Mechanical coupling of convective rolls in a high prandtl number fluid

Experimental and numerical studies (using the finite element method) were c onducted in a rectangular vessel for a high Prandtl number fluid (Pr = 880 at 25 degrees C). The pattern of convective rolls is perturbed by lateral h eating 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 = 4.6R(c) where R and R-c are the Rayleigh number and its critical value of Benard convection). T he formation of a large roll induced by the lateral heating causes a slight variation in the wave number of the rolls, accompanied by the disappearanc e of pairs of rolls, or single rolls, depending on the boundary conditions at the other small side of the enclosure. In all instances, this disappeara nce respects the mechanical coupling between the rolls. Temperature and vel ocity fields are assessed, as well as the heat transfer. The transient stat es observed during the experimentation are well reproduced by the two-dimen sional numerical model developed for this study.