2 research outputs found
New Exact Betchov-like Relation for the Helicity Flux in Homogeneous Turbulence
In homogeneous and isotropic turbulence, the relative contributions of
different physical mechanisms to the energy cascade can be quantified by an
exact decomposition of the energy flux (P. Johnson, Phys. Rev. Lett., 124,
104501 (2020), J. Fluid Mech. 922, A3(2021)). We extend the formalism to the
transfer of kinetic helicity across scales, important in the presence of
large-scale mirror breaking mechanisms, to identify physical processes
resulting in helicity transfer and quantify their contributions to the mean
flux in the inertial range. All subfluxes transfer helicity from large to small
scales. About 50% of the mean flux is due to the scale-local vortex flattening
and vortex twisting. We derive a new exact relation between these effects,
similar to the Betchov relation for the energy flux, revealing that the mean
contribution of the former is three times larger than that of the latter.
Multi-scale effects account for the remaining 50% of the mean flux, with
approximate equipartition between multi-scale vortex flattening, twisting and
entangling