The far-field sound radiation behavior of a circular cylindrical shell submerged at finite depth from the free surface is studied. Based on the Flügge shell theory and the Helmholtz equation, the structure-acoustic coupling equation is established. An image method is applied so that the sound boundary condition of the free surface can be satisfied. Analytical expression of the far-field sound pressure is obtained using the stationary phase method and the Graf's addition theorem. In order to evaluate the effect of the submerged depth on sound radiation, the results of the submerged cylindrical shell at finite depth from the free surface are compared with those of the submerged cylindrical shell in the infinite fluid. The characteristics of the far-field sound pressure with the change of the depth are investigated. It is found that the submerged depth has a significant influence on the far-field sound pressure radiated from the submerged cylindrical shell due to the free surface effects. The work provides more understanding on the sound radiation properties of the submerged circular cylindrical shell without assuming infinite fluid field, which was commonly used in previous studies.
A sound–structure interaction model is established to study the vibroacoustic characteristics of a semisubmerged cylindrical shell using the wave propagation approach (WPA). The fluid free surface effect is taken into account by satisfying the sound pressure release condition. Then, the far-field sound pressure is predicted with shell's vibration response using the stationary phase method. Modal coupling effect arises due to the presence of the fluid free surface. New approaches are proposed to handle this problem, i.e., diagonal coupling acoustic radiation model (DCARM) and column coupling acoustic radiation model (CCARM). New approaches are proved to be able to deal with the modal coupling problem efficiently with a good accuracy at a significantly reduced computational cost. Numerical results also indicate that the sound radiation characteristics of a semisubmerged cylindrical shell are quite different from those from the shell fully submerged in fluid. But the far-field sound pressure of a semisubmerged shell fluctuates around that from the shell ideally submerged in fluid. These new approaches can also be used to study the vibroacoustic problems of cylindrical shells partially coupled with fluid.
In this work, a new approach is developed for predicting the vibro-acoustic characteristics of a semi-submerged cylindrical shell on the basis of the Fl gge shell theory and sound-structure coupling theory. The effect of fluid free surface is taken into account by satisfying the sound pressure release boundary condition. The wave propagation method is utilized to derive the sound-structure coupling equation. Modal coupling phenomenon is noted due to the existence of fluid free surface. A new approach, diagonal coupling acoustic radiation model (DCAAM), is put forward to deal with the modal coupling effect. Then, the far-field sound pressure is predicted by making use of the stationary image method and structural vibration response. The results from DCAAM is compared with recent works. It's verified that the new approach, DCAAM, has good accuracy and costs less time. DCARM can also be applied to study the vibroacoustic characteristics of a partially immersed cylindrical shell.
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