Additional Aerodynamic Features of Wing-Gurney Flap Flows

An extension of the existing explanation of the flow mechanisms characteristic of the wing-Gurney flap flow has been proposed. Based on the Helmholtz vortex theory, it has been postulated at the onset of the present study that, in addition to the spanwise vortices, as predicted by a commonly accepted flow hypothesis one or more pairs of streamwise trailing vortices ought to exist. A series of wind-tunnel models, including a clean wing and one full-span and two partial-span Gurney flaps, have been tested in a low-speed wind tunnel. Several techniques, including two methods of flow visualization of trailing vortices and measurements of rotational speeds produced by these vortices, have been employed. All of these methods have consistently and clearly indicated the presence of additional vortices. As such, these vortices are important for accurate prediction of the aerodynamic characteristics of wing-Gurney flap configurations.

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