Flow anisotropy in rotating buoyancy-driven turbulence

Rajaei, Hadi; Joshi, Pranav; Kunnen, Rudie; Clercx, Hjh Herman

doi:10.1103/physrevfluids.1.044403

Cited by 8 publications

(23 citation statements)

References 56 publications

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“…This is however not the case in the turbulent flows studied here, since the PDFs of vertical velocity are shown to have wider tails, compared to the Gaussian distribution, in both electromagnetically forced turbulence (EFT) and Rayleigh-Bénard convection (RBC) [22,23]. Moreover, anisotropy and inhomogeneity play a role, especially in the flow close to the horizontal top and bottom plates [22][23][24][25]. Even though the scaling laws, derived in HIT, are shown to be robust [20], it is not clear how anisotropy, inhomogeneity and non-Gaussian velocity statistics influence the curvature and torsion PDFs and whether one recovers these scaling laws in different turbulent flows like, for example, the ones studied here.…”

Section: Introductionmentioning

confidence: 99%

“…For the torsion PDFs, shown in figure 3b, we again observe that the PDF constructed in the non-BL region recovers the HIT scaling law, while the PDF constructed in the BL region reveals a different scaling behavior. So, even though the bulk flow near the top plate is anisotropic [8,25], this does not influence the scaling behavior of the curvature and torsion PDFs. This suggests that as long as viscosity does not play a significant role and as long as the flow is turbulent, the scaling laws found in section II hold.…”

Section: A Non-rotating Turbulencementioning

confidence: 99%

“…For RBC we start these measurements in the cell center, where the flow is closest to HIT [23,25,35]. However we know that, even in the center of the cell, the vertical velocity PDF shows non-Gaussian behavior [23].…”

Section: A Non-rotating Turbulencementioning

confidence: 99%

“…This can be studied by comparing scaling laws, measured in the bulk, to scaling laws measured in the boundary layer at different rotation rates. In the bulk we will moreover consider a measurement volume in the center of the cell and one closer to the top plate, to include effects of anisotropy and inhomogeneity [22][23][24][25]. In this way, we aim at finding a general effect of rotation on the geometry of particle trajectories, not only in different types of turbulent flows, but also closer to, or even inside, the boundary layer.…”

Section: Introductionmentioning

confidence: 99%

“…First, rotation does influence the level of anisotropy and inhomogeneity in RBC and EFT [22][23][24][25]. Second, it changes the length scales of the typical coherent structures in both types of turbulence systems.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 99%

Section: A Non-rotating Turbulencementioning

confidence: 99%

Section: A Non-rotating Turbulencementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geometry of tracer trajectories in rotating turbulent flows

et al. 2017

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Velocity and acceleration statistics in rapidly rotating Rayleigh–Bénard convection

et al. 2018

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Background rotation causes different flow structures and heat transfer efficiencies in Rayleigh–Bénard convection (RBC). Three main regimes are known: rotation-unaffected, rotation-affected and rotation-dominated. It has been shown that the transition between rotation-unaffected and rotation-affected regimes is driven by the boundary layers. However, the physics behind the transition between rotation-affected and rotation-dominated regimes are still unresolved. In this study, we employ the experimentally obtained Lagrangian velocity and acceleration statistics of neutrally buoyant immersed particles to study the rotation-affected and rotation-dominated regimes and the transition between them. We have found that the transition to the rotation-dominated regime coincides with three phenomena; suppressed vertical motions, strong penetration of vortical plumes deep into the bulk and reduced interaction of vortical plumes with their surroundings. The first two phenomena are used as confirmations for the available hypotheses on the transition to the rotation-dominated regime while the last phenomenon is a new argument to describe the regime transition. These findings allow us to better understand the rotation-dominated regime and the transition to this regime.

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Multiple heat transport maxima in confined-rotating Rayleigh–Bénard convection

et al. 2022

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Moderate rotation and moderate horizontal confinement similarly enhance the heat transport in Rayleigh–Bénard convection (RBC). Here, we systematically investigate how these two types of flow stabilization together affect the heat transport. We conduct direct numerical simulations of confined-rotating RBC in a cylindrical set-up at Prandtl number $\textit {Pr}=4.38$ , and various Rayleigh numbers $2\times 10^{8}\leqslant {\textit {Ra}}\leqslant 7\times 10^{9}$ . Within the parameter space of rotation (given as inverse Rossby number $0\leqslant {\textit {Ro}}^{-1}\leqslant 40$ ) and confinement (given as height-to-diameter aspect ratio $2\leqslant \varGamma ^{-1}\leqslant 32$ ), we observe three heat transport maxima. At lower $ {\textit {Ra}}$ , the combination of rotation and confinement can achieve larger heat transport than either rotation or confinement individually, whereas at higher $ {\textit {Ra}}$ , confinement alone is most effective in enhancing the heat transport. Further, we identify two effects enhancing the heat transport: (i) the ratio of kinetic and thermal boundary layer thicknesses controlling the efficiency of Ekman pumping, and (ii) the formation of a stable domain-spanning flow for an efficient vertical transport of the heat through the bulk. Their interfering efficiencies generate the multiple heat transport maxima.

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Flow anisotropy in rotating buoyancy-driven turbulence

Cited by 8 publications

References 56 publications

Geometry of tracer trajectories in rotating turbulent flows

Geometry of tracer trajectories in rotating turbulent flows

Velocity and acceleration statistics in rapidly rotating Rayleigh–Bénard convection

Multiple heat transport maxima in confined-rotating Rayleigh–Bénard convection

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