Using a Computational Fluid Dynamics (CFD) Tool to Analyze the Influence of the Urban Form Over the Wind in a Tropical Humid Climate City

Abstract

The present research focus on the influence of the urban structure on the wind, with a case study in a specific part of city of Fortaleza, Ceará, Brazil. The study of air flow changing over the urban area covers the southeast sector of city, which is experiencing an urban expansion process caused by the housing market, intensifying its occupation and changing patterns of land use through tall buildings and constructive densification allowed by law. The wind is a key element to air quality in the urban environment and thermal comfort in hot, humid climate locations, the case of the city of Fortaleza. However, this urban climate element is structurally modified by the urbanization process.
The urban form is the result of urban standards such building height, occupancy rate and space between buildings, changing the permeability of the wind in the urban space. The study reproduced three virtual models representing the present situation, the maximum occupancy allowed and an intermediate proposal as a criticism of the permissiveness provided by law. These scenarios were simulated using the fluid dynamics software developed by the ANSYS Company, called ANSYSCFX, to analyze the airflow around buildings, allowing the physical phenomena to be captured more accurately and comparing the airflow within these three scenarios. The results indicated that the natural ventilation was prejudiced in the posterior region of the scenario of maximum occupancy. At the local level most of the points of comparison within the maximum occupancy model indicated better ventilation conditions about building’s height comparing to the intermediate model, attesting the influence of a lower occupancy rate.