An experimental study on vortex breakdown in a differentially-rotating cylindrical container

The results of an experimental study of the forced and periodic breakdown of a confined vortex rotating in the opposite direction are presented. The vortex tube consists of two chambers connected by a short conduit through streamlined transitions. The upstream end is closed by a plain wall, and a circular orifice is provided at the downstream end. The swirling flow and the breaker-vortex are generated by introducing varying proportions of air or water through tangential ports located near the upstream and downstream walls of the unit. The cases of single breakdown and periodic breakdown are explored and typical data are presented for each case. Finally, the pros and cons of the two existing transition theories are discussed.

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Numerical study on vortex breakdown in a cylindrical container driven by rotating small disk

The Proceedings of Mechanical Engineering Congress Japan ◽

10.1299/jsmemecj.2020.s05435 ◽

2020 ◽

Vol 2020 (0) ◽

pp. S05435

Author(s):

Koji SUZUKI ◽

Reima IWATSU

Keyword(s):

Vortex Breakdown ◽

Numerical Study ◽

Cylindrical Container ◽

Small Disk

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Topology of vortex breakdown in closed polygonal containers

Journal of Fluid Mechanics ◽

10.1017/jfm.2017.211 ◽

2017 ◽

Vol 820 ◽

pp. 263-283 ◽

Cited By ~ 7

Author(s):

Igor V. Naumov ◽

Irina Yu. Podolskaya

Keyword(s):

Aspect Ratio ◽

Cross Section ◽

Vortex Breakdown ◽

Laser Doppler Anemometry ◽

Reynolds Numbers ◽

Cylindrical Container ◽

Stagnation Points ◽

Aspect Ratios ◽

Particle Visualization ◽

Cross Section Geometry

The topology of vortex breakdown in the confined flow generated by a rotating lid in a closed container with a polygonal cross-section geometry has been analysed experimentally and numerically for different height/radius aspect ratios $h$ from 0.5 to 3.0. The locations of stagnation points of the breakdown bubble emergence and corresponding Reynolds numbers were determined experimentally and numerically by STAR-CCM+ computational fluid dynamics software for square, pentagonal, hexagonal and octagonal cross-section configurations. The flow pattern and velocity were observed and measured by combining seeding particle visualization and laser Doppler anemometry. The vortex breakdown size and position on the container axis were identified for Reynolds numbers ranging from 500 to 2800 in steady flow conditions. The obtained results were compared with the flow structure in the closed cylindrical container. The results allowed revealing regularities of formation of the vortex breakdown bubble depending on $Re$ and $h$ and the cross-section geometry of the confined container. It was found in a diagram of $Re$ versus $h$ that reducing the number of cross-section angles from eight to four shifts the breakdown bubble location to higher Reynolds numbers and a smaller aspect ratio. The vortex breakdown bubble area for octagonal cross-section was detected to correspond to the one for the cylindrical container but these areas for square and cylindrical containers do not overlap in the entire range of aspect ratio.

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