Aerodynamic Sound Identification of Longitudinal Vortex System

Longitudinal vortex generated around automobiles and airplanes is reproduced by a delta wing with attack angle of 15°, which was merged in the uniform flow at 10 m/s. The paper aims to clarify the sound source of the longitudinal vortex system. The beamforming technique was applied to identify the sound sources of the vortex system in the JAXA (Japan Aerospace Exploration Agency) wind tunnel. To verify the simulation model used, aerodynamic sound in the far field was compared with measured one. Estimated sound agrees quite well with measured one. To clarify aerodynamic sound generation mechanism, sound source distribution and vortex structure were numerically investigated. As a result, following findings were obtained. (1) Dominant sound source was experimentally observed by beamforming technique at the apex of the longitudinal vortex system. (2) Numerical analysis clarified sound source distributions of derivatives of surface pressure fluctuations, which were caused by the strongest unsteady motions of the vortices at the apex of the vortex system.