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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Measurement of charged-particle event shape variables in s = 7 TeV proton-proton interactions with the ATLAS detector

CERN-LHC. Measurements of the event shape variables Transverse Thrust, Transverse Thrust Minor and Transverse Sphericity in proton-proton collisions at a centre-of-mass energy of 7 TeV. Events with at least six final state charged particles are selected from a data sample collected in April 2010 with a minimum prescale factor for the minimum-bias trigger. In addition to the event shape distributions, data on the evolution of their mean values with charged particle multiplicity and scalar PT sum are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Particle size and shape distributions of hammer milled pine

Particle size and shape distributions impact particle heating rates and diffusion of volatized gases out of particles during fast pyrolysis conversion, and consequently must be modeled accurately in order for computational pyrolysis models to produce reliable results for bulk solid materials. For this milestone, lodge pole pine chips were ground using a Thomas-Wiley #4 mill using two screen sizes in order to produce two representative materials that are suitable for fast pyrolysis. For the first material, a 6 mm screen was employed in the mill and for the second material, a 3 mm screen was employed in the mill. Both materials were subjected to RoTap sieve analysis, and the distributions of the particle sizes and shapes were determined using digital image analysis. The results of the physical analysis will be fed into computational pyrolysis simulations to create models of materials with realistic particle size and shape distributions. This milestone was met on schedule.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Hopper flows of mixtures of spherical and rod‐like particles via the multisphere method

Abstract The discharge of granular media from hoppers plays a vital role in many solids handling operations. The dynamic flow of poly‐disperse nonspherical particles differs markedly from mono‐disperse spheres and highlights the need to rigorously account for particle shape effects. The multisphere discrete element method (MS‐DEM) was utilized here to examine the bulk packing fraction, discharge rate, collisional stress tensor, and order parameter of a bi‐disperse sphere‐rod mixture evacuating a hopper. A modified form of the Myers and Sellers correlation with variable shape factor is capable of replicating the MS‐DEM discharge data. The collisional stress tensor is observed to be highly symmetric for mono‐disperse spheres but becomes asymmetric when rod‐like particles are introduced. The order parameter within the hopper increases significantly during discharge and the rod‐like particles undergo shear induced alignment with their long dimensions orthogonal to the outflow plane.

Lattanzi, Aaron M.↗
DOE OSTI2020

Measurement of flow properties coupled to experimental and numerical analyses of dense, granular flows for solar thermal energy storage

Granular flows of sintered bauxite proppants were researched along an inclined plane for solar thermal energy storage applications. Granular flow properties needed to drive numeric granular models were measured for improved numerical model predictions for Carbobead CP 50/140, 40/100, and 30/60 particles. Particle shape and size distributions were determined by coupling optical microscopy to an in-house image processing algorithm. The impulse excitation technique was used to measure elastic and shear moduli, and compute Poisson’s ratio. The coefficient of static sliding friction was measured using the slip-stick method, and the static rolling friction was determined from measured shear on particles positioned between two hot-pressed plates. The coefficient of restitution was measured by dropping particles on a surface and determining the kinetic energy before and after impact with the surface using high resolution particle tracking velocimetry. Particle size did not significantly impact the coefficients of restitution and static rolling friction, however, particle shape distribution resulted in a large variation in measurements. An inclined flow experiment was performed to characterize granular flows of Carbobead CP 30/60 particles using particle image velocimetry. Numerical models of the experiment using discrete element method were generated with the measured mechanical properties as inputs for comparison with experimental results. A constant directional torque rolling friction model best predicted bulk granular flow behavior. Furthermore, good agreement between the model and experiment was achieved at ambient, steady state conditions, with average velocity differences <10%.

14 SOLAR ENERGY↗
DOE OSTI2022

Computational study of inertial migration of prolate particles in a straight rectangular channel

Inertial migration of spherical particles has been investigated extensively using experiments, theory, and computational modeling. Yet, a systematic investigation of the effect of particle shape on inertial migration is still lacking. Herein, we numerically mapped the migration dynamics of a prolate particle in a straight rectangular microchannel using smoothed particle hydrodynamics at moderate Reynolds number flows. After validation, we applied our model to 2:1 and 3:1 shape aspect ratio particles at multiple confinement ratios. Their effects on the final focusing position, rotational behavior, and transitional dynamics were studied. In addition to the commonly reported tumbling motion, for the first time, we identified a new logrolling behavior of a prolate ellipsoidal particle in the confined channel. This new behavior occurs when the confinement ratio is above an approximate threshold value of K = 0.72. Our microfluidic experiments using cell aggregates with similar shape aspect ratio and confinement ratio confirmed this new predicted logrolling motion. In this study, we also found that the same particle can undergo different rotational modes, including kayaking behavior, depending on its initial cross-sectional position and orientation. Furthermore, we examined the migration speed, angular velocity, and rotation period as well as their dependence on both particle shape aspect ratio and confinement ratio. Our findings are especially relevant to the applications where particle shape and alignment are used for sorting and analysis, such as the use of barcoded particles for biochemical assays through optical reading, or the shape-based enrichment of microalgae, bacteria, and chromosomes.

42 ENGINEERING↗
DOE OSTI2022

Voronoi cell analysis: The shapes of particle systems

Many physical systems can be studied as collections of particles embedded in space, often evolving in time. Natural questions arise concerning how to characterize these arrangements—are they ordered or disordered? If they are ordered, how are they ordered and what kinds of defects do they possess? Voronoi tessellations, originally introduced to study problems in pure mathematics, have become a powerful and versatile tool for analyzing countless problems in pure and applied physics. Here we explain the basics of Voronoi tessellations and the shapes that they produce and describe how they can be used to characterize many physical systems.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Proton beam shaped by “particle lens” formed by laser-driven hot electrons

Two-dimensional tailoring of a proton beam is realized by a “particle lens” in our experiment. A large quantity of electrons, generated by an intense femtosecond laser irradiating a polymer target, produces an electric field strong enough to change the trajectory and distribution of energetic protons flying through the electron area. The experiment shows that a strip pattern of the proton beam appears when hot electrons initially converge inside the plastic plate. Then the shape of the proton beam changes to a “fountain-like” pattern when these hot electrons diffuse after propagating a distance.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Adhesion and aerodynamic forces for the resuspension of non-spherical particles in outdoor environments

Particles deposited on an outdoor surface can be resuspended by wind gusts, become airborne, and be inhaled if small enough. If toxic or infectious, these particles may be dangerous for the populace health. It is therefore important to determine under which weather conditions a deposit of particle could be resuspended to implement the best response actions and plan clean-up. To this scope, one needs to consider the competing forces acting on the particle keeping it attached to the surface (gravity and adhesion) or trying to remove it (aerodynamic forces, i.e., lift and drag). Here, this article reviews the current understanding of the aforementioned forces for colloidal spherical particles and extends the existing theories to rod-shaped particles, representative for instance of Bacillus spores. In particular, for the adhesion force, the Derjaguin approximation was used and the adhesion force was computed from the radii of curvature of the particle and the surface at the point of closest approach. For the aerodynamic forces, we re-derived the equations for the drag and lift forces accounting for the shape of the particle. Both smooth and rough surfaces will be discussed, the former as idealized cases, the latter as more representative of real outdoor surfaces.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Photoluminescence properties of AlN-doped BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphors

Highlights: ► Ideal hexagonal shape particle size in 5 μm and 2.5–3 μm in thickness are obtained. ► The growth mechanism is studied by a computer simulation. ► The influence of introduced AlN on the sites of Eu{sup 2+} and photoluminescence properties was investigated. - Abstract: The AlN-doped BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphors were synthesized by conventional solid-state reaction. Powder X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectrum (PL) were used for characterization. The growth mechanism was carried out by computer simulation with CASTEP application, and revealed that an ideal hexagonal shape, particle size in 5 μm and 2.5–3 μm in thickness, could be obtained by AlN doping. Additionally, due to the low electronegativity of N{sup 3−}, the AlN-doped sample showed 35% increase in PL intensity and improvement of thermal stability. These fine particle size and better photoluminescence properties are expected to be applicable to industrial production of BaMgAl{sub 10}O{sub 17}:Eu{sup 2+} phosphors.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Small-angle X-ray and neutron scattering demonstrates that cell-free expression produces properly formed disc-shaped nanolipoprotein particles

Nanolipoprotein particles (NLPs), composed of membrane scaffold proteins and lipids, have been used to support membrane proteins in a native-like bilayer environment for biochemical and structural studies. Traditionally, these NLPs have been prepared by the controlled removal of detergent from a detergent-solubilized protein-lipid mixture. Recently, an alternative method has been developed using direct cell-free expression of the membrane scaffold protein in the presence of preformed lipid vesicles, which spontaneously produces NLPs without the need for detergent at any stage. Using SANS/SAXS, we show here that NLPs produced by this cell-free expression method are structurally indistinguishable from those produced using detergent removal methodologies. This further supports the utility of single step cell-free methods for the production of lipid binding proteins. Lastly, in addition, detailed structural information describing these NLPs can be obtained by fitting a capped core-shell cylinder type model to all SANS/SAXS data simultaneously.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Synergistic Effect of Nitrogen and Refractory Material on TiN Formation and Equiaxed Grain Structure of Ferritic Stainless Steel

The effect of nitrogen content on the formation of an equiaxed solidification structure of Fe-16Cr steel was investigated. Moreover, two different kinds of refractory materials, i.e., alumina and magnesia, were employed to control the type of oxide inclusion. The characteristics of TiN(-oxide) inclusions were quantitatively analyzed in both molten steel and solidified samples. When the melting was carried out in the alumina refractory, the grain size continuously decreased with increasing nitrogen content. However, a minimum grain size was observed at a specific nitrogen content (approx. 150 ppm) when the steel was melted in the magnesia refractory. Most of the single TiN particles had a cuboidal shape and fine irregularly shaped particles were located along the grain boundary due to the microsegregation of Ti at the grain boundary during solidification. The type of TiN-oxide hybrid inclusion was strongly affected by the refractory material where Al{sub 2}O{sub 3}-TiN and MgAl{sub 2}O{sub 4}-TiN hybrid-type inclusions were obtained in the alumina and magnesia refractory experiments, respectively. The formation of oxide inclusions was well predicted by thermochemical computations and it was commonly found that oxide particles were initially formed, followed by the nucleation and growth of TiN. When the nitrogen content increased, the number density of TiN linearly increased in the alumina refractory experiments. However, the number of TiN exhibits a maximum at about [N] = 150 ppm, at which a minimum grain size was obtained in the magnesia refractory experiments. Therefore, the larger the number density of TiN, the smaller the primary grain size after solidification. The number density of TiN in the steel melted in the magnesia refractory was greater than that in the steel melted in the alumina refractory at given Ti and N contents, which was due to the lower planar lattice disregistry of MgAl{sub 2}O{sub 4}-TiN interface rather than that of Al{sub 2}O{sub 3}-TiN interface. When ∆T{sub TiN} (= difference between the TiN precipitation temperature and the liquidus of the steel) was 20 K to 40 K, the number density of effective TiN was maximized and thus, the grain size was minimized after solidification. Finally, although most of the TiN particles were smaller than 1 μm in the molten steel samples irrespective of the nitrogen content, TiN particles larger than 10 μm were observed in the solidified samples when the nitrogen content was greater than 150 ppm. The growth of TiN particles during melting and solidification was well predicted by the combinatorial simulation of the ‘Ostwald ripening model’ based on the Lifshitz–Slyozov–Wagner theory in conjunction with the ‘Diffusion controlled model’ using Ohnaka’s microsegregation equation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Discrete element modeling of deformable pinewood chips in cyclic loading test

The design of efficient lignocellulosic biomass feedstock systems is challenging, as current laboratory characterization and design methods were developed primarily for fine powders with relatively low compressibility. Here, the discrete element method (DEM) is gaining prominence as an alternative method for modeling the bulk flow and transport of particulate materials in hoppers and feeders. However, prior DEM simulations investigating the flow of wood chips modeled the particles as simple rigid geometries such as spheres, rods or blocks, and neglected the effects of particle deformability and irregular shapes. As a consequence, those simplified DEM models may not provide enough key diagnosis to help improve the design of biomass feeding and handling equipment. This work presents a bonded-sphere DEM approach for characterizing the mechanical behavior of bulk flexible, deformable pinewood chips in a cyclic stress loading test. Clustered spheres that can bend and twist via elastic bonds are used to model irregular-shape particles in real pinewood chip samples. An axial compression tester, which contains 0.06 million bonded-sphere particles (1.35 million spheres) in a quarter cylinder, is simulated with a domain size similar to the experiments. With careful calibration, the simulations have delivered the bulk densities and the bulk moduli of elasticity that are in good agreement with those measured in the corresponding experiments. However, it is also been found challenging for the present DEM model to accurately predict the overall stress-strain behavior of bulk pinewood chips, especially the large sustained plastic deformation during unloading. Additional numerical tests have shown that the adjustment in certain contact parameters (e.g. bond stiffness) can lead to profound solution improvement, but meanwhile will induce extra challenges such as increased computing time. Future work will include an elasto-plastic particle bond model to enhance the simulation fidelity.

42 ENGINEERING↗