This work presents large eddy simulation of mixed convection in transient, two-dimensional laminar and turbulent flows in cavities. The Smagorinsky model is employed for the sub-grid treatment. The simulations are based on the finite element solution of the conservation equations, and are presented for Reynolds and Richardson numbers ranging from 400 to 10.000 and from 0.1 to 0.44, respectively. Results for both the laminar and turbulent are compared with those in the literature, leading to maximum deviations of about 5%. In general, the results show a strong dependence of the type of stratification with the fluid dynamics and heat transfer. (C) 2011 Elsevier Ltd. All rights reserved.