We applied a novel sensing and data processing technique to analyze the water-interaction dynamics of a thin-walled aluminum beam filled with micro-structured material. The spatial impulse response is sensed at three spatial points in the form of ensembles of collocated acceleration signals. Processed by the powerful POD Transforms, the modal-like decomposition of collocated acceleration signals provides interesting insight on the nature of impulse-induced vibrations of this complex structure-water system. When not interacting with water, the point impulse excited structure vibrates in a dominant POD mode with energy-transfer wave form characteristics. When interacting with water, the point impulse excited structure vibrates in two POD modes. One POD mode is vibration while the other one is rigid-flexible body motion. The POD modes capture characteristics of interactions between flexible body (vibration-wave) and rigid body motions. This modal identification technique is potentially useful for reduced model identification and parameter estimation of hard to model complex structural-fluid interacting systems encountered in aerospace and ocean environments.
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