A basic study on fluctuating aerodynamic noise radiated from longitudinal vortex in the flow field with turbulence

Abstract

Fluctuating aerodynamic noise, that is, time-varying wind noise can significantly affect driver annoyance during at high cruising speed, independent of average loudness. Causes of fluctuating aerodynamic noise include wind buffeting generated by other vehicles, and also wind gusting. Therefore, it is necessary to clarify the generation mechanism of the fluctuating aerodynamic noise generated in the turbulent flow. In the uniform flow without turbulence, our previous study has revealed the generation mechanism as well as noise sources of aerodynamic noise on the longitudinal vortex system. In the experimental and numerical study, turbulence was produced with a cylinder placed upstream of a delta wing. Main flow with periodic turbulence of Karman vortex impinged with the longitudinal vortex system generated along the leading edge of the delta wing. The study was conducted experimentally and numerically. Both the studies showed that aerodynamic noise is amplified around the frequency of shedding vortices. The numerical data was also investigated with modulation spectrum analysis. As a result, it was found that the shedding frequency is modulated to the lower frequency range related to fluctuating aerodynamic noise.