Wind-induced natural ventilation of re-entrant bays in a high-rise building

This paper reports a systematic computational study of wind-induced natural ventilation and pollutant transport of re-entrant bays on a total of 30 generic building models of different building heights and with bays of different dimensions. Mean wind flow around each building model and wind-induced flow inside re-entrant bays are computed. To determine the ventilation efficiency of the bay, the computed flow field is used to disperse a scalar pollutant initially occupying the entire bay at a uniform concentration. The subsequent time decay of pollutant concentration inside the bay is studied and the ventilation efficiency is quantified by the retention time. The results show that wind-induced flow inside the bay, especially on the building side face, is complex and highly three-dimensional. Air exchange rates through the roof opening and vertical side opening are analyzed for each bay and their relationship to the ventilation efficiency is discussed. The bays on the building side faces are much worse ventilated than those on the windward or leeward building face. The deeper the side bay, the worse is the air exchange and ventilation. The building height is found to have a governing effect on the ventilation of the windward and leeward re-entrant bays.