Ship Underwater Radiation Noise Prediction Method And Experimental Research

The hull will vibrate under the excitation of the power equipments.The hull vibration will cause the surrounding fluid to vibrate to produce the underwater radiation noise,on the other hand the hull vibration will cause the cabin noise in the form of structural sound.For military ships,predicting underwater acoustic radiation at the design stage can estimated the stealth performance of ships and provide the basis for subsequent vibration and noise reduction design.At the same time,it is of great practical significance to carry out the prediction of cabin noise and design of noise reduction in the design stage,it can improve the quality of shipbuilding and reduce the cost of shipbuilding.In this paper,a type of oil tanker is taken as the research object,the oil tanker underwater acoustic radiation forecast and the forecast of the cabin noise of the whole frequency band are realized by different numerical calculation methods,at the same time,this article carried out real-vessel measurement of tanker vibration and cabin noise.At the end of this paper,the application of the SEA in the calculation of the acoustic vibration response in the middle frequency is explorated.The research work in this paper includes:(1)The finite element model of the oil tanker and the surrounding fluid is established and the hull vibration wet mode is calculated.The calculated value of the hull vibration mode is in good agreement with the estimated value.The harmonic response of the tanker is analyzed and compared with the real ship vibration test results.The results show that the simulation values of hull vibration can be well fitted with the measured values.On this basis,the underwater vibration characteristics of hull are analyzed.(2)The underwater radiated noise of oil tanker is calculated by FE-BEM,FE-IFEM and FE-AML respectively in the middle and low frequency.The paper compares the results of three different numerical calculation methods for the whole ship's vibro-acoustic calculations.The results show that the calculated sound power and field points radiation sound pressure of above three different methods get better consistency.The statistical energy method is used to calculate the hull vibration and underwater acoustic radiation in the high frequency.In this paper,the underwater radiated noise calculation and acoustic radiation characteristics of oil tanker have been realized in the whole frequency finally.(3)The models of oil tanker cabin noise prediction for low frequency,medium frequency and high frequency are established.The cabin noise prediction of oil tanker is achieved by FE,FE-SEA and SEA respectively in the whole frequency and compared with the measured values.The results show that the prediction value of cabin noise is in good agreement with the measured value.The maximum error between simulation value and measured value of each cabin noise is 5.801 dB,the remaining errors are all within 3dB.The cabin noise forecast methods have good reliability and accuracy.From the perspective of sound absorption,the cabin noise reduction is studied,the different optimization algorithms is used to achieve a variety of sound-absorbing material combinations of acoustic optimization design.(4)Based on the PIM method,the equivalent coupling loss factor between structures is calculated,and the equivalent coupling loss factor is substituted into the statistical energy balance equation to calculate the vibration response of the structure in the mid-frequency region.The results are compared with the FE calculated results,and the two calculated results obtain a good match.The coupling loss factor between structure and acoustic cavity is calculated by structural acoustic radiation efficiency,which is substituted into the statistical energy balance equation of the actual acoustic model to calculate the structural sound insulation quantity.The calculated values of the modified statistical energy method are in good agreement with the experimental values.