Sound radiation from a water-filled pipe, radiation into light fluid.

This paper is concerned with the sound radiation from a water-filled exhaust pipe. The pipe opening and a plate attached to it form a vibrating surface for this radiation. Fluid-structural coupling between the pipe and enclosed fluid is included in the system modeling, but light fluid assumption is used for sound radiation into the space above the vibrating surface. In this paper, a numerical study on the n = 0 mode in the pipe shows that the wave types associated with this mode have different characteristics in two regions of the nondimensional frequency omega. In the first region of 0<omega<0.5 and 1<omega<1.3, the fluid and structural waves are weakly coupled, and the fluid and structural response of the pipe is governed by the resonance of each wave type. The fluid and structural waves are strongly coupled in the second region (0.5<omega<1). Simple correlation between the pipe response and uncoupled mode distributions does not exist. Significant contribution of multiple wave-types to the model energy is evident. The ultimate goal of our system modeling is to illustrate the contribution of all wave types (structural-borne and water-borne waves of the system) to sound radiation from the pipe opening and the attached plate. This paper also demonstrates the effect of these waves and their coupling in the water-filled pipe and across the plate and pipe boundary on the radiated sound pressure. Experimental results obtained in a semi-anechoic room are used to partially validate the theoretical and numerical predictions.