Numerical Simulation of Subsonic Unsteady Flow around Wings and Rotors

Abstract

An unsteady 3D Panel method has been developed to compute the subsonic aerodynamics of finite thickness wings and multiblade rotors. The free wake is simulated by a lattice of shed and trailing vortices. The method is applied to wings in pitching and plunging motion, to a two blade and the four blade BO 105 hingeless rotor in hover. The four-blade rotor has also been studied in the forward flight descent and climb modes. Computed wake geometry of the wings agrees well with two-dimensional code results and with smoke trace experiment results. Prediction of pressure distribution on blade surface during hover agrees very well with wind tunnel test data and Euler solver results. Results for descent flight where severe blade vortex interaction (BVI) takes place are in fair agreement with the experiment. The time stepping scheme employed permits a detailed study of the wake development. This is done for the descent case of the BO 105 four blade rotor to indicate areas of possible severe BVI. No restrictions are placed on the prescribed wing or blade motion, blade profile, planform, twist etc. so that a single code can treat wings or multiblade rotors in a variety of flight conditions.