Abstract:

A numerical method for modeling the aerodynamics of bladevortex interaction (BVI) is developed which adopts the unsteady Euler equations in inertial coordinate systems to capture the features of the rotor BVI flow and uses the overset grid technique to realize multizone solution and information exchange in forward flight. To incorporate the effect of the vortex in the solution, an effective approach, called the “generalized gridvelocity approach” is presented to simplify computation. Numerical examples on the rotor BVI flow field are performed by this method, and a comparison of the calculated results with available experimental data demonstrats its validity. By comparing the pressure variations for various chord locations, it is shown that the BVI loading is mainly caused by the high rate of change of the pressure within 10% of the leading edge. Furthermore, additional calculations are carried out to analyze the effect of vortex strength, miss distance and interaction angle on the aerodynamic characteristics of BVI. The present investigation indicates that lift reaches its maximum when the vortex position is slightly upstream of the leading edge of the airfoil, and that the circulation on the blade surface suitable for the trailingedge Kutta condition is altered by the induced velocity of the vortex passing the trailing edge, but it starts to be reestablished as the vortex moves farther away.

Key words: blade-vortex interaction, generalized grid-velocity approach, Euler equations, overset grids, rotor, helicopter