Axisymmetric wave propagation in fluid-loaded cylindrical shells: Theory versus experiment

This paper discusses both theoretical and experimental aspects of axisymmetric wave propagation along fluid-loaded cylindrical shells (excluding torsional modes). For a steel cylindrical shell with a fixed ratio of inner to outer radius, four different fluid configurations are considered: water inside and outside the steel shell; air inside and outside; water inside and air outside; and air inside and water outside. Calculations of the transient pressure response for the case of an axisymmetric ring source and a point receiver are made as a function of source–receiver separation. Experimentally, a PZT ring source and ring receiver are placed around a steel cylindrical shell with an outer radius of 9.53 mm and an inner radius of 7.94 mm. Waveforms are recorded for multiple source–receiver hydrophone spacings in the frequency band 50–240 kHz. Using a Prony’s method, the complex wave number as a function of frequency for each of the modes in the system is derived from both the theoretical and experimental waveforms. These axisymmetric modes are grouped into three categories: steel modes, non-cutoff fluid modes, and cutoff fluid modes. Excellent agreement is obtained between theory and experiment.