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NASA NTRSDate not supplied

Nanoflare Heating Frequency of an X-ray Bright Point Observed by MaGIXS

Nanoflares have been considered to be one of the most likely candidates for heating the solar corona to multi-million kelvin temperatures. Individual nanoflares are difficult to detect with today's instruments, but their presence may be established by comparing simulated nanoflare-heated plasma emissions to observed emissions. We present a simulation of emission from an X-ray Bright Point (XBP) detected by the MaGIXS, as well as simultaneous observations from SDO/AIA and Hinode/XRT. To simulate the XBP loops, we utilize the HYDRAD code. The length and magnetic field strength of these loops are determined using potential field extrapolation of SDO/HMI's observed photospheric magnetogram. Each loop is considered to be heated by random nanoflares, the amplitude and frequency of which are governed by the length of the loop and the strength of the magnetic field. The simulated outputs are used to estimate the intensity of spectrally pure maps of Fe-18, Fe-17, Ne-9, O-8, O-9, Ne-9, and so on, which is then compared to the intensity determined from MaGIXS observations. In addition, we derived the intensity maps obtained by AIA and XRT and compared them to the observed data. The composite distribution of the delay time of the nanoflares for which the simulated loops morphology and intensities match with observation shows a peak at 200s-500s, indicating that most of the nanoflares have a high/intermediate frequency.

coronal heating↗

NASA NTRS2001

Near-Horizontal, Two-Phase Flow Patterns of Nitrogen and Hydrogen at Low Mass Heat and Flux (on CD-ROM)

One reason for NASA's interest in cryogenic two-phase flow with low mass and heat flux is the need to design spacecraft heat exchangers used for vaporizing cryogenic propellants. The CD-ROM provides digitized movies of particular flow patterns observed in experimental work. The movies have been provided in (QuickTime9Trademark) format, encoded at 320w x 240h pixels, 15 fps, using the Sorenson(Trademark) Video Codec for compression. Experiments were conducted to obtain data on the two-phase (liquid and vapor) flow behavior of cryogenic nitrogen and hydrogen under low mass and heat flux conditions. Tests were performed in normal gravity with a 1.5 degree up flow configuration. View ports in the apparatus permitted visual observation of the two-phase flow patterns. Computer codes to predict flow patterns were developed from theoretical/empirical models reported in the literature. Predictions from the computer codes were compared with experimental flow pattern observations. Results are presented employing the traditional two-dimensional flow pattern map format using the liquid and gas superficial velocities as coordinates. In general, the agreement between the experimental results and the analytical predictive methods is reasonably good. Small regions of the flow pattern maps are identified where the models are deficient as a result of neglecting phase change phenomena. Certain regions of the maps were beyond the range of the experiments and could not be completely validated. Areas that could benefit from further work include modeling of the transition from separated flow, collection of additional data in the bubble and annular flow regimes, and collection of experimental data at other inclination angles, tube diameters and high heat flux.

TWO PHASE FLOW↗

DOE OSTI2025

Deconvoluting thermomechanical effects in X-ray diffraction data using machine learning

X-ray diffraction is ideal for probing the sub-surface state during complex or rapid thermomechanical loading of crystalline materials. However, challenges arise as the size of diffraction volumes increases due to spatial broadening and because of the inability to deconvolute the effects of different lattice deformation mechanisms. Here, we present a novel approach that uses combinations of physics-based modeling and machine learning to deconvolve thermal and mechanical elastic strains for diffraction data analysis. The method builds on a previous effort to extract thermal strain distribution information from diffraction data. The new approach is applied to extract the evolution of the thermomechanical state during laser melting of an Inconel 625 wall specimen which produces significant residual stress upon cooling. A combination of heat transfer and fluid flow, elasto-plasticity and X-ray diffraction simulations is used to generate training data for machine-learning (Gaussian process regression, GPR) models that map diffracted intensity distributions to underlying thermomechanical strain fields. First-principles density functional theory is used to determine accurate temperature-dependent thermal expansion and elastic stiffness used for elasto-plasticity modeling. The trained GPR models are found to be capable of deconvoluting the effects of thermal and mechanical strains, in addition to providing information about underlying strain distributions, even from complex diffraction patterns with irregularly shaped peaks.

36 MATERIALS SCIENCE↗

NASA NTRS1969

Propellant tank pressurization analysis program

Propellant tank pressurization analysis program considers fluid densities related to pressures and temperatures acting on the components, heat transfer between the fluids, the components, the ambient, plus component volumes, materials, and configurations in the formation of a mathematical model. This program is written in FORTRAN H and MAP.

Epstein, M.↗

NASA NTRS1981

Infrared studies of the S235 molecular cloud

Infrared observations from 7.8 to 200 microns have been obtained for the S235 molecular cloud. Far-infrared maps were obtained for a region of active star formation, as marked by the presence of compact H II regions, water masers, and compact near-infrared sources. The primary heating source for the far-infrared emission appears to be the compact H II region, S235A. Detailed examination of the gas energetics in the region supports the plausibility of the picture in which the gas is heated by collisions with warm dust grains. The ratio of far-infrared optical depth to (C-13)O column density is somewhat lower in this source than is commonly found. This effect may be caused by the presence of substantial (C-13)O in regions where the dust is not warm enough to emit substantial 50-100 micron radiation.

Evans, N. J., II↗

NASA NTRS1986

Particle precipitaion into the thermosphere (invited review)

A review of research on particle precipitation into the thermosphere is presented. Particle precipitation plays an important role in thermospheric dynamics, often being both the most important ionization source and the most important heat source, comparable to Joule heating rates in the auroral zones and typically exceeding solar ultraviolet as an ionization mechanism in the nightside auroral zones and winter polar caps. Rees (1963) has shown that, roughly speaking, one electron-ion pair is produced by each 35 eV of incident electron energy flux; thus, over half of the incident electron energy flux goes into heating rather than into ionization. Precipitating ions also can produce ionization, also requiring roughly 35 eV per pair; however, since ion energy fluxes are typically much weaker than electron fluxes, they have often been neglected. The particle precipitation into the thermosphere is both an important ionization source and an important heat source; since the globally integrated value can vary over more than a factor of ten, and the instantaneous local rate can vary over nearly three orders of magnitude global, maps of precipitation rates are extremely important for predicting thermospheric weather.

Reiff, P. H.↗

NASA NTRS1989

Measurements of turbulence and its evolution and variability during MAP

The understanding of turbulence in the middle atmosphere has improved considerably during the MAP period. For a theoretical viewpoint, several advances were made including understanding the ways in which turbulence is generated, and the differences between the rates of diffusion of momentum and heat. Experimentally, a proper understanding of how radars can be used to measure turbulence has emerged, and turbulent energy dissipation rates in the middle atmosphere were measured with MF, HF, and VHF radars. New rocket techniques were developed which have enabled detailed studies of the fine structure of turbulence to be made. While some discrepancies between techniques still exist, these will undoubtedly be resolved soon, and these different techniques are already providing a great improvement in the understanding of turbulence on a global scale.

Hocking, W. K.↗

NASA NTRS1999

Aerodynamic Flow Field Measurements for Automotive Systems

The design of a modern automotive air handling system is a complex task. The system is required to bring the interior of the vehicle to a comfortable level in as short a time as possible. A goal of the automotive industry is to predict the interior climate of an automobile using advanced computational fluid dynamic (CFD) methods. The development of these advanced prediction tools will enable better selection of engine and accessory components. The goal of this investigation was to predict methods used by the automotive industry. To accomplish this task three separate experiments were performed. The first was a laboratory setup where laser velocimeter (LV) flow field measurements were made in the heating and air conditioning unit of a Ford Windstar. The second involved flow field measurements in the engine compartment of a Ford Explorer, with the engine running idle. The third mapped the flow field exiting the center dashboard panel vent inside the Explorer, while the circulating fan operated at 14 volts. All three experiments utilized full-coincidence three-component LV systems. This enabled the mean and fluctuating velocities to be measured along with the Reynolds stress terms.

Hepner, Timothy E.↗

NASA NTRS2009

Evidence for Interhemispheric Coupling during the Unusual Northern Polar Summer Mesosphere of 2002

Data from the MaCWAVE MIDAS Rocket Program launched during July, 2002, from Andoya Rocket Range (ARR) in Norway have demonstrated that the temperature structure of the summer polar mesosphere during this period was atypical, at least above ARR. The summer polar mesopause region was warmer than normal and of shorter duration than for other years analyzed. Theoretical studies have since been published that imply that the abnormal characteristics of this polar summer were generated by unusual dynamical processes occurring in the southern polar winter hemisphere. We have used data from the SABER instrument aboard the NASA TIMED Satellite to study these characteristics on a global scale and compare them with the features observed in the ensuing seven years. For background, The TIMED Satellite was launched on December 7, 2001 to study the dynamics and energy of the mesosphere and lower thermosphere (MLT). The SABER instrument on TIMED is a limb scanning infrared radiometer designed to measure a large number of minor constituents as well as temperature of the MLT. In this study, we have investigated the temperature characteristics of the polar mesosphere as a function of spatial and temporal considerations. We have used the most recent SABER dataset (1.07) that includes the improved temperature retrievals in Earth polar regions, Weekly averages were used 10 make the comparisons between the winter and summer hemispheres. The unusually short polar summer in the northern hemisphere during 2002 is clearly defined by this analysis and is shown to be unique for the 7 years analyzed. Furthermore, the data analysis agrees with recent theoretical studies showing that this behavior is a result of anomalous heating events in the southern polar stratosphere. The time sequence of the coupling process, as predicted by recent theoretical models, is well defined in a sequence of weekly temperature contour maps measured by SABER.

Goldberg, Richard A.↗

NASA NTRS2011

Evolution of the Equatorial Oscillation in Saturn's Stratosphere Between 2005 and 2010 from Cassini/CIRS Limb Data Analysis

We present an analysis of thermal infrared spectra acquired in limb viewing geometry by Cassini/CIRS in February 2010. We retrieve vertical profiles of Saturn's stratospheric temperature from 20 hPa to 10 (exp -2) hPa, at 9 latitudes between 20 deg N and 20 deg S. Using the gradient thermal wind equation, we derive a map of the zonal wind field. Both the temperature and the zonal wind vertical profiles exhibit an oscillation in the equatorial region. These results are compared to the temperature and zonal wind maps obtained from 2005-2006 CIRS limb data, when this oscillation was first reported. In both epochs, strong temperature anomalies at the equator (up to 20K) are consistent with adiabatic heating (cooling) due to a sinking (rising) motion at a speed of 0.1 - 0.2 mm/s. Finally, we show that the altitude of the maximum eastward wind has moved downwards by 1.3 scale heights in 4.2 years, hence with a 'phase' speed of approximately 0.5 mm/s. This rate is consistent with the estimated period of 14.7 years for the equatorial oscillation, and requires a local zonal acceleration of 1.1 x 10(exp -6) m.s(exp -2) at the 2.5 hPa pressure level. This downward propagation of the oscillation is consistent with it being driven by absorption of upwardly propagating waves.

Guerlet, S.↗

NASA NTRS2012

NASA Tech Briefs, August 2012

Topics covered include: Mars Science Laboratory Drill; Ultra-Compact Motor Controller; A Reversible Thermally Driven Pump for Use in a Sub-Kelvin Magnetic Refrigerator; Shape Memory Composite Hybrid Hinge; Binding Causes of Printed Wiring Assemblies with Card-Loks; Coring Sample Acquisition Tool; Joining and Assembly of Bulk Metallic Glass Composites Through Capacitive Discharge; 670-GHz Schottky Diode-Based Subharmonic Mixer with CPW Circuits and 70-GHz IF; Self-Nulling Lock-in Detection Electronics for Capacitance Probe Electrometer; Discontinuous Mode Power Supply; Optimal Dynamic Sub-Threshold Technique for Extreme Low Power Consumption for VLSI; Hardware for Accelerating N-Modular Redundant Systems for High-Reliability Computing; Blocking Filters with Enhanced Throughput for X-Ray Microcalorimetry; High-Thermal-Conductivity Fabrics; Imidazolium-Based Polymeric Materials as Alkaline Anion-Exchange Fuel Cell Membranes; Electrospun Nanofiber Coating of Fiber Materials: A Composite Toughening Approach; Experimental Modeling of Sterilization Effects for Atmospheric Entry Heating on Microorganisms; Saliva Preservative for Diagnostic Purposes; Hands-Free Transcranial Color Doppler Probe; Aerosol and Surface Parameter Retrievals for a Multi-Angle, Multiband Spectrometer LogScope; TraceContract; AIRS Maps from Space Processing Software; POSTMAN: Point of Sail Tacking for Maritime Autonomous Navigation; Space Operations Learning Center; OVERSMART Reporting Tool for Flow Computations Over Large Grid Systems; Large Eddy Simulation (LES) of Particle-Laden Temporal Mixing Layers; Projection of Stabilized Aerial Imagery Onto Digital Elevation Maps for Geo-Rectified and Jitter-Free Viewing; Iterative Transform Phase Diversity: An Image-Based Object and Wavefront Recovery; 3D Drop Size Distribution Extrapolation Algorithm Using a Single Disdrometer; Social Networking Adapted for Distributed Scientific Collaboration; General Methodology for Designing Spacecraft Trajectories; Hemispherical Field-of-View Above-Water Surface Imager for Submarines; and Quantum-Well Infrared Photodetector (QWIP) Focal Plane Assembly.

Source record↗

NASA NTRS2012

NASA Glenn Icing Research Tunnel: Upgrade and Cloud Calibration

In 2011, NASA Glenn s Icing Research Tunnel underwent a major modification to it s refrigeration plant and heat exchanger. This paper presents the results of the subsequent full cloud calibration. Details of the calibration procedure and results are presented herein. The steps include developing a nozzle transfer map, establishing a uniform cloud, conducting a drop sizing calibration and finally a liquid water content calibration. The goal of the calibration is to develop a uniform cloud, and to build a transfer map from the inputs of air speed, spray bar atomizing air pressure and water pressure to the output of median volumetric droplet diameter and liquid water content.

VanZante, Judith Foss↗

NASA NTRS2012

NASA Glenn Icing Research Tunnel: 2012 Cloud Calibration Procedure and Results

VanZante, Judith Foss↗

NASA NTRS1997

Network Coronal Bright Points: Coronal Heating Concentrations Found in the Solar Magnetic Network

We examine the magnetic origins of coronal heating in quiet regions by combining SOHO/EIT Fe XII coronal images and Kitt Peak magnetograms. Spatial filtering of the coronal images shows a network of enhanced structures on the scale of the magnetic network in quiet regions. Superposition of the filtered coronal images on maps of the magnetic network extracted from the magnetograms shows that the coronal network does indeed trace and stem from the magnetic network. Network coronal bright points, the brightest features in the network lanes, are found to have a highly significant (8 sigma above random chance) coincidence with polarity dividing lines (neutral lines) in the network, and are often at the feet of enhanced coronal structures that stem from the network and reach out over the cell interiors. These results indicate that, similar to the close linkage of neutral-line core fields with coronal heating in active regions, low-lying core fields encasing neutral lines in the magnetic network often drive noticeable coronal heating both within themselves (the network coronal bright points) and on more extended fields lines rooted around them. This behavior favors the possibility that active core fields in the network are the main drivers of the heating of the bulk of the quiet corona, on scales much larger than the network lanes and cells.

Falconer, D. A.↗

DOE OSTI2022

Additive manufacturing of ceramic materials for energy applications: Road map and opportunities

Among engineering materials, ceramics are indispensable in energy applications such as batteries, capacitors, solar cells, smart glass, fuel cells and electrolyzers, nuclear power plants, thermoelectrics, thermoionics, carbon capture and storage, control of harmful emission from combustion engines, piezoelectrics, turbines and heat exchangers, among others. Advances in additive manufacturing (AM) offer new opportunities to fabricate these devices in geometries unachievable previously and may provide higher efficiencies and performance, all at lower costs. This article reviews the state of the art in ceramic materials for various energy applications. The focus of the review is on material selections, processing, and opportunities for AM technologies in energy related ceramic materials manufacturing. The aim of the article is to provide a roadmap for stakeholders such as industry, academia and funding agencies on research and development in additive manufacturing of ceramic materials toward more efficient, cost-effective, and reliable energy systems.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Inverse Mapping of the Collision Kernel and Wall Flux Scaling in a Tall Convection‐Cloud Chamber Using Local Sensors and Knowledge‐Informed Deep Learning

Droplet collision–coalescence is a crucial process in cloud physics, but accurately representing this process under different dynamical conditions remains challenging. A proposed future convective‐cloud chamber aims to investigate this key process, but the method for observing it remains unclear, even though it is theoretically established that collision‐coalescence will occur. This study serves as a proof‐of‐concept demonstration of how knowledge‐informed deep learning, combined with measurement data from local sensors in the chamber, can be used to estimate the collision kernels, which determine how the droplet size distribution evolves during collision‐coalescence. In addition to estimating the collision kernel, we also address wall fluxes, another uncertain but important process that acts as a source of heat and moisture in the chamber. Ensemble runs of large‐eddy simulations are conducted by scaling the wall fluxes and the collision kernel, while the measured flow and cloud properties are used as inputs for a neural network. Results indicate that this approach successfully maps the scaling of wall fluxes and the collision kernel with biases of approximately 1% or less relative to the range of the target data. This proof‐of‐concept lays the groundwork for future applications; when the real measurements are available, real sensor data combined with the trained model presented in this work will enable estimation of the actual wall fluxes and collision kernel.

cloud chamber↗

DOE OSTI2023

Accelerated thermal property mapping of TRISO advanced nuclear fuel

TRistructural ISOtropic (TRISO) fuel is a leading-edge nuclear fuel form representing a departure from the more traditional nuclear fuel forms utilized in the reactor fleet of today. Rather than a monolithic fuel pellet of uranium dioxide, integral fuel forms containing TRISO fuel are composed of thousands of microencapsulated uranium-bearing fuel kernels and individually coated with multiple layers of pyrolytic carbon and silicon carbide. These multilayered ceramic coatings serve as an environmental barrier to ensure radioactive and chemically reactive fission products are contained within the reactor fuel elements, but also participate in the transfer of heat generated in the nuclear fuel to the coolant – the primary purpose of a nuclear reactor. Since traditional thermal property measurement techniques, such as laser flash analysis, would be unable to resolve the thermal properties of the individual TRISO coating layers, a simplified frequency-domain thermoreflectance technique has been developed to rapidly map the thermal properties of TRISO particles. Using this technique, the thermal properties of TRISO particles have been mapped from room temperature up to 1000 °C to examine the spatial variation and temperature-dependency of the thermal properties within each layer. Additionally, spatial-domain thermoreflectance was used to examine the anisotropy of the thermal properties for each layer at different locations within a single TRISO particle, and across multiple TRISO particles to assess the intra- and inter-particle uniformity of thermal properties, respectively. To elucidate the underlying causes for the measured variations in thermal properties, scanning electron microscopy and Raman spectroscopy were used to examine variations in microstructure and chemical bonding within the different coating layers. Results from this work are then compared with previous examinations of TRISO fuel particles and microstructurally driven mechanisms for the variations in the measured thermal properties of the different carbonaceous layers are discussed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2024

Evaluation of SPARC divertor conditions in H-mode operation using SOLPS-ITER

The predicted divertor conditions for the SPARC tokamak are calculated using SOLPS-ITER for a range of scrape-off-layer (SOL) heat flux widths λ q , input powers, and particle fueling locations. Under H-mode scenario conditions with an upstream separatrix density of 1 x 10 20 m -3 , the most conservative range of λ q extrapolations ( 0.15 mm) results in extremely high unmitigated particle and energy fluxes to the divertor, both under full field (12.2 T) and power (P SOL = 29 MW) conditions, and 2/3 field with P SOL = 10 MW. Increasing the cross-field SOL diffusivities by 2–10× reduces the magnitude of the mitigation challenge, however strategies such as impurity seeding or strike-point-sweeping will likely still be required. A combination of steady-state and time-dependent SOLPS-ITER simulations are used to map out phase space diagrams of upstream and divertor conditions. The simulations include parallel currents but neglect cross-field drifts. At low upstream density the inner and outer divertor conditions are highly asymmetric, with a large temperature difference and significant heat fluxes driven by parallel currents. The solution has sharp bifurcations with a region of hysteresis, depending on whether the initial state is at a low or high density. This behavior is observed even when the fueling location, cross-field diffusivity, and impurity level is changed, although the density window with asymmetry is reduced with increasing diffusivity. The addition of neon impurity seeding reduces the divertor heat fluxes, but also causes a drop in the upstream electron density with fixed particle throughput. This drop can be counteracted by increased main ion throughput, however too much neon results in a back transition into the asymmetric divertor regimes suggesting a need for control of both main ion and impurity seeding levels to achieve a desired divertor state.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗