Two approaches for closing the turbulence subgrid-scale stress tensor in terms of matrix exponentials are introduced and compared. The first approach is based on a formal solution of the stress transport equation in which the production terms can be integrated exactly in terms of matrix exponentials. This formal solution of the subgrid-scale stress transport equation is shown to be useful to ex...

Toroidal magnetic fields subject to the Tayler instability can transport angular momentum. We show that the Maxwell and Reynolds stress of the nonaxisymmetric field pattern depend linearly on the shear in the cylindrical gap geometry. Resulting angular momentum transport also scales linear with shear. It is directed outwards for astrophysical relevant flows and directed inwards for superrotatin...

Simulations of stochastically forced shear-flow turbulence in a shearing-periodic domain are used to study the spontaneous generation of large-scale flow patterns in the direction perpendicular to the plane of the shear. Based on an analysis of the resulting large-scale velocity correlations it is argued that the mechanism behind this phenomenon could be the mean-vorticity dynamo effect pioneer...

Turbulent flow over wall-mounted cube in a channel was investigated numerically using Large Eddy Simulation. The Selective Structure Function model was used to determine eddy viscosity that appeared in the subgrid scale stress terms in momentum equations. Studies were carried out for the flows with Reynolds number ranging from 1000 to 40000. To evaluate the computational results, data was compa...

Aims. To understand the fundamental physical processes important for the evolution of solar rotation and distribution of chemical species, we provide theoretical predictions for particle mixing and momentum transport in the stably stratified tachocline. Methods. By envisioning that turbulence is driven in the tachocline, we compute the amplitude of turbulent flow, turbulent particle diffusiviti...

This paper discusses the development of a high-order, multidomain based large-eddy simulation (LES) for compressible flows. The LES model equations are approximated on unstructured grids of non-overlapping hexahedrals subdomains providing geometric flexibility. In each domain a highorder Chebyshev polynomial approximation represents the solution ensuring a highly accurate approximation with lit...

A general solution for the eddy viscosity within the surface layer is presented on the basis of rst order closure. Eddy viscosity for stable or unstable stratiication is calculated for given friction velocity, buoyancy ux and length scale. The turbulent length scale is obtained from comparison with several empirical prooles of the diabatic wind proole. Zusammenfassung Eine allgemeine LL osung d...

The effect of Alfvén waves on turbulent momentum transport is studied in three-dimensional reduced magnetohydrodynamic turbulence. A strong external uniform magnetic field B0 is assumed to be present orthogonal to both background shear flow and its inhomogeneity. Energy is injected into the fluid and/or magnetic field on small scales. It is shown analytically that eddy viscosity is reduced as 1...

Discussed is the use of tctroons to obtain cstiinates of the Reynolds stresses, the rate of production of eddy kitictic energy through these stresses, thc coefficictit of eddy viscosity, and thc viscous dissipation within thc planetary boundary layer. At a n average height of about 3000 ft. (admittedly in thc upper portion of the boundary layer) the tetroons yield a mean value for the zonal Rey...

We present a one-equation subgrid scale model that evolves the turbulence energy corresponding to unresolved velocity fluctuations in large eddy simulations. The model is derived in the context of the Germano consistent decomposition of the hydrodynamical equations. The eddy-viscosity closure for the rate of energy transfer from resolved toward subgrid scales is localised by means of a dynamica...