSTRUCTURED GRID MODELING OF TURBOMACHINERY FLOWS

摘要

Although unstructured grids have gained wide acceptance in many engineering applications, they still suffer from difficulties in achieving high accuracy at the inflow, outflow and mixing-plane interface boundaries of multi-stage turbomachinery configurations. To overcome these difficulties and hence to increase the accuracy of unstructured grid methods, a novel dual mesh approach is proposed. In contrast to conventional CFD techniques, the dual mesh approach works on two sets of meshes at the boundaries: one is the original mesh and the other is an auxiliary surface mesh created at run time. By properly coupling of such double meshes, the dual mesh approach can effectively increase the accuracy and conservation of the solutions at the inflow, outflow and mixing-plane interface boundaries, and it can also enjoy most of the sophisticated numerical algorithms originally developed for the structured-grid boundary conditions. With both compressor and turbine test cases, the dual mesh approach is demonstrated to be superior to the conventional method while its CPU-time penalty is marginal. Additionally the dual mesh approach may be also useful for any structured CFD solvers subject to some restrictions on the structured grid distributions at the inflow, outflow and mixing-plane interface boundaries, e.g. mesh uniformity in the circumferential direction.