抄録
In this paper, the influence of building height on the thermal climate in urban canyons is discussed. The investigation was carried out using a three-dimensional numerical model with high spatial and temporal resolution that simulated the microclimatic changes in urban environments. Model calculations were performed for a typical summer day in Dhaka, Bangladesh, a city in South Asia with a high population density and tropical climate. Two existing urban canyons in the city center with different height to width ratios, and projected canyons with increased building heights were investigated for daytime conditions. The thermal climate was evaluated on the basis of solar radiation, air temperature Ta, and mean radiant temperature Tmrt, mostly along the pedestrian ways. The results show that with respect to daytime thermal climate depending on Ta, greater building height was more advantageous in the case of shallow canyons than for deeper canyons. However, the mean radiant temperature Tmrt on the pedestrian ways was found to be 30−40°C higher than Ta for sunny conditions; however, for shaded conditions, the difference was minimal. Finally, considerable decreases in Tmrt were found in projected canyons compared with existing canyons, especially during those times of the day when there is shade.
