Computational Fluid Dynamics Simulation of High-Resolution Spatial Distribution of Sensible Heat Fluxes in Building-Congested Area

Urban areas consist of various land cover types, with a high proportion of artificial surfaces among them. This leads to unfavorable thermal environments in urban areas. Continuous research on the thermal environment, specifically on the sensible heat flux (Q_h), has been conducted. However, previous research has faced temporal, spatial, and resolution limitations when it comes to detailed analysis of sensible heat flux in urban areas. Therefore, in this study, a computational fluid dynamics (CFD) model combined with the LDAPS and the VUCM was developed to simulate Q_h at one-hour intervals over a 1-month period in an urban area with various land cover types. Model validation was performed by comparing it with measurements, confirming the suitability of the model for simulating Q_h. The land cover was categorized into five types: building, road, bare land, grassland, and tree areas. Q_h exhibited distinct patterns depending on the land cover type. When averaging the Q_h distribution over the target period, buildings, roads, and bare land areas showed a predominance of upward Q_h values, while grassland and tree areas displayed dominant downward Q_h values. Additionally, even within the same land cover types, slight Q_h variations were identified based on their surroundings. The averaged Q_h value for building areas was the highest at 36.79 W m⁻², while that for tree areas was −3.04 W m⁻². Moreover, during the target period, the time-averaged Q_h showed that building, road, and bare land areas peaked at 14 LST, while grassland and tree areas exhibited very low Q_h values. Notably, buildings reached a maximum Q_h of 103.30 W m⁻² but dropped to a minimum of 1.14 W m⁻² at 5 LST.