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At least 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Subsonic wind-tunnel measurements of a slender wing-body configuration employing a vortex flap

A wind tunnel study at Mach 0.4 was conducted for a slender wing-body configuration with a leading edge vortex flap of curved planform that is deflectable about a 74 degree swept hinge line. The basic data consist of a unique combination of longitudinal aerodynamic, surface pressure, and vortex flap hinge-moment measurements on a common model. The longitudinal aerodynamic, pressure and hinge-moment data are presented without analysis in tabular format. Plots of the tabulated pressure data are also given.

Frink, Neal T.↗
NASA NTRS1986

Splitter blades as an aeroelastic detuning mechanism for unstalled supersonic flutter of turbomachine rotors

Splitter plates usable as aeroelastic detuner devices for supersonic flutter in turbomachinery, through the introduction of both aerodynamic and structural detuning to enhance aeroelastic stability, are presently considered by a mathematical model. The model demonstrates that aerodynamic detuning is due to both the alternate circumferential spacing of the full chord airfoils and the variable circumferentially spaced splitters between each pair of full chord airfoils. Structural detuning is based on the lower natural frequencies of the splitters, by comparison with the full chord airfoils. The model's application to two unstable rotors demonstrates enhanced torsion mode flutter stability through the incorporation of splitters, where the critical parameters are chord length and the circumferential and axial locations of the splitters.

Topp, D. A.↗
NASA NTRS1981

The design of a wind tunnel VSTOL fighter model incorporating turbine powered engine simulators

A wind-tunnel model of a supersonic VSTOL fighter aircraft configuration has been developed for use in the evaluation of airframe-propulsion system aerodynamic interactions. The model may be employed with conventional test techniques, where configuration aerodynamics are measured in a flow-through mode and incremental nozzle-airframe interactions are measured in a jet-effects mode, and with the Compact Multimission Aircraft Propulsion Simulator which is capable of the simultaneous simulation of inlet and exhaust nozzle flow fields so as to allow the evaluation of the extent of inlet and nozzle flow field coupling. The basic configuration of the twin-engine model has a geometrically close-coupled canard and wing, and a moderately short nacelle with nonaxisymmetric vectorable exhaust nozzles near the wing trailing edge, and may be converted to a canardless configuration with an extremely short nacelle. Testing is planned to begin in the summer of 1982.

Bailey, R. O.↗
NASA NTRS1972

Effects of wing-pivot location and forewing configuration on the low-speed aerodynamic characteristics of a variable-sweep airplane model

An investigation has been made to determine the effects of the location of the wing pivot and geometry of the forewing on the static longitudinal aerodynamic characteristics at subsonic speeds of a model representing a variable-sweep supersonic fighter airplane. Results indicate that as the wing-pivot location moves aft and outboard, the change in static margin due to wing sweep is reduced. Increasing the forewing area resulted in a forward shift of the aerodynamic center as well as a slight reduction in the aerodynamic-center variation due to wing sweep.

Huffman, J. K.↗
NASA NTRS2003

Low Speed Rot or/Fuselage Interactional Aerodynamics

This report presents work performed under a Cooperative Research Agreement between Virginia Tech and the NASA Langley Research Center. The work involved development of computational techniques for modeling helicopter rotor/airframe aerodynamic interaction. A brief overview of the problem is presented, the modeling techniques are described, and selected example calculations are briefly discussed.

Barnwell, Richard W.↗
NASA NTRS1981

Determination of airplane model structure from flight data by using modified stepwise regression

The linear and stepwise regressions are briefly introduced, then the problem of determining airplane model structure is addressed. The MSR was constructed to force a linear model for the aerodynamic coefficient first, then add significant nonlinear terms and delete nonsignificant terms from the model. In addition to the statistical criteria in the stepwise regression, the prediction sum of squares (PRESS) criterion and the analysis of residuals were examined for the selection of an adequate model. The procedure is used in examples with simulated and real flight data. It is shown that the MSR performs better than the ordinary stepwise regression and that the technique can also be applied to the large amplitude maneuvers.

Klein, V.↗
NASA NTRS1984

Preliminary results of experimental and analytical investigations of the tumbling phenomenon for an advanced configuration

A sustained autorotative pitching motion usually called 'tumbling' has been observed during dynamic model tests of the X-29A configuration. The X-29 is an advanced design incorporating forward-swept wings and canards in a highly relaxed static stability condition. Beginning with a historical review of the tumbling phenomenon, this paper discusses the current experimental results of dynamic model tumbling tests of the X-29 and the initial efforts to establish an aerodynamic and mathematical model for analysis.

Whipple, R. D.↗
NASA NTRS2007

Modeling Tool Advances Rotorcraft Design

Continuum Dynamics Inc. (CDI), founded in 1979, specializes in advanced engineering services, including fluid dynamic modeling and analysis for aeronautics research. The company has completed a number of SBIR research projects with NASA, including early rotorcraft work done through Langley Research Center, but more recently, out of Ames Research Center. NASA Small Business Innovation Research (SBIR) grants on helicopter wake modeling resulted in the Comprehensive Hierarchical Aeromechanics Rotorcraft Model (CHARM), a tool for studying helicopter and tiltrotor unsteady free wake modeling, including distributed and integrated loads, and performance prediction. Application of the software code in a blade redesign program for Carson Helicopters, of Perkasie, Pennsylvania, increased the payload and cruise speeds of its S-61 helicopter. Follow-on development resulted in a $24 million revenue increase for Sikorsky Aircraft Corporation, of Stratford, Connecticut, as part of the company's rotor design efforts. Now under continuous development for more than 25 years, CHARM models the complete aerodynamics and dynamics of rotorcraft in general flight conditions. CHARM has been used to model a broad spectrum of rotorcraft attributes, including performance, blade loading, blade-vortex interaction noise, air flow fields, and hub loads. The highly accurate software is currently in use by all major rotorcraft manufacturers, NASA, the U.S. Army, and the U.S. Navy.

Source record↗
NASA NTRS1975

Aerodynamic damping and oscillatory stability in pitch of a model of a proposed manned lifting entry vehicle at Mach Numbers of 1.80, 2.16, and 2.86

Wind tunnel tests were conducted using a model of a proposed manned lifting entry vehicle to determine the aerodynamic damping and oscillatory stability in pitch. The model was tested at Mach numbers of 1.80, 2.16, and 2.86. Angles of attack varied from minus 2 degrees to plus 30 degrees at zero angle of sideslip using a small-amplitude, forced-oscillation technique. It was determined that, in general, all the configurations have near zero or slightly positive damping in pitch throughout the angle of attack range. The effects of the deflection of flaps on aerodynamic damping are discussed.

Kilgore, R. A.↗
NASA NTRS2014

Static Aeroelastic Analysis with an Inviscid Cartesian Method

An embedded-boundary, Cartesian-mesh flow solver is coupled with a three degree-of-freedom structural model to perform static, aeroelastic analysis of complex aircraft geometries. The approach solves a nonlinear, aerostructural system of equations using a loosely-coupled strategy. An open-source, 3-D discrete-geometry engine is utilized to deform a triangulated surface geometry according to the shape predicted by the structural model under the computed aerodynamic loads. The deformation scheme is capable of modeling large deflections and is applicable to the design of modern, very-flexible transport wings. The coupling interface is modular so that aerodynamic or structural analysis methods can be easily swapped or enhanced. After verifying the structural model with comparisons to Euler beam theory, two applications of the analysis method are presented as validation. The first is a relatively stiff, transport wing model which was a subject of a recent workshop on aeroelasticity. The second is a very flexible model recently tested in a low speed wind tunnel. Both cases show that the aeroelastic analysis method produces results in excellent agreement with experimental data.

Aeroelastic↗
NASA NTRS1978

Estimate of Orbiter static aeroelasticity properties via FLEXSTAB

The theory underlying the use of rigid-model experimental data in FLEXSTAB aeroelasticity calculations is summarized. A description is given of the aerodynamic and structural models used in the calculation of Space Shuttle Orbiter aeroelasticity properties during the re-entry phase. Experience gained with the use of pressure, nonlinear force and moment, and area-ratio correction methods in the Orbiter application is described and typical program output data are included. The inability of the program to correctly estimate differential control surface pressures and to accept external corrections for these terms is shown to be a major limitation in the Orbiter application.

Cavin, R. K., III↗
NASA NTRS1979

A model of transverse fuel injection applied to the computation of supersonic combustor flow

A two-dimensional, nonreacting flow model of the aerodynamic interaction of a transverse hydrogen jet within a supersonic mainstream has been developed. The model assumes profile shapes of mass flux, pressure, flow angle, and hydrogen concentration and produces downstream profiles of the other flow parameters under the constraints of the integrated conservation equations. These profiles are used as starting conditions for an existing finite difference parabolic computer code for the turbulent supersonic combustion of hydrogen. Integrated mixing and flow profile results obtained from the computer code compare favorably with existing data for the supersonic combustion of hydrogen.

Rogers, R. C.↗
NASA NTRS1980

The role of fallback ejecta in the modification of impact craters

The physical processes responsible for the deposition of fragments of target material ejected from the transient cavity of an impact crater within the crater are discussed and quantities of fallback ejecta deposited in impact craters formed on different planetary surfaces are estimated. Consideration is given to the relative importance of in-flight particle collisions and atmospheric particle deceleration, and a model of the aerodynamic deceleration of fallback ejecta is developed. When applied to Meteor Crater in Arizona, the model predicts 5% of the primary ejecta, with an average fragment size of 1.4 cm, to have fallen back into the crater, in agreement with empirical studies of the crater fallback deposit, thus indicating atmospheric deceleration to be the principal mechanism for fallback deposition on earth. The model also predicts the proportion of primary ejecta to be deposited as fallback to increase with excavation cavity diameter on the earth. Model estimates also suggest that more than half of the primary ejecta from large-scale Venusian cavities should be redeposited as fallback, while relatively small amounts of fallback are expected for lunar and Martian craters.

Settle, M.↗
NASA NTRS1981

Impact of high-alpha aerodynamics on dynamic stability parameters of aircraft and missiles

The aerodynamic phenomena associated with high angles of attack and their effects on the dynamic stability characteristics of airplane and missile configurations are examined. Information on dynamic effects is limited. Steady flow phenomena and their effects on the forces and moments are reviewed. The effects of asymmetric vortices and of vortex bursting on the dynamic response of flight vehicles are reviewed with respect to their influence on: (1) nonlinearity of aerodynamic coefficients with attitude, rates, and accelerations; (2) cross coupling between longitudinal and lateral directional models of motion; (3) time dependence and hysteresis effects; (4) configuration dependencey; and (5) mathematical modeling of the aerodynamics.

Malcolm, G. N.↗
NASA NTRS1993

Size distributions and aerodynamic equivalence of metal chondrules and silicate chondrules in Acfer 059

The CR2 chondrite Acfer 059 is unusual in that the original droplet shapes of metal chondrules are well preserved. We determined separate size distributions for metal chondrules and silicate chondrules; the two types are well sorted and have similar size distributions about their respective mean diameters of 0.74 mm and 1.44 mm. These mean values are aerodynamically equivalent for the contrasting densities, as shown by calculated terminal settling velocities in a model solar nebula. Aerodynamic equivalence and similarity of size distributions suggest that metal and silicate fractions experienced the same sorting process before they were accreted onto the parent body. These characteristics, together with depletion of iron in Acfer 059 and essentially all other chondrites relative to primitive CI compositions, strongly suggest that sorting in the solar nebula involved a radial aerodynamic component and that sorting and siderophile depletion in chondrites are closely related.

Skinner, William R.↗