Evaluation of the impact of design components on optimizing the thermal comfort of the bazaar sidewalk in Ahvaz city

Introduction
As a vital element of successful cities, public spaces play an important role in achieving the goals of sustainable development and dealing with climate change. Also, new research studies in the field of urban environmental performance and architecture state that the climatic design of urban spaces is one of the main criteria of urban progress and has a wide impact on achieving thermal comfort. Thermal comfort plays a key role in encouraging people to use public open spaces, especially in hot climates. The high presence time of pedestrians in the open space of a bazaar, along with the tense and specific climatic conditions of Ahvaz city, is one of the obstacles that hinders the possibility of creating thermal comfort. The target of this research is to achieve an optimal pattern that is affected by the type of "architectural massing" in terms of orientation, distance, height, etc., "shading" through artificial canopies and "surface materials".
 
Materials and Methods
The area studied in this research is the city of Ahvaz, the center of Khuzestan province with the climate characteristics of very tropical regions; Also, the process of simulating geometric models with the help of Rhino software and climate, thermal and wind flow simulations with the help of Grasshopper software and Ladybug, Honeybee, Butterfly plugins have been done.  The index used to evaluate outdoor thermal comfort in this research is the UTCI index. UTCI index is one of the most comprehensive indices of outdoor thermal comfort. The simulation period is one of the warm weeks of the year (June 9-15) and its average thermal comfort is 38.39 degrees. In the process of reaching a better level of comfort, in the first step, a pedestrian way and two architectural masses were considered, then the influence of the ratio of the height of the masses to the width of the path and its orientation was investigated. In the second step, the type of canopies, their height and width were evaluated and in the third step, the selection of materials for external surfaces was evaluated.
Results and Discussion
In the first part, the height of the mass in two sizes of 4 and 6 meters and the width of the street 6 meters were considered based on the existing physical condition of Ahvaz city. The results showed that taller buildings with constant street width are more successful in improving thermal performance. The orientation of the north south streets creates the best thermal conditions. In the second part, two categories of canopies were defined, including the central canopy and the canopies attached to the mass body. In the optimization process, it was first determined that the height of the central canopy should be lower than the height of the canopies connected to the body, then it was determined that the width of the central canopy has a greater effect on thermal improvement. Also, to limit the desired patterns, based on the better performance of the wind flow, two patterns were introduced. At the end, two general patterns (parallel placement of masses and intersecting placement of masses) were investigated for arrangement of masses and bazaar rows. In the third part, one of the selected patterns of different materials was defined on the outer surfaces. Ceramic, marble, tile, vegetation and wood materials were selected for the sidewalk floor, wall, roof, central canopy and canopy attached to the building.
 
Conclusion
The purpose of this research is to provide thermal comfort conditions for open space; It was also found that radiation control will have the greatest effect in order to achieve thermal comfort. Based on the findings, choosing a higher height for the masses along with choosing a north-south orientation increases the possibility of shadow formation along the route. In the process of simulating canopies, the results show that the lower the height of the central canopy and the wider its width than the canopies connected to the body, the better its performance will be. Finally, it was concluded that among the investigated materials, vegetation has the best thermal efficiency. Also, the best pattern for the arrangement of masses and rows of the bazaar was their parallel arrangement. By comparing the outdoor thermal comfort for a small part of a large group of a market has decreased by 2.94 degrees; In fact, thermal comfort has reached 38.39 degrees to 35.45 degrees.