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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Pressure waves generated by steady flames.

Analysis of pressure waves that can be generated by clouds of explosive gas mixtures in a free atmosphere which is initially at a uniform state. The treatment is restricted only to the final stage of constant flame velocity when the flowfield is self-similar. By the introduction of reduced blast-wave parameters as phase-plane coordinates, the problem is resolved into the determination of the appropriate integral curves on this plane. Results, including space profiles of gasdynamic parameters, have been computed for a specific case of a hydrocarbon-air mixture characterized by a specific heat ratio of 1.3, sound speed at NTP of 345 m/sec, and volumetric expansion ratio corresponding to constant pressure deflagration of 7. Maximum overpressure ratios that can be generated by such flames in point-and line-symmetrical waves range from .00053, for the lower bound in the burning speed, up to 6 for the deflagration, while, for the average speeds of 5 to 10 m/sec, they are at a level of 0.05 to 0.10.

Kuhl, A. L.↗
NASA NTRS1993

ULF waves in the Io torus: Ulysses observations

Throughout the Io torus, Ulysses has observed intense ultralow frequency (ULF) wave activity in both electric and magnetic components. Such ULF waves have been previously suggested as the source of ion precipitation leading to Jovian aurorae. The peaks of the wave spectra are closely related to the ion cyclotron frequencies, which is evidence of the waves being ion cyclotron waves (ICWs). Analysis of the dispersion relation using a multicomponent density model shows that at high latitudes (approximately 30 deg), peak frequencies of the waves fall into L mode branches of guided or unguided ICWs. Near the equator, in addition to the ICWs below f(sub cO(2+)), there are strong signals at approximately 10 Hz which require an unexpectedly large energetic ion temperature anistropy to be explained by the excitation of either convective or nonconvective ion cyclotron instabilities. Their generation mechanism remains open for the future study. Evaluation of the Poynting vector and the dispersion relation analysis suggest that the waves near the equator had a small wave angle relative to the magnetic field, while those observed at high latitudes were more oblique. The polarization of the waves below f(sub cH(+)) is more random than that of the whistler mode waves, but left-hand-polarized components of the waves can still be seen. The intensity of the ICWs both near the equator and at high latitudes are strong enough to meet the requirement for producing strong pitch angle scattering of energetic ions.

Lin, Naiguo↗
NASA NTRS1976

Wave propagation in laminated orthotropic circular cylindrical shells

An exact three-dimensional analysis of wave propagation in laminated orthotropic circular cylindrical-shells is developed. Numerical results are presented for three-ply shells, and for various axial wave lengths, circumferential wave numbers, and thicknesses. Results from a thin shell theory and a refined approximate theory are compared with the exact results.

Srinivas, S.↗
NASA NTRS2002

IMAGE-EUV Observation of Large Scale Standing Wave Pattern in the Nightside Plasmasphere

We present analyses of a nightside plasmaspheric pattern of bifurcated, filamentary He(+) 30.4-nm emission enhancements observed by IMAGE EUV between approximately 19:40-22:13 UT on 28 June 2000 that indicate the presence of a large-scale, global ULF standing wave pattern. Analysis of coincident IMAGE magnetometer chain data reveals that these ULF waves extend across the magnetic latitude-longitude range of the chain and possess multiple spectral features between 0.6-5-mHz (3-30 minute period). Additionally, analysis of ACE SWE data reveals similarly structured spectral components in the solar wind. Collectively, these analyses lead to the conclusion that the observed large-scale ULF wave pattern is the result of solar wind pressure pulses 'ringing' the inner-magnetosphere.

Six, N. Frank↗
NASA NTRS1993

Mountain-wave drag in the stratosphere and mesosphere inferred from observed winds and a simple mountain-wave parameterization scheme

A daily analysis of mountain-wave propagation through observed, global wind, and temperature fields in January and August is presented. Winds and temperatures are obtained from the daily 18-level NMC Climate Analysis Center. Mountain-wave properties are deduced from a simple, gravity wave parameterization scheme in which the effects of topographic anisotropy (ridge orientation) are explicitly included. Planetary waves in the northern winter stratosphere are found to play an important role in modulating the magnitude and distribution of inferred mountain-wave drag in the middle atmosphere. The Aleutian anticyclone is found to effectively block mountain waves generated over western North America from reaching the mesosphere by inducing local mountain-wave-critical levels in the stratosphere. Stratospheric sudden warmings have a similar effect at all longitudes so that during months with sudden warmings the average inferred drag in the mesosphere is reduced by a factor of 4 to 5 from its normal value. Partly as a consequence of larger planetary-wave filtering in the Northern Hemisphere, inferred mountain-wave drag in the southern winter mesosphere is found to be comparable to that in the northern winter mesosphere. Almost all of the mountain wave drag exerted on the southern middle atmosphere is found to originate over the southern Andes and Antarctic Peninsula.

Bacmeister, Julio T.↗
NASA NTRS1989

Traveling-wave induction launchers

An analysis of traveling-wave induction launchers shows that induction is a feasible method of producing armature current and that efficient accelerators can be built without sliding contacts or arcs. In a traveling-wave induction launcher the armature current is induced by a slip speed between the armature and a traveling magnetic field. At 9 m/s slip speed a 9 kg projectile with an aluminum armature weighing 25 percent of the total mass can be accelerated to 3000 m/s in a 5 m-long barrel with a total ohmic loss in the barrel coils and armature of 4 percent of the launch kinetic energy and with an average armature temperature rise of 220 deg C, but a peak excitation frequency of 8600 Hz is required. With a 2 kg launch mass the ohmic loss is 7 percent. A launcher system optimized for rotating generators would have a peak frequency of 4850 Hz; with an aluminum armature weighing 33 percent of the launch mass and a slip speed of 30 m/s the total ohmic loss in the generators, cables, and accelerator would be 43 percent of the launch kinetic energy, and the average armature temperature rise would be 510 deg C.

Elliott, David G.↗
NASA NTRS1983

Turbulence analysis of the Jovian upstream 'wave' phenomenon

As Voyager 2 approached Jupiter's bow shock, large-amplitude fluctuations were seen in both the magnetic field and plasma fluid velocity. These fluctuations generally coincided with the occurrence of long-lived energetic particle events similar to the upstream waves often observed near the earth's bow shock. In this paper an analysis of the magnetic field and plasma observations using spectral methods is presented. The characteristic spectral features related to the upstream waves are generally seen near 1 mHz. The measured correlation lengths of these fluctuations suggest that they are coherent over only a few wavelengths. The analysis is consistent with the hypothesis that these fluctuations are driven by streaming ions, possibly protons. No evidence for the existence of whistler waves is found. It is argued that some of the observed spectral features suggest that dynamical turbulent processes are occurring in the uptream wave region, including a possible observation of an inverse cascade of magnetic helicity to large spatial scales.

Smith, C. W.↗
NASA NTRS2012

Interpretation of Vector Electric Field Measurements of Bursty Langmuir Waves in the Cusp

An analysis of auroral Langmuir waves in the cusp observed by two high-frequency electric field instruments on the TRICE high-flyer sounding rocket shows many examples of Langmuir wave bursts modulated at approximately 10 kHz. Previous studies have explained these and similar observations as the result of beating between waves with very close frequencies near the Langmuir cutoff, resulting from either wave-wave interactions or independent linear excitations. The unique three-dimensional (3-D) data set provided by the NASA Goddard Space Flight Center TAEFWD instrument shows that up to 25% of waveforms selected from the most intense bursts exhibit anisotropic modulations, i.e., the beat nulls and peaks are not aligned in time across the three perpendicular electric field components. Modulations of this type arise when superposed wave normal modes possess differing polarizations, and simulations using wave modes calculated with the J-WHAMP numerical dispersion code show (1) that waves with differing polarizations can exist in conditions like those observed by TRICE-High and (2) that superpositions of such waves can produce anisotropic modulation. Fourier analysis of the 3-D waveform data suggests that both linear and elliptically polarized waves are present near the Langmuir cutoff at these times. These observations illustrate how 3-D measurements can give valuable insight into the nature of wave interactions in the auroral plasma environment.

Dombrowski, M. P.↗
DOE OSTI2020

Slider Crank WEC Performance Analysis with Adaptive Autoregressive Filtering

This paper investigates a performance analysis of wave excitation force prediction to extract wave power for a slider crank power take-off system (PTOS) based on auto regressive (AR) filters. To efficiently convert wave energy into electricity, the prediction of wave excitation forces to keep the generator and the wave excitation force in sync is important for maximum energy extraction. The study shows a prediction methodology of half period and zero crossings in the practical scenario of irregular ocean waves. The prediction has been tested for different wave periods and with different filter orders. The prediction results have been used in the PTOS simulation to analyze the energy extraction. It has been shown that the prediction accuracy in the wave half period between the truth data and the predicted data drives the WEC energy extraction efficiency. The amplitude of the wave force is not used and hence the prediction deviation in the wave force amplitude does not affect the PTOS energy extraction. Further analysis shows that the optimum energy can be extracted at 15 th order filter with moderate prediction horizon length.

autoregressive filter↗
NASA NTRS1985

Observation and analysis of thunderstorm-generated gravity waves in the lower stratosphere

The relation between internal gravity waves and thunderstorms may be important in at least two respects. First, thunderstorm cells could be excited or initiated by propagating gravity waves in the troposphere. Second, thunderstorms may contribute to the energy of the atmospheric gravity wave field. Observations of gravity waves associated with thunderstorms are analyzed. The analysis will emphasize the difference of thunderstorm-generated gravity waves in the troposphere and lower stratosphere.

Lu, D.↗
NASA NTRS1994

Slow Wave Vane Structure with Elliptical Cross-Section Slots, an Analysis

Mathematical analysis of the wave equation in cylinders with elliptical cross-section slots was performed. Compared to slow wave structures with rectangular slots higher impedance and lower power dissipation losses are evident. These features could lead to improved designs of traveling wave magnetrons and gigahertz backward-wave oscillators as well as linear traveling wave tubes with relatively shallow slots.

Kosmahl, Henry G.↗
DOE OSTI2025

Insights into distorted lamellar phases with small-angle scattering and machine learning

Lamellar phases are essential in various soft matter systems, with topological defects significantly influencing their mechanical properties. In this report, we present a machine-learning approach for quantitatively analyzing the structure and dynamics of distorted lamellar phases using scattering techniques. By leveraging the mathematical framework of Kolmogorov–Arnold networks, we demonstrate that the conformations of these distorted phases – expressed as superpositions of complex waves – can be reconstructed from small-angle scattering intensities. Through the contour analysis of wave field phase singularities, we obtain the statistics of the spatial distribution of topological defects. Furthermore, we establish that the temporal evolution of these defects can be derived from the time-dependent traveling wave field, informed by the dispersion relation of spectral components. This method opens new avenues for investigating the dynamics of distorted lamellar phases using various dynamic scattering techniques such as neutron spin echo and X-ray photon correlation spectroscopy. These findings enhance our microscopic understanding of how defects influence the physical properties of lamellar materials, with implications for both equilibrium and non-equilibrium states in general lamellar systems.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Aerodynamic-Analysis Programs For Microcomputers

Lifts, drags, and moments calculated for subsonic and supersonic speeds. Series of computer programs used for aerodynamic analysis at NASA Langley Research Center modified for use on microcomputer. Programs include aerodynamic-analysis program for low-speed wing and flap systems (SUBAERF), supersonic-wave-drag-analysis program (WDRAG2), and supersonic-lifting-surface program (Lift Analysis). Set up to run from common geometry format with appropriate additional input data for each particular program. Package written in FORTRAN 77.

Knapp, Marie L.↗
NASA NTRS1991

Monte Carlo analysis of dissociation and recombination behind strong shock waves in nitrogen

Computations are presented for the relaxation zone behind strong, 1D shock waves in nitrogen. The analysis is performed with the direct simulation Monte Carlo method (DSMC). The DSMC code is vectorized for efficient use on a supercomputer. The code simulates translational, rotational and vibrational energy exchange and dissociative and recombinative chemical reactions. A model is proposed for the treatment of three body-recombination collisions in the DSMC technique which usually simulates binary collision events. The model improves previous models because it can be employed with a large range of chemical-rate data, does not introduce into the flow field troublesome pairs of atoms which may recombine upon further collision (pseudoparticles) and is compatible with the vectorized code. The computational results are compared with existing experimental data. It is shown that the derivation of chemical-rate coefficients must account for the degree of vibrational nonequilibrium in the flow. A nonequilibrium-chemistry model is employed together with equilibrium-rate data to compute the flow in several different nitrogen shock waves.

Boyd, I. D.↗
DOE OSTI2022

Rapid attribution analysis of the extraordinary heat wave on the Pacific coast of the US and Canada in June 2021

Towards the end of June 2021, temperature records were broken by several degrees Celsius in several cities in the Pacific Northwest areas of the US and Canada, leading to spikes in sudden deaths and sharp increases in emergency calls and hospital visits for heat-related illnesses. Here we present a multi-model, multi-method attribution analysis to investigate the extent to which human-induced climate change has influenced the probability and intensity of extreme heat waves in this region. Based on observations, modelling and a classical statistical approach, the occurrence of a heat wave defined as the maximum daily temperature (TXx) observed in the area 45–52 °N, 119–123 °W, was found to be virtually impossible without human-caused climate change. The observed temperatures were so extreme that they lay far outside the range of historical temperature observations. This makes it hard to state with confidence how rare the event was. Using a statistical analysis that assumes that the heat wave is part of the same distribution as previous heat waves in this region led to a first-order estimation of the event frequency of the order of once in 1000 years under current climate conditions. Using this assumption and combining the results from the analysis of climate models and weather observations, we found that such a heat wave event would be at least 150 times less common without human-induced climate change. Also, this heat wave was about 2 °C hotter than a 1-in-1000-year heat wave would have been in 1850–1900, when global mean temperatures were 1.2 °C cooler than today. Looking into the future, in a world with 2 °C of global warming (0.8 °C warmer than today), a 1000-year event would be another degree hotter. Our results provide a strong warning: our rapidly warming climate is bringing us into uncharted territory with significant consequences for health, well-being and livelihoods. Adaptation and mitigation are urgently needed to prepare societies for a very different future.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

NREL Waves to Water Prize Program: Sensitivity Analysis of Alternative Markets

Isle Inc., in collaboration with Engineering for Change (project team), performed a Sensitivity Analysis of market alternatives to evaluate commercialization barriers for the Waves to Water (W2W) competitors. This analysis included interviews with organizations and end-users in three market categories (1) Disaster Relief, (2) Commercial/Industrial, and (1) Municipal, Residential, and Government. For each category, the project team selected organizations that provided a well rounded experience and set of drivers for adopting W2W technologies. In addition to the project team's efforts, fellows from NREL/DOE completed interviews with government organizations to understand their potential to engage with W2W technologies, and these findings are summarized in a separate summary document.

16 TIDAL AND WAVE POWER↗