| CHEMEQ2: A Solver for the Stiff Ordinary Differential Equations of Chemical Kinetics |
27 JUL 2001 |
67 pages |
| Authors:
David R. Mott; Elaine S. Oran; NAVAL RESEARCH LAB WASHINGTON DC
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 | This report describes and documents the subroutine CHEMEQ2, used to integrate stiff ordinary differential equations arising from reaction kinetics. This is a second generation improvement of CHEMEQ using a new quasi-steady-state predictor-corrector method that is A-stable for linear equations and second- order accurate. A single integration method can now be used for all species, regardless of the timescales of the individual equations. Start-up costs and memory requirements are low, so ... |
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| An Analysis of Lift-Off in Laminar Diffusion Flames |
11 JUN 2001 |
28 pages |
| Authors:
Sally A. Cheatham; Elaine S. Oran; NAVAL RESEARCH LAB WASHINGTON DC
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| A jet diffusion flame attached to a burner rim may lift off and become stabilized further downstream when the jet velocity is sufficiently increased. In turbulent jet diffusion flames, such liftoff has been described alternately as the result of a stabilized premixed flame base, and as the result of extinguished diffusion flamelets at the flame base. Laminar flames exhibit liftoff behavior as well, and possess a relatively simpler flame structure ... |
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| Design and Simulation of a Partially Confined Detonation Facility |
30 SEP 1997 |
26 pages |
| Authors:
Charles A. Lind; Jay P. Boris; Elaine S. Oran; NAVAL RESEARCH LAB WASHINGTON DC CENTER FOR COMPUTATIONAL PHYSICS DEVELOPMENTS
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| It is estimated that more than 500,000 tons of obsolete and unwanted conventional weapons exists in the United States. The disposal of these unexploded ordnances, in an environmentally sound and cost effective way, is of tantamount importance. Open-air burning and open-air detonation (OB/OD) are two of the most widely used methods to dispose of these unwanted energetic materials. This report describes our efforts to improve the environmental safety of OB/OD ... |
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| The Stability and Multiplicity of the Monotonic Lagrangian Grid |
28 MAY 97 |
28 pages |
| Authors:
Robert S. Sinkovits; Elaine S. Oran; Jay P. Boris; NAVAL RESEARCH LAB WASHINGTON DC CENTER FOR REACTIVE FLOW AND DYNAMICAL SYSTE MS
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| The Monotonic Lagrangian Grid (MLG) is a data structure in which nodes are ordered in a monotonic way such that those nodes which are close in physical space also have nearby indices in the data structure arrays. An MLG ordering for a given system of nodes, as defined by the monotonicity constraints, is not unique. For all but the smallest systems, the number of allowed orderings is extremely large with ... |
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| Simulations of Hypersonic Rarefied Gas Flows Using DSMC-MLG |
16 MAY 97 |
64 pages |
| Authors:
Thuong X. Nguyen; Choong K. Oh; Robert S. Sinkovits; Elaine S. Oran; John D. Anderson Jr; NAVAL RESEARCH LAB WASHINGTON DC SENIOR SCIENTIST FOR REACTIVE FLOW PHYSICS
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| The combined Direct Simulation Monte Carlo (DSMC) and Monotonic Lagrangian Grid (MLG) methodologies are used on the massively parallel Connection Machines CM-5 to solve for the properties of a low density hypersonic flow through a channel containing a wedge. Numerical issues related to grid generation around the obstacle, the effects of resolution in terms of the simulated to actual particle ratio, and the use of time-averaging to obtain a statistically ... |
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| A Theory of DDT in Unconfined Flames |
19 JUN 96 |
27 pages |
| Authors:
Alexei M. Khokhlov; Elaine S. Oran; J. C. Wheeler; NAVAL RESEARCH LAB WASHINGTON DC SENIOR SCIENTIST FOR REACTIVE FLOW PHYSICS
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| This paper outlines a theoretical approach for predicting the onset of detonation in unconfined turbulent flames. Two basic assumptions are made (1) the gradient mechanism is the inherent mechanism that leads to DDT in unconfined conditions, and (2) the sole mechanism for preparing the gradient in induction time is by turbulent mixing and local flame quenching. The criterion for DDT is derived in terms of the one-dimensional detonation wave thickness, ... |
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| Numerical Studies of the Ram Accelerator |
AUG 95 |
5 pages |
| Authors:
Elaine S. Oran; Chiping Li; K. Kailasanath; Jay P. Boris; NAVAL RESEARCH LAB WASHINGTON DC
|
| Multidimensional, reactive flow simulations were used to provide the pressure information on the projectile for studying the projectile stability and the starting process of the thermally choked ram accelerator. The results showed that the pressure distribution on the front part of the projectile was controlled by a series of reflected shock and expansion waves. These reflected pressure waves were quite stable and virtually steady. A perturbation in the projectile position ... |
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| LCPFCT-A Flux-Corrected Transport Algorithm for Solving Generalized Continuity Equations |
16 APR 93 |
134 pages |
| Authors:
Jay P. Boris; Alexandra M. Landsberg; Elaine S. Oran; John H. Gardner; NAVAL RESEARCH LAB WASHINGTON DC
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| Flux-Corrected Transport has proven to be an accurate and easy to use an algorithm to solve nonlinear, time-dependent continuity equations of the type which occur in fluid dynamics, reactive, multiphase, and elastic plastic flows, plasmadynamics, and magnetohydrodynamics. This report updates and supersedes a previous report entitled Flux-Corrected Transport Modules for Solving Generalized Continuity Equations. It can be used as a user manual for subroutines and test programs included in the ... |
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| Numerical Studies for the RAM Accelerator |
23 DEC 92 |
19 pages |
| Authors:
Elaine S. Oran; Chiping Li; K. Kailasanath; NAVAL RESEARCH LAB WASHINGTON DC LAB FOR COMPUTATIONAL PHYSICS AND FLUID DYNA MICS
|
| Time-dependent, multidimensional computations were performed to study basic issues related to the structure of shocks, detonations, and modes of combustion affecting the feasibility or performance of the ram accelerator. A focus was on understanding of the structure and stability of oblique detonations generated by oblique shocks in supersonic fuel-air mixtures. The simulations show that steady, oblique detonations can be stabilized in supersonic flows and that they have very complex, multidimensional ... |
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| Molecular Dynamics of Shocks in Crystals with Defects |
15 JUL 92 |
43 pages |
| Authors:
Lee Phillips; Robert S. Sinkovits; Elaine S. Oran; Jay P. Boris; NAVAL RESEARCH LAB WASHINGTON DC
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| We examine, using computational molecular dynamics, shocks launched in two-dimensional crystals by a flying plate. The interaction of the shock with various lattice defects is observed, and is seen to create sites of rapidly growing, thermalized, hot fluid-like phases included within the crystal lattice. We hypothesize that these included fluid-like regions are the sites of the initial chemical reactions leading to detonation in energetic materials, and that crystallographic defects therefore ... |
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| Numerical Simulations of Spontaneous Ignition and Detonation in Propane- Air Mixtures |
06 JUL 92 |
39 pages |
| Authors:
Carolyn R. Kaplan; Elaine S. Oran; NAVAL RESEARCH LAB WASHINGTON DC
|
| The spontaneous ignition and subsequent detonation of propane-air mixtures caused by a weak shock in a partially confined volume containing an obstacle are studied using time-dependent numerical simulations. The motivation for this work is two-fold: first, to examine potential hazards from a leaking storage container (an obstacle to the flow), and second, to study the fundamental interaction of a shock wave with an obstacle in an energetic ambient gas. The ... |
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| International Workshop on Mathematical Methods in Combustion Held in Como, Italy on 18-22 May 1992 |
MAY 92 |
26 pages |
| Authors:
Luigi De Luca; Elaine S. Oran; M. Quinn. Brewster; Mikhail K. Strelets; Boris V. Novozhilov; POLITECNICO DI MILANO (ITALY) DIPT DI ENERGETICA
|
| The overall objective of the Workshop was to try to improve communications and promote cross-fertilizations between applied mathematicians and computational scientists, by pointing out promising directions as well as effective means of interaction. Specific objectives of the Workshop were to critically compare analytic to numerical approaches, assess potentials and limitations of both, and hopefully foster new developments in combustion. To this end, a proper mix of formal lectures, specialized presentations, ... |
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| Computations of Detonation Structure: The Influence of Model Input Parameters |
10 APR 92 |
22 pages |
| Authors:
Michel H. Lefebvre; Elaine S. Oran; K. Kailasanath; NAVAL RESEARCH LAB WASHINGTON DC
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| We describe analyses and numerical computations that examine the validity of certain common simplifications in the chemical and thermophysical model on the calculation of detonation properties. In particular, we examine the effects of (1) approximations of the temperature dependence of the specific heat C, and the ratio of specific heats Gamma = C(sub p) / C(sub v) in a detailed numerical simulation of detonation in a mixture of hydrogen and ... |
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| Numerical Simulations of Detonation Transmission |
03 SEP 91 |
49 pages |
| Authors:
Elaine S. Oran; David A. Jones; Martin Sichel; NAVAL RESEARCH LAB WASHINGTON DC
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| The complex, dynamic shock-detonation structure formed by the glancing interaction of a primary detonation with a secondary explosive is studied using time-dependent two-dimensional simulations and related experiments. The materials considered in the simulations are stoichiometric and lean mixtures of hydrogen and oxygen diluted with argon. Related experiments have used undiluted hydrogen and oxygen as well as other gases. The conditions simulated are; (a) the primary mixture is stoichiometric and the ... |
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| A One-Dimensional Flux-Corrected Transport Code for Detonation Calculations |
MAR 91 |
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| Authors:
David A. Jones; Elaine S. Oran; Raafat Guirguis; MATERIALS RESEARCH LABS ASCOT VALE (AUSTRALIA)
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 | The development of a one-dimensional Flux-Corrected Transport code to model detonation in a homogeneous medium is described. The material flow is modelled using the Euler equations, and the chemical kinetics by a two-step induction parameter model which uses a quasi-steady induction time and first order Arrhenius kinetics. Two different modes off initiation are compared. Conditions necessary for a self-sustaining detonation are described and illustrated. A detailed comparison is made between ... |
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| Dynamics of an Unsteady Diffusion Flame: Effects of Heat Release and Gravity |
27 SEP 90 |
19 pages |
| Authors:
Janet L. Ellzey; Elaine S. Oran; NAVAL RESEARCH LAB WASHINGTON DC
|
| This report presents time-dependent axisymmetric numerical simulations of an unsteady diffusion flame formed between a jet and a coflowing air stream. The computations include the effects of convection, molecular diffusion, thermal conduction, viscosity, gravitational forces, and chemical reactions with energy release. Previous work has shown that viscous effects are important in these flames and, therefore, all of the viscous terms in the compressible Navier-Stokes equations are included. In addition, the ... |
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| Numerical Simulations of Flowfields in a Central-Dump Ramjet Combustor. 3. Effects of Chemistry |
23 JUL 90 |
52 pages |
| Authors:
Kazhikathra Kailasanath; John H. Gardner; Jay P. Boris; Elaine S. Oran; NAVAL RESEARCH LAB WASHINGTON DC
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| This report is the third in a series which presents the results of numerical simulations performed to isolate and study acoustic-vortex-chemical interactions in an idealized ramjet consisting of an axisymmetric inlet and combustor and a choked nozzle. Both reactive and nonreactive flows have been simulated. The nonreactive flow calculations show complex interactions among the natural instability frequency of the shear layer at the inlet-combustor junction and the acoustics of both ... |
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| Surface Tension and Viscosity with Lagrangian Hydrodynamics on a Triangular Mesh |
18 MAR 88 |
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| Authors:
David E. Fyfe; Elaine S. Oran; M. J. Fritts; NAVAL RESEARCH LAB WASHINGTON DC
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| Numerical algorithms for surface tension and viscosity are presented in the context of a Lagrangian treatment of incompressible hydrodynamics with a dynamically restructuring grid. New algorithms are given which update previous Lagrangian approaches in the code SPLISH. Test problems involving internal gravity and capillary waves, an oscillating droplet and a viscous shear layer are described. An example is given of a flow calculated in and around a viscous droplet with ... |
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| Approaches to Resolving and Tracking Interfaces and Discontinuties |
28 JUL 87 |
30 pages |
| Authors:
K. J. Laskey; Elaine S. Oran; J. P. Boris; NAVAL RESEARCH LAB WASHINGTON DC
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| A review is presented of methods of modeling interfaces in numerical simulations. Interface capturing methods, in which the finest scales of the interface are resolved, and interface tracking approaches methods, in which the interface is treated as a discontinuity are discussed. Interface tracking approaches include moving-grid methods, surface tracking methods, volume tracking methods, and gradient methods. Keywords: Interface tracking; Reactive flows. |
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| Direct Numerical Simulation of Axisymmetric Jets |
25 MAR 86 |
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| Authors:
F. F. Grinstein; Elaine S. Oran; J. P. Boris; NAVAL RESEARCH LAB WASHINGTON DC
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| We present results from numerical simulations of the evolution of the Kelvin-Helmholtz instability for an unforced, subsonic, compressible axisymmetric, spatially-evolving shear layer. In addition, we study the effect of small, random pressure fluctuations at the nozzle orifice on the growth of the mixing layers. These fluctuations model inflow perturbations in experimental flows arising from turbulence and boundary layers in the nozzle. The finite- difference numerical model used to perform the ... |
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| Numerical Simulation of Fuel Droplet Interactions and Breakup |
01 DEC 85 |
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| Authors:
Elaine S. Oran; David E. Fyfe; NAVAL RESEARCH LAB WASHINGTON DC
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| The objective of the research is to develop Lagrangian methods on triangular grids and apply these methods to the calculation of life-history and dynamics of fuel droplets. During the period October 1985 to September 1986, the two-dimensional code SPLISH was used to study droplet distortion and breakup due to shear flows. A preliminary calculation of droplet-droplet collision was performed. Further testing of the basic SPLISH hydrodynamic algorithms as well as ... |
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| A Review of Research in Chemical-Acoustic Coupling |
08 JUL 1983 |
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| Authors:
Elaine S. Oran; John H. Gardner; NAVAL RESEARCH LAB WASHINGTON DC
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| In this review we have summarized previous research in chemical- acoustic interactions and extracted from it those elements which may be most important to reactive flows of exothermic materials. (Author) |
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| The Ionospheric Response to Solar Flares. I. Effects of Approximations of Solar Flare EUV Fluxes |
16 JAN 1981 |
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| Authors:
Elaine S. Oran; John T. Mariska; NAVAL RESEARCH LAB WASHINGTON DC
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| SOLRAD and many other satellite systems have provided a large data base showing the time-dependent behavior of broad and band solar fluxes in the X-ray and EUV spectral regions. These bands are broad in the sense that one band may contain many ionospherically important spectral lines. We present results of tests performed to determine how this information can be best be used to predict the effects of a solar flare ... |
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| Approximate Equations for Transport Coefficients of Multicomponent Mixtures of Neutral Gases. |
19 NOV 1980 |
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| Authors:
J. Michael Picone; Elaine S. Oran; NAVAL RESEARCH LAB WASHINGTON DC
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| Reactive flow systems often consist of multicomponent mixtures of neutral gases. Accurate modelling of reactive flows will, in many cases, require the accurate representation of transport phenomena in the conservation equations. In this paper, we identify and derive accurate, easy-to-evaluate equations for the coefficients of (ordinary) diffusion, viscosity, thermal conductivity, and thermal diffusion. The paper also serves to introduce and supplement the standard references on the subject for readers who ... |
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| Detailed Modelling of Combustion Systems. |
12 NOV 1980 |
226 pages |
| Authors:
Elaine S. Oran; Jay P. Boris; NAVAL RESEARCH LAB WASHINGTON DC
|
| The purpose of this paper is to acquaint the reader with some of the basic principles of detailed modelling as applied to combustion systems. Detailed modelling is also known as numerical simulation. It can be used to describe the chemical and physical evolution of a complex reactive flow system by solving numerically the governing time-dependent conservation equations for mass, momentum and energy. Solving these equations requires input data such as ... |
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| The Effects of Electron-Neutral Collisions on the Intensity of Plasma Lines. |
17 OCT 1980 |
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| Authors:
Alice L. Newman; Elaine S. Oran; NAVAL RESEARCH LAB WASHINGTON DC
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| In the earth's ionosphere the presence of nonthermal electrons causes enhancements of the electron plasma line resonance observed by incoherent backscatter radar. This paper extends previous calculations of the plasma intensity by including resonance broadening due to electron neutral collisions. A BGK collision term is included in the derivation of the electron spectral density function obtained from Fluctuation Dissipation theory. Assuming the non-thermal electron distribution is a small perturbation on ... |
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| Vector Operations in a Dipole Coordinate System. |
07 MAY 1979 |
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| Authors:
Joseph H. Orens; Theodore R. Young Jr.; Elaine S. Oran; Timothy P. Coffey; NAVAL RESEARCH LAB WASHINGTON DC
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| For many physical systems, especially those in the earth's magnetosphere or in solar flares, the major component of the plasma motion is along the magnetic field which is approximately dipolar. For such systems, resolving the flow into dipole coordinates is often beneficial. This report presents a list of the most common mathematical formulas and operations used in the application of a dipole coordinate system. (Author) |
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| Low Altitude Plasma Line Anisotropy. |
OCT 1977 |
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| Authors:
Elaine S. Oran; Peter J. Palmadesso; NAVAL RESEARCH LAB WASHINGTON D C
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| Plasma line observations obtained from incoherent radar backscatter have been used as a groundbased method for deriving information about the size and anisotropy of the ionospheric photoelectron fluxes. In the past data interpretation has been confined to altitudes above the F2 peak. Measurements below the F2 peak consistently show an anisotropy in the ratio of the downshifted to upshifted amplitudes of 20-50% when it is generally assumed that diffusion processes ... |
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| Calculation of the Ionospheric Photoelectron Distribution Function. |
SEP 1976 |
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| Authors:
Elaine S. Oran; D. J. Strickland; NAVAL RESEARCH LAB WASHINGTON D C
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| Calculations of the photoelectron flux in the ionosphere have been obtained by solving the Boltzmann equation. The method is flexible enough to allow for a wide range of energy and angular dependences for both external and internal electron sources. Detailed comparisons of calculated and measured photoelectron fluxes show excellent agreement. A series of solutions is shown which indicates the sensitivity of the calculations to the solar zenith angle, isotropic versus ... |
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| The Aeronomy of Odd Nitrogen in the Thermosphere. II. Twilight Emissions. |
JUL 1975 |
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| Authors:
Darrell F. Strobel; Elaine S. Oran; P. D. Feldman; NAVAL RESEARCH LAB WASHINGTON D C
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| The previously developed model by Oran et al. (1975) for the aeronomy of odd nitrogen in the thermosphere is used to analyze AE data on N(doublet D) and NO published by Rusch et al. (1975) and the twilight NO emission data of Feldman and Takacs (1974). It is concluded that most NO(+) dissociative recombination events must produce N(doublet D), that N(doublet D) is quenched by O with a rate of ... |
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| Photochemically Induced Departures of (O) and (O2) from Diffusive Equilibrium Distributions. |
MAY 1975 |
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| Authors:
Elaine S. Oran; Darrell F. Strobel; NAVAL RESEARCH LAB WASHINGTON D C
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| Photochemically induced departures of (O) and (O2) from diffusive equilibrium distributions are found to depend principally on atmospheric composition, the solar flux between 1250-1750 A, and the euv solar flux which produces O2 dissociation indirectly through odd nitrogen chemistry. Above 200 km the (O2) concentrations are about 20-35% less than diffusive equilibrium concentrations given by a Jacchia model atmosphere, while the O concentrations are enhanced by about 10%. |
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| Numerical Evaluation of Oscillatory Integrals with Specific Application to the Modified Bessel Function (K sub i, zeta) (x). |
OCT 1974 |
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| Authors:
Jay P. Boris; Elaine S. Oran; NAVAL RESEARCH LAB WASHINGTON D C
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| The authors present an orthogonalized Fourier method for the numerical evaluation of oscillatory integrals which have an infinite range of integration. This method in contrast to others which have been developed, attains maximum efficiency in the limit of rapid oscillations. The results are compared to those obtained from a Gaussian integration scheme and the Shanks acceleration of the Gaussian results. Special attention is given to the evaluation of the modified ... |
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Reports by Author
