山区峡谷风场分布特性及地形影响的数值模拟
Numerical simulation of distribution characteristic of wind fields and terrain’s influence in mountain canyon

为揭示山区峡谷风场的空间分布特性以及峡谷地形对谷内风场特性分布的影响，根据山区峡谷的地形特点，在AutoCAD中将峡谷的几何模型离散为高程点云，利用逆向工程软件Imageware将高程点云拟合成峡谷地形曲面，并导入Gambit中生成满足要求的计算模型；应用FLUENT软件选取适合山区风场的Realizable 模型，采用稳定性好的SIMPLE算法对峡谷风场特性进行数值模拟；最后根据峡谷地形特点和其影响参数，提出峡谷风速放大系数计算公式，并采用多个算例验证其正确性。研究结果表明：山区峡谷风剖面的轮廓线可以分成3段，不能套用平原地区常用的幂函数模型，并且峡谷风剖面的轮廓线具有明显拐点，风速增大段的风剖面轮廓线应采用线性函数与幂函数共同模拟；峡谷内中间位置风剖面最大风速大于两侧风剖面最大风速，其相应的风速拐点高度也较大；峡谷内同一高度观测点的风速在峡谷横断面上成抛物线变化，距离两侧山体约60 m处风速达到最大值；峡谷越窄，两侧山峰越高，峡谷内风场的“峡谷效应”越明显；风剖面风速拐点高度与峡谷高宽比成反比，峡谷高宽比越大，风剖面风速拐点高度就越小；该公式可推算山区峡谷内任意高度的风速，可为跨越山区峡谷的桥梁抗风设计基准风速的计算提供简便方法。
In order to reveal the spatial distribution characteristics of wind fields in mountain canyon and the effect of canyon topography on the distribution characteristics of wind field in valley, according to the topographic features of mountain valleys, the digital geometry of canyon was discreted into elevation points in AutoCAD, and the elevation points were used to synthesize the canyon terrain and surface by using reverse engineering software Imageware, which were imported into Gambit to generate computational models that meet the requirements. The Realizable model suitable for mountain wind field and the SIMPLE algorithm with good stability were selected to numerically simulate the wind field characteristics of canyon by FLUENT software. Finally, according to the characteristic of canyon topography and influencing parameter velocity amplification coefficient mathematical formulas of canyon wind were put forward, and its validity was proved by multiple calculating examples. The results show that the contour line of canyon wind profiles can be divided into three segmentations, and it cannot be simulated by the power function model that is frequently used in plain area. Moreover, the contour of canyon wind profile has obvious inflection point, and the contours of wind profile in wind increasing section should be simulated by linear function and power function. The maximum wind velocity of wind profile in middle of the canyon is greater than the maximum wind speed at both sides of the canyon, and the corresponding wind speed inflection point’s height is also higher. The wind speed at the same height observation point in the canyon is parabola in the cross section of canyon, and the wind speed reaches the maximum value at the distance of about 60 m between the two sides of the mountain. The smaller the canyon width, the higher the peak in both sides, and the more obvious the “valley effect” of wind fields in valley. The wind speed inflection point height of wind profile is inversely proportional to the canyon depth-width ratio, and