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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Effects of wing leading-edge flap deflections on subsonic longitudinal aerodynamic characteristics of a wing-fuselage configuration with a 44 deg swept wing

An investigation was conducted to determine the effects of wing leading-edge flap deflections on the subsonic longitudinal aerodynamic characteristics of a wing-fuselage configuration with a 44 deg swept wing. The tests were conducted at Mach numbers from 0.40 to 0.85, corresponding to Reynolds numbers (based on wing mean geometric chord) of 2.37 x 1,000,000 to 4.59 x 1,000,000 and at angles of attack from -3 deg to 22 deg. The configurations under study included a wing-fuselage configuration and a wing-fuselage-strake configuration. Each configuration had multisegmented, constant-chord leading-edge flaps which could be deflected independently or in various combinations.

Henderson, W. P.↗
NASA NTRS1978

Blown flap noise prediction

Theoretical and experimental developments of flow-surface interaction noise with a particular emphasis on blown-flap noise were reviewed. Several blown-flap noise prediction methods were evaluated by comparing predicted acoustic levels, directivity, and spectra with a recently obtained data base. A prediction method was selected and a detailed step-by-step description of this method was provided to develop a computer module to calculate one-third octave band frequency spectra at any given location in the far-field for under-the-wing and upper surface blown configurations as a function of geometric and operational parameters.

Reddy, N. N.↗
NASA NTRS1979

Wind tunnel force and pressure tests of a 21% thick general aviation airfoil with 20% aileron, 25% slotted flap and 10% slot-lip spoiler

Force and surface pressure distributions were measured for the 21% LS(1)-0421 modified airfoil fitted with 20% aileron, 25% slotted flap and 10% slot lip spoiler. All tests were conducted at a Reynolds number of 2.2 x 10 to the 6th power and a Mach number of 0.13. The lift, drag, pitching moments, control surface normal force and hinge moments, and surface pressure distributions are included in the results. Incremental performance of flap and aileron are discussed and compared to the GA(W)-2 airfoil. Spoiler control which shows a slight reversal tendency at high alpha, is examined.

Wentz, W. H., Jr.↗
NASA NTRS1979

Two dimensional aerodynamic interference effects on oscillating airfoils with flaps in ventilated subsonic wind tunnels

The numerical computation of unsteady airloads acting upon thin airfoils with multiple leading and trailing-edge controls in two-dimensional ventilated subsonic wind tunnels is studied. The foundation of the computational method is strengthened with a new and more powerful mathematical existence and convergence theory for solving Cauchy singular integral equations of the first kind, and the method of convergence acceleration by extrapolation to the limit is introduced to analyze airfoils with flaps. New results are presented for steady and unsteady flow, including the effect of acoustic resonance between ventilated wind-tunnel walls and airfoils with oscillating flaps. The computer program TWODI is available for general use and a complete set of instructions is provided.

Fromme, J.↗
NASA NTRS1980

Wing flapping with minimum energy

For slow flapping motions it is found that the minimum energy loss occurs when the vortex wake moves as a rigid surface that rotates about the wing root - a condition analogous to that determined for a slow-turning propeller. The optimum circulation distribution determined by this condition differs from the elliptic distribution, showing a greater concentration of lift toward the tips. It appears that very high propulsive efficiencies are obtained by flapping.

Jones, R. T.↗
NASA NTRS1980

Airplane wing leading edge variable camber flap

The invention and design of an aerodynamic high lift device which provided a solution to an aircraft performance problem are described. The performance problem of converting a high speed cruise airfoil into a low speed aerodynamic shape that would provide landing and take-off characteristics superior to those available with contemporary high lift devices are addressed. The need for an improved wing leading edge device that would complement the high lift performance of a triple slotted trailing edge flap is examined. The mechanical and structural aspects of the variable camber flap are discussed and the aerodynamic performance aspects only as they relate to the invention and design of the device are presented.

Cole, J. B.↗
NASA NTRS1980

Computation of spanwise distribution of circulation and lift coefficient for flapped wings of arbitrary planform

The question of the effect of distribution and magnitude of spanwise circulation and shed vorticity from an airplane wing on the distribution pattern of agricultural products distributed from an airplane was studied. The first step in an analysis of this question is the determination of the actual distribution of lift along an airplane wing, from which the pattern of shed vorticity can be determined. A procedure is developed to calculate the span loading for flapped and unflapped wings of arbitrary aspect ratio and taper ratio. The procedure was programmed on a small programmable calculator, the Hewlett Packard HP-97, and also was programmed in BASIC language. They could be used to explore the variations in span loading that can be secured by variable flap deflections or the effect of flying at varying air speeds at different airplane gross weights. Either an absolute evaluation of span loading can be secured or comparative span loading can be evaluated to determine their effect on swath width and swath distribution pattern. The programs are intended to assist the user in evaluating the effect of a given spanload distribution.

Razak, K.↗
NASA NTRS1980

Noise radiation from the side edges of flaps

The recently observed phenomenon of high noise radiation from the side edges of flaps in flow is investigated by way of a simple two-dimensional model problem. The model is based upon a physical picture of boundary layer vorticity being swept around the edge by spanwise flow on the flap. The model problem is developed and solved and the resulting noise radiation calculated. Further, a mathematical condition for the vortex to be captured by the potential flow and swept around the edge is derived. The results show that the sound generation depends strongly upon the strength of the vorticity and distance from the edge and that it can be more intense than the more common trailing edge noise source in agreement with the experimental observations.

Hardin, J. C.↗
NASA NTRS1980

Noise generation at the side edges of flaps

The recently observed phenomenon of high noise radiation from the side edges of flaps is investigated by way of a two-dimensional model based upon a physical picture of chordwise boundary layer vorticity being swept around the edge by spanwise flow on the flap. The trajectory and resulting noise radiation for a discrete vortex in such a flow is obtained. Further, a mathematical condition for the vortex to be captured by the flow and swept around the edge is derived. The sound generation depends strongly upon the vortex strength and distance from the edge and can be more intense than trailing edge noise in agreement with experimental observations.

Hardin, J. C.↗
NASA NTRS1979

Low-speed aerodynamic performance of a high-aspect-ratio supercritical-wing transport model equipped with full-span slat and part-span double-slotted flaps

An investigation was conducted in the Langley V/STOL tunnel to determine the static longitudinal and lateral-directional aerodynamic characteristics of an advanced high-aspect-ratio supercritical-wing transport model equipped with a full-span leading-edge slat and part-span double-slotted trailing-edge flaps. This wide-body transport model was also equipped with spoiler and aileron control surfaces, flow-through nacelles, landing gear, movable horizontal tails, and interchangeable wing tips with aspect ratios of 10 and 12. The model was tested with leading-edge slat and trailing-edge flap combinations representative of cruise, climb, takeoff, and landing wing configurations. The tests were conducted at free-stream conditions corresponding to Reynolds numbers (based on mean geometric chord) of 0.97 to 1.63 x 10 to the 6th power and corresponding Mach numbers of 0.12 to 0.20, through an angle-of-attack range of -2 deg to 24 deg and a sideslip-angle range of -10 deg to 5 deg.

Morgan, H. L., Jr.↗
NASA NTRS1982

Aerosound from corner flow and flap flow

Noise generation at the edge of a wing flap is analyzed. The phenomenon as a single vortex moving around a corner in an incompressible, potential flow is modelled. Vortex image retarding effects are proposed as an explanation for small Strouhal numbers. The model surface pressures, sound pressures (using Curle's theory), and Mach number dependencies agree with wind tunnel experiments. A double pressure peak is found in the model (credited to image action) which is qualitatively similar to measured sound correlations. Incompressible flow aerosound calculations are discussed. The effects of a series of vortices moving in the same idealized potential flow are also studied. The vortices are assumed to be statistically independent so their intensities can be added. The frequency of appearance of the vortices are determined from measurements. Diffraction effects caused by the presence of the wing near the dipole sound radiators on the flap surfaces are included.

Meecham, W. C.↗
NASA NTRS1972

Low-speed aerodynamic characteristics of a model having a 42 deg swept low wing with a supercritical airfoil, double-slotted flaps, and a T-tail

A low speed wind tunnel test was conducted in the Langley V/STOL tunnel to determine the static longitudinal and lateral stability characteristics of a general research model which simulated an advance configuration for a commercial transport airplane with a T tail. The model had a 42 deg swept, aspect ratio 6.78 wing with a supercritical airfoil and a high lift system which consisted of a leading edge slat and a double slotted flap. Various slat and flap deflection combinations represented clean, take off, and landing configurations. Effects on the longitudinal and lateral aerodynamic characteristics were determined for two flow through, simulated engine nacelles located on the sides of the fuselage near the rear of the model.

Fournier, P. G.↗
NASA NTRS1973

Effects of wing height on low-speed aerodynamic characteristics of a model having a 42 deg swept wing, a supercritical airfoil, double-slotted flaps, and a low tail

A low speed investigation was conducted in the Langley V/STOL tunnel to determine the static longitudinal lateral stability characteristics of a general research model with the wing in a high position and a low position on the fuselage. The model had a wing with a quarter chord sweep of 42 deg, an aspect ratio of 6.78, a supercritical airfoil, and a high lift system which consisted of a leading edge slat and a double slotted flap. Various slat and flap deflections represented clean, take off, and landing configurations. A 45 deg swept horizontal tail located slightly below the fuselage center line was investigated with both the low and high wing configurations.

Fournier, P. G.↗
NASA NTRS1983

The application of parameter estimation to flight measurements to obtain lateral-directional stability derivatives of an augmented jet-flap STOL airplane

Flight experiments with an augmented jet flap STOL aircraft provided data from which the lateral directional stability and control derivatives were calculated by applying a linear regression parameter estimation procedure. The tests, which were conducted with the jet flaps set at a 65 deg deflection, covered a large range of angles of attack and engine power settings. The effect of changing the angle of the jet thrust vector was also investigated. Test results are compared with stability derivatives that had been predicted. The roll damping derived from the tests was significantly larger than had been predicted, whereas the other derivatives were generally in agreement with the predictions. Results obtained using a maximum likelihood estimation procedure are compared with those from the linear regression solutions.

Stephenson, J. D.↗
NASA NTRS1983

Flap effectiveness on subsonic longitudinal aerodynamic characteristics of a modified arrow wing

An investigation of the subsonic longitudinal aerodynamic characteristics of a modified arrow-wing model was conducted in the Langley 4- by 7-Meter Tunnel. This investigation addressed the effectiveness of the leading and trailing edge flap deflections of this model. The arrow wing was tested at a Mach number of 0.02 and at an angle-of-attack range from -4 deg to 24 deg. The results of the investigation showed that deflecting the leading edge and trailing edge in combination could promote an attached-flow condition at the wing leading edge. Also, the leading edge suction could be maximized over the complete lift-coefficient range by scheduling a combination of leading and trailing edge flap deflections.

Quinto, P. F.↗
NASA NTRS1984

Investigation of trailing-edge-flap, spanwise-blowing concepts on an advanced fighter configuration

The aerodynamic effects of spanwise blowing on the trailing edge flap of an advanced fighter aircraft configuration were determined in the 4 by 7 Meter Tunnel. A series of tests were conducted with variations in spanwise-blowing vector angle, nozzle exit area, nozzle location, thrust coefficient, and flap deflection in order to determine a superior configuration for both an underwing cascade concept and an overwing port concept. This screening phase of the testing was conducted at a nominal approach angle of attack from 12 deg to 16 deg; and then the superior configurations were tested over a more complete angle of attack range from 0 deg to 20 deg at tunnel free stream dynamic pressures from 20 to 40 lbf/sq ft at thrust coefficients from 0 to 2.

Paulson, J. W., Jr.↗
NASA NTRS1984

Unsteady wake measurements of an oscillating flap at transonic speeds

The steady and unsteady wake profiles of an airfoil with an oscillating flap were measured at nominal free stream Mach number of 0.8 in the NASA Ames 11 x 11-foot wind tunnel. The instantaneous wake velocity and pressure profiles at four axial locations are presented up to one chord length from the trailing edge. Both fundamental harmonic frequency and typical time history data are presented to observe the effects of airfoil incidence and flap angle. The drag coefficient obtained from the wake pressure measurements is compared with that obtained from the airfoil pressure distribution.

Bodapati, S.↗
NASA NTRS1984

The lateral-directional characteristics of a 74-degree Delta wing employing gothic planform vortex flaps

The low speed lateral/directional characteristics of a generic 74 degree delta wing body configuration employing the latest generation, gothic planform vortex flaps was determined. Longitudinal effects are also presented. The data are compared with theoretical estimates from VORSTAB, an extension of the Quasi vortex lattice Method of Lan which empirically accounts for vortex breakdown effects in the calculation of longitudinal and lateral/directional aerodynamic characteristics. It is indicated that leading edge deflections of 30 and 40 degrees reduce the magnitude of the wing effective dihedral relative to the baseline for a specified angle of attack or lift coefficient. For angles of attack greater than 15 degrees, these flap deflections reduce the configuration directional stability despite improved vertical tail effectiveness. It is shown that asymmetric leading edge deflections are inferior to conventional ailerons in generating rolling moments. VORSTAB calculations provide coarse lateral/directional estimates at low to moderate angles of attack. The theory does not account for vortex flow induced, vertical tail effects.

Grantz, A. C.↗