MEAN FLOW EFFECTS ON A PLATE-BACKED CAVITY .1. THEORY

This is part I of a paper dealing with the vibro-acoustic behavior of a baffled plate backed cavity, immersed in a mean flow. The plate is e xcited by a point force or a plane wave convected by the mean flow. Th is paper expounds the theory. The formulation is based on a finite ele ment method for both the plate and the cavity. Fluid loading due to me an flow is taken into account through an impedance matrix. This extern al impedance matrix is calculated using an extended form of the Kirchh off's integral equation together with a variational boundary element m ethod. To account for the cavity, a system of coupled equations is con structed in terms of structural displacements and acoustic pressure. T he solution CPU time is substantially reduced by using a modal expansi on in terms of the in vacuo structural modes and rigid cavity modes. T wo numerical validation are presented. Part II discusses results regar ding the effects of mean flow on the vibro-acoustic indicators of the system.