Transmission loss characteristics of an annular cavity with arbitrary port locations using Green's function method.
The prediction of transmission loss characteristics of a short chamber requires the study of both longitudinal as well as transverse modes. This prompts the development of a three-dimensional (3D) transfer matrix, which can address the wave propagation in all three directions. Accordingly, an analytical methodology for transmission loss characteristics of an annular cavity using Green's function method is presented in this paper. The 3D wave equation is used to derive the mode shape functions for the cavity. The average pressure on the inlet and outlet ports is predicted using the Green's function derived from the mode shapes. Three different port location configurations of the annular cavity are considered for establishing the analytical methodology, viz., face-inlet-face-outlet (FIFO), side-inlet-side-outlet (SISO), and face-inlet-side-outlet (FISO). Numerical model results are used to corroborate the analytical results. The effects of geometrical parameters on the transmission loss are studied.
FORMULATION OF FOUR POLES OF THREE-DIMENSIONAL ACOUSTIC SYSTEMS FROM PRESSURE RESPONSE FUNCTIONS WITH SPECIAL ATTENTION TO SOURCE MODELLING
Abstract The procedure proposed by Kim, who is also one of the authors of this paper, and Soedel (Journal of Sound and Vibration129,237–254) for formulation of four-pole parameters of three-dimensional cavities is revised. In the procedure, four poles were formulated in terms of the pressure responses of the cavities to a point source. However, it is shown that using the point source model for such a purpose may not always be valid because the pressure response function becomes singular at the source point in such a case. In this work, the procedure is modified by employing the surface source model and a new definition of the input impedance. It is shown that the modified procedure can be applied to three-dimensional acoustic systems. Also, an interesting concept of using a sub-system composed of the cavity and a pair of short pipes is suggested for more accurate analysis.
Pump-induced acoustic pressure distribution in an annular cavity bounded by rigid walls
Abstract This paper describes an analytical method for estimating the coolant pump-induced acoustic pressure distribution in the inlet annulus of a pressurized water reactor. To simplify the problem, flow velocity is ignored and the walls bounding the annular cavity are assumed to be rigid. The phenomenon of beating due to slight differences in the pump blade passing frequencies is included in this analysis. An experiment based on a simple laboratory model is carried out to verify the theory, small loudspeakers being used to simulate the pumps and air as the fluid medium. Agreement between theory and measurement is good.