桥墩布置形式对桥墩绕流及局部流场的影响

The Influence of Bridge Pier Arrangement on Circling Flow Around Bridge Pier and Local Flow Field

应用MIKE21软件模拟分析了不同桥墩布置形式斜交桥对河道局部流场的影响。模拟结果表明:单线斜交桥对水流有明显阻水影响,双线斜交桥对水流的阻水影响,并不是简单叠加;下游桥桥墩与上游桥桥墩对孔布置且桥墩相距较近,下游桥桥墩受上游桥桥墩的遮蔽作用,其阻水影响被削弱,对水流的消能和流速再分配有一定作用;下游桥桥墩与水流方向夹角的改变,除使桥墩附近局部区域水流流态变化明显,并随着角度增加影响增大、其他区域变化值相差不大,不存在单调关系;圆端形桥墩应尽量采用顺水流布置,非顺水流布置时,如果对桥墩附近局部区域水流流态的影响较大,可通过开挖拓宽桥址处河道,降低河道单宽流量,增加河道过流面积的方法改善。

Based on MIKE21 software the influence of different pier arrangement in double-line skew bridge on the local flow field is simulated and analyzed. The simulation results show that the single-line skew bridge has a significant blocking water effect on water flow, and the blocking water effect of double-line skew bridge is not a simple superposition. Since hridge piers downstream and up- stream are arranged on-the-hole and they are closer, lower bridge piers have smaller blocking water effect with certain effects on en- ergy dissipation and the redistribution of flow velocity in view of the shielding effect of upper bridge piers. The change of angle be- tween the axial direction of lower bridge piers and the flow direction makes the flow pattern in local region around piers change great- ly, and the influences increase along with the increment of the angle. The change value in other regions has little difference and there exists no monotonic relationship between them. The round ended piers should be arranged in the flow direction as much as possible. Otherwise, if the bridge piers have a great effect on the flow pattern in local region around piers, it is effective to excavate the beach to compensate the flow area occupied by the project.