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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Quantum Solver Using Singular Value Decomposition for Computational Fluid Dynamics

Numerical solutions for fluid flow problems are challenging and have been focus of Computational Fluid Dynamics (CFD) research for past several decades. The advent of quantum computing promises exponential speedup in comparison to existing classical methods and alleviate computational constraints posed by CFD problems. Although solutions for most problems of interest in fluid dynamics using quantum computing are distant, recent advances in algorithms, software and hardware provide a path towards realizing this goal. Quantum linear solver algorithms (QLSA) such as Harrow–Hassidim–Lloyd (HHL) and Variational Quantum Linear Solver (VQLS) have been successfully implemented to solve for canonical problems such as Hele-Shaw flow. However, these algorithms still suffer to scale and address problems with ill-conditioned Jacobians. In the current paper, we alleviate these restrictions with a new quantum solver based on Singular Value Decomposition (SVD) and simulate flow past a 2D cylinder. The fidelity of the SVD based quantum solver in predicting the flow past 2D cylinder is computed along with an assessment of errors. Classical and quantum solutions for the flow are compared for different resolutions. Finally, we discuss variation in the solutions based on number of shots used.

Gottiparthi, Kalyan [ORNL] (ORCID:0000000213540255↗
DOE OSTI2014

Comparison of the Amanzi Model against Analytical Solutions and the FEHM Model

This file documents Amanzi code verification of flow simulations for three selected cases: (1) an infinite strip aquifer embedded between two other aquifers, (2) a heterogeneous cylinder (or disc in 2D case) embedded in a background aquifer, and (3) uniform aquifers in bounded domains with fixed heads at the upper- and down-stream directions and no-flow at lateral boundaries. The original FORTRAN codes that solve the analytical solutions for cases (1) and (2) were obtained from Greg Ruskauf. Two modifications were made for compilation on Linux systems: (a) The keyword ‘mode’ in OPEN statements was removed because it is not standard, and (b) variables in COMMON blocks were re-arranged to eliminate a warning message (padding of additional 4 bytes). These codes were compiled using the gfortran compiler on the Linux environment. Note that these analytical solutions were derived for two-dimensional problems only, and therefore in numerical simulations, we used three-dimensional domains with unit thickness for comparison.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Large Eddy Simulation of the Flow Behavior in a Simplified Helical Coil Steam Generator

Large eddy simulation (LES) is conducted for the flow over the shell side of a helical coil steam generator (HCSG) heat exchanger. Simulations are conducted on a simplified experimental test section that represents a one-column region of the helical coils using half-rods. Although the rods are wall-bounded, the flow still exhibits the turbulent characteristics and fluctuations from vortex shedding that one would expect from crossflow around a cylinder. The spectral element, computational fluid dynamics (CFD) code Nek5000, is used to capture the physics, and the results are compared with particle image velocimetry (PIV) measurements. In order to ensure that the turbulence is resolved, analysis is conducted by using the Taylor length scales and normalized wall distance. Sensitivity to the inlet boundary conditions (BCs) and the spatial discretization for different polynomial order solutions are also studied, finding only minor differences between each case. Pressure drop and velocity statistics show reasonable agreement with PIV. Proper orthogonal decomposition (POD) analysis reveals that the primary modes are similar between experiment and simulation, although the LES predicts higher turbulent kinetic energy than does PIV. Overall, the study establishes the resolution and resources required in order to conduct a high-fidelity simulation over 12 helical rods.

Lai, Jonathan K.↗
DOE OSTI2017

Hierarchical Engine for Large-scale Infrastructure Co-Simulation

HELICS is designed to support very-large-scale (100,000+ federates) cosimulations with off-the-shelf power-system, communication, market, and end-use tools. Other key features include cross platform operating system support, the integration of both event driven (e.g., packetized communication) and time-series (e.g., power flow) simulations, and the ability to co-iterate among federates to ensure physical model convergence at each time step.

Source record↗
DOE OSTI2017

Hierarchical Engine for Large-scale Infrastructure Co-Simulation

HELICS is designed to support very-large-scale (100,000+ federates) cosimulations with off-the-shelf power-system, communication, market, and end-use tools. Other key features include cross platform operating system support, the integration of both event driven (e.g., packetized communication) and time-series (e.g., power flow) simulations, and the ability to co-iterate among federates to ensure physical model convergence at each time step.

Source record↗
NASA NTRS1989

Numerical Solution Of Navier-Stokes Equations

Three-dimensional, incompressible flow simulated on computer. Report discusses mathematical basis of IN3SD computer code and application of code to several test problems. Relies heavily on use of pseudocompressibility to solve numerically three-dimensional Navier-Stokes equations of viscous, incompressible flow. With further study and some modification, valuable computational tool for solution of engineering problems in fluid dynamics.

Rogers, Stuart E.↗
NASA NTRS2012

AdapChem

AdapChem software enables high efficiency, low computational cost, and enhanced accuracy on computational fluid dynamics (CFD) numerical simulations used for combustion studies. The software dynamically allocates smaller, reduced chemical models instead of the larger, full chemistry models to evolve the calculation while ensuring the same accuracy to be obtained for steady-state CFD reacting flow simulations. The software enables detailed chemical kinetic modeling in combustion CFD simulations. AdapChem adapts the reaction mechanism used in the CFD to the local reaction conditions. Instead of a single, comprehensive reaction mechanism throughout the computation, a dynamic distribution of smaller, reduced models is used to capture accurately the chemical kinetics at a fraction of the cost of the traditional single-mechanism approach.

Oluwole, Oluwayemisi O.↗
NASA NTRSDate not supplied

Simulations of the Modular Axisymmetric Scramjet Test Rig Under Reacting Flow Conditions

Simulations of the Air Force Research Laboratory (AFRL) Modular Axisymmetric Scramjet Test Rig (MASTeR) are presented. MASTeR is a parametric test article capable of investigating various scramjet cavity flameholder designs and fueling strategies with the goal to characterize and optimize flameholding capability. In the current work, three cavity aspect ratios, three depths, and two fueling strategies (upstream and in-cavity) with ethylene at a nominal facility pressure and temperature conditions are evaluated. The simulations are performed for mixing-only and reacting flows, and the resulting flow characteristics are compared. For each configuration and fueling strategy, cavity residence time, entrainment rate, and fuel-air equivalence ratio are computed. The MASTeR geometry is defined in the Engineering Sketch Pad (ESP) and the simulations use a sketch-to-solution (S2S) automated unstructured grid adaptation tool in VULCAN-CFD. This tool automatically generates a simulation grid from the ESP geometry and systematically adapts it to the numerical solution based on the Hessian error estimate of a specified flow field parameter. Reynolds averaged simulations (RAS) are used with typical two-equation linear eddy viscosity and diffusivity model. The resulting database can be compared with the experimental data as those becomes available and explored to develop models for cavity performance for scramjet propulsion design applications.

hypersonics↗
DOE OSTI2019

Exploratory Research: Transport and Transformation of Particulate Organic Matter in Permeable River Sediments

The hyporheic zone (HZ) is the volume of streambed sediments where surface water and groundwater mix. The mixing of ground and surface water geochemical constituents including organic matter and the presence of large microbial populations create an important location for biogeochemical activity. Large and periodic fluctuations in river stage such as those associated with operation of hydroelectric dams, may enhance downstream hyporheic exchange by reversing the direction of flow to/from the stream on a regular basis. Solute transport in hyporheic zones is affected by river regulation; however, little is known about the transport of particulate organic matter (POM) under these conditions. We performed a laboratory experiment to simulate the transport and retention of POM under conditions simulating flow reversal in the hyporheic zone. Here, POM is created by inoculating artificial river water with algae obtained from the Hanford Reach of the Columbia River. POM transport experiments are then conducted in columns packed with sandy sediments; these data are then used to calibrate a model describing fundamental processes controlling its transport in saturated sediments. Models results reveal that filtration, sorption to sediment, and sorption to previously retained POM are important mechanisms of POM retention in sandy, saturated sediments. Additionally, upon flow direction reversal, POM is readily mobilized leading to effluents concentrations above the initial input concentrations. These findings indicate that river stage changes may change POM storage in the hyporheic zone depending on the type and magnitude of flow variation.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2001

Designing Adaptive Low-Dissipative High Order Schemes for Long-Time Integrations

A general framework for the design of adaptive low-dissipative high order schemes is presented. It encompasses a rather complete treatment of the numerical approach based on four integrated design criteria: (1) For stability considerations, condition the governing equations before the application of the appropriate numerical scheme whenever it is possible; (2) For consistency, compatible schemes that possess stability properties, including physical and numerical boundary condition treatments, similar to those of the discrete analogue of the continuum are preferred; (3) For the minimization of numerical dissipation contamination, efficient and adaptive numerical dissipation control to further improve nonlinear stability and accuracy should be used; and (4) For practical considerations, the numerical approach should be efficient and applicable to general geometries, and an efficient and reliable dynamic grid adaptation should be used if necessary. These design criteria are, in general, very useful to a wide spectrum of flow simulations. However, the demand on the overall numerical approach for nonlinear stability and accuracy is much more stringent for long-time integration of complex multiscale viscous shock/shear/turbulence/acoustics interactions and numerical combustion. Robust classical numerical methods for less complex flow physics are not suitable or practical for such applications. The present approach is designed expressly to address such flow problems, especially unsteady flows. The minimization of employing very fine grids to overcome the production of spurious numerical solutions and/or instability due to under-resolved grids is also sought. The incremental studies to illustrate the performance of the approach are summarized. Extensive testing and full implementation of the approach is forthcoming. The results shown so far are very encouraging.

Yee, Helen C.↗
DOE OSTI2022

TOUGH3-FLAC3D: a modeling approach for parallel computing of fluid flow and geomechanics

The recent development of the TOUGH3 code allows for a faster and more reliable fluid flow simulator. At the same time, new versions of FLAC3D are released periodically, allowing for new features and faster execution. In this paper, we present the first implementation of the coupling between TOUGH3 and FLAC3Dv6/7, maintaining parallel computing capabilities for the coupled fluid flow and geomechanical codes. We compare the newly developed version with analytical solutions and with the previous approach, and provide some performance analysis on different meshes and varying the number of running processors. Finally, we present two case studies related to fault reactivation during CO 2 sequestration and nuclear waste disposal. The use of parallel computing allows for meshes with a larger number of elements, and hence more detailed understanding of thermo-hydro-mechanical processes occurring at depth.

58 GEOSCIENCES↗
NASA NTRS2018

Generating a Grid for Unstructured RANS Simulations of Jet Flows

A study has been performed to determine best practices for generating unstructured grids for Reynolds-Averaged Navier-Stokes (RANS) simulations of jet flows. The Axisymmetric Near-Sonic Jet Case from the Turbulence Modeling Resource was used for this study: a Mach 0.985 flow through the 2-in. diameter Acoustic Reference Nozzle (ARN2). Simulations were run with FUN3D and used the Menter Shear Stress Transport (SST-V), Spalart-Allmaras (S-A), and k-kL turbulence models. The axial velocity and turbulent kinetic energy fields in the jet plume of the unstructured grid solutions were compared to those of the baseline structured grid solution provided by the Turbulence Modeling Resource. Only solutions using grids with structured-like elements in the jet plume showed good agreement with the baseline structured grid solution. Using the SST-V turbulence model, the fully unstructured grid solutions predicted the jet potential core to decay upstream of the baseline solution. With the S-A turbulence model, the unstructured grid solutions predicted the jet potential core to decay upstream of the baseline solution. The solutions using the k-kL turbulence model seemed less sensitive to grid topology. Nozzle massflow and thrust performance were also compared for all simulations. Based on the results of this study, it is currently recommended that structured-like grid elements are used in the plumes of jet flows; unstructured grid elements can be used elsewhere.

RANS Simulations; Unstructured Grids; Jet Flows↗
DOE OSTI2017

Numerical studies of CO 2 and brine leakage into a shallow aquifer through an open wellbore

Industrial-scale geological storage of CO 2 in saline aquifers may cause CO 2 and brine leakage from abandoned wells into shallow fresh aquifers. This leakage problem involves the flow dynamics in both the wellbore and the storage reservoir. T2Well/ECO2N, a coupled wellbore-reservoir flow simulator, was used to analyze CO 2 and brine leakage under different conditions with a hypothetical simulation model in water-CO 2 -brine systems. Parametric studies on CO 2 and brine leakage, including the salinity, excess pore pressure (EPP) and initially dissolved CO 2 mass fraction, are conducted to understand the mechanism of CO 2 migration. The results show that brine leakage rates increase proportionally with EPP and inversely with the salinity when EPP varies from 0.5 to 1.5 MPa; however, there is no CO 2 leakage into the shallow freshwater aquifer if EPP is less than 0.5 MPa. The dissolved CO 2 mass fraction shows an important influence on the CO 2 plume, as part of the dissolved CO 2 becomes a free phase. Scenario simulation shows that the gas lifting effect will significantly increase the brine leakage rate into the shallow freshwater aquifer under the scenario of 3.89% dissolved CO 2 mass fraction. The equivalent porous media (EPM) approach used to model the wellbore flow has been evaluated and results show that the EPM approach could either under- or over-estimate brine leakage rates under most scenarios. The discrepancies become more significant if a free CO 2 phase evolves. Therefore, a model that can correctly describe the complex flow dynamics in the wellbore is necessary for investigating the leakage problems.

58 GEOSCIENCES↗
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↗
NASA NTRS1975

Coaxial injector response to axial instability under simulated cold-flow

The frequency dependence of the admittances and response factors of various gaseous rocket injector configurations subject to axial instabilities under cold-flow conditions, have been measured using the modified impedance-tube technique. The tested configurations simulate the flows in a gaseous-fuel injector, gaseous-oxidizer injector and a coaxial injector with both fuel and oxidizer elements. Comparison of the measured response data with corresponding data predicted by the Feiler and Heidmann model indicates good agreement between the two sets of data.

Janardan, B. A.↗
DOE OSTI2017

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

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↗
DOE OSTI2025

Numerical analysis of gas exhaust in Wendelstein 7-X using the direct simulation Monte Carlo method

The present work is focused on a 3D numerical assessment of the Wendelstein 7-X (W7-X) particle exhaust. For all the numerical simulations the direct simulation Monte Carlo solver of the DIVGAS workflow, has been employed. The complex 3D geometry of the sub-divertor region includes the pumping gap panel, supporting structures, cooling pipes as well as the cryo-vacuum pump. All the considered flow simulations correspond to the Standard magnetic configuration of W7-X. The main conclusions, which can be extracted from the present numerical analysis could be summarized as follows; The coupling between EMC3-EIRENE and DIVGAS, which considers the fact that the incoming neutral particle flux at the sub-divertor is based on realistic plasma background, has been demonstrated. Three plasma scenarios have been considered, for which is clearly seen that by increasing the heating power, the neutral pressure as well as the resulting pumping efficiency is increased. The obtained numerical results of the neutral pressure in the sub-divertor lie within a more general scan matrix, which assumes a wider range of incoming particle flux, namely 10 19 –10 24 (s −1 ). It has been observed that, the sub-divertor neutral pressure is proportional to the incoming neutral particle flux, with the effective pumping speed to be a constant of proportionality. The influence of switching off the cryo-vacuum pump on the sub-divertor pressure is rather modest and a weak increase of the neutral pressure in the sub-divertor is expected. Correlations of the sub-divertor pressure with the total incoming particle flux as well as the individual pumped flux at each of the AEH and AEP sections have been deduced. Moreover, it has been demonstrated that the influence of the incoming neutral particle flux on the albedo coefficient at the AEH and AEP pumping gaps is rather weak. All the above numerical findings will actively support the optimization of the W7-X particle exhaust, in view of future experimental campaigns.

DSMC method↗
DOE OSTI2020

The Sealing Mechanisms of a Fracture in Opalinus Clay as Revealed by in situ Synchrotron X-Ray Micro-Tomography

The detailed mechanisms of the sealing of a single fracture, from hydration to almost complete closure by increase of confining pressure, as monitored from in situ synchrotron X-ray microtomography during the flow of carbonated water, is here shown for the first time. Different mechanisms play the key role at different stages in the evolution of the fracture. Hydration mechanically weakens the surfaces of the fracture and induces a first closure due to microcracking at the asperity contacts, increasing their size and creating choke points. Increase in confining stress promptly hydraulically seals the fracture by closing the main choke point, with a relative small deformation of the sample. Finally, the more pervasive mechanical deformation observed at higher stresses almost completely seals the whole fracture. The evolution of the sample has been described and quantified using 4D image processing, focusing on the evolution of aperture and digital volume correlation. Hydraulic properties of the sample at different stages have been modeled via Stokes flow simulation, and the results compared to the morphometric analysis, finding positive correlations with the average fracture aperture variation along the flowpath in function of confining pressure. Opalinus Clay is found to be a rock markedly prone to sealing in case of flow with carbonated water; this behavior is the result of the large fraction of clays and of its microstructure, lacking both cementing phases and large stiff particles. CO2 in this sample has no evident role in the evolution of the fracture; chemically induced weathering on the surface has not been detected, in contrast with the behavior observed in samples with carbonates as cementing phase.

58 GEOSCIENCES↗