Franck Sgard

Finite element and boundary methods in structural acoustics and vibration

“...the analyses presented begin with well-known fundamental equations and follow a logical progression to the final solutions. ...The book provides a thorough treatment of the theory that underpins FEA and BEA as applied to the solution of vibro-acoustic problems and, as such, it is a valuable textbook for graduate students majoring in acoustics or vibration.” —Colin Hansen, past president, International Institute of Acoustics and Vibration

Effects of mean flow on the vibroacoustic behavior of a plate-backed cavity

This paper describes a general formulation allowing for the analysis of the vibroacoustic behavior of a baffled plate, acoustically or mechanically excited, immersed in a mean flow on one side and coupled to a rectangular hard-walled cavity on the other side. The analysis i s based on a finite element method for the plate vibrations. Fluid loading on each side of the plate is taken into account through an impedance matrices approach. The plate-cavity impedance matrix is calculated using a boundary element method. The amount of computation is decreased by using a two indices Greens function inside the cavity. The external impedance matrix accounting for mean flow, is calculated using an extended form of Kirchoffs integral equation and a boundary element method. A detailed discussion of mean flow effects on the different vibroacoustic indicators (mean square plate velocity, acoustic radiated power and radiation efficiency of the plate inside the cavity) is presented. Coupling mechanisms are explained in terms of added mass, stiffness and damping. Important changes occur in the vibroacoustic indicators as the Mach number increases. It is seen that the mean flow effects tend to oppose cavity effects especially at low frequencies.