Destabilization of free convection by weak rotation

• Published in: Journal of fluid mechanics 2011-10, Vol.685, p.377-412
• Main Author: Gelfgat, A. Yu
• Format: Article
• Language: English
• Subjects: Buoyancy-driven instability; Computational fluid dynamics; Convection; Cross-disciplinary physics: materials science; rheology; Crystal growth; Cylinders; Destabilization; Exact sciences and technology; Fluid dynamics; Fluid flow; Fundamental areas of phenomenology (including applications); Growth from melts; zone melting and refining; Heat conductivity; Hydrodynamic stability; Instability; Materials science; Methods of crystal growth; physics of crystal growth; Physics; Prandtl number; Stability; Systems stability; Thermal stratification; Vortices
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/jfm.2011.323

This study offers an explanation of the recently observed effect of destabilization of free convective flows by weak rotation. After studying several models where flows are driven by the simultaneous action of convection and rotation, it is concluded that destabilization is observed in cases where the centrifugal force acts against the main convective circulation. At relatively low Prandtl numbers, this counter-action can split the main vortex into two counter-rotating vortices, where the interaction leads to instability. At larger Prandtl numbers, the counter-action of the centrifugal force steepens an unstable thermal stratification, which triggers the Rayleigh–Bénard instability mechanism. Both cases can be enhanced by advection of azimuthal velocity disturbances towards the axis, where they grow and excite perturbations of the radial velocity. The effect was studied by considering a combined convective and rotating flow in a cylinder with a rotating lid and a parabolic temperature profile at the sidewall. Next, explanations of the destabilization effect for rotating-magnetic-field-driven flow and melt flow in a Czochralski crystal growth model were derived.