Title: Scattering of evanescent pipe modes form elastic spherical objects external to a fluid-filled, submerged cylindrical waveguide.
Abstract: Investigation into the interaction of low-frequency fluid-borne, radially decaying pipe modes with elastic objects exterior to a cylindrical waveguide using the elastodynamic finite integration technique (EFIT). The system is an oil-filled steel pipe submerged in water. When the sound speed of the conveyed fluid is lower than the exterior fluid, there exist fluid/fluid modes possessing cutoff frequencies supported by both the interior and exterior fluids. These are in addition to the higher-velocity, steel-borne modes, and the low-velocity internal-fluid-borne mode without a cutoff frequency. Excitation of a fluid/fluid mode near its cutoff frequency results in its further penetration into the exterior fluid. An object close to the pipe wall allows for scattering of this evanescent mode. An advantage of EFIT, direct manipulation of material properties, allows for easy inclusion of objects. Simulation results show the scattering from elastic objects with and without air pockets that are compared to analytical plane wave solutions. A plastic sphere with a radius ¾ the pipe inner radius gives a backscattered signal 15 dB below and a forward scattering signal 10 dB below the incident field. In order to achieve mode separation over shorter propagation distances, the analytical mode solution is used for single mode excitation.
Publication Year: 2010
Publication Date: 2010-10-01
Language: en
Type: article
Indexed In: ['crossref']
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