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Plasma Physics (Physics/ECE/NE 922) Seminar
“Turbulent Mixing: Problems, Concepts, Solutions”
Date: Monday, February 14th
Time: 12:05 pm
Place: 2241 Chamberlin Hall
Speaker: Snezhana Abarzhi, University of Chicago
Abstract: Turbulent mixing plays an important role in a broad variety of plasma systems, spanning astrophysical to atomistic scales and low to high energy densities. Examples include inertial confinement fusion, Z-pinches, core-collapse supernovae, thermonuclear stellar flashes, magneto-convection, ionospheric plasmas, and light-material interaction. Theoretical description of non-equilibrium mixing transports is a challenging problem due to singular aspects of the governing (Euler or Navier-Stokes) equations. Furthermore these processes are statistically unsteady and their fluctuating quantities are essentially time-dependent and non-Gaussian.

We developed a novel theoretical concept, the rate of momentum loss, and applied it to describe the transports of mass, momentum and energy in turbulent mixing flow and to capture its anisotropic and inhomogeneous character. It was shown that invariant, scaling and spectral properties of unsteady turbulent mixing differ substantially from those of isotropic and homogeneous turbulence. Time- and
scale-invariance of the rate of momentum loss leads to non-dissipative momentum transfer, to and power-law
scale-dependencies of the velocity and Reynolds number and to non-Kolmogorov spectra. Turbulent mixing exhibits more order compared to isotropic turbulence, and its viscous and dissipation scales are finite and set by flow acceleration. We suggested how to describe the random character of the statistically unsteady turbulent flow and showed that the rate of momentum loss is the statistic invariant and a robust
diagnostic parameter for either sustained or time-dependent acceleration. Some criteria are outlined for the estimate of the fidelity and information capacity of the experimental and numerical data sets.
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