Local Wind Field Measurement Above Bridge Deck And CFD Comparative Analysis

Long-span bridges in mountainous terrain need to cross complex terrain,the ups and downs of the terrain and the changing climate have made the mountain wind environment extremely complicated,to evaluate the driving stability of vehicles passing through mountain bridges in windy weather,it is necessary to analyze the wind characteristics of the bridge deck.The wind field measurement is the most direct data in the analysis of the bridge deck wind field.Through the comparative analysis and research of the local wind field measurement with CFD,the local wind field on the bridge deck can be more thoroughly understood.Thus,this thesis takes a long-span suspension bridge in the mountainous area as a background and analyzes the influence of wind speed,wind attack angle,and other factors on the local wind field of the bridge deck by combining field measurement with numerical simulation.The main research work of this thesis is as follows:1.Using computational fluid dynamics(CFD)analysis methods,relying on FLUENT numerical simulation software,the main beam 2D model and 3D model were established.The wind speed of the monitoring points above different lanes on the bridge deck is calculated,and the wind speed cloud diagram and the flow field trace diagram are drawn based on the results.The results are compared with the wind tunnel test results to verify the reliability of the model.The effects of different incoming wind speeds and wind attack angles on the local wind field of bridge deck were further analyzed,and the differences between the 2D and 3D models were discussed.A three-dimensional vehicle model was established,then the aerodynamic coefficients of the vehicles in different lanes and the differences in aerodynamic coefficients between different vehicle models were analyzed.2.The main beam model containing cables was established,and the distribution of the wind field above the cable was analyzed using the CFD method,the representativeness of the incoming flow of the wind field above the main cable is analyzed,the influence of the location of measuring point along cable and the height from cable on the representativeness of the incoming flow is discussed.3.The local wind field was measured on the bridge deck of the actual engineering bridge site,and the wind profiles at different lane positions were measured,and the wind field distribution at different positions along the main beam direction was also measured.After preprocessing the measured results,the spatial coherence of the bridge deck wind field along the main beam is analyzed,and the wind field measured results above different lanes are compared with the CFD results.The CFD bridge deck wind field study shows that: Different wind speeds have little effect on the wind environment of the bridge deck,and the wind environment of the bridge deck is less affected by the Reynolds number.As the wind attack angle increases from-7 ° to+ 7 °,the equivalent wind speed in each lane tends to decrease overall.To some extent,the2 D model can replace the 3D model to analyze and calculate the wind field above bridge deck.The inflow monitoring point is more suitable when it is installed at a height higher than 2.3m from the top of the cable,which can better represent the wind speed and wind attack angle of the inflow.Field measurements of the wind field above the bridge deck indicate: Along the direction of the main beam,the closer the measuring point is,the stronger coherence of wind speed.In the numerical simulation,the wind speed reduction coefficient of each lane is larger than the field measurement results.