Toward the Fastest Unstructured CFD Code "FaSTAR"

Along with the system development of “Digital/Analog-Hybrid Wind Tunnel” at JAXA, a fast CFD code is required. Based on the investigation of well-known unstructured CFD codes, we have determined the target performance and specification of CFD code. This is then followed by the development of a fast unstructured CFD code “FaSTAR”. The accuracy of drag prediction with FaSTAR is validated by the DPW4 benchmark problem. The computed drag coefficients generally agree with other results. Since we employ the Cartesian-based unstructured grid generated with HexaGrid, the predicted drag is affected by the choice of discretization method, whether it is cell-center or cell-vertex. Moreover, the reconstruction method is found to be important. This affects the drag prediction accuracy and the smoothness of surface pressure distribution. The computational speed of present CFD code is 1.8 hour/case with 10 million grid and 100 cores for a standard civil aircraft. The multigrid method with the global coarse grid shows four times faster convergence than that with the zonal coarse grid. Here, the coarse grids are generated utilizing the octree data of Cartesian grid.