Methods of adaptive unstructured grid based on the image process methodology

Solution-based grid adaptation is a subject of great significance to the practical application of unstructured grid in CFD simulations, especially in the simulations of complex flow phenomena. The paper presents an efficient solution-adaptive procedure, based on the image process methodology. It regards the grids as the analogical pixels of picture, and the values of flow parameters (density, velocity, etc) as the gray. The image process techniques are employed to isolate the regions in the field which contains physical features of interest. These regions are reduced to several groups of simple geometric entities representing the physical features via a feature detector function, which contains different values. Therefore, the transition region of adaptive grid between the finer and initial regions will be generated automatically after the adaptive procedure, and the quality of the adapted mesh is ensured. The refinement and coarsening techniques, implemented based on the values of the feature detector function, are developed as well. The procedure was coupled with a flow solver. Results were presented for a variety of CFD applications. The method is successfully shown to be effective for aerodynamic applications, detecting regions of interest, etc.