In this study, near-neutrally stratified planetary boundary layer (PBL) flows over complex terrain are numerically investigated via a one-way coupling of mesoscale numerical weather prediction (NWP) with unsteady computational fluid dynamics (CFD) codes. First, empirical turbulence model constants are modified to accomplish consistent turbulent viscosities between PBL schemes of mesoscale NWP and the \(k - \omega\) turbulence closure of microscale CFD. Next, to reconstruct turbulent inflows calculated from coarse NWP analysis, inverse distance weighted (IDW) interpolation is optimized and adopted around the coupling interfaces. This method has been shown to decrease prediction uncertainty, as high-aspect-ratio NWP grids are used. Compared with time-series measurements, the proposed approach presents wind velocities in agreement around both upstream and separated regions in the Askervein Hill case, although the turbulent kinetic energy on the leeward side is still underestimated. Another moderately complex terrain with an enlarged domain around Feng Men Hill also exhibits improved numerical results. Moreover, the unsteady simulations reveal that both wind speed-up and wake are highly correlated with inflow characteristics. The successful integration of the nesting simulation with a general CFD code demonstrates the flexibility and efficiency of this procedure in modeling high-resolution unsteady flows over complex terrain.

在这项研究中，通过中尺度数值天气预报 (NWP) 与非稳态计算流体动力学 (CFD) 代码的单向耦合，对复杂地形上的近中性分层行星边界层 (PBL) 流动进行了数值研究。首先，修改经验湍流模型常数以在中尺度 NWP 的 PBL 方案和\(k - \omega\)微尺度 CFD 的湍流闭合。接下来，为了重建从粗略 NWP 分析计算出的湍流流入，在耦合界面周围优化和采用反距离加权 (IDW) 插值。由于使用了高纵横比的 NWP 网格，因此该方法已被证明可以降低预测的不确定性。与时间序列测量相比，所提出的方法在 Askervein Hill 案例中在上游和分离区域周围呈现出一致的风速，尽管背风侧的湍流动能仍然被低估。另一个中等复杂的地形在凤门山周围扩大了区域，也显示出改进的数值结果。此外，非定常模拟表明，风速和尾流都与流入特征高度相关。