Search NASA⌕ Search

SEARCH · Search NASA

Results for “Application Models”

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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

A Visual Comparison of Silent Error Propagation

High-performance computing (HPC) systems play a critical role in facilitating scientific discoveries. Their scale and complexity (e.g., the number of computational units and software stack) continue to grow as new systems are expected to process increasingly more data and reduce computing time. However, with more processing elements, the probability that these systems will experience a random bit-flip error that corrupts a program's output also increases, which is often recognized as silent data corruption. Analyzing the resiliency of HPC applications in extreme-scale computing to silent data corruption is crucial but difficult. An HPC application often contains a large number of computation units that need to be tested, and error propagation caused by error corruption is complex and difficult to interpret. Here, to accommodate this challenge, we propose an interactive visualization system that helps HPC researchers understand the resiliency of HPC applications and compare their error propagation. Our system models an application's error propagation to study a program's resiliency by constructing and visualizing its fault tolerance boundary. Coordinating with multiple interactive designs, our system enables domain experts to efficiently explore the complicated spatial and temporal correlation between error propagations. At the end, the system integrated a nonmonotonic error propagation analysis with an adjustable graph propagation visualization to help domain experts examine the details of error propagation and answer such questions as why an error is mitigated or amplified by program execution.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Lagrangian and Eulerian Supersaturation Statistics in Turbulent Cloudy Rayleigh–Bénard Convection: Applications for LES Subgrid Modeling

Abstract Turbulent fluctuations of scalar and velocity fields are critical for cloud microphysical processes, e.g., droplet activation and size distribution evolution, and can therefore influence cloud radiative forcing and precipitation formation. Lagrangian and Eulerian water vapor, temperature, and supersaturation statistics are investigated in direct numerical simulations (DNS) of turbulent Rayleigh–Bénard convection in the Pi Convection Cloud Chamber to provide a foundation for parameterizing subgrid-scale fluctuations in atmospheric models. A subgrid model for water vapor and temperature variances and covariance and supersaturation variance is proposed, valid for both clear and cloudy conditions. Evaluation of phase change contributions through an a priori test using DNS data shows good performance of the model. Supersaturation is a nonlinear function of temperature and water vapor, and relative external fluxes of water vapor and heat (e.g., during entrainment-mixing and phase change) influence turbulent supersaturation fluctuations. Although supersaturation has autocorrelation and structure functions similar to the independent scalars (temperature and water vapor), the autocorrelation time scale of supersaturation differs. Relative scalar fluxes in DNS without cloud make supersaturation PDFs less skewed than the adiabatic case, where they are highly negatively skewed. However, droplet condensation changes the PDF shape response: it becomes positively skewed for the adiabatic case and negatively skewed when the sidewall relative fluxes are large. Condensation also increases correlations between water vapor and temperature in the presence of relative scalar fluxes but decreases correlations for the adiabatic case. These changes in correlation suppress supersaturation variability for the nonadiabatic cases and increase it for the adiabatic case. Implications of this work for subgrid microphysics modeling using a Lagrangian stochastic scheme are also discussed.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Development and Application of Preliminary TOGA Model for CO 2 -EOR with Comparison to Resistivity Data

A new TOUGH code, TOGA (Transport of Oil, Gas, Aqueous), is used to model enhanced oil recovery (EOR) from a South Texas field where a combination of water, CO 2 , and WAG (water-alternating-gas) injection wells are located in the down-dip region of a fault block, with oil and natural gas production occurring from wells located up-dip. The reservoir is composed of interlayered sands and shales at a depth of about 2000 m. TOGA considers three fluid phases (oil, gas, and aqueous), and multiple components. Oil field data including compositional analysis of stock-tank oil, gas-oil ratio, and gas gravity are used to determine the composition of oil and gas phases. Initial conditions for aqueous saturation are determined from a depth to surface resistivity survey conducted prior to the onset of CO 2 injection and Archie’s Law. Simulation results after several years of EOR operations are then converted back to resistivity maps and compared to images created by time-lapse depth-to-surface resistivity surveys. These surveys show a strong increase in resistivity, interpreted as the replacement of aqueous phase by injected CO 2 . In contrast, preliminary TOGA results show that injected CO 2 displaced more oil than water, suggesting that the three-phase relative permeability curves used to describe the interference of fluid phases need to be modified. Limited information on the composition of produced fluids provides another data set for comparison with model results. Model variations including using different relative permeability curve parameters and WAG cycle durations yielded improved model matches to the field data. The practical simplifications needed to simulate an actual operating oil field and the limited amount of field operation data available preclude using the present model to get an accurate history match or to make detailed predictions. Rather, the modeling is intended to illustrate the general trends occurring during CO 2 -EOR and to indicate where more detailed information is needed.

02 PETROLEUM↗
DOE OSTI2021

“Experimental investigation of the governing parameters of atmospheric ice nucleation using field-collected and laboratory generated aerosol particles and its application in cloud resolving models” (Final Report)

The objective of this research project is to improve our understanding of the role of aerosol particles acting as ice-nucleating particles (INPs) which in turn define the mixed-phase and cirrus cloud radiative properties and thus climate. The focus is placed on how the physicochemical particle population properties determine the particles’ ability to initiate ice nucleation. This research project combined micro-spectroscopic particle analysis, experimental ice nucleation studies, and model sensitivity studies to advance our predictive capability of the formation of mixed-phase and cirrus clouds. These project activities have led to new ice nucleation data from laboratory generated and ambient (authentic) aerosol particles furthering process-level understanding, insights in the role of organic aerosol in ice formation, and advancements in the interpretation and parameterization of ice nucleation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Application of Process Chemical Modeling to Optimize Radioactive Waste Disposal at the Savannah River Site - 24242

The Technical Optimization Model (TOM) is used by Savannah River Mission Completion (SRMC) to carry out facility-wide material balance and validate chemistrydependent processes for the purpose of their System Plan.The TOM simulates material movement and chemical reactions at the Tank Farm (TF), Salt Waste Processing Facility (SWPF) and Defense Waste Processing Facility (DWPF).

Georgiou, Andreas↗
NASA NTRS1974

Application of infrared line models in the detection of atmospheric pollutants

The total absorptions of the three line profiles, Lorentz, Doppler, and Voight, are compared for a range of intervening parameters. It is found that, for the intermediate path lengths, the use of the combined Lorentz-Doppler (Voight) line profile is essential in calculating the atmospheric transmittance. The line-by-line model transmittance expression is incorporated in the atmospheric radiative flux equation. This equation, in turn, is utilized to determine the pollutant concentration in the atmosphere from the data obtained by the radiation measurement from an aircraft- or satellite-mounted instrument.

Tiwari, S. N.↗
NASA NTRS1977

Applications of Suits spectral model to wheat

Canopy reflectance calculations for a spring type Mexican wheat, Penjamo, are compared with published data on Scout winter wheat. Good agreement exists between model calculations and experimental data in the spectral range, 500 nm to 750 nm, suggesting that the model parameters for wheat can be applied to different cultivars of wheat in the same growth stage. Wheat canopy reflectance is dependent upon surface soil type and this dependency is examined with the Suits' spectral model. In this particular growth stage wheat reflectance is shown to be nearly independent of soil reflectance in the visible wavelengths and progressively dependent at longer wavelengths in the infrared.

Chance, J. E.↗
NASA NTRS1977

Applications of infrared band model correlations to nongray radiation

Various correlations for the total absorptance of a wide band are presented. These are employed in two physically realistic problems (radiative transfer in gases with internal heat source and heat transfer in laminar flow of absorbing-emitting gasses between parallel plates) to study their influence on final radiative transfer results.

Tiwari, S. N.↗