2023/03/04 by Nobumitsu Yokoi, Yokoi, Nobumitsu
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Astro and Planetary Science #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Geomagnetism and Paleomagnetism Studies #Geophysics (physics.geo-ph) #Plasma Physics (physics.plasm-ph) #Solar and Space Plasma Dynamics #Solar and Stellar Astrophysics (astro-ph.SR)
paper · pdf · doi:10.48550/arxiv.2303.02414
openalex publication_date 2023/03/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Kinetic helicity (hereafter helicity) is defined by the correlation between the velocity and the flow-aligned vorticity. Helicity, as well as energy, is an inviscid invariant of the hydrodynamic equations. In contrast to energy, a measure of the turbulent intensity, turbulent helicity, representing right- and left-handed twist associated with a fluctuating motion, provides a measure of the structural or topological property of the fluctuation. The helicity effect on the turbulent transport can be analytically obtained in the framework of the multiple-scale renormalized perturbation expansion theory through the inclusion of the non-reflectionally-symmetric part for the lowest-order (homogeneous and isotropic) velocity correlation. The physical significance of the helicity-related contribution to the momentum transport is explained. By utilizing the analytical expression of the Reynolds stress, a turbulence model with helicity effect incorporated (helicity model) is constructed. This helicity model is applied to a swirling flow to show its validity in describing the prominent properties of the flow. In addition to the transport suppression, inhomogeneous helicity coupled with a rotation can induce a large-scale flow. The results of direct numerical simulations (DNSs) confirming the global flow generation by helicity will be also reviewed, followed by several possible applications in geo- and astro-physical flow phenomena.