Abstract
Self-organized large-scale flow structures occur in a wide range of turbulent flows. Yet, their emergence, dynamics, and interplay with small-scale turbulence are not well understood. Here, we investigate such self-organized turbulent superstructures in three-dimensional turbulent Kolmogorov flow with large-scale drag. Through extensive simulations, we uncover their low-dimensional dynamics featuring transitions between several stable and meta-stable large-scale structures as a function of the damping parameter. The main dissipation mechanism for the turbulent superstructures is the generation of small-scale turbulence, whose local structure depends strongly on the large-scale flow. Our results elucidate the generic emergence and low-dimensional dynamics of large-scale flow structures in fully developed turbulence and reveal a strong coupling of large- and small-scale flow features.
Highlights
Self-organized large-scale flow structures occur in a wide range of turbulent flows
Superstructures in fully developed turbulence are a widely occurring, dynamically emergent phenomenon. Despite their generic occurrence in a broad range of prototypical flows, the emergence and dynamics of turbulent superstructures, and in particular their interplay with smallscale turbulence, are currently not well understood. These aspects are crucial for developing a low-dimensional description of the large-scale dynamics of fully developed turbulent flows
We here study a prototypical shear flow—a generalized three-dimensional (3D) turbulent Kolmogorov flow, which allows the investigation of turbulent superstructures without the complications imposed by boundaries
Summary
Self-organized large-scale flow structures occur in a wide range of turbulent flows. Yet, their emergence, dynamics, and interplay with small-scale turbulence are not well understood. Our results elucidate the generic emergence and low-dimensional dynamics of large-scale flow structures in fully developed turbulence and reveal a strong coupling of large- and small-scale flow features. We generalize 3D Kolmogorov flow by including a large-scale drag term, which allows the manipulation of the range of scales on which turbulent superstructures occur.
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