Life, death, and propagation of an isolated turbulent blob fed by vortex loops
ORAL
Abstract
We create and sustain an isolated blob of turbulence by repeatedly firing together vortex loops.
In the steady state, our PIV and 3D PTV measurements reveal that the blob consists of a turbulent core (Re_lambda = 50 - 300) surrounded by comparatively quiescent fluid. By examining the mass and enstrophy flux, distribution of energy and enstrophy, and turbulent statistics, we assemble a full picture of its three-dimensional structure, onset, and tunability. When the injection of vortex rings stops, a spherical front that separates the turbulent core from the quiescent surroundings propagates in the chamber, and the turbulence decays. By using a simple low-order closure model, we construct a spatially-extended description of the turbulence propagation, and compare its predictions of energy profile and non-diffusive dynamics with data.
In the steady state, our PIV and 3D PTV measurements reveal that the blob consists of a turbulent core (Re_lambda = 50 - 300) surrounded by comparatively quiescent fluid. By examining the mass and enstrophy flux, distribution of energy and enstrophy, and turbulent statistics, we assemble a full picture of its three-dimensional structure, onset, and tunability. When the injection of vortex rings stops, a spherical front that separates the turbulent core from the quiescent surroundings propagates in the chamber, and the turbulence decays. By using a simple low-order closure model, we construct a spatially-extended description of the turbulence propagation, and compare its predictions of energy profile and non-diffusive dynamics with data.
*This work was partially supported by the U.S. Army Research Office through Grant No. W911NF-17-S-0002, W911NF-18-1-0046, and W911NF-20-1-0117 to WI, and partially supported by a grant to NG from the Simons Foundation (Grant No. 662985, N.G.).
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Presenters
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Takumi Matsuzawa
- The University of Chicago