Effect Of Mass And Damping Ratios On Fiv Of Downstream Cylinder In Presence Of Upstream Stationary Cylinder

In our life,we can find applications of flow-induced vibration everywhere.For example,when air-conditioner is running,vibration and noise make terrible impacts on the life span of the machine.When aircraft flies in the air,the vibration of airfoil has an impact on the stability of the plane,which effects the passengers' safety.Therefore,the thesis mainly researches the mechanism of flow-induced vibration.Two distinct cylinders arranged in tandem are taken as the research model.The upstream cylinder is fixed while the downstream cylinder induced vibration in the cross-flow transverse direction.The topic mainly uses wind tunnel experiments,which studies a significant vibration-galloping.Adjustable mass-damping ratio is used to achieve the critical velocity corresponding to onset galloping vibration.Finally,stability map and predicting the critical velocity formula would be exhibited.In the experiment,the ratio of diameter is 0.4,the gap L which is a distance from the center of upstream stationary cylinder to the forward stagnation point of the vibrating downstream cylinder is 1.5D,and 3.5D.D and d is diameter of downstream cylinder and the upstream cylinder.m*? is mass-damping ratio.In the wind tunnel experiment,by changing the mass of the vibrating cylinder,it is proper to obtain corresponding values of damping ratio,resulting in adjustable mass damping ratio m*?.In every situation of m*?,the amplitude,frequency at every reduced velocity will be obtained at first,the critical velocity and stability map will be summarized.At static area between lock-in and galloping(desynchronization branch),a uniform initial displacement was set to get the total damping ratio.We research the relationship among the total damping ratio,m*? and critical velocity.At last,formulas of predicting the critical velocity are obtained based on those variable.