Numerical Simulations On Aerodynamic Forces And Response Characteristics Of A Thin Plate Under The Complex Wind Field

With the effects of global warming,the bridge structures are being affected by the increasingly harsh climate and environment,such as coastal typhoon,thunderstorm downburst,strong wind in mountainous terrain and other extreme weather phenomena.In order to describe such extreme weather phenomena in detail,domestic and overseas scholars have carried out a lot of research work on the characteristics of wind field by field measurement or wind tunnel test methods,and proposed the corresponding complex wind field models and applied them to the analysis of the response characteristics of some typical bridge sections.However,it should be noted that the existing studies are generally based on the Scanlan’s flutter and buffeting theory,and there exist few studies on the applicability of this theory in complex wind fields.Specifically,most of the current studies on the buffeting response of long-span bridges under complex wind fields express the aerodynamic forces on the structure as a linear superposition of bufeting forces and self-excited forces,while the applicability of the theoretical formula has not been strictly verified.Therefore,this paper took the thin plate as the research object,and used the numerical simulation method to calculate the aerodynamic force and flutter and buffeting response characteristics of the thin plate under complex wind fields.The main works are as follows:(1)This paper briefly introduced its research background and significance,and reviewed the theoretical basis of the aerodynamic force of the thin plate,the flutter and buffeting response of bridges and the research status of the impact of complex wind fields on bridges.Then,the shortcomings of existing research work were summarized,and the main aspects of research content of this paper were clarified.(2)Based on the fluid-structure interaction method,the numerical simulation of the thin plate in low turbulent wind field was carried out under static and vibrating states,respectively,and the aerodynamic force and flutter and buffeting response characteristics of the thin plate in low turbulent wind field were studied.Then,the differences between the simulated value of self-excited force and the calculated value based on the Scanlan’ s self-excited force theory were compared and analyzed.The research results show that the linear superposition relationship of Scanlan’s flutter and buffeting theory under the low turbulent wind field is approximately established,which provides a basis for subsequent research.(3)Based on the validated numerical simulation methods,the aerodynamic force and flutter and buffeting response of the thin plate in high turbulent wind field were studied,and the flutter derivatives of the thin plate in turbulent and uniform wind fields were identified by the forced vibration method.The research results show that the linear superposition relationship of Scanlan’s flutter and buffeting theory cannot be approximately established in a high turbulent wind field,and the flutter derivatives identified in the turbulent wind field can better express the aerodynamic force on the thin plate.On this basis,the parameter values in the self-excited force model of the thin plate under the turbulent wind field were proposed in this paper.(4)The forced vibration numerical simulation method was used to calculate the selfexcited force of the thin plate under the sinusoidal non-stationary wind field and the stationary wind field,respectively,and the differences and the reasons of the self-excited force of the thin plate between the simulated values and the calculated values from the Scanlan’s theory were analyzed based on the characteristics of the surrounding flow field.The research results show that under the non-stationary wind field,the amplitude of each harmonic component of the simulated self-excited force of the thin plate is obviously different from the calculated value of the Scanlan’ s theory.The non-stationary incoming flow intensifies the disturbance to the shear boundary layer at the leading edge of the thin plate,greatly affects the generation,shedding and drift of vortices in the boundary layer,and finally leads to the deviations between the simulated value of self-excited force and the calculated value based on the Scanlan’s theory.As the torsional amplitude of the thin plate increases,the deviations between the simulated value of self-excited force and the corresponding calculated value generally become larger,and more severe flow separations together with larger scales and influence ranges of shedding vortexes are generated around the thin plate.