Large eddy simulation of microburst wind fields over flat and cuboid obstacle terrains

A microburst is a kind of extreme weather event capable of generating intense outburst winds near the ground within a short time. It can bring significant threats to the structural stability of buildings and the safety of aircraft during takeoff and landing. In this study, we develop an adaptive large-eddy simulation (LES) numerical framework for the simulation of a microburst. A high-order finite volume method and a Runge–Kutta scheme are applied for the spatial and temporal discretizations, respectively, to ensure the computational accuracy. Local adaptive grid refinement is employed to enhance the resolution of the near-wall region. Furthermore, we integrate the immersed boundary method (IBM) with LES to establish a computational approach for simulating the microburst over non-flat terrain, which is one of the contributions of this work. In the numerical results, the development of the microburst over both flat terrain and terrain with cuboid obstacles is compared and analyzed. We first compare the wind speed distribution on flat terrain with previous experimental and numerical simulation data, and analyze the fitting capability of a classical physical model—the Vicroy empirical model—for the wind speed profile. These results indicate a close correspondence between the wind velocity profiles and prior studies, and the Vicroy empirical model demonstrates a notable capacity to accurately replicate the profile during the initial phase of the microburst, while exhibits a substantial discrepancy after the secondary vortex appears. Then we investigate the influence of different obstacles' parameters on flow evolution and wind shear intensity. The results show that obstacles exert a significant impact on airflow, such as changes in peak wind speeds, the formation of jet-like high-speed regions on their lateral and rear sides, and the development of strong wind shear zones behind them where the F-factor can change from −0.9 to 0.9. These findings can provide valuable guidance for the design of buildings and other engineering structures, as well as the security of aircraft safety.