Regensburg 2019 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 18: Fluid physics and turbulence
DY 18.8: Vortrag
Dienstag, 2. April 2019, 12:15–12:30, H20
Laboratory Study of the Bottleneck Effect in ultra-strong Turbulence — •Christian Küchler1, Gregory P. Bewley2, and Eberhard Bodenschatz1,2,3 — 1Max Planck Institute for Dynamics and Self-Organization — 2Cornell University, Ithaca — 3Georg August University Göttingen
The turbulent flows characteristic of the atmosphere as well as many engineering problems, are intrinsically a multi-scale phenomenon. While the large-scale motions depend on the turbulence forcing mechanism, and the small scales are dominated by viscosity, the intermediate scales are believed to depend only on the scale-to-scale energy transfer of kinetic energy. In this inertial range, the turbulence is suspected to follow universal laws, e.g. Kolmogorov’s 1941 scaling of the energy spectrum E(k) ∼ k−5/3. However, deviations from this scaling are commonly observed, possibly revealing more complicated energy transfer mechanisms. We present the first laboratory study of one of these effects, namely the bottleneck effect - a pileup of energy at the transition from inertial to dissipative flow scales. In particular we show the dependence of this phenomenon on the turbulence intensity measured by the Taylor-scale Reynolds number Rλ. For this we devised a technique to examine energy spectra plagued by non-flat frequency responses of the hot-wire anemometer we use to measure flow speed. This is made possible by the unique mosaic active grid in the Variable Density Turbulence Tunnel. The active grid also permits the creation of Rλ>5000, which is unmatched by any well-controlled laboratory flow with experimentally resolvable dissipative scales.