Random shearing by zonal flows and transport reduction
- Department of Physics, University of California, San Diego, La Jolla, California 92093-0319 (United States)
The physics of random shearing by zonal flows and the consequent reduction of scalar field transport are studied. In contrast to mean shear flows, zonal flows have a finite autocorrelation time and can exhibit complex spatial structure. A random zonal flow with a finite correlation time {tau}{sub ZF} decorrelates two nearby fluid elements less efficiently than a mean shear flow does. The decorrelation time is {tau}{sub D}=({tau}{sub {eta}}/{tau}{sub ZF}{omega}{sub rms}{sup 2}){sup 1sol2} ({tau}{sub {eta}} is the turbulent scattering time, and {omega}{sub rms} is the rms shear), leading to larger scalar field amplitude with a slightly different scaling ({proportional_to}{tau}{sub D}/{omega}{sub rms}), as compared to the case of coherent shearing. In the strong shear limit, the flux scales as {proportional_to}{omega}{sub rms}{sup -1}.
- OSTI ID:
- 20643959
- Journal Information:
- Physics of Plasmas, Vol. 11, Issue 12; Other Information: DOI: 10.1063/1.1808455; (c) 2004 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Theory of turbulence regulation by oscillatory zonal flows
A generic model for transport in turbulent shear flows