| Wind resistance ability for bridges worthes much more attention due toincreasing bridge span. Over the years, Wind Tunnel Test is commonly recognized asa direct and effective way to evaluate bridge performance in nature wind. However,with the development of fast computing resource and technology, Numerical WindTunnel is convinced to be another convenient and prospective method used foraerodynamic assessment of bluff body and bridge elements. Currently,Two-dimensional (2-D) and steady simulation in wind engineering has been replacedby more accurate three-dimensional (3-D) and unsteady simulation. This paper mainlyfocuses the flow characteristics around bluff and bridge girder section based on2-Dand3-D Large Eddy Simulation (LES).Firstly,2-D numerical simulation is employed to obtain the aerodynamiccoefficients, pattern of the pressure distribution, the location of flow separation andreattachment. The paper also analyzes the relationship between lift and vortexstructures in the wake, the requirement of span-wise grid density in3-D LES andfinds out the results of mean pressure distribution and flucutuating lift coefficientfrom3-D numerical simulation are much more exact corresponding to2-D numericalsimulation.Secondly, this paper obtains distribution of mean and fluctuating pressure alongthe cylinder surface and locates the separate point and vortex shedding zone aroundthe circle cylinder based on3-D LES. Furthermore, this paper studies vortex sheddingeffect on unsteady characteristics and coherence of pressure. Out-phase vortexshedding along the span-wise direction with flow visualization is analyzed and thenphase angle is obtained. Span-wise correlation length of the flow is obtained and theconcept of sectional fluctuating lift coefficient is put forward while the value of whichis obtained.Finally, flow characteristics around one box girder are analyzed. As for sectionmodel force test in Wind Tunnel, the requirement of span-wise dimension is at least0.5B. The effects of grid density and span-wise on aerodynamic coefficient areinvestigated. This paper finds out the different flow characteristics of streamline bodycorresponding to bluff body and analyses distribution of mean and fluctuatingpressure based on flow mechanism. Also, vortex shedding characteristics are analyzedand aerodynamic coefficients are obtained. This paper mainly carries out3-D LES of flow around bluff body and box girderbased on2-D numerical simulation and Wind Tunnel Test results and finds out thelimit of span-wise gird density(δ_z/D≤0.1). The results from3-D LES agree well withWind Tunnel Test results corresponding to2-D computations. Flow visualization isemployed to understand the vortex shedding characteristics of bluff body and boxgirder. |
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