Influence Of Ground Effect On Flutter Performance Of Bridge With Near Streamline Section

In the existing wind engineering research,scholars at home and abroad mainly focus on the static wind stability,vortex-induced resonance and flutter stability of bridge structures.However,some of the existing bridges are close to the water surface or the ground.Now,the research on the ground effect is mainly on the aircraft wing.When the water surface or the ground is close to the bridge structure,the aerodynamic performance of the structure will be different.Once the bridge flutter occurs,it will cause irreversible damage to the structure.Therefore,it is of practical significance to study and analyze the influence of ground effect on the wind-induced flutter of the bridge and propose a reasonable aerodynamic optimization scheme.In this paper,the static aerodynamic performance and flutter stability of common sections with ground effects will be studied by numerical simulation:(1)In this paper,CFD numerical simulation method is used to obtain the static threecomponent force coefficient of the section and summarize its change law with the height from the ground.The research shows that the drag coefficient is more affected than the lift coefficient and the lift moment coefficient,especially under the high angle of attack,the lower the altitude from the ground,the higher the drag coefficient,and will slightly affect the lift coefficient and the lift moment coefficient.When the height above the ground is reduced,the section forms a narrow "channel" on the ground,which compresses and blocks the airflow flowing through it,making the section pressure separation different from the situation far from the ground.(2)At+3 ° wind angle of attack,the existence of ground effect has a significant impact on the flutter stability of the near-streamlined section.Through the simulation of the whole process of flutter by the free vibration method and the analysis of its flow field and displacement changes,it is found that the ground effect makes the negative pressure and positive pressure of the section increase in varying degrees,which leads to the reduction of the flutter critical wind speed;Through the forced vibration method to identify the aerodynamic derivatives,it is found that the flutter aerodynamic force has phase difference with the vertical displacement and torsional displacement.If the phase difference causes the self-excited force to produce positive work on the structure,the vibration amplitude will gradually increase and flutter will occur.(3)When considering the ground effect,properly reducing the angle of the inclined web or setting the central stabilizer plate can effectively improve the flutter stability performance;The flutter critical wind speed increases with the increase of the height of the stabilizer plate,until the optimal height is reached,the flutter critical wind speed decreases from the optimal value.The principle is that the installation of the central stabilizer plate is beneficial to improve the participation of vertical aerodynamic forces and inhibit the torsional movement.