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Rotor Vortex Filaments: Living on the Slipstream's EdgeThe purpose of this paper is to gain a better understanding of rotor wake evolution in hover and axial flow by deriving an analytical solution for the time dependent behavior of vortex filament circulation and core size. This solution is applicable only for vortex filaments in the rotor far-wake. A primarily inviscid vortex/shear layer interaction (where the slipstream boundary is modeled as a shear layer) has been identified in this analytical treatment. This vortex/shear layer interaction results in decreasing, vortex filament circulation and core size with time. The inviscid vortex/shear layer interaction is shown, in a first-order treatment, to be of greater magnitude than viscous diffusion effects. The rate of contraction, and ultimate collapse, of the vortex filament core is found to be directly proportional to the rotor inflow velocity. This new insight into vortex filament decay promises to help reconcile several disparate observations made in the literature and will, hopefully, promote new advances in theoretical modeling of rotor wakes.
Document ID
19970011043
Acquisition Source
Ames Research Center
Document Type
Technical Memorandum (TM)
Authors
Young, Larry A. (NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1997
Subject Category
Aerodynamics
Report/Patent Number
NASA-TM-110431
A-975569
NAS 1.15:110431
Accession Number
97N16092
Funding Number(s)
PROJECT: RTOP 505-59-36
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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