Three-dimensional flow structure and ventilation dynamics of a cross-ventilated building

We present measurements of the three-dimensional flow structure and mixing dynamics for a cross-ventilated building model. The geometry consists of a cuboid building adapted from the wind tunnel study by Tominaga and Blocken (2015) with windward and leeward windows and a simple open interior. Comparisons are also made to a solid building with the same exterior dimensions. Experiments are conducted in a small-scale water channel facility at a fully turbulent building Reynolds number of 8,000. Kinematic similarity with high Reynolds number studies is maintained by enforcing the ratio of the building ventilation time scale to the characteristic advection time scale. A passive scalar contaminant is released upstream of the building for steady and transient release profiles. The three-dimensional velocity field is measured using magnetic resonance imaging and the time-resolved concentration field on the building center plane is measured using planar laser induced fluorescence. Together, these datasets provide two independent measurements of the building ventilation rate to validate the scaling methodology, and comparisons to high Reynolds number wind tunnel data demonstrate the efficacy of the low Reynolds number water channel, as long as the flow is fully turbulent and kinematic similarity is achieved. The results show that the building ventilation prolongs the plume residence time in the wake relative to the unventilated solid building case. Additionally, the spatially-averaged interior concentration is in good agreement with well-mixed arguments, yet zonal measures of interior fluctuations can be significant and are correlated to the cross-ventilation flow structure. Overall, these data elucidate the complex flow structure and unsteady plume dynamics around and within the building.