On concentrated vortices of 3D incompressible Euler equations under helical symmetry: with swirl

In this paper, we consider the existence of concentrated helical vortices of 3D incompressible Euler equations with swirl. First, without the assumption of the orthogonality condition, we derive a 2D vorticity-stream formulation of 3D incompressible Euler equations under helical symmetry. Then based on this system, we deduce a non-autonomous second order semilinear elliptic equations in divergence form, whose solutions correspond to traveling-rotating invariant helical vortices with non-zero helical swirl. Finally, by using Arnold's variational method, that is, finding maximizers of a properly defined energy functional over a certain function space and proving the asymptotic behavior of maximizers, we construct families of concentrated traveling-rotating helical vortices of 3D incompressible Euler equations with non-zero helical swirl in infinite cylinders. As parameter $ \varepsilon\to0 $, the associated vorticity fields tend asymptotically to a singular helical vortex filament evolved by the binormal curvature flow.