Kinematic properties of passive scalar gradient predicted by a stochastic Lagrangian model

M Gonzalez (1)

1 CORIA - Complexe de recherche interprofessionnel en aérothermochimie

A modeled equation for the gradient of a passive scalar is derived consistently with the approach of Chevillard and Meneveau for the velocity gradient tensor [Phys. Rev. Lett. 97, 174501 (2006)] and its predictions are analyzed in three-dimensional, isotropic turbulence. General features of scalar gradient kinematics, namely, production of scalar gradient norm and alignment with respect to strain principal axes and vorticity are rather well described. A strain persistence parameter defined for tight alignment of vorticity with a strain eigenvector is used to bring further insight into geometric properties of the scalar gradient. In particular, the model results lend support to the existence of special alignments of the scalar gradient which are determined by local strain persistence and are different from the directions of strain principal axes as already shown in two-dimensional turbulence.

Mots clés: isotropic turbulence; scalar gradient; stochastic model

Domaines: Mécanique des fluides [physics.class-ph]; Milieux fluides et réactifs

M Gonzalez. Kinematic properties of passive scalar gradient predicted by a stochastic Lagrangian model. Physics of Fluids, 2009, 21, pp.055104. ⟨10.1063/1.3140004⟩. ⟨hal-01415347⟩