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09-04-13 15:00 Age: 5 years

By:  Fernando F. Grinstein (Los Alamos National Laboratory)

On coarse grained simulations of high reynolds-number turbulent material mixing


Abstract

Under-resolved computer simulations are typically unavoidable in many
practical turbulent flow applications exhibiting extreme geometrical complexity and a broad range of length and time scales. In such applications, coarse grained simulation (CGS) becomes the effective simulation strategy mostly by necessity rather than by choice. In CGS strategies, a resolved / under-resolved scale separation is assumed possible, large energy containing structures are resolved, smaller structures are spatially filtered out, and unresolved subgrid effects are modeled; this includes classical large eddy simulation (LES) strategies [1] with explicit use of closure subgrid scale models, and implicit LES (ILES) [2], relying on subgrid modeling implicitly provided by physics capturing numerical algorithms. The performance of CGS in the substantially difficult problem of under-resolved material mixing driven by under-resolved velocity fields and under-resolved initial conditions is a particular focus of the present work. We survey our present understanding of the theoretical basis of ILES from the perspectives of classical LES and finite-scale (observable dynamics). Examples from relevant recent simulations of canonical turbulence test cases and shock driven turbulence are presented; relevant verification and validations issues are addressed in this context.

1. Sagaut P., Large Eddy Simulation for Incompressible Flows, Springer, 2006.
2. Grinstein, F.F, Margolin, L.G., Rider, W.J.,Implicit Large Eddy Simulation: Computing Turbulent Fluid Dynamics, Cambridge UP, 2nd printing 2010


09-04-13 15:00 Age: 5 years

By:  Fernando F. Grinstein (Los Alamos National Laboratory)

On coarse grained simulations of high reynolds-number turbulent material mixing


Abstract

Under-resolved computer simulations are typically unavoidable in many
practical turbulent flow applications exhibiting extreme geometrical complexity and a broad range of length and time scales. In such applications, coarse grained simulation (CGS) becomes the effective simulation strategy mostly by necessity rather than by choice. In CGS strategies, a resolved / under-resolved scale separation is assumed possible, large energy containing structures are resolved, smaller structures are spatially filtered out, and unresolved subgrid effects are modeled; this includes classical large eddy simulation (LES) strategies [1] with explicit use of closure subgrid scale models, and implicit LES (ILES) [2], relying on subgrid modeling implicitly provided by physics capturing numerical algorithms. The performance of CGS in the substantially difficult problem of under-resolved material mixing driven by under-resolved velocity fields and under-resolved initial conditions is a particular focus of the present work. We survey our present understanding of the theoretical basis of ILES from the perspectives of classical LES and finite-scale (observable dynamics). Examples from relevant recent simulations of canonical turbulence test cases and shock driven turbulence are presented; relevant verification and validations issues are addressed in this context.

1. Sagaut P., Large Eddy Simulation for Incompressible Flows, Springer, 2006.
2. Grinstein, F.F, Margolin, L.G., Rider, W.J.,Implicit Large Eddy Simulation: Computing Turbulent Fluid Dynamics, Cambridge UP, 2nd printing 2010


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