The Research On Effects Of Fluid-Structure Interaction On Acoustic Radiation Of Underwater Structure

Most studies of fluid-structure interaction problems focus on the field of airborne andelastic, rarely relevant to underwater structure and water coupling problems. Fluid-structureinteraction can cause great dynamic instability of the structure in flowing water, and thestructure dynamic response will greatly changed. Consequently, the fluid-structureinteraction has a great impact on the radiation noise of the underwater structure. Therefore,the study of fluid-structure interaction about underwater structure has great significance ingrasp the coupling of vibration and the mechanism of radiation noiseThis paper takes scale model for the study of the sail of the submarine. Firstly, usingthe computational fluid dynamics software to simulate the flow characteristics oftwo-dimensional and investigate the mean pressure of the surface and the flow field aroundthe model. Secondly, study effects of the thickness, stiffened and fluid-structure interactionon the model respectively, then calculate the acoustic radiation power of the model underthe point forces in different model thickness, the location of the forces, stiffened, as well asfluid-structure interaction.Flow noise generated by the water flowing through underwater vehicle, inspiring andradiating from the surface fluctuation pressure and the disturbance in the turbulent boundarylayer. Therefore, extracts the surface fluctuation pressure of the model and turbulence noisesource by ACTRAN, and calculate the turbulence noise as well as the radiation noise of themodel. This approach make us can study the radiation acoustic power of model innon-harmonic force. Finally, use the reverberation chamber method to accomplish themeasurement of the radiated acoustic power of the shell model in blown-down water tunnel.The following conclusions can be obtained through simulation and experimentalmeasurements: the fluid-structure coupling between the water and the model make themodel’s nature modal frequency offset to low-frequency. This offset strengthens the model’svibration in the low frequency, thus increasing the radiation noise in the correspondingfrequency range. The radiated acoustic power decreased with the model’s thicknessincreasing. There are about5-10dB decrees when the model’s thickness increased from1to2millimeter at the frequency of2kHz-8kHz. With flow velocity increased the radiatedacoustic power increased. When flow velocity increased from6to9m/s, the radiatedacoustic power have a10-13dB increase, with a great fluctuation at the frequency of2kHz-6kHz and fewer at the frequency of6kHz-20kHz. There are about2-3dB decrease with a stiffener in the model compared with no stiffener in the model at the frequency of2kHz-6kHz. The rudder installed outer the model have a great effect on the radiatedacoustic power at the intermediate frequency, with a5-7dB decrease at the frequency of6kHz-14kHz. In a nutshell, flow velocity have greatest effect on the radiated acoustic power,while the stiffener have slightest effect, compared with install stiffener in the model orinstall rudder outer the model.