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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1967

Subsonic and Supersonic Flutter Analysis of a Highly Tapered Swept-Wing Planform, Including Effects of Density Variation and Finite Wing Thickness, and Comparison with Experiments

The flutter characteristics of several wings with an aspect-ratio of 4.0, a taper ratio of 0.2, and a quarter-chord sweepback of 45 deg. have been investigated analytically for Mach numbers up to 2.0. The calculations were based on the modified-strip-analysis method, the subsonic-kernel-function method, piston theory, and quasi-steady second-order theory. Results of t h e analysis and comparisons with experiment indicated that: (1) Flutter speeds were accurately predicted by the modified strip analysis, although accuracy at t h e highest Mach numbers required the use of nonlinear aerodynamic theory (which accounts for effects of wing thickness) for the calculation of the aerodynamic parameters. (2) An abrupt increase of flutter-speed coefficient with increasing Mach number, observed experimentally in the transonic range, was also indicated by the modified strip analysis. (3) In the low supersonic range for some densities, a discontinuous variation of flutter frequency with Mach number was indicated by the modified strip analysis. An abrupt change of frequency appeared experimentally in the transonic range. (4) Differences in flutter-speed-coefficient levels obtained from tests at low supersonic Mach numbers in two wind tunnels were also predicted by the modified strip analysis and were shown to be caused primarily by differences in mass ratio. (5) Flutter speeds calculated by the subsonic-kernel-function method were in good agreement with experiment and with the results of the modified strip analysis. (6) Flutter speed obtained from piston theory and from quasi-steady second-order theory were higher than experimental values by at least 38 percent.

Yates, Carson, Jr.↗
NASA NTRS1983

Development of aerodynamic prediction methods for irregular planform wings

A set of empirical methods was developed to predict low-speed lift, drag and pitching-moment variations with angle of attack for a class of low aspect ratio irregular planform wings suitable for application to advanced aerospace vehicles. The data base, an extensive series of wind-tunnel tests accomplished by the Langley Research Center of the National Aeronautics and Space Administration, is summarized. The approaches used to analyze the wind tunnel data, the evaluation of previously existing methods, data correlation efforts, and the development of the selected methods are presented and discussed. A summary of the methods is also presented to document the equations, computational charts and design guides which have been programmed for digital computer solution. Comparisons of predictions and test data are presented which show that the new methods provide a significant improvement in capability for evaluating the landing characteristics of advanced aerospace vehicles during the preliminary design phase of the configuration development cycle.

Benepe, D. B., Sr.↗
NASA NTRS1985

Supersonic aerodynamic characteristics of canard, tailless, and aft-tail configurations for 2 wing planforms

Aerodynamic characteristics of canard, tailless, and aft tail configurations were compared in tests on a general research model (generic fuselage without canopy, inlets, or vertical tails) at Mach 1.60 and 2.00 in the Langley Unitary Plan Wind Tunnel. Two uncambered wing planforms (trapezoidal with 44 deg leading edge sweep and delta with 60 deg leading edge sweep) were tested for each configuration. The relative merits of the configurations were also determined theoretically, to evaluate the capabilities of a linear theory code for such analyses. The canard and aft tail configurations have similar measured values for lift curve slope, maximum lift drag ratio, and zero lift drag. The stability decrease as Mach number increases is greatest for the tailless configuration and least for the canard configuration. Because of very limited accuracy in predicting the aerodynamic parameter increments between configurations, the linear theory code is not adequate for determining the relative merits of canard, tailless, and aft tail configurations.

Covell, P. F.↗
NASA NTRS1991

Crescent Wing Planforms Reduce Lift-Dependent Drag

New understanding of optimization of design of wing to minimize induced drag developed by use of computational methods that account properly for nonlinear effects of deflected wake, nonplanar shape of wing, and vortex rollup. Crescent planforms are lunate shapes like some found in nature, similar to certain bird wings and fish fins. Theoretical and experimental analyses reveals superior aerodynamic efficiency and improved high-angle-of-attack characteristics.

Holmes, Bruce J.↗
NASA NTRS1986

Visualization and flow surveys of the leading edge vortex structure on delta wing planforms

In the present experimental investigation of thin delta wing vortex breakdown, for the cases of sweep angles of 70, 75, 80, and 85 deg, and smoke flow visualization/laser light sheet technique is used to obtain cross sectional views of the leading edge vortices as they break down. A combination of lateral and longitudinal cross sectional views furnishes data on the three-dimensional character of the vortex before, during, and after breakdown. Velocity measurements conducted with a laser Doppler anemometer on the 70 deg sweep delta, at 30 deg angle-of-attack, indicate that when breakdown occurs the core flow is transformed from a jet-like to a wake-like flow.

Payne, F. M.↗
NASA NTRS1974

Comparisons of two-dimensional shock-expansion theory with experimental aerodynamic data for delta-planform wings at high supersonic speeds

An investigation has been conducted to explore the potential for optimizing airfoil shape at high supersonic speeds by utilizing the two-dimensional shock-expansion method. Theoretical and experimental force and moment coefficients are compared for four delta-planform semispan wings having a leading-edge sweep angle of 65 deg and incorporating modified diamond airfoils with a thickness-chord ratio of 0.06. The wings differ only in airfoil maximum-thickness position and camber. The experimental data are obtained at Mach numbers of 3.95 and 4.63 and at a Reynolds number of 9.84 million per meter. A relatively simple method is developed for predicting, in terms of lift-drag ratio, the optimum modified diamond airfoil at high supersonic and hypersonic speeds.

Jernell, L. S.↗
NASA NTRS1988

An aerodynamic comparison of planar and non-planar outboard wing planforms

An investigation of seven different configurations for two different spans confirms that an experimentally derived span efficiency of greater than one is possible for a nonplanar wing. It is suggested that the induced drag benefits of wings with nonplanar outboard planforms relate to the movement of vorticity away from the center of the span line. Both the position of the vortex and its effect on the wing's downwash distribution are found to significantly effect nonplanar wing performance.

Naik, D. A.↗
NASA NTRS1976

Wing planforms for high-speed flight

The analysis indicates that for aerodynamic efficiency, wings designed for flight at supersonic speeds should be swept back at an angle greater than the Mach angle and the angle of sweepback should be such that the component of velocity normal to the leading edge is less than the critical speed of the airfoil sections. This principle may also be applied to wings designed for subsonic speeds near the speed of sound, for which the induced velocities resulting from the thickness might otherwise be sufficiently great to cause shock waves.

Jones, R. T.↗
NASA NTRS1973

Supersonic aerodynamic characteristics associated with variations in the geometry of the forward portion of irregular planform wings

The experimental longitudinal and lateral-directional stability characteristics of a Langley conceptual space shuttle orbiter design have been obtained for a series of inboard planform fillets in a unitary plan wind tunnel. Fillet sweep angles up to 78 deg were investigated while holding the spanwise intersection of the fillet and wing constant. The data were obtained at Mach numbers of 2.36 to 4.63 and at Reynolds numbers (depending on Mach number) of 1.5 million to 2.5 million per foot. The angle of attack was varied from about minus 2 deg to 44 deg at 0 deg and 3 deg of sideslip.

Spencer, B., Jr.↗
NASA NTRS1973

Subsonic and transonic aerodynamic characteristics associated with variations in the geometry of the forward portion of irregular planform wings on a .01875 scale LO-100 Langley concept space shuttle orbiter in the Langley 8 foot TPT (LA7B)

The experimental longitudinal-and lateral-directional stability characteristics of a Langley conceptual space shuttle orbiter design were obtained for a series of inboard planform fillets in the NASA/LaRC 8-foot transonic pressure tunnel. Fillet sweep angles up to 78 deg were investigated while holding the spanwise intersection of the fillet and wing constant. The data were obtained at Mach numbers of 0.35 to 1.2 and at Reynolds numbers (depending on Mach number) of 1,000,000 to 3,200,000 per foot. The angle of attack was varied from about -2 deg to 22 deg at sideslip.

Vaughn, J. E.↗
NASA NTRS1987

An experimental study of the aerodynamic characteristics of planar and non-planar outboard wing planforms

A series of wind tunnel experiments have been conducted to investigate the aerodynamic characteristics of several planar and nonplanar wingtip planforms. Seven different configurations: base-line rectangular, elliptical, swept and tapered, swept and tapered with dihedral, swept and tapered with anhedral, rising arc, and drooping arc, were investigated for two different spans. The data are available in terms of coefficient plots of force data, flow visualization photographs, and velocity and pressure flowfield surveys. All planforms, particularly the nonplanar, have some advantages over the baseline rectangular planform. Span efficiencies up to 20-percent greater than baseline are a possibility. However, it is suggested that the span efficiency concept might need refinement for nonplanar wings. Flow survey data show the change in effective span with vortex roll-up. The flow visualization shows the occurrence of mushroom-cell-separation flow patterns at angles of attack corresponding to stall. These grow with an increase in post-stall angle of attack. For the larger aspect ratios, the cells are observed to split into sub-cells at the higher angles of attack. For all angles of attack, some amount of secondary vortex flow is observed for the planar and nonplanar out-board planforms with sweep and taper.

Naik, D. A.↗
NASA NTRS1991

Conical Euler simulation of wing rock for a delta wing planform

Unsteady, vortex-dominated flowfields are presently studied by using the conical Euler equations as an efficient first step toward investigation of the full three-dimensional problem, under the assumption that the supersonic flow about a delta wing is conical and therefore allows the three-dimensional problem to be reduced to a two-dimensional one. Attention is given to the case of a delta wing undergoing wing-rock motion. The code developed has also been modified to allow treatment of the 'free-to-roll' case.

Lee, Elizabeth M.↗
NASA NTRS1999

Testing the 2.2% HSR Reference H Model with a Modified Wing Planform in the NTF

The HSR program moved into phase two with the selection of a new airplane configuration, the Technology Concept Airplane (TCA). The TCA was designed based on the experiences gained while investigating both the Reference H and the Arrow Wing configurations in different wind tunnels and CFD studies. Part of that investigation included performing extensive high Reynolds number testing on the Reference H configuration in the NTF to provide data for predicting full-scale flight performance, as well as developing techniques for testing these types of configurations in the NTF. With the selection of the TCA configuration, a smaller investigation was designed to examine whether or not the scaling characteristics of the TCA configuration are similar to those observed for the Reference H configuration. This presentation will include a description of the 2.2% Modified Reference H model used in this investigation (highlighting the similarities and the differences when compared to the TCA configuration), the testing objectives, and some preliminary findings that are relevant to the current high-lift system.

Owens, Lewis R., Jr.↗
NASA NTRS1990

Static Wind-Tunnel and Radio-Controlled Flight Test Investigation of a Remotely Piloted Vehicle Having a Delta Wing Planform

At the request of the United States Marine Corps, an exploratory wind-tunnel and flight test investigation was conducted by the Flight Dynamics Branch at the NASA Langley Research Center to improve the stability, controllability, and general flight characteristics of the Marine Corps Exdrone RPV (Remotely Piloted Vehicle) configuration. Static wind tunnel tests were conducted in the Langley 12 foot Low Speed Wind Tunnel to identify and improve the stability and control characteristics of the vehicle. The wind tunnel test resulted in several configuration modifications which included increased elevator size, increased vertical tail size and tail moment arm, increased rudder size and aileron size, the addition of vertical wing tip fins, and the addition of leading-edge droops on the outboard wing panel to improve stall departure resistance. Flight tests of the modified configuration were conducted at the NASA Plum Tree Test Site to provide a qualitative evaluation of the flight characteristics of the modified configuration.

Yip, Long P.↗