Nusselt number measurements for turbulent Rayleigh-Benard convection

We present high-precision measurements of the Nusselt number N as a function of the Rayleigh number R for a cylindrical sample of water (Prandtl number = 4.4) of height L = 50 cm and aspect ratio Gamma = D/L = 1 (D is the diameter) over the range 3 X109 < R < 1 x 1011. Results were obtained wi...

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Veröffentlicht in:Bulletin of the American Physical Society 2004-03, Vol.49 (1)
Hauptverfasser: Ahlers, Guenter, Nikolaenko, Alexei
Format: Artikel
Sprache:eng
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Zusammenfassung:We present high-precision measurements of the Nusselt number N as a function of the Rayleigh number R for a cylindrical sample of water (Prandtl number = 4.4) of height L = 50 cm and aspect ratio Gamma = D/L = 1 (D is the diameter) over the range 3 X109 < R < 1 x 1011. Results were obtained with both Aluminum (conductivity l_p = 170 W/m K) and Copper (l_p = 400 W/m K) top and bottom plates. The results with Aluminum plates fall significantly below those obtained with Copper plates, thus confirming qualitatively the prediction by Verzicco that plates of finite conductivity diminish the heat transport in the fluid. The Nusselt number N_infty is estimated by fitting both data sets to an effective powerlaw for N_infty multiplied by a correction factor f(X) which depends on the ratio X of the thermal resistance of the fluid to that of the plates as suggested by Verzicco. The result is consistent with the structure of the Grossmann-Lohse (GL) model, but will require an adjustment of the model parameters. Near R = 1011, the effective exponent gamma_eff = 0.325 of N_infty almost has reached the asymptotic value 1/3 of the GL model for our Prandtl number.
ISSN:0003-0503