New inflow boundary conditions for modeling twisted wind profiles in CFD simulation for evaluating the pedestrian-level wind field near an isolated building

Abstract

The hilly topography of Hong Kong influences oncoming winds and gradually changes their wind directions along the profiles' height. The vertical variation in wind directions, or the twist effect, significantly influences the Pedestrian Level Wind (PLW) field in urban areas of Hong Kong, thus it is a topic demanding systematic investigations. In this study, a new set of inflow boundary conditions are proposed to model twisted wind flows in Computational Fluid Dynamic (CFD) simulations. The new inflow boundary condition derived based on the horizontal homogeneous assumption, specifies a vertical profile of lateral wind speeds at the inlet boundary to sustain the twist effect in the empty computational domain. The proposed boundary conditions are used to simulate the PLW fields near three isolated buildings with different Height-to-Width ratio using two CFD codes; OpenFOAM, and FLUENT. The results reveal that OpenFOAM is more reliable in simulating PLW fields in twisted wind flows using the new set of boundary conditions. The three-dimensional flow field provided by the OpenFOAM simulation shows sparse streamlines downstream the buildings, indicating lack of organized eddies in the building far wake, which negatively affects the dispersion of air pollutants in twisted winds.

Large-scale forcing effects on wind flows in the urban canopy: Impact of inflow conditions

“…At present, it is not clear how the choice of one these two options affects the CFD results in terms of mean velocity and turbulent kinetic energy profiles, yaw and pitch angles. Weerasuriya et al (2018) adopted different CFD codes to simulate twisted wind flows effects on buildings, showing large differences in wind speeds in the downstream zone, compared to those measured in the WT tests (Tse, Weerasuriya, Zhang, Li, & Kwok, 2017).…”

Analysis of infrared extinction performance of the smoke screen in the field

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Recent advances in modeling turbulent wind flow at pedestrian-level in the built environment

“…Among the studies investigated in this review, SRANS is broadly Fig. 1 CFD applications in PLW studies published in recent 5 years applied to investigate PLW flow fields in different urban settings, ranging from an isolated building (Huang et al, 2021;Jia et al, 2021;van Druenen et al, 2019;Weerasuriya et al, 2018;Zhang, Yang, et al, 2021) to more complex geometries such as building arrays (Allegrini & Carmeliet, 2017;Hang, Chen, et al, 2018;Hang, Xian, et al, 2018;Lin et al, 2019;Sattar et al, 2018;Sha et al, 2018), generic street canyons (Liu et al, 2021;Sun & Zhang, 2018;Wen & Malki-Epshtein, 2018;Yang et al, 2020;Zhang et al, 2019;Zhang, Chen, et al, 2020), and realistic urban areas (Ricci et al, 2020;Santiago et al, 2021;Sousa & Gorle, 2019;Tsichritzis & Nikolopoulou, 2019;Vervoort et al, 2019).…”