Search NASA⌕ Search

SEARCH · Search NASA

Results for “Modelling”

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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Final Report: Modeling coupled ice sheet-ocean interactions in the Model for Prediction Across Scales (MPAS) and in DOE Earth System Models

Ice sheet-ocean interactions are involved in a potential climate tipping point in the climate system. Weakening of dynamical ocean barriers that currently hold warmer waters off the Antarctic continental shelf could lead to warming under Antarctica’s largest ice shelves, causing as much as a hundredfold increase in sub-ice-shelf melting. Increased ice-sheet melting could trigger dynamical instabilities in the ice sheet itself if sufficient buttressing from ice shelves is lost. This project developed and tested several modeling capabilities needed to investigate these phenomena. In collaboration with a number of international groups, notably the climate modeling group at Los Alamos National Laboratory (LANL), the following capabilities were added to the Energy Exascale Earth System Model (E3SM) and its ocean component (the Model for Prediction Across Scales Ocean, MPAS-Ocean): 1) a new vertical coordinate appropriate for ice-shelf cavities; 2) an initialization procedure appropriate for damping waves from imbalances in ocean pressure and that of the overlying ice shelf; 3) A suite of idealized test cases related to ice shelf-ocean interactions; 4) A set of diagnostics for tracking freshwater fluxes and heat budgets from ice-shelf melting; 5) infrastructure for computing ice sheet-ocean fluxes in the E3SM coupler; and 6) A set of analysis and visualization tools for E3SM ocean and sea-ice validation with a particular focus on Antarctic and Southern Ocean climate. Additionally, the project included participation and leadership in a number of international model intercomparison projects (MIPs). Most notably, the PI was a co-chair of the Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP), designing the experiment, coordinating participation in the MIP and performing the bulk of the analysis. Although the project was cut short when the PI accepted a staff scientist position at LANL, the project played a role in seven publications and has segued smoothly into ongoing Department of Energy projects in the “ecosystem” surrounding E3SM.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Hierarchical calibration and validation for modeling bench-scale solvent-based carbon capture. Part 1: Non-reactive physical mass transfer across the wetted wall column

A hierarchical model calibration and validation are proposed here for quantifying the confidence level of mass transfer prediction using a computational fluid dynamics (CFD) model, where the solvent-based carbon dioxide (CO 2 ) capture is simulated and the predicted results are compared to the corresponding bench-scale experimental data. Two unit problems with an increasing level of complexity are proposed to break down the complex physical/chemical processes of solvent-based CO 2 capture into relatively simpler problems to separate the effects of physical transport and chemical reaction. This paper focuses on the calibration and validation of the first unit problem, i.e., the CO 2 mass transfer across a falling ethanolamine (MEA) film in the absence of chemical reaction. This problem is investigated both experimentally and numerically using non-reactive nitrous oxide (N 2 O) as a surrogate for CO 2 . To capture motion of the gas-liquid interface, a volume of fluid method is employed with a one-fluid formulation to compute the mass transfer between the two phases. Parallel bench-scale experiments are designed and conducted to validate and calibrate the CFD models using a general Bayesian calibration approach. Two important transport parameters, Henry's constant and gas diffusivity, are calibrated to produce the posterior distributions, which will be used as input for the second unit problem to address the chemical absorption of CO 2 across the MEA falling film, where both mass transfer and chemical reaction are involved. Finally, mass transfer coefficients predicted by CFD are also compared with those predicted by the traditional/empirical correlations under both steady and wavy falling film conditions.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1990

Model-based estimation of wind fields over the ocean from wind scatterometer measurements. I - Development of the wind field model. II - Model parameter estimation

Techniques for the determination of near-surface mesoscale ocean wind fields on the basis of satellite scatterometer data are developed and demonstrated. The derivation of normal-boundary and parameterized-boundary-condition (PBC) wind-field models is outlined, and results from a simulation performed to estimate the model errors are presented in tables. It is shown that the PBC model provides accurate results while minimizing the number of unknowns. After a review of the principles of scatterometry and an analysis of scatterometer measurement noise, an objective function for the measurement parameters is developed and optimized on the basis of gradient search with initial values computed from pointwise wind estimates. The model is then applied to data from a simulation of the NASA Scatterometer (Li et al., 1984), and the results are presented in extensive graphs. The feasibility of model-based wind-field estimation and the appropriateness of the PBC model are demonstrated.

Long, David G.↗
DOE OSTI2024

From minimum-viable-products to full models: a step-wise development of diagnostic forward models in support of design, analysis and modelling on the ST40 tokamak

Like most magnetic confined fusion experiments, the ST40 tokamak started off with a small subset of diagnostics and gradually increased the diagnostic set to include more complex and comprehensive systems. To make the most of each operational phase, forward models of various diagnostics are used and developed to aid design, provide consistency-checks during commissioning, test analysis methods, and build workflows to constrain high-level parameters to inform interpretation, theory and modelling. For new models and new analysis workflows, minimum-viable-products are released early, and their complexity is increased in a step-wise manner, facilitating the support of all programme phases on multiple parallel applications, while enabling learning opportunities and feedback loops. In this contribution we review the philosophy, scope and architecture of the framework under development. We discuss the details of some forward models, with examples on how they are used to aid diagnostic design, to investigate analysis methodologies through synthetic data, and how they are embedded in experimental analysis workflows. We compare previously published experimental results with new, more advanced analysis workflows employing more recent, detailed models and new diagnostic data, providing confirmation of the published material from the 2021–22 experimental campaign.

integrated data analysis↗
NASA NTRS1987

A numerical modeling study of a Montana thunderstorm. I - Model results versus observations involving nonelectrical aspects. II - Model results versus observations involving electrical aspects

Model results and the observed cloud behavior are examined in terms of nonelectrical and electrical aspects of a thunderstorm. The characteristics of the two-dimensional, time-dependent atmospheric electricity model used to simulate the cloud observations of July 19, 1981 in Miles City, Montana are described. The interactions of the dynamics and microphysics of the cloud with the charge separation mechanisms are analyzed. It is observed that the model accurately represents many of the observed characteristics of the cloud; however, the cloud base height, maximum liquid water content, and the time from first formation of precipitation until it reaches the ground are not accurately modeled. It is found that the model adequately represents the electrical field structure of the cloud and the electrical field strengths.

Helsdon, John H., Jr.↗
NASA NTRS1954

Wind-Tunnel Investigation of the Effects on the Aerodynamic Characteristics of Modifications to a Model of a Bomb Mounted on a Wing-Fuselage Model and to a Model of the Bomb Alone

An investigation was conducted in the Langley high-speed 7- by 10-foot tunnel to determine effects of modifications to a bomb model (particularly with regard to drag) when mounted on a wing-fuselage model and tested at Mach numbers from 0.70 to 1.10. In addition, the static longitudinal stability characteristics of several configurations of a larger scale model of the bomb alone were obtained over a Mach number range from 0.50 to 0.95. The results obtained for the wing-fuselage-bomb model indicate that large reductions in installation drag were obtained for the wing-fuselage-bomb model when the flat nose of the basic bomb was replaced by rounded or pointed noses of various calibers. Shortening the mounting pylon gave further decreases in the installation drag. The tests of the bomb alone indicated that only the flat-nose configurations were stable over the greater part of the Mach number range. Nose-shape modifications which improved the drag also caused the bombs to become unstable at low angles of attack. The stability of the low-drag bomb configurations could be improved by lengthening the cylindrical portion of the body behind the center of gravity.

King, Thomas J., Jr.↗
DOE OSTI2024

Modeling the Effects of Artificial Drainage on Agriculture-dominated Watersheds using a Fully Distributed Integrated Hydrology Model: Datasets, code, models files

This model-data archive is for a modeling study focused on the effects of artificial drainage on agriculture-dominated watersheds using a fully distributed integrated hydrology model. This study introduced a novel strategy to represent the effects of tile drains and agricultural ditches in a fully distributed basin-scale integrated hydrology model. The numerical experiments in this study reveal the effects of surface and subsurface drainage on various hydrological states and fluxes. The details about the datasets can be found in the "readme" document attached with the dataset.

Agricultural Watersheds↗
DOE OSTI2017

Capturing the two-way hydromechanical coupling effect on fluid-driven fracture in a dual-graph lattice beam model

Fluid-driven fractures of brittle rock is simulated via a dual-graph lattice model. The new discrete hydromechanical model incorporates a two-way coupling mechanism between the discrete element model and the flow network. Through adopting an operator-split algorithm, the coupling model is able to replicate the transient poroelasticity coupling mechanism and the resultant Mandel-Cryer hydromechanical coupling effect in a discrete mechanics framework. As crack propagation, coalescence and branching are all path-dependent and irreversible processes, capturing this transient coupling effect is important for capturing the essence of the fluid-driven fracture in simulations. Injection simulations suggest that the onset and propagation of fractures is highly sensitive to the ratio between the injection rate and the effective permeability. Moreover, we show that in a permeable rock, the borehole breakdown pressure, the pressure at which fractures start to grow from the borehole, depends on both the given ratio between injection rate and permeability and the Biot coefficient.

58 GEOSCIENCES↗
DOE OSTI2017

Influence of multi-species solute transport on modeling of hydrated Portland cement leaching in strong nitrate solutions

The differences between the predictions of Fickian diffusion and Nernst-Planck electro-diffusion based reactive transport models are investigated in the context of an important practical problem – leaching of Portland cement in strong nitrate porewater solutions under saturated conditions. Numerical results are presented for three distinct porewater solutions: deionized water, ammonium nitrate solution, and diluted porewater from a cementitious low-activity nuclear waste form. Solute concentrations predicted by the two transport models show significant differences: as much as a factor of two for ammonium nitrate leaching and as much as a factor of four for waste form leaching; whereas, negligible differences are observed for deionized water leaching. The major conclusion is that Fickian diffusion may be accurate enough for deionized water leaching, but electro-diffusion should be considered in the reactive solute transport modeling of ammonium nitrate decalcification and in the degradation modeling of cementitious materials exposed to nuclear waste form solutions.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1984

Inversion of vegetation canopy reflectance models for estimating agronomic variables. III - Estimation using only canopy reflectance data as illustrated by the suits model. IV - Total inversion of the SAIL model

The possibility of estimating agronomic and spectral parameters for a vegetation canopy from the canopy reflectance (CR) data in the infrared region is investigated for a set of solar/view directions. It is shown that such an estimation is possible, in principle, for the Suits (1972) model for a homogeneous canopy. The technique is then applied to a more complex model, the SAIL (scattering by arbitrarily inclined leaves) model which explicitly includes the leaf angle distribution in the computation of the canopy reflectance. It is concluded that, given the expected accuracy of CR measurements and the accuracy of the SAIL model in representing CR in the infrared region, the agronomic parameters, leaf area index, and leaf angle distribution can be estimated fairly accurately using ancillary data on spectral parameters.

Goel, N. S.↗