Computational analysis of indoor air circulation and heat transfer in a house ventilatedby wind-catch

Considering that natural ventilation is a climatic factor,a renewable alternative, as well as an important source of comfort, it seems to be relevant to consider its great potential when applied to architecture, taking into account economical and environmental gains. It is difficult to think about studying air circulation without mentioning the north Africa vernacular architecture and its ability to create the best solutions to increase the ventilation without any energy consumption, therefore, adopting passive cooling. According to Hassan Fathy (1986) -- an Egyptian architect who developed a collectionof fruitful works using natural ventilation and local materials -- in that region, ventilation, light and view could not be associated at the same time to a single windowbecause each function demands a different window configuration. Criative systems of passive cooling appearedin these areas and among them the wind-catch or malqaf can be distinguished. It was created to improveventilation requirements catching wind from high above, where the air is cooler, stronger and with less sand and other particles, and channeling it down into the building. In agreement with Fathy, another advantageof the malqaf is the possibility of solving the problemof screening that is the consequence of building settlementsin a ordinary town plan. In Egypt the malqaf is very developed and its first usage dates back to ancient historical periods. In this work, based on the writings of Fathy (1986) we analyse numerically one case in which wind-catch is used. It is the Qa of Muhib AdDin Ash-Shfi Al-Muwaqqi, known as Othmn Katkhud, in Cairo, dated from the fourteenth century A.D. presented in Fathys book, (Fathy 1986).The analyses start by solving the air circulation problems to determine the wind fields, using a mixed stabilised finite element method applied to the full Navier-Stokes equations. With these wind fields, the heat transfer problem is solved and analysed. Numerical results are compared with the studies presented by Fathy (1986). The results obtained suggest the capacity of cooling the indoor air by improving the ventilation with a reasonablearrangement of openings only.