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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

High temperature kinetic study of the reactions H + O2 = OH + O and O + H2 = OH + H in H2/O2 system by shock tube-laser absorption spectroscopy

The reactions: (1) H + O2 = OH + O; and (2) O + H2 = OH + H are the most important elementary reactions in gas phase combustion. They are the main chain-branching reaction in the oxidation of H2 and hydrocarbon fuels. In this study, rate coefficients of the reactions and have been measured over a wide range of composition, pressure, density and temperature behind the reflected shock waves. The experiments were performed using the shock tube - laser absorption spectroscopic technique to monitor OH radicals formed in the shock-heated H2/O2/Ar mixtures. The OH radicals were detected using the P(1)(5) line of (0,0) band of the A(exp 2) Sigma(+) from X(exp 2) Pi transition of OH at 310.023 nm (air). The data were analyzed with the aid of computer modeling. In the experiments great care was exercised to obtain high time resolution, linearity and signal-to-noise. The results are well represented by the Arrhenius expressions. The rate coefficient expression for reaction (1) obtained in this study is k(1) = (7.13 +/- 0.31) x 10(exp 13) exp(-6957+/- 30 K/T) cu cm/mol/s (1050 K less than or equal to T less than or equal to 2500 K) and a consensus expression for k(1) from a critical review of the most recent evaluations of k(1) (including our own) is k(1) = 7.82 x 10(exp 13) exp(-7105 K/T) cu cm/mol/s (960 K less than or equal to T less than or equal to 5300 K). The rate coefficient expression of k(2) is given by k(2) = (1.88 +/- 0.07) x 10(exp 14) exp(-6897 +/- 53 K/T) cu cm/mol/s (1424 K less than or equal to T less than or equal to 2427 K). For k(1), the temperature dependent A-factor and the correlation between the values of k(1) and the inverse reactant densities were not found. In the temperature range of this study, non-Arrhenius expression of k(2) which shows the upward curvature was not supported.

Ryu, Si-Ok↗
NASA NTRSDate not supplied

Some Effects of Tunnel Noise on Cylinder-Induced Mach 6 Transitional Shock Wave Boundary Layer Interactions

Experiments were conducted on a cylinder-induced shock wave boundary layer interaction (SBLI)as its state was brought through transition using a combination of boundary layer trips and Reynolds number sweep. A baseline case with no trips was also examined. The measurements were made in a Mach 6 freestream in the well-characterized Actively Controlled Expansion tunnel, which demonstrated a near tripling in fluctuation levels with unit Reynolds number increase from 3.0 to 3.5 million per meter. Surface oil flow and schlieren images suggested the jump in freestream noise served as the impetus for SBLI transition since the flow separation distance began to decrease as the Reynolds number progressed through those conditions. Likewise, surface mounted Kulite® pressure transducers indicated a rise in surface pressure fluctuations as well as initial growth in the instability responsible for transitioning the boundary layer within the interaction. Finally, heat transfer rates within the tripped SBLI were shown to be affected by the jump in freestream disturbance levels.

Andrew N Leidy↗
DOE OSTI2025

Optimizing ablator thickness for laser shock experiments

In laser shock experiments, a well-defined, flat-top shock wave at the ablator/sample interface is important for accurately probing material response under uniaxial strain compression. However, the relationship between the ablator thickness and the resulting shock wave characteristics is insufficiently understood, limiting the ability to design optimal experiments. To address this need, we conducted a systematic experimental study using a 100 J laser to shock-compress polyimide ablators to peak stresses ranging from 20.4 to 111.6 GPa. Laser interferometry diagnostics measured the transmitted wave profiles at the ablator/sample interface, consistently showing a single jump followed by a constant peak state before the arrival of release waves. Here, by analyzing shock transit time, flat-top duration, and stress, our results establish a framework for selecting ablator thickness to maximize the flat-top duration, improving the precision and reproducibility of laser shock experiments.

design of experiments↗
NASA NTRSDate not supplied

Summary of Shock Wave Turbulent Boundary Layer Interaction Experiments In a Circular Test Section

A series of experiments were performed at Mach 2.5 in a 17 cm diameter circular test section to characterize an impinging/reflected shock wave turbulent boundary layer interaction generated by a cone-cylinder centerbody. The cone-cylinder centerbody generates a conical shock wave that interacts with the naturally occurring boundary layer developing on the test section wall. Three different cone angles were used in the experiment to study unseparated, incipiently separated, and separated interactions. When the cone-cylinder centerbody is positioned on the centerline, a flowfield which is two-dimensional in the mean is generated. Three dimensional interactions were also created by offsetting the cone-cylinder centerbody from the test section centerline. The results are intended to provide benchmark quality datasets for computational fluid dynamics (CFD) validation without the pitfalls inherent in rectangular configurations where corner effects prohibit a truly two-dimensional flow in the mean. The experimental measurements included surface flow visualization, wall static pressure, flowfield Pitot tube pressure, constant-voltage anemometry (CVA) normal hot-wire, and particle image velocimetry (PIV) measurements. The hot-wire measurements were used to calculate mean mass flux and total temperature profiles, mass flux and total temperature turbulence intensities, and the mass flux-total temperature correlation. The PIV measurements provide three-dimensional mean velocity measurements. Agreement between the pressure, hot-wire, and PIV measurements is established in the undisturbed upstream flowfield.

Supersonic↗
NASA NTRSDate not supplied

Summary of Shock Wave Turbulent Boundary Layer Interaction Experiments in a Circular Test Section

A series of experiments were performed at Mach 2.5 in a 17 cm diameter circular test section to characterize an impinging/reflected shock wave turbulent boundary layer interaction generated by a cone-cylinder centerbody. The cone-cylinder centerbody generates a conical shock wave that interacts with the naturally occurring boundary layer developing on the test section wall. Three different cone angles were used in the experiment to study unseparated, incipiently separated, and separated interactions. When the cone-cylinder centerbody is positioned on the centerline, a flowfield which is two-dimensional in the mean is generated. Three dimensional interactions were also created by offsetting the cone-cylinder centerbody from the test section centerline. The results are intended to provide benchmark quality datasets for computational fluid dynamics (CFD) validation without the pitfalls inherent in rectangular configurations where corner effects prohibit a truly two-dimensional flow in the mean. The experimental measurements included surface flow visualization, wall static pressure, flowfield Pitot tube pressure, constant-voltage anemometry (CVA) normal hot-wire, and particle image velocimetry (PIV) measurements. The hot-wire measurements were used to calculate mean mass flux and total temperature profiles, mass flux and total temperature turbulence intensities, and the mass flux-total temperature correlation. The PIV measurements provide three-dimensional mean velocity measurements. Agreement between the pressure, hot-wire, and PIV measurements is established in the undisturbed upstream flowfield.

compressible flow↗
DOE OSTI2024

Sound speed measurements in shock compressed cemented tungsten carbide: Evolution of elastic moduli with damage at pressures to 100 GPa

The motivation of the present study is to gain insights into the evolution of elastic properties of cemented tungsten carbides (WC) shock compressed to 100 GPa. Seven plate impact experiments—two front surface impact and five release wave overtake—are conducted to make simultaneous measurements of Hugoniot states and longitudinal sound speeds in shocked WC with 3.7wt.% cobalt binder. The sound speeds along with estimates for bulk sound speeds, obtained using the Birch–Murnaghan EoS, are analyzed to determine the elastic moduli—longitudinal, bulk, and shear—as a function of Hugoniot stress. The longitudinal and bulk sound speeds at Hugoniot states of interest are found to increase linearly with longitudinal stress. Consistent with the increase in sound speeds, the longitudinal and bulk moduli also increase with Hugoniot stress; however, the increase in longitudinal modulus is modest when compared to predictions of theoretical models that account for pressure and temperature dependence of elastic moduli, but with no damage. The shear moduli remain nearly constant at ~318 GPa over the range of Hugoniot states investigated. These values are, however, much lower than those predicted by the Steinberg–Guinan model with no damage. Poisson’s ratio decreases initially from its ambient value of 0.208 to ~0.199 for Hugoniot stress ≤10 GPa indicating consolidation of the WC microstructure with low initial stress; however, with an increase in Hugoniot stress to ~100 GPa, Poisson’s ratio increases to ~0.317, indicating degradation of shear moduli with increasing stress. The product of density and Grüneisen parameter (ρΓ), after an initial spike, remains nearly constant for volumetric strains ≥0.07. The maximum average temperature rise is estimated to be ~286°C at the highest Hugoniot stress employed in the study.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Plasma wave phenomena observed at interplanetary shocks by the Ulysses URAP experiment

Results of a study of 24 interplanetary shocks observed by the Unified Radio and Plasma Wave Experiment (URAP) on the Ulysses spacecraft are presented. These shocks, observed between approximately 1 and 4 AU, display a variety of wave phenomena similar to those detected in earlier studies of shocks near 1 AU. The correspondence of the observed low frequency magnetic and electric field waves with the parallel index of refraction for whistler waves was investigated. Observed B/E ratios are found to be typically about a factor of 0.7 times the computed index of refraction, supporting the whistler interpretation of these waves, but also implying a prevalent electrostatic wave component which may be due to whistlers propagating at an angle to the interplanetary magnetic field. A statistical correlation of the amplitudes of the various types of waves with shock and solar wind properties is presented.

Lengyel-Frey, D.↗
NASA NTRS1974

Kinetics of nitric oxide formation and decomposition

Experiments on shock wave structure were conducted in the 12 inch shock tube facility, and it is shown that this work was motivated by the need for improved kinetics for the modeling of NO production in space shuttle flow fields. The experiments on shock structure involved simultaneous observations of pressure and temperature on the wall of the shock tube during reflection of normal shock waves in inert gases.

Kruger, C. H.↗
NASA NTRS1991

Convective response of a wall-mounted hot-film sensor in a shock tube

Shock tube experiments were performed in order to determine the response of a single hot-film element of a sensor array to transiently induced flow behind weak normal shock waves. The experiments attempt to isolate the response due only to the change in convective heat transfer at the hot-film surface mounted on the wall of the shock tube. The experiments are described, the results being correlated with transient boundary layer theory and compared with an independent set of experimental results. One of the findings indicates that the change in the air properties (temperature and pressure) precedes the air mass transport, causing an ambiguity in the sensor response to the development of the velocity boundary layer. Also, a transient, local heat transfer coefficient is formulated to be used as a forcing function in an hot-film instrument model and simulation which remains under investigation.

Roberts, A. Sidney, Jr.↗
NASA NTRS1990

Convective response of a wall-mounted hot-film sensor in a shock tube

Shock tube experiments were performed in order to determine the response of a single hot-film element of a sensor array to transiently induced flow behind weak normal shock waves. The experiments attempt to isolate the response due only to the change in convective heat transfer at the hot-film surface mounted on the wall of the shock tube. The experiments are described, the results being correlated with transient boundary layer theory and compared with an independent set of experimental results. One of the findings indicates that the change in the air properties (temperature and pressure) precedes the air mass transport, causing an ambiguity in the sensor response to the development of the velocity boundary layer. Also, a transient, local heat transfer coefficient is formulated to be used as a forcing function in a hot-film instrument model and simulation which remains under investigation.

Roberts, A. S., Jr.↗
DOE OSTI2026

Platform for 100 s Mbar equation of state measurements on the National Ignition Facility

Equation of state (EOS) measurements in the 100 s Mbar range are needed to underwrite models employed in the simulation of high energy density plasmas. To this end, a platform has been developed for fielding on the National Ignition Facility, capable of producing high-quality impedance match EOS data, wherein a planar, high-pressure, steady shock is driven into a sample package, and sample and reference standard shock velocities are measured. This platform, dubbed planar high pressure, or PHP, was fielded with an initial proof-of-concept shot in January 2023. The first PHP shot, aiming to study gold, demonstrated a pressure close to 400 Mbar, two orders of magnitude higher than previously reported gold EOS data.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Jets from shocked metal surfaces with grooves: Missing experiments

Many studies have investigated the mass outflows generated when a planar shock transits an imperfect (“defected”) metal surface, where the defects are symmetric triangular or sinusoidal grooves. Yet a fundamental question remains unanswered: how does the quantity of outflow mass and its maximum velocity vary as a function of the groove cross-sectional aspect ratio? We identify two sets of missing experiments that must be addressed to answer the question. The aspect ratio (groove depth over width) is equivalently represented by θ, the cross-sectional half angle, or by η 0 k, the amplitude multiplied by an effective wavenumber. Low θ (high η 0 k) grooves comprise the first set of missing experiments, which are necessary to determine the validity of theoretical predictions of the nonlinear regime (η 0 k ≥ 1, θ < 57.5°). The second set of missing experiments are those in which the volume of the groove (or equivalently, the axial cross-sectional area) has been held constant as θ or η 0 k are varied. Such experiments are necessary to independently measure the effects of variations in groove volume and groove aspect ratio on the resulting jets.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1985

Shock Compression of Liquid Helium to 56 GPa (560) Kbar

Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

Nellis, W. J.↗
NASA NTRS1984

Shock compression of liquid helium to 56 GPa (560 kbar)

Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation of the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

Nellis, W. J.↗
DOE OSTI2022

Investigating growth to detonation in vapor-deposited hexanitrostilbene and pentaerythritol tetranitrate films using high-throughput methods

In this work, a high-throughput experimental setup was used to characterize initiation threshold and growth to detonation in the explosives hexanitrostilbene (HNS) and pentaerythritol tetranitrate (PETN). The experiment sequentially launched an array of laser-driven flyers to shock samples arranged in a 96-well microplate geometry, with photonic Doppler velocimetry diagnostics to characterize flyer velocity and particle velocity at the explosive–substrate interface. Vapor-deposited films of HNS and PETN were used to provide numerous samples with various thicknesses, enabling characterization of the evolution of growth to detonation. One-dimensional hydrocode simulations were performed with reactions disabled to illustrate where the experimental data deviate from the predicted inert response. Prompt initiation was observed in 144 μm thick HNS films at flyer velocities near 3000 m/s and in 125 μm thick PETN films at flyer velocities near 2400 m/s. This experimental setup enables rapid quantification of the growth of reactions in explosive materials that can reach detonation at sub-millimeter length scales. These data can subsequently be used for parameterizing reactive burn models in hydrocode simulations, as discussed in Paper II [D. E. Kittell, R. Knepper, and A. S. Tappan, J. Appl. Phys. 131, 154902 (2022)].

36 MATERIALS SCIENCE↗