Experimental measurement of the vorticity-strain alignment around extreme energy transfer events

Abstract

This work experimentally explores the alignment of the vorticity vector and the strain-rate tensor eigenvectors at locations of extreme upscale and downscale energy transfer. We show that the turbulent von Karman flow displays vorticity-strain alignment behavior across a large range of Reynolds numbers, which are very similar to previous studies on homogeneous, isotropic turbulence. We observe that this behavior is amplified for the largest downscale energy transfer events, which tend to be associated with sheet-like geometries. These events are also shown to have characteristics previously associated with high flow field non-linearity and singularities. In contrast the largest upscale energy transfer events display much different structures which showcase a strong preference for vortex-compression. We then show further evidence to the argument that strain-self-amplification is the most salient feature in characterizing cascade direction. Finally, we identify possible invariant behavior for the largest energy transfer events, even at scales near the Kolmogorov scale.

arXiv commentJFM Submission/preprint, 20 pages, 11 figures

References in corpus (17)

• Multistability and memory effect in a highly turbulent flow: experimental evidence for a global bifurcation
• Lagrangian dynamics and statistical geometric structure of turbulence
• Extreme velocity gradients in turbulent flows
• Is vortex stretching the main cause of the turbulent energy cascade?
• Modeling the pressure Hessian and viscous Laplacian in Turbulence: comparisons with DNS and implications on velocity gradient dynamics
• Energy transfer from large to small scales in turbulence by multi-scale nonlinear strain and vorticity interactions
• Pressure Hessian and viscous contributions to velocity gradient statistics based on Gaussian random fields
• Vortex stretching and enstrophy production in high Reynolds number turbulence
• Direct Assessment of Vorticity Alignment with Local and Nonlocal Strain Rates in Turbulent Flows
• On the role of vorticity stretching and strain self-amplification in the turbulence energy cascade
• Experimental evidence of a phase transition in a closed turbulent flow
• Triple decomposition of velocity gradient tensor in homogeneous isotropic turbulence
• Vorticity-strain rate dynamics and the smallest scales of turbulence
• Entropy, irreversibility and cascades in the inertial range of isotropic turbulence
• Global vs local energy dissipation: the energy cycle of the turbulent von Kármán flow
• Velocity gradient partitioning in turbulent flows
• Universality and Thermodynamics of Turbulence