| Wed May 6th 2015 16:00 – 17:00 ZH286 | Seminar | Dynamics of the Large-Scale Flow in Turbulent Convection with Modulated Rotation Sebastian Sterl |
Details:We present measurements of the azimuthal rotation velocity and thermal amplitude of the large-scale circulation (LSC) in turbulent Rayleigh-Bénard convection with modulated rotation. Both quantities exhibit clear oscillations at the modulation frequency. Fluid acceleration driven by oscillating Coriolis force causes an increasing phase lag in the azimuthal velocity when the rate of modulation increases. The applied modulation produces oscillatory boundary layers and the resulting time-varying viscous drag modifies the thermal strength of the circulation periodically.The maximum amplitude of the oscillations of the azimuthal speed is found to occur at a finite modulation frequency. Such a resonance-like phenomenon is interpreted as a result of optimal coupling of the circulation strength to the modulated rotation speed. We show that an extended LSC model with a relaxation time for the circulation strength in response to modulated rotations provides predictions in close agreement with the experimental results. | ||
