about theory
meetings
people
projects
publications
review
home
Turbulent Transport Simulations & Analysis
GK/GF Comparisons | Integrated Analysis
Gyrokinetic Simulations
view project
A fully 3D, general geometry gyrokinetic particle code (GTC), which now uses field-line following coordinates, has been successfully developed. Massively parallel simulations have been performed for both turbulent and neoclassical transport studies with new results enabled by utilization of the full power of the T3E at NERSC. For example, by measuring the broadening of radial wave-number spectrum of turbulence in these global gyrokinetic simulations, the turbulence decorrelation by self-generated zonal flows has been quantitatively calculated for the first time [Z. Lin et al., Science, 281, 1835 (1998)].
Email Zhihong Lin for more information on Gyrokinetic Simulations.
Gyrofluid Simulations
Electromagnetic effects, which become especially important in regions of large pressure gradients, have been successively implemented in recent gyrofluid simulations. Results show that electron Landau damping can significantly increase the turbulent transport [P. Snyder et al., Oral Talk, Sherwood Theory Conference, 1999]. In order to take advantage of the power of the MPPs, the gyrofluid code has been parallelized and the domain decomposition algorithm has been improved from one to two-dimensions, in collaboration with the University of Maryland and University of Texas.
Email Michael Beer for more information on Gyrofluid Simulations.
GK/GF Comparisons
A new gyrofluid closure for more accurately representing zonal flow damping physics has been developed [M.A. Beer and G.W. Hammett, Theory of Fusion Plasmas, Proc. of Varenna Workshop, 1998, p.19]. This has been used to address the Rosenbluth and Hinton (PRL, 1998) results which suggest that the undamped components of the zonal flows are responsible for the difference between gyrokinetic particle-in-cell and gyrofluid simulation results. Preliminary results including this undamped component find up to 50% lower flux when compared to previous simulations in strong turbulence regimes. This reduces the GK/GF discrepancy from 3 to 2, depending on the details of closure
Email Michael Beer for more information on GK/GF Comparisons.
Integrated Analysis
The physics of zonal flow properties and the random shearing by self-generated zonal flows have been systematically studied via an integrated program of analytical theory together with gyrokinetic and gyrofluid simulations [T.S. Hahm et al, Invited Talk @ APS-DPP meeting in New Orleans (1998) and Phys. Plasmas, 6, (1999)]. For example, the effective E X B shearing rate for time-dependent zonal flows has been analytically derived and estimated from the zonal flow statistics of the gyrofluid simulations. It is found to be comparable to the maximum linear growth rate--in semi-quantitative agreement with the observations from simulations that turbulence is reduced but not completely quenched by zonal flows
Email Taik Soo Hahm for more information on Integrated Analysis.
about theory | meetings | people | projects | publications | review | home
all content © Princeton Plasma Physics Laboratory