Dresden 2009 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 16: Fluid dynamics I

DY 16.4: Vortrag

Mittwoch, 25. März 2009, 15:30–15:45, ZEU 255

Stochastic analysis of fractal-generated turbulence — •Robert Stresing¹, J. Christos Vassilicos², and Joachim Peinke¹ — ¹Inst. of Physics, University of Oldenburg, Germany — ²Dep. of Aeronautics & Inst. of Math. Sciences, Imperial College, London, UK

We present a stochastic analysis of turbulence data, which provides access to the joint probability of finding velocity increments at several scales. The underlying stochastic process in form of a Fokker-Planck equation can be reconstructed from given data. Intermittency effects are included. The stochastic process is Markovian for scale separations larger than the Einstein-Markov coherence length, which is closely related to the Taylor microscale.

We extend our analysis to turbulence generated by a fractal square grid. We find that in contrast to other types of turbulence, like free-jet turbulence, the coefficients of the Fokker-Planck equation do not depend on the Reynolds number, and the n-scale statistics are universal over the entire range of Taylor based Reynolds numbers from 150 to 740. Thus we propose to have found a new class of Reynolds-number independent turbulence generated by boundary conditions of a fractal grid.

Ref.: R. Friedrich, J. Peinke, Phys. Rev. Lett 78, 863 (1997); C. Renner, J. Peinke, R. Friedrich, O. Chanal, B. Chabaud, Phys. Rev. Lett 89, 124502 (2002); R. E. Seoud, J. C. Vassilicos, Phys. Fluids 19, 105108 (2007); R. Stresing, J. Peinke, R. E. Seoud, J. C. Vassilicos, in: Progress in Turbulence III, Springer, forthcoming