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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Viscous-flow analysis of a subsonic transport aircraft high-lift system and correlation with flight data

High-lift system aerodynamics has been gaining attention in recent years. In an effort to improve aircraft performance, comprehensive studies of multi-element airfoil systems are being undertaken in wind-tunnel and flight experiments. Recent developments in Computational Fluid Dynamics (CFD) offer a relatively inexpensive alternative for studying complex viscous flows by numerically solving the Navier-Stokes (N-S) equations. Current limitations in computer resources restrict practical high-lift N-S computations to two dimensions, but CFD predictions can yield tremendous insight into flow structure, interactions between airfoil elements, and effects of changes in airfoil geometry or free-stream conditions. These codes are very accurate when compared to strictly 2D data provided by wind-tunnel testing, as will be shown here. Yet, additional challenges must be faced in the analysis of a production aircraft wing section, such as that of the NASA Langley Transport Systems Research Vehicle (TSRV). A primary issue is the sweep theory used to correlate 2D predictions with 3D flight results, accounting for sweep, taper, and finite wing effects. Other computational issues addressed here include the effects of surface roughness of the geometry, cove shape modeling, grid topology, and transition specification. The sensitivity of the flow to changing free-stream conditions is investigated. In addition, the effects of Gurney flaps on the aerodynamic characteristics of the airfoil system are predicted.

Potter, R. C.↗
NASA NTRS1979

Data and analysis procedures for improved aerial applications mission performance

An analysis procedure is given and cases analyzed for the effects of wing geometry on lateral transport of a variety of agricultural particles released in the wake of an agricultural airplane. The cases analyzed simulate the release of particles from a fuselage centerline-mounted dry material spreader; however, the procedure applies to particles released anywhere along the wing span. Consideration is given to the effects of taper ratio, aspect ratio, wing loading, and deflected flaps. It is noted that significant lateral transport of large particles can be achieved using high-lift devices positioned to create a strong vortex near the location of particle release.

Holmes, B. J.↗
NASA NTRS1961

A Wind-Tunnel Investigation of a Transonic-Transport Configuration Utilizing Drag-Reducing Devices at Mach Numbers from 0.20 to 1.03

The static longitudinal stability and control and lateral characteristics of a transonic-transport model, incorporating recent drag-reducing devices, has been investigated in the Langley 8-foot transonic pressure tunnel. The wing was cambered, had a thickened root and a taper ratio of 0.3. Wing sweepback angles of 45 degrees and 40 degrees were investigated with corresponding aspect ratios of 7 and 8, respectively. Modifications to the model for reducing the drag were: a forward fuselage addition and special bodies (four big enough to house jet engines) added to the upper surface of the wing. Other components and changes investigated included an empennage, a wing-tip body, wing fences, wing trailing-edge flaps, horizontal-tail settings, and wing dihedral angle. The investigation covered the Mach number range from 0.20 to 1.03 for the angle-of-attack range from -5 degrees to 15.4 degrees, and a sideslip angle of -5 degrees, in the Reynolds number range from 0.52 times 10(exp 6) to 1.94 times 10(exp 6) based on the wing mean aerodynamic chord. The various fuselage and wing additions delayed the drag-rise Mach number and greatly reduced the drag beyond the drag rise. The wing bodies markedly alleviated unstable pitch tendencies throughout the test Mach number range. At low landing speeds, the wing bodies exhibited little interference with the ability of trailing-edge flaps to increase the lift near maximum lift coefficient; and the use of fences greatly reduced the severe longitudinal instability trend at landing attitudes. The model with a 6 degree dihedral angle exhibited positive lateral and directional stability characteristics in the presence of the fuselage and wing additions. An increase in drag-rise Mach number associated with the fuselage and wing additions on the 40 degree sweptback wing combination was similar to that for the comparable 45 degree combination. These additions did, however, reduce the drag of the 40 degree sweptback configurations more than the 45 degree configurations in the transonic speed range.

Loving, Donald L.↗
NASA NTRS1983

Flutter analysis of a transport wing using XTRAN3S

As part of the continuing process of evaluating and validating the XTRAN3S unsteady transonic aerodynamic computer program, the code has been applied to the flutter analysis of a transport type wing. The configuration analyzed was an aspect ratio 8 wing with a taper ratio of 0.4, a quarter chord sweep of 20 degrees and a NACA 65A-012 airfoil section. The analytical results compare well with the experimental flutter boundary and exhibit the classical 'transonic dip'. A literature search of available transport wing transonic flutter data is included.

Myers, M. R.↗
NASA NTRS1976

Experimental aerodynamic characteristics for slender bodies with thin wings and tail at angles of attack from 0 deg to 58 deg and Mach numbers from 0.6 to 2.0

An experimental investigation was conducted by wind tunnel to measure the static aerodynamic characteristics for bodies of circular and elliptic cross section with various thin flat plate wings and a thin tail consisting of horizontal and vertical parts. The wings had aspect ratios of 4 and taper ratios of about 0, 0.25, and 0.5. Two additional wings, which had taper ratios near 0.25 and aspect ratios of about 3 and 5, were also tested in combination with the bodies and tail. All wings had about the same planform area. The exposed area of the horizontal portion of the tail was about 33 to 36 percent of the exposed area of the wings. The exposed area of the vertical tail fin was about 22 to 24 percent of the exposed area of the wings. The elliptic body, with an a/b = 2 cross section, had the same length and axial distribution of cross sectional area as the circular body. The circular body had a cylindrical aftersection of fineness ratio 7, and it was tested with the wings and tail in combination with tangent ogive noses that had fineness ratios of 2.5, 3.0, 3.5, and 5.0. In addition, an ogive nose with a rounded tip and an ogive nose with two different nose strake arrangements were used. Nineteen configuration combinations were tested at Mach numbers of 0.6, 0.9, 1.5, and 2.0 at angles of attack from 0 to 58 deg. The Reynolds numbers, based on body base diameter, were about 4.3 X 100,000.

Jorgensen, L. H.↗
NASA NTRS1977

Pressure distributions on a 1- by 3-meter semispan wing with a nonstreamwise tip in subsonic flow

Pressure distributions on a 1- by 3-meter semispan wing with a tip that is streamwise at 0 deg sweep are presented. The tip becomes nonstreamwise as the wing is swept. At 0 deg sweep angle, the semispan wing has a taper ratio of 1.0 and NACA 0012 airfoil section contours. The test was conducted in the Langley V/STOL tunnel at a freestream dynamic pressure of 2.46 kPa. Pressure distributions are presented for sweep angles of 10, 20, 30, and 40 with an angle of attack range from -6 deg to 20 deg. The data are presented without analysis or discussion.

Yip, L. P.↗
NASA NTRS1985

A method for estimating the rolling moment due to spin rate for arbitrary planform wings

The application of aerodynamic theory for estimating the force and moments acting upon spinning airplanes is of interest. For example, strip theory has been used to generate estimates of the aerodynamic characteristics as a function of spin rate for wing-dominated configurations for angles of attack up to 90 degrees. This work, which had been limited to constant chord wings, is extended here to wings comprised of tapered segments. Comparison of the analytical predictions with rotary balance wind tunnel results shows that large discrepancies remain, particularly for those angles-of-attack greater than 40 degrees.

Poppen, W. A., Jr.↗
NASA NTRS1973

Relaxation methods for transonic flow about wing-cylinder combinations and lifting swept wings

The mixed elliptic-hyperbolic relaxation method for obtaining steady-state solutions to two-dimensional transonic potential equations is extended to the transonic small disturbance equation in three dimensions. In particular, transonic flow is considered both about nonlifting wing-cylinder combinations and over thin lifting wings with sweep and taper. The treatment is restricted to freestream Mach numbers less than one and to wings with subsonic trailing edges.

Bailey, F. R.↗
NASA NTRS1976

Preliminary study of effects of winglets on wing flutter

Some experimental flutter results are presented over a Mach number range from about 0.70 to 0.95 for a simple, swept, tapered, flat-plate wing model having a planform representative of subsonic transport airplanes and for the same wing model equipped with two different upper surface winglets. Both winglets had the same planform and area (about 2 percent of the basic-wing area); however, one weighed about 0.3 percent of the basic-wing weight, and the other weighed about 1.8 percent of the wing weight. The addition of the lighter winglet reduced the wing-flutter dynamic pressure by about 3 percent; the heavier winglet reduced the wing-flutter dynamic pressure by about 12 percent. The experimental flutter results are compared at a Mach number of 0.80 with analytical flutter results obtained by using doublet-lattice and lifting-surface (kernel-function) unsteady aerodynamic theories.

Doggett, R. V., Jr.↗