Non-reflecting boundary conditions on unstructured grids

Abstract

Non-reflecting boundary condition at interfaces for flow simulations in turbomachinery using the method laid out by Giles [1] and Saxer [2] require averages or Fourier decomposition of the flow solution using stations of constant radius at the interface. On structured grids the grid generation process can easily enforce grids having element centers with this property while on unstructured grids this is rarely achievable. We describe an approach which works on an auxiliary mesh with a band structure created from the surface mesh at interfaces and study the influence of the prescribed distribution of the bands on the solution. The effectiveness of the approach is demonstrated by applying it to the simulation of a compressor stage and comparing the results with results obtained by using the existing approach for creating bands and a simulation on a structured grid.