English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The goal of this study is to analyze the fine structure of nonlinear modalinteractions in different 1D Burgers and 3D Navier-Stokes flows. This analysisis focused on preferential alignments characterizing the phases of Fouriermodes participating in triadic interactions, which are key to determining thenature of energy fluxes between different scales. We develop novel diagnostictools designed to probe the level of coherence among triadic interactionsrealizing different flow scenarios. We consider extreme 1D viscous Burgersflows and 3D Navier-Stokes flows which are complemented by singularity-forminginviscid Burgers flows as well as viscous Burgers flows and Navier-Stokes flowscorresponding to generic turbulent and simple unimodal initial data, such asthe Taylor-Green vortex. The main finding is that while the extreme viscousBurgers and Navier-Stokes flows reveal the same relative level of enstrophyamplification by nonlinear effects, this behaviour is realized via modalinteractions with vastly different levels of coherence. In the viscous Burgersflows the flux-carrying triads have phase values which saturate thenonlinearity thereby maximizing the energy flux towards small scales. On theother hand, in 3D Navier-Stokes flows with the extreme initial data the energyflux to small scales is realized by a very small subset of helical triads. Thesecond main finding concerns the role of initial coherence. Comparison of theflows resulting from the extreme and generic initial conditions shows strikingsimilarities between these two types of flows, for the 1D viscous Burgersequation as well as the 3D Navier-Stokes equation.

Alignments of Triad Phases in 1D Burgers and 3D Navier-Stokes Flows