Showing papers on "Vortex lattice method published in 1969"

Correlation of the vortex lattice method on rotor/wing configurations.

Abstract: The Hot Cycle Rotor/Wing is a new concept for high-speed vertical takeoff aircraft. It is a unique, dual-purpose lifting device that is basically a Hot Cycle helicopter rotor with an unusually large hub. It acts as a tip-jet-powered rotor for ver- tical and low-speed flight, and stops during flight to become a low-aspect-ratio, swept wing for high-speed cruise. By stopping the rotor in forward flight, the speed limitations of the helicopter rotor are removed, enabling more efficient cruise and operation at speeds up to 500 knots as a jet airplane. The single, dual-purpose lifting device combined with the simplicity and light weight of the Hot Cycle propulsion system holds promise of high payload capability superior to that of any other high-speed VTOL air- craft concept. Early low-speed wind-tunnel investigations2 of the concept considered the two planforms shown in Figs. 1 and 2 to the scale of the models. The tests of the circular and triangular hubs were conducted with the blades off and on in the stopped rotor mode. The reduced data include lift and pitching moment coefficients for angle of attack and rolling moment coefficient for antisymmetrical deflections of the left and right blades. Because the planforms are somewhat unconven- tional, methods of analysis for estimation of their aero- dynamic characteristics are rather limited. Perhaps the vortex lattice method of Hedman3 and the constant-pressure panel method of Woodward4 provide the only practical meth- ods of solution at this time. It is the purpose of this Note to present a correlation of the calculated results from Hed- man's method with the experimental data. Linearized estimates of the various measured coefficients are shown in Table 1. The reference area for the coefficients is the rotor disk area; the reference length for the moment coefficients is the rotor disk radius. The moments are taken about the disk center. Although many of the experimental