Spatial distribution of heat flux and fluctuations in turbulent Rayleigh-Bénard convection (original) (raw)
We numerically investigate the radial dependence of the velocity and temperature fluctuations and of the local heat flux j(r) in a cylindrical Rayleigh-Bénard cell with aspect ratio Γ = 1 for Rayleigh numbers Ra between 2 × 10 6 and 2 × 10 9 at a fixed Prandtl number P r = 5.2. The numerical results reveal that the heat flux close to the side wall is larger than in the center and that, just as the global heat transport, it has an effective power law dependence on the Rayleigh number, j(r) ∝ Ra γ j (r) . The scaling exponent γj(r) decreases monotonically from 0.43 in the center (r ≈ 0) to 0.29 close to the sidewall (r ≈ D/2). The effective exponents at the center and at the side wall agree well with the measurements of Shang et al. (Phys. Rev. Lett. 100, 244503, 2008) and the predictions of Lohse (Phys. Fluids 16, 1070, 2004). Extrapolating our results to large Rayleigh number would imply a crossover at Ra ≈ 10 15 , where the center heat flux would begin to dominate.
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