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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Effect of drooped-nose flaps on the experimental force and moment characteristics of an oblique wing

Six-component experimental force and moment data are presented for a low aspect ratio, oblique wing equipped with drooped-nose flaps and mounted on top of a body of revolution. These flaps were investigated on the downstream wing panel with the nose drooped 5 deg, 10 deg, 20 deg, and 30 deg, and on both wing panels with the nose drooped 30 deg. It was to determine if such flaps would make the moment curves more linear by controlling the flow separation on the downstream wing panel at high lift coefficients. The wing was elliptical in planform and had an aspect ratio of 6.0 (based on the unswept wing span). The wing was tested at sweep angles of 45 deg and 50 deg throughout the Mach number range from 0.25 to 0.95. The drooped-nose flaps alone were not effective in making the moment curves more linear; however, a previous study showed that Kruger nose flaps improved the linearity of the moment curves when the Kruger flaps were used on only the downstream wing panel equipped with drooped-nose flaps deflected 5 deg.

Hopkins, E. J.↗
NASA NTRS1977

Aeroelastic stability analysis of the AD-1 manned oblique-wing aircraft

The AD-1 manned flight test program was conducted to evaluate the stability, control and handling characteristics of oblique wing aircraft. The results of the aeroelastic stability analysis are presented for both the wing alone and the wing with ailerons. A comparison was made between the results obtained using the traditional k-method of flutter analysis and the results using the PK or British method of flutter analysis. Studies were performed using the latest version of the NASTRAN computer code as well as the PASS/FLUT program.

Rutkowski, M. J.↗
NASA NTRS1979

The effect of oblique angle of sound incidence, realistic edge conditions, curvature and in-plane panel stresses on the noise reduction characteristics of general aviation type panels

Experiments and a theoretical analysis were conducted to predict the noise reduction of inclined and curved panels. These predictions are compared to the experimental results with reasonable agreement between theory and experiment for panels under an oblique angle of sound incidence. Theoretical as well as experimental results indicate a big increase in noise reduction when a flat test panel is curved. Further curving the panel slightly decreases the noise reduction. Riveted flat panels are shown to give a higher noise reduction in the stiffness-controlled frequency region, while bonded panels are superior in this region when the test panel is curved. Experimentally measured noise reduction characteristics of flat aluminum panels with uniaxial in-plane stresses are presented and discussed. These test results indicate an important improvement in the noise reduction of these panels in the frequency range below the fundamental panel/cavity frequency.

Grosveld, F.↗
NASA NTRS1977

Passage of a weak vortex sheet through an oblique shock

The two-dimensional problem of the passage of a free vortex sheet of weak strength through an oblique shock wave of finite strength is investigated. Conditions are established which define the changes of the strength and shape of the vortex sheet after its passage through the shock wave in terms of the shock strength and the angle between the shock wave and the vortex sheet.

Ting, L.↗
NASA NTRS1978

Lifting-line theory of oblique wings

The study extends Prandtl's lifting-line theory to planar wings involving swept and curved centerlines. Attention is focused on distinct features of such a theory, with special emphasis on an oblique wing in a steady incompressible potential flow. The analysis presented is compared with exact solutions derived from an inverse method and with results from a panel method.

Cheng, H. K.↗
NASA NTRS1979

Lifting-line theory of oblique wings in transonic flows

Three-dimensional corrections to the nonlinear mixed flow admitted by a high-aspect-ratio swept wing of practical interest are analyzed by solving a perturbation problem and matching its solution to that of an outer flow. The latter is identified with a linear solution involving a lifting line, but the centerline of the planform is not required to be straight and unyawed. The existence of a similarity in the three-dimensional flow structure for a certain oblique-wing geometry is demonstrated, along with a solution to the reduced problem in a high-subcritical case.

Cheng, H. K.↗
NASA NTRS1975

Wind tunnel investigation of an oblique wing transport model at mach numbers between 0.6 and 1.4

Models of three practical oblique-wing transport configurations were tested in the NASA Ames 11 foot wind tunnel. The three configurations used a common forward fuselage, wing, and support system but employed different aft fuselage sections simulating alternate propulsion system installations. These included an integrated propulsion system, pylon-mounted nacelles, and clean (no propulsion system) configuration. The tests were conducted over a Mach number range from 0.6 to 1.4 and at sweep angles from 0 to 60 degrees. The nominal unit Reynolds number was 1.83 million per meter and the angle of attack range was -3 to +6 degrees. The models were mounted in the tunnel by means of a lower blade support system. The interference effects of this lower blade and the flow inclination were determined by using an image blade system and testing the configuration in both the upright and inverted positions.

Black, R. L.↗
NASA NTRS1980

Oblique detonation wave ramjet

Two conceptual designs of the oblique detonation wave ramjet are presented. The performance is evaluated for stoichiometric hydrogen-air equivalence ratios of phi = 1/3, 2/3 and 1 for a range of flight Mach numbers from 6 to 10.

Morrison, R. B.↗
NASA NTRS1980

Calculation of oblique-shock-wave laminar-boundary-layer interaction on a flat plate

A finite difference solution to the problem of the interaction between an impinging oblique shock wave and the laminar boundary layer on a flat plate is presented. The boundary layer equations coupled with the Prandtl-Meyer relation for the external flow are used to calculate the flow field. A method for the calculation of the separated flow region is presented and discussed. Comparisons between this theory and the experimental results of other investigators show fairly good agreement. Results are presented for the case of a cooled wall with an oncoming flow at Mach number 2.0 without and with suction. The results show that a small amount of suction greatly reduces the extent of the separated region in the vicinity of the shock impingement location.

Goldberg, U.↗
NASA NTRS1980

The oblique wing-research aircraft

The AD-1 airplane was designed as a low cost, low speed manned research tool to evaluate the flying qualities of the oblique wing concept. The airplane is constructed primarily of foam and fiberglass and incorporates simplicity in terms of the onboard systems. There are no hydraulics, the control system is cable and torque tube, and the electrical systems consist of engine driven generators which power the battery for engine start, cockpit gages, trim motors, and the onboard data system. The propulsion systems consist of two Microturbo TRS-18 engines sea level trust rated at 220 pounds. The airplane weighs approximately 2100 pounds and has a performance potential in the range of 200 knots and an altitude of 15,000 feet.

Andrews, W. H.↗
NASA NTRS1980

Determination of an oblique wing aircraft's aerodynamic characteristics

In this paper, the integration of wind tunnel and flight test procedures are studied for specifying aerodynamic model forms. A procedure is described which employs a stepwise regression method to systematically determine model structures and F-ratio statistics to rank the importance of each aerodynamic coefficient within a given model. Application of this technique and wind tunnel procedures to an oblique-wing aircraft indicate that the aircraft's measured and estimated response are in good agreement at both small and large wing skew angles

Travassos, R. H.↗
NASA NTRS1981

Extension of oblique incidence method to photo-orthotropic-elasticity

With the interpretation of isochromatic and isoclinic fringes in transparent, birefringent, orthotropic composites established, efforts were in progress to determine the individual values of the principal stresses or strains. Several methods utilize the photoelastic results only partially and rely on numerical procedures. Others attempt to obtain the required information based entirely on experimental data. The classical oblique incidence technique as applied to transversely isotropic birefringent composites, is presented. The proposed extension is verified by applying it to the problem of an orthotropic half-plane subjected to an edge-load.

Prabhakaran, R.↗
NASA NTRS1979

Convective instability when the temperature gradient and rotation vector are oblique to gravity. I - Fluids without diffusion

A linear stability analysis of fluid layers under uniform rotation (generally oblique to gravity) which possess both vertical and horizontal temperature gradients is made by considering ideal fluids without diffusion within a Boussinesq approximation. This simplified configuration is used to assess the preferred convective modes as a function of latitude on a planet like Jupiter. The tilted rotation vector introduces a preference for roll-like disturbances with north-south orientations, while the horizontal temperature gradient produces a thermal wind shear which favors convective rolls oriented parallel to the flow in an east-west direction. It is found that the horizontal temperature gradient needed to produce a preference for the axisymmetric or east-west rolls increases with an increasing rotation rate and a decreasing latitude. The parameter values for Jupiter are estimated with the use of a simple radiative convective model, indicating a preference for axisymmetric rolls at nearly all latitudes if the convection zone depth is greater than about 200 km below the one atmosphere pressure level and convective roll characteristics which contribute to an equatorial acceleration.

Hathaway, D. H.↗
NASA NTRS1980

Convective instability when the temperature gradient and rotation vector are oblique to gravity. II - Real fluids with effects of diffusion

The linear stability analysis of Hathaway et al. (1979) is repeated for Boussinesq fluids with viscous and thermal diffusion. The fluid is confined between plane parallel boundaries and the rotation vector is oblique to gravity; this tilted rotation vector introduces a preference for roll-like disturbances whose axes are oriented north-south. The presence of a latitudinal temperature gradient produces a thermal wind shear which favors axisymmetric convective rolls if the gradient exceeds some critical value. The axisymmetric rolls are similar in many respects to the cloud bands on Jupiter provided they extend to a depth of about 15,000 km.

Hathaway, D. H.↗
NASA NTRS1982

Spin-tunnel investigation of a 1/13-scale model of the NASA AD-1 oblique-wing research aircraft

The spin and recovery characteristics of a 1/13-scale model of the NASA AD-1 oblique-wing research aircraft at wing-skew positions of 0, 25, 45, and 60 deg (right wing forward) were investigated. Spins were obtained for all wing-skew positions tested. For the unskewed wing position, two spin modes were possible. One spin mode was very steep and recoveries were obtained within 1 turn or less by rudder reversal. The second spin mode was flat and fast; the angle of attack was about 75 deg and the spin rate was about 145 deg/sec (2.5 seconds per turn). For the skewed wing positions, spins were obtained only in the direction of the forward-skewed wing (right wing forward). No spins were obtained to the left when the wing was skewed with the right wing forward. Recoveries should be attempted by deflecting the rudder to full against the spin, the ailerons to full with the spin, and movement of the wings to 0 deg skew. If the wing is skewed, the recovery may not be effected until the wing skew approaches 0 deg.

White, W. L.↗
NASA NTRS1981

AD-1 oblique wing aircraft program

A NASA program for evaluation of the handling and flying characteristics of the AD-1 oblique wing aircraft is discussed. The vehicle was flown to compare wind tunnel predictions with aerodynamic data, explore the control system requirements, and obtain a preliminary assessment of the aeroelastic effects. The fiberglass sandwich skin aircraft is designed for 8 g positive and 4 g negative loading at 175 knots, while the wing pivot can withstand 25 g loading. Flight monitoring was accomplished with a 41 channel pulse code modulation system for telemetry and by averaging of pilot ratings. Maneuvering tests are outlined, noting that pilot ratings indicated acceptable handling at up to 50 deg sweep. It is concluded that acceptable flying qualities can be achieved with a 60 deg sweep, and that aeroelastic tailoring can be used to satisfy cruise design technology.

Mcmurtry, T. C.↗
NASA NTRS1981

Dissipation due to obliquity-induced tides in a Kelvin-Voigt viscoelastic body

A calculation is conducted regarding the local and total dissipation rate of mechanical energy for an incompressible, Kelvin-Voigt body in a circular orbit with finite obliquity. The considered material is characterized by a shear modulus and a viscosity. Of the two parameters, only the shear modulus is known. An investigation is conducted regarding the variation of the total dissipation rate with viscosity. For small values of the viscosity the Kelvin-Voigt material approximates the behavior of an elastic solid. In this range, results for the earth-moon system are similar to those obtained by Peale and Cassen (1978) using a modified form of the elastic solution. For large values of the viscosity the results are qualitatively different from those in the 'elastic' range, as viscous effects dominate the material response.

Vanarsdale, W. E.↗
NASA NTRS1982

Impingement of an oblique shock wave on a cylinder

This paper presents a numerical simulation of impingement of an oblique shock wave on a cylinder. The study was undertaken to understand the three-dimensional shock wave and boundary-layer interactions occurring on problems such as the impingement of the bow shock wave from the Shuttle nose on an external tank, and store-carriage interference on a supersonic tactical aircraft. A thin-layer approximation of the Navier-Stokes equations is solved by a mixed explicit-implicit scheme for a supersonic Mach 4 flow with an incident shock angle of 25 deg. Both laminar and turbulent flows are investigated. Surface pressures show large extents of upstream influence, except near windward plane. Based on plots of velocity at the first mesh points above the cylinder body, a conjectured limiting-streamline pattern is constructed. Three-dimensional separation is studied, and the role of crossflow is discussed.

Hung, C. M.↗