Vortex flow generated by a magnetic stirrer

Abstract

We investigate the flow generated by a magnetic stirrer in cylindrical containers by optical observations, PIV measurements and particle and dye tracking methods. The tangential flow is that of an ideal vortex outside of a core, but inside downwelling occur with a strong jet in the very middle. In the core region dye patterns remain visible over minutes indicating a pure stirring and mixing property in this region. The results of quantitative measurements can be described by simple formulas in the investigated region of the stirring bar's rotation frequency. The tangential flow turns out to be dynamically similar to that of big atmospheric vortices like dust devils and tornadoes.

Floating Photocatalysts for Passive Solar Degradation of Naphthenic Acids in Oil Sands Process-Affected Water

“…The beakers were then placed on a rooftop outdoors (43 • 28 17.9" N 80 • 32 32.2" W) and exposed to sunlight while stirring at 130 rpm, where a control included OSPW exposed to sunlight in the absence of TiO 2 . The stirring Reynolds number was calculated according to the formula Re = f r 2 υ −1 , where f is the rotational frequency (130 rpm), r is the radius of the stir bar (1.905 cm) and υ is the kinematic viscosity of water [16]. Following solar treatment, the photocatalyst was separated from the OSPW by flotation or centrifugation, retaining the water for analysis (stored at 4 • C in the dark).…”

Tornado model for a magnetised plasma

“…[1][2][3][4][5][6] The magnetic flux tubes with vortical motion are a fundamental model for understanding solar tornadoes, 7-10 astrophysical jets 11,12 and disks around rotating magnetised stars and black holes 13 as well as some configurations of confined laboratory plasmas. [14][15][16] Recent solar observations from the Atmospheric Imaging Assembly (AIA) on board NASA's space-based Solar Dynamics Observatory (SDO) and the Crisp Imaging Spectropolarimeter (CRISP) on the ground-based, Swedish 1-m Solar Telescope have generated a lot of interest in solar magnetic tornadoes as possible channels for energy transfer into the solar corona. 9,10 The acoustic gravity tornadoes can also appear in the form of twisted density structures.…”

Investigations on the influence of phosphonates in dispersing iron oxide (rust) by polymeric additives for industrial water applications

“…In a typical test, six experiments were run simultaneously using a gang-stirrer at 110 revolutions per minute (superficial fluid velocity 1.22 ms -1 , or for the experimental setup the Reynolds number was 9778) [17]. At known time intervals transmittance readings (%T) were taken with a Brinkmann® Probe Colorimeter equipped with a 420 nm filter.…”