Abstract
This study investigates the effect of outdoor flow fields around urban-like block arrays on indoor ventilation flows within a building located in an urban canopy layer by analyzing datasets of a series of numerical simulations coupling indoor and outdoor airflows. Four configurations of building arrays and opening locations were adopted in order to consider how the difference in outdoor flow patterns affected the indoor velocity distributions and ventilation rates. The conclusions are summarized as follows. First, temporally averaged velocity distributions around block arrays were largely influenced by the array types, though opening locations hardly affected the outdoor velocity distributions due to large difference in indoor and outdoor velocity magnitude. In contrast, temporally averaged indoor velocity distributions were significantly sensitive to both opening locations and outdoor array types because the flow introduction through the openings was highly affected by the flow patterns near the openings. Second, temporal changes in the indoor velocity did not fluctuate with high frequencies, although the temporal changes considerably correlated with the outdoor velocity which temporally changed with a scale defined by the building length scale and approaching wind speed. Third, ventilation rates determined by a conventional method based on the pressure differences between building faces showed larger values than those determined by velocity in the openings in the present numerical simulations for all cases. In addition, turbulent ventilation remained even in the case where temporally averaged velocity in the openings became zero. These results indicate that we need to consider the effect of the outdoor airflow, which changes spatially and temporally, on the indoor velocity distributions and ventilation rates.
