{
  "id": "1205.0108",
  "version": "v1",
  "published": "2012-05-01T08:25:29.000Z",
  "updated": "2012-05-01T08:25:29.000Z",
  "title": "Heat transport by turbulent Rayleigh-Bénard convection for $\\Pra\\ \\simeq 0.8$ and $3\\times 10^{12} \\alt \\Ra\\ \\alt 10^{15}$: Aspect ratio $Γ= 0.50$",
  "authors": [
    "Guenter Ahlers",
    "Xiaozhou He",
    "Denis Funfschilling",
    "Eberhard Bodenschatz"
  ],
  "comment": "44 pages, 18 figures, submitted to NJP",
  "categories": [
    "physics.flu-dyn"
  ],
  "abstract": "We report experimental results for heat-transport measurements, in the form of the Nusselt number \\Nu, by turbulent Rayleigh-B\\'enard convection in a cylindrical sample of aspect ratio $\\Gamma \\equiv D/L = 0.50$ ($D = 1.12$ m is the diameter and $L = 2.24$ m the height). The measurements were made using sulfur hexafluoride at pressures up to 19 bars as the fluid. They are for the Rayleigh-number range $3\\times 10^{12} \\alt \\Ra \\alt 10^{15}$ and for Prandtl numbers \\Pra\\ between 0.79 and 0.86. For $\\Ra < \\Ra^*_1 \\simeq 1.4\\times 10^{13}$ we find $\\Nu = N_0 \\Ra^{\\gamma_{eff}}$ with $\\gamma_{eff} = 0.312 \\pm 0.002$, consistent with classical turbulent Rayleigh-B\\'enard convection in a system with laminar boundary layers below the top and above the bottom plate. For $\\Ra^*_1 < \\Ra < \\Ra^*_2$ (with $\\Ra^*_2 \\simeq 5\\times 10^{14}$) $\\gamma_{eff}$ gradually increases up to $0.37\\pm 0.01$. We argue that above $\\Ra^*_2$ the system is in the ultimate state of convection where the boundary layers, both thermal and kinetic, are also turbulent. Several previous measurements for $\\Gamma = 0.50$ are re-examined and compared with the present results.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2012-05-01T08:25:29.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "turbulent rayleigh-bénard convection",
      "aspect ratio",
      "heat transport",
      "classical turbulent rayleigh-benard convection",
      "laminar boundary layers"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/1367-2630/14/10/103012",
      "journal": "New Journal of Physics",
      "year": 2012,
      "month": "Oct",
      "volume": 14,
      "number": 10,
      "pages": 103012
    },
    "note": {
      "typesetting": "TeX",
      "pages": 44,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2012NJPh...14j3012A"
    }
  }
}