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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Modifications of magnetohydrodynamics as applied to the solar wind

The effect of including the Braginskii viscous stress tensor in magnetohydrodynamics is remarked upon. It is shown that semiquantitative agreement with a recently observed anisotropy in the turbulent solar wind spectrum can be achieved in this way. The modifications of the dynamical equations are simple enough to permit their inclusion in numerical codes. The effects of large 'ion parallel viscosities' also may be significant for plasmas in quite different regimes than the solar wind.

Montgomery, David↗
DOE OSTI2023

Large-eddy simulations of turbulent flows in arrays of helical- and straight-bladed vertical-axis wind turbines

Effects of helical-shaped blades on the flow characteristics and power production of finite-length wind farms composed of vertical-axis wind turbines (VAWTs) are studied numerically using large-eddy simulation (LES). Two helical-bladed VAWTs (with opposite blade twist angles) are studied against one straight-bladed VAWT in different array configurations with coarse, intermediate, and tight spacings. Statistical analysis of the LES data shows that the helical-bladed VAWTs can improve the mean power production in the fully developed region of the array by about 4.94%–7.33% compared with the corresponding straight-bladed VAWT cases. The helical-bladed VAWTs also cover the azimuth angle more smoothly during the rotation, resulting in about 47.6%–60.1% reduction in the temporal fluctuation of the VAWT power output. Using the helical-bladed VAWTs also reduces the fatigue load on the structure by significantly reducing the spanwise bending moment (relative to the bottom base), which may improve the longevity of the VAWT system to reduce the long-term maintenance cost.

17 WIND ENERGY↗
NASA NTRS1978

Numerical simulation of MHD shock waves in the solar wind

The effects of the interplanetary magnetic field on the propagation speed of shock waves through an ambient solar wind are examined by numerical solutions of the time-dependent nonlinear equations of motion. The magnetic field always increases the velocity of strong shocks. Although the field may temporarily slow down weak shocks inside 1 AU, it eventually also causes weak shocks to travel faster than they would without the magnetic field at larger distances. Consistent with the increase in the shock velocity, the gas pressure ratio across a shock is reduced considerably in the presence of the magnetic field. The numerical method is used to simulate (starting at 0.3 AU) the large deceleration of a shock observed in the lower corona by ground-based radio instrumentation and the more gradual deceleration of the shock in the solar wind observed by the Pioneer 9 and Pioneer 10 spacecraft.

Steinolfson, R. S.↗
DOE OSTI2015

Understanding the El Niño-like Oceanic Response in the Tropical Pacific to Global Warming

The enhanced central and eastern Pacific SST warming and the associated ocean processes under global warming are investigated using the ocean component of the Community Earth System Model (CESM), Parallel Ocean Program version 2 (POP2). The tropical SST warming pattern in the coupled CESM can be faithfully reproduced by the POP2 forced with surface fluxes computed using the aerodynamic bulk formula. By prescribing the wind stress and/or wind speed through the bulk formula, the effects of wind stress change and/or the wind-evaporation-SST (WES) feedback are isolated and their linearity is evaluated in this ocean-alone setting. Result shows that, although the weakening of the equatorial easterlies contributes positively to the El Niño-like SST warming, 80% of which can be simulated by the POP2 without considering the effects of wind change in both mechanical and thermodynamic fluxes. This result points to the importance of the air-sea thermal interaction and the relative feebleness of the ocean dynamical process in the El Niño-like equatorial Pacific SST response to global warming. On the other hand, the wind stress change is found to play a dominant role in the oceanic response in the tropical Pacific, accounting for most of the changes in the equatorial ocean current system and thermal structures, including the weakening of the surface westward currents, the enhancement of the near-surface stratification and the shoaling of the equatorial thermocline. Interestingly, greenhouse gas warming in the absence of wind stress change and WES feedback also contributes substantially to the changes at the subsurface equatorial Pacific. Further, this warming impact can be largely replicated by an idealized ocean experiment forced by a uniform surface heat flux, whereby, arguably, a purest form of oceanic dynamical thermostat is revealed.

El Niño-like response↗
NASA NTRS1972

Wind-tunnel Investigation of Effects of Rear Upper Surface Modification on a NASA Supercritical Airfoil

Wind tunnel tests were conducted at Mach numbers from 0.60 to 0.81 to examine the effects on supercritical airfoil of modifying the rear upper surface to reduce the magnitude of an intermediate off design second velocity peak. The modification was accomplished by increasing the upper surface curvature around the 50 percent chord station and reducing the curvature over approximately the rearmost 30 percent of the airfoil while maintaining the same trailing edge thickness.

Harris, C. D.↗
NASA NTRS1989

Solar wind and high energy particle effects in the middle atmosphere

The solar wind variability and high energy particle effects in the neutral middle atmosphere are not much known. These factors are important in the high latitude upper mesosphere, lower thermosphere energy budget. They influence temperature, composition (minor constituents of nitric oxide, ozone), circulation (wind system) and airflow. The vertical and latitudinal structures of such effects, mechanisms of downward penetration of energy and questions of energy abundance are largely to be solved. The most important recent finding seems to be the discovery of the role of highly relativistic electrons in the middle atmosphere at L = 3 - 8 (Baker et al., 1987). The solar wind and high energy particle flux variability appear to form a part of the chain of possible Sun-weather (climate) relationships. The importance of such studies in the nineties is emphasized by their role in big international programs STEP and IGBP - Global Change.

Lastovicka, Jan↗
DOE OSTI2022

International assessment of priority environmental issues for land-based and offshore wind energy development

Non-technical summary A substantial increase in wind energy deployment worldwide is required to help achieve international targets for decreasing global carbon emissions and limiting the impacts of climate change. In response to global concerns regarding the environmental effects of wind energy, the International Energy Agency Wind Technical Collaborative Program initiated Task 34 – Working Together to Resolve Environmental Effects of Wind Energy or WREN. As part of WREN, this study performed an international assessment with the global wind energy and environmental community to determine priority environmental issues over the next 5‒10 years and help support collaborative interactions among researchers, developers, regulators, and stakeholders. Technical summary A systematic assessment was performed using feedback from the international community to identify priority environmental issues for land-based and offshore wind energy development. Given the global nature of wind energy development, feedback was of interest from all countries where such development is underway or planned to help meet United Nations Intergovernmental Panel on Climate Change targets. The assessment prioritized environmental issues over the next 5–10 years associated with wind energy development and received a total of 294 responses from 28 countries. For land-based wind, the highest-ranked issues included turbine collision risk for volant species (birds and bats), cumulative effects on species and ecosystems, and indirect effects such as avoidance and displacement. For offshore wind, the highest-ranked issues included cumulative effects, turbine collision risk, underwater noise (e.g. marine mammals and fish), and displacement. Emerging considerations for these priorities include potential application to future technologies (e.g. larger turbines and floating turbines), new stressors and species in frontier regions, and cumulative effects for multiple projects at a regional scale. For both land-based and offshore wind, effectiveness of minimization measures (e.g. detection and deterrence technologies) and costs for monitoring, minimization, and mitigation were identified as overarching challenges. Social media summary Turbine collisions and cumulative effects among the international environmental priorities for wind energy development.

17 WIND ENERGY↗
NASA NTRS1979

Effect on head-wind profiles and mean head-wind velocity on landing capacity flying constant-airspeed and constant-groundspeed approaches

A study was conducted to determine the effect of head-wind profiles and mean head-wind velocities on runway landing capacity for airplanes flying constant-airspeed and constant-groundspeed approaches. It was determined that when the wind profiles were encountered with the currently used constant airspeed approach method, the landing capacity was reduced. The severity of these reductions increased as the mean head-wind value of the profile increased. When constant-groundspeed approaches were made in the same wind profiles, there were no losses in landing capacity. In an analysis of mean head winds, it was determined that in a mean head wind of 35 knots, the landing capacity using constant-airspeed approaches was 13% less than for the no wind condition. There were no reductions in landing capacity with constant-groundspeed approaches for mean head winds less than 35 knots. This same result was observed when the separation intervals between airplanes was reduced.

Hastings, E. C., Jr.↗
NASA NTRS1981

A theory for predicting boundary impedance and resonance frequencies of slotted-wall wind tunnels, including plenum effects

Wave-induced resonance associated with the geometry of wind-tunnel test sections can occur. A theory that uses acoustic impedance concepts to predict resonance modes in a two dimensional, slotted wall wind tunnel with a plenum chamber is described. The equation derived is consistent with known results for limiting conditions. The computed resonance modes compare well with appropriate experimental data. When the theory is applied to perforated wall test sections, it predicts the experimentally observed closely spaced modes that occur when the wavelength is not long compared with he plenum depth.

Barger, R. L.↗
NASA NTRS2016

UAS Air Traffic Controller Acceptability Study-2: Effects of Communications Delays and Winds in Simulation

This study evaluated the effects of Communications Delays and Winds on Air Traffic Controller ratings of acceptability of horizontal miss distances (HMDs) for encounters between UAS and manned aircraft in a simulation of the Dallas-Ft. Worth East-side airspace. Fourteen encounters per hour were staged in the presence of moderate background traffic. Seven recently retired controllers with experience at DFW served as subjects. Guidance provided to the UAS pilots for maintaining a given HMD was provided by information from self-separation algorithms displayed on the Multi-Aircraft Simulation System. Winds tested did not affect the acceptability ratings. Communications delays tested included 0, 400, 1200, and 1800 msec. For longer communications delays, there were changes in strategy and communications flow that were observed and reported by the controllers. The aim of this work is to provide useful information for guiding future rules and regulations applicable to flying UAS in the NAS.

Comstock, James R., Jr.↗
DOE OSTI2018

Effective Quantification of Wind-Speed Variability at Different Temporal Scales

RCoV, a statistically robust and resistant metric, effectively characterizes and correlates the spreads of the distributions of wind resources and wind-energy productions. Using RCoV, a wind farm with high wind-speed fluctuations possesses high variations in wind-energy generation and vice versa. Because the long-term correlations between the wind-speed and energy-production interannual variabilities are weak and decrease with the length of data, we do not recommend calculating variabilities with yearly mean data. Skewness and kurtosis drastically change with averaging time frames. Nonzero skewness and kurtosis illustrate that the Gaussian assumption is principally inadequate in most of the United States for all averaging time frames of wind speeds.

17 WIND ENERGY↗
NASA NTRS2010

Methodology for the Assessment of 3D Conduction Effects in an Aerothermal Wind Tunnel Test

This slide presentation reviews a method for the assessment of three-dimensional conduction effects during test in a Aerothermal Wind Tunnel. The test objectives were to duplicate and extend tests that were performed during the 1960's on thermal conduction on proturberance on a flat plate. Slides review the 1D versus 3D conduction data reduction error, the analysis process, CFD-based analysis, loose coupling method that simulates a wind tunnel test run, verification of the CFD solution, Grid convergence, Mach number trend, size trends, and a Sumary of the CFD conduction analysis. Other slides show comparisons to pretest CFD at Mach 1.5 and 2.16 and the geometries of the models and grids.

Oliver, Anthony Brandon↗
NASA NTRS1971

Wind-tunnel investigation of effects of trailing-edge geometry on a NASA supercritical airfoil section

Wind-tunnel tests have been conducted at Mach numbers from 0.60 to 0.81 to determine the effects of trailing-edge geometry on the aerodynamic characteristics of a NASA supercritical airfoil shape. Variations in trailing-edge thicknesses from 0 to 1.5 percent of the chord and a cavity in the trailing edge were investigated with airfoils with maximum thicknesses of 10 and 11 percent of the chord.

Harris, C. D.↗
NASA NTRS1981

Photospheric flow and stellar winds

The effect of the photospheric outflow on the expansion of the strongly bound coronas of dwarf main-sequence stars is examined. The extended temperatures of the strongly bound coronas cause the stars to expand and form tenuous stellar winds, with a slight mean upward motion of the gas in the photosphere to replenish the mass loss through the coronal expansion. A formal solution of the time-dependent hydrodynamic equations illustrates the effects of the photospheric velocity at large distances, and the effect of blocking the upward flow in the photosphere is calculated using the sun as an example. Results indicate that the expansion of a strongly bound corona is insensitive over historical time scales to the small outflow of gas in the photosphere.

Parker, E. N.↗
NASA NTRS1984

Numerical investigation of fluid models with full electron and proton thermal conduction equations for the quiet solar wind

The effect of using full equations (rather than Fourier law expressions) for the electron and proton thermal conductivities in conjunction with community, momentum, and temperature equations for the description of spherically symmetric quiet solar wind states is investigated numerically. For this purpose a time-dependent method is used, and steady state solutions in both subsonic and supersonic regimes between the sun and 5 AU are obtained and presented. The consequences for one-fluid and two-fluid models for the solar wind are summarized and discussed.

Cuperman, S.↗
DOE OSTI2012

A Study of the Effects of Different Urban Wind Models on Dispersion Patterns Using Joint Urban 2003 Data

The Quick Urban & Industrial Complex (QUIC) Dispersion Modeling System has been developed to rapidly compute the transport and dispersion of toxic agent releases in the vicinity of buildings. It is composed of a wind solver, an 'urbanized' Lagrangian random-walk model, and a graphical user interface. QUIC has two different wind models: (a) The QUIC-URB wind solver, an empirically-based diagnostic wind model and (b) The QUIC-CFD (RANS) solver, based on the 3D Reynolds-Averaged Navier-Stokes (RANS) equations. In this paper, we discuss the effect of different wind models on dispersion patterns in dense built-up areas. The model-computed wind from the two urban wind models- QUIC-URB and QUIC-CFD are used to drive the dispersion model. The concentration fields are then compared to measurements from the Oklahoma City Joint Urban 2003 field experiment. QUIC produces high-resolution 3-D mean wind and concentration fields around buildings, in addition to deposition on the ground and building surfaces. It has options for different release types, including point, moving point, line, area, and volumetric sources, as well as dense gas, explosive buoyant rise, multi-particle size, bioslurry, and two-phase releases. Other features include indoor infiltration, a pressure solver, outer grid simulations, vegetative canopies, and population exposure calculations. It has been used for biological agent sensor siting in cities, vulnerability assessments for heavier-than-air chemical releases at industrial facilities, and clean-up assessments for radiological dispersal device (RDD) releases in cities (e.g., see Linger et al., 2005; Brown, 2006a, b). QUIC has also been used for dust transport studies (Bowker et al., 2007a) and for the impact of highway sound barriers on the transport and dispersion of vehicle emissions (Bowker et al., 2007b).

54 ENVIRONMENTAL SCIENCES↗