Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “distributed simulation”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

SIMULATIONS OF A DYNAMIC SOLAR CYCLE AND ITS EFFECTS ON THE INTERSTELLAR BOUNDARY EXPLORER RIBBON AND GLOBALLY DISTRIBUTED ENERGETIC NEUTRAL ATOM FLUX

Since 2009, observations by the Interstellar Boundary Explorer (IBEX) have vastly improved our understanding of the interaction between the solar wind (SW) and local interstellar medium through direct measurements of energetic neutral atoms (ENAs), which inform us about the heliospheric conditions that produced them. An enhanced feature of flux in the sky, the so-called IBEX ribbon, was not predicted by any global models before the first IBEX observations. A dominating theory of the origin of the ribbon, although still under debate, is a secondary charge-exchange process involving secondary ENAs originating from outside the heliopause. According to this mechanism, the evolution of the solar cycle should be visible in the ribbon flux. Therefore, in this paper we simulate a fully time-dependent ribbon flux, as well as globally distributed flux from the inner heliosheath (IHS), using time-dependent SW parameters from Sokół et al. as boundary conditions for our time-dependent heliosphere simulation. After post-processing the results to compute H ENA fluxes, our results show that the secondary ENA ribbon indeed should be time dependent, evolving with a period of approximately 11 yr, with differences depending on the energy and direction. Our results for the IHS flux show little periodic change with the 11 yr solar cycle, but rather with short-term fluctuations in the background plasma. While the secondary ENA mechanism appears to emulate several key characteristics of the observed IBEX ribbon, it appears that our simulation does not yet include all of the relevant physics that produces the observed ribbon.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Coordinate-based simulation of pair distance distribution functions for small and large molecular assemblies: implementation and applications

X-ray scattering has become a major tool in the structural characterization of nanoscale materials. Thanks to the widely available experimental and computational atomic models, coordinate-based X-ray scattering simulation has played a crucial role in data interpretation in the past two decades. However, simulation of real-space pair distance distribution functions (PDDFs) from small- and wide-angle X-ray scattering, SAXS/WAXS, has been relatively less exploited. This study presents a comparison of PDDF simulation methods, which are applied to molecular structures that range in size from β-cyclodextrin [1 kDa molecular weight (MW), 66 non-hydrogen atoms] to the satellite tobacco mosaic virus capsid (1.1 MDa MW, 81 960 non-hydrogen atoms). The results demonstrate the power of interpretation of experimental SAXS/WAXS from the real-space view, particularly by providing a more intuitive method for understanding of partial structure contributions. Furthermore, the computational efficiency of PDDF simulation algorithms makes them attractive as approaches for the analysis of large nanoscale materials and biological assemblies. The simulation methods demonstrated in this article have been implemented in stand-alone software, SolX 3.0 , which is available to download from https://12idb.xray.aps.anl.gov/solx.html.

Zuo, Xiaobing (ORCID:0000000201344804)↗
DOE OSTI2025

CGSim: A Simulation Framework for Large Scale Distributed Computing Environment

Large-scale distributed computing infrastructures such as the Worldwide LHC Computing Grid (WLCG) require comprehensive simulation tools for evaluating performance, testing new algorithms, and optimizing resource allocation strategies. However, existing simulators suffer from limited scalability, hardwired algorithms, lack of real-time monitoring, and inability to generate datasets suitable for modern machine learning approaches. We present CGSim, a simulation framework for large-scale distributed computing environments that addresses these limitations. Built upon the validated SimGrid simulation framework, CGSim provides high-level abstractions for modeling heterogeneous grid environments while maintaining accuracy and scalability. Key features include a modular plugin mechanism for testing custom workflow scheduling and data movement policies, interactive real-time visualization dashboards, and automatic generation of event-level datasets suitable for AI-assisted performance modeling. We demonstrate CGSim’s capabilities through a comprehensive evaluation using production ATLAS PanDA workloads, showing significant calibration accuracy improvements across WLCG computing sites. Scalability experiments show near-linear scaling for multi-site simulations, with distributed workloads achieving 6 × better performance compared to single-site execution. The framework enables researchers to simulate WLCG-scale infrastructures with hundreds of sites and thousands of concurrent jobs within practical time budget constraints on commodity hardware.

Vatsavai, Sairam Sri [Brookhaven National Laborato↗
DOE OSTI2014

Toward Online Adaptive Hyperthermia Treatment Planning: Correlation Between Measured and Simulated Specific Absorption Rate Changes Caused by Phase Steering in Patients

Purpose: Hyperthermia is the clinical application of heat, in which tumor temperatures are raised to 40°C to 45°C. This proven radiation and chemosensitizer significantly improves clinical outcome for several tumor sites. Earlier studies of the use of pre-treatment planning for hyperthermia showed good qualitative but disappointing quantitative reliability. The purpose of this study was to investigate whether hyperthermia treatment planning (HTP) can be used more reliably for online adaptive treatment planning during locoregional hyperthermia treatments. Methods and Materials: This study included 78 treatment sessions for 15 patients with non-muscle-invasive bladder cancer. At the start of treatments, temperature rise measurements were performed with 3 different antenna settings optimized for each patient, from which the absorbed power (specific absorption rate [SAR]) was derived. HTP was performed based on a computed tomography (CT) scan in treatment position with the bladder catheter in situ. The SAR along the thermocouple tracks was extracted from the simulated SAR distributions. Correlations between measured and simulated (average) SAR values were determined. To evaluate phase steering, correlations between the changes in simulated and measured SAR values averaged over the thermocouple probe were determined for all 3 combinations of antenna settings. Results: For 42% of the individual treatment sessions, the correlation coefficient between measured and simulated SAR profiles was higher than 0.5, whereas 58% showed a weak correlation (R of <0.5). The overall correlation coefficient between measured and simulated average SAR was weak (R=0.31; P<.001). The measured and simulated changes in average SAR after adapting antenna settings correlated much better (R=0.70; P<.001). The ratio between the measured and simulated quotients of maximum and average SARs was 1.03 ± 0.26 (mean ± SD), indicating that HTP can also correctly predict the relative amplitude of SAR peaks. Conclusions: HTP can correctly predict SAR changes after adapting antenna settings during hyperthermia treatments. This allows online adaptive treatment planning, assisting the operator in determining antenna settings resulting in increased tumor temperatures.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Radiation induces turbulence in particle-laden fluids

When a transparent fluid laden with solid particles is subject to radiative heating, non-uniformities in particle distribution result in local fluid temperature fluctuations. Under the influence of gravity, buoyancy induces vortical fluid motion which can lead to strong preferential concentration, enhancing the local heating and more non-uniformities in particle distribution. By employing direct numerical simulations this study shows that the described feedback loop can create and sustain turbulence. The velocity and length scale of the resulting turbulence is not known a priori, and is set by balance between viscous forces and buoyancy effects. When the particle response time is comparable to a viscous time scale, introduced in our analysis, the system exhibits intense fluctuations of turbulent kinetic energy and strong preferential concentration of particles.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

SU-E-T-609: Perturbation Effects of Pedicle Screws On Radiotherapy Dose Distributions

Purpose: Radiation therapy in conjunction with surgical implant fixation is a common combined treatment in case of bone metastases. However, metal implants generally used in orthopedic implants perturb radiation dose distributions. Carbon-Fiber Reinforced (CFR) PEEK material has been recently introduced for production of intramedullary screws and plates. Gold powder can be added to the CFR-PEEK material in order to enhance visibility of the screws during intraoperative imaging procedures. In this work, we investigated the perturbation effects of the pedicle screws made of CFR-PEEK, CFR-PEEK with added gold powder (CFR-PEEK-AU) and Titanium (Ti) on radiotherapy dose distributions. Methods: Monte Carlo (MC) simulations were performed using the EGSnrc code package for 6MV beams with 10×10 fields at SSD=100cm. By means of MC simulations, dose distributions around titanium, CFR- PEEK and CFR-PEEK-AU screws (manufactured by Carbo-Fix Orthopedics LTD, Israel) placed in a water phantom were calculated. The screw axis was either parallel or perpendicular to the beam axis. Dose perturbation (relative to dose in homogeneous water phantom) was assessed. Results: Maximum overdose due to backscatter was 10% for the Ti screws, 5% for the CFR-PEEK-AU screws and effectively zero for the CFR-PEEK screws. Maximum underdose due to attenuation was 25% for the Ti screws, 15% for the CFR-PEEK-AU screws and 5% for the CFR-PEEK screws. Conclusion: Titanium screws introduce the largest distortion on the radiation dose distribution. The gold powder added to the CFR-PEEK material improves visibility at the cost of increased dose perturbation. CFR-PEEK screws caused minimal alteration on the dose distribution. This can decrease possible over and underdose of adjacent tissue and thus favorably influence treatment efficiency. The use of such implants has potential clinical advantage in the treatment of neoplastic bone disease.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2026

T&D LIBRA: Simulation Framework for Transmission and Distribution Load and IBR Assessment

This paper introduces T&D LIBRA, a HELICS-based dynamic co-simulation framework designed for transmission and distribution (T&D) load and inverter-based resource assessment. This framework is designed to model interactions between single-phase induction motors (i.e., Motor-D), distributed energy resources (DERs) and the transmission network, emphasizing system stability during fault conditions. The primary objective of this research is to study the fault-induced delayed voltage recovery (FIDVR) behavior of the T&D networks using the co-simulation framework and to compare the results with conventional PSS/E only simulations. Simulations are validated using T&D co-simulations with a single distribution node and the IEEE 123-bus distribution test case. The co-simulation results demonstrate the value of using T&D co-simulations to capture motor stalling, DER tripping and other sources of voltage diversity on distribution networks.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2020

Performance and Feature Improvements in Parareal-based Power System Dynamic Simulation

In recent years, a novel Parareal-based approach has been developed for fast transient simulations of large power system interconnections. Parareal belongs to the class of Parallel-in-time algorithms for solution of systems of differential-algebraic equations in parallel over an interval of time. The selection of a reasonably fast and accurate coarse solution is crucial to improve the performance of Parareal algorithm. Semi-analytical solution methods are one promising approach to achieve this goal. They have been investigated, and some preliminary results are presented here. In addition, Parareal-based simulator has been expanded to enable co-simulation with OpenDSS, a widely used open-source distribution system simulator. Preserving the parallel nature of the Parareal approach and taking advantage of the parallel capabilities of the latest versions of OpenDSS, each distribution system can be solved in their entirety on different processors in parallel within the main Parareal simulator. This paper also presents the structure of the transmission and distribution co-simulation and some results with different dynamic models of inverter-based resources in the distribution systems.

Park, Byungkwon↗
DOE OSTI2012

Clinical evaluation of a commercial orthopedic metal artifact reduction tool for CT simulations in radiation therapy

Purpose: Severe artifacts in kilovoltage-CT simulation images caused by large metallic implants can significantly degrade the conspicuity and apparent CT Hounsfield number of targets and anatomic structures, jeopardize the confidence of anatomical segmentation, and introduce inaccuracies into the radiation therapy treatment planning process. This study evaluated the performance of the first commercial orthopedic metal artifact reduction function (O-MAR) for radiation therapy, and investigated its clinical applications in treatment planning. Methods: Both phantom and clinical data were used for the evaluation. The CIRS electron density phantom with known physical (and electron) density plugs and removable titanium implants was scanned on a Philips Brilliance Big Bore 16-slice CT simulator. The CT Hounsfield numbers of density plugs on both uncorrected and O-MAR corrected images were compared. Treatment planning accuracy was evaluated by comparing simulated dose distributions computed using the true density images, uncorrected images, and O-MAR corrected images. Ten CT image sets of patients with large hip implants were processed with the O-MAR function and evaluated by two radiation oncologists using a five-point score for overall image quality, anatomical conspicuity, and CT Hounsfield number accuracy. By utilizing the same structure contours delineated from the O-MAR corrected images, clinical IMRT treatment plans for five patients were computed on the uncorrected and O-MAR corrected images, respectively, and compared. Results: Results of the phantom study indicated that CT Hounsfield number accuracy and noise were improved on the O-MAR corrected images, especially for images with bilateral metal implants. The {gamma} pass rates of the simulated dose distributions computed on the uncorrected and O-MAR corrected images referenced to those of the true densities were higher than 99.9% (even when using 1% and 3 mm distance-to-agreement criterion), suggesting that dose distributions were clinically identical. In all patient cases, radiation oncologists rated O-MAR corrected images as higher quality. Formerly obscured critical structures were able to be visualized. The overall image quality and the conspicuity in critical organs were significantly improved compared with the uncorrected images: overall quality score (1.35 vs 3.25, P= 0.0022); bladder (2.15 vs 3.7, P= 0.0023); prostate and seminal vesicles/vagina (1.3 vs 3.275, P= 0.0020); rectum (2.8 vs 3.9, P= 0.0021). The noise levels of the selected ROIs were reduced from 93.7 to 38.2 HU. On most cases (8/10), the average CT Hounsfield numbers of the prostate/vagina on the O-MAR corrected images were closer to the referenced value (41.2 HU, an average measured from patients without metal implants) than those on the uncorrected images. High {gamma} pass rates of the five IMRT dose distribution pairs indicated that the dose distributions were not significantly affected by the CT image improvements. Conclusions: Overall, this study indicated that the O-MAR function can remarkably reduce metal artifacts and improve both CT Hounsfield number accuracy and target and critical structure visualization. Although there was no significant impact of the O-MAR algorithm on the calculated dose distributions, we suggest that O-MAR corrected images are more suitable for the entire treatment planning process by offering better anatomical structure visualization, improving radiation oncologists' confidence in target delineation, and by avoiding subjective density overrides of artifact regions on uncorrected images.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2014

SU-E-J-56: Dosimetric Impact of Patient Roll Variability in Peripheral-Lung SBRT

Purpose: Positional variation about the patient longitudinal axis may introduce deleterious effects to clinical treatment plans, the effects of which are exacerbated by hypo-fractionated treatment regimens. Our goal is to evaluate the dosimetric impact of rotational setup error in stereotactic body radiation therapy (SBRT) for peripherally-located lung lesions. Methods: Six patients who had been treated for peripheral lung lesions using varying SBRT techniques were analyzed. Each patient's planning CT was processed using custom in-house software to simulate 1, 3, and 5 degree roll in both directions about their longitudinal axis. The original plan was fused and re-calculated. Agreement between planned and error-simulated dose distributions was quantified using 3%, 3mm criteria for the 3-dimensional gamma metric, and changes in target coverage and adjacent normal anatomy were also quantified. Results: Increased rotational setup error resulted in reduced target coverage, with changes in equivalent uniform dose ranging from −1.24% to −6.11% for simulated roll greater than or equal to 3 degrees, increasing with magnitude of error and skewed for roll directed toward the involved side. Changes to normal tissue metrics are linearly related to simulated roll, with rib D(1cc) changes ranging from −4.23% to 3.27% relative to the original treatment plan. Error-simulated dose distributions demonstrate agreement by the gamma metric in the planned target of 72.56%, 81.02%, and 99.52% for 5, 3, and 1 degree simulated roll scenarios, respectively. Corresponding agreement for the regional dose in excess of 50% of the maximum were 65.71%,70.77%, and 97.88%. Conclusion: This study suggests that the ability to detect and compensate for rotational positioning variations beyond a threshold level may improve care for patients with peripherally-located lesions beyond that which may be accomplished using only translational axes. Positional error of one degree of roll had little influence, though three or more degrees of error introduced significant discrepancy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Fluid–Solid Coupling Simulation on the Temperature Distribution of Tuyere Used for Oxygen Bottom Blowing Converter

For an oxygen bottom blowing converter, a high-temperature fire spot zone forms above the tuyere owing to oxygen reaction. The bottom blowing tuyere and surrounding brick are simultaneously heated by high-temperature fire spot and flowing molten steel. High-speed fluids flowing in the inner tube and the annular gap of the tuyere can remove part of the heat transferred from the fire spot zone and molten steel, playing a vital role in cooling the tuyere. To determine the temperature distributions of the tuyere and surrounding brick under the condition of oxygen bottom blowing, a fluid–solid coupling heat transfer numerical model that considers both the radiation of the fire spot and convection of the molten steel was established in this study. The simulation results agree well with previous experimental results; thus, the numerical model was validated. Utilizing the validated model, the influences of the tuyere inner tube material and fire spot zone temperature on the tuyere temperature distribution were studied in detail. Along with an increase in the material thermal conductivity, the maximum temperature of the inner tube at the hot face decreased, verifying the superiority of copper as the inner tube. More importantly, it was found that reducing the fire spot zone temperature by mixing CO{sub 2} in the bottom blowing oxygen fundamentally alleviated the burning loss of the tuyere and the surrounding brick.

36 MATERIALS SCIENCE↗
DOE OSTI2011

A Distributed Electrochemistry Modeling Tool for Simulating SOFC Performance and Degradation

This report presents a distributed electrochemistry (DEC) model capable of investigating the electrochemistry and local conditions with the SOFC MEA based on the local microstructure and multi-physics. The DEC model can calculate the global current-voltage (I-V) performance of the cell as determined by the spatially varying local conditions through the thickness of the electrodes and electrolyte. The simulation tool is able to investigate the electrochemical performance based on characteristics of the electrode microstructure, such as particle size, pore size, electrolyte and electrode phase volume fractions, and triple-phase-boundary length. It can also investigate performance as affected by fuel and oxidant gas flow distributions and other environmental/experimental conditions such as temperature and fuel gas composition. The long-term objective for the DEC modeling tool is to investigate factors that cause electrode degradation and the decay of SOFC performance which decrease longevity.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2014

Investigating ice nucleation in cirrus clouds with an aerosol-enabled Multiscale Modeling Framework

In this study, an aerosol-dependent ice nucleation scheme [Liu and Penner, 2005] has been implemented in an aerosol-enabled multi-scale modeling framework (PNNL MMF) to study ice formation in upper troposphere cirrus clouds through both homogeneous and heterogeneous nucleation. The MMF model represents cloud scale processes by embedding a cloud-resolving model (CRM) within each vertical column of a GCM grid. By explicitly linking ice nucleation to aerosol number concentration, CRM-scale temperature, relative humidity and vertical velocity, the new MMF model simulates the persistent high ice supersaturation and low ice number concentration (10 to 100/L) at cirrus temperatures. The low ice number is attributed to the dominance of heterogeneous nucleation in ice formation. The new model simulates the observed shift of the ice supersaturation PDF towards higher values at low temperatures following homogeneous nucleation threshold. The MMF models predict a higher frequency of midlatitude supersaturation in the Southern hemisphere and winter hemisphere, which is consistent with previous satellite and in-situ observations. It is shown that compared to a conventional GCM, the MMF is a more powerful model to emulate parameters that evolve over short time scales such as supersaturation. Sensitivity tests suggest that the simulated global distribution of ice clouds is sensitive to the ice nucleation schemes and the distribution of sulfate and dust aerosols. Simulations are also performed to test empirical parameters related to auto-conversion of ice crystals to snow. Results show that with a value of 250 μm for the critical diameter, Dcs, that distinguishes ice crystals from snow, the model can produce good agreement to the satellite retrieved products in terms of cloud ice water path and ice water content, while the total ice water is not sensitive to the specification of Dcs value.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Enabling Smart Grid Cosimulation Studies: Rapid Design and Development of the Technologies and Controls

The 21st century electric power grid is transforming with an unprecedented increase in demand and increase in new technologies. In the United States Energy Independence and Security Act of 2007, Title XIII sets the tenets for modernizing the electricity grid through what is known as the 'Smart Grid Initiative.' This initiative calls for increased design, deployment, and integration of distributed energy resources, smart technologies and appliances, and advanced storage devices. The deployment of these new technologies requires rethinking and re-engineering the traditional boundaries between different electric power system domains.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2012

Thermal characteristics of air flow cooling in the lithium ion batteries experimental chamber

A battery pack prototype has been designed and built to evaluate various air cooling concepts for the thermal management of Li-ion batteries. The heat generation from the Li-Ion batteries was simulated with electrical heat generation devices with the same dimensions as the Li-Ion battery (200 mm x 150 mm x 12 mm). Each battery simulator generates up to 15W of heat. There are 20 temperature probes placed uniformly on the surface of the battery simulator, which can measure temperatures in the range from -40 C to +120 C. The prototype for the pack has up to 100 battery simulators and temperature probes are recorder using a PC based DAQ system. We can measure the average surface temperature of the simulator, temperature distribution on each surface and temperature distributions in the pack. The pack which holds the battery simulators is built as a crate, with adjustable gap (varies from 2mm to 5mm) between the simulators for air flow channel studies. The total system flow rate and the inlet flow temperature are controlled during the test. The cooling channel with various heat transfer enhancing devices can be installed between the simulators to investigate the cooling performance. The prototype was designed to configure the number of cooling channels from one to hundred Li-ion battery simulators. The pack is thermally isolated which prevents heat transfer from the pack to the surroundings. The flow device can provide the air flow rate in the gap of up to 5m/s velocity and air temperature in the range from -30 C to +50 C. Test results are compared with computational modeling of the test configurations. The present test set up will be used for future tests for developing and validating new cooling concepts such as surface conditions or heat pipes.

25 ENERGY STORAGE↗
DOE OSTI2011

Heat transfer simulation and thermal measurements of microfabricated x-ray transparent heater stages

A microfabricated amorphous silicon nitride membrane-based nanocalorimeter is proposed to be suitable for an x-ray transparent sample platform with low power heating and built-in temperature sensing. In this work, thermal characterization in both air and vacuum are analyzed experimentally and via simulation. Infrared microscopy and thermoreflectance microscopy are used for thermal imaging of the sample area in air. While a reasonably large isothermal area is found on the sample area, the temperature homogeneity of the entire sample area is low, limiting use of the device as a heater stage in air or other gases. A simulation model that includes conduction, as well as radiation and convection heat loss, is presented with radiation and convection parameters determined experimentally. Simulated temperature distributions show that the homogeneity can be improved by using a thicker thermal conduction layer or reducing the pressure of the gas in the environment but neither are good solutions for the proposed use. A new simple design that has improved temperature homogeneity and a larger isothermal area while maintaining a thin thermal conduction layer is proposed and fabricated. This new design enables applications in transmission x-ray microscopes and spectroscopy setups at atmospheric pressure.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Design of the HELICS High-Performance Transmission-Distribution-Communication-Market Co-Simulation Framework

This paper describes the design rationale for a new cyber-physical-energy co-simulation framework for electric power systems. This new framework will support very large-scale (100,000+ federates) co-simulations with off-the-shelf power-systems, communication, and end-use models. Other key features include cross-platform operating system support, integration of both event-driven (e.g. packetized communication) and time-series (e.g. power flow) simulation, and the ability to co-iterate among federates to ensure model convergence at each time step. After describing requirements, we begin by evaluating existing co-simulation frameworks, including HLA and FMI, and conclude that none provide the required features. Then we describe the design for the new layered co-simulation architecture.

24 POWER TRANSMISSION AND DISTRIBUTION↗