Ventilation naturelle d'un local par une grande ouverture extérieure : Calcul à l'aide d'un code de champ

This paper is dedicated to the numerical study of natural ventilation in a room through a large external opening using the CFD code Fluent. Bidimensional numerical simulations are performed for wind speeds up to 5.55 m·s−1 (20 km·h−1). We propose a two-step solution procedure with grid refinement. When combined with appropriate thermal boundary conditions, this technique appears very efficient at limiting local convergence problems. Through an analysis of the flow pattern in the cavity, we qualitatively explain those results and define a critical Archimedes number. Calculated air change rates are compared to values deduced from empirical correlations of the literature. Agreement is in general poor, which can be explained by the differences between the conditions of our simulations and those of the experiments that lead to those correlations. However, from our simulations, we derived very clear correlations between the air change coefficient and the Archimedes number. In the last part, our results are compared with published data from two experiments. Agreement, in terms of air change coefficient, is within 26 % on average with the Porto test cell data which is closest to our numerical conditions. One should be careful about the transposition of our results to different ventilation scenarios.