Investigations On The Influence Of Trailing Edge Flow On Flutter Of Bridge

The flutter of bridges,as a devastating wind disaster,must be completely avoided during the bridge construction and operation phases.Under the current dual effects of increasing bridge span requirements and severe wind environment,the construction of modern bridges has put forward higher requirements on the flutter stability of the bridge.To obtain the bridge section that has higher flutter stability,The mechanism of fluid-structure coupling of the flutter large-span bridges must be more fully grasped.Under this background,this paper carried out the research on the flutter mechanism of the bridge based on the flow characteristics.Two methods,active control and passive control,are used to control the wake flow pattern of the bridge section that D/B=1:5 & 1:10.Flutter response of the models is measured.Meanwhile,to get more clearer cognition of the change of the wake flow,the Particle Image Velocimetry(PIV)is used to observe and record the flow field around the lower part of the model.Then the influence and mechanism of different patterns of wake flow on the flutter characteristics and flutter stability of the bridge are explored.The specific work contents are as follows:1.Flutter test under the control of the splite plate.For D/B=1:5,splitter plates of different thicknesses are placed in the wake area of the model to achieve different degrees of control on wake flow patterns.The flutter response and the flow field are simultaneously measured.The connection between the model flutter amplitude,vibration frequency and wind speed and the thickness of the the splitter plate is analyzed.The relation between the vortex intensity distribution characteristics of the flow field and the wind speed,the thickness of the the splitter plate and the vibration of the model is explored.2.Flutter test under the control of wind fairings.For the streamline segment model that D/B=1:10,with 30 o leading-edge wind fairings,different kinds of wind fairings are used to control the wake flow pattern.The vibration response of the model at different wind speeds is measured.The relation between the model’s flutter characteristics and the kind of wind fairings that represents the kind of wake flow pattern is analyzed.As the results show,there is a direct connection between flutter stability and wake flow.Both of the two experiments show that wake flow patterns have a Significant impact on the flutter characteristics and critical flutter velocity of bridges.The more blunt the fairing of trailing edge is,the higher the critical wind speed of flutter will be.