Some challenges of realistic flow simulations by unstructured grid CFD

This paper discusses the unstructured grid method to compute flows around geometrically complex bodies having relative motions. To enhance the capability to treat complex geometries, a surface triangulation method using the advancing front method coupled with geometric feature extraction technique is described. Stereolithography (STL) data are adopted as an interface between a CAD system and the surface grid generator. Moving bodies are treated by the overset unstructured grid method. The capability of the method is demonstrated for simulations of an airplane separation process from a rocket booster and a hornet in flight. In the hornet simulation, the detailed components such as antennas, legs and a sting are all included in the computational grid. The flapping wings are treated by the overset unstructured grid method where a grid around the wing is overlapped on a stationary grid around the body of a hornet and moves with time to simulate the flapping motion.