Zhen Bu

This paper discusses the sustainability of the areaway-attached basement concept with the attentions focused on wind-driven single-sided natural ventilation. First, numerical simulations were performed on an areaway-attached basement with a single-sided opening. Two CFD approaches: Reynolds averaged Navier-Stokes (RANS) and large-eddy simulation (LES) were used and compared with the previous experimental results of effective ventilation rate. A good agreement between the measurement and LES model was found and RANS model tends to underestimate the ventilation rates. Furthermore, Based on LES with the inflow turbulent fluctuations, the mean airflow patterns within and around the areaway-attached basement was investigated for different wind incidence angles to examine the influences of wind direction on ventilation performances.

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.

This paper presents an experimental investigation of the wind-induced single-sided natural ventilation for an areaway attached basement. The experimental data in terms of wind pressure coefficients (Cp) were measured on both the external surfaces of the areaway space and internal surfaces of the basement space for the detached building pattern and the multi building pattern. Several parameters, including the presence of the above-ground building, wind incidence angle, areaway configurations, surrounding sheltering expressed by building coverage ratio, were studied. The power spectrum analysis was further performed to study the pressure characteristics at different sampling point positions. The results revealed the influences of the investigated parameters and can provide fundamental data for future ventilation investigations.

This paper is devoted to study wind environment in a dense urban areas from the ventilation perspective. In order to take the stochastic characteristics of city wind into consideration, the exceedance probability analysis method was applied using air change rate as the index. The air change rate in the target domain was first obtained using CFD simulation for 16 wind directions and each building pattern. The CFD results demonstrated that airflow fields in the target domain were complicated and the air change rates depends greatly on wind direction. However, there is no direct correlation between street width and air change rate. The exceedance probability distributions were further calculated using the wind statistical data in Tokyo and used to analysis the influences of model orientation and street width. The results indicated that both factors affects the ventilation performance in the target domain significantly. The proposed evaluating approach is useful and effective for the urban ventilation design.