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Simulations of turbulent flows hit with strong shockwaves

Sanjiva K. Lele
Stanford University

Turbulent flows which also involve interactions with strong shocks and density variations arise in many diverse areas of science and technology. For example the explosive phenomena associated with supernova explosions, volcanic eruptions, accidental detonations involving natural gas leaks, shock wave lithotripsy to break up kidney stones, as well as the implosion of a cryogenic fuel capsule for inertial confinement fusion all involve dramatic compression and expansion of multi-phase materials, their turbulent mixing and chemical reactions. Strong shock waves, strong acceleration and deceleration of heterogeneous materials and associated turbulent mixing play a critical part in these phenomena. Besides the multi-scale hydrodynamic processes, these phenomena also involve other physics and chemistry rich in its complexity and nonlinearity, such as plasma physics, radiation transport, and complex chemical kinetics. The current ability to predict these flow phenomena is strongly limited by the models of turbulence used, and by the computational algorithms employed. This project, utilizing the petascale computational capabilities envisioned by the Department, provides an opportunity to revolutionize the scientific understanding of shock-turbulence interactions and multimaterial mixing in complex flows by simulations at unparalleled fidelity.

The project will consider turbulent flow configurations involving shock-turbulence interaction and multi-material mixing for fundamental scientific study, and for systematic model development, for example for use in large-eddy simulations in the context of applications to accelerated multi-material flows. The team will also systematically evaluate different novel numerical approaches for nonlinear, multi-scale shock-turbulence interaction flow problems to establish the best practices and rigorous benchmarks in large-eddy simulations.

Problems of shock-turbulence interaction present a philosophical dilemma in numerical algorithm development. Methods designed to treat discontinuities and shocks are inherently dissipative for turbulence, and methods designed for turbulence (fluctuating fields with broadband variations) are ineffective for discontinuities. Capturing the interactions at unprecedented realism requires novel algorithms and effective use of software tools which allow the full benefit of the new algorithms to be realized on the massively parallel computer architectures.

Flows involving the interaction of strong shocks with turbulence and density interfaces are central to laser-driven implosion of inertial confinement fusion plasmas, as well as in the broader Stockpile Stewardship mission of DOE. However, the current scientific understanding of shock-turbulence interactions in complex configurations, and the ability to reliably predict these strongly nonlinear multi-scale flows remains limited and imperfect. It is this area of science application, with relevance to inertial confinement fusion application and supernovae astrophysics, that the current Project aims to revolutionize by bringing together a team with deep expertise in numerical simulations of turbulence and turbulence physics, computational gas dynamics and shock wave physics, numerical analysis and nonlinear dynamics, and massively parallel computing.





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