DO: Solar Radiation at Different Hours

Solar Radiation at Different Hours, Discrete Ordinates (DO) Radiation Model

Description

This project simulates the impact of solar radiation on an urban environment using the Discrete Ordinates (DO) radiation model in ANSYS Fluent, focusing specifically on how conditions differ between morning and afternoon hours. The simulation captures how solar angle, intensity, and geographical location together shape heat distribution and thermal comfort across a built urban landscape.

The 3D geometry represents a full urban environment, including houses, trees, and surrounding terrain, meshed using a high-fidelity unstructured grid totaling 2,054,294 cells.

Methodology

Radiation was captured comprehensively using the DO radiation model, paired with solar ray tracing to accurately determine solar position and intensity based on the specific geographical location and time being simulated — Baku, Azerbaijan, at two points on June 21st: 8 AM and 3 PM. A coupled heat transfer approach incorporating conduction, convection, and radiation together was used to capture the full thermal behavior of the scene.

Ambient conditions were set to a free air velocity of 10 m/s and an ambient temperature of 27°C, with material properties assigned appropriately for soil, brick (representing the houses), and wood (representing the trees).

Conclusion

Results include temperature distributions across the urban landscape, radiation heat flux patterns on various surfaces, and a direct comparison between the morning and afternoon conditions, identifying thermally safe zones and shaded areas throughout the scene.

The comparison reveals a maximum temperature difference of 6°C between the two times of day — the morning case peaked at approximately 312 K (39°C), while the afternoon case reached approximately 318 K (45°C). Notably, shaded areas maintained a consistent radiation flux of 50–70 W/m² regardless of the time of day, indicating that shading provides a reliably stable thermal environment even as direct solar conditions shift substantially between morning and afternoon — insight directly relevant to urban heat island mitigation, building orientation strategy, and public space comfort design.