Dynamic interaction of an eccentric multipole cylindrical radiator suspended in a fluid-filled borehole within a poroelastic formation |
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Authors: | Seyyed M Hasheminejad Amir K Miri |
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Institution: | (1) Acoustics Research Laboratory, Department of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran, 16844, Iran |
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Abstract: | Acoustic radiation and the dynamic field induced by a cylindrical source of infinite extent, undergoing angularly periodic
and axially-dependent harmonic surface vibrations, while eccentrically suspended in a fluid-filled cylindrical cavity embedded
within a fluid-saturated porous elastic formation, are analyzed in an exact manner. This configuration, which is a realistic
idealization of an acoustic logging tool suspended in a fluid-filled borehole within a permeable surrounding formation, is
of practical importance with a multitude of possible applications in seismo-acoustics. The formulation utilizes the novel
features of Biot dynamic theory of poroelasticity along with the translational addition theorem for cylindrical wave functions
to obtain a closed-form series solution. The basic dynamic field quantities such as the resistive and the reactive components
of the modal acoustic radiation impedance load on the source in addition to the radial and transverse stresses induced in
the surrounding formation by an eccentric pulsating/oscillating cylinder in a water-filled borehole within a water-saturated
Ridgefield sandstone medium are evaluated and discussed. Special attention is paid to the effects of source eccentricity,
excitation frequency, and mode of surface oscillations on the modal impedance values and the dynamic stresses. Limiting cases
are considered and good agreements with available solutions are obtained. |
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Keywords: | Acoustic radiation Eccentric source Fluid-filled cavity Permeable formation |
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