NUMERICAL AND EXPERIMENTAL-STUDY OF MULTICELLULAR FREE-CONVECTION FLOWS IN AN ANNULAR POROUS LAYER

A numerical and experimental study of free convection two-dimensional (2D) flows in a saturated porous horizontal annulus is reported. The fluid motion, described by 2D Darcy-Boussinesq equations, is obtained from two different numerical methods, namely Fourier-Galerkin and collocation-Chebyshev methods, for high approximations. A comparison of the spectral accuracy of these two methods is carried out. Numerical results indicate that the collocation-Chebyshev method gives a better accuracy especially for the description of the boundary layers developed near the inner and outer cylinders. An experimental study using the Christiansen effect for the visualization of the thermal fields shows the existence of bicellular 2D structures. These structures, which have never been previously observed for concentric cylinders and by means of the Christiansen effect, are in good agreement with numerical results.