Dual vortex breakdown in a two-fluid confined flow

Naumov, I. V.; Sharifullin, B. R.; Tsoy, M. A.; Shtern, V. N.

doi:10.1063/5.0012156

Cited by 24 publications

(17 citation statements)

References 10 publications

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“…Since the bubble VB onset maps for two fluids are unknown, a new visualization technique was used to determine the boundaries of the realized regimes. The track visualization system implements the adaptive real-time track visualization technique developed and tested by the authors 21 , 24 . Digital filtering based on averaging with a sliding window and subtraction of the static background were used to increase the signal-to-noise ratio, making it possible to observe low-contrast movements of light-scattering particles in a wide dynamic range even in the presence of significant background illumination.…”

Section: Experimental Setup and Measurement Equipmentmentioning

confidence: 99%

Dual vortex breakdown in a two-fluid whirlpool

Skripkin

Sharifullin

Naumov

et al. 2021

Sci Rep

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Looking for an optimal flow shape for culture growth in vortex bioreactors, an intriguing and impressive structure has been observed that mimics the strong swirling flows in the atmosphere (tornado) and ocean (waterspout). To better understand the flow nature and topology, this experimental study explores the development of vortex breakdown (VB) in a lab-scale swirling flow of two immiscible fluids filling a vertical cylindrical container. The rotating bottom disk drives the circulation of both fluids while the sidewall is stationary. The container can be either sealed with the still top disk (SC) or open (OC). As the rotation strength (Re) increases, a new circulation cell occurs in each fluid—the dual VB. In case SC, VB first emerges in the lower fluid at Re = 475 and then in the upper fluid at Re = 746. In case OC, VB first emerges in the upper fluid at Re = 524 and then in the lower fluid at Re = 538. The flow remains steady and axisymmetric with the interface and the free surface being just slightly deformed in the studied range of Re. Such two-VB swirling flows can provide efficient mixing in aerial or two-fluid bioreactors.

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Section: Experimental Setup and Measurement Equipmentmentioning

confidence: 99%

Dual vortex breakdown in a two-fluid whirlpool

Skripkin

Sharifullin

Naumov

et al. 2021

Sci Rep

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“…Vortex breakdown occurs when the swirl intensity exceeds a certain threshold and is referred to as an abrupt change in the structure of a vortex core 15 . Different forms of vortex breakdown have been reported, and all of them have several common features, such as an adverse pressure gradient along the streamwise direction, a stagnation point followed by a highly turbulent region of reverse flow further downstream, and a jet-like axial velocity profile upstream and a wake-like velocity profile downstream of the breakdown location [16][17][18] . The two most common ones among those different types of breakdown are the asymmetrical spiral type and the nearly axisymmetrical bubble type.…”

Section: Introductionmentioning

confidence: 99%

Determination of single and double helical structures in a swirling jet by spectral proper orthogonal decomposition

Zhang

Vanierschot

2021

Physics of Fluids

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This paper studies the coherent structures found in an annular swirling jet flow undergoing vortex breakdown with control parameters the Reynolds number Re=8500 and the swirl number Sw=0.38. The flow field is simulated using the large eddy simulation (LES) method with a dynamic k model. The first-and second-order statistics of the velocity fields are compared to tomographic particle image velocimetry measurements of the same flow configuration to validate the numerical simulation. The fast Fourier transform of the sampled velocity and pressure signals indicates a precessing vortex core with a frequency of 22 Hz. This frequency is in line with the one detected by spectral proper orthogonal decomposition (SPOD), which is utilized to identify the coherent structures in the near-field region of the swirling flow in the present work. In detail, apart from the single helical structure usually found in swirling flows, a double helix, rarely observed in turbulent swirling jets, is also identified. This structure is not a second-order harmonic mode of the single one as shown by statistical analysis of the mode temporal coefficients. Moreover, the calculation of energy production shows that this coherent precessing motion extracts energy from the mean flow field in the wake behind the bluff-body and in the break up region of the vortex.

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“…The main difference between our CHP and traditional rotating cylindrical heat pipes [3,4] is that in our case, the convection of the working fluid is not free, but forced. At that, in the case of two immiscible media, at small swirls of the cold disk, the vortex motion of the liquid adjacent to the cold disk forms the circulation motion of the second liquid adjacent to the hot surface, as it was studied in detail in [5][6][7] for the isothermal case.…”

Section: Introductionmentioning

confidence: 99%

Heat transfer in a centrifugal vortex tube

Gorelikov

Naumov

Tsoy

et al. 2021

J. Phys.: Conf. Ser.

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The results of an experimental study of the heat flux in a model of a centrifugal vortex apparatus with a lower rotating disk are presented. An experiment considered three cases at a distance between the disks H=R/2 and H=R: “water”, “water-air”, and “water-oil”. Using the colorimetric method, the dependence of the heat flux on Reynolds is shown. The case “water-air” was chosen to evaluate the contribution to heat exchange from the thermocapillary effect (Marangoni) at high Re. For the case of two immiscible liquids of different densities (water-oil), the effect of “centrifugal levitation” is found.

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Dual vortex breakdown in a two-fluid confined flow

Cited by 24 publications

References 10 publications

Dual vortex breakdown in a two-fluid whirlpool

Dual vortex breakdown in a two-fluid whirlpool

Determination of single and double helical structures in a swirling jet by spectral proper orthogonal decomposition

Heat transfer in a centrifugal vortex tube

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