Directly determining mean and instantaneous ventilation rates using stereoscopic PIV for single-sided and cross ventilations of a cubic building

Since the indoor ventilation significantly influences human health and comfort, there has been a huge demand for realizing a sustainable air conditioning system by utilizing natural ventilation. Although there are numerous experimental studies on wind-induced natural ventilation, these experiments were unable to determine the genuine ventilation rate based on the velocity component normal to opening because of the methodological limitations. In this study, therefore, stereoscopic particle image velocimetry was progressively employed to determine three velocity components within a lateral opening of an isolated cubic building in single-sided and cross ventilation conditions. As a result, the mean, variance and covariance of velocity components at lateral opening of the single-sided-ventilation model are comparable to those of the cross-ventilation model. On the other hand, after the flow goes into the building, the velocity fluctuations are significantly reduced in the single-sided ventilation condition, while it decays more slowly in the cross-ventilation condition. In addition, the mean and instantaneous ventilation rates were experimentally determined to quantify the contribution of the turbulent flow passing to the ventilation rates. This study clarifies the ventilation mechanism by turbulence and provides reliable database of ventilation flow for numerical validation.