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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Application of technology developed for flight simulation at NASA. Langley Research Center

In order to meet the stringent time-critical requirements for real-time man-in-the-loop flight simulation, computer processing operations including mathematical model computation and data input/output to the simulators must be deterministic and be completed in as short a time as possible. Personnel at NASA's Langley Research Center are currently developing the use of supercomputers for simulation mathematical model computation for real-time simulation. This, coupled with the use of an open systems software architecture, will advance the state-of-the-art in real-time flight simulation.

Cleveland, Jeff I., II↗
DOE OSTI2020

Construction of a Code Verification Matrix for Heat Conduction With Finite Element Code Applications

When establishing the pedigree of a simulation tool, code verification is used to ensure that the implemented numerical algorithm is a faithful representation of its underlying mathematical model. During this process, numerical results on various meshes are systematically compared to a reference analytic solution. The selection of analytic solutions can be a laborious process, as it is difficult to establish adequate code confidence without performing redundant work. In this report we address this issue by applying a physics-based process that establishes a set of reference problems. In this process, code simulation options are categorized and systematically tested, which ensures that gaps in testing are easily identified and addressed. The resulting problems are primarily intended for code verification analysis but may also be useful for comparison to other simulation codes, troubleshooting activities, or training exercises. The process is used to select fifteen code verification problems relevant for the one-dimensional steady-state heat conduction equation. These problems are applicable to a wide variety of simulation tools, but, in this work, a demonstration is performed using the finite element-based nuclear fuel performance code BISON. Convergence to the analytic solution at the theoretical rate is quantified for a selection of the problems, which establishes a baseline pedigree for the code. Not only can this standard set of conduction solutions be used for verification of other codes, but also the physics-based process for selecting problems can be utilized to quantify and expand testing for any simulation tool.

42 ENGINEERING↗
NASA NTRS2005

Hardware in-the-Loop Demonstration of Real-Time Orbit Determination in High Earth Orbits

This paper presents results from a study conducted at Goddard Space Flight Center (GSFC) to assess the real-time orbit determination accuracy of GPS-based navigation in a number of different high Earth orbital regimes. Measurements collected from a GPS receiver (connected to a GPS radio frequency (RF) signal simulator) were processed in a navigation filter in real-time, and resulting errors in the estimated states were assessed. For the most challenging orbit simulated, a 12 hour Molniya orbit with an apogee of approximately 39,000 km, mean total position and velocity errors were approximately 7 meters and 3 mm/s respectively. The study also makes direct comparisons between the results from the above hardware in-the-loop tests and results obtained by processing GPS measurements generated from software simulations. Care was taken to use the same models and assumptions in the generation of both the real-time and software simulated measurements, in order that the real-time data could be used to help validate the assumptions and models used in the software simulations. The study makes use of the unique capabilities of the Formation Flying Test Bed at GSFC, which provides a capability to interface with different GPS receivers and to produce real-time, filtered orbit solutions even when less than four satellites are visible. The result is a powerful tool for assessing onboard navigation performance in a wide range of orbital regimes, and a test-bed for developing software and procedures for use in real spacecraft applications.

Moreau, Michael↗
NASA NTRS1989

Fragmentation of cosmic-string loops

The fragmentation of cosmic string loops is discussed, and the results of a simulation of this process are presented. The simulation can evolve any of a large class of loops essentially exactly, including allowing fragments that collide to join together. Such reconnection enhances the production of small fragments, but not drastically. With or without reconnections, the fragmentation process produces a collection of nonself-intersecting loops whose typical length is on the order of the persistence length of the initial loop.

York, Thomas↗
NASA NTRS2006

Experimental Demonstration of the Molten Oxide Electrolysis Method for Oxygen and Iron Production from Simulated Lunar Materials

This paper presents the results of a Marshall Space Flight Center funded effort to conduct an experimental demonstration of the processing of simulated lunar resources by the molten oxide electrolysis (MOE) process to produce oxygen and metal from lunar resources to support human exploration of space. Oxygen extracted from lunar materials can be used for life support and propellant, and silicon and metallic elements produced can be used for in situ fabrication of thin-film solar cells for power production. The Moon is rich in mineral resources, but it is almost devoid of chemical reducing agents, therefore, molten oxide electrolysis, MOE, is chosen for extraction, since the electron is the most practical reducing agent. MOE was also chosen for following reasons. First, electrolytic processing offers uncommon versatility in its insensitivity to feedstock composition. Secondly, oxide melts boast the twin key attributes of highest solubilizing capacity for regolith and lowest volatility of any candidate electrolytes. The former is critical in ensuring high productivity since cell current is limited by reactant solubility, while the latter simplifies cell design by obviating the need for a gas-tight reactor to contain evaporation losses as would be the case with a gas or liquid phase fluoride reagent operating at such high temperatures. In the experiments reported here, melts containing iron oxide were electrolyzed in a low temperature supporting oxide electrolyte (developed by D. Sadoway, MIT).

Curreri, P. A.↗
NASA NTRS2011

ARC+(Registered Trademark) and ARC PC Welding Simulators: Teach Welders with Virtual Interactive 3D Technologies

123 Certification Inc., a Montreal based company, has developed an innovative hands-on welding simulator solution to help build the welding workforce in the most simple way. The solution lies in virtual reality technology, which has been fully tested since the early 90's. President and founder of 123 Certification Inc., Mr. Claude Choquet Ing. Msc. IWE. acts as a bridge between the welding and the programming world. Working in these fields for more than 20 years. he has filed 12 patents world-wide for a gesture control platform with leading edge hardware related to simulation. In the summer of 2006. Mr Choquet was proud to be invited to the annual IIW International Weld ing Congress in Quebec City to launch the ARC+ welding simulator. A 100% virtual reality system and web based training center was developed to simulate multi process. multi-materiaL multi-position and multi pass welding. The simulator is intended to train welding students and apprentices in schools or industries. The welding simulator is composed of a real welding e[eetrode holder (SMAW-GTAW) and gun (GMAW-FCAW). a head mounted display (HMD), a 6 degrees of freedom tracking system for interaction between the user's hands and head. as well as external audio speakers. Both guns and HMD are interacting online and simultaneously. The welding simulation is based on the law of physics and empirical results from detailed analysis of a series of welding tests based on industrial applications tested over the last 20 years. The simulation runs in real-time, using a local logic network to determine the quality and shape of the created weld. These results are based on the orientation distance. and speed of the welding torch and depth of penetration. The welding process and resulting weld bc.1d are displayed in a virtual environment with screenplay interactive training modules. For review. weld quality and recorded process values can be displayed and diagnosed after welding. To help in the le.tming process, a learning curve for each student and each Virtual Welding Class'" can be plotted, for an instructor's review or a required third party evaluation.

Choquet, Claude↗
DOE OSTI2020

Literature Review on the Theory and Measurement of Dry Sliding Friction of Metals

Understanding the friction behavior between two sliding bodies can inform the design of machines, processing of materials, and simulation of dynamic processes. Kinetic friction is a complex phenomenon that depends on a multitude of factors such as sliding velocity, normal force, contact area, surface roughness, material properties, lubrication conditions, and thermal effects. This literature review covers the major known effects of sliding velocity, normal load, and surface roughness on the measured kinetic friction coefficient in the context of microscopic friction phenomena. Classic macroscale friction models are reviewed to illustrate approaches for simulating friction behavior. Prominent experimental friction setups within the literature are discussed with respect to achievable velocity and pressure regimes. The background information gathered here will be used to inform experimental procedures and modeling strategies of the exploratory research (ER) project titled “Measurement of Dynamic Friction via Kolsky Bar” (20200418ER).

36 MATERIALS SCIENCE↗
DOE OSTI2019

Numerical Investigation of the Effect of Rolling on the Localized Stress and Strain Induction for Wire + Arc Additive Manufactured Structures

Cold rolling can be used in-process or post-process to improve microstructure, mechanical properties and residual stress in directed-energy-deposition techniques, such as the high deposition rate wire + arc additive manufacturing (WAAM) process. Finite element simulations of the rolling process are employed to investigate the effect of rolling parameters, in particular rolling load and roller profile radius on the residual stress field as well as plastic strain distribution for the profiled roller. The results show the response to rolling of commonly used structural metals in WAAM, i.e., AA2319, S335JR steel and Ti-6Al-4V, taking into account the presence of residual stresses. The rolling load leads to changes in the location and the maximum value of the compressive residual stresses, as well as the depth of the compressive residual stresses. However, the roller profile radius only changes the maximum value of these compressive residual stresses. Changing the rolling load influences the equivalent plastic strain close to the top surface of the wall as well as in deeper areas, whereas the influence of the roller profile radius is negligible. The plastic strain distribution is virtually unaffected by the initial residual stresses prior to rolling. Finally, design curves were generated from the simulations for different materials, suggesting ideal rolling load and roller profile combinations for microstructural improvement requiring certain plastic strains at a specific depth of the additive structure.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Investigation of the Role of the Role of Nuclear Physics in Heavy Element Nucleosynthesis, through the Study of Key Reactions, and the Improvement of Theoretical Reaction Rates (Final Report)

Neutrino-driven winds in core-collapse supernovae have been identified as a possible site for the production of elements heavier than iron. Traditionally, these neutrino-driven winds have been proposed as the site of the main r-process. Recent simulations fail to reproduce the conditions required for the main r-process. while they remain a promising site for producing the lightest elements beyond iron, e.g., Sr, Y, and Zr through the νp process. The efficiency of the νp process depends on the hydrodynamical conditions, the electron fraction (which is related to the neutrino properties), and the nuclear reactions on many short-lived nuclei with limited (if at all) experimental information. The reaction rates on these nuclei are based on theoretical predictions using the Hauser-Feshbach model. Recent sensitivity studies have highlighted the importance of neutron-induced reactions on these nuclei along the νp process path. This work aimed to experimentally constrain reaction rates that are known to play a key role in the neutrino-p process nucleosynthesis. A secondary subsequently-added objective was to start the implementation of techniques that improve the description of nuclear properties in the Hauser-Feshbach model by extending the microscopic nuclear level density description offered via the shell model to high excitation energies without using experiment-based renormalizations. The main objective of this work was the experimental constraint of the 56 Ni(n,p) 56 Co reaction rate via a measurement of the inverse reaction 56 Co(p,n) 56 Ni at the National Superconducting Cyclotron Laboratory (NSCL) and later the Facility for Rare Isotope Beams (FRIB). This reaction is considered the key one for determining the yields possible by the neutrino-p process. A technique for this type of measurement in inverse kinematics at low energies did not exist before this work. The work also had two secondary objectives. First, to contribute to efforts to measure the same reaction in direct kinematics using a radioactive target at Los Alamos National Laboratory (LANL), and second, to advance work to implement shell-model-deduced microscopic level densities in Hauser-Feshbach calculations. The project has resulted in the development of the first technique to perform (p,n) cross-section measurements in relevant-for-astrophysics low energies in inverse kinematics using a magnetic spectrometer or separator, and neutron detectors for neutron tagging. It has also resulted in the precise measurement of the cross-section of the 40 Ar(p,n) 40 K reaction in a proof-of-principle experiment realized by using a beam-line quadrupole of the ReA3 accelerator of NSCL/FRIB. As part of this project the technique was successfully adapted to make use of the superior acceptance of the Separator for Capture Reactions (SECAR) at FRIB. In this project, the required experimental setup simulations and beam optics were developed and tested with the measurement of the 58 Fe(p,n) 58 Cu reaction cross-section. Additionally, this project contributed with simulation work to the development of a technique to measure (n,p) reactions with radioactive targets at LANL, and which resulted in the measurement of the key 56 Ni(n,p) 56 Co reaction cross-section at neutron energies above ≈1 MeV. Last, the project initiated work in the development of shell model based level densities using the moments method.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Thermal analysis of projected molten salt compositions during FFTF and EBR-II used nuclear fuel processing

This work studies the change in liquidus temperature of the salt used in the Mk-IV electrorefiner at the Idaho National Laboratory during processing campaigns of sodium-bonded driver fuels from Experimental Breeder Reactor II and the Fast Flux Test Facility reactor. Modeling and Simulation Tool for Electrochemical Recycling Systems (MASTERS), an INL proprietary pyroprocessing flowsheet simulation tool, was used to simulate the processing campaigns and determine the resulting composition changes of the Mark-IV electrorefiner salt. Surrogate salt samples simulating the Mk-IV electrorefiner salt during the fuel processing campaigns were prepared, and the thermal properties were measured via differential scanning calorimetry. Results from this study indicate that after processing approximately 2,150 kg of uranium metal from used fuel, the liquidus temperature of the molten salt exceeds 520°C, which is a significant increase from 352°C (the melting temperature of eutectic LiCl-KCl). It was also discovered that the liquidus temperature is strongly dependent on the amount of NaCl accumulating in the Mk-IV electrorefiner salt. Thus, the assessment of the liquidus temperature during the subsequent fuel processing campaigns can be simplified by considering the ternary LiCl-KCl-NaCl system only.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Modeling of fluid injection-induced fault reactivation using coupled fluid flow and mechanical interface model

The present study is aimed at developing a numerical model to reproduce coupled hydro-mechanical processes associated with fault reactivation by fluid injection in low permeability rock, as part of the DECOVALEX-2019 project Task B. We proposed a modeling approach for simulating the processes using the TOUGH-FLAC simulator, and modeled a fault reactivation experiment conducted at Mont Terri Rock Laboratory in Switzerland. The first step of the study involved benchmark calculations considering a simplified fault plane and geometry. Fluid flow along a fault was modeled using elements of aperture-sized thickness on the basis of Darcy's law and the cubic law in TOUGH2, whereas the mechanical behavior of a single fault was represented by zero-thickness interface elements in FLAC3D upon which a slip and/or separation is allowed. A methodology to connect a TOUGH2 volume element to a FLAC3D interface element was developed for handling the hydro-mechanical interactions on the fault during fluid injection. Two different fault models for describing the evolutions of hydraulic aperture by elastic fracture opening and failure-induced aperture increase were considered in the benchmark calculations. In the coupling process, the changes in geometrical features and hydrological properties induced by mechanical deformation were continuously updated. The transient responses of the fault and host rock to stepwise pressurization were examined during the simulation. The hydro-mechanical behavior, including the injection flow rate, pressure distribution around the borehole, stress conditions, and displacements in normal and shear directions were monitored in the surrounding rock and along the fault. The results of benchmark calculations suggest that the developed model reasonably represents the hydro-mechanical behavior of a fault and the surrounding rock. This modeling approach was applied to the fault reactivation experiment of the Mont Terri Rock Laboratory. In this interpretive modeling, a parametric study was conducted to examine the effects of input parameters regarding in situ stress and fault properties on the hydro-mechanical responses of the fault to water injection. Then, an optimal parameter set to reproduce the field experiment results was chosen by trial-and-error. The injection flow rate and pressure response during fault reactivation closely matched those obtained at the site, which indicates the capability of the model to appropriately capture the progressive pathway evolution during fault reactivation tests at the site. Finally, the anchor displacements were overestimated by the model, but a fair agreement was obtained in terms of the order of magnitude and the variation tendency.

58 GEOSCIENCES↗
DOE OSTI2023

Machine learning models inaccurately predict current and future high-latitude C balances

The high-latitude carbon (C) cycle is a key feedback to the global climate system, yet because of system complexity and data limitations, there is currently disagreement over whether the region is a source or sink of C. Recent advances in big data analytics and computing power have popularized the use of machine learning (ML) algorithms to upscale site measurements of ecosystem processes, and in some cases forecast the response of these processes to climate change. Due to data limitations, however, ML model predictions of these processes are almost never validated with independent datasets. To better understand and characterize the limitations of these methods, we develop an approach to independently evaluate ML upscaling and forecasting. We mimic data-driven upscaling and forecasting efforts by applying ML algorithms to different subsets of regional process-model simulation gridcells, and then test ML performance using the remaining gridcells. In this study, we simulate C fluxes and environmental data across Alaska using ecosys, a process-rich terrestrial ecosystem model, and then apply boosted regression tree ML algorithms to training data configurations that mirror and expand upon existing AmeriFLUX eddy-covariance data availability. We first show that a ML model trained using ecosys outputs from currently-available Alaska AmeriFLUX sites incorrectly predicts that Alaska is presently a modeled net C source. Increased spatial coverage of the training dataset improves ML predictions, halving the bias when 240 modeled sites are used instead of 15. However, even this more accurate ML model incorrectly predicts Alaska C fluxes under 21st century climate change because of changes in atmospheric CO 2 , litter inputs, and vegetation composition that have impacts on C fluxes which cannot be inferred from the training data. Our results provide key insights to future C flux upscaling efforts and expose the potential for inaccurate ML upscaling and forecasting of high-latitude C cycle dynamics.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

A Mobility-Driven Approach to Modeling Building Energy

Buildings are one of the primary energy consumers in any city's energy use [12]. Presence and absence of humans is a major contributing factor to the energy use in a building. In this paper, we present an approach to generating a realistic model of human building occupancy throughout a typical work week. We use the Toolbox for Urban Mobility Systems (TUMS) to generate a synthetic population based on population distribution estimates, we schedule the population's daily commute based on National Household Travel Survey (NHTS) survey data, and we simulate their daily travel patterns using an agent-based transportation simulation (TRANSIMS). We process and fuse the simulation output to produce a list of the first and last seen location of each agent in the simulation. Based on the arrival at the last destination, we map each agent to one of the nearby buildings. Using these agent arrivals, as well as NHTS data, we create an hourly occupancy schedule for each building. We successfully demonstrate this workflow at the example of the Chicago Loop, a major business district in Chicago, Illinois.

Berres, Andy↗
NASA NTRS2010

The Kepler End-to-End Model: Creating High-Fidelity Simulations to Test Kepler Ground Processing

The Kepler mission is designed to detect the transit of Earth-like planets around Sun-like stars by observing 100,000 stellar targets. Developing and testing the Kepler ground-segment processing system, in particular the data analysis pipeline, requires high-fidelity simulated data. This simulated data is provided by the Kepler End-to-End Model (ETEM). ETEM simulates the astrophysics of planetary transits and other phenomena, properties of the Kepler spacecraft and the format of the downlinked data. Major challenges addressed by ETEM include the rapid production of large amounts of simulated data, extensibility and maintainability.

Bryson, Stephen T.↗
NASA NTRS2012

Unsteady Aero Computation of a 1 1/2 Stage Large Scale Rotating Turbine

This report is the documentation of the work performed for the Subsonic Rotary Wing Project under the NASA s Fundamental Aeronautics Program. It was funded through Task Number NNC10E420T under GESS-2 Contract NNC06BA07B in the period of 10/1/2010 to 8/31/2011. The objective of the task is to provide support for the development of variable speed power turbine technology through application of computational fluid dynamics analyses. This includes work elements in mesh generation, multistage URANS simulations, and post-processing of the simulation results for comparison with the experimental data. The unsteady CFD calculations were performed with the TURBO code running in multistage single passage (phase lag) mode. Meshes for the blade rows were generated with the NASA developed TCGRID code. The CFD performance is assessed and improvements are recommended for future research in this area. For that, the United Technologies Research Center's 1 1/2 stage Large Scale Rotating Turbine was selected to be the candidate engine configuration for this computational effort because of the completeness and availability of the data.

To, Wai-Ming↗
DOE OSTI2021

Development and Demonstration of a Reduced-Order PWR Power Dispatch Simulator

This report describes the development, modeling, and results of a reduced-order thermal power dispatch pressurized water reactor (RO-TPD-PWR) power plant simulator that incorporates coupled electrical and thermal power dispatch to an industrial process. The simulator is built on models that have been developed in previous work, including a Rancor Microworld model previously developed by INL and the University of Idaho [Ref] and reactor core and secondary system models that have been published previously [Ref]. The simulator also includes a scalable model of a high temperature electrolysis (HTE) system that has been developed at INL. A particular benefit of the Rancor Microworld model is that it is compatible with a human-system interface (HMI) that has already been developed by the Human System Simulation Laboratory (HSSL) at INL that can emulate the control room of a PWR for realistic human-in-the-loop studies with mock nuclear power plant operating procedures. The results of these human-in-the-loop tests will be compared with similar tests using a commercial full-scope generic PWR (GPWR) simulator that has been modified to include thermal power dispatch, referred to as the TPD-GPWR [ , ]. The simplicity of the RO-TPD-PWR helps to better understand and verify the results of the TPD-GPWR, which employs >1,000 variables and has much greater complexity. A second key purpose of the RO-TPD-PWR simulator is that its relative simplicity allows it scale between lab-size equipment (~100 kW) and full-scale nuclear power plants (~1 GW) by adjusting only a few parameters in the models, such as fluid masses and heat exchanger areas. The RO-TPD-PWR simulator will be used to guide the controls of lab tests, so that equipment in those tests, such as the Thermal Energy Distribution System (TEDS) and pilot-scale high temperature electrolysis (HTE) units at scales of 50-250 kW, may operate in a manner that is relevant to full-scale PWR operations.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1979

Simulated electronic heterodyne recording and processing of pulsed-laser holograms

The electronic recording of pulsed-laser holograms is proposed. The polarization sensitivity of each resolution element of the detector is controlled independently to add an arbitrary phase to the image waves. This method which can be used to simulate heterodyne recording and to process three-dimensional optical images, is based on a similar method for heterodyne recording and processing of continuous-wave holograms.

Decker, A. J.↗
DOE OSTI2022

Forest regeneration within Earth system models: current process representations and ways forward

Earth system models must predict forest responses to global change in order to simulate future global climate, hydrology, and ecosystem dynamics. These models are increasingly adopting vegetation demographic approaches that explicitly represent tree growth, mortality, and recruitment, enabling advances in the projection of forest vulnerability and resilience, as well as evaluation with field data. To date, simulation of regeneration processes has received far less attention than simulation of processes that affect growth and mortality, in spite of their critical role maintaining forest structure, facilitating turnover in forest composition over space and time, enabling recovery from disturbance, and regulating climate-driven range shifts. Here, our critical review of regeneration process representations within current Earth system vegetation demographic models reveals the need to improve parameter values and algorithms for reproductive allocation, dispersal, seed survival and germination, environmental filtering in the seedling layer, and tree regeneration strategies adapted to wind, fire, and anthropogenic disturbance regimes. These improvements require synthesis of existing data, specific field data-collection protocols, and novel model algorithms compatible with global-scale simulations. Vegetation demographic models offer the opportunity to more fully integrate ecological understanding into Earth system prediction; regeneration processes need to be a critical part of the effort.

54 ENVIRONMENTAL SCIENCES↗