Jet circulation control airfoil for VTOL rotors

Abstract

Based on the potential flow theory calculation, the capacity of the air supply, the limitation of the internal pressure of the model and the limitation due to the compressibility effect of the jet stream at high velocities, the elliptical airfoils of 18 and 12% thickness ratios were designed and constructed. Experimental investigations for both models with trailing-edge jets include force and pitching moment measurements. In addition, static pressure measurements were made in both span wise and chord wise directions. These results were used to compare with available theories as well as other experimental data. Circulation control with dual jets for the elliptical airfoil of 18% thickness ratio was tested with very satisfactory results. The determination of the aerodynamic response of the airfoil model to cyclic changes in jet mass flow was also made. The cyclic results were very satisfactory and are presented in the form of pulsating lift coefficient, drag coefficient, and pressure coefficient as a function of pulsating jet coefficient. NomenclatureFluid and flow properties p = pressure p m = freestream pressure Q = AjVj, volume flow rate of jet, ft 3 /sec u = local velocity relative to airfoil t/max = maximum potential flow velocity (at minimum pressure point) [/co = freestream velocity Vj = jet fluid velocity relative to airfoil