Journal ArticleDOI
Length of near-wall plumes in turbulent convection
Baburaj A. Puthenveettil,G. S. Gunasegarane,Yogesh K. Agrawal,Daniel Schmeling,Johannes Bosbach,Jaywant H. Arakeri +5 more
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TLDR
In this article, the authors present planforms of line plumes formed on horizontal surfaces in turbulent convection, along with the length of plumes measured from these planforms, in a six decade range of Rayleigh numbers (10(5) < Ra < 10(11)) and at three Prandtl numbers (Pr = 0.7, 5.2, 602).Abstract:
We present planforms of line plumes formed on horizontal surfaces in turbulent convection, along with the length of line plumes measured from these planforms, in a six decade range of Rayleigh numbers (10(5) < Ra < 10(11)) and at three Prandtl numbers (Pr = 0.7, 5.2, 602). Using geometric constraints on the relations for the mean plume spacings, we obtain expressions for the total length of near-wall plumes on horizontal surfaces in turbulent convection. The plume length per unit area (L(p)/A), made dimensionless by the near-wall length scale in turbulent convection (Z(w)), remains constant for a given fluid. The Nusselt number is shown to be directly proportional to L(p)H/A for a given fluid layer of height H. The increase in Pr has a weak influence in decreasing L(p)/A. These expressions match the measurements, thereby showing that the assumption of laminar natural convection boundary layers in turbulent convection is consistent with the observed total length of line plumes. We then show that similar relationships are obtained based on the assumption that the line plumes are the outcome of the instability of laminar natural convection boundary layers on the horizontal surfaces.read more
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Journal ArticleDOI
New perspectives in turbulent Rayleigh-Bénard convection.
Francesca Chillà,Jörg Schumacher +1 more
TL;DR: Key emphasis is given to the physics and structure of the thermal and velocity boundary layers which play a key role for the better understanding of the turbulent transport of heat and momentum in convection at high and very high Rayleigh numbers.
Journal ArticleDOI
Boundary layer structure in turbulent Rayleigh-Bénard convection
TL;DR: In this article, the structure of the boundary layers in turbulent Rayleigh-B´ enard convection is studied by means of three-dimensional direct numerical simulations, and the results demonstrate that important assumptions of existing classical laminar boundary layer theories for forced and natural convection are violated, such as the strict two-dimensionalality of the dynamics or the steadiness of the fluid motion.
Journal ArticleDOI
Turbulent Rayleigh-B\'enard convection in spherical shells
TL;DR: In this paper, the authors simulate numerically Boussinesq convection in non-rotating spherical shells for a fluid with a unity Prandtl number and Rayleigh numbers up to $10^9.
Journal ArticleDOI
Turbulent Rayleigh-Bénard convection in spherical shells
TL;DR: In this paper, the authors simulate numerically Boussinesq convection in non-rotating spherical shells for a fluid with a Prandtl number of unity and for Rayleigh numbers up to.
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Selection of efficient solvent in solvent-aided thermal recovery of bitumen
TL;DR: In this paper, a linear stability analysis is presented to study the growth of convective instabilities and determine the onset of the convective dissolution and the initial wavelength of instabilities.
References
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Siegfried Grossmann,Detlef Lohse +1 more
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