Acoustics of Transonic Flow Around an Oscillating Flap

Abstract

Investigation of noise mechanisms due to unsteady transonic flow is important for aircraft noise reduction. In this work, the near-field impulsive noise due to an oscillating flap is simulated numerically. The problem is modeled by the two-dimensional high frequency transonic small disturbance equation (VTRAN2 code). The three types of unsteady shock wave motion have been identified. Two different important disturbances exist in the pressure signal. The disturbances are related to the unsteady motion of the supersonic pocket and fluctuating lift, and drag forces. Pressure wave signatures, noise frequency spectra, and noise directivity are shown.