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oai:riuma.uma.es:10630/375282026-02-03T10:59:50Zcom_10630_2254col_10630_37953

00925njm 22002777a 4500 dc Durán-Venegas, Eduardo author Le Dizès, Stéphane author 2019 New solutions describing the interaction of helical pairs of counter-rotating vortices are obtained using a vortex filament approach. The vortices are assumed to have a small core size allowing the calculation of the self-induced velocities from the Biot–Savart law using the cutoff theory. These new vortex structures do not possess any helical symmetry but they exhibit a spatial periodicity and are stationary in a rotating and translating frame. Their properties, such as radial deformation, frame velocity and induced flow, are provided as a function of the four geometric parameters characterizing each solution. Approximate solutions are also obtained when the mutual interaction is weak. This allows us to provide explicit expressions for the rotation and translation velocities of the structure in this limit. First-order corrections describing helix deformation are also calculated and used for comparison with the numerical results. The variation of the vortex core size induced by the helix deformation is also analysed. We show that these variations have a weak effect on the shape and characteristics of the solutions, for the range of parameters that we have considered. The results are finally applied to rotor wakes. It is explained how these solutions could possibly describe the far wake of an helicopter rotor in vertical flight. Durán Venegas E, Le Dizès S. Generalized helical vortex pairs. Journal of Fluid Mechanics. 2019;865:523-545. doi:10.1017/jfm.2019.65 https://hdl.handle.net/10630/37528 10.1017/jfm.2019.65 Mecánica de fluidos Generalized helical vortex pairs