Analysis and modeling on thermal and aero-dynamical forcing effect brought by urban canopy.

我们在上一个项目中开发了一套完整的直接测量系统，用于测量作用在建筑块区域上的阻力和来自城市树冠的标量通量传递，进行了系统和全面的风洞实验，以确定各种城市几何背景下的所谓整体阻力（动量）传递系数和整体阻力标量传递系数。只要选取合适的参数，我们就可以初步得到两个整体传输系数与城市几何形状之间的普遍关系。研究发现，不仅建筑物密度，而且建筑物的细长度、高度变化、排列随机性对城市冠层湍流结构的传递系数有重要影响。我们还采用了除风实验之外的其他方法; PIV技术和CFD，以确保调查在湍流结构方面城市树冠中和上方真正发生的事情。大涡模拟（LES）是目前最先进的CFD技术之一，它揭示了冠层上方出现的与冠层内部动力学相关的湍流有组织结构（TOS）对热力和气动力强迫效应的影响。

The complete set of elaborated direct measurement systems for both drag force acting on a building blocks area and scalar flux transfer from urban canopies, which we developed in the previous project, systematic and comprehensive wind tunnel experiments to identify the so-called Bulk Drag (Momentum) Transferring Coefficient & Bulk Drag Scalar Transferring Coefficient for various urban geometric contexts were carried out. We identified a good first-step inception to get somehow universal relations of both two bulk transferring coefficients with urban geometry as long as we choose appropriate parameters. We grasped that not only building density but also slenderness of each building blocks as well as height variation, array randomness are crucially affecting on the transferring coefficients through turbulent structure brought by urban canopies. We also took other methodologies than the wind experiment; PIV technique and CFD that make sure to investigate what is really happening in and just-above urban canopies in terms of turbulent structure. LES, one of up-most CFD techniques, reveals that TOS (turbulent organized structure) emerged above canopies in connection with dynamics within canopies significantly affects onthe thermal and aero-dynamical forcing effect.