Prospects Of Using Zero-Mass “Synthetic” Jets For Improved Helicopter/Tiltrotor Aerodynamic Performance

Using modified versions of the NASA Ames “ARC2D” and the US Army “2DBVI” two-dimensional Navier-Stokes flow solvers, studies were conducted to illustrate the beneficial aerodynamic effects that result from the use of macro-sized array(s) of zero-mass jets (AZMJ) on lifting aerodynamic surfaces (e.g., airfoils, wings, rotor blades, etc.). Specifically, using the NACA-0012 airfoil as a representative aerodynamic configuration, the following is demonstrated: a) the improved lift capability of the airfoil, b) the strong similarities that exist between the aerodynamic effects that result from the use of a conventional integral-type trailing edge flap and those which result from the use of two AZMJ, and c) the use of two AZMJ to alleviate the impulsive aerodynamic response of the airfoil while encountering a moving line vortex (model problem for the more general helicopter rotor blade-vortex interaction, BVI, problem). Close-up views of the predicted particle trajectories in the vicinity of the AZMJ are presented at selected times during one complete jet oscillation cycle to provide insight into the unsteady nature of the interaction between the jets and the developing boundary layer. The potential benefits of using array(s) of zero-mass jets to improve the aerodynamics of conventional helicopters and tiltrotor aircraft is also addressed. Results from the numerical simulations suggest that the peak jet velocity and the jet oscillation frequency are the prime parameters which affect the attained mean lift, drag and pitching moment levels. For rotor BVI applications, if the objective is to alleviate the blade leading edge temporal pressures, timing of the “activation” and “de-activation” of the AZMJ is critical for successful control.Using modified versions of the NASA Ames “ARC2D” and the US Army “2DBVI” two-dimensional Navier-Stokes flow solvers, studies were conducted to illustrate the beneficial aerodynamic effects that result from the use of macro-sized array(s) of zero-mass jets (AZMJ) on lifting aerodynamic surfaces (e.g., airfoils, wings, rotor blades, etc.). Specifically, using the NACA-0012 airfoil as a representative aerodynamic configuration, the following is demonstrated: a) the improved lift capability of the airfoil, b) the strong similarities that exist between the aerodynamic effects that result from the use of a conventional integral-type trailing edge flap and those which result from the use of two AZMJ, and c) the use of two AZMJ to alleviate the impulsive aerodynamic response of the airfoil while encountering a moving line vortex (model problem for the more general helicopter rotor blade-vortex interaction, BVI, problem). Close-up views of the predicted particle trajectories in the vicinity of the AZMJ are presented at selected times during one complete jet oscillation cycle to provide insight into the unsteady nature of the interaction between the jets and the developing boundary layer. The potential benefits of using array(s) of zero-mass jets to improve the aerodynamics of conventional helicopters and tiltrotor aircraft is also addressed. Results from the numerical simulations suggest that the peak jet velocity and the jet oscillation frequency are the prime parameters which affect the attained mean lift, drag and pitching moment levels. For rotor BVI applications, if the objective is to alleviate the blade leading edge temporal pressures, timing of the “activation” and “de-activation” of the AZMJ is critical for successful control.