Investigation of heat island effect on urban surfaces by using simulation method

Urban heat island became an important factor that affects climatic comfort in urban areas in recent years. Heat island effect that could be defined as higher air temperatures in an urban area than in a rural area in the same region adversly affects outside comfort conditions depending on surface temperatures of urban elements. In this study, the effect of heat island in urban areas in Elazig was evaluated by a computational fluid dynamics program. For this purpose, simulations were made for urban areas on Gazi, Şehit İlhanlar Streets and developing urban areas which have the highest urban density and results are evaluated by a parameter called heat island potential. Validation of the study was provided by comparing the simulation and observational results and convergence between %0.44-%2.56 was handled for different urban elements. Wind velocity and direction used in the simulations were taken from Government Meteorological Office and five-years avearege values were calculated. First of all, simulations were made for 1st, 11th and 21st days of June, July and August between 9.00-17.00 with no tree and traffic effect. After that, simulations were made for 11th days of June, July and August by adding traffic and tree effects remarkably. Simulations for building height (H)/ street width (W) ratios for 1, 2 and 0.5 for those cases mentioned above were also done. Traffic+tree effects were also added to simulations for 11th July for all H/W ratios. After all that in order to evaluate the effect of wind velocity on heat island potential, wind velocity for 12.00 am on every day of 1st, 11th and 21st days of June, July and August were increased about 2 m/s and for all H/W ratios. In order to define the effect of material properties on heat island potential, different material alternatives were determined for every urban element. Simulations were made for 11 th of July and by changing only one urban element's material properties. An extra section was also added to define the effect of adjacent and detached housing and building orientation on heat island potential. For this purpose, another location was determined and simulations were made for 11th of June, July and August. Simulation results were presented graphically and evaluated. Accordingly, significant impact of the paramaters including wind speed and direction, tree and trafic effect, different building height street width ratio, surface coating materials, building orientation and adjacent or detached buildings has been observed in urban areas. It was aimed to find and suggest important points that could be usefull to reduce the undesirable effects of heat island.