STUDY OF VISITATION FREQUENCY AND PURGING FLOW RATE OF URBAN AREA BASED ON CFD ANALYSIS

Study on ventilation efficiency around an elevated highway

Abstract

Ventilation efficiency around heavy traffic road covered with elevated highway and side buildings is evaluated with Visitation Frequency (the times for contaminant to return back to the objective domain) and Purging Flow Rate (the air flow rate for defining the domain averaged concentration). These are analyzed by the CFD (Computational Fluid Dynamics) based on the standard k-ε model. The properties of VF and PFR of four objective domains are analyzed with the changes of wind direction and arrangements of road center obstacles under the elevated highway. The resulting VF more than 1.0 are shown for all cases, which means that contaminant circulates within the objective domain enclosed with the elevated highway and side buildings. The influence of the arrangement of the buildings around the objective domain and the structure in the domain on VF is large. In the case of no obstacles under the elevated highway, the ventilation frequency tends to be high.