Abstract
This paper describes how an unstable vortex dipole rebounded from a wall generates the sound field by 3-dimensional DNS. The unstable vortex dipole may form a chain of vortex rings because of the Crow-type instability. Small initial disturbances added to 2-dimensional vortex dipole lead to three-dimensionality. The vortex dipole changes its shape because of the Crow-type instability. When the vortex dipole is near the wall, secondary vortex is generated on the wall. The numerical results show that the sound fields generated are consists of a few waves coming from the sound source area.
