Simulation of tiltrotor fountain flow field effects using a finite volume technique - An aero-acoustic study

This paper presents the results from an aero-acoustics analysis for a tiltr otor obtained by coupling an efficient Navier-Stokes solver, ROTTILT, with the acoustic code WOPWOP, The flow solver is finite volume based and solves the three dimensional, steady, laminar, incompressible equations in Cartes ian coordinates. The acoustic code WOPWOP is an implementation of Farassat' s linearized formulation IA, Predicted and measured fountain velocities are presented for a 15 percent V-22 semi-span model. Predicted and measured ae rodynamic performance and noise results are presented are for an XV-15 tilt rotor vehicle in hover, A semi-span configuration which includes the fusela ge, wing, and nacelle is used to model a full vehicle. The trimmed solution includes the combined effect of the rotor and body. Thus the computation o f rotor blade airloads are determined for a given thrust, which includes th is combined effect. The computed high resolution airloads are used as the i nput to the noise prediction program WOPWOP. The accuracy of the computed a irloads, flow and noise are evaluated by comparing with measured acoustic f light data. The predicted results show fair but promising correlation with the available data.