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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Numerical Studies of Collisionless Current Layers

The purpose of this proposal was to investigate collisionless current layers using a variety of analytic and numerical tools. The first year of the contract was dedicated to analytical studies, to the porting and adaption of codes being used in this study, and to the numerical simulation of collisionless current layers. The second year entailed the development of multi-dimensional hybrid algorithms as well as the re-examination of the problem of integro-differential equations that occur in the linear stage of plasma instabilities.

Quest, Kevin B.↗
NASA NTRS2006

Real-Time Rocket/Vehicle System Integrated Health Management Laboratory For Development and Testing of Health Monitoring/Management Systems

Pratt & Whitney Rocketdyne has developed a real-time engine/vehicle system integrated health management laboratory, or testbed, for developing and testing health management system concepts. This laboratory simulates components of an integrated system such as the rocket engine, rocket engine controller, vehicle or test controller, as well as a health management computer on separate general purpose computers. These general purpose computers can be replaced with more realistic components such as actual electronic controllers and valve actuators for hardware-in-the-loop simulation. Various engine configurations and propellant combinations are available. Fault or failure insertion capability on-the-fly using direct memory insertion from a user console is used to test system detection and response. The laboratory is currently capable of simulating the flow-path of a single rocket engine but work is underway to include structural and multiengine simulation capability as well as a dedicated data acquisition system. The ultimate goal is to simulate as accurately and realistically as possible the environment in which the health management system will operate including noise, dynamic response of the engine/engine controller, sensor time delays, and asynchronous operation of the various components. The rationale for the laboratory is also discussed including limited alternatives for demonstrating the effectiveness and safety of a flight system.

Aguilar, R.↗
DOE OSTI2019

Simulations of particle interactions in a high-current RFQ

High-intensity beams of composite ions are susceptible to particle interactions that do not affect single ions, such as stripping of electrons and charge exchange. Beam dynamics simulation techniques used in accelerator design do not often include these particle interactions, and so the transmission of the real beam can be significantly different from the design simulations. We have modified the IMPACT-T code to include particle interactions as part of the beam dynamics simulations, including space-charge effects and beam losses. We have carried out validation simulations of interactions in a molecular hydrogen ion beam through an existing high-intensity deuteron RFQ design, as beam commissioning is often carried out using molecular hydrogen beams, to avoid deuteron-deuteron interactions in the accelerator leading to neutron activation. The new code framework successfully models the interactions within the beam, tracks the different source and product ions through the accelerator, and calculates the collective effects such as space charge from all particles together. Finally, we also discuss other simulation codes that could be modified to include similar interaction effects, and possible applications to other types of accelerators.

47 OTHER INSTRUMENTATION↗
NASA NTRS1985

Computer simulation of environmental, hazard scenarios in space

The development of the Advanced Computer Graphics Laboratory at NASA/JSC will enable NASA engineers to utilize state-of-the-art computer systems to simulate and analyze current and planned space missions. These systems utilize computer graphics to animate automated satellite rendezvous and docking, satellite servicing, tether operations, as well as remote manipulator activities and assembly of large space structures including the space station. These computer simulations enhance the engineering evaluation of possible hazardous scenarios in space by allowing users to view from any point in space these activities and determine if any potential problem could occur.

Brown, R. H.↗
DOE OSTI2024

Validation of Simulation Models for Wall-Connected Scrape off Layer Currents during MHD Activity in the HBT-EP Tokamak (Final Report)

This is the final report for the DOE award DE-SC0021325, titled “Validation of Simulation Models for Wall-Connected Scrape off Layer Currents during MHD Activity in the HBT-EP Tokamak” for the period September 1, 2020 – May 31, 2023. This award is part of a broader collaborative project, which supported training of a PhD student at Columbia University under the joint supervision of Dr. Hansen and Columbia project members. The award supported research into computational models for plasma and 3D conducting structures in the vicinity relevant to tokamak disruptions and other mode activity (eg. RWMs) using the NIMROD, and PSI-Tet, codes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Developing a simulation tool for evaluating in-motion detector systems [Slides]

In order to combat the illicit trafficking of nuclear materials, Radiation Detection Systems (RDS) are used to scan pedestrians, vehicles, cargo, luggage, and other conveyances. Many of these systems are used in an “in-motion” configuration where the detector or target are moving past the other. Current modeling and simulation tools lack the ability to produce time-series detector response profiles for in-motion applications.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2020

A 3D simulation comparison of carrier transport in green and blue c-plane multi-quantum well nitride light emitting diodes

Until recently, the electrical efficiency of green nitride light-emitting diodes (LEDs) was considerably lower than that of blue LEDs. This is particularly surprising as one would expect a reduced forward voltage with increasing emission wavelength. In this paper, we theoretically investigated the impact of the number of quantum wells on the forward voltage of III-nitride LEDs with x = 0.15 (blue) and x = 0.24 (green) In x Ga1–xN QWs. The simulated dependence of current density (J) on applied diode bias (V) shows a significant increase of 1.9 V in the forward voltage between one and five quantum well (QW) c-plane green LED structures. Artificially turning off the polarization fields in the simulation does not entirely suppress this effect. Due to the large band offsets in the green LED multiple QW stack, simulations indicate a sequential band filling of the QW sequence. Furthermore, this mechanism should not be limited to c-plane LEDs and could also be present in nonpolar or semipolar devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Counter-Current Flow Limitation Studies in Complex Geometries Utilizing Interface Capturing Simulations Coupled with PID Flow Rate Controller

In nuclear thermal-hydraulic studies, counter-current flow limitation (CCFL) typically refers to steam rising at a fast rate such that it prevents coolant from draining down within a confined channel. CCFL is a crucial issue in nuclear reactor safety analysis. This study investigates CCFL in debris bed channels using high-resolution interface-capturing simulations. A novel proportional-integral-derivative flow rate controller is developed to efficiently achieve the CCFL conditions. Verification studies confirm that CCFL occurs under the same conditions with or without the controller, demonstrating that PID control ensures accurate prediction. Three debris bed channel geometries were examined: a cylindrical channel, a channel with small obstacles, and a channel with large obstacles. Results show that obstacles significantly impact flow behavior, interfacial shear, wall shear, and pressure gradients required for CCFL. Furthermore, the comparison with experimental data confirmed that simulations incorporating geometric complexities align more closely with experimental CCFL conditions. A pressure gradient correlation was also developed for CCFL prediction.

Counter-current flow limitation↗
DOE OSTI2025

Analyzing the Effects of the Interference between One- and Two-Body Currents on Neutrino-Nucleus Scattering in ACHILLES

Modeling improvements of neutrino–nucleus scattering are an essential aspect of reducing systematic uncertainties for current and future neutrino oscillation experiments. In particular, retaining quantum mechanical effects such as the interference between one-body (1p1h) and two-body (2p2h) currents in our cross-section models is an essential consideration. This work investigates the impact of this interference term on neutrino–argon scattering using the ACHILLES event generator, which directly implements the interference model developed by Lovato, Rocco, and Steinberg. Using fluxes relevant to SBND, the DUNE near detector, and MiniBooNE, charged- and neutral-current event samples are generated and predicted event rates are plotted against a variety of kinematic variables. For events simulated using the SBND flux, it is found that interference contributes approximately 10 \% to the total charged-current event rate, and serves to enhance the quasi-elastic peak. When considering events generated using the DUNE flux, resonance interactions contribute more to the predicted event rate, as the neutrino flux extends out to higher energies. The relative interference contribution subsequently decreases to roughly 7 \%. Neutral-current simulations show a higher rate of neutron knockout. Finally, a comparison of argon-to-carbon cross-section ratios is performed utilizing fluxes from SBND and MiniBooNE.

Pando, Nathan [Fermilab]↗
DOE OSTI2025

Analyzing the Effects of the Interference between One- and Two-Body Currents on Neutrino-Nucleus Scattering in ACHILLES

Modeling improvements of neutrino–nucleus scattering are an essential aspect of reducing systematic uncertainties for current and future neutrino oscillation experiments. In particular, retaining quantum mechanical effects such as the interference between one-body (1p1h) and two-body (2p2h) currents in our cross-section models is an essential consideration. This work investigates the impact of this interference term on neutrino–argon scattering using the ACHILLES event generator, which directly implements the interference model developed by Lovato, Rocco, and Steinberg. Using fluxes relevant to SBND, the DUNE near detector, and MiniBooNE, charged- and neutral-current event samples are generated and predicted event rates are plotted against a variety of kinematic variables. For events simulated using the SBND flux, it is found that interference contributes approximately 10 \% to the total charged-current event rate, and serves to enhance the quasi-elastic peak. When considering events generated using the DUNE flux, resonance interactions contribute more to the predicted event rate, as the neutrino flux extends out to higher energies. The relative interference contribution subsequently decreases to roughly 7 \%. Neutral-current simulations show a higher rate of neutron knockout. Finally, a comparison of argon-to-carbon cross-section ratios is performed utilizing fluxes from SBND and MiniBooNE.

Pando, Nathan [Fermilab]↗
NASA NTRS2010

Global Response to Local Ionospheric Mass Ejection

We revisit a reported "Ionospheric Mass Ejection" using prior event observations to guide a global simulation of local ionospheric outflows, global magnetospheric circulation, and plasma sheet pressurization, and comparing our results with the observed global response. Our simulation framework is based on test particle motions in the Lyon-Fedder-Mobarry (LFM) global circulation model electromagnetic fields. The inner magnetosphere is simulated with the Comprehensive Ring Current Model (CRCM) of Fok and Wolf, driven by the transpolar potential developed by the LFM magnetosphere, and includes an embedded plasmaspheric simulation. Global circulation is stimulated using the observed solar wind conditions for the period 24-25 Sept 1998. This period begins with the arrival of a Coronal Mass Ejection, initially with northward, but later with southward interplanetary magnetic field. Test particles are launched from the ionosphere with fluxes specified by local empirical relationships of outflow to electrodynamic and particle precipitation imposed by the MIlD simulation. Particles are tracked until they are lost from the system downstream or into the atmosphere, using the full equations of motion. Results are compared with the observed ring current and a simulation of polar and auroral wind outflows driven globally by solar wind dynamic pressure. We find good quantitative agreement with the observed ring current, and reasonable qualitative agreement with earlier simulation results, suggesting that the solar wind driven global simulation generates realistic energy dissipation in the ionosphere and that the Strangeway relations provide a realistic local outflow description.

Moore, T. E.↗
NASA NTRS1995

Rings of the North Brazil Current: Their structure and behavior inferred from observations and a numerical simulation

Large anticyclonic rings are shed from the retroflecting North Brazil Current (NBC) near 8 deg N in the tropical western Atlantic. New subsurface velocity and temperature measurements within three such rings are presented here and are found to be consistent with previous in situ and remotely sensed NBC ring measurements. A high-resolution numerical model of the Atlantic Ocean forced by monthly wind stress and an imposed meridional overturning cell is found to shed NBC rings that approximate those observed. The model rings are more surface-intensified than those observed and somewhat smaller in diameter. Both observed and modeled NBC rings move northwestward along the coast of South America with a speed of 8-16 cm/s, considerably slower than predicted by analytical theories describing westward ring propagation. At least 2-3 rings per year separate from the NBC retroflection. Annually, 1-3 rings translate intact from their formation region near 50 deg W to the islands of the southeastern Caribbean, where they disintegrate after a lifetime of about 100 days. This study is the first to make use of subsurface temperature and velocity data to compute the volume of the anomalous ring core. NBC rings may be responsible for 3-4 Sv of direct mass transport across the equatorial-tropical gyre boundary or 20-25% of the total upper ocean cross-gyre transport required by the Atlantic meridional overturning cell. Translating NBC rings may contribute 20% of the total meridional heat transport by the ocean at this latitude.

Fratantoni, David M.↗
NASA NTRS2020

An Evaluation of UAS Pilot Workload and Acceptability Ratings with Four Simulated Radar Declaration Ranges

Currently, minimum operating standards (MOPS) are being developed for a broader range of UAS types, including smaller UAS that will feature onboard sensors that are low in size, weight, and power (Low SWaP). These sensors will have limited declaration ranges compared to ones typically found on medium-to-large UAS used to detect non-cooperative aircraft. A human-in-the-loop (HITL) study was conducted examining four possible radar declaration ranges (i.e., 1.5 nm, 2 nm, 2.5 nm, and 3 nm) for a potential low SWaP sensor with a DAA system. Participants had lower workload, particularly workload associated with temporal demand and effort. Furthermore, participants reported better ability to remain DAA well clear within the larger declaration range conditions, such as the 2.5 nm and 3 nm.

UAS↗
NASA NTRSDate not supplied

An Evaluation of UAS Pilot Workload and Acceptability Ratings with Four Simulated Radar Declaration Ranges

Currently, minimum operational performance standards (MOPS) are being developed for a broader range of unmanned aircraft system (UAS) platforms, including smaller UAS that will feature onboard sensors that are low in size, weight, and power, otherwise known as low SWaP. The low SWaP sensors used to detect non-cooperative traffic will have limited declaration ranges compared to those designed for medium-to-large UAS. A human-in-the-loop (HITL) study was conducted examining four possible radar declaration ranges (i.e., 1.5 NM, 2 NM, 2.5 NM, and 3 NM) for a potential low SWaP sensor with a detect and avoid (DAA) system encountering various non-cooperative encounters in Oakland Center airspace. Participants had lower workload, particularly workload associated with temporal demand and effort, in scenarios that featured larger declaration ranges. Furthermore, participants reported better ability to remain DAA well clear within the larger declaration range conditions, specifically with the 2.5 NM and 3 NM conditions.

UAS↗
NASA NTRS2020

An Evaluation of UAS Pilot Workload and Acceptability Ratings with Four Simulated Radar Declaration Ranges

Currently, minimum operational performance standards (MOPS) are being developed for a broader range of unmanned aircraft system (UAS) platforms, including smaller UAS that will feature onboard sensors that are low in size, weight, and power, otherwise known as low SWaP. The low SWaP sensors used to detect non-cooperative traffic will have limited declaration ranges compared to those designed for medium-to-large UAS. A human-in-the-loop (HITL) study was conducted examining four possible radar declaration ranges (i.e., 1.5 NM, 2 NM, 2.5 NM, and 3 NM) for a potential low SWaP sensor with a detect and avoid (DAA) system encountering various non-cooperative encounters in Oakland Center airspace. Participants had lower workload, particularly workload associated with temporal demand and effort, in scenarios that featured larger declaration ranges. Furthermore, participants reported better ability to remain DAA well clear within the larger declaration range conditions, specifically with the 2.5 NM and 3 NM conditions.

UAS↗