Snezhana Abarzhi
Center for Turbulence Research
Stanford University
Turbulent Mixing and Beyond
Abstract
Whenever fluids of different densities are accelerated against the
density gradient we observe the development of the Rayleigh-Taylor
instability (RTI), which causes extensive interfacial mixing of the
fluids. The turbulent mixing plays a key role in preventing the
formation of "hotspot" in inertial confinement fusion, providing proper
conditions for the synthesis of heavy mass elements in supernovae, in
determining the drop size distribution in sprays, in premixed and
non-premixed combustion, in the recovery and production of oil, etc.
The dynamics of RTI is governed by a system of conservation laws, which
are nonlinear partial differential equations with initial and boundary
conditions at the fluid interface. Singular aspects of the interface
evolution cause significant difficulties for theoretical and numerical
studies of RTI.
We suggest a new theoretical approach to the long-standing problem,
based on group theory and scale separation. The dynamics of the
large-scale coherent structures in RTI is studied, the invariants of
the flow are identified, and the non-local and multi-scale character of
the instability evolution is shown. A phenomenological model is
suggested to describe the turbulent mixing under various physical
conditions and to account for the stochastic properties of the process.
The applications of the obtained results are discussed.
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