SciTech Connect

Title: The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence

The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence Because of the ubiquitous nature of turbulence and the vast array of different systems which have turbulent solutions, the study of turbulence is an area of active research. Much present day understanding of turbulence is rooted in the well established properties of homogeneous Navier-Stokes turbulence, which, due to its relative simplicity, allows for approximate analytic solutions. This work examines a group of turbulent systems with marked differences from Navier-Stokes turbulence, and attempts to quantify some of their properties. This group of systems represents a variety of drift wave fluctuations believed to be of fundamental importance in laboratory fusion devices. From extensive simulation of simple local fluid models of long wavelength drift wave turbulence in tokamaks, a reasonably complete picture of the basic properties of spectral transfer and saturation has emerged. These studies indicate that many conventional notions concerning directions of cascades, locality and isotropy of transfer, frequencies of fluctuations, and stationarity of saturation are not valid for moderate to long wavelengths. In particular, spectral energy transfer at long wavelengths is dominated by the E {times} B nonlinearity, which carries energy to short scale in a manner that is highly nonlocal and anisotropic. In marked contrast to the canonical self-similar cascade more » dynamics of Kolmogorov, energy is efficiently passed between modes separated by the entire spectrum range in a correlation time. At short wavelengths, transfer is dominated by the polarization drift nonlinearity. While the standard dual cascade applies in this subrange, it is found that finite spectrum size can produce cascades that are reverse directed and are nonconservative in enstrophy and energy similarity ranges. In regions where both nonlinearities are important, cross-coupling between the nolinearities gives rise to large no frequency shifts as well as changes in the spectral dynamics. « less
Authors:
Publication Date:
OSTI Identifier:OSTI ID: 10103225
Report Number(s):DOE/ER/53291--225
ON: DE94001785; BR: AT0520210; TRN: 94:001335
DOE Contract Number:FG02-89ER53291
Resource Type:Thesis/Dissertation
Resource Relation:Other Information: TH: Thesis (Ph.D.); PBD: Sep 1993
Research Org:Wisconsin Univ., Madison, WI (United States). Plasma Physics Research
Sponsoring Org:USDOE, Washington, DC (United States)
Country of Publication:United States
Language:English
Subject: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; TURBULENCE; NONLINEAR PROBLEMS; PLASMA DRIFT; NAVIER-STOKES EQUATIONS; MAGNETIC CONFINEMENT; PLASMA WAVES 700340; 700330; PLASMA WAVES, OSCILLATIONS, AND INSTABILITIES; PLASMA KINETICS, TRANSPORT, AND IMPURITIES