Rotation Induced Stabilization of Thermal Buoyancy Driven Water Flow in a Vertical Rotating Closed Cylinder
An experimental study was carried out here to investigate the stabilization of the thermal buoyancy driven unstable water flow in a vertical closed circular cylinder heated from below by rotating the cylinder about its vertical axis. Results for the time variations of the water temperature at selected locations were obtained for the imposed temperature difference ΔT ranging from 5℃ to 15℃, the cavity rotation rate Ω from 0 to 300 rpm for a cylinder with D＝5cm and H＝10cm and Ω varying 0 to 210 rpm for anothr cylinder with D＝2.5cm and H＝5cm. Based on the results for the time records of the water temperature,t he flow can be stabilized by the cylinder rotation when the rotation rate is in a certain range. The results also indicate that at low rotation rates the amplitude of the termperature oscillation can be larger than that in a stationary cavity. The flow is in time periodic or quasi-periodic oscillation at certain higher rotation rates for the larger cylinder. It was noted that low frequency high amplitude oscillations were found when Ω was in some ranges for the smaller cylinder. significant dependence of the oscillation amplitude with the space is revealed. But the entire flow oscillates at the same frequency when the flow is time periodic. Moreover, nonmonotonic variations of the oscillation frequency with the rotation rate is clearly shown. Flow regime maps delineating the stable and unstable states in the rotating cylinders are also provided.
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