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Erschienen in: Flow, Turbulence and Combustion 2/2018

16.07.2018

A Numerical Study of the Flow Around a Model Winged Seed in Auto-Rotation

verfasst von: Gonzalo Arranz, Alejandro Gonzalo, Markus Uhlmann, Oscar Flores, Manuel García-Villalba

Erschienen in: Flow, Turbulence and Combustion | Ausgabe 2/2018

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Abstract

In this study the flow around a winged-seed in auto-rotation is characterized using direct numerical simulations (DNS) at Reynolds number in the range 80–240, based on the descent speed and a characteristic chord length. In this range, the flow is approximately steady when observed from a reference frame fixed to the seed. For all cases, the flow structure consists of a wing tip vortex which describes a helical path, a vortex shed behind the nut of the seed and a stable leading edge vortex above the wing surface which merges with the tip vortex. With increasing Reynolds number, the leading edge vortex becomes more intense and gets closer to the wing surface. The simulation results also show the formation of a spanwise flow on the upper surface of the wing, moving fluid towards the wing tip in a region downstream and beneath the leading edge vortex. This spanwise flow is rather weak inside the core of the leading edge vortex, and the analysis of the streamlines show a very weak transport of vorticity along the vortex for the cases under consideration. The analysis of the flow suggests that the stabilization of the leading edge vortex is mainly due to non-inertial accelerations, although viscous effects may contribute, specially at lower Re. Furthermore, the leading edge vortex has been characterized by analysing the flow variables averaged along cross-sections of the vortex. While some quantities, like the spanwise velocity or the pressure inside the vortex, are rather insensitive to the threshold used to define the leading edge vortex, the same is not true for the circulation of the vortex or its averaged spanwise vorticity, due to the viscous nature of the vortex. Finally, it is observed that the spanwise vorticity scales with the angular rotation of the seed for the different Re.

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Metadaten
Titel
A Numerical Study of the Flow Around a Model Winged Seed in Auto-Rotation
verfasst von
Gonzalo Arranz
Alejandro Gonzalo
Markus Uhlmann
Oscar Flores
Manuel García-Villalba
Publikationsdatum
16.07.2018
Verlag
Springer Netherlands
Erschienen in
Flow, Turbulence and Combustion / Ausgabe 2/2018
Print ISSN: 1386-6184
Elektronische ISSN: 1573-1987
DOI
https://doi.org/10.1007/s10494-018-9945-z

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