Physics of Fluids - Publications

Non–Oberbeck-Boussinesq effects in two-dimensional Rayleigh-Bénard convection in glycerol

arΧiv
Europhysics Letters 80, 34002 (2007)

Authors

	Kazuyasu Sugiyama
	Enrico Calzavarini
	Siegfried Grossmann
	Detlef Lohse

BibTeΧ

@article{0295-5075-80-3-34002,
  author={K. Sugiyama and E. Calzavarini and S. Grossmann and D. Lohse},
  title={Non–Oberbeck-Boussinesq effects in two-dimensional Rayleigh-Bénard convection in glycerol},
  journal={EPL (Europhysics Letters)},
  volume={80},
  number={3},
  pages={34002},
  url={http://stacks.iop.org/0295-5075/80/i=3/a=34002},
  year={2007},
  abstract={We numerically analyze Non–Oberbeck-Boussinesq (NOB) effects in two-dimensional Rayleigh-Bénard flow in glycerol, which shows a dramatic change in the viscosity with temperature. The results are presented both as functions of the Rayleigh number Ra up to 10 8 (for fixed temperature difference Δ between the top and bottom plates) and as functions of Δ ("non-Oberbeck-Boussinesqness" or "NOBness") up to 50 K (for fixed Ra ). For this large NOBness the center temperature T c is more than 5 K larger than the arithmetic mean temperature T m between top and bottom plate and only weakly depends on Ra . To physically account for the NOB deviations of the Nusselt numbers from its Oberbeck-Boussinesq values, we apply the decomposition of Nu NOB / Nu OB into the product of two effects, namely first the change in the sum of the top and bottom thermal BL thicknesses, and second the shift of the center temperature T c as compared to T m . While for water the origin of the Nu deviation is totally dominated by the second effect (cf. AhlersG. et al ., J. Fluid Mech. , 569 (2006) 409) for glycerol the first effect is dominating, in spite of the large increase of T c as compared to T m .}
}