title: Impact of the inherent separation of scales in the Navier-Stokes- alphabeta equations.
abstract: We study the effect of the length scales alpha and beta in the Navier-Stokes- alphabeta equations on the energy spectrum and the alignment between the vorticity and the eigenvectors of the stretching tensor in three-dimensional homogeneous and isotropic turbulent flows in a periodic cubic domain, including the limiting cases of the Navier-Stokes- alpha and Navier-Stokes equations. A significant increase in the accuracy of the energy spectrum at large wave numbers arises for beta<alpha . The vorticity structures predicted by the Navier-Stokes- alphabeta equations also improve as beta decreases away from alpha . However, optimal choices for alpha and beta depend not only on the problem of interest but also on the grid resolution.
authors.affiliation: Department of Mechanical Engineering, McGill University, Montréal, Quebec, Canada H3A 2K6.
authors.forename: Tae-Yeon
authors.initials: TY
authors.lastname: Kim
authors.forename: Massimo
authors.initials: M
authors.lastname: Cassiani
authors.forename: John D
authors.initials: JD
authors.lastname: Albertson
authors.forename: John E
authors.initials: JE
authors.lastname: Dolbow
authors.forename: Eliot
authors.initials: E
authors.lastname: Fried
authors.forename: Morton E
authors.initials: ME
authors.lastname: Gurtin