Numerical investigation of wind-induced airflow and interunit dispersion characteristics in multistory residential buildings

Abstract

Compared with the buoyancy-dominated upward spread, the interunit dispersion of pollutants in wind-dominated conditions is expected to be more complex and multiple. The aim of this study is to investigate the wind-induced airflow and interunit pollutant dispersion in typical multistory residential buildings using computational fluid dynamics. The mathematical model used is the nonstandard k-ε model incorporated with a two-layer near-wall modification, which is validated against experiments of previous investigators. Using tracer gas technique, the reentry of exhaust air from each distinct unit to other units on the same building, under different practical conditions, is quantified, and then, the possible dispersion routes are revealed. The units on the floor immediately below the source on the windward side, and vertically above it on the leeward side, where the reentry ratios are up to 4.8% and 14.9%, respectively, should be included on the high-infection list. It is also found that the presence of balconies results in a more turbulent near-wall flow field, which in turn significantly changes the reentry characteristics. Comparison of the dispersion characteristics of the slab-like building and the more complicated building in cross (#) floorplan concludes that distinctive infectious control measures should be implemented in these two types of buildings.

The airborne transmission of infection between flats in high-rise residential buildings: A review

“…Passive tracer gases, such as carbon dioxide (CO 2 ), sulfur hexafluoride (SF 6 ), propane (C 3 H 8 ) and haze-fog (HF), have been successfully and widely used in experimental and numerical studies of the inter-flat transmission and dispersion [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. The reason lies in the similarity of their aerodynamic behaviors to those various gaseous pollutants and fine aerosols.…”

“…The mass fraction was first proposed by Niu and Tung [26] and further developed by Ai et al [37] to quantitatively estimate the potential inter-flat flow based on a three-zone airflow and mass-balance model, whose detailed deduction can be found in [26]. The mass fraction, M i-j , is defined as the mass fraction of air that originates from the source flat i and is present in another flat j.…”

“…Considering the uncontrollable atmospheric conditions during on-site measurements and the scale problems of wind tunnel tests [70,71], Ai et al performed numerical simulations to study the wind-dominated inter-flat dispersion in a multi-storey slab-like building in terms of mean process using the optimized RNG model with the two-layer near-wall model [37,38], and transient process using LES model [40]. Besides, Ai et al [37,38,40] further investigated the effects of balcony on the dispersion behavior, which is out of the scope of this paper.…”

“…Besides, Fig. 6 depicts the partial results summarized from Ai et al [37,38] of dispersion patterns and re-entry ratios around a slab-like multi-storey building with different conditions. Detailed analysis and discussions regarding comparisons between Figs.…”

“…Previous on-site measurements [25,26] and numerical simulations [27][28][29][30] on buoyancy-dominated inter-flat transmission well explained and quantified the upward vertical transport of gaseous pollutants. Later, a series of wind tunnel tests [31][32][33][34] and numerical simulations [35][36][37][38][39][40] was carefully performed to study the inter-flat airborne transmission and dispersion dominated by wind effect. In addition, a few studies [26,29,39] provided some preliminary work on the dispersion mechanism driven by combined buoyancy and wind effect.…”