  Natural ventilation is gaining popularity in response to an increasing demand
for a sustainable and healthy built environment, but the design of a naturally
ventilated building can be challenging due to the inherent variability in the
operating conditions that determine the natural ventilation flow. Large-eddy
simulations (LES) have significant potential as an analysis method for natural
ventilation flow, since they can provide an accurate prediction of turbulent
flow at any location in the computational domain. However, the simulations can
be computationally expensive, and few validation and sensitivity studies have
been reported. The objectives of this study are to validate LES of wind-driven
cross-ventilation and to quantify the sensitivity of the solution to the grid
resolution and the inflow boundary conditions. We perform LES for an isolated
building with two openings, using three different grid resolutions and two
different inflow conditions with varying turbulence intensities. Predictions of
the ventilation rate are compared to a reference wind-tunnel experiment
available from literature, and we also quantify the age of air and ventilation
efficiency. The results show that a sufficiently fine grid resolution is needed
to provide accurate predictions of the detailed flow pattern and the age of
air, while the inflow condition is found to affect the standard deviation of
the instantaneous ventilation rate. However, for the cross-ventilation case
modeled in this paper, the prediction of the mean ventilation flow rate is very
robust, showing negligible sensitivity to the grid resolution or the inflow
characteristics.
