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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Prediction of sonic boom from experimental near-field overpressure data. Volume 1: Method and results

A computerized procedure for predicting sonic boom from experimental near-field overpressure data has been developed. The procedure extrapolates near-field pressure signatures for a specified flight condition to the ground by the Thomas method. Near-field pressure signatures are interpolated from a data base of experimental pressure signatures. The program is an independently operated ODIN (Optimal Design Integration) program which obtains flight path information from other ODIN programs or from input.

Glatt, C. R.↗
NASA NTRS1974

Theoretical and experimental study on the ejector augmented jet flap

The analytical concept used in determining the characteristics of jet flap or related propulsive systems suitable for VTOL and STOL applications was examined. The configuration chosen was a two dimensional wing with a biplane flap, having a jet injected on the upper surface of the wing at the flap hinge axis and discharging into the channel between the two elements of the flap. The experimental work was conducted in a two dimensional test installation in a subsonic wind tunnel. The model description, the test conditions, and a summary of the experimental results are presented.

Stewart, H. J.↗
NASA NTRS1975

Analytic and experimental evaluation of flowing air test conditions for selected metallics in a shuttle TPS application

A detailed experimental and analytical evaluation was performed to define the response of TD nickel chromium alloy (20 percent chromium) and coated columbium (R512E on CB-752 and VH-109 on WC129Y) to shuttle orbiter reentry heating. Flight conditions important to the response of these thermal protection system (TPS) materials were calculated, and test conditions appropriate to simulation of these flight conditions in flowing air ground test facilities were defined. The response characteristics of these metallics were then evaluated for the flight and representative ground test conditions by analytical techniques employing appropriate thermochemical and thermal response computer codes and by experimental techniques employing an arc heater flowing air test facility and flat face stagnation point and wedge test models. These results were analyzed to define the ground test requirements to obtain valid TPS response characteristics for application to flight. For both material types in the range of conditions appropriate to the shuttle application, the surface thermochemical response resulted in a small rate of change of mass and a negligible energy contribution. The thermal response in terms of surface temperature was controlled by the net heat flux to the surface; this net flux was influenced significantly by the surface catalycity and surface emissivity. The surface catalycity must be accounted for in defining simulation test conditions so that proper heat flux levels to, and therefore surface temperatures of, the test samples are achieved.

Schaefer, J. W.↗
NASA NTRS1974

Planetary entry aerothermodynamics. I - Technology requirements and experimental facilities

Consideration has been given to the entry of vehicles into the atmospheres of all planets with the exception of Pluto and to missions for returning samples to Earth from all the planets (excepting Pluto), the satellites of Mars, Jupiter, and Saturn, the Moon, the asteroids, and certain comets. The efficient planning of the space missions including the appropriate design of the spacecraft requires that operational and environmental parameter values for the large range of mission options included be adequately known. The need to obtain the data required as a basis for the computational studies involved makes it necessary to conduct a comprehensive experimental research program. Details concerning the experimental facilities employed in this program are discussed, giving attention to shock tubes, the planetary-entry radiation facility, ballistic ranges, an expansion tube, a hypersonic tetrafluoromethane tunnel, and arcjet facilities.

Olstad, W. B.↗
NASA NTRS1974

Experimental and analytical sonic nozzle discharge coefficients for Reynolds numbers up to 8,000,000

Sonic discharge coefficients are presented for two different geometry flow nozzles using nitrogen gas at high pressures where real-gas corrections are significant. Throat Reynolds number range extended up to 8,000,000. Experimentally obtained coefficients for a nozzle with a continuous and finite radius of curvature agreed with those obtained analytically to within 0.2 per cent. Experimental coefficients for a long-radius ASME nozzle agreed to within 0.25 per cent to an empirical equation representing the most probable subsonic discharge coefficient.

Szaniszlo, A. J.↗
NASA NTRS1974

Theoretical and experimental comparisons of the nonlinear energy method to the J-integral, R-curve and COD methods in fracture toughness testing

Because of the current high degree of interest in the development of a standard nonlinear test method, analytical and experimental comparisons have been made between the R-curve, COD, J-integral and nonlinear energy methods. A general definition of fracture toughness is proposed and the fundamental definitions of each method are compared to it. Experimental comparisons between the COD, J-integral, nonlinear energy and standard ASTM methods have been made for a series of compact tension tests on several aluminum alloys. Some of the tests were conducted according to the ASTM standard method E399-72, while the specimen thickness was reduced below the minimum requirement for plane strain fracture toughness testing for several other test series. The fracture toughness values obtained by the COD method were significantly higher than the toughness values obtained by the other three methods. All of the methods displayed a tendency to yield higher toughness values as the thickness was decreased below the ASTM plane strain requirement.

Liebowitz, H.↗
NASA NTRS1975

Experimental characterization of composites

The experimental characterization for composite materials is generally more complicated than for ordinary homogeneous, isotropic materials because composites behave in a much more complex fashion, due to macroscopic anisotropic effects and lamination effects. Problems concerning the static uniaxial tension test for composite materials are considered along with approaches for conducting static uniaxial compression tests and static uniaxial bending tests. Studies of static shear properties are discussed, taking into account in-plane shear, twisting shear, and thickness shear. Attention is given to static multiaxial loading, systematized experimental programs for the complete characterization of static properties, and dynamic properties.

Bert, C. W.↗
NASA NTRS1975

Experimental studies of flow separation and stalling on two-dimensional airfoils at low speeds. Phase 2: Studies with Fowler flap extended

Results were given on experimental studies of flow separation and stalling on a two-dimensional GA(W)-1 17 percent thick airfoil with an extended Fowler flap. Experimental velocity profiles obtained from a five tube probe survey with optimum flap gap and overlap setting (flap at 40 deg) are shown at various stations above, below, and behind the airfoil/flap combination for various angles of attack. The typical zones of steady flow, intermittent turbulence, and large scale turbulence were obtained from a hot wire anemometer survey and are depicted graphically for an angle of attack of 12.5 deg. Local skin friction distributions were obtained and are given for various angles of attack. Computer plots of the boundary layer profiles are shown for the case of the flap at 40 deg. Static pressure contours are also given. A GA(W)-2 section model was fabricated with 30 percent Fowler flaps and with pressure tabs.

Seetharam, H. C.↗
NASA NTRS1975

A generalized correlation of experimental flat-plate collector performance

A generalized collector performance correlation was derived and shown by experimental verification to be of the proper form to account for the majority of the variable conditions encountered both in outdoor and in indoor collector tests. This correlation permits a determination of collector parameters which are essentially nonvarying under conditions which do vary randomly (outdoors) or conditions which vary in a controlled manner (indoors - simulator). It was shown that correlation of the experimental performance of collectors allows the following: (1) comparisons of different collector designs; (2) collector performance prediction under conditions that differ from the conditions of the test program; and (3) monitoring performance degradation effects.

Simon, F. F.↗
NASA NTRS1976

Analytical and experimental studies of an optimum multisegment phased liner noise suppression concept

Results are presented from detailed analytical studies made to define methods for obtaining improved multisegment lining performance by taking advantage of relative placement of each lining segment. Properly phased liner segments reflect and spatially redistribute the incident acoustic energy and thus provide additional attenuation. A mathematical model was developed for rectangular ducts with uniform mean flow. Segmented acoustic fields were represented by duct eigenfunction expansions, and mode-matching was used to ensure continuity of the total field. Parametric studies were performed to identify attenuation mechanisms and define preliminary liner configurations. An optimization procedure was used to determine optimum liner impedance values for a given total lining length, Mach number, and incident modal distribution. Optimal segmented liners are presented and it is shown that, provided the sound source is well-defined and flow environment is known, conventional infinite duct optimum attenuation rates can be improved. To confirm these results, an experimental program was conducted in a laboratory test facility. The measured data are presented in the form of analytical-experimental correlations. Excellent agreement between theory and experiment verifies and substantiates the analytical prediction techniques. The results indicate that phased liners may be of immediate benefit in the development of improved aircraft exhaust duct noise suppressors.

Sawdy, D. T.↗
NASA NTRS1976

An experimental investigation of supersonic flow past a wedge-cylinder configuration

An experimental investigation of supersonic flow past double-wedge configurations was conducted. Over the range of geometries tested, it was found that, while theoretical solutions both for a Type V pattern and for a Type VI pattern could be generated for a particular flow condition (as defined by the geometry and the free-stream conditions), the weaker, Type VI pattern was observed experimentally. More rigorous flow-field solutions were developed for the flow along the wing leading-edge. Solutions were developed for the three-dimensional flow in the plane of symmetry of a swept cylinder (which represented the wing leading-edge) which was mounted on a wedge (which generated the "bow" shock wave). A numerical code was developed using integral techniques to calculate the flow in the shock layer upstream of the interaction region (i.e., near the wing root). Heat transfer rates were calculated for various free stream conditions. The present investigation was undertaken to examine the effects of crossflow on the resultant flow-field and to verify the flow model used in theoretical calculations.

Barnette, D. W.↗
NASA NTRS1976

Experimental study of transient dynamics of a flexible rotor

The results of an experimental program to investigate the transient response of a flexible rotor are presented. The program consisted of a series of tests conducted on a rig with a rotor designed to operate above its first bending critical speed. The purpose of the tests was to obtain experimental data on the transient behavior of a flexible rotor under conditions simulating those which might occur in a jet aircraft engine. The scope of the program included tests to measure the response of both balanced and unbalanced rotors during steady-state operation, acceleration, deceleration, and simulated blade loss.

Hibner, D. H.↗
NASA NTRS1976

An experimental and computational investigation of the flow field about a transonic airfoil in supercritical flow with turbulent boundary-layer separation

A combined experimental and computational research program is described for testing and guiding turbulence modeling within regions of separation induced by shock waves incident in turbulent boundary layers. Specifically, studies are made of the separated flow the rear portion of an 18%-thick circular-arc airfoil at zero angle of attack in high Reynolds number supercritical flow. The measurements include distributions of surface static pressure and local skin friction. The instruments employed include highfrequency response pressure cells and a large array of surface hot-wire skin-friction gages. Computations at the experimental flow conditions are made using time-dependent solutions of ensemble-averaged Navier-Stokes equations, plus additional equations for the turbulence modeling.

Rubesin, M. W.↗
NASA NTRS1976

Experimental development of processes to produce homogenized alloys of immiscible metals, phase 3

An experimental drop tower package was designed and built for use in a drop tower. This effort consisted of a thermal analysis, container/heater fabrication, and assembly of an expulsion device for rapid quenching of heated specimens during low gravity conditions. Six gallium bismuth specimens with compositions in the immiscibility region (50 a/o of each element) were processed in the experimental package: four during low gravity conditions and two under a one gravity environment. One of the one gravity processed specimens did not have telemetry data and was subsequently deleted for analysis since the processing conditions were not known. Metallurgical, Hall effect, resistivity, and superconductivity examinations were performed on the five specimens. Examination of the specimens showed that the gallium was dispersed in the bismuth. The low gravity processed specimens showed a relatively uniform distribution of gallium, with particle sizes of 1 micrometer or less, in contrast to the one gravity control specimen. Comparison of the cooling rates of the dropped specimens versus microstructure indicated that low cooling rates are more desirable.

Reger, J. L.↗
NASA NTRS1976

Use of dynamic theory to describe experimental results from volume holography

The general applicability of dynamic theory to the description of the recording and readout characteristics of volume (thick) hologram gratings is indicated. In dynamic theory (as opposed to static theory), the volume nature of the thick holographic grating allows the interference of an incident light beam with its own diffracted beam inside the recording medium. This effect causes the continuous recording of another grating that alters the initial one, producing a resultant grating that is not uniform through the thickness of the recording material and a grating whose writing and reading characteristics may vary dramatically, depending on the recording material and the experimental conditions. A large number of diverse types of writing, reading, and angular-selectivity behavior have been reported. The dynamic theory of thick-hologram writing and reading is shown to predict qualitatively all of these various types of experimental behavior.

Magnusson, R.↗
NASA NTRS1975

Analysis and experimental measurement of straylight suppression systems for the large space telescope

A computer program for straylight suppression system design and analysis was developed to analyze various proposed LST straylight suppression systems. Simultaneously, experimental measurements are being made on a simplified LST straylight suppression system in a unique facility. The experimental measurements are being used to verify and improve the computer program. The facility represents the state-of-the-art in straylight suppression measurements, and transmission factors of 10 to the minus 12th power have been measured.

Wyman, C. L.↗
NASA NTRS1976

Experimental-analytical correlation of optimum duct acoustic liner performance

Mode matching and segmented duct analytical models have been developed to take advantage of relative placement of liner segments in the design of optimal duct acoustic liners of one, two, and three segments. This paper presents experimental results which were obtained for liners installed in a rectangular duct for the case with no mean airflow through the duct. Excellent correlation is shown between the analytical and experimental data, thus verifying the analytical procedures used to design the optimum segmented lining configurations.

Patterson, J. D.↗
NASA NTRS1976

An experimental and computational investigation of the flow field about a transonic airfoil in supercritical flow with turbulent boundary-layer separation

A combined experimental and computational research program for testing and guiding turbulence modeling within regions of separation induced by shock waves incident on turbulent boundary layers is described. Specifically, studies are made of the separated flow over the rear portion of an 18%-thick circular-arc airfoil at zero angle of attack in high Reynolds number supercritical flow. The measurements include distributions of surface static pressure and local skin friction. The instruments employed include high-frequency response pressure cells and a large array of surface hot-wire skin-friction gages. Computations at the experimental flow conditions are made using time-dependent solutions of ensemble-averaged Navier-Stokes equations, plus additional equations for the turbulence modeling.

Rubesin, M. W.↗