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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 1,333 records · Page 74
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Fiber Composite Sandwich Thermostructural Behavior - Computational Simulation

Four computational simulation methods with different levels of sophistication were used to simulate thermal behavior and structural changes of composite sandwich panels with a honeycomb core subjected to a variety of environmental effects. The models on thich these methods are based include three-dimensional finite-element modeling, three-dimensional finite-element modeling assuming a homogeneous core, laminate theory, and simple equations for predicting the equivalent properties of the honeycomb core. A procedure was developed and embedded in a composite mechanics computer code, which made it possile to conduct parametric studies to determine 'optimum' composite sandwich configurations for specific applications. The procedure was applied for the evaluation of composite sandwich behavior at the global, local, laminate, ply, and micromechanics levels when the composite sandwich is subjected to hygral, thermal, and mechanical loading environments.

Chamis, Christos C.↗
NASA NTRS1988

On air motion trajectories in cold fronts

This paper examines air parcel trajectories in the two-dimensional model for a cold front by Reeder and Smith (1987). These are found to be in close agreement with trajectories deduced from analyses of summertime 'cool changes' in southeastern Australia, adding further support to the applicability of the numerical model to this kind of cold front. The favorable comparison points also to the dynamical consistency of the conceptual model for the cool change, which has evolved from the analysis of data from observational experiments.

Reeder, Michael J.↗
NASA NTRS1988

Lidar observations of the planetary boundary layer during FASINEX

Data are presented on the planetary boundary layer (PBL) over the ocean acquired with an airborne downward-looking lidar during the Frontal Air-Sea Interaction Experiment (FASINEX) with the purpose of studying the impact of an ocean front on air-sea interactions. No changes in the PBL structure were detected by lidar. Lidar data were then used along with other readily available remotely-sensed data and a one-dimensional boundary-layer-growth model to infer the mean PBL moisture and temperature structure and to estimate the surface fluxes of heat and moisture.

Melfi, S. H.↗
NASA NTRS1989

Fluid flow analysis of the SSME high pressure fuel and oxidizer turbine coolant systems

The objective is to provide improved analysis capability for the Space Shuttle Main Engine (SSME) high pressure fuel and oxidizer turbine coolant systems. Each of the systems was analyzed to determine fluid flow rate and thermodynamic and transport properties at all key points in the systems. Existing computer codes were used as a baseline for these analyses. These codes were modified to provide improved analysis capability. The major areas of improvement are listed. A review of the drawings was performed, and pertinent geometry changes were included in the models. Improvements were made in the calculation of thermodynamic and transport properties for a mixture of hydrogen and steam. A one-dimensional turbine model for each system is included as a subroutine to each code. This provides a closed loop analysis with a minimum of required boundary conditions as input. An improved labyrinth seal model is included in the high pressure fuel turbine coolant model. The modifications and the analysis results are presented in detail.

Teal, G. A.↗
NASA NTRS1992

Space environmental effects on LDEF low Earth orbit exposed graphite reinforced polymer matrix composites

The Long Duration Exposure Facility (LDEF) was deployed on April 7, 1984 in low earth orbit (LEO) at an altitude of 482 kilometers. On board experiments experienced the harsh LEO environment including atomic oxygen (AO), ultraviolet radiation (UV), and thermal cycling. During the 5.8 year mission, the LDEF orbit decayed to 340 kilometers where significantly higher AO concentrations exist. LDEF was retrieved on January 12, 1990 from this orbit. One experiment on board LDEF was M0003, Space Effects on Spacecraft Materials. As a subset of M0003 nearly 500 samples of polymer, metal, and glass matrix composites were flown as the Advanced Composites Experiment M0003-10. The Advanced Composites Experiment is a joint effort between government and industry with the Aerospace Corporation serving as the experiment integrator. A portion of the graphite reinforced polymer matrix composites were furnished by the Boeing Defense and Space Group, Seattle, Washington. Test results and discussions for the Boeing portion of M0003-10 are presented. Experiment and specimen location on the LDEF are presented along with a quantitative summary of the pertinent exposure conditions. Matrix materials selected for the test were epoxy, polysulfone, and polyimide. These composite materials were selected due to their suitability for high performance structural capability in spacecraft applications. Graphite reinforced polymer matrix composites offer higher strength to weight ratios along with excellent dimensional stability. The Boeing space exposed and corresponding ground control composite specimens were subjected to post flight mechanical, chemical, and physical testing in order to determine any changes in critical properties and performance characteristics. Among the more significant findings are the erosive effect of atomic oxygen on leading edge exposed specimens and microcracking in non-unidirectionally reinforced flight specimens.

George, Pete↗
NASA NTRS1951

On the particular integrals of the Prandtl-Busemann iteration equations for the flow of a compressible fluid

The particular integrals of the second-order and third-order Prandtl-Busemann iteration equations for the flow of a compressible fluid are obtained by means of the method in which the complex conjugate variables are utilized as the independent variables of the analysis. The assumption is made that the Prandtl-Glauert solution of the linearized or first-order iteration equation for the two-dimensional flow of a compressible fluid is known. The forms of the particular integrals, derived for subsonic flow, are readily adapted to supersonic flows with only a change in sign of one of the parameters of the problem.

Kaplan, Carl↗
NASA NTRS1996

Advanced interactive display formats for terminal area traffic control

This report describes the basic design considerations for perspective air traffic control displays. A software framework has been developed for manual viewing parameter setting (MVPS) in preparation for continued, ongoing developments on automated viewing parameter setting (AVPS) schemes. Two distinct modes of MVPS operations are considered, both of which utilize manipulation pointers imbedded in the three-dimensional scene: (1) direct manipulation of the viewing parameters -- in this mode the manipulation pointers act like the control-input device, through which the viewing parameter changes are made. Part of the parameters are rate controlled, and part of them position controlled. This mode is intended for making fast, iterative small changes in the parameters. (2) Indirect manipulation of the viewing parameters -- this mode is intended primarily for introducing large, predetermined changes in the parameters. Requests for changes in viewing parameter setting are entered manually by the operator by moving viewing parameter manipulation pointers on the screen. The motion of these pointers, which are an integral part of the 3-D scene, is limited to the boundaries of the screen. This arrangement has been chosen in order to preserve the correspondence between the spatial lay-outs of the new and the old viewing parameter setting, a feature which contributes to preventing spatial disorientation of the operator. For all viewing operations, e.g. rotation, translation and ranging, the actual change is executed automatically by the system, through gradual transitions with an exponentially damped, sinusoidal velocity profile, in this work referred to as 'slewing' motions. The slewing functions, which eliminate discontinuities in the viewing parameter changes, are designed primarily for enhancing the operator's impression that he, or she, is dealing with an actually existing physical system, rather than an abstract computer-generated scene. The proposed, continued research efforts will deal with the development of automated viewing parameter setting schemes. These schemes employ an optimization strategy, aimed at identifying the best possible vantage point, from which the air traffic control scene can be viewed for a given traffic situation. They determine whether a change in viewing parameter setting is required and determine the dynamic path along which the change to the new viewing parameter setting should take place.

Grunwald, Arthur J.↗
NASA NTRS1999

Advanced Interactive Display formats for Terminal Area Traffic Control

This report describes the basic design considerations for perspective Air Traffic Control displays. A software framework has been developed for manual viewing parameter setting (MVPS) in preparation for continued, ongoing developments on automated viewing parameter setting (AVPS) schemes. Two distinct modes of MVPS operations are considered, both of which utilize manipulation pointers imbedded in the three-dimensional scene: (1) direct manipulation of the viewing parameters; in this mode the manipulation pointers act like the control-input device, through which the viewing parameter changes are made. Part of the parameters are rate controlled, and part of them position controlled. This mode is intended for making fast, iterative small changes in the parameters. (2) indirect manipulation of the viewing parameters. This mode is intended primarily for introducing large, predetermined changes in the parameters. Requests for changes in viewing parameter setting are entered manually by the operator by moving viewing parameter manipulation pointers on the screen. The motion of these pointers, which are an integral part of the 3-D scene, is limited to the boundaries of screen. This arrangement has been chosen, in order to preserve the correspondence between the spatial lay-outs of the new and the old viewing parameter setting, a feature which contributes to preventing spatial disorientation of the operator. For all viewing operations, e.g. rotation, translation and ranging, the actual change is executed automatically by the system, through gradual transitions with an exponentially damped, sinusoidal velocity profile, in this work referred to as 'slewing' motions. The slewing functions, which eliminate discontinuities in the viewing parameter changes, are designed primarily for enhancing the operator's impression that he, or she, is dealing with an actually existing physical system, rather than an abstract computer-generated scene, The proposed, continued research efforts will deal with the development of automated viewing parameter setting schemes. These schemes employ an optimization strategy, aimed at identifying the best possible vantage point, from which the Air Traffic Control scene can be viewed for a given traffic situation. They determine whether a change in viewing parameter setting is required and determine the dynamic path along which the change to the new viewing parameter setting should take place.

Grunwald, Arthur J.↗
NASA NTRS2001

Consideration of Moving Tooth Load in Gear Crack Propagation Predictions

Robust gear designs consider not only crack initiation, but crack propagation trajectories for a fail-safe design. In actual gear operation, the magnitude as well as the position of the force changes as the gear rotates through the mesh. A study to determine the effect of moving gear tooth load on crack propagation predictions was performed. Two-dimensional analysis of an involute spur gear and three-dimensional analysis of a spiral-bevel pinion gear using the finite element method and boundary element method were studied and compared to experiments. A modified theory for predicting gear crack propagation paths based on the criteria of Erdogan and Sih was investigated. Crack simulation based on calculated stress intensity factors and mixed mode crack angle prediction techniques using a simple static analysis in which the tooth load was located at the highest point of single tooth contact was validated. For three-dimensional analysis, however, the analysis was valid only as long as the crack did not approach the contact region on the tooth.

Lewicki, David G.↗
NASA NTRS2002

Effects of Volcanic Eruptions on Stratospheric Ozone Recovery

The effects of the stratospheric sulfate aerosol layer associated with the Mt. Pinatubo volcano and future volcanic eruptions on the recovery of the ozone layer is studied with an interactive two-dimensional photochemical model. The time varying chlorine loading and the stratospheric cooling due to increasing carbon dioxide have been taken into account. The computed ozone and temperature changes associated with the Mt. Pinatubo eruption in 1991 agree well with observations. Long model runs out to the year 2050 have been carried out, in which volcanoes having the characteristics of the Mount Pinatubo volcano were erupted in the model at 10-year intervals starting in the year 2010. Compared to a non-volcanic run using background aerosol loading, transient reductions of globally averaged column ozone of 2-3 percent were computed as a result of each of these eruptions, with the ozone recovering to that computed for the non-volcanic case in about 5 years after the eruption. Computed springtime Arctic column ozone losses of from 10 to 18 percent also recovered to the non-volcanic case within 5 years. These results suggest that the long-term recovery of ozone would not be strongly affected by infrequent volcanic eruptions with a sulfur loading approximating Mt. Pinatubo. Sensitivity studies in which the Arctic lower stratosphere was forced to be 4 K and 10 K colder resulted in transient ozone losses of which also recovered to the non-volcanic case in 5 years. A case in which a volcano five times Mt. Pinatubo was erupted in the year 2010 led to maximum springtime column ozone losses of 45 percent which took 10 years to recover to the background case. Finally, in order to simulate a situation in which frequent smaller volcanic eruptions result in increasing the background sulfate loading, a simulation was made in which the background aerosol was increased by 10 percent per year. This resulted in a delay of the recovery of column ozone to 1980 values of more than 10 years.

Rosenfield, Joan E.↗
NASA NTRS2013

Discontinuity Detection for Analysis of Telerobot Trajectories

To identify spatial and temporal discontinuities in telerobot movement in order to describe the shift in operators control and error correction strategies from continuous control to move-and-wait strategies. This shift was studied under conditions of simulated increasingly time-delayed teleoperation. The ultimate goal is to determine if the time delay associated with the shift is invariant with independently imposed control difficulty. We expect this shift to manifest itself as changes in the number of discontinuity of movement path. We proposed an approach to spatial and temporal discontinuity detection algorithm for analysis of teleoperated trajectory in three dimensional space. The algorithm provides a simple and potentially objective method for detecting the discontinuity during telerobot operation and evaluating the difficulty of rotational coordinate condition in teleoperation.

Yeom, Kiwon↗
NASA NTRS2018

One-Dimensional Modeling Methodology for Shock Tubes: Application to the EAST Facility

In this work, a one-dimensional methodology for simulating shock tubes is developed. The model accounts for the viscous interactions of the shock with the shock tube wall by adding an area change source term in the 1-D conservation equations corresponding to the boundary layer growth. This source term corresponds to the mass and energy going into the boundary layer. The boundary layer growth is computed using a simple model with a scaling factor. This scale factor is used to tailor a solution to match the deceleration profile of a shock tube test. In doing so, not only will the source term take into account boundary layer losses, it will also cover any effect due to radiative cooling loses from the gas. For this study, the Electric Arc Shock Tube(EAST) facility at NASA Ames Research Center is modeled for Earth reentry conditions. The purpose of this paper is to investigate if anomalies identified for certain conditions in the EAST data are due to shock deceleration. These anomalies include measuring electron number density above equilibrium predictions and observing that radiance profiles can continually increase behind the shock, never reach steady state, for certain shots (typically those less than 10 km/s). An eleven species air mixture is chosen to study the chemistry of the flow. Comparisons of the simulations to the experimental results are presented. Good agreement with the shock deceleration profiles was achieved by tuning in the boundary layer scale factor. The temperature as well as electron number density increases behind the shock, as has also been observed in the experiments. Finally, radiance comparisons between results from NEQAIR and experiments also show good agreement for some shots, but significant discrepancies are still observed for others.

Sharma, Maitreyee↗
NASA NTRS2018

One-Dimensional Modeling Methodology for Shock Tubes: Application to the EAST Facility

In this work, a one-dimensional methodology for simulating shock tubes is developed. The model accounts for the viscous interactions of the shock with the shock tube wall by adding an area change source term in the 1-D conservation equations corresponding to the boundary layer growth. This source term corresponds to the mass and energy going into the boundary layer. The boundary layer growth is computed using a simple model with a scaling factor. This scale factor is used to tailor a solution to match the deceleration profile of a shock tube test. In doing so, not only will the source term take into account boundary layer losses, it will also cover any effect due to radiative cooling loses from the gas. For this study, the Electric Arc Shock Tube(EAST) facility at NASA Ames Research Center is modeled for Earth reentry conditions. The purpose of this paper is to investigate if anomalies identified for certain conditions in the EAST data are due to shock deceleration. These anomalies include measuring electron number density above equilibrium predictions and observing that radiance profiles can continually increase behind the shock, never reach steady state, for certain shots (typically those less than 10 km/s). An eleven species air mixture is chosen to study the chemistry of the flow. Comparisons of the simulations to the experimental results are presented. Good agreement with the shock deceleration profiles was achieved by tuning in the boundary layer scale factor. The temperature as well as electron number density increases behind the shock, as has also been observed in the experiments. Finally, radiance comparisons between results from NEQAIR and experiments also show good agreement for some shots, but significant discrepancies are still observed for others.

Sharma, Maitreyee↗
DOE OSTI2023

Multi-dimensional resilience: A quantitative exploration of disease outcomes and economic, political, and social resilience to the COVID-19 pandemic in six countries

The COVID-19 pandemic has highlighted a need for better understanding of countries’ vulnerability and resilience to not only pandemics but also disasters, climate change, and other systemic shocks. A comprehensive characterization of vulnerability can inform efforts to improve infrastructure and guide disaster response in the future. In this paper, we propose a data-driven framework for studying countries’ vulnerability and resilience to incident disasters across multiple dimensions of society. To illustrate this methodology, we leverage the rich data landscape surrounding the COVID-19 pandemic to characterize observed resilience for several countries (USA, Brazil, India, Sweden, New Zealand, and Israel) as measured by pandemic impacts across a variety of social, economic, and political domains. We also assess how observed responses and outcomes (i.e., resilience) of the COVID-19 pandemic are associated with pre-pandemic characteristics or vulnerabilities, including (1) prior risk for adverse pandemic outcomes due to population density and age and (2) the systems in place prior to the pandemic that may impact the ability to respond to the crisis, including health infrastructure and economic capacity. Our work demonstrates the importance of viewing vulnerability and resilience in a multi-dimensional way, where a country’s resources and outcomes related to vulnerability and resilience can differ dramatically across economic, political, and social domains. This work also highlights key gaps in our current understanding about vulnerability and resilience and a need for data-driven, context-specific assessments of disaster vulnerability in the future.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1986

Turbulent dispersion of the icing cloud from spray nozzles used in icing tunnels

To correctly simulate flight in natural icing conditions, the turbulence in an icing simulator must be as low as possible. But some turbulence is required to mix the droplets from the spray nozzles and achieve an icing cloud of uniform liquid water content. The goal for any spray system is to obtain the widest possible spray cloud with the lowest possible turbulence in the test section of a icing tunnel. This investigation reports the measurement of turbulence and the three-dimensional spread of the cloud from a single spray nozzle. The task was to determine how the air turbulence and cloud width are affected by spray bars of quite different drag coefficients, by changes in the turbulence upstream of the spray, the droplet size, and the atomizing air. An ice accretion grid, located 6.3 m downstream of the single spray nozzle, was used to measure cloud spread. Both the spray bar and the grid were located in the constant velocity test section. Three spray bar shapes were tested: the short blunt spray bar used in the NASA Lewis Icing Research Tunnel, a thin 14.6 cm chord airfoil, and a 53 cm chord NACA 0012 airfoil. At the low airspeed (56 km/hr) the ice accretion pattern was axisymmetric and was not affected by the shape of the spray bar. At the high airspeed (169 km/hr) the spread was 30 percent smaller than at the low airspeed. For the widest cloud the spray bars should be located as far upstream in the low velocity plenum of the icing tunnel. Good comparison is obtained between the cloud spread data and predicitons from a two-dimensional cloud mixing computer code using the two equation turbulence (k epsilon g) model.

Marek, C. J.↗
DOE OSTI2018

In situ high-energy X-ray diffraction mapping of Lüders band propagation in medium-Mn transformation-induced plasticity steels

Two-dimensional distributions of microstructural characteristics of austenite (γ) around the Lüders band in medium-Mn transformation-induced plasticity (TRIP) steel were revealed by in situ high-energy X-ray diffraction. Lüders band propagation leads to significant changes in the volume fraction and lattice strains of austenite. The evolution of the lattice strain of γ-311 accords well with the true yield behavior model and is used to estimate the angle of the Lüders band front with respect to the tensile axis. The modified Williamson-Hall analysis shows that the dislocation density in austenite increased from 7 × 10 14 m -2 to 1.5 × 10 15 m -2 after Lüders band propagation. This in situ high-energy X-ray diffraction study unravels two-dimensional distribution of microstructural evolution during Lüders band propagation in medium-Mn TRIP steels.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Two-Dimensional Siloxene Nanosheets: Understanding the Effect of Heat Treatment on the Surface Chemistry and Resulting Electrochemistry in Lithium-Based Batteries

Two-dimensional (2D) silicon materials are conceptually appealing as negative electrode materials in lithium-ion batteries due to their layered morphology, which can accommodate (de)lithiation-induced volume changes. Herein, heat treatment of 2D Siloxene materials was used to modify the surface functional groups to determine the impact on the electrochemical behavior. Spectroscopic characterization of the heat-treated nanosheets confirmed the loss of oxygenated and hydride surface functional groups with an increased annealing temperature. Formation and disproportionation of the amorphous suboxides with increasing heat treatment were affirmed with lab and synchrotron-based measurements. A reduced irreversible capacity was observed for Siloxene with a higher temperature heat treatment consistent with the formation of a more favorable surface electrolyte interphase (SEI). A Siloxene-400||NMC622 full cell (prepared with 400 °C-annealed Siloxene (Siloxene-400) and LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622)) showed significantly enhanced capacity and rate capability compared to a nano Si||NMC622 cell. Finally, these results illustrate the ability of thermal annealing to modify the surface functional groups of Siloxene and highlight the favorable impact of the appropriate surface functionality on the electrochemistry of Siloxene in lithium cells.

25 ENERGY STORAGE↗
DOE OSTI2018

Modeling of three-dimensional surfaces using high-level canonical piecewise-linear functions in cylindrical coordinates

In this paper, the potential application of the high-level canonical piecewise-linear model in the field of three-dimensional visualization is proposed. This idea emerges from the premise that a three-dimensional surface can be modeled by a continuous two-dimensional function. In this regard, the main contribution consists in providing a methodology for the construction of such function. For this purpose, the well-known algorithm used in the high-level canonical piecewise-linear model has been modified to achieve functions with greater graphing capability. One of the most notorious changes made with respect to the traditional methodology is the use of a new scheme of function domain partition. Contrary to the simplicial partitioning, in our proposal, an equally distributed angular partitioning is considered. With this, the resulting approximate function is expressed in cylindrical coordinates which overcome the typical limitation of graphs in Cartesian coordinates of only representing single-valued surfaces. Another remarkable change can be found in the range of evaluation of the function. Instead of using an open interval, in our approach, a closed interval from 0 to 2π is adopted. To support this proposal, illustrative case studies are reported. Numerical simulations demonstrate the effectiveness of this type of representation model not only in visual perception of three-dimensional surfaces, but also in more complex tasks like volume estimation.

97 MATHEMATICS AND COMPUTING↗