Computational fluid dynamics of airflow rates for natural ventilation with opposing wind and buoyancy

Department of Architectural Engineering, Graduate School of Engineering, Osaka University, Osaka, Japan

^* Corresponding author: jiang_zitao@arch.eng.osaka-u.ac.jp

Abstract

Wind and buoyancy both play an important role as driving forces of natural ventilation. Previous theoretical analysis has shown that there might be at most three mathematical solutions of airflow rate for a known indoor heat generation rate and wind pressure. However, the most of prior studies only consider the steady state while neglecting the wind turbulence effects. Turbulence was widely proven to be another determinant factor in natural ventilation. In the present study, the steady and unsteady simulation of airflow rates for a full-scale naturally ventilated room with opposing wind and the internal uniform heating floor was conducted. The comparison between Reynolds Averaged Numerical Simulation (RANS) and Large Eddy Simulation (LES) shows when the buoyancy force is stronger than the wind force, the airflow behaviour is different in RANS and LES. The airflow in RANS is nearly unidirectional, however, LES results show the airflow is bidirectional at each opening, which was not reported before.