Building Simulation: An International Journal

Article Title

CFD simulation of wind and thermal-induced ventilation flow of a roof cavity


ventilated roof cavity, CFD simulation, atmospheric boundary layer, thermal-induced buoyancy


The hygrothermal performance of a ventilated roof cavity is greatly affected by the airflow passing through it. This ventilation flow is mainly driven by the wind pressure difference between openings and the thermal-induced buoyancy. However, the wind effect is not well understood as it is often neglected in previous studies. The present study investigates the properties of such airflows, including the flow pattern, flow regime, and flow rate, using a CFD method. The target building is a large-span commercial building with a low-pitched roof. To study the wind-induced airflows, the onset atmospheric boundary layer wind flow was modelled, and the results were compared with the site-measured data recorded in the literature. To study the thermal-induced buoyancy effects, a roof cavity model found in the literature with experimental data was adopted. The findings show that the flow pattern in the roof cavity varied with the airflow driven factors. The flow separation at the windward eave inlet of the thermally induced flows are more pronounced compared with those of the wind-induced flows. Furthermore, the wind-induced airflows can generate around two times more ventilation flow rate through the roof cavity compared to the thermal-induced airflow. The findings indicate that wind-induced ventilation flows are the dominant factor of the roof cavity ventilation in a large-span, low-pitched building.