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DOE OSTI2022

Designing, synthesizing, and modeling active fluids

We review recent advances in the design, synthesis, and modeling of active fluids. Active fluids have been at the center of many technological innovations and theoretical advances over the past two decades. Research on this new class of fluids has been inspired by the fascinating and remarkably efficient strategies that biological systems employ, leading to the development of biomimetic nano- and micro-machines and swimmers. The review encompasses active fluids on both the nano- and micro-scale. We start with examples of biological active systems before we discuss how experimentalists leverage novel propulsion mechanisms to power nano- and micro-machines. Furthermore, we then examine how the study of these far-from-equilibrium systems has prompted the development of new simulation methods and theoretical models in nonequilibrium physics to account for their mechanical, thermodynamic, and emergent properties. Recent advances in the field have paved the way for the design, synthesis, and modeling of autonomous systems at the nano- and micro-scale and opened the door to the development of soft matter robotics.

36 MATERIALS SCIENCE↗

NASA NTRS1990

The effect of latent heat release on synoptic-to-planetary wave interactions and its implication for satellite observations: Theoretical modeling

The project objectives are to develop process models to investigate the interaction of planetary and synoptic-scale waves including the effects of latent heat release (precipitation), nonlinear dynamics, physical and boundary-layer processes, and large-scale topography; to determine the importance of latent heat release for temporal variability and time-mean behavior of planetary and synoptic-scale waves; to compare the model results with available observations of planetary and synoptic wave variability; and to assess the implications of the results for monitoring precipitation in oceanic-storm tracks by satellite observing systems. Researchers have utilized two different models for this project: a two-level quasi-geostrophic model to study intraseasonal variability, anomalous circulations and the seasonal cycle, and a 10-level, multi-wave primitive equation model to validate the two-level Q-G model and examine effects of convection, surface processes, and spherical geometry. It explicitly resolves several planetary and synoptic waves and includes specific humidity (as a predicted variable), moist convection, and large-scale precipitation. In the past year researchers have concentrated on experiments with the multi-level primitive equation model. The dynamical part of that model is similar to the spectral model used by the National Meteorological Center for medium-range forecasts. The model includes parameterizations of large-scale condensation and moist convection. To test the validity of results regarding the influence of convective precipitation, researchers can use either one of two different convective schemes in the model, a Kuo convective scheme or a modified Arakawa-Schubert scheme which includes downdrafts. By choosing one or the other scheme, they can evaluate the impact of the convective parameterization on the circulation. In the past year researchers performed a variety of initial-value experiments with the primitive-equation model. Using initial conditions typical of climatological winter conditions, they examined the behavior of synoptic and planetary waves growing in moist and dry environments. Surface conditions were representative of a zonally averaged ocean. They found that moist convection associated with baroclinic wave development was confined to the subtropics.

Branscome, Lee E.↗

NASA NTRS2001

A New Analytical Approach to Predict Spacing Selection in Lamellar and Rod Eutectic Systems

In this paper, we reexamine the Jackson and Hunt (JH) theory and relax the assumption of isothermal solid/liquid interface(SLI) used in their treatment. A modification of the term B. in the expression of the solute concentration profile is also proposed. Based on the predictions of this modified theory the traditional definitions of regular and irregular eutectics are discussed. For regular eutectics the new model identifies a range of spacing within the limits defined by the minimum undercooling of the alpha and beta phase. For the irregular Al-Si eutectic system in particular we identified two different spacing selection mechanisnis: a) for a particular growth rate, a nearly isothermal interface can be achieved at a unique minimum spacing lambda(sub I); b) the average spacing in the microstructure (lambda(sub av) > lambda(sub I)) is essentially dictated by the undercooling of the faceted phase. Based on the modified theoretical model a semi-empirical expression has been developed to account for the influence of the temperature gradient. The theoretical calculations have been found to be in good agreement with the published experimental measurements.

Catalina, Adrian V.↗

NASA NTRS2001

MHD Energy Bypass Scramjet Engine

Revolutionary rather than evolutionary changes in propulsion systems are most likely to decrease cost of space transportation and to provide a global range capability. Hypersonic air-breathing propulsion is a revolutionary propulsion system. The performance of scramjet engines can be improved by the AJAX energy management concept. A magneto-hydro-dynamics (MHD) generator controls the flow and extracts flow energy in the engine inlet and a MHD accelerator downstream of the combustor accelerates the nozzle flow. A progress report toward developing the MHD technology is presented herein. Recent theoretical efforts are reviewed and ongoing experimental efforts are discussed. The latter efforts also include an ongoing collaboration between NASA, the US Air Force Research Laboratory, US industry, and Russian scientific organizations. Two of the critical technologies, the ionization of the air and the MHD accelerator, are briefly discussed. Examples of limiting the combustor entrance Mach number to a low supersonic value with a MHD energy bypass scheme are presented, demonstrating an improvement in scramjet performance. The results for a simplified design of an aerospace plane show that the specific impulse of the MHD-bypass system is better than the non-MHD system and typical rocket over a narrow region of flight speeds and design parameters. Equilibrium ionization and non-equilibrium ionization are discussed. The thermodynamic condition of air at the entrance of the engine inlet determines the method of ionization. The required external power for non-equilibrium ionization is computed. There have been many experiments in which electrical power generation has successfully been achieved by magneto-hydrodynamic (MHD) means. However, relatively few experiments have been made to date for the reverse case of achieving gas acceleration by the MHD means. An experiment in a shock tunnel is described in which MHD acceleration is investigated experimentally. MHD has several potential aerospace applications. The first is to improve the performance of hypersonic air-breathing engines for space launch and cruise vehicles. The second is to improve the performance of a high enthalpy wind tunnel. The third is to control a hypersonic vehicle. With such applications in mind, theoretical and experiments are being conducted at the NASA Ames Research Center to develop the MHD technology.

Mehta, Unmeel B.↗

NASA NTRS1989

Atomic oxygen effects on spacecraft materials: The state of the art of our knowledge

In the flight materials exposure data base extensive quantitative data is available from limited exposures in a narrow range of orbital environments. More data is needed in a wider range of environments as well as longer exposure times. Synergistic effects with other environmental factors; polar orbit and higher altitude environments; and real time materials degradation data is needed to understand degradation kinetics and mechanism. Almost no laboratory data exists from high fidelity simulations of the LEO environment. Simulation and test system are under development, and the data base is scanty. Theoretical understanding of hyperthermal atom surface reactions in the LEO environment is not good enough to support development of reliable accelerated test methods. The laser sustained discharge, atom beam sources are the most promising high fidelity simulation-test systems at this time.

Koontz, Steven L.↗

DOE OSTI2022

Theoretical and calculable dependent variables and their covariance in nuclear data libraries [Slides]

This presentation begins by defining observables, including theoretical observable, calculable observable, and measured observable. It also provides definitions and examples of experimental effects. Additionally, uncertainty in evaluated libraries and a metric to probe evaluated uncertainty is presented. In conclusion, being related to theoretical quantities such as resonance parameters, the uncertainty in ENDF libraries (e.g., ENDF/B-VIII.0) can be overestimated because it is usually evaluated under the guidance of experimental uncertainty: lim Δσexp.corr.→0 Δσ = Δσ theoretical model . The presentation states that a clear distinction of the uncertainty between nuclear theoretical models and experimental corrections should be revisited and this is important since (e.g., transport) simulations need theoretical quantities convoluted with specific operational parameters and material configurations. It also states that strong coupling between uncertainty quantification methodologies and optimization procedures exists, and it is necessary to develop methodologies to obtain uncertainty on theoretical models from physical and mathematical constraints.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2018

Theoretical Studies of Elementary Hydrocarbon Species and Their Reactions

The research program supported by this DOE grant carried out both methodological development and computational applications of first-principles theoretical chemistry based on quantum mechanical wavefunctions, as directed toward understanding and harnessing the fundamental chemical physics of combustion. To build and refine the world’s database of thermochemistry, spectroscopy, and chemical kinetics, predictive and definitive computational methods are needed that push the envelope of modern electronic structure theory. The application of such methods has been made to gain comprehensive knowledge of the paradigmatic reaction networks by which the n- and i-propyl, t-butyl, and n-butyl radicals are oxidized by O 2 . Numerous ROO and QOOH intermediates in these R + O 2 reaction systems have been characterized along with the interconnecting isomerization transition states and the barriers leading to fragmentation. Other combustion-related intermediates have also been studied, including methylsulfinyl radical, cyclobutylidene, and radicals derived from acetaldehyde and vinyl alcohol. Theoretical advances have been achieved and made available to the scientific community by implementation into PSI4, an open-source electronic structure computer package emphasizing automation, advanced libraries, and interoperability. We have pursued the development of universal explicitly correlated methods applicable to general electronic wavefunctions, as well as a framework that allows multideterminant reference functions to be expressed as a single determinant from quasiparticle operators. Finally, a rigorous analytical tool for correlated wavefunctions has been created to elucidate dispersion interactions, which play essential roles in many areas of chemistry, but whose effects are often masked and enigmatic. Our research decomposes and analyzes the coupled-cluster electron correlation energy in molecular systems as a function of interelectronic distance. Concepts are emerging that can be used to explain the influence of dispersion on the thermochemistry of large hydrocarbons, including fuels important to combustion technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Air-Coupled Nondestructive Evaluation Dissected

This work develops a two-dimensional theoretical model to simulate the behavior of a fully non-contact air-coupled nondestructive evaluation system for a thin isotropic plate. The model is divided into transmission, guided wave propagation and reception phase. The validation of the complete model was carried out by modeling the same system by means of finite element method using a Multiphysics software. In addition, the dependency of the generated Lamb waves on different transmitter’s parameters and incidence angle is thoroughly investigated. The results of the acoustic pressure excited by the transducer, the out-of-plane velocity amplitudes for the generated first antisymmetric Lamb wave mode, and the radiated pressure from the plate caused by the leaky Lamb wavefield were all compared between the two models and a reasonable degree of similarity was found.

42 ENGINEERING↗

DOE OSTI2025

Dehumidification energy storage using a stratified liquid desiccant tank

Liquid desiccants can play an important role in reducing dehumidification energy requirements in the built environment. Because they are in a liquid state, the desiccant can be easily stored and then used to dehumidify buildings during peak energy consumption periods. By maintaining stratification between concentrated and diluted desiccant solutions, a single tank can be used to store liquid desiccant for energy storage purposes. Using a stratified tank instead of separate tanks for dilute and concentrated solutions will reduce storage costs and increase energy storage densities for liquid desiccant systems. This paper describes the experimental validation and one-dimensional modeling of a stratified liquid desiccant tank. The stratified tank prototype developed achieved 80 % of the theoretical energy storage density based on an imposed desiccant concentration change. Here, the stratified tank model was able to reasonably reproduce the experimental results. Using this model, the impact of varying operational conditions on the energy density of the stratified liquid desiccant energy storage was evaluated. Depending on the operating conditions, stratified liquid desiccant energy storage using aqueous LiCl up to 40 wt% can achieve energy storage densities in excess of 330 kWh/m 3 .

25 ENERGY STORAGE↗

DOE OSTI2017

A fast integrated mobility spectrometer for rapid measurement of sub-micrometer aerosol size distribution, Part I: Design and model evaluation

This study discusses, a fast integrated mobility spectrometer (FIMS) was previously developed to characterize submicron aerosol size distributions at a frequency of 1 Hz and with high size resolution and counting statistics. However, the dynamic size range of the FIMS was limited to one decade in particle electrical mobility. It was proposed that the FIMS dynamic size range can be greatly increased by using a spatially varying electric field. This electric field creates regions with drastically different field strengths in the separator, such that particles of a wide diameter range can be simultaneously classified and subsequently measured. A FIMS incorporating this spatially varying electric field is developed. This paper describes the theoretical frame work and numerical simulations of the FIMS with extended dynamic size range, including the spatially varying electric field, particle trajectories, activation of separated particles in the condenser, and the transfer function, transmission efficiency, and mobility resolution. The influences of the particle Brownian motion on FIMS transfer function and mobility resolution are examined. The simulation results indicate that the FIMS incorporating the spatially varying electric field is capable of measuring aerosol size distribution from 8 to 600 nm with high time resolution. As a result, the experimental characterization of the FIMS is presented in an accompanying paper.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2017

Characterization of reactive CaCO 3 crystallization in a fluidized bed reactor as a central process of direct air capture

A laboratory-scale, fluidized-bed pellet reactor (BPR) was used to investigate a CaCO 3 crystallization process for the recovery of CO 2 in a Direct Air Capture (DAC) process. The BPR performance was validated against data from a pilot-scale unit. Subsequently, the pellet growth under process-relevant conditions was studied over a period of 144 h. The experimental results with the BPR, containing a bed of pellets sized between 0.65 and 0.84 mm, have shown that a calcium retention of 80% can be achieved at a fluidization velocity of 60 m h -1 and a calcium loading rate of 3 mol h -1 . This result is consistent with calcium retention observed at pilot scale operation and hence, results from the BPR are considered representative for the pilot scale unit. Starting with a bed of pellets sized between 0.15 and 0.5 mm, the average pellet growth rate, G, at the reactor bottom increased from 8.1E-10 to 11E–10 m s -1 at the onset and decreased to 4.9E–10 m s -1 over the course of a 144 h test. The calcium retention over the course the test showed the same trend (initial increase and final decrease) as the pellet growth rate. A theoretical bed growth model was developed and validated against data from the pilot scale and benchtop pellet reactors. The model was used to calculate the bed porosity and total pellet surface area in each control volume. Lastly, the pellet surface area growth at the bottom of the reactor reproduced the pellet growth and retention data trends.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

A greedy Galerkin method to efficiently select sensors for linear dynamical systems

A key challenge in inverse problems is the selection of sensors to gather the most effective data. In this paper, we consider the problem of inferring the initial condition to a linear dynamical system and develop an efficient control-theoretical approach for greedily selecting sensors. Our method employs a Galerkin projection to reduce the size of the inverse problem, resulting in a computationally efficient algorithm for sensor selection. As a byproduct of our algorithm, we obtain a preconditioner for the inverse problem that enables the rapid recovery of the initial condition. Here, we analyze the theoretical performance of our greedy sensor selection algorithm as well as the performance of the associated preconditioner. Finally, we verify our theoretical results on various inverse problems involving partial differential equations.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2021

Mechanistic Study of the Li–Air Battery with a Co 3 O 4 Cathode and Dimethyl Sulfoxide Electrolyte

The lithium–air battery, a powerful competitor to replace the traditional lithium-ion battery, has attracted increasing attention due to its extremely high theoretical energy density. However, its development is limited by the cathode and electrolyte properties, which should include high stability, conductivity, and electrocatalytic properties in oxygen-rich environments. Here, we employ a systematic first-principles study of Li–O 2 discharge and charge reactions on the Co 3 O 4 -based cathode with the assistance of dimethyl sulfoxide (DMSO) electrolyte. The structure, stability, and electronic properties of different surface reconstructions of the Co 3 O 4 (100) facet are investigated. In addition, the mechanisms and thermodynamic overpotentials of multi-step reactions between Li + /e – and O 2 are provided, where lithium suboxide products (Li 2 O 2 or Li 3 O 2 ) are formed on the different Co 3 O 4 (100) terminations. The solvation shell of Li + components in explicit DMSO solvent is investigated through ab initio molecular dynamics simulations. In general, we find that the Co 3 O 4 (100)-O (oxidized) surface is the most stable one under standard conditions, and the stable Li + solvation structure is found in a tetrahedral Li(DMSO) 4 + shell in the DMSO-based electrolyte. Moreover, in the system of the Co 3 O 4 (100)-O cathode and DMSO electrolyte, the solution model pathway is energetically favorable for the Li–O 2 discharge reaction. It provides a low constant overpotential of 0.17 V during a long-term discharging process, thus causing the final toroid Li 2 O 2 formation on the cathode. During the charging process, an overpotential of 0.36 V is required to rapidly decompose Li 2 O 2 .

25 ENERGY STORAGE↗

DOE OSTI2021

Simultaneous Decomposition and Dewetting of Nanoscale Alloys: A Comparison of Experiment and Theory

In this work, we consider the coupled process of phase separation and dewetting of metal alloys of nanoscale thickness deposited on solid substrates. The experiments involve applying nanosecond laser pulses that melt the Ag40Ni60 alloy films in two setups: either on thin supporting membranes or on bulk substrates. These two setups allow for extracting both temporal and spatial scales on which the considered processes occur. The theoretical model involves a longwave version of the Cahn–Hilliard formulation used to describe spinodal decomposition, coupled with an asymptotically consistent longwave-based description of dewetting that occurs due to destabilizing interactions between the alloy and the substrate, modeled using the disjoining pressure approach. Careful modeling, combined with linear stability analysis and fully nonlinear simulations, leads to results consistent with the experiments. In particular, we find that the two instability mechanisms occur concurrently, with the phase separation occurring faster and on shorter temporal scales. The modeling results show a strong influence of the temperature dependence of relevant material properties, implying that such a dependence is crucial for the understanding of the experimental findings. The agreement between theory and experiment suggests the utility of the proposed theoretical approach in helping to develop further experiments directed toward formation of metallic alloy nanoparticles of desired properties.

36 MATERIALS SCIENCE↗

DOE OSTI2017

New Description of Evolution of Magnetic Phases in Artificial Honeycomb Lattice

Artificial magnetic honeycomb lattice provides a two-dimensional archetypal system to explore novel phenomena of geometrically frustrated magnets. According to theoretical reports, an artificial magnetic honeycomb lattice is expected to exhibit several phase transitions to unique magnetic states as a function of reducing temperature. Experimental investigations of permalloy artificial honeycomb lattice of connected ultra-small elements, ≃ 12 nm, reveal a more complicated behavior. First, upon cooling the sample to intermediate temperature, T≃ 175 K, the system manifests a non-unique state where the long range order co-exists with short-range magnetic charge order and weak spin ice state. Second, at much lower temperature, T≃ 6 K, the long-range spin solid state exhibits a re-entrant behavior. Both observations are in direct contrast to the present understanding of this system. New theoretical approaches are needed to develop a comprehensive formulation of this two dimensional magnet.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2024

Acid–base concentration swing for direct air capture of carbon dioxide

This work demonstrates the first experimental evidence of the acid–base concentration swing (ABCS) for direct air capture of CO 2 . This process is based on the effect that concentrating particular acid–base chemical reactants will strongly acidify solution, through Le Chatelier's principle, and result in outgassing absorbed CO 2 . After collecting the outgassed CO 2 , diluting the solution will result in a reversal of the acid–base reaction, basifying the solution and allowing for atmospheric CO 2 absorption. The experimental study examines a system that includes sodium cation as the alkalinity carrier, boric acid, and a polyol complexing agent that reversibly reacts with boric acid to strongly acidify solution upon concentration. Though the tested experimental system faces absorption rate and water capacity limitations, the ABCS process described here provides a basis for further process optimization. A generalized theoretical ABCS reaction framework is developed and different reaction orders and conditions are studied mathematically. Higher order reactions yield favorable cycle output results, reaching volumetric cycle capacity above 50 mM for third-order and 80 mM for fourth-order reactions. Optimal equilibrium constants are determined in order to guide alternative chemical searches and synthetic chemistry design targets. There is a substantial energetic benefit for reaction orders above the first, with second- and third-order ABCS cycles exhibiting a thermodynamic minimum work for the concentrating and outgassing steps around 150 kJ per mole of CO 2 . A significant advantage of the ABCS is that it can be driven through well-developed and widely-deployed desalination technologies, such as reverse osmosis, with opportunities for energy recovery when recombining the concentrated and diluted streams, and extraction can occur directly from the liquid phase upon vacuum application.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2018

Understanding the effects of symmetric salt on the structure of a planar dipolar polymer brush

The effects of added salt on a planar dipolar polymer brush immersed in a polar solvent are studied using a field theoretic approach. The field theory developed in this work provides a unified framework for capturing effects of the inhomogeneous dielectric function, translational entropy of ions, crowding due to finite sized ions, ionic size asymmetry, and ion solvation. In this paper, we use the theory to study the effects of ion sizes, their concentration, and ion-solvation on the polymer segment density profiles of a dipolar brush immersed in a solution containing symmetric salt ions. The interplay of crowding effects, translational entropy, and ion solvation is shown to exhibit either an increase or decrease in the brush height. Translational entropy and crowding effects due to finite sizes of the ions tend to cause expansion of the brush as well as uniform distribution of the ions. By contrast, ion-solvation effects, which tend to be stronger for smaller ions, are shown to cause shrinkage of the brush and inhomogeneous distribution of the ions.

36 MATERIALS SCIENCE↗

DOE OSTI2020

An in situ shearing x-ray measurement system for exploring structures and dynamics at the solid–liquid interface

Revealing interfacial structure and dynamics has been one of the essential thematic topics in material science and condensed matter physics. Synchrotron-based x-ray scattering techniques can deliver unique and insightful probing of interfacial structures and dynamics, in particular, in reflection geometries with higher surface and interfacial sensitivity than transmission geometries. We demonstrate the design and implementation of an in situ shearing x-ray measurement system, equipped with both inline parallel-plate and cone-and-plate shearing setups and operated at the advanced photon source at Argonne National Laboratory, to investigate the structures and dynamics of end-tethered polymers at the solid-liquid interface. With a precise lifting motor, a micrometer-scale gap can be produced by aligning two surfaces of a rotating upper shaft and a lower sample substrate. A torsional shear flow forms in the gap and applies tangential shear forces on the sample surface. The technical combination with nanoscale rheology and the utilization of in situ x-ray scattering allow us to gain fundamental insights into the complex dynamics in soft interfaces under shearing. In this work, we demonstrate the technical scope and experimental capability of the in situ shearing x-ray system through the measurements of charged polymers at both flat and curved interfaces upon shearing. Furthermore, through the in situ shearing x-ray scattering experiments integrated with theoretical simulations, we aim to develop a detailed understanding of the short-range molecular structure and mesoscale ionic aggregate morphology, as well as ion transport and dynamics in soft interfaces, thereby providing fundamental insight into a long-standing challenge in ionic polymer brushes with a significant technological impact.

36 MATERIALS SCIENCE↗