Improved Acoustic Approximations for Submerged Shells

by Ranganathan Vasudevan, Asst. Civ. Engr.; New York City Transit Authority, New York, N.Y.,
Frank L. DiMaggio, (F.ASCE), Prof.; Dept. of Civ. Engrg. Mechanics, Columbia Univ., Seeley W. Mudd Building, New York, N.Y. 10027,

Serial Information: Journal of the Engineering Mechanics Division, 1981, Vol. 107, Issue 1, Pg. 39-54

Document Type: Journal Paper


Acoustic approximations are differential relations between fluid pressure and velocity used on the surface of a submerged structure to uncouple its motion from that of the fluid. Two recently proposed schemes, the Improved Doubly Asymptotic Approximation (DAA2) and the Inertial Damping Collocation Approximation (IDCA) are capable of giving exact results for one component of response at one and two intermediate frequencies, respectively, in addition to predicting correct behavior at very low and very high frequencies, as does the widely used Doubly Asymptotic Approximation (DAA). In this paper, the choice of these fitting frequencies is optimized for spherical geometry, and the predicted acoustic resistance and reactance curves are compared with each other, with exact solutions, and with those obtained earlier using the DAA.

Subject Headings: Fluid velocity | Approximation methods | Submerging | Drag (fluid dynamics) | Dynamic pressure | Underwater structures | Motion (dynamics) | Inertia

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