Investigation On The Fast Prediction Method Of The Underwater Noise From Ship

The radiation noise always has been the important indicator which measures the fighting capacity and survivability of the ship,which is the main detection target of passive sonar and the major interference factor of its active sonar.For the large complex structures as ship,fast prediction or real-time monitoring of radiation noise in its service period is of importance in improving the fighting capacity and survivability.Therefore,the investigation on fast prediction of radiation noise has significant theoretical value and engineering application.This paper focuses on the fast prediction of radiation noise by ship,does some theoretical and experimental work,following the principle of theoretical research combined with engineering application.Firstly,this paper deeply analyzes the transfer rule between the base's vibration,the surface's vibration and the radiation acoustic field.Then,the acoustic-vibration transfer function between the ship base's vibration and the underwater acoustic pressure has been built.The acoustic-vibration transfer function is only associated to frequency,after verified by theoretical,numerical and experimental methods.In other words,the acoustic-vibration transfer function is immutable for the specific ship.Based on the immutable characteristic of the acoustic-vibration transfer function,using the pre-computation of the acoustic-vibration transfer function,the fast prediction method of the ship radiation noise underwater under single-source exciting condition has been proposed.The numerical software takes several hours to complete the prediction for the ship noise underwater.However,the fast prediction method only takes minutes to complete it.The next,in the ship's service period,ship needs to open multiple devices,in order to maintain its operation normally.According to the superposition principle of acoustic energy,this paper only superimposes the acoustic pressure amplitude value,ignoring the phase relationship between sound waves.Based on this superposition principle of acoustic energy and the fast prediction method of the ship underwater under single source exciting condition,the fast prediction method of the ship radiation noise underwater under multi-source exciting condition has been proposed.After discussing the errors caused by ignoring the correlation between excitation sources,the project using range of the fast prediction method are given.Once more,for the present fast prediction method of the ship noise underwater under single and multi-source exciting conditions,the vibration and acoustic experimental research on underwater stiffened cylindrical shell are performed,which are carried out in six-side anechoic tank.The experiment gives the test result of the acoustic-vibration transfer function between the stiffened cylindrical shell vibration and the acoustic pressure.It verifies the immutable characteristic of the acoustic-vibration transfer function,also verifies the validity of the fast prediction method of the ship noise underwater under single and multi-source excitation conditions.Finally,based on the presented fast prediction method of the ship noise underwater,combined with the engineering practice demand for fast prediction of the ship noise underwater in the ship's service period,this paper develop the fast prediction software by MATLAB tool.The fast prediction software can be directly used to fast predict and real-time monitor the underwater noise of the ship.The investigation in this paper provides the theoretical derivation on the raw between the base's vibration,the surface's vibration and the radiation acoustic field.Based on the immutable characteristic of the acoustic-vibration transfer function,the new method is put forward to fast predict the underwater noise of the ship in its service period,which provides theoretical foundation for real-time monitoring of the ship noise in its service period.After discussing the errors caused by ignoring the correlation between excitation sources,the project using range of the fast prediction method are given.The method provides a new way to solve the fast prediction of ship underwater noise in engineering prediction.