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DY: Fachverband Dynamik und Statistische Physik
DY 12: Posters DY - Fluid Physics, Active Matter, Complex Fluids, Soft Matter and Glasses (joint session DY/BP)
DY 12.2: Poster
Monday, March 22, 2021, 14:00–16:30, DYp
Dynamic role of coherent structures in two-dimensional Navier-Stokes turbulence — •Jiahan Wang1, Wolf-Christian Müller1, and Jörn Sesterhenn2 — 1Technische Universität Berlin, Berlin, Germany — 2Universität Bayreuth, Bayreuth, Germany
Turbulent coherent structures can phenomenologically be described as regions in a flow exhibiting a high level of spatio-temporal correlation. Although these structures are ubiquitously observed in nature, providing a universal and rigorous definition of them is not a straightforward task. Therefore the choice of a suitable structure detection method is generally not unique and problem-dependent. We are interested in structures appearing in statistically isotropic Navier-Stokes turbulence. For this purpose, direct numerical simulations (DNS) of a two-dimensional flow, forced at small spatial scales, are employed to compare different definitions of structural coherence. This setup inherently forms large scale structures due to the inverse cascade of energy. Detection methods such as the identification of Lagrangian coherent structures (LCS), dynamic mode decomposition (DMD) and wavelet denoising are all capable of splitting physical fields into coherent and incoherent contributions. Based on that, the analysis of the scale-to-scale decomposed energy flux yields a physical interpretation for the influence of those structures onto the overall inverse cascade dynamics. As a result, the decomposed fluxes gained from LCS and DMD are related, whereas the wavelet decomposition shows no similarity at all.