地面效应对近流线型断面静气动特性的影响

Ground Effects on the Static Force Coefficients of a Closed Box Girder

以风洞试验和计算流体动力学(CFD)相结合的方法,对存在地面效应的近流线型断面的静气动力特性(静三分力系数、St数)进行研究.首先,基于风洞试验获得近流线型断面在不同风攻角下的静气动参数随离地高度的变化规律,试验结果表明,地面效应将对断面静气动力特性产生不利影响.其次,采用CFD识别各试验工况下断面的绕流特征及静气动参数,分析了不同风攻角下地面效应对近流线型断面静力三分力系数的影响机理,数值分析表明,地面附面层带来的影响总体上减缓了桥梁下腹板与地面之间区域的流速,局部负压区的强度及尺度加强及增大,并增加了驻点处的压力.

As many existing or under-construction bridges are of lower height from the ground, the height could probably become a key factor to the wind-induced responses of bridges, hence it may have an adverse influence on the aerostatic and aerodynamic performances of bridges under wind loads. In this paper, wind tunnel tests and numerical simulation methods were adopted to study the ground effects on the static responses of a closed box girder. Frist, wind tunnel tests have been conducted to study the variation rules change laws of the static force coefficients correlated with the height from the ground of the closed box girder. It is found that ground effects will adversely affect the static wind stability of the closed box girder. Second, computational fluid dynamics （CFD） numerical simulations have been conducted to study the variation rules of the static force coefficients correlated with the height from the ground of the closed box girder. Through the CFD flow fields of the girder, ground effects mechanism on aerostatic performance of the closed box girder has been analyzed and described.