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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
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

The divergence of nearby trajectories in soft-sphere DEM

The n-body instability is investigated with the soft-sphere discrete element method. The divergence of nearby trajectories is quantified by the dynamical memory time. Using the inverse proportionality between the dynamical memory time and the largest Lyapunov exponent, the soft-sphere discrete element method results are compared to previous hard-sphere molecular dynamics data for the first time. Good agreement is observed at low concentrations and the degree of instability is shown to increase asymptotically with increasing spring stiffness. At particle concentrations above 30%, the soft-sphere Lyapunov exponents increase faster than the corresponding hard-sphere data. Finally, this paper concludes with a demonstration of how this case study may be used in conjunction with regression testing and code verification activities.

42 ENGINEERING↗
DOE OSTI2021

Using molten salts to probe outer-coordination sphere effects on lanthanide( III )/( II ) electron-transfer reactions

Controlling structure and reactivity by manipulating the outer-coordination sphere around a given reagent represents a longstanding challenge in chemistry. Despite advances toward solving this problem, it remains difficult to experimentally interrogate and characterize outer-coordination sphere impact. Here, this work describes an alternative approach that quantifies outer-coordination sphere effects. It shows how molten salt metal chlorides (MCl n ; M = K, Na, n = 1; M = Ca, n = 2) provided excellent platforms for experimentally characterizing the influence of the outer-coordination sphere cations (M n+ ) on redox reactions accessible to lanthanide ions; Ln 3+ + e 1– → Ln 2+ (Ln = Eu, Yb, Sm; e 1– = electron). As a representative example, X-ray absorption spectroscopy and cyclic voltammetry results showed that Eu 2+ instantaneously formed when Eu 3+ dissolved in molten chloride salts that had strongly polarizing cations (like Ca 2+ from CaCl 2 ) via the Eu 3+ + Cl 1– → Eu 2+ + ½Cl 2 reaction. Conversely, molten salts with less polarizing outer-sphere M 1+ cations (e.g., K 1+ in KCl) stabilized Ln 3+ . For instance, the Eu 3+ /Eu 2+ reduction potential was >0.5 V more positive in CaCl 2 than in KCl. In accordance with first-principle molecular dynamics (FPMD) simulations, we postulated that hard M n+ cations (high polarization power) inductively removed electron density from Ln n+ across Ln–Cl···M n+ networks and stabilized electron-rich and low oxidation state Ln 2+ ions. Conversely, less polarizing M n+ cations (like K 1+ ) left electron density on Lnn+ and stabilized electron-deficient and high-oxidation state Ln 3+ ions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Sockeye Validation Support Using the SPHERE Facility

The engineering-scale heat pipe application Sockeye, being developed through the Nuclear En- ergy Advanced Modeling and Simulation program is concurrently undergoing code development and verification and validation activities. The Single Primary Heat Extraction and Removal Emu- lator (SPHERE) facility at Idaho National Laboratory has performed numerous sodium heat pipe experiments, one of which is modeled in this work to support Sockeye validation. Heat pipe data produced by the SPHERE facility was found to be very useful not only for Sockeye validation but also as a useful resource for model development. A Sockeye simulation performed using Sockeye’s conduction model modeled an experimental run at SPHERE and was found to be able to accurately reproduce the steady temperature distribution but revealed discrepancies in transient behavior after shutoff of the power. This effort also revealed a number of challenges of modeling an experimental setup such as SPHERE, for example, the importance of details in the setup such as possible gaps in insulation. Also, continuous collaboration between Sockeye developers and SPHERE experimentalists has been established, which allows future experiments to be refined in response to questions and challenges found by simulating earlier experiments.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1928

Recent researches on the air resistance of spheres

The following conclusions on air resistance of spheres are drawn: 1) disturbances in front of the sphere and even single fine wires affect the critical Reynolds Number; 2) disturbances around the sphere increased the drag of the sphere without martially affecting the value of the Reynolds Number(sub crith); 3) great disturbances of the boundary layer of the sphere likewise change R.N.(sub crith); 4) turbulence of the approaching air stream lowers critical R.N.

AERODYNAMICS↗
DOE OSTI2020

Tailoring Polymer Colloids Derived Porous Carbon Spheres Based on Specific Chemical Reactions

Porous carbon spheres derived from polymer colloids with regular geometry, monodispersed morphology, well-controlled contents and structures play important roles in many areas of application, such as energy storage/conversion, gas adsorption/separation, catalysis, and chemo-photothermal therapy. Suitable polymerization reaction and synthetic strategy are both critical for the obtainment of stable polymer colloids as carbon precursors. Basic polymerization reactions are the cornerstones of synthetic strategies, which directly provides the direct molecular-based design of functionalized polymer/ carbon spheres. Thus, this progress report mainly focuses on the summary of suitable polymerization reactions for colloidal polymer derived porous carbon spheres. Recent advances in the synthetic strategies and applications are also discussed, including their corresponding polymerization reactions. Finally, the perspectives for the development of polymer derived porous carbon spheres are provided based on the controlled synthesis of polymer colloids and optimization over the carbonization process to achieve highly functionalized carbon spheres for practical applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Improved reference system for the corrected rigid spheres equation of state model

The Corrected Rigid Spheres (CRIS) EOS model, developed from fluid perturbation theory using a hard sphere reference system, has been successfully used to calculate the EOS of many materials, including gases and metals. The radial distribution function (RDF) plays a pivotal role in choosing the sphere diameter, through a variational principle, as well as the thermodynamic response. Despite its success, the CRIS model has some shortcomings in that it predicts too large a temperature for liquid-vapor critical points, can break down at large compression, and is computationally expensive. In this paper, we first demonstrate that an improved analytic representation of the hard sphere RDF does not alleviate these issues. Relaxing the strict adherence of the RDF to hard spheres allows an accurate fit to the isotherms and vapor dome of the Lennard-Jones fluid using an arbitrary reference system. Second order correction are eliminated, limiting the breakdown at large compression and significantly reducing the computation cost. The transferrability of the new model to real systems is demonstrated on argon, with an improved vapor dome compared to the original CRIS model.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1972

Critical levitation loci for spheres on cryogenic fluids.

The conditions which allow a fluid to support a sphere having a higher specific gravity than its own are investigated. Three basic parameters which together define the maximum floating conditions are considered, including the Bond number, the wetting angle of the interface, and the ratio of solid-liquid specific gravities. The Bond number represents the ratio of buoyancy to surface tension forces. An analysis of the forces at the sphere-liquid interface is conducted to determine the optimum levitation loci, that is, the conditions permitting flotation of a maximum density sphere. Data for glycerine, carbon tetrachloride, and water spheres floating on a liquid nitrogen surface appear to be in good agreement with the analysis. Data for Teflon spheres on water also appear to be in agreement with the analytical results.

Hendricks, R. C.↗
NASA NTRS1974

Dual falling sphere determination of density and transition flow parameter

A new approach to the analysis of falling sphere drag data is described in which the data from two trajectories through the same region of the atmosphere are analyzed simultaneously. The analysis provides important aerodynamic information which is used to obtain an improved value of atmospheric density. The technique is applied to a set of falling sphere data in which a sphere transition-flow parameter and atmospheric density results are obtained in the 80-120 km region from published data for falling spheres over Kwajalein. Another set of data for a falling sphere test over Wallops Island is also analyzed with comparable results.

Karr, G. R.↗
NASA NTRS1982

Resonance frequency shift of an acoustic chamber containing a rigid sphere

The resonance frequency shift of an acoustic rectangular chamber due to the presence of a rigid sphere has been measured for l = 1,2 modes as a function of sphere size and position. The frequency shift is the results of volume exclusion and wave scattering. An analytical Green's function calculation was used to explain the data, providing excellent agreement between the measured and the calculated values. Also reported are similar measurements for a thin disk and the ratio of second harmonic to fundamental pressure as a function of sphere position. The measurement shows that the sphere reduces the first harmonic content, with sharply peaked suppression minima at specific sphere positions.

Leung, E.↗
NASA NTRS1984

Evaporative coating of a sphere from a point source

To optimize the procedure for evaporating a metal film onto a sphere, calculations of the film thickness distribution for various motions of the sphere have been carried out. These calculations, including shadowing effects of sphere support rods, are presented in this paper. Also, an apparatus and procedure for the evaporative coating of a sphere are described. A comparison of measured thickness with the calculated values is made for one example of sphere motion. The implications of the calculated results for coating techniques are discussed.

Strayer, D. M.↗
NASA NTRS1985

The importance of precision radar tracking data for the determination of density and winds from the high-altitude inflatable sphere

Analysis of inflatable sphere measurements obtained during the Energy Budget and MAP/WINE campaigns led to questions concerning the precision of the MPS-36 radar used for tracking the spheres; the compatibility of the sphere program with the MPS-36 radar tracking data; and the oversmoothing of derived parameters at high altitudes. Simulations, with winds having sinusoidal vertical wavelengths, were done with the sphere program (HIROBIN) to determine the resolving capability of various filters. It is concluded that given a precision radar and a perfectly performing sphere, the HIROBIN filters can be adjusted to provide small-scale perturbation information to 70 km (i.e., sinusoidal wavelengths of 2 km). It is recommended that the HIROBIN program be modified to enable it to use a variable length filter, that adjusts to fall velocity and accelerations to provide wind data with small perturbations.

Schmidlin, F. J.↗
NASA NTRS1985

Results of wind simulations in the mesosphere using precision C-band radars and the inflatable falling sphere technique

The inflatable sphere technique represents a relatively inexpensive approach for obtaining density and wind data between 30 and 90 km. The procedure in its current form is adequate for operational rocket network type application. However, detailed information is lost because of oversmoothing. The present study had the objective to determine whether more detailed wind profiles could be obtained using the inflatable falling sphere and Hirobin. Hirobin is the name for the sphere reduction program used at NASA Wallops Island, VA. In connection with the aim of the study, information had to be obtained regarding the precision of the radar used to track the sphere. For this purpose, data from three C-band radars, each with a different tracking precision, were simulated. On the basis of the results of the investigation, it is concluded that, given a radar with a known precision and a perfectly performing sphere, the Hirobin filters can be adjusted to provide small-scale wind information to about 70 km.

Schmidlin, F. J.↗
NASA NTRS1989

Evidence for accurate temperatures from the inflatable falling sphere

The experiments performed with the inflatable falling sphere technique, for middle atmosphere studies, are reported. It is shown to be a potentially high accurate and independent source of temperature measurement and an intrinsic method for establishing accuracy of other atmospheric measurement techniques. Theoretical derivation, simulations, and actual measurements show that the sphere's temperature data are accurate. It is demonstrated that retrieved temperatures from falling spheres are not significantly affected by linear bias in density caused by uncertainties in sphere mass, volume, or cross sectional area. Case studies illustrate the sphere's capability to produce accurate temperatures. Comparisons with Datasonde temperature measurements obtained close in time and space are in agreement below 60 km.

Schmidlin, F. J.↗
NASA NTRS1988

Pool boiling from rotating and stationary spheres in liquid nitrogen

Results are presented for a preliminary experiment involving saturated pool boiling at 1 atm from rotating 2 and 3 in. diameter spheres which were immersed in liquid nitrogen (LN2). Additional results are presented for a stationary, 2 inch diameter sphere, quenched in LN2, which were obtained utilizing a more versatile and complete experimental apparatus that will eventually be used for additional rotating sphere experiments. The speed for the rotational tests was varied from 0 to 10,000 rpm. The stationary experiments parametrically varied pressure and subcooling levels from 0 to 600 psig and from 0 to 50 F, respectively. During the rotational tests, a high speed photographic analysis was undertaken to measure the thickness of the vapor film surrounding the sphere. The average Nusselt number over the cooling period was plotted against the rotational Reynolds number. Stationary sphere results included local boiling heat transfer coefficients at different latitudinal locations, for various pressure and subcooling levels.

Cuan, Winston M.↗
NASA NTRS1991

A new method for visualizing data on a sphere

A method for visualizing data on a globe or unit sphere is described. Information that is distributed over a sphere - global oceanographic or geographic measurements, all-sky astronomy observations, or any quantities that are best represented in spherical coordinates - can benefit from this technique. Retaining a better sense of the geometry and information content of the data, 3D graphics can provide an unobstructed view of the entire sphere, without undue deformation of its surface area. A 'parameterized ray trace' produces look-up tables (LUTs) that can be used for all visualizations. The ray-trace result shows one or more spheres with the data as a texture map and three reflecting rectangles that 'mirror' the far sides of the sphere(s) into view. The LUTs need only be created once. No special purpose hardware is required beyond a PC or workstation that supports color. Examples from astronomical and geophysical datasets, which are commonly displayed with an area deforming (2D) projection, are presented.

Hon, David↗
NASA NTRS1935

Tests of Spheres with Reference to Reynolds Number, Turbulence, and Surface Roughness

The behavior of the Reynolds Number of the sphere is explained (in known manner) with the aid of the boundary-layer theory. Rear spindles may falsify, under certain conditions, the supercritical sphere drag, while suspension wires in the space behind the sphere leave no traceable influence. The critical Reynolds Number of the sphere was arrived at by an unconventional method; that is, by determining the critical wind speed at which the static pressure at the back of the sphere is the same as that of the undisturbed flow. The method makes it possible to interpret the critical Reynolds Number with only one test station.

Hoerner, S↗
NASA NTRS1996

Detecting the dynamical state of the atmosphere from the orbital decay of the ODERACS spheres

The orbital decay curve of a satellite having constant cross-sectional area and in circular orbit can furnish valuable information regarding the dynamical state of the atmosphere. It is shown that a rectilinear decay curve having constant downward slope (zero curvature) should indicate that the atmosphere was undergoing compression during that period. A decay curve having concavity upwards (positive curvature) will strongly indicate that the atmosphere was in a contracting phase. A decay curve with downward concavity (negative curvature) may indicate an expanding, a stationary or a contracting atmosphere. This theory, when applied to the orbital decay of the Orbital Debris Radar Calibration Spheres (ODERACS) satellites, indicates that during the period from Day 90 through Day 240 in the year 1994, the atmosphere was very definitely in a compression mode. During this period, ODERACS Sphere 1 faced nearly constant densities while Sphere 6 actually encountered progressively smaller air densities as they descended. The atmospheric scale height as calculated from the orbital data of Spheres 1 and 6 diminished steadily during the same period. It is shown that Spheres 1 and 6 descended faster and slower respectively, than the level of constant air density equal to 5 x 10 kg/m . During a brief period from Day 240 through Day 290, the atmosphere reversed to a strongly expanding mode. Thereafter, the atmosphere reverted back to a compression mode from Day 290 through Day 390, 1994.

Tan, Arjun↗
NASA NTRS1959

Free-Flight Test of a Technique for Inflating an NASA 12-Foot-Diameter Sphere at High Altitudes

A free-flight test has been conducted to check a technique for inflating an NASA 12-foot-diameter inflatable sphere at high altitudes. Flight records indicated that the nose section was successfully separated from the booster rocket, that the sphere was ejected, and that the nose section was jettisoned from the fully inflated sphere. On the basis of preflight and flight records, it is believed that the sphere was fully inflated by the time of peak altitude (239,000 feet). Calculations showed that during descent, jettison of the nose section occurred above an altitude of 150,000 feet. The inflatable sphere was estimated to start to deform during descent at an altitude of about 120,000 feet.

Kehlet, Alan B.↗