Eddy-resolving approaches in OpenFOAM

Large-eddy simulations

Hybrid RANS-LES (DES)

Wall resolved LES

Wall modeled LES

Requirements:

First cell in viscous sublayer (y+ < 1)

Buffer region up to y+ = 30 resolved with 10-20 grid points

Pros:

Cons:

Curtail need for wall function approximation

Long simulations (small time step, large domains)

Requirements:

First cell outside of buffer region (y+ > 30)

Approach basics:

Larger motions are modeled directly

Subgrid turbulence incorporating using a subgrid viscosity model

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Approach basics:

Use RANS in regions where the eddy length scale is too small for the LES grid and use LES with its subgrid scale model in regions where the scales are large enough to be resolved.

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