Interaction of Helical Modes in Formation of Vortical Structures in Decaying Isotropic Turbulence

概要

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A transition process from vortex layers into vortex tubes through the Kelvin-Helmholtz instability in decaying homogeneous turbulence is studied numerically in terms of the helical decomposition. For smooth initial conditions high-vorticity regions with positive and negative helicity generally take the form of blobs. In the early stage with almost inviscid dynamics these blobs become flatter and layer-like, approaching simultaneously each other. In the next stage a pair of high-vorticity strips with opposite-signed helicity attach each other. It forms a precursor of a vortex tube with an internal dipole structure, which corresponds to the surrounding dipoles of high energy-dissipation. At later times two high-vorticity tubes with opposite-signed helicity join in series into a single vortex tube. They are separated again by the viscous diffusion. The recovery to a reflectional symmetry state is also studied using a strongly helical initial condition.
社団法人日本物理学会の論文
1994-06-15