水库蓄水对山区桥址风特性的影响

Influence of Reservoir Water Storage on Wind Characteristics over Bridge Site in Mountainous Area

为研究山区水电大坝蓄水后对库区桥位风场特性的影响,以某复杂深切峡谷大跨度悬索桥为工程背景,通过Gambit和ICEM分别构建了原始地形以及大坝蓄水后的地形数值模型,并应用软件FLUENT对两个模型进行了数值模拟,多工况对比分析了大坝蓄水对桥址区风速沿竖向和主梁跨向分布以及对主梁平均风速、风攻角和风向角的影响.研究结果表明:无蓄水时该桥址区风速有较明显的加速效应,风速放大系数高达1.14,但蓄水后明显降低;大坝蓄水后,大多数工况下主梁平均风速均有不同程度的降低,主梁的正攻角效应明显减弱,主梁平均风向角整体变化规律一致,风剖面形状在低海拔范围内有较大变化,而随着海拔增加二者逐渐趋于相同.

In th is study, th e in f lu en c e of a hydropower dam b u i l t in a mou ntaino us region on th e wind characteristics of a bridge site in the reservoir area after storing water was examined. For this purpose, the example of a long-span suspension bridge over a deep-cutting gorge in a complicated mountainous area was considered. The numerical terrain model of the original site and that of the site after the reservoir was filled with water were built by Gambit and ICEM. Numerical simulations for the two models were performed by employing computational fluid dynamics commercial software FLUENT. Different cases were analysed to identify the influence of the reservoir water storage on the distribution of wind velocities along the vertical direction and along the bridge deck, and to identify the influence of water storage on the average velocity of the bridge deck, attack angle,a n d wind d ire c t io n an gle. The wind velocity at the bridge site clearly increases as compared to the velocity before the reservoir is filled with water, and th e velocity ampl ificat ion facto r re a c he s up to 1. 14. Howeve r, th e velocity amplification factor decreases significantly after the reservoir was filled with water. The average velocity of the bridge deck in most cases decreased to different extents, a n d th e effect of th e pos itive a t ta ck angle decreased significantly after reservoir water storage. The variation in the average wind direction angle is consistent with that in the original model. The wind profile shapes exhibit considerable changes in a low altitude range after water storage, b u t they gradu al ly ten d to b e th e same as th e a l t i tu d eincreases. The conclusions o f this study provide a basis fo r the wind-resistant design o f bridges.