Efficient Aero-Acoustic Simulation of the HART II Rotor with the Compact Pade Scheme

Abstract

One major diffculty in the design of quiet rotor blades is the correct numerical prediction of blade vortex interaction (BVI) noise in descent flight. Current second order spatial discretization schemes inherently have too much numerical dissipation to correctly conserve vorticity in the computational fluid dynamics (CFD) simulation. Higher order methods have proven their worthiness to alleviate this problem, yet are costly in terms of computational resources. In this paper, the 4th order implicit compact Pade scheme based on the finite difference formulation of the RANS equations is employed to convect the vortices in the simulation. The approach is paired with the classical finite volume approach with the Jameson-Schmidt-Turkel (JST) scheme. The robustness and flexibility of the JST scheme are exploited in the nearfield of the rotor blades and fuselage, while in the mid- and farfield the Pade scheme is utilized. This approach is validated against the experimental data of the HART II wind tunnel campaign. Different grid resolutions are examined as well as simulation strategies ranging from inviscid isolated rotor simulation up to viscous simulation including the fuselage. This hybrid simulation technique demonstrates the usefulness due to its high efficiency, while for design purposes the simplified physics yield an additional speed-up of the turn-around time.