A Study On Vibro-acoustics Analysis Of Liquid-filled Pipeline On Ships And Optimization Of Hybrid Damping Materials

Nowadays, the main problem of vibration and noise reduction in ships isvibration and noise analysis of liquid-filled pipeline systems in full frequency domain(1~10KHz), which belongs to multi-physics problems involving fluid mechanics,structural dynamics and acoustics. Solution technology for these coupling equations isnot well developed, and main difficulties in solving focus on two aspects:determination of magnitudes of transient hydraulic sources like water hammer andsurge, which can be obtained with computational fluid mechanics method but the costof computation is rather high, and the establishment of fluid-structure couplingnumerical models suitable for the whole frequency domain. In the first part of thispaper, an integrated method is studied for vibroacoustic analysis of liquid-filledpipeline. Firstly, magnitudes of hydraulic transient pressures are evaluated accordingto empirical formulas, and there follows an introduction to acoustic-structure couplingmodels without high computation costs. Then, characteristics of construction ofpipeline models with vibroacoustic analysis in full spectrum are investigated.Computational results of modal density show that the pipeline vibroacoustic modelsfor full frequency domain should be constructed with the FE and FE-SEA hybridmethods, while the use of either FEM or SEA method can not meet the requirements.Finally, given damping materials are attached to pipelines for meeting the engineeringrequirement of vibration and noise reduction, and the evaluation results on vibrationvelocity levels and sound pressure levels in pipeline system before/after theattachments of different damping materials are calculated.Damping materials are widely applied in vibration and noise reduction ofengineering structures for their high energy absorption characteristic. However, thedevelopment of new damping materials is hard, with a high price of money and time,so a more feasible way is to make maximum use of existing damping materials. In thesecond part of this paper, the optimization design of the thickness and topologicaldistribution of damping materials in the surface of structures is done, in order to makefull use of these damping materials, in which the use of damping materials is the lestunder the premise of meeting a certain requirement of vibration and noise reduction.Then, new hybrid damping materials, like the gradient damping materials, aredeveloped through different combinations of existing damping materials. Finally, thedesign models of hybrid damping materials are established, and the design methods are given, which turn out to have a good practicable value in engineering according tocomputation results.