Colloquium # 259

Fluid patterns in thermal convection with rotation

by Dr. Krishna Kumar
Department of Physics
Indian Institute of Technology
Kharagpur, West Bengal

Thursday, 12th May 3:30 PM, Seminar Hall

Chandrasekhar [Proc. R. Soc. (London) A 217, 306 (1953)] investigated the linearized problem of Rayleigh-Bénard (RB) convection in the presence of Coriolis force and showed that onset of convection is always stationary if the Prandtl number Pr > 0.677, and the convection is always oscillatory if Pr < 0.677. Küppers and Lortz analysed the nonlinear problem [J. Fluid. Mech. 35, 609 (1969)] and showed that the onset of thermal convection in RB system rotating uniformly about a vertical axis is always unsteady, if Pr > 0.677 and Taylor number Ta > 2285. A set of rolls is then replaced by another set of rolls inclined with the first set at an angle of 60°. The second set of rolls is again replaced by a new set of rolls making an angle of 60° with the second set. The process is irregular in time and leads to turbulent flow in RBC with rotation. We studied the instabilities in Rayleigh-Bénard convection numerically. We observed several interesting fluid patterns in simulations of low-Prandtl-number RB convection with Coriolis force. The bursting of fluid patterns near the onset of thermal convection is a possibility. Küppers-Lortz instability may or may not occur at the onset of convection in a rotating RB system. Fluid patterns depend on Prandtl number, Taylor number (rotation rate), Rayleigh number (buoyancy force) and the size of containers . Some features of turbulent flow in rotating RB system are also investigated.

About the speaker
Prof. Krishna Kumar is currently working as a professor at Indian Institute of Technology, Kharagpur (IIT-KGP). He joined IIT KGP in 2002. Prior to joining IIT-KGP, he was associated with many Institutes namely Indian Statistical Institute, Kolkata, École-Normale Supérieure de Lyon, France and Indian Institute of Technology, Kanpur (IITK). He pursued his PhD from Department of Physics, Indian Institute of Technology, Kanpur-in 1987. He then continued his research as a Research Associate at IIT-K. Then he moved to University des Saarlandes, Saarland (Germany) as a Postdoctoral Fellow in 1988.
His research interest includes Hydrodynamic Instabilities, Interfacial Waves and Granular Materials. He has published more than fifty papers in peered review journals. He has already supervised seven PhD students. Last but not the least he has received the President of India Award in 1986, Alexander von Humbold Fellowship in 1988 and Geophysical Fluid Dynamics Summer Fellowship in 1991.