Corner vortex characteristics at the reversal of large scale circulation in turbulent Rayleigh-Bnard convection

The two-dimensional Rayleigh-Bnard convection is calculated by DNS method. A large scale circulation and two corner vortices with reverse rotation are presented in soft turbulent convection, and the reversal phenomenon of the large scale circulation appears. Continuous temperature contour and the streamline chart describe the whole process of the reversal clearly. In the process of the reversal, the changes of the corner vortex size play an important role. Analysis of the corner vortex size change shows that the changes appear violent oscillation in the thermal flow field with the reversal, but only slight pulsation is found without the reversal. Corner vortex size, velocity at the typical position, and the temperature near the angle location in the process of reversal are discussed. The reversal is found to be done in an instant, and the velocity pulse is smaller and the temperature is higher in the corner vortex. The corner vortex size and the vertical velocity on the side wall vary synchronistically before the reversal.