Analysis Of The Influence Of Water-film Morphology On The Phenomenon Of Rain-wind Induced Vibration Of Stay Cable

Rain-wind induced vibration(RWIV)is a large amplitude vibration of cables of cable-stayed bridges under the effect of wind and rain,and will induce accumulating of damage,attenuating of bearing capacity and even an emergent accident.Because RWIV is a problem of coupling oscillation of gas,liquid and solid,whose generation environment is very complex and influencing effect is changeable,its mechanism is still unclear so far.The study in the past suggests that the formation and oscillation of the upper rivulets on the surface of cables plays a significant role in RWIV.With lubrication theory and computational fluid dynamics(CFD)method combined,a finite element model was built to simulate RWIV.Through investigating the mutual influence among water film evolution,lift and vibration of cable,the mechanism of RWIV were analysed.The main research contents include:Combining Navier-Stokes equations,CFD technology and lubrication theory,a water film evolution equation was built considering the influence of wind pressure coefficient and friction coefficient of water film around stay cable.Using d'Alambert principle and considing cable damping,cable vibration equation was established.Based on the RNAS theory and Spalart-Allmaras turbulence flow model,a finite element model was built by COMSOL software to simulate RWIV and compared with the existing experimental results.On this basis,the time,location,height and width of the initial formation of upper rivulets at different wind speed,wind yaw angle and cable's inclination angle were studied Besides,the effects of the three factors mentioned above were analyzed,which could provide the basis for design of wind tunnel tests scheme,mechanism analysis of RWIV and windresistant design of stayed cable..Based on the calculation parameters mentioned above,the evolution of upper rivulets are studied at different speeds.The schedule of aerodynamic lift and frequency value obtained from modle is applied to cable vibration equation to calculate cable vibration response at different speeds.Through investigating the mutual influence among water film evolution,lift and vibration of cable,the mechanism of RWIV were analyzed.Similar to experimental results,the computing results showed that,the resonance among upper rivulet,lift and cable a significant motivating factors RWIV.