The fm_wexb coefficient has been increased from 1e-6 to 1e-4. This factor determines the effect of ExB flow shear suppression on the anomalous transport:
Simulation results for the case XGC-209 that uses smoothing procedure introduced on January 12. In addition, effect of fm_wexb parameter on the particle transport is studied. The results show noticeable smoothing for the radial electric field profiles in the plasma core and very little change in the plasma density dynamics.
Smoothing procedure adopted from the ASTRA code on Friday (see previous post) is tested for set of 200 random numbers. The plots are generated for the smoothness parameter (left figure), (center figure), and (left figure):
In order to introduce more smoothing in the plasma core which is needed to compensate additional numerical noise in the core introduced by volume effect, dependence on is introduced:
where is the coefficient that controls region where smoothing is applied. The following function is selected for the next test:
where R is a random number in the range from 0 to 1, and are the coefficient that are set to 0.95 and 0.001 correspondingly. This function reproduce XGC-0 results for the radial electric field with more noise in the plasma core and large potential well in the plasma edge. The goal of smoothing is to remove noise in the plasma core and to preserve the details of potential well in the plasma edge. The results on the figure below are obtained for smoothness parameters and .
The level of smoothness in the plasma core is controlled by and the region where soothing is applied is controlled by the coefficient . Smaller values of should result in more extended region where the smoothing is applied. Test below show results for the same , but set to 2.
The idea for smoothing of plasma profiles is based on routine implemented in the ASTRA code. The resulting function is based on finding of the minimum of the functional
with respect to U. The functional is design for the cylindrical case and the resulting function has zero derivative for x=0 and preserve boundary condition at x=1. The description of the method can be found at:
B. K. P. Horn and B. G. Schunck, Artifical Intelligence, 17:185-203, 1981.
N. P. Galatsanos and A. K. Katsaggelos. IEEE transaction on image processing, 1(3):322-336, 1992.
New simulation for the whole plasma profile with XGC-0 standard anomalous transport model is submitted on FRANKLIN. The FMCFM interface is not used. All other settings are the same.
Error in the initialization of the case XGC-209 is discovered. The case is resubmitted with the following additional changes:
fm_nsmooth = 0 ! number of applications of smoothing in fmcfm_call
fm_nsmooth_er = 4 ! number of smoothing for radial electric field in the core region
fm_smooth_er_rhob = 0.95 ! rho, where transition between different level of smoothing is applied
fm_smooth_er_coef = 50. ! coefficient that controls sharpness of transition between different level of smoothness for Er
fm_nsmooth_chi = 2 ! number of applications of diffusivity smoothing in fmcfm_call
fm_wexb = 1.0d-6
Note that the flow shear stabilization coefficient is reduced from 1e-5 to 1e-6.
Averaging over three neighboring points is used in this case.