Shear turbulence on a sparse spectral grid

Shear turbulence on a sparse spectral grid.

We simulate turbulence in a plane Couette geometry by a spectral method intermediate between full resolution and the complete elimination of small modes common in large eddy simulations. The wave number grid is sparse in spanwise and downstream direction, with a total number of modes proportional to Re(3/4) lnRe. At a Reynolds number of 2000 we could suppress more than 80% of the modes and stil...

Sparse Grid Spectral Methods

On shear-induced turbulence in rotating stars

We review various prescriptions which have been proposed for the turbulent transport of matter and angular momentum in differentially rotating stellar radiation zones. A new prescription is presented for the horizontal transport associated with the anisotropic shear turbulence which is produced by the differential rotation in latitude; this ‘β-viscosity’ is drawn from torque measurements in the...

Shear Turbulence: Onset and Structure

Figure 1: Reynolds’ 1883 experiment, still operating at the University of Manchester, UK. Water flows down a long pipe and ink is introduced at the pipe centerline. On the right are the original drawings showing the dye filament in laminar flow (a), and the rapid mixing of the dye and water when the Reynolds number is larger than about 2000 in (b). (c) shows details of vortical structures in tu...

Shear effects in nonhomogeneous turbulence

Motivated by recent experimental and numerical results, a simple unifying picture of intermittency in turbulent shear flows is suggested. Integral structure functions (ISF), taking into account explicitly the shear intensity, are introduced on phenomenological grounds. ISF can exhibit a universal scaling behavior, independent of the shear intensity. This picture is in satisfactory agreement wit...