Analytical sound pressure expression of vortices near a ground surface

Abstract

In this work, an analytical expression is sought for the sound pressure of aircraft wake vortices near a ground surface. The analytical basis for the mechanisms of aircraft vortex sound generation follows the vortex dynamic models and vortex sound theory. The theory focuses on acoustic signatures of the vortex created from subsonic flow. Vortex acoustic signature from a ground can mainly be characterized based on the boundary condition and transition of the flow moving away from the ground. Of interest is acoustic characterization of wake vortices in ground effect. To this end, the method of images was used to simulate the presence of the ground. The method of images assures that the vorticity is mirrored about the ground plane that contributes to the modified amplitude above the ground. The extension of the presented approach to model the turbulent flow in the ground effect will also be highlighted.