Helicity generation in uniform helical flows

Helicity 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-independent equations of motion for inviscid incompressible flow is obtained. The solution describes a generalized Kelvin-Helmholtz 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 origin.