TY - JOUR

T1 - Acoustic radiation from a finite-length shell with non-axisymmetric substructures using a surface variational principle

AU - Choi, S. H.

AU - Igusa, T.

AU - Achenbach, J. D.

N1 - Funding Information:
This research was supported by the Of_ce of Naval Research under contract No[ 80!J!0879 whose support is gratefully acknowledged[

PY - 1996/10/31

Y1 - 1996/10/31

N2 - A modal-based method is developed to analyze the acoustic radiation of axisymmetric submerged shells of finite length with non-axisymmetric internal substructures, subjected to time-harmonic loads. In this method, a variational principle is used to derive impedance relations between the surface pressure and the surface velocity of the shell. These impedance relations are combined with the structural equations of motions based on a Lagrange energy formulation to form a complete set of equations for the fluid-structure interaction problem. Fourier series expansions are used to represent the circumferential dependence of the surface pressure and velocity. The method is demonstrated for two different configurations of substructures: circular ribs supporting length-wise beams and a spatially and modally dense array of oscillators. Since the substructures couple the circumferential modes, a large system of equations must be inverted. A matrix decomposition technique is used to reduce the size of the system of equations of the first example. For the second example, the asymptotic limit for an infinite number of substructures is developed using an integral form for the substructure impedance. It is shown that the Monte Carlo simulations for the oscillator substructures converge to the asymptotic results. It is also shown that, below the ring frequency, oscillators can induce damping that is more effective in reducing far-field radiation than high loss factors in the shell.

AB - A modal-based method is developed to analyze the acoustic radiation of axisymmetric submerged shells of finite length with non-axisymmetric internal substructures, subjected to time-harmonic loads. In this method, a variational principle is used to derive impedance relations between the surface pressure and the surface velocity of the shell. These impedance relations are combined with the structural equations of motions based on a Lagrange energy formulation to form a complete set of equations for the fluid-structure interaction problem. Fourier series expansions are used to represent the circumferential dependence of the surface pressure and velocity. The method is demonstrated for two different configurations of substructures: circular ribs supporting length-wise beams and a spatially and modally dense array of oscillators. Since the substructures couple the circumferential modes, a large system of equations must be inverted. A matrix decomposition technique is used to reduce the size of the system of equations of the first example. For the second example, the asymptotic limit for an infinite number of substructures is developed using an integral form for the substructure impedance. It is shown that the Monte Carlo simulations for the oscillator substructures converge to the asymptotic results. It is also shown that, below the ring frequency, oscillators can induce damping that is more effective in reducing far-field radiation than high loss factors in the shell.

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U2 - 10.1006/jsvi.1996.0535

DO - 10.1006/jsvi.1996.0535

M3 - Article

AN - SCOPUS:0030260138

VL - 197

SP - 329

EP - 350

JO - Journal of Sound and Vibration

JF - Journal of Sound and Vibration

SN - 0022-460X

IS - 3

ER -