Study On Prediction And Control Of Underwater Model Ship's Vibration And Radiation Noise

In recent years, people pay close attention to the acoustic performance of the underwater structure. Therefore, researchers increasingly focus on the prediction about the vibration and radiation noise of underwater structure and the way to reduce acoustic radiation.An underwater model ship is studied in this thesis. It is demonstrated that no resonance occurs on the model under excitation by modal simulation and excitation test. Mechanical noise of the model structure is analyzed as follows, the thesis tests the excitation source of the structure——the exciting force of the propeller, and obtains the response of the structure by the finite element method. Taking the response as the boundary condition, the method combining of finite element method and boundary element method is used to compute low frequency radiation noise of the structure under the propeller excitation. According to the excitation, the statistical energy analysis method is used to compute high frequency radiated noise. The propeller's own radiation noise is tested and demonstrated as the major noise source of the model by the experimental data compared with the simulation results.The transfer paths of the underwater model ship's radiation noise are optimized.Considering its structural form, the propeller is elastically mounted on the horizontal wing, sound-insulated and coated with damping material to decrease acoustic radiation of the underwater model ship.A test bench is putted up. Vibration and noise are tested to validate the design of decreasing radiation noise in the following three situations, "the propeller is mounted rigidly","the propeller is mounted elastically" and "the propeller is mounted elastically and coated with damping material".The thesis is instructive in analyzing the modal of the underwater structure,predicting its full-band radiation noise and designing the noise reduction measures.