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Results for “Constrained transport”

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 OSTI2020

Persistence of soil organic carbon caused by functional complexity

Soil organic carbon management has the potential to aid climate change mitigation through drawdown of atmospheric carbon dioxide. To be effective, such management must account for processes influencing carbon storage and re-emission at different space and time scales. Achieving this requires a conceptual advance in our understanding to link carbon dynamics from the scales at which processes occur to the scales at which decisions are made. Here, we propose that soil carbon persistence can be understood through the lens of decomposers as a result of functional complexity derived from the interplay between spatial and temporal variation of molecular diversity and composition. For example, co-location alone can determine whether a molecule is decomposed, with rapid changes in moisture leading to transport of organic matter and constraining the fitness of the microbial community, while greater molecular diversity may increase the metabolic demand of, and thus potentially limit, decomposition. This conceptual shift accounts for emergent behaviour of the microbial community and would enable soil carbon changes to be predicted without invoking recalcitrant carbon forms that have not been observed experimentally. Finally, functional complexity as a driver of soil carbon persistence suggests soil management should be based on constant care rather than one-time action to lock away carbon in soils.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Collisionless cooling of perpendicular electron temperature in the thermal quench of a magnetized plasma

Thermal quench of a nearly collisionless plasma against an isolated cooling boundary or region is an undesirable off-normal event in magnetic fusion experiments, but an ubiquitous process of cosmological importance in astrophysical plasmas. Parallel transport theory of ambipolar-constrained tail electron loss is known to predict rapid cooling of the parallel electron temperature $T_{e\Vert}$ although $T_{e\Vert}$ is difficult to diagnose in actual experiments. Instead direct experimental measurements can readily track the perpendicular electron temperature $T_{e\bot}$ via electron cyclotron emission. The physics underlying the observed fast drop in $T_{e\bot}$ requires a resolution. Here two collisionless mechanisms, dilutional cooling by infalling cold electrons and wave-particle interaction by two families of whistler instabilities, are shown to enable fast $T_{e\bot}$ cooling that closely tracks the mostly collisionless crash of $T_{e\Vert}$. These findings motivate both experimental validation and reexamination of a broad class of plasma cooling problems in laboratory, space, and astrophysical settings.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Characterizing radial flow fluctuations in relativistic heavy-ion collisions at top RHIC and LHC energies

This study presents a systematic investigation of the transverse-momentum differential radial flow fluctuations observable 𝑣 0 ⁡ (𝑝 𝑇 ) in relativistic heavy-ion collisions at top Relativistic Heavy Ion Collider ($\sqrt{s_{NN}}$ = 200 GeV) and Large Hadron Collider ($\sqrt{s_{NN}}$ = 2.76 and 5.02 TeV) energies. Using a multistage hydrodynamic model, this study assesses the sensitivity of 𝑣 0 ⁡(𝑝 𝑇 ) to a wide range of physical effects, including bulk and shear viscosities, off-equilibrium corrections at particlization, the presence of a hadronic afterburner, and the nucleon size in the initial conditions. By employing complementary rescaling strategies, this study demonstrates how different physical effects leave distinct imprints on the shape of 𝑣 0 ⁡(𝑝 𝑇 ). A combined double-rescaling of 𝑣 0 ⁡(𝑝 𝑇 )/𝑣 0 versus 𝑝 𝑇 /⟨𝑝 𝑇 ⟩ reveals a universality across a wide range of energies and model assumptions in the low-𝑝 𝑇 regime, a robust signature of collective behavior. This allows us to disentangle the universal dynamics of the bulk medium from model-specific features that emerge at higher 𝑝 𝑇 . These results establish 𝑣 0⁡ (𝑝 𝑇 ) as a powerful and complementary observable for constraining quark-gluon plasma transport properties and initial-state granularity, offering a unique probe of the created QCD medium.

Du, Lipei [University of California, Berkeley, CA ↗
DOE OSTI2021

Characterizing the Influence of Organic Polymers on the Specific Reactivity of Particulate Remedial Amendments

Commercially available particulate amendments demonstrate high reactivity for effective treatment of water soluble organic and inorganic contaminants in laboratory studies; however, transport of these particles is constrained in the subsurface. In many field applications, particulate amendments are mixed with organic polymers to enhance mobility for direct push applications or stabilize suspensions for high mass loadings. As such, the interactions between particulate amendments, organic polymers and contaminant species need to be systematically investigated to properly understand mechanistic processes that facilitate predictive performance metrics for specific applications in situ . In this study, batch experiments were conducted to quantify the effects of organic polymers (xanthan gum, guar gum, and sodium alginate), polymer concentration (800 and 4,000 mg/L), and aging (up to 28 days) on chromate treatment rate and capacity by two classes of amendments: reductants [granular zero-valent iron (gZVI), micron-ZVI (mZVI), sulfur modified iron (SMI)], and an adsorbent (bismuth sub-nitrate). When particulate amendments were suspended in polymer solutions, reductants retained between 84–100% of the amendment treatment capacity. Conversely, the adsorbent maintained 63–97% relative treatment capacity of the no-polymer control. Polymer solutions had a more pronounced impact on the rate of chromate removal; first order rates of chemical reduction decreased by as much as 70% and adsorption by up to 81% relative to the no-polymer controls. Polymer–amendment aging experiments also showed decreased Cr(VI) treatment capacity; reductants decreased by as much as 24% and adsorption decreased by as much as 44% after 28 days of incubation. While polymer suspensions are needed to aid the injection of particulate amendments into the subsurface, the results from this study indicate potential losses of treatment capacity and a decrease in the rate of remedial performance due to the physical and chemical interactions between polymer suspensions and reactive particulate amendments. Simple batch systems provide baseline characterization of tripartite interactions for the removal of Cr(VI). Additional work is needed to quantify the full impact of polymers on remedial outcomes under site relevant conditions at field scale.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1980

Integrated application of active controls (IAAC) technology to an advanced subsonic transport project. Initial ACT configuration design study

The initial ACT configuration design task of the integrated application of active controls (IAAC) technology project within the Energy Efficient Transport Program is summarized. A constrained application of active controls technology (ACT) resulted in significant improvements over a conventional baseline configuration previously established. The configuration uses the same levels of technology, takeoff gross weight, payload, and design requirements/objectives as the baseline, except for flying qualities, flutter, and ACT. The baseline wing is moved forward 1.68 m. The configuration incorporates pitch-augmented stability (which enabled an approximately 10% aft shift in cruise center of gravity and a 45% reduction in horizontal tail size), lateral/directional-augmented stability, an angle of attack limiter, wing load alleviation, and flutter mode control. This resulted in a 930 kg reduction in airplane operating empty weight and a 3.6% improvement in cruise efficiency, yielding a 13% range increase. Adjusted to the 3590 km baseline mission range, this amounts to 6% block fuel reduction and a 15.7% higher incremental return on investment, using 1978 dollars and fuel cost.

Source record↗
NASA NTRS2002

Aeronautical Communications Research and Development Needs for Future Air Traffic Management Applications

Continuing growth in regional and global air travel has resulted in increasing traffic congestion in the air and on the ground. In spite of occasional temporary downturns due to economic recessions and catastrophic events, average growth rates of air travel have remained high since the 1960s. The resulting congestion, which constrains expansion of the air transportation industry, inflicts schedule delays and decreases overall system efficiency, creating a pressing need to develop more efficient methods of air traffic management (ATM). New ATM techniques, procedures, air space automation methods, and decision support tools are being researched and developed for deployment in time frames stretching from the next few years to the year 2020 and beyond. As these methods become more advanced and increase in complexity, the requirements for information generation, sharing and transfer among the relevant entities in the ATM system increase dramatically. However, current aeronautical communications systems will be inadequate to meet the future information transfer demands created by these advanced ATM systems. Therefore, the NASA Glenn Research Center is undertaking research programs to develop communication, methods and key technologies that can meet these future requirements. As part of this process, studies, workshops, testing and experimentation, and research and analysis have established a number of research and technology development needs. The purpose of this paper is to outline the critical research and technology needs that have been identified in these activities, and explain how these needs have been determined.

Kerczewski, Robert J.↗
NASA NTRS2009

Ultraviolet and Radio Emission from the Northern Middle Lobe of Centaurus A

We present deep GALEX ultraviolet (135 - 280 nm) images of the Northern Middle Lobe (NML) of the nearby radio galaxy Centaurus A. We find that the ultraviolet emission appears to have a complex interaction with soft X-ray, H-alpha emission, and radio emission, which should help constrain various models of energy transport in the NML. We also present new 90cm VLA images of the NML. The radio morphology at this wavelength is indicative of a more complex system than either a straightforward flaring jet (Morganti et al. 1999) or a bubble with trailing stem (Saxton et al. 2001). New limits are placed on the lack of radio emission from any corresponding southern counterpart to the NML.

Neff, Susan↗
NASA NTRS2021

Intercomparison of the representations of the atmospheric chemistry of pre-industrial methane and ozone in earth system and other global chemistry-transport models

An intercomparison has been set up to study the representation of the atmospheric chemistry of the pre-industrial troposphere in earth system and other global tropospheric chemistry-transport models. The intercomparison employed a constrained box model and utilised tropospheric trace gas composition data for the pre-industrial times at ninety mid-latitude surface locations. Incremental additions of four organic compounds: methane, ethane, acetone and propane, were used to perturb the constrained box model and generate responses in hydroxyl radicals and tropospheric ozone at each location and with each chemical mechanism. Although the responses agreed well across the chemical mechanisms from the selected earth system and other global tropospheric chemistry-transport models, there were differences in the detailed responses between the chemical mechanisms that could be tracked down by sensitivity analysis to differences in the representation of C1–C3 chemistry. Inter-mechanism ranges in NOx compensation points were about 0.17 ± 0.12 when expressed relative to the inter-mechanism average. Monte Carlo uncertainty analysis carried out with a single chemical mechanism put the intra-mechanism range a factor of three higher at 0.50 ± 0.12. Similar differences between inter-mechanism and intra-mechanism ranges were found for hydroxyl radical depletion but were up to a factor of six wider for ozone formation from incremental additions of organic compounds. The cause of the discrepancies between the inter- and intra-mechanism ranges was found to be the large uncertainties that are present in the laboratory determinations of the rate coefficients and product channel branching ratios of some key chemical reactions involving organic peroxy radicals and hydroperoxides. Whilst these large uncertainties are present in the laboratory determinations, there will be irreducible uncertainties in the predictions from the earth system and other chemistry-transport models of methane and tropospheric ozone trends since pre-industrial times and hence their contributions to the radiative forcing of climate change. Further definitive laboratory studies of the reaction rates and product yields of the reactions of the simple organic peroxy radicals and hydroperoxides are required to resolve and reduce current uncertainties in earth system and chemistry-transport model predictions.

atmospheric chemistry↗
DOE OSTI2026

Predicting multiphase flow and tracer transport for an underground chemical explosive test

Detecting radionuclide gas seepage from clandestine underground nuclear tests is central to nonproliferation explosion monitoring research. Yet, early-time (<6 day) gas transport driven by the explosive pressure wave remains poorly constrained due to scarcity of field data. We simulate multi-phase gas transport in the vadose zone using pre-shot data from a recent chemical explosion in P-Tunnel at the Nevada National Security Site, USA. Despite using a simplified 2D-radial model, predictions of tracer arrival matched observations within one order-of-magnitude. Our results show how transient blast forcing rapidly mobilizes gases from the cavity into surrounding rock – critical for optimizing sensor placement and test planning. This unique integration of field data and modeling represents a significant improvement in our ability to predict gas migration from underground explosions. More broadly, it offers insights into the coupled dynamics of pressure waves and contaminant transport in the vadose zone, with implications for monitoring and hazard assessment.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2018

Reactive Transport and Mass Balance Modeling of the Stimson Sedimentary Formation and Altered Fracture Zones Constrain Diagenetic Conditions at Gale Crater, Mars

On a planet as cold and dry as present-day Mars, evidence of multiple aqueous episodes offers an intriguing view into very different past environments. Fluvial, lacustrine, and eolian depositional environments are being investigated by the Mars Science Laboratory Curiosityin Gale crater, Mars. Geochemical and mineralogical observations of these sedimentary rocks suggest diagenetic processes affected the sediments. Here, we analyze diagenesis of the Stimson formation eolian parent material, which caused loss of olivine and formation of magnetite. Additional, later alteration in fracture zones resulted in preferential dissolution of pyroxene and precipitation of secondary amorphous silica and Ca sulfate. The ability to compare the unaltered parent material with the reacted material allows constraints to be placed on the characteristics of the altering solutions. In this work we use a combination of a mass balance approach calculating the fraction of a mobile element lost or gained, τ, with fundamental geochemical kinetics and thermodynamics in the reactive transport code CrunchFlow to examine the characteristics of multiple stages of aqueous alteration at Gale crater, Mars. Our model results indicate that early diagenesis of the Stimson sedimentary formation is consistent with leaching of an eolian deposit by a near-neutral solution, and that formation of the altered fracture zones is consistent with a very acidic, high sulfate solution containing Ca, P and Si. These results indicate a range of past aqueous conditions occurring at Gale crater, Mars, with important implications for past Martian climate and environments.

Gale crater↗
NASA NTRS2018

Reactive Transport and Mass Balance Modeling of the Stimson Sedimentary Formation and Altered Fracture Zones Constrain Diagenetic Conditions at Gale Crater, Mars

On a planet as cold and dry as present-day Mars, evidence of multiple aqueous episodes offers an intriguing view into very different past environments. Fluvial, lacustrine, and eolian depositional environments are being investigated by the Mars Science Laboratory Curiosity in Gale crater, Mars. Geochemical and mineralogical observations of these sedimentary rocks suggest diagenetic processes affected the sediments. Here, we analyze diagenesis of the Stimson formation eolian parent material, which caused loss of olivine and formation of magnetite. Additional, later alteration in fracture zones resulted in preferential dissolution of pyroxene and precipitation of secondary amorphous silica and Ca sulfate. The ability to compare the unaltered parent material with the reacted material allows constraints to be placed on the characteristics of the altering solutions. In this work we use a combination of a mass balance approach calculating the fraction of a mobile element lost or gained, tau, with fundamental geochemical kinetics and thermodynamics in the reactive transport code CrunchFlow to examine the characteristics of multiple stages of aqueous alteration at Gale crater, Mars. Our model results indicate that early diagenesis of the Stimson sedimentary formation is consistent with leaching of an eolian deposit by a near-neutral solution, and that formation of the altered fracture zones is consistent with a very acidic, high sulfate solution containing Ca, P and Si. These results indicate a range of past aqueous conditions occurring at Gale crater, Mars, with important implications for past martian climate and environments.

Gale↗
NASA NTRS1973

Aeronautical fuel conservation possibilities for advanced subsonic transports

The anticipated growth of air transportation is in danger of being constrained by increased prices and insecure sources of petroleum-based fuel. Fuel-conservation possibilities attainable through the application of advances in aeronautical technology to aircraft design are identified with the intent of stimulating NASA R and T and systems-study activities in the various disciplinary areas. The material includes drag reduction; weight reduction; increased efficiency of main and auxiliary power systems; unconventional air transport of cargo; and operational changes.

Braslow, A. L.↗
DOE OSTI2022

Particle phase-state variability in the North Atlantic free troposphere during summertime is determined by atmospheric transport patterns and sources

Abstract. Free tropospheric aerosol particles have important but poorly constrained climate effects due to transformations of their physicochemical properties during long-range transport. In this study, we investigate the chemical composition and provide an overview of the phase states of individual particles that have undergone long-range transport over the North Atlantic Ocean in June and July 2014, 2015, and 2017 to the Observatory of Mount Pico (OMP) in the Azores. The OMP is an ideal site for studying long-range-transported free tropospheric particles because local emissions have a negligible influence and contributions from the boundary layer are rare. We used the FLEXible PARTicle Lagrangian particle dispersion model (FLEXPART) to determine the origins and transport trajectories of sampled air masses and found that most of them originated from North America and recirculated over the North Atlantic Ocean. The FLEXPART analysis showed that the sampled air masses were highly aged (average plume age >10 d). Size-resolved chemical compositions of individual particles were probed using computer-controlled scanning electron microscopy with an energy-dispersive X-ray spectrometer (CCSEM-EDX) and scanning transmission X-ray microscopy with near-edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS). CCSEM-EDX results showed that the most abundant particle types were carbonaceous (∼ 29.9 % to 82.0 %), sea salt (∼ 0.3 % to 31.6 %), and sea salt with sulfate (∼ 2.4 % to 31.5 %). We used a tilted stage interfaced within an environmental scanning electron microscope (ESEM) to determine the phase states of individual submicron particles. We found that most particles (∼ 47 % to 99 %) were in the liquid state at the time of collection due to inorganic inclusions. Moreover, we also observed substantial fractions of solid and semisolid particles (∼ 0 % to 30 % and ∼ 1 % to 42 %, respectively) during different transport patterns and events, reflecting the particles' phase-state variability for different atmospheric transport events and sources. Combining phase state measurements with FLEXPART CO tracer analysis, we found that wildfire-influenced plumes can result in particles with a wide range of viscosities after long-range transport in the free troposphere. We also used temperature and RH values extracted from the Global Forecast System (GFS) along the FLEXPART-simulated path to predict the phase state of the particles during transport and found that neglecting internal mixing with inorganics would lead to an overestimation of the viscosity of free tropospheric particles. Our findings warrant future investigation aiming at the quantitative assessment of the influence of internal mixing on the phase states of the individual particles. This study also provides insights into the chemical composition and phase state of free tropospheric particles, which can help models to reduce uncertainties about the effects of ambient aerosol particles on climate.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1980

OPDOT: A computer program for the optimum preliminary design of a transport airplane

A description of a computer program, OPDOT, for the optimal preliminary design of transport aircraft is given. OPDOT utilizes constrained parameter optimization to minimize a performance index (e.g., direct operating cost per block hour) while satisfying operating constraints. The approach in OPDOT uses geometric descriptors as independent design variables. The independent design variables are systematically iterated to find the optimum design. The technical development of the program is provided and a program listing with sample input and output are utilized to illustrate its use in preliminary design. It is not meant to be a user's guide, but rather a description of a useful design tool developed for studying the application of new technologies to transport airplanes.

Sliwa, S. M.↗
NASA NTRS1987

Dendritic growth in a supercooled alloy melt

A simple model which describes the growth of an 'array' of dendrites into a supercooled, binary, alloy melt is presented. Solute diffusion is calculated by superposing the solutions given by Flemings and Zener, and also, by superposing the solutions given by Ivantsov and Flemings. A general expression for the transport solution is suggested from which all other dendrite growth models presented earlier may be obtained as special cases. It is shown that both 'free' and 'constrained' growth may be described by a single transport solution, which indicates that (1) both thermal and solutal effects will be important during 'free' growth in dilute alloys, (2) only solutal effects are predominant during 'free' growth in concentrated alloys and during 'constrained' growth. An examination of the relevant dimensionless parameters also suggests that all dendrite growth models, regardless of the assumptions used to determine the tip radius (marginal stability, minimum undercooling, maximum velocity, minimum entropy production) should predict the experimentally observed extrema in tip radius and growth velocity in dilute alloys, during 'free' dendritic growth. Experimental data in binary H2O-NaCl and succinonitrile-acetone solutions are shown to be in good agreement with the model.

Laxmanan, V.↗
DOE OSTI2022

Platform for probing radiation transport properties of hydrogen at conditions found in the deep interiors of red dwarfs

We describe an experimental concept at the National Ignition Facility for specifically tailored spherical implosions to compress hydrogen to extreme densities (up to ∼800× solid density, electron number density ne∼4×1025 cm−3) at moderate temperatures (T∼200 eV), i.e., to conditions, which are relevant to the interiors of red dwarf stars. The dense plasma will be probed by laser-generated x-ray radiation of different photon energy to determine the plasma opacity due to collisional (free–free) absorption and Thomson scattering. The obtained results will benchmark radiation transport models, which in the case for free–free absorption show strong deviations at conditions relevant to red dwarfs. This very first experimental test of free–free opacity models at these extreme states will help to constrain where inside those celestial objects energy transport is dominated by radiation or convection. Moreover, our study will inform models for other important processes in dense plasmas, which are based on electron–ion collisions, e.g., stopping of swift ions or electron–ion temperature relaxation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2012

The Impact of Geometrical Constraints on Collisionless Magnetic Reconnection

One of the most often cited features associated with collisionless magnetic reconnection is a Hall-type magnetic field, which leads, in antiparallel geometries, to a quadrupolar magnetic field signature. The combination of this out of plane magnetic field with the reconnection in-plane magnetic field leads to angling of magnetic flux tubes out of the plane defined by the incoming magnetic flux. Because it is propagated by Whistler waves, the quadrupolar field can extend over large distances in relatively short amounts of time - in fact, it will extend to the boundary of any modeling domain. In reality, however, the surrounding plasma and magnetic field geometry, defined, for example, by the overall solar wind flow, will in practice limit the extend over which a flux tube can be angled out of the main plain. This poses the question to what extent geometric constraints limit or control the reconnection process and this is the question investigated in this presentation. The investigation will involve a comparison of calculations, where open boundary conditions are set up to mimic either free or constrained geometries. We will compare momentum transport, the geometry of the reconnection regions, and the acceleration if ions and electrons to provide the current sheet in the outflow jet.

Hesse, Michael↗
NASA NTRS2014

A High Speed, Radiation Hard X-Ray Imaging Spectroscometer for Planetary Investigations

X-ray observations provide a unique window into fundamental processes in planetary physics, and one that is complementary to observations obtained at other wavelengths. We propose to develop an X-ray imaging spectrometer (0.1-10 keV band) that, on orbital planetary missions, would measure the elemental composition, density, and temperature of the hot plasma in gas giant magnetospheres, the interaction of the Solar wind with the upper atmospheres of terrestrial planets, and map the elemental composition of the surfaces of the Galilean moons and rocky or icy airless systems on spatial scales as small as a few meters. The X-ray emission from gas giants, terrestrial planets and moons with atmospheres, displays diverse characteristics that depend on the Solar wind's interaction with their upper atmospheres and/or magnetospheres. Our imaging spectrometer, as part of a dedicated mission to a gas giant, will be a paradigm changing technology. On a mission to the Jovian system, our baseline instrument would map the elemental composition of the rocky and icy surfaces of the Galilean moons via particle-induced X-ray fluorescence. This instrument would also measure the temperature, density and elemental abundance of the thermal plasma in the magnetosphere and in the Io plasma torus (IPT), explore the interaction of the Solar wind with the magnetosphere, and characterize the spectrum, flux, and temporal variability of X-ray emission from the polar auroras. We will constrain both the mode of energy transport and the effective transport coefficients in the IPT and throughout the Jovian magnetosphere by comparing temporal and spatial variations of the X-ray emitting plasma with those seen from the cooler but energetically dominant 5 eV plasma.

Kraft, R. P.↗