Swirling Flows Characteristics in a Cylinder Under Effect of Buoyancy

摘要

Thermal buoyancy, induced by injection or by differential heating of a tiny rod is explored to control breakdown in the core of a helical flow driven by the lid rotation of a cylinder. Three main parameters are required to characterize numerically the flow behavior; namely, the rotational Reynolds number?Re, the cavity aspect ratio and the Richardson number?Ri.?Warm injection/rod,?Ri?> 0, is shown to prevent on-axis flow stagnation while breakdown enhancement is evidenced when?Ri?< 0. Results revealed that a bubble vortex evolves into a ring type structure which may remain robust, as observed in prior related experiments or, in contrast, disappear over a given range of parameters (Λh,?Re,?Ri?> 0). Besides, the emergence of such a toroidal mode was not found to occur under thermal stratification induced by a differentially heated rod. Moreover, three state diagrams were established which provide detailed flow characteristics under the distinct and combined effects of buoyancy strength, viscous effects and cavity aspect ratio.