Two-dimensional large-eddy simulation of turbulent natural convection due to internal heat generation

Two-dimensional numerical simulations of laminar and turbulent natural conv ection in a fluid with internal heat generation in a square cavity are pres ented. The simulations were carried out at Rayleigh numbers 10(6)-10(11) an d Prandtl numbers 0.25 and 0.6. The turbulent fluid motion was captured wit h a large-eddy simulation (LES) model. The Rayleigh-Taylor instabilities at the upper boundary and the Kelvin-Helmholtz instabilities at the side boun daries cause first local and then global transition from laminar to turbule nt motion. Lower Prandtl numbers enhance heat transfer through the bottom r egion, whereas higher Prandtl numbers enhance heat transfer through the upp er region of the simulation domain. The simulations also reveal that the Ra yleigh-Nusselt number relation is not uniformly linear in a log(10)-log(10) diagram. (C) 2001 Elsevier Science Ltd. All rights reserved.