斜交桥下水流流向偏转角度的理论分析

我国现有铁路桥渡水文设计规范有关斜交桥的水力计算没有考虑桥下流向偏转的影响,从而影响计算精度。将流体力学中圆柱绕流经典理论的成果推广应用于双圆柱桥墩的情况,假设单桥墩的绕流流场可以按照一定的规律叠加,推导出圆柱形墩斜交桥梁桥下水流流向偏转角度的计算公式。分析表明,斜交桥下的水流流向偏转角度随斜交角度的增大先增大后减小,其极大值随压缩比的减小而增大。公式经与前人的试验资料验证,一定范围内吻合良好,并依据公式更正了此前流向偏转角度随斜交角度的增大而增大的错误认识。

Theoretical analysis of the deflection degree of the flow direction under bevel bridge

The norm of hydraulic design of railway bridge in China does not consider the effect of the deflect degree of the flow direction under bridge.By extending the calssical fluid mechanism result about the flow field round a pier to two piers,the formula of the deflection degree of flow direcrion is deduced with the assumption that the field around two piers simulates that of one pier.The formula shows that the deflect degree first increases,then decreases,and its maximum increases while the compress rate decreases.The formula fits with the laboratory data well in some condition,and corrects the mistake that the deflect degree only increases while the bevel increases.