Helicity Generation in Uniform Helical Flows
S. G. Chefranov
Oboukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow, 109017 Russia
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences,
Pushchino, Moscow oblast, 142292 Russia
Received July 14, 2003
AbstractHelicity generation conditions are derived for helical flows of Joukowski type with allowance for
effects due to viscosity, buoyancy, temperature nonuniformity, and solid-body rotation. The upper and lower
limits are determined for the rotation-frequency interval in which helicity can be generated by viscous forces.
These conditions correspond to the regime of an isolated tornado-like vortex. An exact solution to the time-inde-
pendent equations of motion for inviscid incompressible flow is obtained. The solution describes a generalized
KelvinHelmholtz vortex having the form of a localized cylindrical vortex with nontrivial stable topological
vortex-core structure determined by a finite value of helicity. For linear traveling inertia waves, which must have
uniform helical structure, a general representation is found that characterizes helical structures of different ori-
gin. © 2004 MAIK Nauka/Interperiodica.
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