Prediction of Unsteady Natural Convection within a Horizontal Narrow Annular Space Using the Control-Volume Method

ABSTRACT

Oscillatory natural convection in a narrow horizontal space is investigated numerically using the control-volume method. A parametric study for Rayleigh number is carried out using the power-law scheme and a confrontation with the central-difference scheme is developed. At intermediate values of the Prandtl number, complex interaction between hydrodynamic and thermal instabilities exists. For Pr = 0.2, gradual transitions from monocellular to three-top cell regimes are registered, the phenomenon of coalescence and separation of like-rotating cells is observed, and a subharmonic instability, followed by an early chaotic flow, is depicted. A disagreement between the power-law and the central-difference schemes results exists; the latest ones are in good agreement with the finite-difference method computations. However, the central-difference scheme results suffer from the false diffusion phenomenon.