Acoustics of spaces between axisymmetric structures

Abstract

The acoustic behavior of a fluid in the space between two axisymmetric rigid bodies has been investigated, with emphasis placed on the determination of the resonance frequencies of this space. An approximate wave equation derived for this interspace is quite similar to the Webster horn equation. Since the interspace wave equation can be solved analytically for only a few special shapes, an approximate Rayleigh-Ritz procedure is used to predict the resonance frequencies of the space. This procedure is shown to give accurate results when applied to an exponential horn, for which the exact solution to Webster's horn equation is known. It is then applied to the practical case of the interspace region in the Apollo Command Module. The resonance frequencies so predicted are in resonable agreement with measurements on a one-tenth acoustic scale model of the Apollo Command Module. [Work performed at Bolt Beranek and Newman Inc. under the sponsorship of the National Aeronautics and Space Administration.]