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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
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NASA NTRS2009

An Integrated Solution for Performing Thermo-fluid Conjugate Analysis

A method has been developed which integrates a fluid flow analyzer and a thermal analyzer to produce both steady state and transient results of 1-D, 2-D, and 3-D analysis models. The Generalized Fluid System Simulation Program (GFSSP) is a one dimensional, general purpose fluid analysis code which computes pressures and flow distributions in complex fluid networks. The MSC Systems Improved Numerical Differencing Analyzer (MSC.SINDA) is a one dimensional general purpose thermal analyzer that solves network representations of thermal systems. Both GFSSP and MSC.SINDA have graphical user interfaces which are used to build the respective model and prepare it for analysis. The SINDA/GFSSP Conjugate Integrator (SGCI) is a formbase graphical integration program used to set input parameters for the conjugate analyses and run the models. The contents of this paper describes SGCI and its thermo-fluids conjugate analysis techniques and capabilities by presenting results from some example models including the cryogenic chill down of a copper pipe, a bar between two walls in a fluid stream, and a solid plate creating a phase change in a flowing fluid.

Kornberg, Oren↗
NASA NTRS2012

3D Display Using Conjugated Multiband Bandpass Filters

Stereoscopic display techniques are based on the principle of displaying two views, with a slightly different perspective, in such a way that the left eye views only by the left eye, and the right eye views only by the right eye. However, one of the major challenges in optical devices is crosstalk between the two channels. Crosstalk is due to the optical devices not completely blocking the wrong-side image, so the left eye sees a little bit of the right image and the right eye sees a little bit of the left image. This results in eyestrain and headaches. A pair of interference filters worn as an optical device can solve the problem. The device consists of a pair of multiband bandpass filters that are conjugated. The term "conjugated" describes the passband regions of one filter not overlapping with those of the other, but the regions are interdigitated. Along with the glasses, a 3D display produces colors composed of primary colors (basis for producing colors) having the spectral bands the same as the passbands of the filters. More specifically, the primary colors producing one viewpoint will be made up of the passbands of one filter, and those of the other viewpoint will be made up of the passbands of the conjugated filter. Thus, the primary colors of one filter would be seen by the eye that has the matching multiband filter. The inherent characteristic of the interference filter will allow little or no transmission of the wrong side of the stereoscopic images.

Bae, Youngsam↗
NASA NTRS2020

How Magnetically Conjugate Atmospheres and the Magnetosphere Participate in the Formation of Low‐Energy Electron Precipitation in the Region of Diffuse Aurora

The electron precipitation in the region of the diffuse aurora should be considered as a two‐step process (Khazanov et al., 2017, https://doi.org/10.1002/2016GL072063). The first one is the interaction of plasma sheet electrons with electrostatic electron cyclotron and/or whistler waves, moving those electrons into the loss cone to precipitate in both magnetically conjugate atmospheres. The second step is the interaction of these electrons with the ionosphere and atmosphere via their elastic and nonelastic collisions and reflection (backscatter) of degraded electrons back to magnetosphere and conjugate ionospheres. This paper presents the results of a newly developed scenario of non steady‐state electron precipitation dynamics that accounts for magnetosphere‐ionosphere‐atmosphere energy interplay over the entire energy range of the plasma sheet electron population and their affiliated secondary electrons. It also studies how both magnetically conjugate auroral regions work together with the magnetosphere in the formation of electron precipitation in the region of the diffuse aurora with the energy range coverage from 1 eV up to 10 keV.

George V Khazanov↗
NASA NTRSDate not supplied

Assessment of Coupling One-Dimension and Three-Dimension CFD in Conjugate Heat Transfer Modeling and Simulations for Cooling of Turbine Engine

The CHT (conjugate heat transfer) modeling and simulation work fits under a bigger area in the TTT (Transformational Tools and Technologies) project called “Cooling Tools and Technologies for Combustor and Turbine.” The existing validation data sets such as TTT GRC (Glenn Research Center) THX (Turbulent Heat FLUX) IV experiments will be used to assess the solid/fluid heat transfer development and validation. The experimental configuration was a subsonic convergent nozzle with a square exit blowing a heated exhaust over an effusion-cooled deck. The simulation solutions were obtained and compared to experimental measurements of the profiles of flow velocities and temperatures, as well as deck surface temperatures. Cooling air blowing ratios of 0, 1, and 2 were considered. The three-dimensional cooling tubes were modelled by the medial axis of the cylindrical geometries due to large length over width ratios. It represented a typical coupling of one-dimension and three-dimension simulations of conjugate heat transfer approaches. The surface temperatures on the solid surfaces and the profiles of velocities and temperatures near the surfaces compared to the experimental data were presented.

nonlinear sub-filter stresses↗
NASA NTRS1972

Rocket measurements of conjugate photoelectrons during the total solar eclipse of 7 March 1970 over Wallops Island.

Results of measurements made with a retarding potential analyzer on a Nike-Tomahawk rocket during the totality of the solar eclipse, showing definite evidence for the existence of photoelectrons from the conjugate hemisphere. Photoelectrons are observed in the altitude range from 120 to 260 km. The observed flux in the energy range from 2 to 30 eV is relatively constant above about 200 km, but decreased below that altitude. The flux of 5-eV energy electrons above 200 km altitude is about 10 to the 7th power electrons/cm/sec/eV. Higher-energy electrons were also observed, and it is possible that the energy content of these observed fluxes of conjugate-point photoelectrons is sufficient to maintain the observed electron densities and temperatures during the total eclipse.

Maier, E. J.↗
NASA NTRS1973

Conjugate photoelectron excitation of O I 4368 airglow emission.

Conjugate photoelectron fluxes are shown to be mainly responsible for the excitation of O I 4368 radiation observed with a grille spectrometer located at Langmuir Laboratory, New Mexico (L equals 1.7). On the basis of observations of O I 7774 and 4368 tropical emissions at Agulhas, Negras, Brazil (L equals 1.1), the contribution of radiative recombination to the New Mexico intensity is shown to be small. Conjugate photoelectron excitation at the Brazilian site has not been observed.

Christensen, A. B.↗
NASA NTRS1974

L = 1.24 conjugate magnetic field line tracing experiments with barium shaped charges

Description of three experiments involving the injection of barium ions into magnetic flux tubes with the aid of high-explosive shaped charges with hollow conical liners of barium metal. In these experiments (called Alco, Bubia, and Loro, respectively) the explosive charges were detonated at altitudes above 500 km, producing jets of barium plasma with initial velocities ranging from 8 to 20 km/sec. The most interesting result of the experiments, which were carried out near L = 1.24 and were successful in tracing an entire field line some 7000 km to the conjugate ionosphere, was the observation that for Loro and probably Alco the direction and rate of drift of the two ends of the field line were identical, whereas those for Bubia differed significantly. In the case of the Bubia event significant differences in magnitude and direction at the conjugate points are noted, which lead to the conclusion that the field line could not have been equipotential during the interval of observation.

Wescott, E. M.↗
NASA NTRS1974

Conjugate excitation of atomic oxygen emissions in the far ultraviolet

Rocket observations of far-ultraviolet terrestrial airglow emissions in the 1230- to 1450-A band at night have been carried out from White Sands Missile Range. Three rockets carried 15.4-cm-diam far-ultraviolet telescopes to about 220 km altitude at various times during the night from postsunset to predawn. Postsunset and predawn observations were made when the solar zenith angle at the conjugate ionosphere was about 95 deg, and in both cases positive identification of strong O I 1304-A emissions was made. Evidence that in these cases the 1356/1304 intensity ratio was less than 0.2 is presented. Observations made well into the night yielded only an upper limit to the combined O I 1304- and 1356-A emissions of 20 Rayleighs, consistent with previous observations and theoretical calculations. These results show that meaningful rocket observations of the cosmic far ultraviolet background can be made only when the solar zenith angle at the conjugate ionosphere of the launch site is larger than 105 deg or if atomic oxygen emission lines are excluded from the detectors' bandpass.

Holberg, J.↗
NASA NTRS1976

Conjugate quasilinear Dirichlet and Neumann problems and a posteriori error bounds

Quasilinear Dirichlet and Neumann problems on a rectangle D with boundary D prime are considered. Using these concepts, conjugate problems, that is, a pair of one Dirichlet and one Neumann problem, the minima of the energies of which add to zero, are introduced. From the concept of conjugate problems, two-sided bounds for the energy of the exact solution of any given Dirichlet or Neumann problem are constructed. These two-sided bounds for the energy at the exact solution are in turn used to obtain a posteriori error bounds for the norm of the difference of the approximate and exact solutions of the problem. These bounds do not involve the unknown exact solution and are easily constructed numerically.

Lavery, J. E.↗
NASA NTRS1979

Phase conjugation method and apparatus for an active retrodirective antenna array

An active retrodirective antenna array wherein a reference array element is used to generate a phase reference which is replicated at succeeding elements of the array. Each element of the array is associated with a phase regeneration circuit and the phase conjugation circuitry of an adjacent element. In one implementation, the phase reference circuit operates on the input signal at the reference element, a voltage controlled oscillator (VCO) output signal and the input pilot signal at the next array element received from a transmission line. By proper filtering and mixing, a phase component may be produced to which the VCO may be locked to produce the phase conjugate of the pilot signal at the next array element plus a transmission line delay. In another implementation, particularly suited for large arrays in space, two different input pilot frequencies are employed.

Tausworthe, R. C.↗
NASA NTRS1984

Application of augmented-Lagrangian methods in meteorology: Comparison of different conjugate-gradient codes for large-scale minimization

A Lagrange multiplier method using techniques developed by Bertsekas (1982) was applied to solving the problem of enforcing simultaneous conservation of the nonlinear integral invariants of the shallow water equations on a limited area domain. This application of nonlinear constrained optimization is of the large dimensional type and the conjugate gradient method was found to be the only computationally viable method for the unconstrained minimization. Several conjugate-gradient codes were tested and compared for increasing accuracy requirements. Robustness and computational efficiency were the principal criteria.

Navon, I. M.↗
NASA NTRS1984

Temporal variations in the Siple Station conjugate area

The Siple Station conjugate locations in the Northern Hemisphere are examined for the epoch 1975-1990 according to the predictions of three internal source geomagnetic field models (1GRF 1980, Magsat 1980, Barraclough 1975) and one external field model (Mead/Fairfield) under quiet and disturbed conditions. The conjugate location systematically changes in the interval studied, making it imperative that changes be made in the locations of the Northern Hemisphere geophysical stations during the reactivation of Siple Station in 1985-1987.

Stassinopoulos, E. G.↗
NASA NTRS1986

Multi-color incomplete Cholesky conjugate gradient methods for vector computers

In this research, we are concerned with the solution on vector computers of linear systems of equations, Ax = b, where A is a larger, sparse symmetric positive definite matrix. We solve the system using an iterative method, the incomplete Cholesky conjugate gradient method (ICCG). We apply a multi-color strategy to obtain p-color matrices for which a block-oriented ICCG method is implemented on the CYBER 205. (A p-colored matrix is a matrix which can be partitioned into a pXp block matrix where the diagonal blocks are diagonal matrices). This algorithm, which is based on a no-fill strategy, achieves O(N/p) length vector operations in both the decomposition of A and in the forward and back solves necessary at each iteration of the method. We discuss the natural ordering of the unknowns as an ordering that minimizes the number of diagonals in the matrix and define multi-color orderings in terms of disjoint sets of the unknowns. We give necessary and sufficient conditions to determine which multi-color orderings of the unknowns correpond to p-color matrices. A performance model is given which is used both to predict execution time for ICCG methods and also to compare an ICCG method to conjugate gradient without preconditioning or another ICCG method. Results are given from runs on the CYBER 205 at NASA's Langley Research Center for four model problems.

Poole, E. L.↗
NASA NTRS1986

Lens collimation and testing using a Twyman-Green interferometer with a self-pumped phase-conjugating mirror

Ordinarily Twyman-Green interferometers are employed testing optical elements. In a modification of the basic configuration, the ordinary mirror in the test arm is replaced with a self-pumped phase-conjugating mirror using a barium titanate crystal. It is shown that, with a redefinition of components, the new configuration permits retention and improvement of the optical element testing function while simultaneously serving as a sensitive test for collimation. The optical path difference resulting from the double pass in the original Twyman-Green interferometer approximately equals that of the single pass and phase conjugation in the modification.

Howes, W. L.↗
NASA NTRS1987

Processing Conjugated-Diene-Containing Polymers

Diels-Alder reaction used to cross-linked thermoplastics. Process uses Diels-Alder reaction to cross-link and/or extend conjugated-diene-containing polymers by reacting them with bis-unsaturated dienophiles results in improved polymer properties. Quantities of diene groups required for cross-linking varies from very low to very high concentrations. Process also used to extend, or build up molecular weights of, low-molecular-weight linear polymers with terminal conjugated dienic groups.

Bell, Vernon L.↗
NASA NTRS1977

Process for crosslinking and extending conjugated diene-containing polymers

A process using a Diels-Alder reaction which increases the molecular weight and/or crosslinks polymers by reacting the polymers with bisunsaturated dienophiles is developed. The polymer comprises at least 75% by weight based on the reaction product, has a molecular weight of at least 5000 and a plurality of conjugated 1,3-diene systems incorporated into the molecular structure. A dienophile reaction with the conjugated 1,3-diene of the polymer is at least 1% by weight based on the reaction product. Examples of the polymer include polyesters, polyamides, polyethers, polysulfones and copolymers. The bisunsaturated dienophiles may include bis-maleimides, bis maleic and bis tumaric esters and amides. This method for expanding the molecular weight chains of the polymers, preferable thermoplastics, is advantageous for processing or fabricating thermoplastics. A low molecular weight thermoplastic is converted to a high molecular weight plastic having improved strength and toughness for use in the completed end use article.

Bell, Vernon L.↗
NASA NTRS1986

Large aperture interferometer with phase-conjugate self-reference beam

A large aperture self-referencing interferometer consisting of a Twyman-Green interferometer using a self-pumped phase conjugator in series with test section optics is described and experimentally demonstrated. This interferometer provides twice the fringe shift of a Mach-Zehnder (M-Z) interferometer for a given optical phase change induced within the test section. It also provides greater irradiance in the reference beam than does a similar series setup utilizing a M-Z interferometer incorporating a local reference beam. Whereas the ordinary interferometer records instantaneous conditions, the new one records overage conditions if a BaTiO3 crystal is used as the phase conjugator.

Howes, W. L.↗