During the interaction between a convecting vortical flow and an elliptic body, the flow field around the body become unsteady and the acoustic wave is generated due to the unsteady flow field. The unsteady surface pressure is calculated in two-dimensional incompressible and inviscid flow and the acoustic pressure is obtained at the far field. The vorticity field is initially modeled by the Rankine type multiple vortices (vortex cloud) which are free to move. And the body surface is represented by source panels satisfying the Neumann boundary condition. When the vortices approach close to the ellipse surface, the panels are redistributed adaptively to calculate the unsteady flow field due to the vortex flow more accurately. The adaptive panel method also shows good results for the regions having large gradients such as the leading and trailing edges.
The surface pressure distribution is obtained from the unsteady Bernoulli equation which has the quasi-steady and the unsteady pressure terms. The far field acoustic pressure is calculated with acoustic dipole sources distribution on the surface. The strengths of the dipole sources are obtained from the unsteady surface pressure fluctuation.
It turns out that the unsteady pressure term dominates the quasi-steady term in the acoustic pressure. Also the normal component of the pressure to the free stream direction and the potential variation on the surface due to the source panels dominates the horizontal component and the potential variation due to the vortex flow respectively. Finally the strong acoustic pressures are generated when the vortex flow passes near the leading and trailing edges of the body. This indicates that the acoustic pressure from the two edges can be obtained almost independently.
