| When the ship is in actual operation,the unsteady pulse force caused by the non-uniform flow field of the stern can lead to strong propeller vibration and large propeller noise,which will seriously affect the ship performance.In order to study the vibration response characteristics of the elastic propeller in the non-uniform flow,the CFD/FEM two-way fluid structure interaction(FSI)method has been used considering the influence of the stern wake field.By summarizing the relevant research methods of propeller hydrodynamic and vibration responses,the CFD/FEM FSI numerical method combined with CFX-Transient Structural simutaion module of ANSYS＿Workbench platform is proposed for the vibration response analysis of elastic propeller in the flow field.First of all,numerical calculation methods and simulation techniques of the CFD/FEM FSI for elastic rotating structures have been summarized,including the establishment of simulation model,mesh generation method,setup technique of coupling solver and the selection of turbulence model,and the SST k-ω turbulence model is selected for flow field simulation.Then taking the MAU four-blade propeller as the object,the effect of blade elasticity on propeller performance has been studied by FSI simulation.Firstly,the dry and wet modes of propeller are simulated.The wet frequencies of propeller decrease compared with the dry,but the vibration modes are similar.In FSI simulation,the coupling hydrodynamic results of elastic propeller are closer to the test values than the rigid,which indicates that the FSI hydrodynamic prediction is more accurate.Blade elasticity has little influence on pressure distribution of blade surface,but the vibration response cannot be ignored.So,the response of blade displacement is further analyzed.Comparing the peak of response amplitude-frequency of tip displacement and the wet mode natural frequency of propeller,the propeller has large vibration response at the first natural frequency.Finally,the influence of non-uniform wake field on the vibration response of E1619seven-blade highly skewed propeller is studied.And the "cross" type wake field and "ox horn" type wake field are selected for the FSI simulation.The FSI results show that the shaft,blade frequency and their doubling frequencies of propeller’s vibration response have different amplitude characteristics due to the different types of wake field.And in addition to the correlation between blade frequency and shaft frequency,the propeller also has obvious vibration response at the lower natural frequency.Analyzing the pulse thrust of elastic and rigid propeller in "ox horn" wake field,it is found that pulse thrust of the elastic propeller has the same lowfrequency peak as the rigid except the low frequency elastic peak(the first-order natural frequency of propeller),and the low-frequency broadband force amplitude of the elastic propeller caused by unsteady turbulence is an order of magnitude higher than the rigid.The velocity distribution characteristics of the different wake field have also been analyzed,especially in the area with high velocity of tip. |
