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Sharp transitions in rotating turbulent convection
- Source :
- Physical Review Fluids, Physical review fluids, 4(7):074601. American Physical Society, Physical Review Fluids, 4(7):074601, 1-19. American Physical Society, Physical review fluids (Online) 4 (2019). doi:10.1103/PhysRevFluids.4.074601, info:cnr-pdr/source/autori:Alards K.M.J.; Kunnen R.P.J.; Stevens R.J.A.M.; Lohse D.; Toschi F.; Clercx H.J.H./titolo:Sharp transitions in rotating turbulent convection: Lagrangian acceleration statistics reveal a second critical Rossby number/doi:10.1103%2FPhysRevFluids.4.074601/rivista:Physical review fluids (Online)/anno:2019/pagina_da:/pagina_a:/intervallo_pagine:/volume:4
- Publication Year :
- 2019
- Publisher :
- American Physical Society, 2019.
-
Abstract
- In RB convection for fluids with Prandtl number $Pr\gtrsim 1$, rotation beyond a critical (small) rotation rate is known to cause a sudden enhancement of heat transfer which can be explained by a change in the character of the BL dynamics near the top and bottom plates of the convection cell. Namely, with increasing rotation rate, the BL signature suddenly changes from Prandtl--Blasius type to Ekman type. The transition from a constant heat transfer to an almost linearly increasing heat transfer with increasing rotation rate is known to be sharp and the critical Rossby number $Ro_{c}$ occurs typically in the range $2.3\lesssim Ro_{c}\lesssim 2.9$ (for Rayleigh number $Ra=1.3\times 10^9$, $Pr=6.7$, and a convection cell with aspect ratio $\Gamma=\frac{D}{H}=1$, with $D$ the diameter and $H$ the height of the cell). The explanation of the sharp transition in the heat transfer points to the change in the dominant flow structure. At $1/Ro\lesssim 1/Ro_c$ (slow rotation), the well-known LSC is found: a single domain-filling convection roll made up of many individual thermal plumes. At $1/Ro\gtrsim 1/Ro_c$ (rapid rotation), the LSC vanishes and is replaced with a collection of swirling plumes that align with the rotation axis. In this paper, by numerically studying Lagrangian acceleration statistics, related to the small-scale properties of the flow structures, we reveal that this transition between these different dominant flow structures happens at a second critical Rossby number, $Ro_{c_2}\approx 2.25$ (different from $Ro_{c_1}\approx 2.7$ for the sharp transition in the Nusselt number $Nu$; both values for the parameter settings of our present numerical study). When statistical data of Lagrangian tracers near the top plate are collected, it is found that the root-mean-square (rms) values and the kurtosis of the horizontal acceleration of these tracers show a sudden increase at $Ro_{c_2}$.<br />Comment: 16 pages, 9 Figures
- Subjects :
- Fluid Flow and Transfer Processes
Convection
Physics
Prandtl number
Computational Mechanics
Fluid Dynamics (physics.flu-dyn)
FOS: Physical sciences
Rayleigh number
Physics - Fluid Dynamics
Vorticity
01 natural sciences
Nusselt number
010305 fluids & plasmas
Rossby number
Physics::Fluid Dynamics
Boundary layer
symbols.namesake
Modeling and Simulation
0103 physical sciences
Statistics
symbols
HEAT-TRANSPORT
BENARD CONVECTION
VELOCITY
CIRCULATION
010306 general physics
Physics::Atmospheric and Oceanic Physics
Convection cell
Subjects
Details
- Language :
- English
- ISSN :
- 2469990X
- Volume :
- 4
- Issue :
- 7
- Database :
- OpenAIRE
- Journal :
- Physical Review Fluids
- Accession number :
- edsair.doi.dedup.....d3c3709390a1f42c80ebeafbc9e5054b