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\u65e5\u6642\uff1a 2\u670818\u65e5\uff08\u6728\uff09 15:00 \u304b\u3089 16:30<\/p>\n
\u5834\u6240\uff1a \u4eac\u5927 \u7406\u5b66\u7814\u7a76\u79d15\u53f7\u9928\uff08\u7269\u7406\u5b66\u6559\u5ba4\uff09413\u53f7\u5ba4<\/p>\n
\u8b1b\u5e2b\uff1a Prof. Sadruddin Benkadda
\n (International Institute for fusion Science-Universite
\n de Provence, Marseille France)<\/p>\n
\u984c\u76ee: Patterns, Intermittent Transport and Universality
\n in Convective Turbulence in Magnetic Fusion Plasmas<\/p>\n
\u6982\u8981\uff1aBuoyancy-driven flows such as thermal convection are of great
\n importance for a wide range of phenomena in geophysical,
\n astrophysical and fusion plasmas [1,2,3]. We consider here
\n intermittent aspects of convective turbulence and transport in
\n magnetized plasma of magnetic fusion machines such as tokamaks or
\n stelerators. These investigations use Direct Numerical Simulation
\n (DNS) of Ion Temperature Gradient instability (ITG) which is
\n identical to the Rayleigh-Benard thermal convection problem in
\n neutral fluids [4,5,6]. Rayleigh-Benard convection in particular
\n is a fundamental paradigm for nonlinear dynamics including
\n instabilities and bifurcations, pattern formation, chaotic
\n dynamics and developed turbulence.<\/p>\n
Using a weakly non-linear analysis, we show that the back-reaction
\n on the mean profile is the natural mechanism for saturation and
\n suggest that it will stay the main non-linear coupling mechanism
\n in the turbulent state. We also will review some basic aspects of
\n the interaction between convective cells and a mean flow [7,8]. In
\n particular and still along the line of the “defreezing” assumption
\n we study the behavior of a model for shear flow instability :
\n transient bursts of vorticity flux are generated in this model. We
\n briefly discuss the advantage of this kind of formulation compared
\n to the “non-normal” operator approach where the mean velocity is
\n also assumed frozen . <\/p>\n
An extension of Herring model is derived. It takes into account
\n the self-consistent generation of a mean flow. It is shown that
\n our model has substantially richer dynamics than the one of
\n Herring. In particular the interaction between the convective
\n modes and the mean flow leads in the turbulent state to a
\n transition in the statistical properties of the transport. This
\n bifurcation is analogous the so-called soft to hard turbulence
\n transition in convection. In the strongly turbulent state,
\n intermittent bursts of thermal transport are observed in both
\n cases. For the latter regime, the reduced model as well as DNS
\n show that the Nusselt number Nu (normalized heat flux) scales with
\n the normalized ion pressure gradient Ki as Nu \u203e Ki1\/3[6]. Since
\n the Rayleigh number for ITG turbulence is proportional to Ki, the
\n Nusselt number scaling for ITG turbulence is thus similar to the
\n classical Globe & Dropkin scaling for Rayleigh-Benard convection
\n in neutral fluids.<\/p>\n
References:
\n [1]S. Benkadda, P. Beyer, N. Bian et al, Nuclear Fusion 41, 997
\n (2001)
\n [2] P. Beyer, S. Benkadda, X. Garbet and P.H. Diamond, Phys. Rev
\n Letters 85, 4892 (2000).
\n [3] Amita Das, Abhijit Sen, and Predhiman Kaw, S. Benkadda and
\n Peter Beyer, Physics of Plasmas 12, 032302 (2005)
\n [4] K. Takeda, S. Benkadda, S. Hamaguchi and M. Wakatani, Physics
\n of Plasmas 11, 3561-3571 (2004)
\n [5] K. Takeda, S. Benkadda, S. Hamaguchi and M. Wakatani, J.
\n Plasma Fusion Res 6 570 (2004)
\n [6] K. Takeda, S. Benkadda, S. Hamaguchi, M. Wakatani, Physics of
\n Plasmas 12, 052309 (2005)
\n [7] N. Bian, S. Benkadda, X. Garbet, O. Garcia, J. Paulsen, Physics
\n of Plasmas, 10, 1382, (2003)
\n [8] O. Garcia, N. Bian, J. Paulsen , S. Benkadda and K. Rypdal,
\n Plasma Physics and Controlled Fusion 45, 919-932, (2003) <\/p>\n
+–+–+–+–+–+–+–+–+–+–+–+–+–+–+–+–+–+–+–+—-+–+–+<\/p>\n
\u4e16\u8a71\u4eba\uff1a\u5c71\u7530 \u9053\u592b(\u4eac\u5927\u6570\u7406\u7814)\uff0c \u85e4 \u5b9a\u7fa9(\u4eac\u5927)\uff0c\u677e\u672c \u525b(\u4eac\u5927\u7406)
\n\u30a2\u30c9\u30d0\u30a4\u30b6\u30fc\uff1a\u8239\u8d8a \u6e80\u660e\uff08\u4eac\u5927\u60c5\u5831\u5b66\uff09\u3001\u6c34\u5cf6 \u4e8c\u90ce(\u540c\u5fd7\u793e\u5927\u5de5)\u3001
\n \u4f59\u7530 \u6210\u7537\uff08\u4eac\u5927\u7406\uff09
\n\u9023\u7d61\u5148\uff1a\u5c71\u7530\u9053\u592b yamada@kurims.kyoto-u.ac.jp
\n=========================================================<\/p>\n","protected":false},"excerpt":{"rendered":"
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