Boundary conforming discontinuous Galerkin finite element approach for rotorcraft simulations

A numerical method has been developed for predicting the complex vortex wake for a helicopter rotor in hover and in forward flight. The method is based on the solution of the three-dimensional, compressible Euler equations expressed in an arbitrary Lagrangian Eulerian reference frame. A second-order accurate discontinuous Galerkin finite element method is used to discretize the governing equations on a hexahedral mesh. Unstructured, local mesh refinement is performed to enable prediction of the structure of the vortex wake. The capabilities of this computational fluid dynamics method are demonstrated by simulations of the How around the Caradonna-Tung helicopter rotor in hover and simulations of the flow around the Operational Loads Survey helicopter rotor in forward flight. Accuracy of the method is assessed through comparison with wind-tunnel data, if available. Special attention is given to a rotor trimming procedure developed at the National Aerospace Laboratory/NLR and to the grid adaptation algorithm.