Numerical Analysis Of Effects Of Flow Speed On Structural Vibration And Acoustic Radiation Of Plates In Mean Flow

Prediction and control of the structural vibration and voice is an especially important subject for both civil ships and naval vessels. Underwater vibro-acoustic characteristics differ greatly from air vibro-acoustic characteristics mainly due to the loading effect of the surrounding heavy fluid. At present, most of the researches considered the vibro-acoustic characteristics under the no-flow condition, thereby, it is important theoretically and practically for prediction and control of the structural vibration and noise to study the influence of the flow speed on the vibro-acoustic characteristics of underwater structure.This paper couples the boundary element method which is based on the surface integral equation of pressure in mean flow with structural finite element method to obtain motion equation of fluid-structure interaction. An adjoint subspace iteration method is employed to calculate the eigenvalues of the fluid-structure interaction system. Numerical examples of stiffened plate and plate are involved to show the effects of flow speed on vibro-acoustic behavior in mean flow. Numerical results of structural natural frequencies show that the effects of flow speed seem generally to decrease the natural frequencies of plate. However, with increasing flow speed, the effects of flow speed may increase the natural frequencies due to fluid added stiffness. Numerical results of mean square velocity and radiated power show that more power is radiated in mean flow when compared with the no-flow case. The effects of flow speed increase the mean square velocity and radiated power, the effect on radiated power is more obvious than on velocity. The stiffness of the plates is important to these effects of flow speed on vibro-acoustic behavior. The smaller the plate's stiffness is, more significant these effects are.