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Magnetic micro-convection

Magnetic micro-convection, discovered in early 1980s by Maiorov and Cēbers, is a phenomenon that appears on the interface between miscible magnetic and non-magnetic fluids. It is caused by the ponderomotive forces of the self-magnetic field in a magnetic fluid and, above a critical magnetic field, creates an instability.

Experimental images of finger-like patterns of the magnetic micro-convection
   

The magnetic field dependent instability in a Hele-Shaw cell creates a characteristic finger-like pattern, which can be seen above. We try to understand the physics governing this instability by locating characteristic parameters and comparing them between experimental and theoretical results. In collaboration with Dantec Dynamics for the first time we have managed to measure the micro-convective flow field, using a micro Particle Image Velocimetry setup with special image processing algorithms. So far we have shown that our model, which has a Brinkamn term, agrees with experiments both qualitatively and quantitatively and is characterized with a single dimensionless quantity - magnetic Rayleigh number. We are further interested in the peculiarities of the finger growth and applications in microfluidics, for example, e.g. mixing.

Microscopic flows in magnetic micro-convection investigated with Particle Image Velocimetry (PIV)
Experimental image / flow field / vorticity field

Magnetic micro-convection: comparison between experiment and numerical simulation

  • G. Kitenbergs, A. Tatulcenkovs, K. Ērglis, O. Petrichenko, R. Perzynski, A. Cēbers (2015). Magnetic field driven micro-convection in the Hele-Shaw cell: the Brinkman model and its comparison with experiment. Journal of Fluid Mechanics, 774, 170-191. link 
  • F. G. Ergin, B. B. Watz, K. Ērglis, A. Cēbers (2015). Time-resolved velocity measurements in a magnetic micromixer. Experimental Thermal and Fluid Science, 67, 6-13. link
  • G. Kitenbergs, K. Ērglis, R. Perzynski, A. Cēbers (2015). Magnetic particle mixing with magnetic micro-convection for microfluidics. Journal of Magnetism and Magnetic Materials, 380, 227-230. link
  • F. G. Ergin, B. B. Watz, K. Ērglis, A. Cēbers (2014). Modal analysis of magnetic microconvection. Magnetohydrodynamics, 50, 339-352. link
  • K. Ērglis, A. Tatulcenkov, G. Kitenbergs, O. Petrichenko, F. G. Ergin, B. B. Watz, A. Cēbers (2013). Magnetic field driven micro-convection in the Hele-Shaw cell. Journal of Fluid Mechanics, 714, 612–633. link