Dr. Haim Bau | CURRENT RESEARCH:  Micro and Nano Fluidics | Active Control of Flow Patterns | Molecular Motions
   

Active Control of Flow Patterns

Areas of Research:

People:

Opportunities:

Other Research Areas:

 

 

Active Control of Flow Patterns:

Rayleigh-Benard


RAYLEIGH-BENARD
We are investigating the feasibility of delaying the transition from the no-motion (pure conduction) to the motion state in the Rayleigh-Benard (RB) problem of a fluid layer heated from below and cooled from above. We have chosen this problem for study because the uncontrolled problem has been extensively studied and the phenomena observed are relatively well understood. The RB problem is also of technological importance since it serves as a paradigm for many material processing applications.

In theoretical studies, Tang & Bau (1993a, b, 1994, 1995, and 1998) have shown that with the aid of a feedback controller the critical Rayleigh number for the onset of convection in an infinite horizontal fluid layer can be increased by almost an order of magnitude. Our experiments demonstrated (Tang & Bau, 1998) a more modest success. Currently, we are improving the experiments to bridge the gap between theoretical predictions and experimental observations, investigating the limitations of linear control strategies, and devising non-linear controllers.
The normalized critical Rayleigh (R/1707) and wave (a/3.117) numbers are depicted as functions of the thermal controller's gain (Kp). The solid and dotted curves describe, respectively, loss of stability through a real eigenvalue (exchange of stability) and through a Hopf bifurcation. .  
 

PUBLICATIONS

  • Tang, J., & Bau, H. H., 1993, Stabilization of the No-motion State in Rayleigh-Bénard Convection Through the Use of Feedback Control, Physical Review Letters, 70, 1795-1798.
  • Tang, J., & Bau, H. H., 1993, Feedback Control Stabilization of the No-motion State of a Fluid Confined in a Horizontal, Porous Layer Heated from Below, J. Fluid Mechanics, 257, 485-505.
  • Bau, H., H., 1993, Controlling Chaotic Convection, (an invited paper) in Theoretical and Applied Mechanics 1992, (Proceedings of the XVIIIth International Congress of Theoretical and Applied Mechanics, Haifa, Israel, August 22-28), S. R. Bonder, J. Singer, A. Solan, and Z. Hashin, editors, Elsevier Science Publishers, 187-203.
  • Tang, J., and Bau, H. H., 1994, Stabilization of the No-motion State in the Rayleigh-Bénard Problem, Proceedings Royal Society A, 447, 587-607.
  • Tang, J., and Bau, H. H., 1995, Stabilization of the No-motion State of a Horizontal Fluid Layer Heated from Below with Joule Heating, Trans. ASME-J. Heat Transfer, 117, 329-333.
  • Tang, J., & Bau, H. H., Experiments on the Stabilization of the No-Motion State of a Fluid Layer Heated From Below and Cooled from Above, J. Fluid Mechanics, 363, 153-171, 1998.
  • Tang, J., & Bau, H. H., 1998, Numerical Investigation of the Stabilization of the No-Motion State of a Fluid Layer Heated from Below and Cooled from Above, Physics of Fluids, 10, Issue 7, 1597-1610