Experimental and numerical evaluation of wind-driven natural ventilation of a curved roof for various wind angles

Abstract

The paper experimentally and numerically investigates the capability of the semi-cylindrical curved roofs in providing natural ventilation. Extensive measurements around a 1:17 scale model of a typical room with a semi-cylindrical roof have been conducted to determine the pressure and velocity field for gaining the discharge coefficients of apertures. Besides, smoke flow visualization and three-dimensional RANS simulations have been performed to correlate the ventilation characteristics, the induced volumetric airflow rate, and the flow trajectories. The prior studies were carried out on the domed roofs, but in the present study, the focus is on the semi-cylindrical curved roofs. It is found that the natural ventilation performance of the curved roof is profoundly sensitive to the wind angle (i.e. α) so that the extreme ventilation takes place at α = 0°, while the α = 75° - 90° gives the lowest airflow rate. The dependence of the airflow rate on α is attributed to variation in the pressure difference between openings (known as the main driving force) caused by flow acceleration and flow separation. Further increase of α slightly ameliorates the airflow rate, although still not comparable with that of α = 0°. Flow visualization results reveal that the height of the curved roof is a key factor in the enhancement of recirculation flow inside the building. Finally, a comparison discloses that the semi-cylindrical curved roof is prone to enhance the natural ventilation inside buildings as much as the wind-catchers, although presumably is cheaper in terms of the structural costs.