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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Wind-tunnel investigation of aerodynamic load distribution on a variable-wing-sweep fighter airplane with a NASA supercritical airfoil

Wind-tunnel tests have been conducted at Mach numbers of 0.85, 0.88, and 0.90 to determine the aerodynamic load distribution for the 39 deg swept-wing configuration of a variable-wing-sweep fighter airplane with a NASA supercritical airfoil. Chordwise pressure distributions were measured at two wing stations. Also measured were the overall longitudinal aerodynamic force and moment characteristics and the buffet characteristics. The analysis indicates that localized regions of shock-induced flow separation may exist on the rearward portions of the supercritical wing at high subsonic speeds, and caution must be exercised in the prediction of buffet onset when using variations in trailing-edge pressure coefficients at isolated locations.

Hallissy, J. B.↗
NASA NTRS1983

Computer code for off-design performance analysis of radial-inflow turbines with rotor blade sweep

The analysis procedure of an existing computer program was extended to include rotor blade sweep, to model the flow more accurately at the rotor exit, and to provide more detail to the loss model. The modeling changes are described and all analysis equations and procedures are presented. Program input and output are described and are illustrated by an example problem. Results obtained from this program and from a previous program are compared with experimental data.

Meitner, P. L.↗
NASA NTRS1984

Application of near-term technology to a Mach 2.0 variable-sweep-wing, supersonic-cruise executive jet

The impact of variable sweep wing technology with relaxed static stability requirements on a supersonic-cruise executive jet with transatlantic range was assessed. The baseline vehicle utilized modified, current-technology engines and titanium structures produced with superplastic forming and diffusion bonding; this vehicle meets study requirements for both supersonic-cruise and low-speed characteristics. The baseline concept has a ramp weight of 64,500 pounds with a crew of two and eight passengers. Its Mach 2.0 cruise range is nearly 3,500 nautical miles; its Mach 0.9 cruise range is over 5,000 nautical miles. Takeoff, landing, and balanced field length requirements were calculated for a composite variant and are all less than 5,000 feet.

Beissner, F. L., Jr.↗
NASA NTRS1983

Continuing investigation of sweeping Jovian resonances - The 7:3 amd 3:2 resonances with further discussion of the 2:1 resonance

The formation of the solar system from an accretion disk around the protosun can have a significant impact on the celestial mechanics of the early solar system. The solids in the disk settled to the midplane and formed a planetesimal swarm while an early-formed Jupiter was present. The gravity of the disk makes the radial force law become non-Keplerian, causing the commensurability resonances of the early-formed Jupiter to be displaced from where they would otherwise be. An analysis similar to that previously applied to the 2:1, 3:1 and 5:2 resonances is presently undertaken for the 7:3 and 3:2 resonances, and a Kirkwood-like gap is obtained for a sweeping 7:3 resonance. An accumulation of objects is obtained near the 3:2 resonance which, with the ejection of objects on either side of the resonance, would resemble the Hilda group of asteroids. Agreement between the exact commensurability location and the gap center is discussed for the 2:1 resonance.

Torbett, M. V.↗
NASA NTRS1985

Potential flow calculations and preliminary wing design in support of an NLF variable sweep transition flight experiment

NASA Langley and NASA Ames-Dryden have defined a variable-sweep transition-flight experiment utilizing the F-14 aircraft to enhance understanding of the interaction of crossflow and Tollmien-Schlichting instabilities on a laminar-boundary-layer transition. The F-14 wing outer panel will be modified to generate favorable pressure gradients on the upper wing surface over a wide range of flight conditions. Extensive computations have been performed using two-dimensional and three-dimensional transonic analysis codes. Flight-test and computational data are compared and shown to validate the applicability of the three-dimensional codes (WBPPW and TAWFIVE). In addition, results from two preliminary glove designs derived from two different approaches to the design problem are presented. Advantages and disadvantages of each approach are identified, and it is concluded that coupling an analysis code with an automated design procedure yields a powerful code with distinct advantages over a 'cut-and-dry' approach.

Waggoner, E. G.↗
NASA NTRS1985

Computational wing design in support of an NLF variable sweep transition flight experiment

A natural laminar flow outer panel wing glove has been designed for a variable sweep fighter aircraft using state-of-the-art computational techniques. Testing of the design will yield wing pressure and boundary-layer data under actual flight conditions and environment. These data will be used to enhance the understanding of the interaction between crossflow and Tollmien-Schlichting disturbances on boundary-layer transition. The outer wing panel was contoured such that a wide range of favorable pressure gradients could be obtained on the wing upper surface. Extensive computations were performed to support the design effort which relied on two- and three-dimensional transonic design and analysis techniques. A detailed description of the design procedure that evolved during this study is presented. Results on intermediate designs at various stages in the design process demonstrate how the various physical and aerodynamic constraints were integrated into the design. Final results of the glove design analyzed as part of the complete aircraft configuration with a full-potential wing/body analysis code indicate that the aerodynamic design objectives were met.

Waggoner, E. G.↗
NASA NTRS1986

Phase lock acquisition for sampled data PLLs using the sweep technique

Simulation results of the swept-acquisition performance of residual carrier phase-locked loops (PLLs) are reported. The loops investigated are sampled data counterparts of the continuous time type II and III loops currently in use in Deep Space Network receivers. It was found that sweep rates of 0.2 B(sub L)(2) to 0.4 B(sub L)(2) Hz/s can be used, depending on the loop parameters and loop signal-to-noise ratio (SNR), where B(sub L) is the one-sided loop noise bandwidth. Type III loops are shown to be not as reliable as type II loops for acquisition using this technique, especially at low SNRs.

Aguirre, S.↗
NASA NTRS1987

Investigation of the vortex flap concept on a 75-deg sweep delta wing at supersonic speeds

An experimental investigation of the aerodynamic performance of vortex flaps on a 75-deg sweep delta wing has been conducted in the NASA Langley Unitary Plan Wind Tunnel at Mach numbers from 1.7 to 2.8. The sharp leading edge vortex flaps consisted of the outboard 30 percent of the local wing semispan. Flap deflections of 0, 5, 10, and 15 deg were investigated, for both a wing-alone and a wing-body configuration. The flaps were effective in reducing the drag across the lift-coefficient range. Integration of the upper surface pressure distributions showed that the suction pressures induced by the vortex on the flap were responsible for the drag reductions. At some lift conditions, the minimum drag condition permitted hinge line separation or vortex migration inboard of the hinge line. This result is in contrast to subsonic results, where optimum conditions call for no hinge line separation. The magnitude of the drag reduction due to flap deflection generally decreased as Mach number increased. The effect of a cylindrical forebody on the drag reduction due to flap deflection was minimal.

Covell, Peter F.↗
NASA NTRS1988

Control of supersonic intersection flowfields through filleting and sweep

The problem of supersonic flow control using fillets and sweep for a wing/body junction has been investigated numerically using a three-dimensional Navier-Stokes code which employs the MacCormack time-split finite-volume technique. An elliptic grid generation technique with direct control over spacing has been incorporated for constructing the grid at a filleted wing/body junction. The computed results for pressure distribution, particle paths, and limiting streamlines on the flat plate and fin surface for a swept fin show a decrease in the peak pressure on the fin leading edge and in the extent of the separated flow region. Moreover, the results for the filleted juncture clearly show that the flow streamline patterns lose much of their vortical character with proper filleting. It is demonstrated that fillets with a radius of 3.5 times the fin leading edge diameter are required to weaken the usual necklace vortex interaction.

Lakshmanan, B.↗
NASA NTRS1989

Effect of leading edge sweep on shock-shock interference at Mach 8

These Mach 8 experimental results are applicable to the details of a shock-shock interference that may occur on an engine inlet of a hypersonic vehicle from a swept forebody shock interacting with a swept cowl leading edge bow shock or from a swept splitter plate shock interacting with a swept fuel injection strut bow shock. Peak surface pressure and heat transfer rate on the cylinder were about 10 and 30 times the undisturbed flow stagnation point value, respectively, for the 0 deg sweep test. A comparison of the 15 deg and 30 deg swept results with the 0 deg swept results shows that peak pressure was reduced about 13 percent and 44 percent, respectively, and peak heat transfer rate was reduced about 7 percent and 27 percent, respectively.

Glass, Christopher E.↗
NASA NTRS1989

Identification of XV-15 aeroelastic modes using frequency sweeps

The XV-15 tilt-rotor wing has six major aeroelastic modes that are close in frequency. To precisely excite individual modes during flight test, dual flaperon exciters with automatic frequency-sweep controls were installed. The resulting structural data were analyzed in the frequency domain (Fourier-transformed). Modal frequencies and damping were determined by performing curve fits to frequency-response magnitude and phase data. Results are given for the XV-15 with its original metal rotor blades. Frequency and damping values are also compared with predictions by two different programs, CAMRAD and ASAP.

Acree, C. W., Jr.↗
NASA NTRS1987

Variable-Sweep Transition Flight Experiment (VSTFE): Stability code development and clean-up glove data analysis

The primary objective of the Variable Sweep Transition Flight Experiment (VSTFE) was to establish an improved swept wing transition criterion. The development of the Unified Stability System gave a way of quickly examining disturbance growth for a wide variety of laminar boundary layers. The disturbance growth traces shown are too scattered to define a transition criteria to replace the F-111 data band, which has been used successfully to design NLF gloves. Still, a careful review of the clean-up glove data may yield cases for which the transition location is known more accurately. Liquid crystal photographs of the clean-up glove show much spanwise variation in the transition front for some conditions, and this further complicates the analyses. Several high quality cases are needed in which the transition front is well defined and at a relatively constant chordwise station.

Rozendaal, Roger A.↗
NASA NTRS1989

Experimental transonic flutter characteristics of two 72 deg-sweep delta-wing models

Transonic flutter boundaries are presented for two simple, 72 deg. sweep, low-aspect-ratio wing models. One model was an aspect-ratio 0.65 delta wing; the other model was an aspect-ratio 0.54 clipped-delta wing. Flutter boundaries for the delta wing are presented for the Mach number range of 0.56 to 1.22. Flutter boundaries for the clipped-delta wing are presented for the Mach number range of 0.72 to 0.95. Selected vibration characteristics of the models are also presented.

Doggett, Robert V., Jr.↗
NASA NTRS1990

NGC 3312: A victim of ram pressure sweeping

Researchers are undertaking a volume limited survey of the Hydra I cluster in neutral hydrogen using the National Radio Astronomy Observatory's Very Large Array (VLA). The main purpose is to study the effects of a dense environment on the gaseous component of the galaxies. Observational evidence has been accumulating recently that ram pressure sweeping does occur in the centers of clusters, but it is possible that tidal interactions play a role as well. Results of high resolution HI imaging of NGC 3312, the large peculiar spiral near the cluster center are presented. Hydra I (= A1060) is the nearest rich cluster beyond Virgo and, as such, presents a unique opportunity to do a complete survey of a cluster. It is similar to the Virgo cluster in many of its general physical characteristics, such as size, x ray luminosity, velocity dispersion, and galaxy content (high spiral fraction). However, Hydra I appears to be more regular and relaxed. This is evident in the x ray distribution in its central region, which is radially symmetric and centered on the dominant galaxy, NGC 3311, a cD-like elliptical. The observed x ray luminosity implies a central gas density of 4.5 x 10 to the 3rd power cm(-3). Gallagher (1978) argued from optical images of NGC 3312 that this galaxy might be an ideal candidate to directly study effects of the ram pressure process; it might currently be undergoing stripping of its interstellar medium. The researchers' data are consistent with this suggestion, but other origins of the peculiar appearance cannot yet be ruled out.

Mcmahon, P. M.↗
NASA NTRS1991

Linear-sweep voltammetry of a soluble redox couple in a cylindrical electrode

An approach is described for using the linear sweep voltammetry (LSV) technique to study the kinetics of flooded porous electrodes by assuming a porous electrode as a collection of identical noninterconnected cylindrical pores that are filled with electrolyte. This assumption makes possible to study the behavior of this ideal electrode as that of a single pore. Alternatively, for an electrode of a given pore-size distribution, it is possible to predict the performance of different pore sizes and then combine the performance values.

Weidner, John W.↗
NASA NTRS1991

Satellite sweeping of energetic particles at Neptune

The calculation of the absorption rate of charged particles by planetary satellites introduced by Paonessa and Cheng (1987) is generalized to include an arbitrary offset of the dipole center from the planet center, appropriate for Neptune. The absorption rates calculated for particles of fixed L shell, energy, and pitch angle reflect the features of the complicated geometry of the dipole and the moons. This absorption probability is found to be insignificant compared with that of the rings at L shells to which both sets of absorbers map. However, at larger radii the sweeping rate is controlled by the moons, and the corresponding absorption features provide a starting point for understanding the Voyager energetic particle observations.

Paranicas, C. P.↗
NASA NTRS1955

Flight Measurements of Horizontal-Tail Loads on the Bell X-5 Research Airplane at a Sweep Angle of 58.7 Deg

A flight investigation was made at altitudes of 40,000, 25,000 and 15,000 feet to determine the horizontal-tail loads of the Bell X-5 research airplane at a sweep angle of 58.7 deg over the lift range of the airplane for Mach numbers from 0.61 to 1.00. The horizontal-tail loads were found to be nonlinear with lift throughout the lift ranges tested at all Mach numbers except at a Mach number of 1.00. The balancing tail loads reflected the changes which occur in the wing characteristics with increasing angle of attack. The nonlinearities were, in general, more pronounced at the higher angles of attack near the pitch-up where the balancing tail loads indicate that the wing-fuselage combination becomes unstable. No apparent effects of altitude on the balancing tail loads were evident over the comparable lift ranges of these tests at altitudes from 40,000 feet to 15,000 feet. Comparisons of balancing tail loads obtained from flight and windtunnel tests indicated discrepancies in absolute magnitudes, but the general trends of the data agree. Some differences in absolute magnitude may be accounted for by the tail load carried inboard of the strain-gage station and the load induced on the fuselage by the presence of the tail. These loads were not measured in flight.

Reed, Robert D↗