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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Thermal stability effects on the structure of the velocity field above an air-water interface

Mean velocity and turbulence measurements are described for turbulent flows above laboratory water waves, under various wind and thermal stratification conditions. Experimental results, when presented in the framework of Monin-Obukhov (1954) similarity theory, support local scaling based on evaluation of stratification effects at the same nondimensional distance from the mean water surface. Such scaling allows an extension of application of the above theory to the outer region of the boundary layer. Throughout the fully turbulent region, ratios of mean velocity gradients, eddy viscosities, and turbulence intensities under nonneutral and neutral conditions correlate well with the parameter z/Lambda (Lambda being a local Obukhov length and z the vertical coordinate of the mean air flow) and show good agreement with established field correlations. The influence of stratification on the wind-stress coefficient can be estimated from an empirical relationship in terms of its value under neutral conditions and a bulk Richardson number.

Papadimitrakis, Y. A.↗
NASA NTRS1993

Velocity distributions of hydrogen atoms and hydroxyl radicals produced through solar photodissociation of water

The velocity distributions of H and OH fragments produced through solar photodissociation of gaseous H2O molecules under collisionless conditions are presented. The calculations are carried out using: the most recently available absolute partial cross sections for the production of H and OH through photodissociation of H2O from its absorption onset at 1860 A down to 500 A; the newly available vibrational and rotational energy distributions of both the excited and ground state OH photofragments; the calculated cross sections for the total dissociation processes; and the integrated solar flux in 10 A increments from 500 to 1860 A in the continuum regions and the specific wavelength and flux at the bright solar lines. The calculated results show that the H atoms and the OH radicals produced exhibit multiple velocity groups. Since most current cometary modeling uses a single velocity of 20 km/sec associated with the photodissociation of H2O, the present results may be useful in interpreting the many peaks observed in the velocity distributions of the H Lyman alpha and H alpha of comets.

Wu, C. Y. R.↗
NASA NTRS1990

Bulk properties and velocity distributions of water group ions at Comet Halley - Giotto measurements

In the region upstream of Comet Halley, pickup heavy ions of cometary origin were directly observed by the implanted ion spectrometer on Giotto. Diffusion of this population in pitch angle and in energy, during the approach to the comet and on the outbound leg is discussed. The two data sets are compared and qualitative ideas on scattering timescales are inferred. In addition the bulk parameters of these distributions have been computed and a comparison of the observed speed in the solar wind frame and the observed density with expectations is presented. Pitch angle scattering occurs more slowly than expected with filled shells appearing at 2,500,000 km, and significant energy diffusion does not occur until the bow shock region. Also the shell distributions downstream of the shock flow at the bispherical bulk speed (related to the Alfven speed) along the magnetic field with respect to the solar wind in accordance with conservation of energy between the pickup ions and the wave turbulence.

Coates, A. J.↗
DOE OSTI2024

Airborne Measurements of Scale‐Dependent Latent Heat Flux Impacted by Water Vapor and Vertical Velocity Over Heterogeneous Land Surfaces During the CHEESEHEAD19 Campaign

Abstract The water vapor transport associated with latent heat flux (LE) in the planetary boundary layer (PBL) is critical for the atmospheric hydrological cycle, radiation balance, and cloud formation. The spatiotemporal variability of LE and water vapor mixing ratio ( r v ) are poorly understood due to the scale‐dependent and nonlinear atmospheric transport responses to land surface heterogeneity. Here, airborne in situ measurements with the wavelet technique are utilized to investigate scale‐dependent relationships among LE, vertical velocity ( w ) variance (), and r v variance () over a heterogeneous surface during the Chequamegon Heterogeneous Ecosystem Energy‐balance Study Enabled by a High‐density Extensive Array of Detectors 2019 (CHEESEHEAD19) field campaign. Our findings reveal distinct scale distributions of LE, , and at 100 m height, with a majority scale range of 120 m–4 km in LE, 32 m–2 km in , and 200 m–8 km in . The scales are classified into three scale ranges, the turbulent scale (8–200 m), large‐eddy scale (200 m–2 km), and mesoscale (2–8 km) to evaluate scale‐resolved LE contributed by and . The large‐eddy scale in PBL contributes over 70% of the monthly mean total LE with equal parts (50%) of contributions from and . The monthly temporal variations mainly come from the first two major contributing classified scales in LE, , and . These results confirm the dominant role of the large‐eddy scale in the PBL in the vertical moisture transport from the surface to the PBL, while the mesoscale is shown to contribute an additional ∼20%. This analysis complements published scale‐dependent LE variations, which lack detailed scale‐dependent vertical velocity and moisture information.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Millinocket Stream, Maine Velocity and Bathymetry Measurements 2021

ORPC staff collected site characterization data on Millinocket Stream, downstream of the hydropower station at the former Great Northern Paper Mill site in Millinocket, Maine. Bathymetry was collected with a SonTek M9 using HydroSurveyor software package and velocity was collected using the SonTek M9 RiverSurveyor software package. Bathymetry only was collected on 9/30/21. Bathymetry and velocity were collected on 10/21/21.

16 TIDAL AND WAVE POWER↗
NASA NTRS1986

Laser anemometry measurements of natural circulation flow in a scale model PWR reactor system

The natural circulation of a single phase fluid in a scale model of a pressurized water reactor system during a postulated grade core accident is analyzed. The fluids utilized were water and SF6. The design of the reactor model and the similitude requirements are described. Four LDA tests were conducted: water with 28 kW of heat in the simulated core, with and without the participation of simulated steam generators; water with 28 kW of heat in the simulated core, with the participation of simulated steam generators and with cold upflow of 12 lbm/min from the lower plenum; and SF6 with 0.9 kW of heat in the simulated core and without the participation of the simulated steam generators. For the water tests, the velocity of the water in the center of the core increases with vertical height and continues to increase in the upper plenum. For SF6, it is observed that the velocities are an order of magnitude higher than those of water; however, the velocity patterns are similar.

Kadambi, J. R.↗
NASA NTRS1986

Velocity-resolved observations of water in Comet Halley

An infrared spectrum of comet Halley was recorded at the Kuiper Airborne Observatory with an instrumental velocity resolution of 1.1 km/sec. A total of 13 emission lines in the 2.65 micron spectral region were assigned to neutral gaseous H2O : 10 in the 001 to 000 band and 3 in the hot 011 to 010 band. The position and widths of these lines are functions of the gas velocity field in the coma. Analysis indicates that the neutral gas outflow is widely dispersed about the nucleus. This spectroscopic picture is consistent with spacecraft images that show multiple jets releasing material into most of the sunfacing hemisphere.

Larson, Harold P.↗
NASA NTRS1936

The Effect of Water Vapor on Flame Velocity in Equivalent Carbon Monoxide and Oxygen Mixtures

This report presents the results of an investigation to study the effect of water vapor upon the spatial speed of flame in equivalent mixtures of carbon monoxide and oxygen at various total pressures from 100 to 780 mm.hg. These results show that, within this pressure range, an increase in flame speed is produced by increasing the mole fraction of water vapor at least as far as saturation at 25 degrees c., and that the rate of this increase is greater the higher the pressure. It is evident that water vapor plays an important part in the explosive oxidation of carbon monoxide; the need for further experimental evidence as to the nature of its action is indicated.

Fiock, Ernest F↗
NASA NTRS1986

Velocity-resolved observations of water in comet Halley

High-resolution observations of H2O in comet Halley are presented. The positions and widths of the H2O emission line profiles are indicative of the coma's velocity field characteristics. Spectral line shape changes are used to infer temporal variations in the kinematic properties of the outflow. The results suggest that H2O is released into the coma by way of multiple jets.

Larson, Harold P.↗
DOE OSTI2025

Invisible water in subducted crust: Lawsonite velocity anomalies under mantle conditions

Subduction zones transport significant amounts of water into Earth’s mantle, primarily through hydrous minerals such as lawsonite. However, the seismic detectability of lawsonite-bearing oceanic crust at mantle depths remains uncertain. To address this issue, we measured sound velocities of lawsonite up to 7.4 GPa and 600 °C. Both P- and S-wave velocities exhibited unexpected increases with temperature under high-pressure conditions. Our result suggest that hydrous oceanic crust exhibits higher seismic velocities than the surrounding mantle at depths of 150 to 250 km, resulting in high-velocity anomalies rather than the previously assumed low-velocity anomalies. Furthermore, the seismic velocity difference between hydrous and dry oceanic crust is less than 2%, making it challenging to distinguish between them using seismic velocities. This limitation may hinder the detection of the hydration state in subducted crust. In addition, lawsonite remains stable in 90% of subduction zones, and thus, such “seismically invisible water” may exist in most subducted slabs around the world.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Relaxation of molecular velocities and spectral line profiles of astrophysical masers

The rates at which the velocities of water molecules relax to a Maxwellian distribution are calculated under conditions that are representative of those in astrophysical water masers. Populations are calculated as a function of velocity for the lowest 40 rotational energy levels of ortho-water in order to make a detailed determination of the velocity relaxation rate. Relaxation rates for the 22 GHz maser at H2 densities of 10 exp 9/cu cm are 2.0/s and 5.1/s for temperatures of 400 K and 1000 K, respectively. Under these and other conditions, as well as for other maser transitions, the relaxation rate far exceeds the loss rate - usually by more than a factor of 10. Thus maser lines can remain narrow up to intensities that are at least a factor of 10 greater than the saturation intensity, and to path lengths that are at least a factor of 10 greater than the path length at which saturation occurs. Relaxation is dominated by the effects of trapped infrared radiation, though elastic and inelastic collisions are also included in the calculations. These relaxation rates, together with the observed line breadths of the 22 GHz masers, provide limits on maser luminosities which indicate that the brightest 22 GHz masers are highly beamed, with solid angles smaller than 10 exp -5 to 10 exp -4 Sr.

Anderson, Nels↗
DOE OSTI2020

Subcloud and Cloud-Base Latent Heat Fluxes during Shallow Cumulus Convection

Doppler and Raman lidar observations of vertical velocity and water vapor mixing ratio are used to probe the physics and statistics of subcloud and cloud-base latent heat fluxes during cumulus convection at the ARM Southern Great Plains (SGP) site in Oklahoma, United States. The statistical results show that latent heat fluxes increase with height from the surface up to ~0.8 Z i (where Z i is the convective boundary layer depth) and then decrease to ~0 at Z i . Peak fluxes aloft exceeding 500 W m −2 are associated with periods of increased cumulus cloud cover and stronger jumps in the mean humidity profile. These entrainment fluxes are much larger than the surface fluxes, indicating substantial drying over the 0–0.8 Z i layer accompanied by moistening aloft as the CBL deepens over the diurnal cycle. We also show that the boundary layer humidity budget is approximately closed by computing the flux divergence across the 0–0.8 Z i layer. Composite subcloud velocity and water vapor anomalies show that clouds are linked to coherent updraft and moisture plumes. The moisture anomaly is Gaussian, most pronounced above 0.8 Z i and systematically wider than the velocity anomaly, which has a narrow central updraft flanked by downdrafts. This size and shape disparity results in downdrafts characterized by a high water vapor mixing ratio and thus a broad joint probability density function (JPDF) of velocity and mixing ratio in the upper CBL. We also show that cloud-base latent heat fluxes can be both positive and negative and that the instantaneous positive fluxes can be very large (~10 000 W m −2 ). However, since cloud fraction tends to be small, the net impact of these fluxes remains modest.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1986

Velocity-resolved observations of water in Comet Halley

High resolution (lambda/delta lambda approx. = 3 x 10 to the 5th power) near-infrared observations of H2O emission from Comet Halley were acquired at the time of maximum post-perihelion geocentric Doppler shift. The observed widths and absolute positions of the H2O line profiles reveal characteristics of the molecular velocity field in the coma. These results support H2O outflow from a Sun-lit hemisphere or the entire nucleus, but not from a single, narrow jet emanating from the nucleus. The measured pre- and post-perihelion outflow velocities were 0.9 + or - 0.2 and 1.4 + or - 0.2 km/s, respectively. Temporal variations in the kinematic properties of the outflow were inferred from changes in the spectral line shapes. These results are consistent with the release of H2O into the coma from multiple jets.

Larson, Harold P.↗
NASA NTRS1944

The NACA Impact Basin and Water Landing Tests of a Float Model at Various Velocities and Weights

The first data obtained in the United States under the controlled testing conditions necessary for establishing relationships among the numerous parameters involved when a float having both horizontal and vertical velocity contacts a water surface are presented. The data were obtained at the NACA impact basin. The report is confined to a presentation of the relationship between resultant velocity and impact normal acceleration for various float weights when all other parameters are constant. Analysis of the experimental results indicated that the maximum impact normal acceleration was proportional to the square of the resultant velocity, that increases in float weight resulted in decreases in the maximum impact normal acceleration, and that an increase in the flight-path angle caused increased impact normal acceleration.

Batterson, Sidney A↗
DOE OSTI2020

Simulating the Multi-epoch Direct Detection Technique to Isolate the Thermal Emission of the Non-transiting Hot Jupiter HD187123b

We report the 6.5σ detection of water from the hot Jupiter HD187123b with a Keplerian orbital velocity K {sub p} of 53 ± 13 km s{sup −1}. This high-confidence detection is made using a multi-epoch, high-resolution, cross-correlation technique, and corresponds to a planetary mass of 1.4{sub −0.3}{sup +0.5} M {sub J} and an orbital inclination of 21° ± 5°. The technique works by treating the planet/star system as a spectroscopic binary and obtaining high signal-to-noise, high-resolution observations at multiple points across the planet’s orbit to constrain the system’s binary dynamical motion. All together, seven epochs of Keck/NIRSPEC L-band observations were obtained, with five before the instrument upgrade and two after. Using high-resolution SCARLET planetary and PHOENIX stellar spectral models, we were able to drastically increase the confidence of the detection by running simulations that could reproduce, and thus remove, the nonrandom structured noise in the final likelihood space well. The ability to predict multi-epoch results will be extremely useful for furthering the technique. Here, we use these simulations to compare three different approaches to combining the cross correlations of high-resolution spectra and find that the Zucker log(L) approach is least affected by unwanted planet/star correlation for our HD187123 data set. Furthermore, we find that the same total signal-to-noise ratio (S/N) spread across an orbit in many, lower S/N epochs rather than fewer, higher S/N epochs could provide a more efficient detection. This work provides a necessary validation of multi-epoch simulations, which can be used to guide future observations and will be key to studying the atmospheres of farther separated, non-transiting exoplanets.

79 ASTRONOMY AND ASTROPHYSICS↗