Compressible helical turbulence: Fastened-structure geometry and statistics

TL;DR

This paper investigates how flow compressibility and helicities relate to the geometry and statistics of helical turbulence across various fluid models, revealing universal behaviors and underlying structural principles.

Contribution

It introduces a geometrical framework linking flow invariants and helicities to turbulence statistics, applicable to neutral and ionized gases.

Findings

Flow compressibility reduction correlates with helicities.

A geometrical scenario explains universal turbulence behaviors.

Electric field fluctuations are influenced by plasma helicities.

Abstract

Reduction of flow compressibility with the corresponding ideally invariant helicities, universally for various fluid models of neutral and ionized gases, can be argued statistically and associated with the geometrical scenario in the Taylor-Proudman theorem and its analogues. A `chiral base flow/field', rooted in the generic intrinsic local structure, as well as an `equivalence principle' is explained and used to bridge the single-structure mechanics and the helical statistics. The electric field fluctuations may similarly be depressed by the (self-)helicities of the two-fluid plasma model, with the geometry lying in the relation between the electric and density fields in a Maxwell equation.