Nonuniversal behaviour of helical two-dimensional three-component turbulence

Area of Science:

• Fluid dynamics
• Magnetohydrodynamics
• Plasma physics

Background:

• Two-dimensional three-component (2D3C) flows are crucial for modeling long-time evolution of rotating or magnetized fluids.
• Understanding the behavior of the out-of-plane component is key to characterizing these complex systems.

Purpose of the Study:

• To investigate the dynamics of the out-of-plane component in 2D3C flows under strong helical forcing.
• To determine if the out-of-plane component remains a passive scalar or develops its own dynamics.
• To analyze the energy transfer mechanisms and large-scale properties influenced by helical forcing.

Main Methods:

• Numerical simulations of 2D3C fluid flows.
• Application of strong helical forcing at small scales.
• Analysis of correlations between 2D components and the out-of-plane component.
• Identification of energy transfer pathways, particularly homochiral triads.

Main Results:

• The out-of-plane component in 2D3C flows is not passive under helical forcing; it exhibits nontrivial dynamics.
• Small-scale helicity injection creates correlations between the 2D and out-of-plane components.
• A significant energy transfer develops in the third component, mediated by homochiral triads.
• The leading dynamical interactions are confirmed to be strongly three-dimensional.

Conclusions:

• Strong helical forcing fundamentally alters the behavior of the out-of-plane component in 2D3C flows.
• The out-of-plane component displays strong nonuniversal properties, dependent on the mirror symmetry of the small-scale forcing.
• These findings highlight the inherently three-dimensional nature of interactions in such systems, even when predominantly described in 2D.