Regensburg 2019 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 18: Fluid physics and turbulence

DY 18.5: Talk

Tuesday, April 2, 2019, 11:15–11:30, H20

Transitions between large-scale flow states in turbulent 3D Kolmogorov flow — •Cristian C Lalescu and Michael Wilczek — Max Planck Institute for Dynamics and Self-Organization, Göttingen

For most turbulent flows in nature, the idealization of statistical homogeneity and isotropy only applies to the small scales. The large scales are typically non-universal with pronounced inhomogeneities resulting from walls, large-scale driving etc. This motivates the investigation of the large-scale structure, turbulent fluctuations as well as their interaction in a canonical flow.

Here we present results on a generalized turbulent Kolmogorov flow in three-dimensional periodic domains with aspect ratios larger than one. The flow is forced on a single Fourier mode and is subject to large-scale friction. The flow develops large-scale vortex patterns similar to two-dimensional Kolmogorov flow, even in the presence of intense three-dimensional small-scale fluctuations. We characterize transitions between different large-scale flow states as the large-scale friction is modified, including a regime reminiscent of noise-suppressed hysteresis. In addition to the large-scale flow features, we address the question of small-scale isotropy in the presence of large-scale anisotropies in this flow. Our results help to clarify the role of fluctuations for transitions in fully developed turbulence.