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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 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

An updated theory of the polar wind

The 'classical' polar wind is an ambipolar outflow of thermal plasma from the terrestrial ionosphere at high latitudes. As the plasma escapes along diverging geomagnetic flux tubes, it undergoes four major transitions, including a transition from chemical to diffusion dominance, a transition from subsonic to supersonic flow, a transition from collision-dominated to collisionless regimes, and a transition from a heavy to a light ion. A further complication arises because of horizontal convection of the flux tubes owing to magnetospheric electric fields. Recent modelling predictions indicate that the polar wind has the following characteristics: (1) the ion and electron distributions are anisotropic and asymmetric in the collisionless regime; (2) elevated electron temperatures act to produce significant escape fluxes of suprathermal O(+) ions; (3) the interaction of the hot magnetospheric and cold ionospheric electron population leads to a localized (double layer) electric field which accelerates the polar wind ions; (4) a time-dependent expansion produces suprathermal ions; and (5) large perturbations lead to the formation of forward and reverse shocks. These and other results are reviewed.

Schunk, R. W.↗
DOE OSTI2021

Tools for Assessing Performance Project: FY2021 Quarter 4 Report

The rotatable building located at Texas Tech’s Reese Technology Center is approximately 14 m wide (width being defined as more normal to the wind than parallel), 9 m long (aligned more with the wind than perpendicular), and 4 m tall. By placing 29 sonic anemometers downwind of the building, see Fig. 1, this facility provided a chance to collect data concerning both the wake velocity deficit distribution in the downstream and crosssteam directions (relative to the mean wind) behind an isolated building. A preliminary comparison between this data and the recently- developed fast-running diffusive wake model, which was developed based on wind tunnel and LES (performed with JOULES) simulations, for the purpose of either validating this model of understanding potential persistent differences between the idealized wind tunnel or LES conditions and those of full-scale real world phenomena. For this preliminary exploration, we utilized the diffusive wake model implemented in the QUIC model.

42 ENGINEERING↗
NASA NTRS2003

The Structural Changes of Tropical Cyclones Upon Interaction with Vertical Wind Shear

The Fourth Convection and Moisture Experiment (CAMEX-4) provided a unique opportunity to observe the distributions and document the roles of important atmospheric factors that impact the development of the core asymmetries and core structural changes of tropical cyclones embedded in vertical wind shear. The state-of-the-art instruments flown on the NASA DC-8 and ER-2, in addition to those on the NOAA aircraft, provided a unique set of observations that documented the core structure throughout the depth of the tropical cyclone. These data have been used to conduct a combined observational and modeling study using a state-of-the-art, high- resolution mesoscale model to examine the role of the environmental vertical wind shear in producing tropical cyclone core asymmetries, and the effects on the structure and intensity of tropical cyclones.The scientific objectives of this study were to obtain in situ measurements that would allow documentation of the physical mechanisms that influence the development of the asymmetric convection and its effect on the core structure of the tropical cyclone.

Ritchie, Elizabeth A.↗
NASA NTRS1984

Application of Fabry-perot Spectrometers for Measurement of Upper Atmosphere Temperatures and Winds

The mechanisms giving rise to certain airglow and auroral emissions and their height distribution are briefly surveyed. The basic principles of operation of scanning Fabry-Perot spectrometers are outlined in order to illustrate the calibration and use of such instruments to measure Doppler broadening and shift of atomic emission lines in the spectrum of the airglow and aurora and hence to infer atmospheric temperatures and wind velocities. Technical details of some specific instruments are given. Brief mention is made of the use of wide angle Michelson interferometers for the same application. Emphasis is given to the future importance of imaging Fabry-Perot spectrometers to permit the detailed mapping of temperature and wind velocity, especially in the auroral regions.

F Jacka↗
NASA NTRS2001

Ventifact Formation in the Mojave Desert: Field Analogs for Martian Processes

Two field studies in the Mojave Desert, California, shed light on processes of ventifact formation. The field sites are located on a ridge at Little Cowhole Mountain, which lies approximately 12 km south of Baker, and on an unnamed ridge situated along the northern boundary of the Mojave River Sink (Rasor Road site). The rocks at Little Cowhole Mountain are a blue-grey marble/dolomite, whereas those at Rasor Road are Miocene volcanic rocks (basalt). At both sites the abrasive agent is a fine-grained aeolian sand which was probably derived largely from the Mojave River. There are minimal modem inputs of sand to either site: abrasion occurs as a result of unique climatic and topographic conditions which allow pre-existing sand to be recycled from one aspect of the ridge to the other. Climatic conditions are well suited for ventifact formation. Owing, to the dry climate (marked by low average relative humidity, infrequent dew, and low annual rainfall), rates of chemical weathering are low. Where resurfacing of the rocks by sand abrasion proceeds at a rate greater than weathering, the ventifacts are considered "active." Active ventifacts are found atop and straddling the ridge crests, in the zone of maximum wind velocity and sediment supply. Inactive ventifacts occur where modem weathering Processes exceed abrasion rates; principally on the basal two-thirds of the hillslope, where wind velocity and sediment supply are lower. At intermediate locations between the slope base and crest, ventifacts are either active or inactive, depending on local conditions. The presence of relict ventifacts at the study sites, as well as elsewhere in the eastern Mojave Desert, suggests that the conditions for venti fact formation must have been more intense and extensive in the past. Together, the studies illustrate that the processes that interact to form ventifacts are highly complex, and must be studied at many scales. Small-scale effects, such as local topography, plant cover, or even the spatial distribution of boulders, strongly influence the formation of each individual ventifact. Mesoscale effects (hillslope form, total availability of sediment, seasonality of winds, etc.) determine the distribution of overall erosional energy and the location of active and relict forms.

Laity, J. E.↗
NASA NTRS1992

A distributed system for visualizing and analyzing multivariate and multidisciplinary data

The Linked Windows Interactive Data System (Link Winds) is being developed with NASA support. The objective of this proposal is to adapt and apply that system in a complex network environment containing elements to be found by scientists working multidisciplinary teams on very large scale and distributed data sets. The proposed three year program will develop specific visualization and analysis tools, to be exercised locally and remotely in the Link Winds environment, to demonstrate visual data analysis, interdisciplinary data analysis and cooperative and interactive televisualization and analysis of data by geographically separated science teams. These demonstrations will involve at least two science disciplines with the aim of producing publishable results.

Jacobson, Allan S.↗
NASA NTRS1977

Comparisons of Theoretical and Experimental Pressure Distributions on an Arrow-Wing Configuration at Subsonic, Transonic, and Supersonic Speeds

A wind tunnel test of an arrow wing body configuration consisting of flat and twisted wings, as well as a variety of leading- and trailing-edge control surface deflection, has been conducted at Mach numbers from 0.40 to 2.50 to provide an experimental data base for comparison with theoretical methods. Theory-to-experiment comparisons of detailed pressure distributions have been made using current state-of-the-art attached- and separated-flow methods. The purpose of these comparisons was to delineate conditions under which these theories are valid for aeroelastic calculations and to explore the use of empirical methods to correct the theoretical methods where theory is deficient. It was determined that current state-of-the-art attached flow and empirical methods were inadequate to predict aeroelastic loads for this configuration.

Manro, M. E.↗
DOE OSTI2024

Secular Outflows from Long-Lived Neutron Star Merger Remnants

We study mass ejection from a binary neutron star merger producing a long-lived massive neutron star remnant with general-relativistic neutrino-radiation hydrodynamics simulations. In addition to outflows generated by shocks and tidal torques during and shortly after the merger, we observe the appearance of a wind driven by spiral density waves in the disk. This spiral-wave-driven outflow is predominantly located close to the disk orbital plane and have a broad distribution of electron fractions. At higher latitudes, a high electron-fraction wind is driven by neutrino radiation. The combined nucleosynthesis yields from all the ejecta components is in good agreement with Solar abundance measurements.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Solar PV, Wind Generation, and Load Forecasting Dataset for ERCOT 2018: Performance-Based Energy Resource Feedback, Optimization, and Risk Management (P.E.R.F.O.R.M.)

This report describes the Advanced Research Projects Agency-Energy Performance-Based Energy Resource Feedback, Optimization, and Risk Management (PERFORM) Electric Reliability Council of Texas (ERCOT) dataset consisting of load, solar, and wind deterministic and probabilistic forecasts at three timescales. This dataset consists of 1 year of time-coincident load, wind, and solar actuals and probabilistic forecasts for a region similar to ERCOT. All the data are stored in Hierarchical Data Format 5 (HDF5) files and have been uploaded to an Amazon Web Services repository. The ERCOT data set has 2 years (2017, 2018) of actuals and 1 year (2018) of probabilistic forecasts. These data are provided at various spatial (i.e., site-level, zone-level, and system-level) and temporal scales (i.e., day-ahead, intraday, and intra-hour). Specifically, data are provided for 125 existing wind sites, 22 existing solar sites, 139 proposed wind sites, and 204 proposed solar sites.

14 SOLAR ENERGY↗
NASA NTRS2000

A Dynamical Model for The Jupiter Thermocline

A new conceptual model for the observed banded wind structure of the giant outer planets is proposed, assuming a smoothly distributed potential vorticity (PV) atop a layer of deeply seated, latitudinally variable stratification. With a vanishing horizontal entropy contrast presumably enforced at the bottom of the flow layer by the underlying convection, the thermal-wind balance of observed cloud-top motions implies a mapping of constant potential temperature surfaces, nearly vertical at upper tropospheric levels, down to a deeper, flatter, but variably sloped 'thermocline.' For a generally colder-poleward distribution of isentropes consistent with the strong equatorial jets of both Jupiter and Saturn, this kind of mapping would also imply a poleward decreasing static stability. The proposed temperature-stability distribution is just the reverse of the Earth's troposphere, where the strongest latitudinal potential temperature gradients are at the bottom instead of the top, with static stability generally increasing toward the pole. The warmer-stabler correlation for Jupiter would be consistent, however, with a nearly monotonic distribution of PV from low to high latitudes, over planetary scales for which the planetary vorticity dominates the relative vorticity of the jets. In this way efficient PV mixing for the isentropically bounded thermocline can account for the dynamical maintenance of the cyclonic flanks of the equatorial jet. Over latitudinal intervals comparable to the internal deformation scale, however, the gradient of the absolute vorticity is dominated by the flow curvature, with the local latitudinal gradient of the static stability proportional to the local potential temperature gradient and therefore the local variation in geostrophic velocity. The resulting correlation of velocities and vorticity gradients implies an alternation of the flow over the internal deformation radius set by the vertical entropy contrast.

Allison, Michael↗
DOE OSTI2022

Wind and Solar Hybrid Power Plants for Energy Resilience

Wind-solar-storage hybrid power plants represent a significant and growing share of new proposed projects in the United States (U.S.). Their uptake is supported by increasing renewable energy market share, technical abilities for dispatch and control, and decreasing wind, solar, and battery storage costs. Simultaneously, generation and storage resources are increasingly used in distributed power systems. While concerns around the reliability of the aging, transforming U.S. electric grid are growing, diversifying energy resources through hybridization or spatial distribution provides an opportunity to enhance power system resilience compared to single-source generation. Understanding where to build hybrids for resilience value, rather than bulk power supply, has not been fully explored in previous studies. Therefore, in this study, we complete a national complementarity analysis to identify areas in the U.S. that are particularly suited for wind-solar hybrid power plant development. We show the importance of seasonal and diurnal patterns in assessing complementarity, and identify that regions in the Great Plains, Midwest, and Southeast are particularly suited for hybrid power plants. We demonstrate the resilience value of hybridization for a reference system based near Memphis, Tennessee, and show optimal sizing of wind, solar, and storage assets given 1.0 and 0.9 critical load factors. Results indicate that pairing wind and solar assets better meet constant load demand and reduce storage requirements compared to solar alone. These results enable future work integrating complementarity metrics in resilience frameworks and indicate a need for more finer resolution of local resource, demand, and hazard data.

14 SOLAR ENERGY↗
DOE OSTI2024

Transitioning to Hybrid Power Plants

Hybrid power plants are power generation systems that combine two or more types of electricity generation or storage, creating systems where the optimal dispatch provides more benefits that the sum of the individual components can. These plants exemplify the interconnected challenges of grid modernization. On one hand, rapid increase in deployment and enhanced controllability of renewable energy assets is needed to meet clean energy targets, but on the other, increasing electrification makes it more difficult to manage load and growth in the number of endpoints and stakeholders involved with hybrid plants complicates asset management and cybersecurity. This talk will cover trends in hybrid power plant technologies and deployments, identify future prospects for hybrid systems, and discuss the challenges and research opportunities that exist to transition from the traditional power grids of today to smart, distributed, hybrid power grids we may see in the next few decades.

14 SOLAR ENERGY↗
NASA NTRS1991

Global heating distributions for January 1979 calculated from GLA assimilated and simulated model-based datasets

This study surveys the large-scale distribution of heating for January 1979 obtained from five sources of information. Through intercomparison of these distributions, with emphasis on satellite-derived information, an investigation is conducted into the global distribution of atmospheric heating and the impact of observations on the diagnostic estimates of heating derived from assimilated datasets. The results indicate a substantial impact of satellite information on diagnostic estimates of heating in regions where there is a scarcity of conventional observations. The addition of satellite data provides information on the atmosphere's temperature and wind structure that is important for estimation of the global distribution of heating and energy exchange.

Schaack, Todd K.↗
NASA NTRSDate not supplied

Energy-Optimized Path Planning for Uas in Varying Winds Via Reinforcement Learning

In this paper we propose a reinforcement learning (RL) algorithm for path planning of Unmanned Aviation Vehicles (UAVs) under varying wind conditions. Solutions to UAV path planning problems are becoming increasingly necessary as autonomous UAVs continue to enter commercial and government spaces. Path-planning is inherently challenging, as UAVs need to account for dynamically changing flying conditions such as weather, obstacle or no-fly zones, degraded vehicle health, and off-nominal battery power consumption. Machine learning methods such as reinforcement learning (RL) have the potential to revolutionize how vehicles navigate in such uncertain environments. In this study, we compute UAV trajectories from a pre-determined starting position to a target cell within a 7X7 grid environment by optimizing parameters for mission assurance and safety limits in addition to the energy consumption and operation time. The UAV navigates the grid by taking actions to move in any of the eight cardinal and inter-cardinal directions, under constant thrust profile. The resultant UAV state is sampled from a probability distribution which accounts for the UAV’s action, local wind velocity, and the presence of obstacles or boundaries. As the unmanned airspace gets more complex due to multiple vehicles and environmental uncertainties, trade-offs between energy consumption, operation time, risk tolerance, and mission assurance need to be made. Our Markov Decision Process (MDP) environment model can capture any combination of these in the optimization objective, making it novel compared to other work in the field.

trajectory planning↗
NASA NTRS1984

Low altitude wind shear statistics derived from measured and FAA proposed standard wind profiles

Wind shear statistics were calculated for a simulated data set using wind profiles proposed as a standard and compared to statistics derived from measured wind profile data. Wind shear values were grouped in altitude bands of 100 ft between 100 and 1400 ft, and in wind shear increments of 0.025 kt/ft between + or - 0.600 kt/ft for the simulated data set and between + or - 0.200 kt/ft for the measured set. No values existed outside the + or - 0.200 kt/ft boundaries for the measured data. Frequency distributions, means, and standard deviations were derived for each altitude band for both data sets, and compared. Also, frequency distributions were derived for the total sample for both data sets and compared. Frequency of occurrence of a given wind shear was about the same for both data sets for wind shears, but less than + or 0.10 kt/ft, but the simulated data set had larger values outside these boundaries. Neglecting the vertical wind component did not significantly affect the statistics for these data sets. The frequency of occurrence of wind shears for the flight measured data was essentially the same for each altitude band and the total sample, but the simulated data distributions were different for each altitude band. The larger wind shears for the flight measured data were found to have short durations.

Dunham, R. E., Jr.↗
NASA NTRS1988

The outer atmospheres and winds of T Tau and RU Lupi

Emission line fluxes were used to establish the emission measure distribution for T Tau and RU Lupi. Intersystem lines are used to constrain the electron density in the emitting regions. These are compared with the results of Alfven wave driven wind models. Observed emission line widths and absorption components formed in the stellar winds are also compared with the theoretical predictions. It is concluded that the transition region lines are not formed in the wind and that the large widths of these emission lines are caused by nonthermal turbulent motions. However, the intersystem lines formed at Te less than or = 10,000 K indicate the presence of a lower density region, identified with the wind. Alfven-wave driven winds, with T max = 10,000 K long damping lengths, and high initial wave amplitudes may be able to account for the observed characteristics.

Jordan, C.↗
NASA NTRS1923

Pressure Distribution over Thick Airfoils - Model Tests

This investigation was undertaken to study the distribution of loading over thick wings of various types. The unloading on the wing was determined by taking the pressure at a number of holes on both the upper and lower surfaces of a model wing in the wind tunnel. The results from these tests show, first, that the distribution of pressure over a thick wing of uniform section is very little different from that over a thin wing; second, that wings tapering either in chord or thickness have the lateral center of pressure, as would be expected, slightly nearer the center of the wings; and, third, that wings tapering in plan form and with a section everywhere proportional to the center section may be considered to have a loading at any point which is proportional to the chord when compared to a wing with a similar constant section. These tests confirm the belief that wings tapering both in thickness and plan form are of considerable structural value because the lateral center of pressure is thereby moved toward the center of the span.

Norton, F H↗