# Eddy viscosity and laminarization of sheared flow in three dimensional reduced magnetohydrodynamic turbulence

## Abstract

The effect of Alfven waves on turbulent momentum transport is studied in three-dimensional reduced magnetohydrodynamic turbulence. A strong external uniform magnetic field B{sub 0} 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/B{sub 0}{sup 2} for a strong B{sub 0}, due to the cancellation of the Reynolds stress by Maxwell stress. The sign of eddy viscosity is found to depend on the detailed properties of forcings. Specifically, it is positive for fluid forcing but depends on the anisotropy of the forcing in the case of magnetic forcing. Furthermore, it is indicated that a magnetic field tends to laminarize a mean shear flow. The possible implication of these results for the dynamics of the zonal flows in tokamaks is discussed in view of the cancellation of stresses.

- Authors:

- Publication Date:

- Sponsoring Org.:
- (US)

- OSTI Identifier:
- 40277840

- DOE Contract Number:
- AC02-76-CHO-3073; FG03-88ER 53275

- Resource Type:
- Journal Article

- Journal Name:
- Physics of Plasmas

- Additional Journal Information:
- Journal Volume: 8; Journal Issue: 8; Other Information: DOI: 10.1063/1.1383284; Othernumber: PHPAEN000008000008003576000001; 026108PHP; PBD: Aug 2001; Journal ID: ISSN 1070-664X

- Publisher:
- The American Physical Society

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANISOTROPY; CANCELLATION; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; SHEAR; STRESSES; TRANSPORT; TURBULENCE; VISCOSITY

### Citation Formats

```
Kim, Eun-jin, Hahm, T S, and Diamond, P H.
```*Eddy viscosity and laminarization of sheared flow in three dimensional reduced magnetohydrodynamic turbulence*. United States: N. p., 2001.
Web. doi:10.1063/1.1383284.

```
Kim, Eun-jin, Hahm, T S, & Diamond, P H.
```*Eddy viscosity and laminarization of sheared flow in three dimensional reduced magnetohydrodynamic turbulence*. United States. doi:10.1063/1.1383284.

```
Kim, Eun-jin, Hahm, T S, and Diamond, P H. Wed .
"Eddy viscosity and laminarization of sheared flow in three dimensional reduced magnetohydrodynamic turbulence". United States. doi:10.1063/1.1383284.
```

```
@article{osti_40277840,
```

title = {Eddy viscosity and laminarization of sheared flow in three dimensional reduced magnetohydrodynamic turbulence},

author = {Kim, Eun-jin and Hahm, T S and Diamond, P H},

abstractNote = {The effect of Alfven waves on turbulent momentum transport is studied in three-dimensional reduced magnetohydrodynamic turbulence. A strong external uniform magnetic field B{sub 0} 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/B{sub 0}{sup 2} for a strong B{sub 0}, due to the cancellation of the Reynolds stress by Maxwell stress. The sign of eddy viscosity is found to depend on the detailed properties of forcings. Specifically, it is positive for fluid forcing but depends on the anisotropy of the forcing in the case of magnetic forcing. Furthermore, it is indicated that a magnetic field tends to laminarize a mean shear flow. The possible implication of these results for the dynamics of the zonal flows in tokamaks is discussed in view of the cancellation of stresses.},

doi = {10.1063/1.1383284},

journal = {Physics of Plasmas},

issn = {1070-664X},

number = 8,

volume = 8,

place = {United States},

year = {2001},

month = {8}

}