A numerical study of microburst-like wind load acting on different block array configurations using an impinging jet model

• The microburst wind load on block array configurations is numerically investigated.
• The impinging jet model mimics the downburst wind; k–ω SST models the turbulence.
• The pressure and viscous drag force acting on obstacles in the arrays are presented.
• A semi-empirical model is derived to estimate the averaged wall shear stress.
• The vertical lift force acting on arrays with various packing densities is discussed.

A numerical investigation on the microburst-like wind characteristics in block array configurations has been performed using Computational Fluid Dynamics (CFD). The CFD modelling of impinging jet mimics a microburst wind shear. Effects of plan and frontal area densities on the drag and lift force acting on the arrays are studied by investigating the wall shear stress and pressure distributions. A semi-empirical model based on Poreh et al. (1967) is derived to estimate the spatially-averaged wall shear stress of the finite urban array located near the microburst storm centre. Moreover, the pressure and viscous drag force acting on obstacles in the arrays with different plan and frontal area densities are discussed and compared with the published results regarding the arrays placed in a neutrally stratified Atmospheric Boundary Layer (ABL) flow. The present results show that the viscous drag is insignificant relative to the total drag force for all the cases with different frontal and plan area densities (i.e. roughness packing densities). The mean vertical lift force acting on the arrays for various packing densities is discussed, and the lift force is compared with drag and resultant forces. The averaged lift force acting on a block in the array is 0.3–0.6 times of the magnitude of the resultant force. Therefore, it should be taken into account for the design and maintenance of high-rise buildings in cities.