Turbulent flow over urban-like roughness has been numerically studied for various purposes, such as the clarification of turbulent characteristics over rough walls, visualization of turbulent structures around block arrays, and evaluation of urban ventilation and pedestrian winds. In such simulations, a portion of the developing boundary layer is extracted as a numerical domain, assuming periodic boundary conditions in the horizontal direction to reproduce laterally homogeneous rough surfaces. However, the conditions required to drive the airflow by an artificial momentum source uniquely determine the turbulent statistics, which are different from those in developing boundary layers. Therefore, this study presents a new approach for driving the airflow over urban-like block arrays. The new method is based on spatially averaged Navier–Stokes equations to prove the necessity of height-dependent momentum provision. The turbulent flow over a cubical-block array is determined using large-eddy simulations driven by four different momentum sources. Regardless of the driving force, the vertical profiles of the streamwise velocity components are identical. In contrast, slight differences in the vertical Reynolds stress, variances in the velocity components, and turbulence kinetic energy are appropriately reproduced in the new approach. In addition, the budget equations of the turbulent statistics reveal that a change in the vertical Reynolds stress affects the energy production and its redistribution into variance components. The proposed method can contribute to the reproduction of a realistic turbulent flow and provide a theoretical understanding of the momentum provision.

人们对类城市粗糙度上的湍流进行了数值研究，用于各种目的，例如阐明粗糙墙壁上的湍流特征、块阵列周围湍流结构的可视化以及评估城市通风和行人风。在此类模拟中，将发展中的边界层的一部分提取为数值域，假设水平方向上的周期性边界条件以再现横向均匀的粗糙表面。然而，由人工动量源驱动气流所需的条件唯一地决定了湍流统计数据，这与发展边界层中的湍流统计数据不同。因此，这项研究提出了一种在类似城市的块阵列上驱动气流的新方法。新方法基于空间平均纳维-斯托克斯方程来证明提供高度相关动量的必要性。使用由四个不同动量源驱动的大涡模拟来确定立方体块阵列上的湍流。无论驱动力如何，流向速度分量的垂直分布都是相同的。相比之下，新方法适当地再现了垂直雷诺应力、速度分量的变化和湍流动能的细微差异。此外，湍流统计的预算方程表明，垂直雷诺应力的变化会影响能量产生及其向方差分量的重新分配。