Simulation of twisted wind flows in a boundary layer wind tunnel for pedestrian-level wind tunnel tests

A wind tunnel study of effects of twisted wind flows on the pedestrian-level wind field in an urban environment

“…Since the topographical wind tunnel tests reproduce the field conditions under neutral atmospheric stability, it is reasonable to assume that the twisted wind profiles very likely exist in Hong Kong. In fact, Tse et al [18] confirmed the existence of twisted wind profiles in Hong Kong by analysing 256 wind profiles obtained from topographical wind tunnel tests. Their analysis reveals that the absolute difference in wind directions between the full-scale measurement heights of 25 m and 500 m can be as large as 40°i rrespective to wind speeds, in which the yaw angles were measured.…”

“…Nevertheless, the deviation can still be considered as significant when considering that its magnitude is larger than that of the Ekman Spiral and the deviation is confined to the lower 500 m of the ABL. Based on the results of the wind tunnel tests and CFD simulations carried out by Weerasuriya et al [26] and Li et al [27], Tse et al [18] conjecture that the hilly terrain of Hong Kong may generate large wind direction deviations in the lower part of the ABL. Consequently, the influence of the hilly terrain on the wind direction field should be included in the evaluation of the PLW field in Hong Kong for finding solutions for many wind-related issues, including outdoor thermal discomfort [28], degradation of air quality [29], increase of UHI effect [30], and favourable conditions for spreading airborne pathogens such as the SARS (Severe Acute Respiratory Syndrome) virus [31].…”

“…In other words, there were four types of vanes employed to simulate twisted wind profiles in this study. The previous publications of the authors [18][19][20] provide more details of the vane system.…”

“…The vertical variation in wind directions is a topic that has been insensitively studied in the field of yacht sail's aerodynamic [15][16][17]. Conversely, directional variations in a wind flow have not been systematically investigated in the field of wind engineering until very recent when Tse et al [18][19][20] conducted a series of wind tunnel tests using twisted wind profiles. Tse et al [18] first simulated twisted wind profiles, which have varying wind directions along the profile's height, in a BLWT and then used them for the wind tunnel tests to show the ways that twisted wind flows modify the PLW field near isolated buildings and arrays of buildings [19,20].…”

“…Conversely, directional variations in a wind flow have not been systematically investigated in the field of wind engineering until very recent when Tse et al [18][19][20] conducted a series of wind tunnel tests using twisted wind profiles. Tse et al [18] first simulated twisted wind profiles, which have varying wind directions along the profile's height, in a BLWT and then used them for the wind tunnel tests to show the ways that twisted wind flows modify the PLW field near isolated buildings and arrays of buildings [19,20]. Although these wind tunnel tests are indicative of the impact of twisted winds on the PLW field near https://doi.org/10.1016/j.buildenv.2017.11.041 Received 25 September 2017; Received in revised form 27 November 2017; Accepted 27 November 2017 generic buildings, it is not yet fully understood whether twisted wind profiles have similar importance in assessing the PLW field in an urban area.…”