Dresden 2026 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 8: Nonlinear Dynamics, Synchronization, and Chaos
DY 8.10: Vortrag
Montag, 9. März 2026, 12:15–12:30, ZEU/0118
Two-dimensional turbulent condensates without bottom drag — •Adrian van Kan1, Alexandros Alexakis2, and Edgar Knobloch3 — 1Department of Mathematics, Texas A&M University, College Station, USA — 2Laboratoire de Physique de l’Ecole Normale Supérieure, ENS, Université PSL, CNRS, Paris, France — 3Department of Physics, UC Berkeley, Berkeley, California, USA
The extent to which statistical equilibrium theory applies to driven dissipative dynamics remains an important open question in many systems. We use extensive direct numerical simulations of the incompressible two-dimensional (2D) Navier-Stokes equation to examine the steady state of large-scale condensates in 2D turbulence at finite Reynolds number Re in the absence of bottom drag. Large-scale condensates appear above a critical Reynolds number Rec≈ 4.19. For Re Rec, we find a power-law scaling of the energy with Re − Rec, with the energy spectrum at large scales following the absolute equilibrium form proposed by Kraichnan. At larger Re, the energy spectrum deviates from this form, displaying a steep power-law range at low wave numbers with exponent −5, with most of the energy dissipation occurring within the condensate at large scales. We show that this spectral exponent is consistent with the logarithmic radial vorticity profile of the viscously saturated condensate predicted by quasilinear theory. Our findings shed new light on the classical problem of large-scale turbulent condensation in forced dissipative 2D flows in finite domains, showing that the large scales are close to equilibrium dynamics in weakly turbulent flows but not for strong condensates (Re≫1).
Keywords: Two-dimensional turbulence; Large-scale turbulent condensation; Absolute equilibrium; Quasilinear theory; Direct numerical simulations