Mechanical Coupling of Convective Rolls in a High Prandtl Number Fluid

Abstract

Experimental and numerical studies (using the finite element method) were conducted in a rectangular vessel for a high Prandtl number fluid (Pr = 880 at 25°C). The pattern of convective rolls is perturbed by lateral heating of one of the smaller sides of the box. The wave number of the roll pattern is within a narrow range (±10 percent at R = 4.6RC where R and Rc are the Rayleigh number and its critical value of Be´nard convection). The formation of a large roll induced by the lateral heating causes a slight variation in the wave number of the rolls, accompanied by the disappearance of pairs of rolls, or single rolls, depending on the boundary conditions at the other small side of the enclosure. In all instances, this disappearance respects the mechanical coupling between the rolls. Temperature and velocity fields are assessed, as well as the heat transfer. The transient states observed during the experimentation are well reproduced by the two-dimensional numerical model developed for this study.