Actuator Discs
Propeller
Conway has shown that the propeller effects on a potential flow environment can be represented by the superposition of known-strength vortex systems that satisfy both the Helmholtz Laws of vorticity as well as the propeller actuator conditions.
FlightStream utilizes the superposition of two vortex systems of the same vortex strength. The time-average of the bound and shed vorticity of the propeller is the superposition of the vorticity distributions in the plane of the propeller and the slipstream. There are two propeller vortex distributions which induce perturbations to the free-stream flow. The first is a lifting-line vortex horseshoe system simulating the lifting-line solution of a propeller disc made up of infinite numbers of blades. Such a system has the same vortex strength for all of its lifting-lines. The trailing vortices of the horseshoe system are made up of on strand shed along the axis of the disc and the other shed along tip of the disc. The system is shown in Figure-8(a). The second system of vortices are the shed vortex rings as shown in Figure-8(b). Such a system forms a vortex tube consisting of ring vortices distributed over the tube surface from the edge of the actuator disk and extending downstream to the Trefftz plane. The tube of ring vortices result from the root and tip vortices shed from the lifting lines in the actuator disc and as such also are assumed to have the same vortex strength as that of the lifting-line system
