New criteria for assessing the local wind environment at the pedestrian level and the applications

Abstract

The wind environment is a stochastic phenomenon. To deal with this stochastic feature, this chapter introduces the use of exceedance probability analysis to evaluate the properties of the wind. Two representative indices were adopted: the local purging flow rate (LPFR) and the space-averaged kinetic energy of the wind (KE). The former was used to express the ability of airflow to exhaust contaminants generated within a given space, and the latter was used to represent the ability of airflow to cool the human body. The local air change rate (LACR), defined as the local purging flow rate per volume of void space, was used as the ventilation index for application. The exceedance probability (EP) was calculated based on the wind speed distributions described by the Weibull function for 16 azimuths to indicate the exceedance probability of a given air change rate. The exceedance probability of the kinetic energy of the wind in the void space was also evaluated in the same manner as the local air change rate. Acceptable values of the exceedance probability for both the local air change rate and the space-averaged kinetic energy of the wind in the void space were suggested based on acceptable indoor environmental indices.