Free-wake analysis of compressible rotor flows

A method for computing helicopter rotor flowfields is described that is fully compressible, and which computes the wake without requiring external specification of any flow quantity. Also, it is unified, treating the blade and wake regions as a single domain. It is quite different from most compressible treatments which require that the regions be treated separately. The method has been developed into a computer program, 'HELIX I,' for the computation of compressible rotor flowfields in hover with free wakes. Results of this program are also described. The method utilizes a generalization of a compressible finite-volume potential flow scheme. This scheme has been extensively used in the fixed-wing industry for research and wing design, and has been shown to be effective for resolving shocks and to be in good agreement with experiment for subsonic and transonic flows.