Effect of various gable roof pitches and obstacle positions on natural ventilation performance for an isolated building using CFD

• Main Authors: Zobaied, A. A., Moey, L. K., Tai, V. C., Go, T. F., Ng, J. Y.
• Format: Conference Proceeding
• Language: English
• Subjects: Air flow; Barriers; Coefficients; Computational fluid dynamics; External pressure; Gables; Internal pressure; K-omega turbulence model; Numerical analysis; Slopes; Turbulence models; Ventilation
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/5.0165399

A gable roof with four various roof pitches namely 15°, 25°, 35° & 45° with varying internal obstacle positions of 20, 40, 50, 60 & 80 mm from windward wall of the building were investigated to study the effect on the airflow of an isolated naturally ventilated building. Numerical analysis based on CFD steady RANS equations with SST k-ω turbulence model was deployed in this study. Three parameters namely streamline of normalized velocity, pressure coefficient and ventilation rate were the focus in this research. Based on the obtained simulation results, the streamline shows that velocity has increased at the windward and leeward openings with the presence of a higher roof pitch due to the external and internal pressure difference. The corresponding changes in obstacle position on the other hand leads to larger recirculation of air flow in front of the obstacle, and also an increase in pressure coefficient inside the building because obstacle position adjacent to the outlet trapped more air. Pressure coefficient inside the building reduces with the steepness of roof pitch due to increasing internal velocity. The 45° gable roof pitch and the obstacle position at 50 mm was found to have the highest ventilation rate at 0.007 m3/s. Thus, airflow behaviour and characteristics are clearly reliant on roof pitch and internal obstacle position. Therefore, it has summarised that a steeper roof pitch and an internal obstacle position neither very close to the inlet nor to the outlet of a gable roof building, resulting in higher ventilation rate.