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DY: Fachverband Dynamik und Statistische Physik

DY 57: Focus Session: Turbulence - From Pattern Formation to Stochastic Disorder

DY 57.1: Hauptvortrag

Donnerstag, 10. März 2016, 15:00–15:30, H46

The Transition to the Ultimate State in Turbulent Thermal Convection — •Eberhard Bodenschatz — Max Planck Institut für Dynamik und Selbstorganisation, Göttingen, Deutschland

We report measurements of turbulent Rayleigh-Bénard convection in three cylindrical samples with the aspect ratios (diameter/height) Γ = 1.00, 0.50 and 0.33. All samples had the same diameter D = 1.1m, but different heights L. Compressed sulfur hexafluoride gas (SF₆) at pressures up to 19 bars was used as the fluid at the Göttingen Turbulence Facility (see www.EuHIT.org) The measurements were conducted over the Rayleigh-number range 10¹².3ex<-.75em1ex∼ Ra.3ex<-.75em1ex∼ 4 × 10¹⁵ and for Prandtl numbers Pr near 0.8. In three independent measurements, namely global heat transport, local turbulent Reynolds number, and large scale circulation dynamics, we observed as a function of Rayleigh number a transition over a range of Ra from the classical regime to a regime that can be considered ultimate. Consequences thereof will be discussed and so will be the influence of rotation.

The work was conducted with Guenter Ahlers, Denis Funfschilling, Dennis van Gills, Xiaozhou He, Holger Nobach, and Stephan Weiss.