Vortex structure in rotating Rayleigh-Bénard convection

Vorobieff, Peter; Ecke, Robert E.

doi:10.1016/s0167-2789(98)00118-3

Cited by 40 publications

(38 citation statements)

References 13 publications

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“…An important topic for future study is the intricate interplay between these vortices and the thermal boundary layer which was raised earlier [4,11,12,32] but remains an open question. Also recent work on the enhancement of heat transport by rotation [7] suggests a diminishing effect at higher Ra, further suggesting that increased Ra would also be of interest in understanding the thermal boundary layer interactions with vortical structures.…”

Section: Discussionmentioning

confidence: 99%

“…The situation is quite different for rotation with Ekman pumping of the boundary layers. One picture, supported by numerical simulation [4] and by lateral velocity experiments [11,32] in rotating convection, is of an overall vortical motion consisting of lateral flow towards the vortex core but with the possibility of radially outward flow at the vortex core. This circulation pattern would draw bulk fluid into the boundary layer at the core and pump boundary layer fluid into the bulk around some vortex radius.…”

Section: A Bulk Temperature: Fluctuations and Mean Gradientmentioning

confidence: 92%

“…As rotation forcing increases, as measured by decreasing Ro, the nature of the boundary layer appears to change, leading to modification of the distribution of temperature fluctuations [4,28] and to enhanced heat transport at moderate Ra and for Pr > 2 [1,5,7,8]. The form of localized disturbances of the boundary layer becomes increasingly vortical for Ro < 1 [3,4,11,25,31], and the enhancement of heat transport has been attributed to Ekman pumping at the top and bottom boundaries owing to rotation [3,4,7,11,32]. Note that the absence of Ekman layers in rotating convection for free-slip conditions still leads to a crossover from weak turbulence near onset to stronger rotating turbulence farther from the onset of convection [33].…”

Section: Introductionmentioning

confidence: 99%

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Local temperature measurements in turbulent rotating Rayleigh-Bénard convection

Liu

Ecke

2011

Phys. Rev. E

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We present local temperature measurements of turbulent Rayleigh-Bénard convection with rotation about a vertical axis. The fluid, water with Prandtl number about 6, was confined in a cell with a square cross section of 7.3 × 7.3 cm 2 and a height of 9.4 cm. Temperature fluctuations and boundary-layer profiles were measured for Rayleigh numbers 1 × 10 7 < Ra < 5 × 10 8 and Taylor numbers 0 < Ta < 5 × 10 9 . We present statistics of the temperature field measured by a single thermistor located along the vertical centerline of the cell or by an array of thermistors distributed laterally from that centerline. The statistics include the mean temperature, standard deviation, skewness, and the probability distribution functions at various locations in the cell, especially near and inside the thermal boundary layer. The effects of rotation on these quantities are discussed including the presence of a rotation-dependent mean vertical temperature gradient, the negative skewness of temperature fluctuations in the boundary layer, and the horizontal homogenization of temperature.

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Section: Discussionmentioning

confidence: 99%

Section: A Bulk Temperature: Fluctuations and Mean Gradientmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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Local temperature measurements in turbulent rotating Rayleigh-Bénard convection

Liu

Ecke

2011

Phys. Rev. E

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“…For Ek 1.8·10 −4 rotation starts to play an important role, due to the development of vertically aligned vortical plumes [7,8]. The length scale of these vortical structures, L, is known to decrease with increasing rotation rate [38,39]. This decrease is moreover expected to scale as L ∼ Ek 1/3 [40,41].…”

Section: B Rotating Turbulencementioning

confidence: 99%

Geometry of tracer trajectories in rotating turbulent flows

et al. 2017

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The geometry of passive tracer trajectories is studied in two different types of rotating turbulent flows; rotating Rayleigh-Bénard convection (RBC; experiments and direct numerical simulations) and rotating electromagnetically forced turbulence (EFT; experiments). This geometry is fully described by the curvature and torsion of trajectories and from these geometrical quantities we can subtract information on the typical flow structures at different rotation rates. Previous studies, focusing on non-rotating homogeneous isotropic turbulence (HIT), show that the probability density functions (PDFs) of curvature and torsion reveal pronounced power laws. However, the set-ups studied here involve inhomogeneous turbulence and in RBC the flow near the horizontal plates is definitely anisotropic. We want to investigate how the typical shapes of the curvature and torsion PDFs, including the pronounced scaling laws, are influenced by this level of anisotropy and inhomogeneity and how this effect changes with rotation. A first effect of rotation is observed as a shift of the curvature and torsion PDFs towards higher values in the case of RBC and towards lower values in the case of EFT. This shift is related to the length scale of typical vortical structures that decreases with rotation in RBC, but increases with rotation in EFT, explaining the opposite shifts of the curvature (and torsion) PDFs. A second remarkable observation is that in RBC the HIT scaling laws are always recovered, as long as the boundary layer (BL) is excluded. This suggests that these scaling laws are very robust and hold as long as we measure in the turbulent bulk. In the BL of the RBC cell, however, the scaling deviates from the HIT prediction for lower rotation rates. This scaling behavior is found to be consistent with the coupling between the boundary layer dynamics and the bulk flow, that changes under rotation. In particular, it is found that the active coupling of the Ekman-type boundary layer with the bulk flow suppresses anisotropy in the BL region for increasing rotation rates.

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“…Only very few experiments involving in situ velocity measurements in rotating convection are reported in the literature [3][4][5]. In these studies a fluid seeded with tracer particles was illuminated with a sheet of light.…”

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confidence: 99%