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AND MARTIN LESSENÛ niversity of Rochester, Rochester, N. Y.The stability of a continuous model for the far wake of a hovering rotor has been formulated and analyzed. In the continuous model representation of the far wake, the vorticity of the interdigitated circular vortex helices is assumed to be distributed over a vortex sheet, and the potential flow inside and outside of the vortex sheet is taken to correspond to the average velocity profiles calculated for an interdigitated representation. A continuum of instabilities is found to exist for all wave numbers and for all modes except in some specific situations where the flow is neutrally stable. This model gives the instabilities of the gross flow and complements the interdigitated analysis of Ref. 1 which is the companion analysis for the instabilities of centerline displacements of the vortex helices.

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