The dynamics of interacting nonlinearities governing long wavelength drift wave turbulence. Ph.D. Thesis
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 of the 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 (kps is less than or equal to 1). In particular, spectral energy transfer at long wavelengths is dominated by the E x B nonlinearity, which carries energy to short scale (even in 2-D) in a manner that is highly nonlocal and anisotropic. In marked contrast to the canonical self-similar cascade 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 (i.e., energy to high k) and are nonconservative in enstrophy and energy similarity ranges (but conservative overall).
- Research Organization:
- Wisconsin Univ., Madison, WI (United States). Space Science and Engineering Center
- OSTI ID:
- 264020
- Report Number(s):
- N-96-23720; NIPS-96-07774; TRN: 9623720
- Resource Relation:
- Other Information: TH: Ph.D. Thesis; PBD: Jan 1993
- Country of Publication:
- United States
- Language:
- English
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