196 research outputs found
Non regression testing for the JOREK code
Non Regression Testing (NRT) aims to check if software modifications result
in undesired behaviour. Suppose the behaviour of the application previously
known, this kind of test makes it possible to identify an eventual regression,
a bug. Improving and tuning a parallel code can be a time-consuming and
difficult task, especially whenever people from different scientific fields
interact closely. The JOREK code aims at investing Magnetohydrodynamic (MHD)
instabilities in a Tokamak plasma. This paper describes the NRT procedure that
has been tuned for this simulation code. Automation of the NRT is one keypoint
to keeping the code healthy in a source code repository.Comment: No. RR-8134 (2012
The Problem of Marginality in Model Reductions of Turbulence
Reduced quasilinear (QL) and nonlinear (gradient-driven) models with scale
separations, commonly used to interpret experiments and to forecast turbulent
transport levels in magnetised plasmas are tested against nonlinear models
without scale separations (flux-driven). Two distinct regimes of turbulence --
either far above threshold or near marginal stability -- are investigated with
Boltzmann electrons. The success of reduced models especially hinges on the
reproduction of nonlinear fluxes. Good agreement between models is found above
threshold whilst reduced models would significantly underpredict fluxes near
marginality, overlooking mesoscale flow organisation and turbulence
self-advection. Constructive prescriptions whereby to improve reduced models is
discussed
Global gyrokinetic simulations of rho* and nu* scalings of turbulent transport
Turbulent transport dynamics and level are investigated with the 5D gyrokinetic global code GYSELA, modelling the Ion Temperature Gradient instability with adiabatic electrons. The heat transport exhibits large scale events, propagating radially in both directions at velocities of the order of the diamagnetic velocity. The effective diffusivity is in agreement with that reported in other gyrokinetic codes such as ORB5. Transition from Bohm to gyroBohm scaling is observed on the turbulence correlation length and time, when the normalized gyroradius is decreased from to . The transition value could depend on the distance to the ITG threshold. Collisions are modelled by a reduced Lorentz-type operator. It allows one to recover theoretical neoclassical predictions in the banana and plateau regimes, namely the heat diffusivity and the mean poloidal flow. In the turbulent regime, preliminary results suggest the turbulent transport increases with collisionality close to the threshold, in agreement with previous publications. Finally, the mean poloidal flow can be increased by about 40% as compared to the neoclassical value
Three-dimensional non-linear magnetohydrodynamic modeling of massive gas injection triggered disruptions in JET
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