Aeroacoustic investigation of multi-directional wings aligned in tandem under wing-in-ground effect

Abstract

The aero-train is an innovative, high-efficiency, and low-consumption vehicle that uses the wing-in-ground effect. It utilizes orbital high voltage to obtain a high lift-to-drag ratio while generates significant noise, which is dominated by the trailing-edge noise from the multi-directional wing. Study of trailing-edge noise generation and propagation is of great significance in realizing the active and passive reduction of the trailing-edge noise; however, various types of mechanisms of the trailing-edge noise under near-wall conditions are unknown. In this study, multi-directional wings with different relative spacings aligned in tandem at 0.3 Mach are numerically simulated using the large eddy simulation combined with Möhring acoustic analogy theory. Numerical results indicate that a spacing of six times of the chord length produces the lowest sound pressure level. Moreover, based on an analytical concept of the main frequency contribution of the source region, the frequency response function of each frequency of the source region is integrated. The results of integration indicate that the dominant noise component is the low-frequency noise below 200 Hz, and the low-frequency noise generates from the wing trailing edge, the wake area, and the aileron tip. In addition, low-frequency noise dominates sound propagation owing to its strong ability of the diffraction and penetration. For the ground effect wing (GEW), the orbital wall surface increases the turbulence around the airframe, creates more chaotic vortex structures, and produces greater noise. This study provides a theoretical basis for noise suppression through optimizing and controlling the GEW trailing edge.