17. Large Eddy Simulation
Large Eddy Simulation (LES) offers a compromise between direct numerical simulation and Reynolds-averaged Navier-Stokes equations, enabling a more practical approach to turbulent flow modeling. It focuses on capturing larger eddies and models smaller eddies indirectly through turbulence models. Understanding the distinctions between large and small eddies, their energy transfer, and the governing equations of LES is crucial for simplifying challenging computational fluid dynamic problems.
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What we have learnt
- Large eddies behave anisotropically and are influenced by mean flow and boundary conditions.
- Small eddies exhibit nearly isotropic behavior and have a universal nature as described by the Kolmogorov hypothesis.
- LES utilizes time-dependent simulations to resolve large eddies while modeling small eddies with a turbulence model.
Key Concepts
- -- Large Eddy Simulation (LES)
- A technique to model turbulent flows by directly simulating large eddies and applying a turbulence model for smaller eddies.
- -- Kolmogorov Hypothesis
- A principle suggesting that small eddies in turbulent flows exhibit universal behavior, contrasting with the scale-dependent behavior of large eddies.
- -- Filtered NavierStokes Equations
- Equations formulated in LES that account for large eddies while incorporating effects from smaller eddies through subgrid-scale modeling.
- -- Spatial Filtering
- A process in LES to separate large and small eddies using a filter function, focusing on the relevant scales for simulation.
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