Study on the combined effect of wind and buoyancy on cross-unit contamination around a high-rise residential building

Influencing Factors on Airflow and Pollutant Dispersion around Buildings under the Combined Effect of Wind and Buoyancy—A Review

“…Field and meteorological observations indicate that the airflow in an urban area is usually gusty, with wind speed and direction varying with time [96]. It appears that the strong winds may function as an air curtain with regard to blocking floor heat mass transfer between units, and this was revealed by several studies [97,98]. In the numerical study by Gao et al, when the temperature difference between wall surfaces and ambient air was 5 K (Tw − Tair = 5 K), as the ambient wind speed increased from 0.5 m/s to 2.0 m/s, the plume of pollutant released from the room was forced to approach the upper window, and when the wind speed further increased to 4 m/s, the warm plume development was limited [97].…”

“…For example, Huang et al [100] investigated the heated leeward wall surface and ground on flow and dispersion of rooftop stack emissions around an isolated building under four free-stream velocities (1, 3, 6, 9 m/s), and they reported that when Ri ≤ 0.26, the resulting vortex flow field was similar to that obtained in isothermal cases. In the common isolated building under nonisothermal conditions, as the approaching wind speed increased, the extent of pollutants in the upwards direction was suppressed, while the lateral dispersion first increased and then decreased [98]. Table 1 summarizes the studies focusing on approaching wind speed effects under surface heated conditions.…”

“…Second, the transmission of gaseous pollutants released from multistory buildings at different heights has attracted much attention [98,99,101,114]. For the pollutant source located at the lower, middle and higher parts of the building under the heating condition of the external wall surface, some studies have been previously performed.…”

“…When the source was located in the lower part of the leeward side, the concentration increased in both the upper and lower adjacent levels as the temperature of the leeward side increased, while the concentration decreased with the growth of leeward surface temperature when the pollutant was emitted from the higher floor of the leeward side. Furthermore, Liu et al [98] found that when Ri ≤ 3.5, the vertical upwards transmission was restrained as the source was located at the windward side. The pollutant transmission was in the downwards and horizontal directions when the source was emitted from the leeward side, and the worst situation was observed in the case of Ri = 0.074.…”

“…Wang quantified the ventilation rates through various typical window types and found that the ventilation rates and temperature distributions inside the building varied depending on the type of window, even though the areas where the windows open were almost identical [126]. Furthermore, open window or close window mode [99], thermal position [98,99,114] and building height [119] effects were taken into consideration in different articles.…”