Validation of CFD models of urban microclimates under high temperature and humidity conditions during daytime heatwaves in dense low-rise areas

In the midst of the ongoing climate crisis, there is a growing need to study the effects of climate on humans, especially those of the microclimates that surround humans and their activities. Various models have been developed to simulate microclimates, but simulation models for densely populated areas experiencing heat waves have shown an issue with simulating temperatures that were too high compared to actual measurements. To overcome these limitations, this study aimed to develop and validate CFD model based on STAR-CCM+ in order to more accurately simulate the microclimate of dense residential areas. To improve the realistic simulation capability found in existing models, the model was designed to include solar radiation, humidity, ground radiation, longwave radiation exchange, heat storage and evaporation due to various urban surfaces, evapotranspiration from vegetation, convection, and heat transfer from buildings. For validation, comparisons were made between the simulation results and the actual measurements during this time. The results showed that the R 2 value of the model developed in this study increased from 0.86 to 0.91, indicating that the model was able to reproduce the measured results of the target site well. To avoid overfitting the model, the measurement results of the Han River AWS, another AWS operated by the Korea Meteorological Administration near the target site, were input. It was confirmed that the model reproduced the actual measurements of five locations in the target site well. The R 2 of temperature and humidity ranged from 0.96 to 0.98, and wind speed ranged from 0.64 to 0.81. • Developing microclimate CFD model in a large 5 km × 5 km urban area. • Validating explanatory CFD model in high temperature and moisture conditions. • Including of urban factors, incorporating short/longwave, convection and evaporation. • High accuracy simulation with R 2 0.96 to 0.98 to urban heat islands.