Regensburg 2016 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

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

DY 57.8: Talk

Thursday, March 10, 2016, 17:15–17:30, H46

Lagrangian intermittency in an ensemble of Gaussian velocity time series with fluctuating time scales — •Laura Lukassen and Michael Wilczek — Max Planck Institute for Dynamics and Self-Organization, Goettingen

Turbulent velocity fluctuations exhibit intermittency in both, the Lagrangian and Eulerian frame. Here, we focus on the Lagrangian velocity increments whose probability density function shows a transition from a nearly Gaussian shape to highly non-Gaussian shapes for decreasing time lags. This inherent non-Gaussianity poses a challenge for statistical approaches suffering from the closure problem.

Our aim is to derive an analytically tractable model of turbulence which captures the characteristics of turbulence such as intermittency. We discuss the properties of an ensemble of Gaussian velocity time series in which the characteristic time scales of the ensemble members are drawn from an underlying distribution of those scales. Such an ensemble naturally exhibits non-Gaussian statistics as has been demonstrated, e.g., in the context of multifractal modeling. In order to provide a more general approach, our model is based on the characteristic functional which captures the complete statistical information of the ensemble. As a result, non-trivial statistical information such as joint statistics of increments at various scales or joint statistics of acceleration and increments can be obtained. Based on that, we will discuss the potential of formulating novel closures in the framework of our approach.