Wind-tunnel Investigation at Low Speeds to Determine Flow-field Characteristics and Ground Influence on a Model with Jet-augmented Flaps
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Vogler, Raymond D↗
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Wind-tunnel investigation of the static longitudinal stability and trim characteristics of a sweptback-wing jet-transport model equipped with an external-flow jet augmented flap
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Johnson, Joseph L , Jr↗
Experimental study of acoustic loads on an upper-surface-blown STOL airplane configuration
Fluctuating pressure levels were measured on the flap and fuselage of an upper-surface-blown jet-flap airplane configuration in a wind tunnel. The model tested had turbofan engines with a bypass ratio of 3 and a thrust rating of 10 kN. Rectangular nozzles were mounted flush with the upper surface at 35 percent of the wing chord. Test parameters were flap deflection angle, jet impingement angle, angle of attack, free-stream velocity, spanwise location of the engine, and jet dynamic pressure. Load levels were high throughout the jet impingement region, with the highest levels (about 159 dB) occurring on the fuselage and near the knee of the flap. The magnitude of the forward-velocity effect appeared to depend upon the ratio of free-stream and jet velocities. Good agreement was obtained between fluctuating pressure spectra measured at jet dynamic pressures of 7 and 22 kPa when the spectra were scaled by nondimensional functions of dynamic pressure, velocity, and the empirical relationship between dynamic pressure and overall fluctuating pressure level.
Willis, C. M.↗
Experimental investigation of advanced concepts to increase turbine blade loading. I - Analysis and design
Increased turbine rotor blade loading through use of boundary layer control devices - vortex generator, tangential slot blowing, tandem airfoil, and jet flap
ROTOR BLADE↗
STOL aircraft transient ground effects. Part 2: Experimental techniques feasibility study
Procedures for simulating transient effects associated with STOL aircraft landings and takeoffs were examined and a basis was developed for selection of an experimental approach based on consideration of simulation requirements, experimental techniques, facilities, and costs. The results are generally applicable to STOL aircraft employing any of the following powered lift systems: externally blown flap, upper surface blown flap, augmentor wing, or internally ducted jet flap. Scaling relationships were developed to apply the simulation requirements to model test situations. Procedures for the derivation of aerodynamic forces from the measured data were discussed. Various means of expressing the aerodynamic data in forms convenient for use in performance or stability and control applications were described. Five different experimental techniques were presented that depend on two different types of experimental facilities, wind tunnels and test tracks, and involving different types of model motion, and factors pertinent to selection were summarized.
Crowder, J. P.↗
NASA-Lockheed short-haul transport study
Tilt-wing VTOL and jet-flap STOL designs for commercial passenger transport aircraft
TILT-WING AIRCRAFT↗
Externally blown flap trailing edge noise reduction by slot blowing: A preliminary study
Short takeoff and landing (STOL) aircraft using externally blown flaps (EBF) for lift augmentation develop considerable jet-flap interaction noise. A proposed method to reduce the EBF trailing edge noise is to locate a slot near the trailing edge of a flap through which low velocity secondary air is blown. Limited OASPL noise data were obtained from the interaction of the jet exhaust from a 5.08 cm diameter convergent nozzle with the trailing edge of a plate, and are presented for five slot configurations located near or at the trailing edge of the plate. Also presented are some significant jet trailing edge interaction data using a mixer nozzle with one of the slot configurations.
Mckinzie, D. J., Jr.↗
A wing-jet interaction theory for USB configurations
The aerodynamic interaction between the wing and an inviscid upper-surface blowing (USB) thick jet with Mach number nonuniformity is treated within the framework of a linear inviscid subsonic compressible flow theory. A two-vortex-sheet model for the jet surface is used to represent the induced flowfields inside and outside the jet. Comparison of the predicted results with experimental data shows good agreement in lift, induced drag, and pitching moment. It is shown that the thin jet flap theory is inadequate for USB configurations with thick jet.
Lan, C. E.↗
Blown flap noise research
Noise data with models of both internally and externally blown jet flaps designed for STOL aircraft
Dorsch, R. G.↗
Theoretical aerodynamics of upper-surface-blowing jet-wing interaction
A linear, inviscid subsonic compressible flow theory is formulated to treat the aerodynamic interaction between the wing and an inviscid upper-surface-blowing (USB) thick jet with Mach number nonuniformity. The predicted results show reasonably good agreement with some available lift and induced-drag data. It was also shown that the thin-jet-flap theory is inadequate for the USB configurations with thick jet. Additional theoretical results show that the lift and induced drag were reduced by increasing jet temperature and increased by increasing jet Mach number. Reducing jet aspect ratio, while holding jet area constant, caused reductions in lift, induced drag, and pitching moment at a given angle of attack but with a minimal change in the curve of lift coefficient against induced-drag coefficient. The jet-deflection effect was shown to be beneficial to cruise performance. The aerodynamic center was shifted forward by adding power or jet-deflection angle. Moving the jet away from the wing surface resulted in rapid changes in lift and induced drag. Reducing the wing span of a rectangular wing by half decreased the jet-circulation lift by only 24 percent at a thrust coefficient of 2.
Lan, C. E.↗
STOL aircraft transient ground effects. Part 1: Fundamental analytical study
The first phases of a fundamental analytical study of STOL ground effects were presented. Ground effects were studied in two dimensions to establish the importance of nonlinear effects, to examine transient aspects of ascent and descent near the ground, and to study the modelling of the jet impingement on the ground. Powered lift system effects were treated using the jet-flap analogy. The status of a three-dimensional jet-wing ground effect method was presented. It was shown, for two-dimensional unblown airfoils, that the transient effects are small and are primarily due to airfoil/freestream/ground orientation rather than to unsteady effects. The three-dimensional study showed phenomena similar to the two-dimensional results. For unblown wings, the wing/freestream/ground orientation effects were shown to be of the same order of magnitude as for unblown airfoils. This may be used to study the nonplanar, nonlinear, jet-wing ground effect.
Goldhammer, M. I.↗
Wind-tunnel investigation of an external-flow jet-augmented slotted flap suitable for application to airplanes with pod-mounted jet engines
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Campbell, John P↗
Stability and control of externally blown flap configurations
The results of wind-tunnel investigations on the stability and control characteristics of externally blown jet-flap configurations are presented. Conventional wind-tunnel tests and free-flight model tests have shown that longitudinal trim and stability can be achieved by a properly located horizontal tail of sufficient size, and that lateral trim in the engine-out condition can be produced by combinations of differential flap, spoiler, and rudder deflection. Free-flight model tests have revealed a lightly damped Dutch roll lateral oscillation, and have shown that the oscillation can be stabilized by use of artificial damping.
Parlett, L. P.↗
Wind tunnel investigation of a large-scale semispan model with an unswept wing and an upper-surface blown jet flat
An investigation of the static longitudinal aerodynamic characteristics of a large-scale semispan model with an unswept wing and an upper-surface blown jet flap for lift augmentation was conducted in the Langley full-scale tunnel. The wing had an aspect ratio of 7.8 (3.9 for the semispan) and a simulated turbofan engine mounted ahead of and above the wing in a nacelle with a rectangular-exit nozzle. The flap system had three spanwise flap segments: (1) an inboard plain flap located behind the engine and having a large radius of curvature to provide a smooth upper surface to enhance the turning of the jet sheet, (2) a double-slotted midspan flap, and (3) a drooped aileron equipped with blowing boundary-layer control. The wing was also equipped with a full-span leading-edge Krueger flap with blowing boundary-layer control. In addition to the aerodynamic measurements, noise measurements were also included in the investigation for positions above and below the wing.
Smith, C. C., Jr.↗
The aerodynamic characteristics of a propulsive wing/canard concept in STOL
The potential of the propulsive wing in developing very high lift coefficients for STOL operation has been investigated with several nozzle aspect ratios. The use of the propulsive wing/canard appears to offer an approach to managing the large negative pitching moments associated with trailing-edge blowing. A full-span model of a wing/canard concept representing a fighter configuration has been tested at STOL conditions in the Langley 4 by 7 Meter Tunnel. The results of this test are presented, and comparisons are made to previous tests of the same configuration tested as a semispan model (Stewrt, 1983). Also presented are data showing the effects of large flap deflection and the effect of nozzle span. Comparisons of the test results with jet-flap theory are made and indicate good agreement.
Stewart, V. R.↗
Application of empirical and linear methods to VSTOL powered-lift aerodynamics
Available prediction methods applied to problems of aero/propulsion interactions for short takeoff and vertical landing (STOVL) aircraft are critically reviewed and an assessment of their strengths and weaknesses provided. The first two problems deal with aerodynamic performance effects during hover: (1) out-of-ground effect, and (2) in-ground effect. The first can be evaluated for some multijet cases; however, the second problem is very difficult to evaluate for multijets. The ground-environment effects due to wall jets and fountain flows directly affect hover performance. In a related problem: (3) hot-gas ingestion affects the engine operation. Both of these problems as well as jet noise affect the ability of people to work near the aircraft and the ability of the aircraft to operate near the ground. Additional problems are: (4) the power-augmented lift due to jet-flap effects (both in- and out-of-ground effects), and (5) the direct jet-lift effects during short takeoff and landing (STOL) operations. The final problem: (6) is the aerodynamic/propulsion interactions in transition between hover and wing-borne flight. Areas where modern CFD methods can provide improvements to current computational capabilities are identified.
Margason, Richard↗
Application of empirical and linear methods to VSTOL powered-lift aerodynamics
Available prediction methods applied to problems of aero/propulsion interactions for short takeoff and vertical landing (STOVL) aircraft are critically reviewed and an assessment of their strengths and weaknesses provided. The first two problems deal with aerodynamic performance effects during hover: (1) out-of-ground effect, and (2) in-ground effect. The first can be evaluated for some multijet cases; however, the second problem is very difficult to evaluate for multijets. The ground-environment effects due to wall jets and fountain flows directly affect hover performance. In a related problem: (3) hot-gas ingestion affects the engine operation. Both of these problems as well as jet noise affect the ability of people to work near the aircraft and the ability of the aircraft to operate near the ground. Additional problems are: (4) the power-augmented lift due to jet-flap effects (both in- and out-of-ground effects), and (5) the direct jet-lift effects during short takeoff and landing (STOL) operations. The final problem: (6) is the aerodynamic/propulsion interactions in transition between hover and wing-borne flight. Areas where modern CFD methods can provide improvements to current computational capabilities are identified.
Margason, Richard↗
Aerodynamics of the upper surface blow flap
The results of some preliminary wind-tunnel investigations made to provide fundamental aerodynamic information on the upper surface blown jet-flap concept incorporating high-bypass-ratio turbofan engines are summarized. The results of the investigation have shown the concept to have aerodynamic performance generally similar to that of other externally blown high-lift systems. A few of the more critical problems associated with this concept have been identified and preliminary solutions to some of these problems have been found. These results have proven to be sufficiently encouraging to warrant continuation of fundamental research efforts on the concept.
Phelps, A. E., III↗