Spontaneous suppression of inverse energy cascade in instability-driven 2D turbulence

Abstract

Instabilities of fluid flows often generate turbulence. Using extensive direct numerical simulations, we study two-dimensional turbulence driven by a wavenumber-localised instability superposed on stochastic forcing, in contrast to previous studies of state-independent forcing. As the contribution of the instability forcing, measured by a parameter $\gamma$, increases, the system undergoes two transitions. For $\gamma$ below a first threshold, a regular large-scale vortex condensate forms. Above this threshold, shielded vortices (SVs) emerge within the condensate. At a second, larger value of $\gamma$, the condensate breaks down, and a gas of weakly interacting vortices with broken symmetry spontaneously emerges, characterised by preponderance of vortices of one sign only and suppressed inverse energy cascade. The latter transition is shown to depend on the damping mechanism. The number density of SVs in the broken symmetry state slowly increases via a random nucleation process. Bistability is observed between the condensate and mixed SV-condensate states. Our findings provide new evidence for a strong dependence of two-dimensional turbulence phenomenology on the forcing.

References in corpus (16)

• Meso-scale turbulence in living fluids
• Cascades and transitions in turbulent flows
• Turning bacteria suspensions into a "superfluid"
• Multistability and memory effect in a highly turbulent flow: experimental evidence for a global bifurcation
• Dimensional transition in rotating turbulence
• Phase transition to large scale coherent structures in 2d active matter turbulence
• Subcritical turbulent condensate in rapidly rotating Rayleigh-Bénard convection
• Geometry-dependent viscosity reduction in sheared active fluids
• Condensates in thin-layer turbulence
• Dimensional transition of energy cascades in stably stratified thin fluid layers
• Dynamics of Saturated Energy Condensation in Two-Dimensional Turbulence
• Phase transitions in optical turbulence
• Rare transitions to thin-layer turbulent condensates
• Dipoles and streams in two-dimensional turbulence
• Nonuniversal transition to condensate formation in two-dimensional turbulence
• Collective organisation and screening in two-dimensional turbulence