Compressibility effects on the unsteady aerodynamics of a rotor in hover or axial flight

An extension of TEMURA (TEchnion Model of Unsteady Rotor Aerodynamics) to include compressibility effects is presented. This is a three dimensional detailed model that includes the effects of the bound vortices of all the blades, as well as the wakes of all the blades that are comprised of shed and trailing vortices. The wake geometry is a general three-dimensional one and is an input to the model that can be obtained from a theoretical analysis or experimental measurements. In order to make the model more efficient it is based on a combination between analytic and numerical derivations. The model is verified by comparing its results, for simplified cases, with results for similar two-dimensional cases from the literature. After verification the model is used to study the relative influence of shed and trailing vortices, and the effect of compressibility on both. It is shown that trailing vortices, which were neglected in previous models, may have a significant influence in practical cases and therefore their effect should be included in any analysis.