Aero-Effected Flight Control Using Distributed Active Bleed

Abstract

The public reporting burden for this collection l:>f inforTTilltion is estimab:d to avefllge 1 hour per response, including the time for reviewing instructions, seen::hing existing data soun::es, gllllhering and maintaining the data needed, and completing and reviewing tha collection l:>f Information. Send ocmmenla regarding this burden estimate or any other aspectl:>f this collection l:>f Information, Including suggestions for reducing the burden, to the Department l:>f Defense, Exeoutive Servioe Directorab: (07() SPONSOR/MONITOR'S REPORTArlington, VA 22203 NUMBER(S)AFRL-OSR-VA-TR-2012-0276 DISTRIBUTION/AVAILABILITY STATEMENT Unlimited SUPPLEMENTARY NOTES14. ABSTRACT Aero-ettected flight control us1ng dlstnbuted act1ve bleed dnven by pressure dltterences on 11tt1ng surfaces and regulated by low-power louver actuators was investigated experimentally and theoretically. The flow mechanisms of the interaction between unsteady bleed and the cross flows were investigated on a 2-D static and dynamically pitching Clark-Y model integrated with piezoelectric louvers. The effects of leading and trailing edge bleed on the aerodynamic forces and the flow field were measured using load cells and PIV. Trailing edge bleed at low AoA effects nearly-linear variation of the pitching moment (±12%) with minimal drag penalty. Leading edge bleed at high AoA leads to large variations in lift and pitching moment, and extends the stall margin enabling up to 50% variation in the baseline lift without external control surfaces. Numerical simulations using immersed boundary and penalty methods, showed that the bleed near the trailing edge induced changes in circulation to maintain the Kutta condition. This change in circulation accounts for 5!7 of the total change in lift with center-of-pressure at c/4, in accordance with classical theory. A vortex-based reduced order model was developed to predict aerodynamic forces on an arbitrarily pitching and plunging airfoil with unsteady bleed. Bleed actuation was also investigated on a pitching airfoil over a wide range of AoA. At high reduced frequencies (k > 0.1 ), the bleed alters the dynamics of vorticity production and advection and interacts with the dynamic stall vortex to increase the stability of the pitch motion and minimize negative damping with low lift penalty. SUBJECT TERMS AbstractA novel, scalable approach to aero-effected flight control of lifting surfaces using distributed active bleed was investigated experimentally and theoretically. Aerodynamic control is achieved by large-area surface bleed of air that is driven by the pressure differences in flight and is regulated by low-power surface-integrated louver actuators. The joint numerical-experimental investigation focused on the flow mechanisms of the interaction between the bleed and the cross flow and aerodynamic effects of unsteady bleed on a 2-D wing model. Particular emphasis was placed on the generation and regulation of vorticity concentrations that alter the wing's apparent aerodynamic shape and thereby its aerodynamic ...