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  4. Uncertainty propagation by using spectral methods: A practical application to a two-dimensional turbulence fluid model
 
research article

Uncertainty propagation by using spectral methods: A practical application to a two-dimensional turbulence fluid model

Riva, Fabio
•
Milanese, Lucio
•
Ricci, Paolo  
2017
Physics of Plasmas

To reduce the computational cost of the uncertainty propagation analysis, which is used to study the impact of input parameter variations on the results of a simulation, a general and simple to apply methodology based on decomposing the solution to the model equations in terms of Chebyshev polynomials is discussed. This methodology, based on the work by Scheffel [Am. J. Comput. Math. 2, 173–193 (2012)], approximates the model equation solution with a semi-analytic expression that depends explicitly on time, spatial coordinates, and input parameters. By employing a weighted residual method, a set of nonlinear algebraic equations for the coefficients appearing in the Chebyshev decomposition is then obtained. The methodology is applied to a two-dimensional Braginskii model used to simulate plasma turbulence in basic plasma physics experiments and in the scrape-off layer of tokamaks, in order to study the impact on the simulation results of the input parameter that describes the parallel losses. The uncertainty that characterizes the time-averaged density gradient lengths, time-averaged densities, and fluctuation density level are evaluated. A reasonable estimate of the uncertainty of these distributions can be obtained with a single reduced-cost simulation.

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Uncertanty propagation - submitted.pdf

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http://purl.org/coar/version/c_ab4af688f83e57aa

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