高精度入口边界的峡谷桥址风场数值模拟

山区峡谷地区由于受特殊地形地貌条件影响使得其风场十分复杂，这些地区建立的大跨度桥梁面临着更为突出的风致振动问题，而当前规范对峡谷桥梁的抗风设计还没有明确规定。为更加深入认识峡谷风场的分布特性，基于WRF与CFD耦合模式对峡谷桥址风场进行精细化分析，在中尺度气象模式基础上结合多项式插值方法获取入口边界的平均风速，同时对峡谷桥址上游风速进行实时监测，利用实测站脉动特性互等的原则获取数值模拟入口位置的脉动特性。将平均风速和脉动风速综合考虑后利用UDF程序赋给大涡模拟的入口边界并对峡谷桥址位置风场进行详细分析，最后将模拟结果与实测结果的湍流特性进行对比。研究结果表明：考虑脉动风速后的入口边界条件相比于无脉动入口风速其湍流特性与实测值吻合更好；中国现有规范中的标准谱不适用于复杂峡谷桥址地区，如用现有规范设计山区峡谷桥梁，其结果偏不安全；来流风向与峡谷走向是引起加速效应的主要原因，峡谷上游的复杂局部地形是引起峡谷桥址风场多样性的根本原因。研究成果可供山区峡谷大跨度桥梁抗风设计提供参考。

Numerical Simulation of Wind Field at Canyon Bridges with High Precision Inlet Boundary

Wind fields in mountain canyons are complicated due to the influence of topographical conditions and terrain. Large-span bridges established in these areas face prominent wind-induced vibration problems. The wind-resistance design of a canyon bridge is thus not yet clear. In this study, multi-scale coupling technology was used, between Weather Research and Forecasting (WRF) and Computational Fluid Dynamics (CFD), to analyze the wind field of a gorge-bridge site. Accordingly, the average wind speed at the inlet boundary was obtained by polynomial interpolation, while the fluctuating wind speed at the inlet boundary was acquired from the field measuring station. The Weighted Amplitude Wave Superposition (WAWS) method was then utilized to generate random fluctuating wind velocities. Using the User Defined Function (UDF) program, the target wind-field dates were assigned to the inlet boundary of Large Eddy Simulation (LES). The results showed that the rationality of the wind filed distribution improves while under the fluctuating wind speed. The standard spectrum utilized in China is not suitable for complex mountain gorge areas. If the existing codes are used to design mountain gorge bridges, the design results will be unsafe. The complex local topography of the upper canyon is the main reason for the diversity of the wind field at the canyon bridge site. When the inflow is along the gorge trend, the acceleration effect may occur inside the gorge, which is more apparent when the inflow wind passes through the complex mountain. Results from related research can provide references for the wind-resistance design of large-span bridges in mountain valleys.