Berlin 2015 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 32: Focus Session: Statistics of fully developed turbulence
DY 32.4: Vortrag
Mittwoch, 18. März 2015, 16:00–16:15, BH-N 243
Stochastic description of a turbulent wake — •Nico Reinke and Joachim Peinke — ForWind, Institute of Physics, Carl v. Ossietzky University, Oldenburg, Germany
The presentation will give an insight in our experimental work to fractal generated turbulent flows and especially in the stochastic analysis of this turbulent flow. The stochastic approach allows to characterize the turbulent cascade process in scale r and in different distances x to the grid. This stochastic characterization shows the complexity of the flow and the transition between an non homogenous to a homogenous turbulent flow. To characterize the wake of a fractal grid velocity measurements v(t) (using hot wire anemometer) were performed on the wind tunnel test section center line x → v(t,x). We analysis the wake in terms of velocity increments u(r,x)=v(t+r/<v>,x)−v(t,x). The velocity increments are consider as Markov chain, which is true for r≥ lEM, where lEM is the Einstein-Markov coherence length. The information of the turbulent cascade process is captured in the conditional probability distribution function p(u(r,x)|u(r+δ r,x)), δ r≥ lEM. p(u(r,x)|u(r+δ r,x)) changes for different scales r. This change is describe by the so called Fokker-Planck equation, which is governed by Kramers-Moyal functions D(1)(u(r,x)) and D(2)(u(r,x)). Finally, those functions characterize the turbulent cascade and allow us to understand the wake in scale and in distance to the grid.