Study On Traveling Wave Wall Control Method Of Flow Around The Three-dimensional Cylinder And Vortex Induced Vibration

As one of the simplest models of bluff body flow,the flow around circular cylinder has been one of the basic research objects of computational fluid dynamics because of its simple section form and the location of separation point.On the other hand,aerodynamic optimization of bluff bodies for controlling their wind-induced vibration has wide practical engineering application.Circular cylinder is a normal section in bridge engineering,ocean engineering,and other areas,such as some Suspension cable,pipeline and so on.When the fluid flows around the bluff body,there are vortexes in its wake which are the source of the aerodynamic forces acting on the body.When the force frequency approach the natural frequency of the structure,vortex-induced vibration with large amplitudes will occur.This should be avoided in some important structures,such as high-rise buildings,suspension cables for large span bridges,marine risers,and subsea pipelines.The long-term effects of fluid-induced vibration may lead to reduction in the service life of the equipment and even damage due to the occurrence of vortex-induced resonance.Therefore,it is great significance to suppress the oscillating wake of bluff body and eliminate the vortex-induced vibration.This paper,through an analysis on 3-dimensionally numerical simulation on a circular cylinder with the traveling wave wall(TWW),claims that shape control by a traveling wave wall(TWW)method can successfully manipulate the vortex shedding from a fixed circular cylinder based on a three dimensional CFD numerical simulation.In the present paper,the large-eddy simulation(LES)technique was employed to predict flow past a circular cylinder at subcritical Reynolds number of 4×10~4 and to provide images based on flow visualization which can expound the further physical mechanism responsible for these outcomes.The dynamic mesh technique was taken to generate the traveling waves.The effectiveness of the different wave velocities,wave amplitudes,and wave number on the oscillating wake of the square cylinder was analysed to evaluate the control effectiveness of the TWW flow control method.On the other hand,the paper analyzed the control effect of traveling wave wall on vortex-induced vibration by simulating the flow around the three dimensional cylinder through the comparison a group of data about the cylindrical flow with and without TWW.In addition,the mechanism of traveling wave wall control is analyzed from the perspectives of the three dimensional flow field,vorticity flow,vorticity flux and so on.The results show that the TWW can remarkably decrease the average value of the drag coefficient and alternating vortices behind the cylinder can be effectively eliminated under the control of TWW.The main research points are:LES model has been used in the three dimensional flow field,flow around cylinder and calculation results compared with previous experimental and calculated results,which fully demonstrated the validity of numerical simulation.And also observed the development of the three dimensional flow field of cylindrical wake.These foundational works paved for the following calculation and analysis of the traveling wave wall flow around cylinder.Through the secondary development of Fluent by UDF,three-dimensional travelling wave wall motion was achieved.And the study on the influence of main parameters of travelling wave wall on the control effect was completed,which includes the travelling wave amplitude,travelling wave number and travelling wave velocity,and the optimal parameter combination was obtained through analysis.The numerical model of flow vibration around a single-degree-of-freedom cylinder was established.On the other way,and the numerical simulation of the motion caused by the aerodynamic force from the flow field was completed.In addition,the control of flow oscillations behind the circular cylinder is studied under the optimal combination of parameters about the traveling waving wall.Based on the three-dimensional flow field,the mechanism of the active control of the traveling-wave wall is further analyzed,and the analysis of the three-dimensional flow characteristics,axial vortices,axial velocity,boundary vorticity flux and enstrophy of the active control of traveling-wave wall is completed.