The Mechanism Research Of Rain-wind-induced Vibration Based On Wind-rain Two Phase Flow

Stay cable is the key part of cable-stayed bridge, and one of main factors of itsfailure is the rain-wind induced vibration. In this paper, aerodynamic parameter ofstay cable, trajectory of raindrops and variation of water film morphology under windand rain are researched by the gas-liquid coupling model build in CFX, the model ofcable build in ANSYS and using Workbench as the platform of data transfer. The mainresearch contents include:Based of Lagrange granular flow method and considering the coupling effect ofwind field and raindrops, the trajectory of raindrops in gravity field is verified at first,then the trajectory of raindrops and the effect of raindrops on wind field pulsation areresearched, and finally the variation of aerodynamic parameter under differentconditions of wind and rain is discussed. The results show that the final velocity ofraindrops in gravity field is in good agreement with that in reference. Under theinteraction of gravity and wind, the final horizontal velocity of raindrops is similar towind speed and the final vertical velocity of raindrops is similar to that without wind.There is no obvious change in wind field pulsation caused by rainfall and less changein aerodynamic parameter of stay cable under natural conditions.The transverse displacement and the aerodynamic parameter of stay cable, thewake structure and the trajectory of raindrops are researched respectively in this paperfor the first time using Lagrange granular flow method and considering the couplingeffect of wind field, raindrops and stay cable. The results show that due to the flap ofraindrops, with rainfall intensity of30mm/h stay cable reaches the amplitude oftransverse displacement faster and the amplitude is larger than that without rain. Thefrequencies of transverse displacement and lift coefficient are equal to the naturalfrequency of stay cable, which is0.952Hz.The effects of different initial water-film thickness, contact angle, wind speed,wind yaw angle and inclination of stay cable on rivulet morphology under theinteraction of gravity and wind are studied using VOF method for the first time in thispaper, which is used to verify the model with water-film in gravity field. The resultsshow that in gravity field rivulet falls along the gravity direction, which is inagreement with natural phenomena; and the simulation results of morphology ofupper rivulet and lower rivulet under the interaction of gravity and wind are consistent to that of field observation. Upper rivulet and lower rivulet are formed only whenwind speed is located in a certain region and stay cable is down inclined along winddirection.Before the model with water complementations in gravity field is verified, thevariations of rivulet morphology under the interaction of gravity and wind with twodifferent water complementations are analysed using VOF method for the first timeand formation law of rivulets with different wind speeds is compared. The resultsshow that in gravity field rivulet falls along the gravity direction periodically; upperrivulet and lower rivulet can stay on cable surface for long time with uniform watercomplementation, which is in agreement with the phenomena of field observation; forits consideration would take into account the influence of rivulet sliding along staycable, a more realistic simulation of water film morphology could be analysed usingwater complementation in the area of upper rivulet and lower rivulet; the liftfrequency of cable with water film is lower than without rain.