Effects of a fluctuating sheared flow on cross phase in passive-scalar turbulent diffusion

Journal Article · Wed Nov 15 00:00:00 EST 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2363349· OSTI ID:20860361

Leconte, M; Beyer, P; Benkadda, S; Garbet, X ^[1]

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1. Equipe Dynamique des Systemes Complexes, LPIIM, UMR 6633 CNRS-Universite de Provence, Centre St. Jerome, Case 321, 13397 Marseille Cedex 20 (France)

Transport barriers are key elements concerning energy and particle confinement in fusion devices. They play a fundamental role in the L{yields}H transition observed in most tokamaks' edges. It has been shown that a shear in the ExB velocity could trigger and sustain such a barrier. The ExB velocity shear model has proven to be of great interest in the study of the formation and characteristics of transport barriers. Here we address a particular case of flow shear stabilization, namely the effect of a shear flow on the diffusion of a passive scalar. A shear flow reduces the radial flux (radial transport) {gamma} of a passive scalar field (we consider the pressure field) via the reduction of the turbulence energy {radical}(<p{sup 2}>) and/or via the reduction of the cross phase cos {delta} between the fluctuations of the pressure and velocity fields. We compare our results with those of different analytical models for passive-scalar advection or diffusion [Terry et al., Phys. Rev. Lett. 87, 185001 (2001); Kim and Diamond, Phys. Rev. Lett. 91, 075001 (2003)]. However, these studies yielded contradictory results. The purpose of this study is to shed light on this particular issue using numerical simulations to clarify the role of the reduction of the amplitude of turbulence and cross phase in regulating the radial transport.

• OSTI ID: 20860361
• Journal Information: Physics of Plasmas, Vol. 13, Issue 11; Other Information: DOI: 10.1063/1.2363349; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ADVECTION
AMPLITUDES
BOUNDARY LAYERS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
ELECTROMAGNETIC FIELDS
FLUCTUATIONS
H-MODE PLASMA CONFINEMENT
L-MODE PLASMA CONFINEMENT
NUMERICAL ANALYSIS
PLASMA
PLASMA PRESSURE
PLASMA SIMULATION
RADIATION TRANSPORT
SCALAR FIELDS
SCALARS
SHEAR
TOKAMAK DEVICES
TURBULENCE