大型中心城市平均风速剖面特性的风洞试验

用缩尺模型模拟了上海市同济大学四平路校区所处城市中心区域WNW方向上1.8km×8.0km范围内的真实地貌,通过对该地貌及其衍生地貌工况的风洞试验研究了城市地貌特征、远场与近场地貌的差异以及地貌起点到观测点的距离对平均风速剖面和相关风场参数的影响。结果表明,在平均风速剖面发展稳定前,梯度风高度处于不断升高中,地貌起点距观测点的距离对其影响较大;地貌特征对风剖面的影响极大;研究范围内的大城市中心地貌的地面粗糙度指数达到0.50～0.75,远大于我国现行荷载规范给出的大城市中心地貌的地面粗糙度指数值0.30。建筑结构荷载规范中大城市中心地貌的地面粗糙度指数取值有待增大。

Wind Tunnel Experiments of the Mean Wind Profile Characteristics over a Large Central City

In the paper, the real buildings within a range of 1.8km×8.0km in a central area of Shanghai along the direction of WNW near Tongji University were reconstructed by scale models. The influence of the urban terrain features, the differences between far and near terrains and the distance between the starting position of the terrain and the observation location on mean wind profiles and wind field characteristics were discussed with wind tunnel experiments. Results showed that the gradient wind height is on the increase, until the wind profile becomes steady, with the increase of the distance between the starting position of the terrain and the observation location; the wind profile is influenced by terrain features greatly; the ground roughness exponents of the urban district in Shanghai are estimated as 0.50 to 0.75, which is far greater than the corresponding value 0.30 in the load code for the design of building structures in China. The value of ground roughness exponent of the urban district of large cities presented by the load code for the design of building structures should be increased.