Frequency analysis of submerged cylindrical shells with the wave propagation approach

The wave propagation approach is extended to coupled frequency analysis of finite cylindrical shells submerged in a dense acoustic medium. Comparison of the results by the present method and numerical FEM/BEM has been carried out. A finite cylindrical shell enclosed with plate end-caps was modeled for coupled frequency analysis. The first eight coupled natural frequencies were obtained using SYSNOISE. These results are compared with the new method and good agreement has been found. With the new method the effects of shell parameters, m,n,h/R,L/R and boundary conditions, on the coupled frequencies are investigated. The coupled frequency curves are also u-shaped as the uncoupled frequency curves. As the circumferential mode n increases, the difference between the coupled and uncoupled frequencies reduces at small mode n, but increases after the n where the fundamental frequency is achieved. The effects of boundary conditions are significant at small mode n. Due to the coupling effects the transition of fundamental coupled frequency is earlier with the h/R ratios than that of the uncoupled case. Both the coupled and uncoupled frequencies increase with the h/R ratios, but at different rates which show the different coupling effects on the different wave modes. With the present method the calculation of coupled frequency of submerged cylindrical shells is relatively easy, quick but with good accuracy.