abstract
A leeward sawtooth roof building has an inlet opening in the lower level of the windward facade and an
upper-level outlet opening near the roof top, in the leeward facade. Leeward sawtooth roof buildings can
be applied to efficiently ventilate low-rise buildings. Previous studies of the authors showed that the
ventilation potential strongly depends on the roof inclination angle and roof geometry. The current study
focuses on the ventilation flow in single-zone elongated low-rise buildings with a single-span versus
double-span leeward sawtooth roof and different opening ratios. Straight, concave and convex roof geometries
are evaluated. The analysis is performed using 3D steady Reynolds-averaged NaviereStokes
Computational Fluid Dynamics (CFD) simulations with the SST k-u turbulence model. The computational
grid is based on a grid-sensitivity analysis and the simulation results are validated based on Particle
Image Velocimetry (PIV) measurements from literature. For the single-span cases, the convex roof results
in the highest volume flow rate, which is about 8.8% higher than for the concave roof, and 3.5% higher
than the straight roof. A double-span roof performs slightly better than a single-span roof with respect to
ventilation flow rates (below 4.2%) in case of a straight or concave roof, but worse in case of a convex roof
(12%). The internal roof geometry near the outlet opening plays an important role in the ventilation of
the building. Finally, the inlet-to-outlet opening ratio has an important effect on the volume flow rates,
with significantly higher ventilation flow rates for a lower opening ratio.