Coherent vortex structures over a rotating spinner under non-axial inflows at low Reynolds number
S.S. Tambe (TU Delft - Flight Performance and Propulsion)
FFJ Schrijer (TU Delft - Aerodynamics)
A Gangoli Rao (TU Delft - Flight Performance and Propulsion)
L. L.M. Veldhuis (TU Delft - Flight Performance and Propulsion)
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Abstract
Boundary layer instabilities and the formation of coherent spiral vortices over a rotating cone and ellipsoid are studied experimentally. It is found that under a non-axial inflow, the breaking of symmetry in the flow field significantly disturbs the coherence and delays the formation of spiral vortices to higher local Reynolds numbers (Re_l) and higher rotation ratios (S). Consequently, it also delays boundary layer transition region. A conceptual reasoning for the observed phenomena is given based on the sensitivity of the local spiral vortex characteristics (number n and angle ϵ) to the asymmetry in the local rotation ratios.