Astronomische Nachrichten Astronomical Notes RE PR INT Turbulent viscosity and Λ - effect from numerical turbulence models

Homogeneous anisotropict urbulence simulations are used to determine off-diagonal componentso fthe Reynolds stress tensora nd itsp arameterizationi nt erms of turbulentv iscosity and Λ-effect.T he turbulence is forced in an anisotropic fashion by enhancing thestrengthofthe forcing in thevertical direction. TheCoriolis force is included with arotationaxis inclined relativetothe vertical direction. Thesystem studied here is significantly simpler than that of turbulent stratified convectionwhich has often been used to study Reynolds stresses. Certainpuzzlingfeatures of theresults for convection, suchassign changes or highly concentrated latitudedistributions, are not present in the simpler system considered here. Homogeneous anisotropic turbulence simulations are used to determine off-diagonal components of the Reynolds stress tensor and its parameterization in terms of turbulent viscosity and Λ-effect. The turbulence is forced in an anisotropic fashion by enhancing the strength of the forcing in the vertical direction. The Coriolis force is included with a rotation axis inclined relative to the vertical direction. The system studied here is significantly simpler than that of turbulent stratified convection which has often been used to study Reynolds stresses. Certain puzzling features of the results for convection, such as sign changes or highly concentrated latitude distributions, are not present in the simpler system considered here.