3:45 PM - 4:00 PM
[MIS21-02] Experimental investigation of Rayleigh-Benard convection in a fluid
layer with quasi-two-dimensional confinement
Geometric confinement has a large influence on flow structures in Rayleigh-Bénard convection. For example, large scale circulation reverses its flow direction more frequently in thinner convection cells. Confinement also have great effects on convective heat transfer efficiency. Heat flux increases significantly in quasi-two-dimensional geometries, even though the flow is strongly suppressed by the surrounding walls. Geometric confinement brings about great changes in the behavior of convection. We performed experimental study in quasi-two-dimensional Rayleigh-Bénard convection to examine the confinement effects on thermal convective flow.
We conducted visualization experiments using Xanthan-Gum aqueous solution with small temperature dependence of viscosity as the test fluid and highly confined convection cells with rectangular shape as a container. Geometric confinement is characterized by thickness-to-height aspect ratio Γ. We set Γabout 1/8, where the quasi-two dimensional convective flow is realized. Velocity profiles measured by particle image velocimetry to quantify the spatiotemporal dynamics. We observed quasi-two-dimensional roll near the onset of convection. As convection developed with increasing thermal buoyancy, time-periodic oscillations occurred near the side walls. This oscillation coincides with the emergence of vortex structures at the corner. Once the vortex structure appears, the size of the roll structures increases. This fact implies that the vortex structure may play an important role in heat transport in quasi-two-dimensional convection.
We conducted visualization experiments using Xanthan-Gum aqueous solution with small temperature dependence of viscosity as the test fluid and highly confined convection cells with rectangular shape as a container. Geometric confinement is characterized by thickness-to-height aspect ratio Γ. We set Γabout 1/8, where the quasi-two dimensional convective flow is realized. Velocity profiles measured by particle image velocimetry to quantify the spatiotemporal dynamics. We observed quasi-two-dimensional roll near the onset of convection. As convection developed with increasing thermal buoyancy, time-periodic oscillations occurred near the side walls. This oscillation coincides with the emergence of vortex structures at the corner. Once the vortex structure appears, the size of the roll structures increases. This fact implies that the vortex structure may play an important role in heat transport in quasi-two-dimensional convection.