Examining the role of water channels in enhancing pedestrian thermal comfort of urban alleyways

The impact of an alleyway's aspect ratio on pedestrian thermal comfort has been extensively studied worldwide. However, there is a lack of research on the impact of water channels within an alleyway on thermal comfort. Several traditional villages in hot and arid areas have water channels that can lower temperatures through evaporative cooling while raising relative humidity, which influences thermal comfort negatively. Conducting research is necessary to understand such cases. In this paper, the evaporation from the free surface flow of water channels inside alleyways with varied aspect ratios (AR) is numerically simulated using the CFD approach and the volume of fluid (VOF) methodology to simulate free surface flow. Thermal comfort was predicted using Steadman's apparent temperature equation (Steadman 1994). The lowest apparent temperature was found in the deep alleyways, and the difference between shallow and deep alleyways can reach 1.2 oC. Increasing the wind speed from 1 to 10 m/s decreased the apparent temperature by 5 oC. The relative humidity in deep alleyways is higher than in shallow ones with a difference of around 2%. The drop in air temperature due to evaporative cooling was evident in all cases, but the highest drop was in deep alleyways (5 oC) compared to shallow alleyways (3oC). It is concluded that despite the higher relative humidity, the deep alleyways are more suitable for urban fabrics under hot and arid conditions due to the lower apparent temperatures.