[Crib-list] TODAY: SPEAKER: Noah Mandell (Princeton) -- Computational Research in Boston and Beyond Seminar (CRIBB) -- Friday, August 2, 2019 from 12:00 PM - 1:00 PM in Building 36, Room 462

[Shirley Entzminger]

 	T O D A Y . . .


  	                Computational Research in Boston and Beyond Seminar
  				            (CRIBB)



DATE:		Friday, August 2, 2019

TIME:		12:00 PM to 1:00 PM

LOCATION:	Building 36, Room 462  (RLE)

  		 Enter... 50 Vassar Street
  		          Cambridge, MA


  	       (Pizza/beverages will be provided at 11:45 AM inside
  		        Room 36-462


TITLE:		Electromagnetic gyrokinetic turbulence simulations in the
  		 tokamak edge with discontinuous Galerkin methods



SPEAKER:	Noah Mandell  (Princeton Plasma Physics Laboratory)


ABSTRACT:

Gkeyll, a full-F continuum gyrokinetic code, is being developed to study 
plasma turbulence in the edge and scrape-off-layer (SOL) region of fusion 
devices.  This region involves large-amplitude fluctuations, electromagnetic 
effects, and plasma interactions with material walls due to open magnetic 
field lines; all of these effects make the edge more computationally 
challenging than the core region. Gkeyll models the turbulence by solving the 
5-D full-F gyrokinetic system in Hamiltonian form using an energy-conserving 
high-order discontinuous Galerkin (DG) scheme.  I will present new 
simulations that self-consistently include the effects of electromagnetic 
fluctuations of the background magnetic field on the turbulence in the SOL. 
These simulations are the first continuum gyrokinetic simulations on open 
field lines to include electromagnetic effects.

I will also present some of the implementation details of the DG scheme in 
Gkeyll.  We choose a modal basis composed of orthonormalized Serendipity 
polynomials, which makes tensor products sparse. We use a computer algebra 
system (like Mathematica) to compute the (sparse) tensor products in the DG 
weak form of the gyrokinetic equation.  This system then generates the solver 
kernels that form the back end of Gkeyll: thousands of lines of 
machine-written C code containing no loops.  This allows our algorithm to be 
able to take full advantage of the sparsity, and it also makes the 
implementation quadrature-free.  The result is an O(10) speed-up over a 
previous implementation which used a nodal Serendipity basis with Gaussian 
quadrature.

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Massachusetts Institute of Technology
Cambridge, MA


For information about the Computational Research in Boston and Beyond Seminar
(CRIBB), please visit....

  			http://math.mit.edu/crib/



===

Shirley A. Entzminger
Administrative Assistant II
Department of Mathematics
Massachusetts Institute of Technology
77 Massachusetts Avenue
Building 2, Room 350A
Cambridge, MA 02139
PHONE:	(617) 253-4347
FAX:	(617) 253-4358
E-mail:	daisymae at math.mit.edu