EFFECTS OF ZERO-MASS SYNTHETIC JETS ON THE AERODYNAMICS OF THE NACA-0012 AIRFOIL

A numerical study was conducted to investigate the effect of an array of zero-mass ''synthetic'' jets on the aerodynamic characteristics of the NACA-0012 airfoil. Flowfield predictions were made using a modifie d version of the NASA Ames ''ARC2D'' unsteady, two-dimensional, compre ssible Navier-Stokes flow solver. An unsteady surface transpiration bo undary condition was enforced over a user-specified portion of the air foil's upper and/or lower surface to emulate the time variation of the mass flux out from and into the airfoil's surface. Here, a sinusoidal function which describes the approximate time behavior of the instant aneous mass flux across the airfoil's surface was used. Numerical resu lts have indicated that zero-mass jets can, with the careful selection of their peak amplitude and frequency, enhance the lift characteristi cs of airfoils (helicopter rotor blades, wings, etc.). Effects of the jet peak suction and blowing velocities, oscillation frequency, and je t surface placement on the time histories of the sectional lift, drag and moment are presented for two angles of attack and a free stream Ma ch number of 0.60. Flowfield results that provide insight into the mec hanics of the interaction between the array of jets and the developing boundary layer over the airfoil are presented.