Tue May 24th 2011
10:30
ZH286
Seminar Reorientations and reversals of large-scale circulation in turbulent Rayleigh-Bénard convection
Pankaj Kumar Mishra

Details:

Large Scale Circulation (LSC), also known as `mean wind', appears at large length scales in turbulent Rayleigh-Bénard convection (RBC). It is a coherent structure of the flow in which fluid particle ascends from one side of the wall and descends down from the azimuthally opposite side. It has been observed in laboratory experiments that the vertical plane containing LSC undergoes a diffusive motion in the azimuthal direction of the cylindrical container. Sometimes, in the course of its motion, the plane of the LSC changes by a significant angle. This phenomenon, called the reorientation of the LSC, leads to flow reversal exhibiting a rich dynamical behaviour.

In this talk, we will present a numerical study of the dynamics of the reorientation of the LSC for air (Prandtl number = 0.7) contained in a cylindrical container of aspect ratio one. We propose that the dynamics of LSC in the azimuthal direction is captured quite well by the Fourier mode with the lowest wavenumber. The amplitude and phase of this mode provide a very good estimate of the strength and orientations of LSC, respectively. We observe rotation-led and cessation-led partial as well as full azimuthal reorientation of the large-scale flow as observed in earlier experiments. Finally we will discuss the interesting interplay between the first and higher Fourier modes during cessation-led reorientations.
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The 10th Complex Motion in Fluids 2020
Max Planck Gesellschaft
MCEC
Twente
Centre for Scientific Computing
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