Subgrid models

In Large-Eddy Simulation, a subgrid modeling is used to represent unresolved small-scale fluid motion effects, such as viscous dissipation, through a subgrid viscosity. The formulation of subgrid models requires understanding of the physics and the statistics of scale interactions in hydrodynamic turbulence.

From dimensional analysis it follows that the subgrid viscosity is a product between a characteristic scale \(I\) and a characteristic velocity \(V\) of the subgrid scale motion. The characteristic scale is the filter width, which in the simulation is replaced by the grid spacing \(\Delta x\). A natural candidate for the characteristic velocity is \(\sqrt{k_{I}}\), where \(k_{I}\) is the kinetic energy of eddies of size \(I\).

Note

The subgrid model to be used for simulations depends on testing