The simulation of horizontally homogeneous boundary layers that have characteristics of weakly and moderately stable atmospheric flow is investigated, where the well-established wind engineering practice of using ‘flow generators’ to provide a deep boundary layer is employed. Primary attention is given to the flow above the surface layer, in the absence of an overlying inversion, as assessed from first- and second-order moments of velocity and temperature. A uniform inlet temperature profile ahead of a deep layer, allowing initially neutral flow, results in the upper part of the boundary layer remaining neutral. A non-uniform inlet temperature profile is required but needs careful specification if odd characteristics are to be avoided, attributed to long-lasting effects inherent of stability, and to a reduced level of turbulent mixing. The first part of the wind-tunnel floor must not be cooled if turbulence quantities are to vary smoothly with height. Closely horizontally homogeneous flow is demonstrated, where profiles are comparable or closely comparable with atmospheric data in terms of local similarity and functions of normalized height. The ratio of boundary-layer height to surface Obukhov length, and the surface heat flux, are functions of the bulk Richardson number, independent of horizontal homogeneity. Surface heat flux rises to a maximum and then decreases.

中文翻译：

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弱和中等稳定大气边界层的风洞模拟

研究了具有弱和中度稳定大气流特征的水平均质边界层的模拟，其中采用了使用“气流发生器”提供深层边界层的完善的风工程实践。根据速度和温度的一阶和二阶矩评估，在没有上覆反演的情况下，主要关注表层上方的流动。深层之前的均匀入口温度分布，允许初始中性流动，导致边界层的上部保持中性。不均匀的入口温度曲线是必需的，但如果要避免奇怪的特性（归因于稳定性固有的长期效应和湍流混合水平的降低），则需要仔细指定。如果湍流量随高度平滑变化，风洞地板的第一部分不得冷却。展示了接近水平均匀的流动，其中剖面在局部相似性和归一化高度函数方面与大气数据具有可比性或密切可比性。边界层高度与表面奥布霍夫长度之比以及表面热通量是整体理查森数的函数，与水平均匀性无关。表面热通量上升到最大值然后下降。边界层高度与表面奥布霍夫长度之比以及表面热通量是整体理查森数的函数，与水平均匀性无关。表面热通量上升到最大值然后下降。边界层高度与表面奥布霍夫长度之比以及表面热通量是整体理查森数的函数，与水平均匀性无关。表面热通量上升到最大值然后下降。