Inlet extensions for wind towers to improve natural ventilation in buildings

Abstract

For centuries Wind Towers, also known as Windcatchers, have been used in hot and arid regions to naturally ventilate buildings. This study presents a solution to one problem of their functioning. It is known that at the top of the structure of the traditional wind tower there is a low-pressure zone, caused by boundary layer separation. This low-pressure zone is directly on top of the inlet opening, which has a much higher pressure. The proximity of this to key areas creates an ascending stream that forces the air out of the wind tower inlet opening. Inlet extensions are proposed in this work to force the air towards the inlet and to isolate the high-pressure zone from the low-pressure on top of the tower. Using CFD, 28 different designs of inlet extension have been tested. The results show that the great majority of designs increased air induction to the building by reducing to a minimum the ascending currents from inside the inlet opening to the outside of the towers. However, some of the designs tested formed vortexes inside the inlet openings that prevented the tower from getting more air induction. The present work can serve as a guide to what to do, and what not to do when designing a new wind tower, or when retrofitting an old one with inlet extensions.