UMR 5672

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High precision results for turbulence

Joachim Peinke (Carl-von-Ossietzky University Oldenburg, Germany)
When Nov 23, 2018
from 02:00 PM to 03:00 PM
Where room 116
Attendees Joachim Peinke
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One of the drawbacks of turbulence research is that high precision results are rare or even missing. In this presentation possibilities to overcome this drawback will be discussed.  Two examples will be discussed. First the transition to turbulence. Here we found from PIV measurements on the suction side of an airfoil, that the laminar separation bubble can be characterised quite accurately by the laws of directed percolation, as proposed by Y. Pomeau (1986). Based on the universal scaling exponents of directed percolation the transition point can be determined with an accuracy of 10^-4.
The second example concerns the statistical properties of fully developed turbulence. Setting the turbulent cascades in the framework of non-equilibrium thermodynamics, it has been found that the integral fluctuations theorem is valid for the turbulent cascade. In recent works a precision of the fulfilment of the integral fluctuation theorem better than 10^-4 could be worked out.  The fulfilment of the integral fluctuation theorem can be used to assess the validity of different cascades models for given experimental data, furthermore this fulfilment is based on a multipoint characterisation of turbulence including a three point closure.
 
Citations 
Y. Pomeau, Front Motion, Metastability and Subcritical Bifurcations in Hydrodynamics, Physica D (Amsterdam) 23, 3 (1986).
D. Traphan, T. Wester , G. Gülker, J. Peinke, P. Lind : Directed percolation model captures onset of a laminar separation bubble, Phys Rev X 8, 021015 (2018)
N. Reinke, D. Nickelsen, and J. Peinke : On universale features of the turbulent cascade and its non-equilibrium thermodynamic process, J. Fluid Mech.  848, 117–153 (2018).