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Author(s):
H. Sugama and W. Horton
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Title:
Dynamical Model of Pressure-Gradient-Driven Turbulence and Shear Flow Generation in L-H Transition
Date of publication:
Aug. 1994
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Key words:
pressure-gradient-driven turbulence, shear flow, L-H transition, Reynolds stress
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Abstract:
We present a dynamical model for the L-H transition consisting of three ordinary differential equations. This model describes temporal evolutions of three characteristic variables, i.e., the free energy contained in the pressure gradient, the turbulent kinetic energy and the shear flow energy in the resistive pressure-gradient-driven turbulence. The model equations have stationary solutions corresponding to the L and H-modes and their stabilities depend on the energy input to the peripheral region. Changing the energy input parameter yields the L to H and H to L transitions. We also find the parameter region in which the H-mode stationary solution becomes unstable and bifurcate to the limit cycle which shows periodic oscillations like ELM. It depends on the viscosity for the shear flow which the type of the L-H transition is, a first-order of second-order transition.
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