Numerical procedures based on the 2-D and 3-D full potential equations and the 2-D Navier-Stokes equations were developed to study the effects of leading and trailing edge flap motions on the aerodynamics of parallel airfoil-vortex interactions and on the aerodynamics and acoustics of the more general self-generated rotor blade vortex interactions (BVI). For subcritical interactions, the 2-D results indicate that the trailing edge flap can be used to alleviate the impulsive loads experienced by the airfoil. For supercritical interactions, the results show the necessity of using a leading edge flap, rather than a trailing edge flap, to alleviate the interaction. Results for various time dependent flap motions and their effect on the predicted temporal sectional loads, differential pressures, and the free vortex trajectories are presented. For the OLS model rotor, contours of a BVI noise metric were used to quantify the effects of the trailing edge flap on the size and directivity of the high/low intensity noise region(s). Average reductions in the BVI noise levels on the order of 5 dB with moderate power penalties on the order of 18 pct. for a four bladed rotor and 58 pct. for a two bladed rotor were obtained. Hassan, A. A. and Charles, B. D. and Tadghighi, H. and Sankar, L. N. Unspecified Center NASA-CR-4426, NAS 1.26:4426 NAS1-19136; RTOP 505-63-36...

This report describes a wind tunnel test of the McDonnell Douglas Helicopter Systems (MDHS) Active Flap Model Rotor at the NASA Langley 14- by 22-Foot Subsonic Tunnel. The test demonstrated that BVI noise reductions and vibration reductions were possible with the use of an active flap. Aerodynamic results supported the acoustic data trends, showing a reduction in the strength of the tip vortex with the deflection of the flap. Acoustic results showed that the flap deployment, depending on the peak deflection angle and azimuthal shift in its deployment schedule, can produce BVI noise reductions as much as 6 dB on the advancing and retreating sides. The noise reduction was accompanied by an increase in low frequency harmonic noise and high frequency broadband noise. A brief assessment of the effect of the flap on vibration showed that significant reductions were possible. The greatest vibration reductions (as much as 76%) were found in the four per rev pitching moment at the hub. Performance improvement cam results were inconclusive, as the improvements were predicted to be smaller than the resolution of the rotor balance. Dawson, Seth and Hassan, Ahmed and Straub, Friedrich and Tadghighi, Hormoz Langley Research Center BLADE-VORTEX INTERACTION; WIND TUNNEL TESTS; NOISE REDUCTION; AIRCRAFT CONTROL; FLAPS (CONTROL SURFACES); HELICOPTERS; AEROACOUSTICS; PRESSURE DISTRIBUTION; ACTIVE CONTROL; INTERACTIONAL AERODYNAMICS; VIBRATION EFFECTS; PITCHING MOMENTS; ROTOR DYNAMICS; SURFACE PROPERTIES; ROTOR BLADES; PRESSURE MEASUREMENT; NOISE SPECTRA; ACOUSTIC PROPERTIES; BLADE SLAP NOISE; DEFLECTION; FREQUENCIES; SUBSONIC SPEED; WING TIP VORTICES...

This book focuses on smart materials and structures, which are also referred to as intelligent, adaptive, active, sensory, and metamorphic. The ultimate goal is to develop biologically inspired multifunctional materials with the capability to adapt their structural characteristics, monitor their health condition, perform self-diagnosis and self-repair, morph their shape, and undergo significant controlled motion.