Lattice Boltzmann Simulation of Natural Convection in an Annulus between a Hexagonal Cylinder and a Square Enclosure

Laminar natural convection in a water filled square enclosure containing at its center a horizontal hexagonal cylinder is studied by the lattice Boltzmann method. The hexagonal cylinder is heated while the walls of the cavity are maintained at the same cold temperature. Two orientations are treated, corresponding to two opposite sides of the hexagonal cross-section which are horizontal (case I) or vertical (case II). For each case, the results are presented in terms of streamlines, isotherms, local and average convective heat transfers as a function of the dimensionless size of the hexagonal cylinder cross-section (0.1≤B≤0.4), and the Rayleigh number (103≤Ra≤106)

Analysis of Turbulent Natural Convection by an Elliptic Relaxation Model in Tall Vertical Cavities with Linear Temperatures on Sidewalls

Turbulent natural convection of air is studied, by the elliptic-relaxation model v^2-f, in a tall vertical cavity whose hot and cold walls are maintained at linear temperatures of slopes γ_1 and γ_2, respectively. The average temperatures of the active walls are located at mid-height of the cavity. Four situations are analyzed, corresponding to γ_1=γ_2=γ (case I), γ_1=-γ_2=γ (case II), γ_1=0 and γ_2=γ (case III), γ_1=γ and γ_2=0 (case IV). These boundary conditions may be more representative or used to control heat transfer for certain systems. The effects of the slope (-1≤γ≤1), the aspect ratio of the cavity (10≤A≤80) and the average Rayleigh number (5×〖10〗^4≤〖Ra〗_m≤〖10〗^6 ) on the streamlines, isotherms, contours of the turbulent kinetic energy, heatlines, local and average Nusselt numbers are investigated. It is shown that the local and average heat transfers of cases III and IV can be deducted from those of cases I and II. The obtained dynamic and thermal fields as well as local and average heat transfers of the studied cases are quite different of those of the classical case corresponding to γ=0. A simplified procedure for calculating the average Nusselt number is also developed for each case

The stability of free convection in a particle-fluid mixture with a free surface

cited By 2International audienceno abstrac

Buoyancy driven convection in a particle-fluid mixture layer heated from below

cited By 2International audienceno abstrac

Numerical simulation of coupeld heat transfer through a concrete hollow brick

The present study aims to investigate coupled heat transfer by natural convection and conduction through a concrete hollow brick. The governing equations for conservation of mass, momentum and energy are discretized by the finite volume approach and solved by the SIMPLE algorithm. The numerical simulations were conducted to investigate the effect of Rayleigh number (103≤ Ra ≤ 107) on the heat transfer and fluid flow within the structure