Numerical Simulation of Wind-Induced Ventilation in Urban Buildings of Random Staggered Arrays

The utilization of wind-induced ventilation of an urban building can reduce energy consumption by a cooling system. This project investigates the effectiveness of wind-induced ventilation within arrays of buildings. In atmospheric boundary layer, the pressure difference between windward and leeward sides of buildings generates ventilation. This is however affected by interference effects from surrounding structures and by surface heterogeneity which contributes to pressure and form drags. OpenFOAM simulation is conducted in this study using large-eddy simulation (LES) models to simulate turbulent flow over urban-like arrays from which pressure and velocity distributions are obtained. These arrays comprise of blocks of different heights; nine types of blocks are distributed randomly in an array to construct a simplified urban model based on the geographic information system (GIS) dataset of Tokyo [Hagishima et al. (2009) and Zaki et al. (2011)]. Whilst the standard deviation of block height in each array remains fixed, the packing density i.e. the ratio of occupied area by blocks to the total surface area is varied from 4.4% (sparse array) to 44% (dense array). The distribution of pressure coefficient difference of a building model is expected to be of higher value at the upper half as obtained in a previous study [Cheng et al. (2003)]. The presence of non-uniform elements is likely to increase shear stress which then contributes to turbulence kinetic energy (TKE) in the proximity of canopy level. The pressure distribution of a building is important in building physics when designing its structural performance. Additionally, this would help the study of scalar dispersion such as heat and pollutants within canopy to improve urban air quality.