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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

On the freestream matching condition for stagnation point turbulent flows

The problem of plane stagnation point flow with freestream turbulence is examined from a basic theoretical standpoint. It is argued that the singularity which arises from the standard kappa-epsilon model is not due to a defect in the model but results from the use of an inconsistent freestream boundary condition. The inconsistency lies in the implementation of a production equals dissipation equilibrium hypothesis in conjunction with a freestream mean velocity field that corresponds to homogeneous plane strain - a turbulent flow which does not reach such a simple equilibrium. Consequently, the adjustment that has been made in the constants of the epsilon-transport equation to eliminate this singularity is not self-consistent since it is tantamount to artificially imposing an equilibrium structure on a turbulent flow which is known not to have one.

Speziale, Charles G.↗
NASA NTRS1989

On the freestream matching condition for stagnation point turbulent flows

The problem of plane stagnation point flow with freestream turbulence is examined from a basic theoretical standpoint. It is argued that the singularity which arises from the standard kappa-epsilon model is not due to a defect in the model but results from the use of an inconsistent freestream boundary condition. The inconsistency lies in the implementation of a production equals dissipation equilibrium hypothesis in conjunction with a freestream mean velocity field that corresponds to homogeneous plane strain - a turbulent flow which does not reach such a simple equilibrium. Consequently, the adjustment that has been made in the constants of the epsilon-transport equation to eliminate this singularity is not self-consistent since it is tantamount to artificially imposing an equilibrium structure on a turbulent flow which is known not to have one.

Speziale, C. G.↗
NASA NTRS1958

Theoretical Rocket Performance of JP-4 Fuel with Several Fluorine-Oxygen Mixtures Assuming Equilibrium Composition

Theoretical rocket performance for equilibrium composition during expansion was calculated for JP-4 fuel with several fluorine-oxygen mixtures for a range of pressure ratios and oxidant-fuel ratios. The parameters included are specific impulse, combustion-chamber temperature, nozzle-exit temperature, molecular weight, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, isentropic exponent, viscosity, thermal conductivity, and equilibrium gas compositions. A correlation is given for the effect of chamber pressure on several of the parameters. The maximum value of specific impulse for a chamber pressure of 600 pounds per square inch absolute (40.827 atm) and an exit pressure of 1 atmosphere is 325.7 for 70.37 percent fluorine in the oxidant as compared with 284.9 and 305.1 for 100 percent oxygen and 100 percent fluorine, respectively.

Gordon, Sanford↗
NASA NTRS1980

Effect of ice-albedo feedback on global sensitivity in a one-dimensional radiative-convective climate model

The feedback between the ice albedo and temperature is included in a one-dimensional radiative-convective climate model. The effect of this feedback on global sensitivity to changes in solar constant is studied for the current climate conditions. This ice-albedo feedback amplifies global sensitivity by 26 and 39%, respectively, for assumptions of fixed cloud altitude and fixed cloud temperature. The global sensitivity is not affected significantly if the latitudinal variations of mean solar zenith angle and cloud cover are included in the global model. The differences in global sensitivity between one-dimensional radiative-convective models and energy balance models are examined. It is shown that the models are in close agreement when the same feedback mechanisms are included. The one-dimensional radiative-convective model with ice-albedo feedback included is used to compute the equilibrium ice line as a function of solar constant.

Wang, W.-C.↗
NASA NTRS1993

A thermal NO(x) prediction model - Scalar computation module for CFD codes with fluid and kinetic effects

A thermal NO(x) prediction model is developed to interface with a CFD, k-epsilon based code. A converged solution from the CFD code is the input to the postprocessing model for prediction of thermal NO(x). The model uses a decoupled analysis to estimate the equilibrium level of (NO(x))e which is the constant rate limit. This value is used to estimate the flame (NO(x)) and in turn predict the rate of formation at each node using a two-step Zeldovich mechanism. The rate is fixed on the NO(x) production rate plot by estimating the time to reach equilibrium by a differential analysis based on the reaction: O + N2 = NO + N. The rate is integrated in the nonequilibrium time space based on the residence time at each node in the computational domain. The sum of all nodal predictions yields the total NO(x) level.

Mcbeath, Giorgio↗
DOE OSTI2021

Solubility Product of Vanadinite Pb 5 (VO 4 ) 3 Cl at 25 °C—A Comprehensive Approach to Incongruent Dissolution Modeling

Although vanadinite (Pb 5 (VO 4 ) 3 Cl occurs in abundance in various terrestrial geochemical systems of natural and anthropogenic origin and is seriously considered as a potential nuclear waste sequestering agent, its actual application is severely limited by a lack of understanding of its basic thermodynamic parameters. In this regard, the greatest challenge is posed by its incongruent dissolution, which is a pivotal hurdle for effective geochemical modeling. Our paper presents an universal approach for geochemical computing of systems undergoing incongruent dissolution which, along with unique, long-term experiments on vanadinites’ stability, allowed us to determine the mineral solubility constant. The dissolution experiments were carried out at pH = 3.5 for 12 years. Vanadinite has dissolved incongruently, continuously re-precipitating into chervetite (Pb 2 V 2 O 7 ) with the two minerals remaining in mutual equilibrium until termination of the experiments. The empirically derived solubility constant K sp,V,298 = 10 –91.89 ± 0.05 of vanadinite was determined for the first time. The proposed modeling method is versatile and can be adopted to other mineral systems undergoing incongruent dissolution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Bond Dissociation Energies of the Actinide Halides AnX, An = Ac–Lr and X = F–I, Utilizing Relativistic Composite Coupled Cluster Approaches

Bond dissociation energies (BDEs) have been calculated for the set of actinide halides AnX with An=Ac, Pa, and Np-Lr and X=F-I. Two composite thermochemistry methods based on the Feller-Peterson-Dixon (FPD) approach have been utilized, one involving spinor-based relativistic CCSD(T) calculations where spin-orbit (SO) was included at the orbital level and another using scalar relativistic CCSD(T) with a posteriori SO contributions based on 2-component multireference configuration interaction calculations. The method that was chosen for a given actinide halide was based on which representation yielded the best single determinant reference determinant for the coupled cluster calculation. The spinor-based method was chosen for all cases except for AmX, CmX, and BkX. Both composite approaches included contributions accounting for basis set truncation, outer-core correlation, the Gaunt interaction, and QED. The scalar FPD results, as well as the spinor-based calculations for AcF, also included higher order electron correlation up through CCSDT(Q). In addition to BDEs, CCSD(T) equilibrium bond lengths, harmonic frequencies, and vibrational anharmonicity constants are reported for all species. Last, the FPD BDEs for the fluorides were used to confirm the trend across the actinide series previously predicted by Gibson using bonding models based atomic promotion energies that provide a single 6d electron for bonding. In particular the local minimum in the BDEs at AmF is confirmed in the present calculations. Furthermore, the BDEs for LrX are predicted to be slightly larger than those of AcX, making them the largest in the actinide halide series.

Actinides↗
DOE OSTI2022

Reversible Ligand Protonation in Noninnocent Constrained-Geometry-Like Group 4 Complexes

The proligands C 5 H 5 CMe 2 CHPhOx R (R = Me 2 , CHMe 2 , and CMe 3 ) react with M(NMe 2 ) 4 (M = Ti, Zr, and Hf) to give monodeprotonated (Ox R CHPhCMe 2 C 5 H 4 )M(NMe 2 ) 3 , doubly deprotonated (C 5 H 4 CMe 2 CPhOx R )M(NMe 2 ) 2 , or a mixture of both. The observed products depend on reaction conditions, the oxazoline substituent, and the metal center, with 4-t-butyl-oxazoline or Ti giving only the monodeprotonated (Ox R CHPhCMe 2 C 5 H 4 )M(NMe 2 ) 3 . Amine elimination from (Ox R CHPhCMe 2 C 5 H 4 )M(NMe 2 ) 3 to give (C 5 H 4 CMe 2 CPhOx R )M(NMe 2 ) 2 is reversible for 4,4-dimethyl- and 4-isopropyl-oxazoline-based ligands in Zr or Hf complexes. Temperature-dependent kinetic studies of the equilibration of (C 5 H 4 CMe 2 CPhOx Me2 )Zr(NMe 2 ) 2 , HNMe 2 and (Ox Me2 CHPhCMe 2 C 5 H 4 )Zr(NMe 2 ) 3 provide the experimental thermodynamic parameters ΔS° = -17.4 ± 2.6 cal·mol –1 K –1 and ΔH° = -6.8 ± 0.8 kcal·mol –1 . An Eyring plot of the rate constants, determined from the system as it approaches equilibrium, gives the activation entropy and activation enthalpy for the addition of (C 5 H 4 CMe 2 CPhOx Me2 )Zr(NMe 2 ) 2 and HNMe 2 as -36 ± 4 cal·mol –1 K –1 and 8.9 ± 1.3 kcal·mol –1 , respectively; the elimination of HNMe 2 from (Ox Me2 CHPhCMe 2 C 5 H 4 )Zr(NMe 2 ) 3 is characterized by ΔS ‡ = -19 ± 5 cal·mol –1 K –1 and ΔH ‡ = 15.7 ± 1.5 kcal·mol –1 . DFT computational models indicate a single-step, nonlinear transfer of the H between the benzylic position of the noninnocent, oxazoline-coordinated ligand and NMe 2 . Computations also confirm the negative activation entropy and the trends in the barriers support the experimental results. Together, these studies indicate the importance of steric effects from the oxazoline ligand, metal center, ancillary ligands, and leaving group on the shuttling of the proton between HNMe 2 and the noninnocent ligand. Finally, these effects suggest that coordination of oxazoline to the metal center is a key part of the benzylic deprotonation and noninnocent behavior of the cyclopentadienyl-oxazoline ligand.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Formation of the oxyl’s potential energy surface by the spectral kinetics of a vibrational mode

One of the most reactive intermediates for oxidative reactions is the oxyl radical, an electron-deficient oxygen atom. The discovery of a new vibration upon photoexcitation of the oxygen evolution catalysis detected the oxyl radical at the SrTiO3 surface. The vibration was assigned to a motion of the sub-surface oxygen underneath the titanium oxyl (Ti–O●−) created upon hole transfer to (or electron extraction from) a hydroxylated surface site. Evidence for such an interfacial mode is derived from its spectral shape, which exhibited a Fano resonance—a coupling of a sharp normal mode to continuum excitations. Here, this Fano resonance is utilized to derive precise formation kinetics of the oxyl radical and its associated potential energy surface (PES). From the Fano lineshape, the formation kinetics are obtained from the anti-resonance (the kinetics of the coupling factor), the resonance (the kinetics of the coupled continuum excitations), and the frequency integrated spectrum (the kinetics of the normal mode’s cross-section). All three perspectives yield logistic function growth with a half-rise of 2.3 ± 0.3 ps and a time constant of 0.48 ± 0.09 ps. A non-equilibrium transient associated with photoexcitation is separated from the rise of the equilibrated PES. The logistic function characterizes the oxyl coverage at the very initial stages (t ∼ 0) to have an exponential growth rate that quickly decreases toward zero as a limiting coverage is reached. Such time-dependent reaction kinetics identify a dynamic activation barrier associated with the formation of a PES and quantify it for oxyl radical coverage.

Chemistry↗
DOE OSTI2020

Mirror at the edge of the universe: Reflections on an accelerated boundary correspondence with de Sitter cosmology

An accelerated boundary correspondence (ABC) is solved for the de Sitter moving mirror cosmology. The beta Bogoliubov coefficients reveal the particle spectrum is a Planck distribution with temperature inversely proportional to horizon radius. The quantum stress tensor indicates a constant emission of energy flux consistent with eternal equilibrium, while the total energy carried by the particles remains finite. In conclusion, the curved spacetime transformation to flat spacetime with an accelerated boundary is illustrated, and also shown for anti-de Sitter (AdS) spacetime.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Manuscript model outputs, model source code, and figure scripts: The role of geomorphology in mediating biomass allocation impacts on salt-marsh resilience and carbon accumulation

This data package provides model source code (C++), model outputs, and figure generation scripts (R) needed to reproduce the following manuscript: Bruns, Nicholas E., Genevieve L. Noyce, and Matthew L. Kirwan. "The Role of Geomorphology in Mediating Biomass Allocation Impacts on Salt-Marsh Resilience and Carbon Accumulation." Estuarine, Coastal and Shelf Science 327 (December 2025): 109549. https://doi.org/10.1016/j.ecss.2025.109549. This manuscript investigates how geomorphology mediates the impact of biomass allocation shifts on salt marsh persistence and carbon (C) sequestration under sea level rise. We use a 1-D soil-column model (Kirwan and Mudd 2012) to perform experiments across a range of static root:shoot ratios (RSR = 1-4) spanning observed values. The model explicitly simulates interactions between tidal inundation, productivity, inorganic sediment deposition, and organic matter accumulation. Experiments determine whether geomorphic feedbacks amplify, dampen, or leave unchanged the ecosystem response to biomass allocation shifts. A first experiment uses constant sea level rise (2.5 mm/yr) to examine equilibrium dynamics and their influence on carbon accumulation rates across different suspended sediment concentrations (SSC). A second set of experiments calculates threshold sea level rise rates for marsh drowning across RSR and SSC combinations. Final experiments apply accelerating sea level rise scenarios (2000-2200) derived from NOAA projections (Sweet et al. 2022) to generate an envelope of expected responses, quantifying the importance of biomass allocation shifts on marsh carbon accumulation and persistence. All experiments are repeated across SSC ranging from 5-50 mg/L to investigate how these interactions vary in micro-tidal marshes with different sediment supplies. Package contents: * README.txt with detailed description of package contents and instructions for reproducing manuscript figures and model outputs * R scripts for generating all manuscript figures * C++ baseline model code from Kirwan and Mudd (2012) * C++ source code for 4 experimental model variants used in the manuscript, extending above baseline code * Model input files (.csv, .txt) including sea level rise scenarios * Model output files (.txt) used in manuscript analyses Temporal coverage: Model simulations span years 1900-2200, with accelerating sea level rise scenarios for 2000-2200. Key variables: Root:shoot ratio, suspended sediment concentration, carbon accumulation rate, vertical accretion rate, marsh elevation, inundation depth, threshold sea level rise rate.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1983

Theoretical study of silicon dicarbide

Silicon dicarbide was first observed in 1926 in spectra of cool carbon stars. The carrier of these bands around 5000 A was tentatively identified as SiC2 by Kleman (1956) who produced similar spectra by inserting silicon into the graphite tube of a King furnace heated to over 2500 K. This identification was strengthened by subsequent mass spectral studies which showed SiC2 as a major molecular component of vaporized silicon carbide. The present investigation is concerned with calculations which were initiated in an attempt to understand more recent astronomical observations of unidentified lines in the millimeter-wave region of the spectrum. The calculations were designed to determine the ground state equilibrium structure and to obtain vibrational and rotational constants. Calculations for estimating the positions and structure of low-lying electronic states were also performed. Self-consistent field (SCF) calculations were performed assuming a closed-shell electronic structure analogous to that in C3. Calculations were conducted for symmetric CSiC, and asymmetric SiCC forms.

Green, S.↗
NASA NTRS1999

Theory of Dust Voids in Plasmas

Dusty plasmas in a gas discharge often feature a stable void, i.e., a dust-free region inside the dust cloud. This occurs under conditions relevant to both plasma processing discharges and plasma crystal experiments. The void results from a balance of the electrostatic and ion drag forces on a dust particle. The ion drag force is driven by a flow of ions outward from an ionization source and toward the surrounding dust cloud, which has a negative space charge. In equilibrium the force balance for dust particles requires that the boundary with the dust cloud be sharp, provided that the particles are cold and monodispersive. Numerical solutions of the one-dimensional nonlinear fluid equations are carried out including dust charging and dust-neutral collisions, but not ion-neutral collisions. The regions of parameter space that allow stable void equilibria are identified. There is a minimum ionization rate that can sustain a void. Spatial profiles of plasma parameters in the void are reported. In the absence of ion-neutral collisions, the ion flow enters the dust cloud's edge at Mach number M = 1. Phase diagrams for expanding or contracting voids reveal a stationary point corresponding to a single stable equilibrium void size, provided the ionization rate is constant. Large voids contract and small voids expand until they attain this stationary void size. On the other hand, if the ionization rate is not constant, the void size can oscillate. Results are compared to recent laboratory and microgravity experiments.

Goree, J.↗
NASA NTRS1974

Turbulence measurements in an equilibrium hypersonic boundary layer

New quantitative turbulence measurements were obtained in a constant pressure, nonadiabatic hypersonic boundary layer, including the first higher moment and probability density measurements of mass-flow and total temperature fluctuations in hypersonic flow. The mass-flow and total temperature fluctuations show that the hypersonic data do not follow the trends set by lower Mach number adiabatic results. Measured intermittency distributions indicate substantial intermittency in the viscous sublayer and in the outer flow; significant differences between the present data and incompressible results are apparent. The higher moment and probability density data show that the character of the mass-flow and total temperature fluctuation modes are significantly different across the entire boundary layer. These differences together with turbulence scale and lifetime data obtained from autocorrelation and space-time correlation measurements are also discussed.-

Owen, F. K.↗
NASA NTRS1974

Radiative-dynamical equilibrium states for Jupiter

In order to obtain accurate estimates of the radiative heating that drives motions in Jupiter's atmosphere, previous radiative equilibrium calculations are improved by including the NH3 opacities and updated results for the pressure-induced opacities. These additions increase the radiative lapse rate near the top of the statically unstable region and lead to a fairly constant radiative lapse rate below the tropopause. The radiative-convective equilibrium temperature structure consistent with these changes is calculated, but it differs only slightly from earlier calculations. The radiative equilibrium calculations are used to calculate whether equilibrium states can occur on Jupiter which are similar to the baroclinic instability regimes on the earth and Mars. The results show that Jupiter's dynamical regime cannot be of this kind, except possibly at very high latitudes, and that its regime must be a basically less stable one than this kind.

Trafton, L. M.↗
NASA NTRS1987

A study of the mechanism of internal gravity wave generation by quasigeostrophic meteorological motions

Numerous experiments on the detection of atmospheric waves in the frequency range from acoustic to planetary at meteor heights have revealed that important wave sources are meteorological processes in the troposphere (cyclones, atmospheric fronts, jet streams, etc.). A dynamical theory based on the others work include describing the adaptation of meteorological fields to the geostropic equilibrium state. According to this theory, wave motions appear as a result of constant competition between the maladjustment of the wind and pressure fields due to nonlinear effects and the tendency of the atmosphere to establish a quasi-geostrophic equilibrium of these fields. These meteorological fields are discussed.

Medvedev, A. S.↗
NASA NTRS1992

Ortho-para-hydrogen equilibration on Jupiter

Voyager IRIS observations reveal that the Jovian para-hydrogen fraction is not in thermodynamic equilibrium near the NH3 cloud top, implying that a vertical gradient exists between the high-temperature equilibrium value of 0.25 at depth and the cloud top values. The height-dependent para-hydrogen profile is obtained using an anisotropic multiple-scattering radiative transfer model. A vertical correlation is found to exist between the location of the para-hydrogen gradient and the NH3 cloud, strongly suggesting that paramagnetic conversion on NH3 cloud particle surfaces is the dominant equilibration mechanism. Below the NH3 cloud layer, the para fraction is constant with depth and equal to the high-temperature equilibrium value of 0.25. The degree of cloud-top equilibration appears to depend on the optical depth of the NH3 cloud layer. Belt-zone variations in the para-hydrogen profile seem to be due to differences in the strength of the vertical mixing.

Carlson, Barbara E.↗
NASA NTRS1994

Computer program for calculation of complex chemical equilibrium compositions and applications. Part 1: Analysis

This report presents the latest in a number of versions of chemical equilibrium and applications programs developed at the NASA Lewis Research Center over more than 40 years. These programs have changed over the years to include additional features and improved calculation techniques and to take advantage of constantly improving computer capabilities. The minimization-of-free-energy approach to chemical equilibrium calculations has been used in all versions of the program since 1967. The two principal purposes of this report are presented in two parts. The first purpose, which is accomplished here in part 1, is to present in detail a number of topics of general interest in complex equilibrium calculations. These topics include mathematical analyses and techniques for obtaining chemical equilibrium; formulas for obtaining thermodynamic and transport mixture properties and thermodynamic derivatives; criteria for inclusion of condensed phases; calculations at a triple point; inclusion of ionized species; and various applications, such as constant-pressure or constant-volume combustion, rocket performance based on either a finite- or infinite-chamber-area model, shock wave calculations, and Chapman-Jouguet detonations. The second purpose of this report, to facilitate the use of the computer code, is accomplished in part 2, entitled 'Users Manual and Program Description'. Various aspects of the computer code are discussed, and a number of examples are given to illustrate its versatility.

Gordon, Sanford↗