Experiments on the Determination of Immersed Shell Structure Mobilities via Scale Modeling

Abstract

Experiments were conducted to confirm scaling relations for structural frequency response functions as applied to immersed shell structures using same-material, same-liquid scale models. Accelerance (acceleration/force) frequency response magnitude data were acquired for full-scale and half-scale versions of a fixed-free open cylinder mounted in a rigid vessel. The data confirmed that corresponding frequencies in the model and prototype were in proportion to the inverse of the geometric scale. The peak accelerance magnitudes were normalized by damping to form quantities which should scale despite differences in the corresponding modal damping values. Discrepancies in some of these normalized magnitudes coincided with angular mismatches in mode shapes attributed to minor manufacturing differences in the specimens. Thus, peak frequency responses for a prototype immersed shell structure can be estimated from scale model measurements if typical prototype damping values are known, but the locations of corresponding responses may differ between the model and the prototype in some cases.