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Radial boundary layer structure and Nusselt number in Rayleigh–Bénard convection

  • RICHARD J. A. M. STEVENS (a1), ROBERTO VERZICCO (a2) and DETLEF LOHSE (a1)
Abstract

Results from direct numerical simulation (DNS) for three-dimensional Rayleigh–Bénard convection in a cylindrical cell of aspect ratio 1/2 and Prandtl number Pr=0.7 are presented. They span five decades of Rayleigh number Ra from 2 × 106 to 2 × 1011. The results are in good agreement with the experimental data of Niemela et al. (Nature, vol. 404, 2000, p. 837). Previous DNS results from Amati et al. (Phys. Fluids, vol. 17, 2005, paper no. 121701) showed a heat transfer that was up to 30% higher than the experimental values. The simulations presented in this paper are performed with a much higher resolution to properly resolve the plume dynamics. We find that in under-resolved simulations the hot (cold) plumes travel further from the bottom (top) plate than in the better-resolved ones, because of insufficient thermal dissipation mainly close to the sidewall (where the grid cells are largest), and therefore the Nusselt number in under-resolved simulations is overestimated. Furthermore, we compare the best resolved thermal boundary layer profile with the Prandtl–Blasius profile. We find that the boundary layer profile is closer to the Prandtl–Blasius profile at the cylinder axis than close to the sidewall, because of rising plumes close to the sidewall.

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Corresponding author
Email address for correspondence: r.j.a.m.stevens@tnw.utwente.nl
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Journal of Fluid Mechanics
  • ISSN: 0022-1120
  • EISSN: 1469-7645
  • URL: /core/journals/journal-of-fluid-mechanics
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Type Description Title
VIDEO
Movies

Stevens et al. supplementary movie
Temperature field at mid height for the simulations at Ra = 2 x 109, Pr = 0.7, and G = 0.5 with grid resolution 129 x 65 x 257. The dimensionless time is indicated in the top of the movie. Note that in this low resolution simulation the smoothness of the solution is insufficient to represent all flow dynamics observed in a high resolution simulation.

 Video (3.7 MB)
3.7 MB
VIDEO
Movies

Stevens et al. supplementary movie
Temperature field at mid height for the simulations at Ra = 2 x 109, Pr = 0.7, and G = 0.5 with grid resolution 193 x 65 x 257. The dimensionless time is indicated in the top of the movie.

 Video (3.7 MB)
3.7 MB
VIDEO
Movies

Stevens et al. supplementary movie
Temperature field close to the bottom plate for the simulations at Ra = 2 x 109, Pr = 0.7, and G = 0.5, with grid resolution 193 x 65 x 257 (heights: 0.0021L, 0.0049L, 0.0079L, 0.0111L, and here lqsl=0.0059L). The dimensionless time is indicated in the top of the movie.

 Video (3.8 MB)
3.8 MB
VIDEO
Movies

Stevens et al. supplementary movie
Temperature field close to the bottom plate for the simulations at Ra = 2 x 109, Pr = 0.7, and G = 0.5, with grid resolution 129 x 65 x 257 (heights: 0.0021L, 0.0049L, 0.0079L, 0.0111L, and here lqsl=0.0056L). The dimensionless time is indicated in the top of the movie. Note that in this low resolution simulation the smoothness of the solution is insufficient to represent all flow dynamics observed in a high resolution simulation.

 Video (3.8 MB)
3.8 MB
VIDEO
Movies

Stevens et al. supplementary movie
Temperature field close to the bottom plate for the simulations at Ra = 2 x 109, Pr = 0.7, and G = 0.5, with grid resolution 385 x 97 x 385 (heights: 0.0020L, 0.0044L, 0.0077L, 0.0112L, and here lqsl=0.0059L). The dimensionless time is indicated in the top of the movie.

 Video (3.7 MB)
3.7 MB
VIDEO
Movies

Stevens et al. supplementary movie
Temperature field at mid height for the simulations at Ra = 2 x 109, Pr = 0.7, and G = 0.5 with grid resolution 385 x 97 x 385. The dimensionless time is indicated in the top of the movie.

 Video (3.7 MB)
3.7 MB

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