高精度マルチブロック流体計算のための一般化特性インターフェイス条件の構築とその性能評価

Abstract

In practical fluid computation with structured grids around complex geometries, singular points can be frequently found where abrupt grid line changes exist. The grid singularities cause troublesome problems when some finite difference scheme with high accuracy and resolution is applied. Excellent theory has been proposed, which solve the above singular problem by decomposing a computational domain into two blocks along a line or a surface which contains the singular points and by imposing the characteristic interface conditions (CIC) at the block interface. However, the original theory has constraints on a combination between the adjacent computational coordinate definitions; these two coordinates have to be the same direction on the block interface. For a flexible coordinate arrangement without the restriction, the original CIC is further extended, and the generalized characteristic interface conditions (GCIC) are newly derived. Consequently, the coincidence of the computational coordinate definitions becomes unnecessary, and more flexible multi-block computation can be realized successfully. In this paper, vortex convection problems with grid singularities are solved to validate the GCIC. Besides, conventional multi-block treatment with overlapped domain technique and that with averaging procedure are also tested and compared to investigate their superiorities and inferiorities. As a result, it is confirmed that the GCIC have excellent performance in the multi-block computation and can be straightforwardly applied to a detailed unsteady flow simulation such as direct computation of aero-acoustics.