Effect Of Different Excitations On The Sound And Vibration Characteristics Of Cylindrical Shells

Underwater vehicles get more and more widely used in many countries. They can notonly complete the reconnaissance and attack on the enemy ships or submarines, but also canbe used to the marine science research, exploration and scientific detection. However, withthe high development of modern science and technology, the development and optimizationof underwater vehicles have been paid more attention to by more and more countries.Especially in military, the stealth performance of the underwater vehicles is the mostimportant condition for playing their fighting functions. So how to reduce the vibration andnoise of underwater vehicles have always been the hot topics for the scholars inside andabroad. Structural noise as the main noise sources of underwater vehicles has become thefocus problem of most scholars. Structural noise is caused by the unbalanced force or torquewhich is generated by the running power units, so the research on effect of external excitationon sound and vibration characteristics of underwater vehicles is of very importantsignificance.In this paper, the effect of different excitations on the sound and vibration characteristicsby the established models has been investigated. First, a cone–cylinder shell model has beenbuilt, and the vibration equation of the whole model has been obtained by using the methodsof limit assumption and transfer matrix. After modal frequencies of the model is calculatedusing MATLAB software programming, the numerical calculation results have beencompared with the calculated results of FEM simulation in order to verify the correctness ofthe method. Secondly, the vibration equation and acoustic radiation power of the modelexcited by different force and torque have been derived or calculated. Then FEM model ofaxisymmetrical shell and non-axisymmetrical shell have been built by using FEM codeANSYS. The effect law of different excitations on sound and vibration characteristics of themodel, the relationship between structural parameters and the sound and vibrationcharacteristics, and the effect law between the location of the excitation and the sound andvibration characteristics have been calculated and analyzed by using SYSNOISE. The results have showed that, comparing with other excitations, the axial moment excitation has thegreatest effect on the sound and vibration characteristics. As the shell thickness of the modelincreases the sound and vibration characteristics have effectively been reduced. Increasing thestiffeners number of axisymmetric model and changing the section sharp of non-axisymmetricmodel make the sound and vibration characteristics complicated. Excitation position in themiddle of the model makes acoustic radiation power higher than the excitation position closeto the both sides of the model.The purpose of this paper is to discover the effect law of the different excitations on thesound and vibration characteristics of shell model, and provide some reference for thestructural design and the power unit arrangement of underwater vehicles, and then providebasis and guidance for the reduction of the vibration and noise from underwater vehicles.