Study On The Control Of Wind Load And Flow Field Around The Main Beam Of Long-span Bridge Based On The Spread Disturbance

Vortex-induced vibration(VIV)is a kind of wind-induced vibration of Bridges,which is caused by the vortex shedding alternately at the wake.When the vortex shedding frequency is consistent with the natural vibration frequency of the main beam,the vortex-induced vibration phenomenon that may cause fatigue failure of Bridges and attached structures will occur to a limited extent.In the development of bridge structure,in order to meet the reality,the span of the main span is increasing,and the increase of span means that the stiffness of the main beam is further reduced,the VIV is more likely to occur.With the in-depth study on the spreading vortex shedding at the end of the main beam,it is found that the destruction of spreading consistency can inhibit the formation and development of vortexes and further suppress the vortex-induced vibration.In this paper,the wind load on the model surface and the control of the flow field around the model are studied in the form of spreading disturbance along the model,mainly including the following research work:From the perspective of engineering practice,and in order to better analyze t he control mechanism,components are placed separately at the front end and the tail end of the model before symmetrical arranged along the lower surface of the model.The wind load characteristics and characteristic variation rules of the main beam model under different spanwise perturbations are obtained by measuring the pressure and changing the experimental parameters.Under the condition of 0 degree wind attack Angle and positive wind attack Angle,the surface pulsation pressure coefficient of the model can be reduced by arranging the components at different positions.Under the condition of negative attack Angle,the pulsation value of the components arranged separately at the tail end is relatively unchanged without control,while the surface pulsation value of the model increases when there are components at the front end.Secondly,combined with the experimental results of PIV,the surface pressure characteristics of the superior control condition and the unfavorable control condition were verified,and the corresponding control mechanism was analyzed through the characteristics of the flow field around the flow direction and the spread direction of the two sections.Under the condition of 0 degree wind attack Angle and positive wind attack Angle,the turbulent kinetic energy of the wake field decreases,the influence of the vortex on the wall surface weakens,the correlation of wake field spread direction weakens,and the three-dimensional characteristics of the whole flow field become more obvious.At the negative Angle of attack,the element control effect disappears,and the turbulent kinetic energy on the surface of the model increases when there are elements in the front end.