缆索承重桥并列索平均气动性能的雷诺数效应

REYNOLDS NUMBER EFFECTS ON MEAN AERODYNAMIC FORCES ACTING ON PARALLEL CABLES OF CABLE-SUPPORTED BRIDGES

近距离并列吊索和并列斜拉索在大跨度缆索承重桥中有广泛的应用,但目前在计算并列索静力风荷载时只考虑顺风向阻力的影响,没有考虑因尾流干扰所产生的横风向升力的作用。通过风洞试验,在雷诺数Re=0.9×105~4.6×105(涉及亚临界雷诺数区和临界雷诺数区)研究了多种不同相对位置的并列双圆柱的平均阻力、平均升力和斯特罗哈数随雷诺数的变化规律。研究结果表明:并列圆柱的平均气动性能有强烈的雷诺数效应,临界雷诺数下的气动力系数与亚临界区有很大的差异;在临界雷诺数区域,下游圆柱的平均升力系数会随雷诺数的增大发生不连续突变,这种气动力的突变很可能与双圆柱绕流场的流态结构的演变有关;受上游圆柱的尾流干扰,在临界雷诺数区域内下游圆柱的平均升力系数可达到1.25以上,远大于下游圆柱的平均阻力系数,因而在计算并列索静力风荷载时有必要考虑横风向平均升力的作用。

Parallel hanger cables and stay cables are used extensively in cable-supported bridges. However, the cross-wind mean lift of downstream cables induced by wake interference received little attention when calculating the wind loads on parallel cables. At Reynolds numbers between 0.9×10^5-4.6×10^5 （subcritical Reynolds regime and critical Reynolds regime）, the aerodynamic characteristics of twin circular cylinders were investigated along with their relationships with the Reynolds numbers through a series of wind tunnel tests. Results show the mean aerodynamic forces of two circular cylinders in the critical regime were very different from those in the subcritical regime, showing strong Reynolds number effects. Furthermore, at the critical regime, the mean lift coefficients of the downstream circular cylinder discontinuously suffered abrupt change with the increase in the Reynolds number for some arrangements of the cylinders, which might be related to the shift of the flow state between different flow patterns. Under the wake interference of the upstream circular cylinder, the magnitude of the mean lift coefficient on the downstream cylinder was up to 1.25. Therefore, it is necessary to include the effect of mean lift when calculating static wind loads on parallel cables.