Use of local age of air to study the relation between ventilation efficiency and building configuration

Since human population living in urban areas has been increasing rapidly, strategies to reduce the urban heat island effect are becoming more crucial. It is well-known that appropriate ventilation designs where the wind is able to blow away local heat and pollution accumulation might help with the situation. This paper uses the concept of the local age of air, defined as the time taken by fresh air to replace old air after it enters to a given zone, to evaluate the relation between ventilation efficiency and building configurations. For this purpose, CFD simulations were carried out by using OpenFOAM, the calculation domain was set to x: 1000 m, y: 1000 m, z: 180 m and the actual building site was defined as x: 355 m y: 365 m, z: 180 m. Results showed that in complex locations with a large number of buildings the local age of air is higher than that in contrasting locations. Additionally, it was found that some urban parameters, such as the ratio of the area that is not occupied by any building, improve the ventilation efficiency