Computational Analysis of Heat Wave and its Mitigation in an Urban Microclimate

Abstract

Climate change is having various kinds of adverse effects on the society and the environment. The frequency of summer-time heat waves is increasing and Urban Heat Island Effect can significantly affect the local microclimate which consequently escalates human mortality and mortality. Most of the studies performed in this area are employing field measurements and observational methods which is inadequate to predict the urban temperatures, deterministic approach is required in order to completely forecast the thermal environment. In this study, a computational fluid dynamics simulation of an urban micro-climate during a period of heatwave is performed. 3D unsteady Reynolds-averaged Navier Stokes (URANS) simulations with the realizable k-ε turbulence model are performed on high-resolution computational grid.Various climate variables such as surface temperature, wind velocity and air temperature have been calculated. The CFD surface temperature data is compared with the Satellite Data from the MODIS product of the June-2015 heatwave period in Karachi in the year 2015. A reasonable agreement of the simulated data with the satellite recorded data has been obtained. It is therefore concluded that CFD has the prospect to precisely determine the urban surface temperature with deviation of around 10% from the satellite data. Moreover, as a climate adaptation measure, the effect of albedo or decreased surface absorptivity on the outdoor environment is simulated. It has been observed that high albedo can decrease the temperature up to 2oC, thus decreasing the heat stress.