The fluid mechanics of natural ventilation

Natural ventilation of buildings is the flow generated by temperature diffe rences and by the wind. The governing feature of this flow is the exchange between an interior space and the external ambient. Although the wind may o ften appear to be the dominant driving mechanism, in many circumstances tem perature variations play a controlling feature on the ventilation since the directional buoyancy force has a large influence on the flow patterns with in the space and on the nature of the exchange with the outside. Two forms of ventilation are discussed: mixing ventilation, in which the interior is at an approximately uniform temperature, and displacement ventilation, wher e there is strong internal stratification. The dynamics of these buoyancy-d riven flows are considered, and the effects of wind on them are examined. T he aim behind this work is to give designers rules and intuition on how air moves within a building; the research reveals a fascinating branch of flui d mechanics.