Abstract
We assess two techniques for extracting coherent vortices out of turbulent flows: the wavelet based Coherent Vorticity Extraction (CVE) and the Proper Orthogonal Decomposition (POD). The former decomposes the flow field into an orthogonal wavelet representation and subsequent thresholding of the coefficients allows one to split the flow into organized coherent vortices with non-Gaussian statistics and an incoherent random part which is structureless. POD is based on the singular value decomposition and decomposes the flow into basis functions which are optimal with respect to the retained energy for the ensemble average. Both techniques are applied to direct numerical simulation data of two-dimensional drift-wave turbulence governed by Hasegawa-Wakatani equation, considering two limit cases: the quasi-hydrodynamic and the quasi-adiabatic regimes. The results are compared in terms of compression rate, retained energy, retained enstrophy and retained radial flux, together with the enstrophy spectrum and higher order statistics.
Translated title of the contribution | Coherent vorticity extraction in resistive drift-wave turbulence: Comparison of orthogonal wavelets versus proper orthogonal decomposition |
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Original language | French |
Pages (from-to) | 123-131 |
Number of pages | 9 |
Journal | Comptes Rendus Physique |
Volume | 12 |
Issue number | 2 |
DOIs | |
State | Published - Mar 2011 |
Funding
The authors acknowledge financial support from the Agence Nationale de la Recherche under contract ‘M2TFP’. D.dC.N. is thankful for the support from the Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the US Department of Energy under contract DE-AC05-00OR22725. D.dC.N. also gratefully acknowledges the hospitality and financial support of the École Centrale de Marseille during the elaboration of this work. K.S. and M.F. are thankful to the Association CEA-EURATOM and the French Research Federation for Fusion Studies for supporting their work within the framework of the European Fusion Development Agreement under contract V.3258.001. The views and opinions expressed herein do not necessarily reflect those of the European Commission. M.F. thanks the Wissenschaftskolleg zu Berlin for its kind hospitality while writing this paper.
Keywords
- Coherent structures
- Plasma turbulence
- Proper orthogonal decomposition
- Wavelets