Optimal Design Of Cabin Noise Control On Multi-functional Platform-Support-Vessel

With the development of large-scale exploitation of marine resources,offshore exploitative operations have been continually expanding into the deep sea area.More and more attention has been turned to the marine industry.With various functions,Platform-Support-Vessels which are convenient to supply services to offshore engineering activities,take an active part in the offshore exploitation.Considering the needs of its functions,Platform-Support-Vessels are generally equipped with the bow thrusting propeller that facilitates the dynamic positioning.However,according to the trial result,the Platform-Support-Vessel’s cabin noise situation under the bow thrusting condition usually tends to be severe.In order to adapt the cabin noise situation to the increasingly strict industry standard,this paper is aimed to study the Platform-SupportVessel’s cabin noise under the bow thrusting condition.At present,it’s rare to see research data on the bow thruster excitation.Therefore,for the important noise source under the Platform-Support-Vessel’s bow thrusting condition,this paper uses the Computational Fluid Dynamics(CFD)method to study the propeller excitation effect on the bow thruster tunnel,which is aimed to obtain accurate excitation parameters to prepare for the noise analysis.The fluid model meshed in the ICEM software is calculated in the FLUENT software with the boundary conditions set under the condition that the bow thrusting propeller driven by the diesel engine is operated at the rated power.Through the calculation results,the distribution law of the excitation on the bow thruster tunnel is analyzed.And by the conversion of the transient results,the excitation condition for the noise calculation is ensured.Statistical Energy Analysis(SEA)method and Finite Element(FE)method are combined to predict cabin noise.And the FE-SEA coupling model of 65 m multifunctional Platform-Support-Vessel with the bow thruster tunnel is established by VA One software.Based on the ship data,empirical formulas and fluid calculation results,various important parameters for the noise calculation are determined.The accuracy of model calculation is verified by comparing the calculation results of the cabin noise with the test results.Through the vessel’s noise distribution law,it is found that sound pressure levels of the cabins are related to the position of each excitation source.Under the bow thrusting condition,except for the few cabins near the engine room,which are mostly influenced by the diesel structural excitation,for most cabins of the Superstructure,the main influencing factor of the sound pressure level is the bow thruster excitation.And the effect of the bow thruster excitation tends to be attenuated more rapidly at the higher frequency.The optimal design for cabin noise reduction is undertaken from different ways.Based on the vessel SEA model for noise prediction,the effects of noise reduction by different optimal measures are compared and analyzed.During the vessel design,considering the influence of the relative position of excitation sources to plan the use of each area can bridge the gap between the noise condition and the limit standard,which can reduce the difficulty of noise reduction by the subsequent measures.Considering the transmission path of noise energy,through reasonable vibration absorption measures,the effect of noise reduction at the corresponding cabin can be achieved.With regard to the energy transfer of the excitation source,by effectively controlling the vibration of the excitation source,the effect of reducing the overall sound pressure level at the superstructure can be achieved.