Unsteady RANS simulation of wind flow around a building shape obstacle

This work aims to find the origin and connection of the surface, near-wake, and far-wake structures in the flow encompassing a high-rise building for a high Reynolds number. The origin and interconnection of the stream-wise tip vortices, with the other components of the wake, is analysed in this study for the current scenario. The Unsteady Reynolds Averaged Navier-Stokes equations (URANS) together with the realizable k-ϵ turbulence model have been used in this investigation to study the turbulent wake flow following a ground-surface-attached square shape building. A moderately big obstacle aspect ratio of 4, a Reynolds number of 12,000, and a thin evolving boundary layer thickness have been used in the flow modeling. The designed flow addresses the reversed-flows at the outlet during computation to improve the accuracy of the realizable k-ϵ model. The Reynolds stress components are retrieved using the Boussinesq approach. The wake’s principal compositions, including span-wise-side eddies and area of high stream-wise vorticity in the uppermost portion of the wake, are illustrated by both three-dimensional (3D) representations and planner projections of the mean flow distributions. A braided vortex formation, composed of asymmetric hairpin vortexes, is witnessed in the far-wake area. The association of the near-wake vortex structures with the far-wake and near-wall flow, which is associated with the flow strengths, is also discussed. In this investigation, few areas of large stream-wise vorticity magnitude, like tip vortexes, are correlated to the 3D curving of the fluid motion, and tip vortices did not continuously reach to the free end part of the building. The 3D fluid motion interpretation, which combined several measurements of the flow distribution encompassing the cylinder, shows that the time-averaged near-wake structures are formed of two segments of distinct source and section of dominance. Furthermore, addressing reversed-flow during computation shows notable improvement in the results.