Adding Hybrid Mesh Capability to a CFD-Solver for Helicopter Flows

The enhancement of the so far structured Computational Fluid Dynamics solver FLOWer to enable the use of hybrid meshes and its advantage to numerical helicopter simulations is presented. The improvement is conducted by the implementation of unstructured grid handling into the existing code framework. The aim of the implementation is to reduce meshing effort in near body regions requiring the mapping of complex surfaces including boundary layer extrusion. Using the hybrid mesh approach, off-body regions can still be solved with structured meshes using computationally efficient higher order methods. This off-body region can be meshed automatically using Cartesian grids. The unstructured module features a second-order reconstruction scheme with an efficient GMRES implementation to solve linear systems of equations. Efficient high performance computation is ensured by multi-blocking and efficient load balancing considering the computational effort of the block according to the mesh type and numerical methods applied to. A forward facing step test case provides a reliable reproduction of different physical phenomena. An application-oriented complete helicopter simulation with particular use of unstructured body grids demonstrates the benefit of the hybrid mesh approach regarding our regular work flow.