The Study On Transducer Arrangement Of Cylindrical Shell In Real-time Prediction Of Radiated Sound

The vibration and sound radiation are very important to the military successes ofsubmarines, while these parameters change with different operating conditions. To predict thereal-time sound radiation of submarines, transducers are usually put onto the surface of structureto measure the vibration, and then sound radiation can be obtained by numerical method. Duringthe tests, the reduction of transducers’ number is significant for saving cost when the precisionmeet the engineering need. Thus, the study on transducers arrangement has important theoreticalvalue and wide engineering application. In this dissertation, the methods of transducersarrangement and real-time sound radiation prediction have been discussed.The rules of transducer arrangement in cylinder shell are studied based on far fieldanalytical sound pressure. Firstly, the prediction error with different number of transducers inaxis direction is discussed; at the same time, in circumference direction, the relationship betweenthe number of transducers N and the modes n is deeply analyzed. Finally, a fast predictionmethod of sound pressure in the far field is discussed. The result show that the relationshipbetween the needed number of transducer M and mode m is M＝m﹢1in axis direction incritical wave number, while N＝2n﹢1in circumference direction; in far field sound pressureprediction, by taking the truncation number as N/2+1or increasing transducers’ number in axisdirection, the precision of sound prediction increases.Based on BEM and SEA theories, the appropriate number of transducers in axis andcircumference direction is studied. The appropriate number of transducers necessary forpredicting sound radiation of cylinder shell is about50, the sound power and pressure can beobtained by BEM in low frequency, while by SEA in high frequency. Further more, the influenceof transducers’ location deviation on sound power prediction has been discussed, the resultshows that slight location deviation has little influence on sound prediction, but the transducersshould not be mangled.Based on mode theory and condition number, the study on the method by which the velocitydistribution can be obtained through limited transducers is considered. Take the conditionnumber of mode shape matrix as the target function, sampling points are decreased one by onetill the least amount of transducers and their location left. The velocity distribution of the wholecylinder can be reconstructed with velocities measured by these transducers. The result showsthat the method could reconstruct vibration of cylinder well in low frequency, besides, to decrease transducers’ number, only main modes should be considered.A sound power prediction method has been discussed based on sound impedance theory.The cylinder shell have been divided into several pistons based on the transducer’s location,sound power can be predicted based on sound radiation self-impedance and mutual-impedanceof pistons. If the sizes of pistons are similar to that of meshes, the sound power and pressurepredicted by this method and BEM match each other well, compared with BEM, the givenmethod doesn’t exist singularity problem.In the end of the dissertation, the main conclusions and further work are summarized.