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 57.6: Talk

Thursday, March 10, 2016, 16:45–17:00, H46

Characterizing multi-scale interaction in turbulence — •Cristian C Lalescu and Michael Wilczek — Max Planck Institute for Dynamics and Self-Organization

Turbulence is a true multi-scale phenomenon with a broad range of interacting spatial and temporal scales. It is well known that in a linear system, unique length scales are associated to well-defined time scales, through a dispersion relation. A naive application of the 1941 Kolmogorov theory also yields a simple characteristic time scale for each given length scale. In the case of real turbulence, however, interactions take place between structures with different characteristic sizes and life times, leading to a continuous spectrum of length scales associated to a time scale and vice versa.

In this work, we aim to characterize these turbulent multi-scale interactions quantitatively. To this end, we identify the time scales relevant for structures of a given size, both from an Eulerian and a Lagrangian perspective. By employing filtering techniques in space and time, we compare turbulent velocity fields containing length scales above a given cutoff-scale with time-filtered fields. Varying the filter widths and times yields a precise picture of the various interactions. In a second step, we generalize the analysis to the Lagrangian frame to study the impact of large- and small-scale fluctuations on turbulent particle transport.