Predictive approaches and measurements of far-field radiation from submerged partially coated (compliant layer) cylindrical shells

• Published in: The Journal of the Acoustical Society of America 2000-11, Vol.108 (5_Supplement), p.2625-2625
• Main Authors: Herdic, Peter C., Houston, Brian H., Photiadis, Douglas M., Williams, Earl G.
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4743771

In-water laboratory experiments involving spatially dense near-field and far-field responses (ka=1 to 20) are reported for a number of point driven cylindrical shells with varying amounts of compliant material attached to the exterior. The first framed shell has a square opening in the otherwise fully coated surface. Two modeling approaches are employed to predict the far-field radiation from this opening. The first method is based on the Helmholtz Integral Equation (HIE), using a simple baffled plate model where only surface quantities around the opening are projected. A square piston in a cylindrical baffle is also implemented as a second predictive approach. The predictions are found to be in general agreement with the actual radiated values determined through holographic projections to recover the off-board quantities. The discussion includes the conditions necessary for an accurate model. Additionally, two shells with different levels of interior structural complexity are each investigated using near-field acoustic holography (NAH) where the degree of compliant material coverage is varied. The physics of these systems will be discussed, including the nature of the normal modes, the energetics, and the degree to which interesting phenomena such as ‘‘tunneling’’ are observed.