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Author(s):
K. Itoh, S.-I. Itoh, A. Fukuyama
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Title:
Modelling of Transport Phenomena
Date of publication:
Sep. 1993
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Key words:
Anomalous transport, Fluctuations, Transport matrix, Self-sustained turbulence, L-mode, H-mode, Improved confinement mode, L-H transition, Viscosity, Thermal conductivity, Current diffusivisty, Pseudo-classical transport, Bohm diffusion
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Abstract:
In this review article, we discuss key features of the transport phenomena and theoretical modelling to understand them. Experimental observations have revealed the nature of anomalous transport, i.e., the enhancement of the transport coefficients by the gradients of the plasma profiles, the pinch phenomena, the radial profile of the apomalous transport coefficients, the variation of the transport among the Bohm diffusion, Pseudo-classical confinement, L-mode and variety of improved confinement modes, and the sudden jumps such as L-H transition. Starting from the formalism of the transport matrix, the modelling based on the low frequency instabilities are reviewed. Theoretical results in the range of drift wave frequency are examined. Problems in theories based on the quasilinear and mixing-length estimates lead to the renewal of the turbulence theory, and the physics picture of the self-sustained turbulence is discussed. The theory of transport using the fluid equation of plasma is developed, showing that the new approach is very promising in explaining above-mentioned characteristics of anomalous transport in both L-mode and improved confmement plasmas. The interference of the nuxes is the key to construct the physics basis of the bifurcation theory for the L-H transition. The present status of theories on the mechanisms of improved confinement is discussed. Modelling on the nonlocal nature of transport is briefly discussed. Finally, the impact of the anomalous transport on disruptive phenomena is also described.
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