Prediction Of Low-frequency Sound Radiation From Submerged Cylindrical Shell Based On Dominant Modes

At present,various types of underwater vehicles are widely used in national defense,marine development,and other fields.They have received more and more attention from various countries.In order to evaluate its performance,it is necessary to conduct real-time and rapid monitoring of the noise of the underwater vehicle.Currently,the commonly used method for predicting the radiated sound of underwater structures is to make predictions by monitoring the vibration of the structure.In order to facilitate engineering applications,how to effectively reduce the number of measurement points used in prediction and improve the efficiency of sound radiation prediction is a problem worthy of study.For this reason,this paper firstly proposes a method for rapid prediction of low-frequency acoustic radiation based on the decomposition of cylindrical shell surface displacement.Firstly,the vibration mode of the cylindrical shell is calculated and analyzed,and then the cylindrical shell model is tried to calculate the radiated sound power contributed by each mode at this time.The results can show that there are some modes play a major role in the total sound radiation power of the cylindrical shell in different frequency bands,and these modes can be called dominantly radiated structural modes.Then the method of obtaining the modal displacement participation coefficient is studied.Two methods are given to obtain the participation coefficient of the dominantly radiated structural modes and their adaptation conditions are explained.It is verified that only a small number of measuring points are needed to predict the modal participation coefficient accurately.Then,simulation calculations were performed on different models.The number of measuring points required for forecasting was indicated.Research shows that this method can predict the low-frequency acoustic radiation power of underwater cylindrical shells well in different boundaries and different environments.In addition,compared with the boundary element method,this method can reduce the number of measurement points required.An acoustic radiation prediction method using surface sound pressure decomposition is also proposed,so that fewer measurement points will be required to predict acoustic radiation in the frequency band below the first resonance peak.Similarly,using the vibration mode of the cylindrical shell in vacuum as a set of orthogonal basis,the second method is used to calculate the modal contribution of each low-order mode.There is a dominantly radiated structural mode at the lowest frequency band.Studies have shown that the second method requires fewer measurement points than the first method when forecasting at the lowest frequency band.Then the same simulation analysis was performed on different models.The results showed that,compared with other traditional methods,this method can effectively reduce the number of measurement points required by decomposing the sound pressure.According to the simulation results,a low-frequency sound radiation prediction method test is designed.The results verifies the feasibility of the sound radiation prediction method proposed in this paper and the effect of a limited area on vibration and sound radiation.