New criteria for assessing low wind environment at pedestrian level in Hong Kong

Abstract

The choice of proper wind comfort criterion is considered to be crucial to reliable assessment of pedestrian level wind comfort. This paper aims to propose a wind comfort criterion that can be applied to Hong Kong, in which the wind comfort is seriously deteriorated by the moderated airflow, particularly in the hot and humid summer. By thoroughly reviewing and comparing exiting wind comfort criteria, the parameters in Lawson (1978) criterion are adopted for acceptable, tolerable and intolerable category and the parameters in NEN8100 (2006) criterion are adopted for danger category in the proposed criteria. Besides, a low wind parameter suggested by AVA scheme (2005) is adopted for unfavourable category in summer criterion. The adopted parameters provide scientific foundations and they are carefully chosen to adapt the weak wind conditions. The prominent feature of the criteria is proposed seasonally (summer and winter, respectively) and the overall mean wind velocity ratio () is used as threshold wind velocity parameter. The wind tunnel tests of Hong Kong Polytechnic University (HKPolyU) campus model were used as a case study. The results show that the proposed criteria can reasonably represent the weak wind condition and provide suitable assessments of the wind comfort in Hong Kong. Moreover, the findings in this study provide scientific basis for future policy-making and the proposed criteria can also help city planners to improve the pedestrian level wind comfort.

Evaluation of pedestrian wind comfort near ‘lift-up’ buildings with different aspect ratios and central core modifications

“…However, authors of this paper are not entirely convinced about the probabilities of exceedance of winds defined by Ref. [9] due to the lack of data available from field surveys and measurements. Therefore, the proposed criteria only specify threshold wind speeds for several comfort classes without defining any probability of exceedance for the threshold wind speeds.…”

“…Recently [9], have proposed wind comfort criteria for low wind speed conditions in Hong Kong. They adopted two sets of threshold wind speeds and probabilities of exceedance of wind to define wind comfort and wind danger in summer and winter seasons.…”

A review on the study of urban wind at the pedestrian level around buildings

“…However, all of the above-discussed criteria did not consider pedestrian discomfort due to weak wind conditions for the densely-built urban areas. Du et al [25] proposed the wind comfort criteria for the urban areas of poor wind conditions such as Hong Kong, where the wind comfort becomes worst in hot and humid season. In this criterion overall mean velocity ratio (OMVR) is used as threshold parameter (Table 1), which represents the integration of direction values of mean velocity ratio ( = MVR U U / P r ), Where U P is wind velocity at pedestrian level and U r is wind velocity measured at 200 m height.…”

“…Wind comfort criteria based on overall mean velocity ratio (OMVR) representing weak wind conditions by [25].…”

Perception of Wind in Open Spaces

“…However, seasonality can make this influence pleasant or unwelcome as follows.In hot weather conditions, the correct design of open spaces will direct wind into an air corridor which can reduce the duration of thermal discomfort [13]. The positive role of wind corridors in creating an acceptable outdoor thermal environment has been well researched [14][15][16][17][18][19] and is recommended as a thermal adaptive strategy for many climate conditions [6,20]. Conversely, in cool seasons, strong wind blows induce thermal discomfort which can be mitigated by windbreakers or shields [21].…”