Abstract:

The frequency-wave-number spectrum of the vibration field of force excited, fluid-loaded cylindrical shells is a significant determinant of the shells' acoustic radiated field. This presentation discusses the procedures used and results obtained using accelerometer arrays to sample the vibrations on a number of different type shells. The arrays are formed by distributing accelerometers with uniform spacing, either along a longitudinal generator or around a circumference of the cylinder. Depending on the orientation of the accelerometers relative to the shell's midsurface, the dispersion characteristics found allow for the identification of the various wave types that exist on fluid-loaded cylindrical shells. These are the quasi-flexural waves and in-plane membrane waves, both longitudinal and shear. In an early set of measurements, made in 1986, the shell structure could be considered as unstiffened, while the other results show the effects of stiffening ribs in the frequency-wave-number plots. These effects manifest themselves as aliased quasiflexural waves. The shapes of the dispersion curves are in good agreement with numerical results arising from analytical expressions.