Numerical scale separation in large-eddy simulation
Large-eddy simulation (LES) seeks to predict the dynamics of spatially filtered turbulent flows. The essence of a scale-separation LES model is that it stops the nonlinear production of smaller scales of motion at the scale set by the filter: there the modeled eddy dissipation has to balance the production. Numerical discretization changes both the nonlinear production and dissipation of sub-filter scales. Therefore, the discrete balance between production and dissipation can deviate from the continuous balance, in particular if a balance is imposed near the scale set by the numerical grid. This paper demonstrates that a scale-separation LES model should attain a production-dissipation balance in the numerical setting. Eddy-viscosity models based on this requirement are derived and successfully applied in simulations of decaying isotropic turbulence and channel flow.
Additional InformationThe authors kindly acknowledge Guillaume Balarac and Antoine Vollant for performing spectral simulations with the qr model during the Summer Program.
Published - 06_verstappen.pdf