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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 1,747 records · Page 97
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Spatial Variation of Methane and Other Trace Gases Detected on Mars: Interpretation with a General Circulation Model

Several teams have recently reported the detection of methane in the Martian atmosphere [1-3]. Although the detection is at the limit of the instrument capacities, one of the most surprising findings by some of these teams is the apparent strong spatial variations observed in spite of the fact that a gas like methane was expected to have a relatively long lifetime in the Martian atmosphere and thus be well mixed. To better quantitatively understand how such spatial variations can form on Mars, we have performed multiple realistic 3D general circulation model simulations in which gases with different sources, lifetime or sinks are released and transported in the Martian atmosphere.

Forget, F.↗
NASA NTRS2007

Three-Dimensional Navier-Stokes Calculations Using the Modified Space-Time CESE Method

The space-time conservation element solution element (CESE) method is modified to address the robustness issues of high-aspect-ratio, viscous, near-wall meshes. In this new approach, the dependent variable gradients are evaluated using element edges and the corresponding neighboring solution elements while keeping the original flux integration procedure intact. As such, the excellent flux conservation property is retained and the new edge-based gradients evaluation significantly improves the robustness for high-aspect ratio meshes frequently encountered in three-dimensional, Navier-Stokes calculations. The order of accuracy of the proposed method is demonstrated for oblique acoustic wave propagation, shock-wave interaction, and hypersonic flows over a blunt body. The confirmed second-order convergence along with the enhanced robustness in handling hypersonic blunt body flow calculations makes the proposed approach a very competitive CFD framework for 3D Navier-Stokes simulations.

Chang, Chau-lyan↗
NASA NTRS2014

Applying Motion Constraints Based on Test Data

MSC ADAMS is a simulation software that is used to analyze multibody dynamics. Using user subroutines, it is possible to apply motion constraints to the rigid bodies so that they match the motion profile collected from test data. This presentation describes the process of taking test data and passing it to ADAMS using user subroutines, and uses the Morpheus free-flight 4 test as an example of motion data used for this purpose. Morpheus is the name of a prototype lander vehicle built by NASA that serves as a test bed for various experimental technologies (see backup slides for details) MSC.ADAMS"TM" is used to play back telemetry data (vehicle orientation and position) from each test as the inputs to a 6-DoF general motion constraint (details in backup slides) The MSC.ADAMS"TM" playback simulations allow engineers to examine and analyze flight trajectory as well as observe vehicle motion from any angle and at any playback speed. This facilitates the development of robust and stable control algorithms, increasing reliability and reducing development costs of this developmental engine The simulation also incorporates a 3D model of the artificial hazard field, allowing engineers to visualize and measure performance of the developmental autonomous landing and hazard avoidance technology ADAMS is a multibody dynamics solver. It uses forces, constraints, and mass properties to numerically integrate equations of motion. The ADAMS solver will ask the motion subroutine for position, velocity, and acceleration values at various time steps. Those values must be continuous over the whole time domain. Each degree of freedom in the telemetry data can be examined separately; however, linear interpolation of the telemetry data is invalid, since there will be discontinuities in velocity and acceleration.

Burlone, Michael↗
NASA NTRS2019

Venus Topography and Boundary Conditions in 3D General Circulation Modeling

We describe how one ingests 3D topographic data from NASA's Venus Magellan Spacecraft radar observations into the ROCKE-3D Planetary General Circulation Model. We also explain how boundary condition choices such as ocean/lake coverage/depth, rotation rate, atmospheric constituents, and other factors influence surface conditions in ROCKE-3D paleo-Venus simulations. Studies such as these should also be considered when examining liquid water habitability in similar exoplanet experiments.

topography↗
NASA NTRS2019

Enhanced Habitability on High Obliquity Bodies near the Outer Edge of the Habitable Zone of Sun-Like Stars

High obliquity planets represent potentially extreme limits of terrestrial climate, as they exhibit large seasonality, a reversed annual-mean pole-to-equator gradient of stellar heating, and novel cryospheres. A suite of 3D global climate model simulations is performed for low and high obliquity planets with various stellar fluxes, CO2 concentrations, and initial conditions to explore the propensity for high obliquity climates to undergo global glaciation. We also simulate planets with thick CO2 or H2 atmospheres, such as those expected to develop near or beyond the outer edge of the habitable zone. We show that high obliquity planets are hotter than their low obliquity counterparts due to ice-albedo feedbacks for cold climates, and water vapor in warm climates. We suggest that the water vapor greenhouse trapping is greater on high obliquity bodies for a given global-mean temperature due to the different dynamical regimes that occur between the two states. While equatorial ice belts are stable at high obliquity in some climate regimes, it is substantially harder to achieve global glaciation than for a low obliquity planet. Temperate polar conditions can be present at high obliquity at forcings for which low obliquity planets would be in a hard snowball state. Furthermore, open ocean can persist even in the winter hemisphere and when global-mean temperatures are well below freezing. However, the influence of obliquity diminishes for dense atmospheres, in agreement with calculations from 1D energy balance models.

Planet and satellite atmospheres↗
NASA NTRSDate not supplied

Experimental Observations of Mechanisms of Pattern Formation During Freeze Casting

Empirically, many different materials compositions have been freeze cast over the years. Few have been analyzed to better understand the mechanisms by which the ice crystal growth drives structure formation, particularly the substructures on the cell walls. Collating substructural features, for example, ridges, bridges, and “jellyfish-like” substructures, found on the cell walls of freeze-cast ceramics (platelets versus particles), fibrillated biopolymers (collagen, nanocellulose), and "smooth" biopolymers (chitosan, trehalose), we capture the ice crystal growth process and analyze it both in situ in 2D and "post-mortem" in 3D to gain insights into anisotropic ice crystal growth and other self-assembly mechanisms. Combining these experimental observations with 3D Phase-field simulations of structure formation in ice-templated materials, detailed in a companion presentation, it becomes possible to gain fundamental science insights and to obtain the desired structure-property-processing correlations not only at the more traditional macroscopic, but also at the meso- and microscopic scales.

Kaiyang Yin↗
NASA NTRSDate not supplied

Experimental Observations of Mechanisms of Pattern Formation During Freeze Casting

Empirically, many different materials compositions have been freeze cast over the years. Few have been analyzed to better understand the mechanisms by which the ice crystal growth drives structure formation, particularly the substructures on the cell walls. Collating substructural features, for example, ridges, bridges, and “jellyfish-like” substructures, found on the cell walls of freeze-cast ceramics (platelets versus particles), fibrillated biopolymers (collagen, nanocellulose), and "smooth" biopolymers (chitosan, trehalose), we capture the ice crystal growth process and analyze it both in situ in 2D and "post-mortem" in 3D to gain insights into anisotropic ice crystal growth and other self-assembly mechanisms. Combining these experimental observations with 3D Phase-field simulations of structure formation in ice-templated materials, detailed in a companion presentation, it becomes possible to gain fundamental science insights and to obtain the desired structure-property-processing correlations not only at the more traditional macroscopic, but also at the meso- and microscopic scales.

Kaiyan Yin↗
NASA NTRS2022

The extended atmosphere and circumstellar environment of the cool evolved star VX Sagittarii as seen by MATISSE

Context. VX Sgr is a cool, evolved, and luminous red star whose stellar parameters are difficult to determine, which affects its classification. Aims. We aim to spatially resolve the photospheric extent as well as the circumstellar environment. Methods. We used interferometric observations obtained with the MATISSE instrument in the L (3–4 μm), M (4.5–5 μm), and N (8–13 μm) bands. We reconstructed monochromatic images using the MIRA software. We used 3D radiation-hydrodynamics simulations carried out with CO5BOLD and a uniform disc model to estimate the apparent diameter and interpret the stellar surface structures. Moreover, we employed the radiative transfer codes OPTIM3D and RADMC3D to compute the spectral energy distribution for the L, M, and N bands, respectively. Results. MATISSE observations unveil, for the first time, the morphology of VX Sgr across the L, M, and N bands. The reconstructed images show a complex morphology with brighter areas whose characteristics depend on the wavelength probed. We measured the angular diameter as a function of the wavelength and showed that the photospheric extent in the L and M bands depends on the opacity through the atmosphere. In addition to this, we also concluded that the observed photospheric inhomogeneities can be interpreted as convection-related surface structures. The comparison in the N band yielded a qualitative agreement between the N-band spectrum and simple dust radiative transfer simulations. However, it is not possible to firmly conclude on the interpretation of the current data because of the difficulty in constraing the model parameters using the limited accuracy of our absolute flux calibration. Conclusions. MATISSE observations and the derived reconstructed images unveil the appearance of VX Sgr’s stellar surface and circumstellar environment across a very large spectral domain for the first time.

stars: atmospheres↗
DOE OSTI2012

Progress on the high-current 704 MHz superconducting RF cavity at BNL

The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups and results for the copper prototype. The progress with the niobium cavity fabrication will also be described.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

HOM damping and multipacting analysis of the quarter-wave crab cavity

The quarter-wave crab cavity design has been analyzed further to accommodate LHC requirements. The goal for the design is to provide strong deflecting voltage to the proton bunches at the IP, while keeping the effective length as short as possible. We will evaluate the higher order mode damping with two or four magnetic coupling dampers installed in different configuration. In this paper, we also show possible multipacting locations which are simulated by 2D and 3D codes.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Comparison of the PHISICS/RELAP5-3D Ring and Block Model Results for Phase I of the OECD MHTGR-350 Benchmark

The INL PHISICS code system consists of three modules providing improved core simulation capability: INSTANT (performing 3D nodal transport core calculations), MRTAU (depletion and decay heat generation) and a perturbation/mixer module. Coupling of the PHISICS code suite to the thermal hydraulics system code RELAP5-3D has recently been finalized, and as part of the code verification and validation program the exercises defined for Phase I of the OECD/NEA MHTGR 350 MW Benchmark were completed. This paper provides an overview of the MHTGR Benchmark, and presents selected results of the three steady state exercises 1-3 defined for Phase I. For Exercise 1, a stand-alone steady-state neutronics solution for an End of Equilibrium Cycle Modular High Temperature Reactor (MHTGR) was calculated with INSTANT, using the provided geometry, material descriptions, and detailed cross-section libraries. Exercise 2 required the modeling of a stand-alone thermal fluids solution. The RELAP5-3D results of four sub-cases are discussed, consisting of various combinations of coolant bypass flows and material thermophysical properties. Exercise 3 combined the first two exercises in a coupled neutronics and thermal fluids solution, and the coupled code suite PHISICS/RELAP5-3D was used to calculate the results of two sub-cases. The main focus of the paper is a comparison of the traditional RELAP5-3D “ring” model approach vs. a much more detailed model that include kinetics feedback on individual block level and thermal feedbacks on a triangular sub-mesh. The higher fidelity of the block model is illustrated with comparison results on the temperature, power density and flux distributions, and the typical under-predictions produced by the ring model approach are highlighted.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

FDEM v. 3.0

Program FDEM_v3.0 is designed to simulate three-dimensional (3D) electromagnetic (EM) wave propagation within an isotropic and heterogeneous body. The medium is characterized by the three isotropic (but spatially-variable) parameters electric permittivity, magnetic permeability, and current conductivity. The numerical solution methodology is explicit, time-domain, finite-differencing of the EH (i.e., electric vector – magnetic vector) coupled partial differential system on uniform, but staggered, spatial and temporal grids. In order to suppress grid boundary reflections, FDEM_v3.0 implements “perfectly matched layer” (PML) absorbing boundary conditions on all flanks of the 3D spatial grid in a memory efficient manner.

Aldridge, David F.↗
DOE OSTI2016

FDEM v. 2.0

Program FDEM_v2.0 is designed to simulate three-dimensional (3D) electromagnetic (EM) wave propagation within an isotropic and heterogeneous body. The medium is characterized by the three isotropic (but spatially-variable) parameters electric permittivity, magnetic permeability, and current conductivity. The numerical solution methodology is explicit, time-domain, finite-differencing of the EH (i.e., electric vector – magnetic vector) coupled partial differential system on uniform, but staggered, spatial and temporal grids. FDEM_v2.0 incorporates “perfectly matched layer” (PML) absorbing boundary conditions on all flanks of the 3D spatial grid that effectively suppress grid boundary reflections.

Aldridge, David F.↗
DOE OSTI2017

Sensitivity Analysis of Lbloca In Response To 10 Cfr50.46c New Rulemaking

The Nuclear Regulatory Commission (NRC) is proposing a new rulemaking on emergency core system/loss-of-coolant accident (LOCA) performance analysis. In the proposed rulemaking, designated as 10 CFR 50.46c, the US NRC puts forward an equivalent cladding oxidation criterion as a function of cladding pre-transient hydrogen content. The proposed rulemaking imposes more restrictive and burnupdependent cladding embrittlement criteria; consequently more fuel rods need to be analyzed under LOCA conditions to maintain the safety margin, in contrast to the current practice with which only one hot rod needs to be analyzed. New multi-physics analysis methods are required to provide a thorough characterization of the reactor core in order to identify the locations of the limiting rods and quantify safety margins under LOCA conditions. The U.S. DOE’s Light Water Reactor Sustainability (LWRS) Program has initiated a project to develop multi-physics analytical capabilities, called LOTUS, to support the industry in the transition to the proposed rule. An approach to uncertainty quantification and sensitivity analysis with LOTUS was developed. A typical four-loop PWR plant model was developed and simulated by RELAP5-3D with inputs generated from core design and fuel performance analyses, and uncertainty quantification and sensitivity analysis were performed with seventeen uncertain input parameters. The maximum equivalent cladding reacted ratio (ECRR) and peak clad temperature ratio (PCTR) were selected as the figures of merit (FOM). Pearson, Spearman, partial correlation coefficients, and Sobol indices were considered for all of the figures of merit in the sensitivity analysis.

10CFR50.46c↗
DOE OSTI2013

High-Intensity Continuous Wave Slow Positron Source at Jefferson Lab

We present a novel concept of an electron linac-based slow positron source with projected intensity on the order of 10^10 slow e+/s. The key components of this concept are a Continuous Wave (CW) electron beam, a rotating positron-production target, a synchronized raster/anti-raster, a transport channel, and extraction of positrons into a field-free area through a magnetic field terminator plug for moderation in a solid Neon moderator. The feasibility calculations were completed in the framework of GEANT4 simulation and OPERA-3D magnetic field calculation code.

Wojtsekhowski, Bogdan↗
DOE OSTI2012

Full core reactor analysis: Running Denovo on Jaguar

Fully-consistent, full-core, 3D, deterministic neutron transport simulations using the orthogonal mesh code Denovo were run on the massively parallel computing architecture Jaguar XT5. Using energy and spatial parallelization schemes, Denovo was able to efficiently scale to more than 160 k processors. Cell-homogenized cross sections were used with step-characteristics, linear-discontinuous finite element, and trilinear-discontinuous finite element spatial methods. It was determined that using the finite element methods gave considerably more accurate eigenvalue solutions for large-aspect ratio meshes than using step-characteristics. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗