Zhongguo Jianchuan Yanjiu (Dec 2019)

Prediction on hull vibration and underwater noise radiation based on modified LMM

  • Jiang Chaojun,
  • Xiang Yang,
  • He Peng,
  • Zhang Bo

DOI
https://doi.org/10.19693/j.issn.1673-3185.01557
Journal volume & issue
Vol. 14, no. 6
pp. 172 – 179

Abstract

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[Objectives] Large Mass Method (LMM) is capable to approximately convert excitation acceleration of equipments' seat into force loads,which is a common method for structural vibration response and acoustic radiation simulation analysis. In order to improve the accuracy of LMM applied in ship's noise & vibration response computation,a modified LMM(M-LMM)is presented.[Methods] Its application principles in hull structure response were analyzed, based on which the appropriate large mass ratio ensuring the application precision of LMM was obtained. Rayleigh damping was then taken into consideration,and LMM was modified with ratio coefficient. The experiment comparing results from original LMM as well as M-LMM with tested ones,together with the computations of underwater noise radiation power and vertical directivity pattern of sound field,were followed.[Results] For the frequency range of 20 Hz-200 Hz,the analysis results got from M-LMM were closer to measured values compared to that from LMM although their computed vibration response spectrums were roughly similar.[Conclusions] It is crystal clear that M-LMM can guarantee a simulation of main hull response with higher accuracy(average deviation 2.7%),providing the pre-design stage of vessels with more necessary information.

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