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

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 features of the criteria are proposed seasonally (summer and winter, respectively) and the overall mean wind velocity ratio (OMVR) 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.