Investigation of Ventilation Effectiveness for Wind-Driven Single-Sided Ventilated Buildings Located in an Urban Environment

This study employed large-eddy simulation (LES) to investigate wind-driven single-sided natural ventilation for an idealized building model located in an urban environment. Two ventilation cases, single-sided ventilation with an opening on the windward wall and with an opening on the leeward wall, were considered. The airflow rates through the single opening were calculated based on the mean flow fields and the transient flow fields, respectively. The comparisons showed that using only the information from the mean flow fields under-predicted the airflow rate and indicated the important role of fluctuating flow in the case of wind-driven single-sided ventilation. Using the homogeneous emission method, we further calculated the effective ventilation rates in the target indoor space and fairly good agreements were found in comparison with the measurements. The relationship between the airflow rate through the opening and the effective ventilation rate in the indoor space was studied by defining the ventilation efficiency for single-sided ventilation. This was 31.7% and 37.5% in the windward and leeward cases respectively, indicating a short-circuiting of fresh air at the opening. Based on a further analysis of the time-series data from LES, it was found that the variations of the airflow rate were significant while the variations of the effective ventilation rate were small.