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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Confinement and Kink Entanglement Asymmetry on a Quantum Ising Chain

In this work, we explore the interplay of confinement, string breaking and entanglement asymmetry on a 1D quantum Ising chain. We consider the evolution of an initial domain wall and show that, surprisingly, while the introduction of confinement through a longitudinal field typically suppresses entanglement, it can also serve to increase it beyond a bound set for free particles. Our model can be tuned to conserve the number of domain walls, which gives an opportunity to explore entanglement asymmetry associated with link variables. We study two approaches to deal with the non-locality of the link variables, either directly or following a Kramers-Wannier transformation that maps bond variables (kinks) to site variables (spins). We develop a numerical procedure for computing the asymmetry using tensor network methods and use it to demonstrate the different types of entanglement and entanglement asymmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

The Role of Surface Hydrophobicity on the Structure and Dynamics of CO2 and CH4 Confined in Silica Nanopores

Advancing a portfolio of technologies that range from the storage of excess renewable natural gas for distributed use to the capture and storage of CO 2 in geological formation are essential for meeting our energy needs while responding to challenges associated with climate change. Delineating the surface interactions and the organization of these gases in nanoporous environments is one of the less explored approaches to ground advances in novel materials for gas storage or predict the fate of stored gases in subsurface environments. To this end, the molecular scale interactions underlying the organization and transport behavior of CO 2 and CH 4 molecules in silica nanopores need to be investigated. To probe the influence of hydrophobic surfaces, a series of classical molecular dynamics (MD) simulations are performed to investigate the structure and dynamics of CO 2 and CH 4 confined in OH-terminated and CH 3 -terminated silica pores with diameters of 2, 4, 6, 8, and 10 nm at 298 K and 10 MPa. Higher adsorption extents of CO 2 compared to CH 4 are noted on OH-terminated and CH 3 -terminated pores. The adsorbed extents increase with the pore diameter. Further, the interfacial CO 2 and CH 4 molecules reside closer to the surface of OH-terminated pores compared to CH 3 -terminated pores. The lower adsorption extents of CH 4 on OH-terminated and CH 3 -terminated pores result in higher diffusion coefficients compared to CO 2 molecules. The diffusivities of both gases in OH-terminated and CH 3 -terminated pores increase systematically with the pore diameter. The higher adsorption extents of CO 2 on OH-terminated and CH 3 -terminated pores are driven by higher van der Waals and electrostatic interactions with the pore surfaces, while CH 4 adsorption is mainly due to van der Waals interactions with the pore walls. These findings provide the interfacial chemical basis underlying the organization and transport behavior of pressurized CO 2 and CH 4 gases in confinement.

Mohammed, Sohaib↗
DOE OSTI2024

Precision Synthesis of Conjugated Polymer Films by Surface-Confined Stepwise Sonogashira Cross-Coupling

Thin films of poly(arylene ethynylene)-conjugated polymers, including low-energy-gap donor–acceptor polymers, can be prepared via stepwise polymerization utilizing surface-confined Sonogashira cross-coupling. This robust and efficient polymerization protocol yields conjugated polymers with a precise molecular structure and with nanometer-level control of the organization and the uniform alignment of the macromolecular chains in the densely packed film. In addition to high stability and predictable and well-defined molecular organization and morphology, the surface-confined conjugated polymer chains experience significant interchain electronic interactions, resulting in dominating intermolecular π-electron delocalization which is primarily responsible for the electronic and spectroscopic properties of polymer films. The fluorescent films demonstrate remarkable performance in chemosensing applications, showing a turn-off fluorescent response on the sub-ppt (part per trillion) level of nitroaromatic explosives in water. This unique sensitivity is likely related to the enhanced exciton mobility in the uniformly aligned and structurally monodisperse polymer films.

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

Confinement performance predictions for a high field axisymmetric tandem mirror

This paper presents Hammir tandem mirror confinement performance analysis based on Realta Fusion's first-of-a-kind model for axisymmetric magnetic mirror fusion performance. This model uses an integrated end plug simulation model including, heating, equilibrium, and transport combined with a new formulation of the plasma operation contours (POPCONs) technique for the tandem mirror central cell. Using this model in concert with machine learning optimization techniques, it is shown that an end plug utilizing high temperature superconducting magnets and modern neutral beams enables a classical tandem mirror pilot plant producing a fusion gain Q > 5. The approach here represents an important advance in tandem mirror design. The high fidelity end plug model enables calculations of heating and transport in the highly non-Maxwellian end plug to be made more accurately. The detailed end plug modelling performed in this work has highlighted the importance of classical radial transport and neutral beam absorption efficiency on end plug viability. The central cell POPCON technique allows consideration of a wide range of parameters in the relatively simple near-Maxwellian central cell, facilitating the selection of more optimal central cell plasmas. These advances make it possible to find more conservative classical tandem mirror fusion pilot plant operating points with lower temperatures, neutral beam energies, and end plug performance requirements than designs in the literature. Despite being more conservative, it is shown that these operating points have sufficient confinement performance to serve as the basis of a viable fusion pilot plant provided that they can be stabilized against MHD and trapped particle modes.

FOS: Physical sciences↗
DOE OSTI2025

An Accurate SUPG-stabilized Continuous Galerkin Discretization for Anisotropic Heat Flux in Magnetic Confinement Fusion

We present a novel spatial discretization for the anisotropic heat conduction equation, aimed at improved accuracy at the high levels of anisotropy seen in a magnetized plasma, for example, for magnetic confinement fusion. The new discretization is based on a mixed formulation, introducing a form of the directional derivative along the magnetic field as an auxiliary variable and discretizing both the temperature and auxiliary fields in a continuous Galerkin (CG) space. Both the temperature and auxiliary variable equations are stabilized using the streamline upwind Petrov–Galerkin (SUPG) method, ensuring a better representation of the directional derivatives and therefore an overall more accurate solution. This approach can be seen as the CG-based version of our previous work (Wimmer, Southworth, Gregory, Tang, 2024), where we considered a mixed discontinuous Galerkin (DG) spatial discretization including DG-upwind stabilization. We prove consistency of the novel discretization, and demonstrate its improved accuracy over existing CG-based methods in test cases relevant to magnetic confinement fusion. This includes a long-run tokamak equilibrium sustainment scenario, demonstrating a 35% and 32% spurious heat loss for existing primal and mixed CG-based formulations versus 4% for our novel SUPG-stabilized discretization.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1974

Totally confined explosive welding

A method and associated apparatus for confining the undesirable by-products and limiting noise of explosive welding are discussed. The apparatus consists fo a simple enclosure into which the explosive is placed and within which the explosion occurs. The shape of the enclosure, the placement of the explosive, and the manner in which the enclosure is placed upon the material to be welded determine the force of the explosion transmitted to the proposed bond area. The explosion is totally confined within the enclosure thus reducing the noise level and preventing debris from being strewn about to contaminate the weld area or create personnel hazards.

Bement, L. J.↗
NASA NTRS1977

Alternative approaches to plasma confinement

The potential applications of fusion reactors, the desirable properties of reactors intended for various applications, and the limitations of the Tokamak concept are discussed. The principles and characteristics of 20 distinct alternative confinement concepts are described, each of which may be an alternative to the Tokamak. The devices are classed as Tokamak-like, stellarator-like, mirror machines, bumpy tori, electrostatically assisted, migma concept, and wall-confined plasma.

Roth, J. R.↗
NASA NTRS1977

Hydrostatic equilibrium of gas, extent of cosmic ray confinement, and radio emission in the Galaxy

A detailed study of the hydrostatic equilibrium of the gas-field system perpendicular to the galactic plane in the neighborhood of the sun, assuming that the magnetic field is parallel to the plane, has been carried out. It is found that the distribution of pressure due to cosmic rays and the magnetic field is different from that due to the gas. The observed radio spectrum in the direction of the galactic pole can be understood if one includes in the hydrostatic equilibrium the distribution of gas in the halo. The results of this analysis show that in the galactic plane, the cosmic-ray density is approximately 2 to 3 eV/cu cm with a magnetic-field strength of about 5 to 6 microgauss. It is inferred that cosmic rays are confined to a more extended volume in the Galaxy (with an equivalent thickness of at least 2 kpc in the solar neighborhood) than the gas disk, and the magnetic-field strength slowly decreases to a value of 1 microgauss only beyond about 5 kpc from the plane. Further, there is no evidence for a quasi-spherical radio halo, although the radio emission extends beyond the gas disk with scale height of at least 1 kpc. A lower limit of about 6 million years for the confinement of cosmic rays in the Galaxy has been set.

Badhwar, G. D.↗
NASA NTRS1977

Internal friction quality-factor Q under confining pressure

It has been found in previous studies that small amounts of adsorbed volatiles can have a profound effect on the internal friction quality-factor Q of rocks and other porous media. Pandit and Tozer (1970) have suggested that the laboratory-measured Q of volatile-free rocks should be similar to the in situ seismic Q values of near-surface lunar rocks which according to Latham et al. (1970) are in the range of 3000-5000. Observations of dramatic increases in Q with outgassing up to values approaching 2000 in the seismic frequency range confirm this supposition. Measurements under confining pressures with the sample encapsulated under hard vacuum are reported to aid in the interpretation of seismic data obtained below the lunar surface. It has been possible to achieve in the experiments Q values just under 2000 at about 1 kbar for a terrestrial analog of lunar basalt. It was found that a well-outgassed sample maintains a high Q whereas one exposed to moisture maintains a low Q as the confining pressure is raised to 2.5 kbar. This result suggests that volatiles can indeed affect Q when cracks are partially closed and the high lunar seismic Q values reported are concomitant with very dry rock down to depths of at least 50 km.

Tittmann, B. R.↗
NASA NTRS1978

Totally confined explosive welding

The undesirable by-products of explosive welding are confined and the association noise is reduced by the use of a simple enclosure into which the explosive is placed and in which the explosion occurs. An infrangible enclosure is removably attached to one of the members to be bonded at the point directly opposite the bond area. An explosive is completely confined within the enclosure at a point in close proximity to the member to be bonded and a detonating means is attached to the explosive. The balance of the enclosure, not occupied by explosive, is filled with a shaped material which directs the explosive pressure toward the bond area. A detonator adaptor controls the expansion of the enclosure by the explosive force so that the enclosure at no point experiences a discontinuity in expansion which causes rupture. The use of the technique is practical in the restricted area of a space station.

Bement, L. J.↗
NASA NTRS1978

Magnetically confined plasma solar collector

The possibility of using a plasma medium for collecting solar energy in space is examined on the basis of a concept involving an orbiting magnetic bottle in which a solar-energy-absorbing plasma is confined. A basic system uses monatomic cesium as working fluid. Cesium evaporates from a source and flows into the useful volume of a magnetic bottle where it is photoionized by solar radiation. Ions and electrons lost through the loss cones are processed by a recovery system, which might be a combination of electromagnetic devices and heat engines. This study concentrates on the plasma production processes and size requirements, estimates of the magnetic field required to confine the plasma, and an estimate of the system parameters for a 10 GW solar collector using cesium.

Walters, C. T.↗
NASA NTRS1979

Lean combustion limits of a confined premixed-prevaporized propane jet

An experimental study was carried out to determine the effects of jet velocity and confinement on lean premixed-prevaporized propane/air blowout limits. The combustor consisted of a single hole flameholder within a quartz liner. Five flameholder plates and two quartz liners were used. Lean stability limits were mapped for confined propane jet in cylindrical combustor. Three zones of flame stability were observed depending on the liner and jet Reynolds number and the combustor geometry. At low Reynolds number the combustor was jet stabilized. As the Reynolds number was increased the combustor became either recirculation zone stabilized, or for small recirculation zone step sizes, the combustor was wall stabilized. The factors affecting stability seem to be the Reynolds numbers of the liner and inlet jet along with the flameholder step size. Stability was achieved at both laminar and turbulent conditions.

Huck, K. L.↗
NASA NTRS1981

The deflection of a jet by confining surfaces

Thrust vectoring can be provided by the turning of a jet exhaust by the presence of confining surfaces. This approach is analogous to the upper surface blowing (USB) concept. Mean velocities, velocity autocorrelations, and pressure-velocity correlations are measured. From the autocorrelation curves, the Taylor microscales and the integral length scales are calculated. Convection velocities are calculated from the velocity space-time correlations. Two different confining surfaces (one flat, one with large curvature) are placed adjacent to the lip of a circular nozzle, and the resultant effects on the flow field are determined. In addition, two velocity ratios (exit plane velocity to ambient stream velocity) are examined. The velocity measurements were made with a laser Doppler velocimeter in conjunction with a phase locked-loop processor. Pressure measurements were made using a 1/8th inch condensor type microphone.

Catalano, G. D.↗
NASA NTRS1983

Perspectives on the mixing of a row of jets with a confined crossflow

An interactive computer code, written for a microcomputer, is presented which displays 2-D and 3-D oblique plots of the temperature distribution downstream of jets mixing with a confined crossflow, for either single-side or opposed jet injection. Temperature profiles calculated with this routine are presented to show the effects of flow and geometric variables on the mixing. Examples are shown to illustrate the different perspectives on the mixing available by exercising various view options. In addition, the program is used to calculate profiles for opposed rows of jets with their centerlines in-line, by assuming that the confining effect of an opposite wall is equivalent to that of a plane of symmetry between opposed jets.

Holdeman, J. D.↗
NASA NTRS1983

Electrodynamic coupling in magnetically confined X-ray plasmas of astrophysical origin

Explicitly magnetic field-independent relationships that quantitatively connect the thermodynamic state of the confined beta-less-than-one X-ray plasma to the confining magnetic loop characteristics and the stressing velocity at beta greater than about one are presented. The derived relations fall into two categories: (1) diffuse heating resulting from efficient transport of energy throughout the magnetic loop volume, and (2) isolated heating within the electrodynamic dissipation shell. For each of these cases the Joule dissipation, shear viscous dissipation, and compressional dissipation are considered. Each of these models is characterized by three thermodynamic scalings that are parametrized by the magnetic loop properties and by the stressing velocity. Eliminating the magnetic field intermediary from these relations and normalizing the inverse aspect ratio and the magnetic expansion factor with respect to solar conditions results in a single, unique velocity scaling law for each model.

Ionson, J. A.↗
NASA NTRS1985

Confined turbulent swirling recirculating flow predictions

The capability and the accuracy of the STARPIC computer code in predicting confined turbulent swirling recirculating flows is presented. Inlet flow boundary conditions were demonstrated to be extremely important in simulating a flowfield via numerical calculations. The degree of swirl strength and expansion ratio have strong effects on the characteristics of swirling flow. In a nonswirling flow, a large corner recirculation zone exists in the flowfield with an expansion ratio greater than one. However, as the degree of inlet swirl increases, the size of this zone decreases and a central recirculation zone appears near the inlet. Generally, the size of the central zone increased with swirl strength and expansion ratio. Neither the standard k-epsilon turbulence mode nor its previous extensions show effective capability for predicting confined turbulent swirling recirculating flows. However, either reduced optimum values of three parameters in the mode or the empirical C sub mu formulation obtained via careful analysis of available turbulence measurements, can provide more acceptable accuracy in the prediction of these swirling flows.

Abujelala, M. T.↗
NASA NTRS1985

Observed antiprotons and energy dependent confinement of cosmic rays: A conflict?

In the frame work of energy dependent confinement for cosmic rays, the energy spectrum inside the source is flatter than that observed. Antiproton observation suggests large amount of matter is being traversed by cosmic rays in some sources. As a result, secondary particles are produced in abundance. Their spectra was calculated and it is shown that the energy dependent confinement model is in conflict with some observations.

Stephens, S. A.↗