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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Application of shock tubes to transonic airfoil testing at high Reynolds numbers

Performance analysis of a gas-driven shock tube shows that transonic airfoil flows with chord Reynolds numbers of the order of 100 million can be produced, with limitations being imposed by the structural integrity of the facility or the model. A study of flow development over a simple circular arc airfoil at zero angle of attack was carried out in a shock tube at low and intermediate Reynolds numbers to assess the testing technique. Results obtained from schlieren photography and airfoil pressure measurements show that steady transonic flows similar to those produced for the same airfoil in a wind tunnel can be generated within the available testing time in a shock tube with properly contoured test section walls.

Cook, W. J.↗
NASA NTRS1959

Experimental Investigation of Gas-Side Performance of a Compact Finned-Tube Heat Exchanger

Heat-transfer and pressure-drop data were obtained experimentally for the gas side of a liquid-metal to air, compact finned-tube heat exchanger. The heat exchanger was fabricated from 0.185-inch Inconel tubing in an inline array. The fins were made of 310 stainless-steel- clad copper with a total thickness of 0.010 inch, and the fin pitch was 15.3 fins per inch. The liquid used as the heating medium was sodium. The heat-exchanger inlet gas temperature was varied from 5100 to 1260 R by burning JP fuel for airflow rates of 0.4 to 10.5 pounds per second corresponding to an approximate Reynolds number range of 300 to 9000. The sodium inlet temperature was held at 1400 R with the exception of a few runs taken at 1700 and 1960 R. The maximum ratio of surface temperature to air bulk temperature was 1.45. Friction-factor data with heat transfer were best represented by a single line when the density and viscosity of Reynolds number were evaluated at the average film temperature. At the lower Reynolds numbers reported, the friction data with heat transfer plotted slightly above the friction data without heat transfer. The density of the friction factor was calculated at the average bulk temperature. Heat-transfer results of this investigation were correlated by evaluating the physical properties of air (specific heat, viscosity, and thermal conductivity) at the film temperature.

Gedeon, Louis↗
NASA NTRS1983

Clinostat effects on shoot and root of Arabidopsis

In the clinostat environment, Arabidopsis thaliana (L.) Heynh. plants grown in cultures having limited gas exchange with the external atmosphere developed 'above' the agar media a large mass of roots which eventually covered the stem. Cultural conditions were 0.5 rpm, 350 ft.c. from cool white fluorescent lamps, and 25 C. Limited gas exchange culture tubes were covered with Saran Wrap or mylar film, while free gas exchange cultures were plugged with cotton or polyurethane foam. Average shoot-root dry weight ratio of clinostatted, limited gas exchange plants was 3.39 (p less than 0.001) as compared to 10.1 for upright stationary and 10.3 for vertically rotated controls. Average dry weight (48.3 mg) of all clinostatted shoots was greater than those reported by other investigators (15.1 mg). Finally, shoots of the clinostatted plants reported here were almost 2x heavier (p less than 0.01) than the controls (28.7 mg, 26.7 mg), a result contrary to findings of previous investigators, where the clinostatted plants are the lightest (clinostat 15.1 mg, controls 16.5 mg and 17.2 mg).

Hoshizaki, T.↗
NASA NTRS1973

Relaxation of the accelerating-gas boundary layer to the test-gas boundary layer on a flat plate in an expansion tube

An analytic investigation of the relaxation of the accelerating-gas boundary layer to the test-gas boundary layer over a flat plate mounted in an expansion tube has been conducted. In this treatment, nitrogen has been considered as the test gas and helium as the accelerating gas. The problem is analyzed in two conically similar limits: (1) when the time lag between the arrival of the shock and the interface at the leading edge of the plate is very large, and (2) when this time lag is negligible. The transient laminar boundary-layer equations of a perfect binary-gas mixture are taken as the flow governing equations. These coupled equations have been solved numerically by Gauss-Seidel line-relaxation method. The results predict the transient behavior as well as the time required for an all-helium accelerating-gas boundary layer to relax to an all-nitrogen boundary layer.

Gupta, R. N.↗
NASA NTRS1978

The shock tube as a device for testing transonic airfoils at high Reynolds numbers

A performance analysis of gas-driven shock tubes shows that transonic airfoil flows with chord Reynolds numbers in the range of 100 million can be generated behind the primary shock in a large shock tube. A study of flow over simple airfoils has been carried out at low and intermediate Reynolds numbers to assess the testing technique. Results obtained from schlieren photos and airfoil pressure measurements show that steady transonic flows similar to those observed for the airfoils in wind tunnels can be generated within the available testing time in a shock tube with either properly-contoured test section walls or a properly-designed slotted-wall test section. The study indicates that the shock tube is a useful facility for studying two-dimensional high Reynolds number transonic airfoil flows.

Cook, W. J.↗
NASA NTRS1972

CO2 laser cold cathode study

The procedure for evaluating reliable sputter-free cold cathodes for carbon dioxide lasers is discussed. The purpose of the development is to obtain cold cathodes with service life in excess of 10,000 hours. Discharge tubes are used to eliminate the materials which would be unsatisfactory for use as a cold cathode. A description of the facility for producing the discharge tubes is described. The gas monitoring technique for determining discharge tube performance is examined. Discharge characteristics of tubes with various metals for cathode material are presented in chart form.

Hochuli, U.↗
NASA NTRS1986

Microstructures of niobium-germanium alloys processed in inert gas in the 100 meter drop tube

The 100 meter drop tube at NASA's Marshall Space Flight Center has been used for a series of experiments with niobium-germanium alloys. These experiments were conducted with electromagnetic levitation melting in a 200 torr helium environment. Liquid alloys experienced large degrees of undercooling prior to solidification in the drop tube. Several interesting metastable structures were observed. However, the recalescence event prevented extended solid solubility of germanium in the A-15 beta phase. Liquids of eutectic composition were found to undercool in the presence of solid alpha and solid Nb5Ge3.

Bayuzick, R. J.↗
NASA NTRS1992

Structure of sunspot penumbrae - Fallen magnetic flux tubes

A model is presented of a sunspot penumbra involving magnetic flux tubes that have fallen into the photosphere and float there. An upwelling at the inner end of a fallen tube continuously provides additional gas. This gas flows along and lengthens the tube and is observable as the Evershed flow. Fallen flux tubes may appear as bright streaks near the upwelling, but they become dark filaments further out. The model is corroborated by recent optical high-resolution magnetic data regarding the penumbral filaments, by the 12-micron magnetic measurements relevant to the height of the temperature minimum, and by photographs of the umbra/penumbra boundary.

Wentzel, Donat G.↗
NASA NTRS1992

High spatial resolution measurements of ram accelerator gas dynamic phenomena

High spatial resolution experimental tube wall pressure measurements of ram accelerator gas dynamic phenomena are presented. The projectile resembles the centerbody of a ramjet and travels supersonically through a tube filled with a combustible gaseous mixture, with the tube acting as the outer cowling. Pressure data are recorded as the projectile passes by sensors mounted in the tube wall at various locations along the tube. Data obtained by using a special highly instrumented section of tube has allowed the recording of gas dynamic phenomena with a spatial resolution on the order of one tenth the projectile length. High spatial resolution tube wall pressure data from the three regimes of propulsion studied to date (subdetonative, transdetonative, and superdetonative) are presented and reveal the 3D character of the flowfield induced by projectile fins and the canting of the projectile body relative to the tube wall. Also presented for comparison to the experimental data are calculations made with an inviscid, 3D CFD code.

Hinkey, J. B.↗
NASA NTRS1979

Microscopic phenomena and a modern approach to turbulence

The use of an arc driven shock tube as a technique in the study of turbulence and evidence to support a kinetic theory of turbulence are described. Topics covered include: (1) reaction rate distortion in turbulent flow; (2) turbulent bursts in a shock tube; (3) driver gas flow with fluctuations; (4) improving the Mach number capabilities of arc driver shock tubes; and (5) resonant absorption in an argon plasma at thermal equilibrium.

Johnson, J. A., III↗
NASA NTRS1984

Helium ionization detection apparatus

In a gas chromatograph apparatus comprising a gas supply (He carrier gas), a sample injection apparatus, a chromatograph column, a He ion detector, and connecting tubes, a foreign gas (other than He) injection apparatus is installed between the sample injection apparatus and the detector. Mixing of the sample gas and foreign gas takes place readily, the sample gas is always maintained at a stable concentrator range, and accurate measurements are possible, especially at low sample gas concentrations.

Nagai, R.↗
NASA NTRS1974

An experimental investigation of wall boundary layer transition Reynolds numbers in an expansion tube

Experimental measurements of boundary-layer transition in an expansion-tube test-gas flow are presented along with radial distributions of pitot pressure. An integral method for calculating constant Reynolds number lines for an expansion-tube flow is introduced. Comparison of experimental data and constant Reynolds number calculations has shown that for given conditions, wall boundary-layer transition occurs at a constant Reynolds number in an expansion-tube flow. Operating conditions in the expansion tube were chosen so that the effects of test-gas nonequilibrium on boundary-layer transition could be studied.

Weilmuenster, K. J.↗
NASA NTRS1973

Recent developments in shock tube research; Proceedings of the Ninth International Symposium, Stanford University, Stanford, Calif., July 16-19, 1973

Recent advances in shock tube research are described in papers dealing with the design and performance features of new devices as well as applications in aerodynamic, chemical, and physics experiments. Topics considered include a cryogenic shock tube for studying liquid helium fluid mechanics, studies of shock focusing and nonlinear resonance in shock tubes, applications in gas laser studies, very-low and very-high temperature chemical kinetic measurements, shock tube studies of ionization and recombination phenomena, applications in bioacoustic research, shock-tube simulation studies of sonic booms, and plasma research. Individual items are announced in this issue.

Bershader, D.↗