Characterizing most irregular small scale structures in turbulence using local Hölder exponents

Florian Nguyen (1) , Jean-Philippe Laval (1) , Bérengère Dubrulle (2)

1 LMFL - Laboratoire de Mécanique des Fluides de Lille - Kampé de Fériet
2 CEA - Commissariat à l'énergie atomique et aux énergies alternatives

Two scalar fields characterizing respectively pseudo-Holder exponents and local energy transfers are used to capture the topology and the dynamics of the velocity fields in areas of lesser regularity. The present analysis is conducted using velocity fields from two Direct Numerical Simulations (DNS) of the Navier-Stokes equations in a triply periodic domain. A "typical irregular structure" is obtained by averaging over 213 most irregular events. Such structure is similar to a Burgers vortex, with non-axisymmetric corrections. A possible explanation of such asymmetry is provided by a detailed time-resolved analysis of birth and death of the irregular structures, which shows that they are connected to vortex interactions, possibly vortex reconnexion.

Domaines: Mécanique des fluides [physics.class-ph]

Florian Nguyen, Jean-Philippe Laval, Bérengère Dubrulle. Characterizing most irregular small scale structures in turbulence using local Hölder exponents. Physical Review E , 2020, 102 (063105). ⟨hal-02514185v2⟩