Fluctuating characteristics and rotation induced stabilization of thermal buoyancy driven water flow in a vertical rotating cylinder

Abstract

An experimental study was carried out here to investigate the fluctuating characteristics and stabilization of the thermal buoyancy driven unstable water flow in vertical closed circular cylinders 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 DeltaT ranging from 5 degreesC to 15 degreesC and the cavity rotation rate Ohm from 0 to 300 rpm for a cylinder with diameter D = 5 cm, height H = 10 cm and Ohm varying from 0 to 210 rpm for another cylinder with D = 2.5 cm and H = 5 cm. Based on the data for the time records of the water temperature, the flow suppression by the cylinder rotation causes the time-average temperature distributions along the cylinder axis for high rotation rates to become linear. Besides, the flow can be stabilized by the cylinder rotation when the rotation rate is in certain ranges. Significant dependence of the oscillation amplitude with the space is revealed. But the entire how oscillates at nearly the same frequency when the flow is time periodic. Moreover, non-monotonic variations of the oscillation frequency with the rotation rate are clearly shown. Based on the present data, a flow regime map and correlations delineating the stable and unstable states in the vertical rotating cylinders containing water are also provided. (C) 2001 Elsevier Science Ltd. All rights reserved.