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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 73 records · Page 4
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NASA NTRS2008

Weather Research and Forecasting Model Wind Sensitivity Study at Edwards Air Force Base, CA

NASA prefers to land the space shuttle at Kennedy Space Center (KSC). When weather conditions violate Flight Rules at KSC, NASA will usually divert the shuttle landing to Edwards Air Force Base (EAFB) in Southern California. But forecasting surface winds at EAFB is a challenge for the Spaceflight Meteorology Group (SMG) forecasters due to the complex terrain that surrounds EAFB, One particular phenomena identified by SMG is that makes it difficult to forecast the EAFB surface winds is called "wind cycling". This occurs when wind speeds and directions oscillate among towers near the EAFB runway leading to a challenging deorbit bum forecast for shuttle landings. The large-scale numerical weather prediction models cannot properly resolve the wind field due to their coarse horizontal resolutions, so a properly tuned high-resolution mesoscale model is needed. The Weather Research and Forecasting (WRF) model meets this requirement. The AMU assessed the different WRF model options to determine which configuration best predicted surface wind speed and direction at EAFB, To do so, the AMU compared the WRF model performance using two hot start initializations with the Advanced Research WRF and Non-hydrostatic Mesoscale Model dynamical cores and compared model performance while varying the physics options.

Watson, Leela R.↗
NASA NTRS1978

Solar wind models with Alfven waves

Solutions to the one-fluid solar-wind equations that include pressure and heating due to outwardly propagating Alfven waves are presented. The solutions are given for two forms of the heat flux: the classical Spitzer (1962) formula and a 'collisional' heat flux. Both high-speed and low-speed solar-wind streams are considered. A comparison of solutions with and without waves shows that the solutions without waves cannot come close to reproducing observations of total mass and energy flux at 1 AU, while those with waves are capable of bringing nearly all flow variables into reasonable agreement with the observations. The required wave flux is found to be about 100,000 erg/sq cm per sec for the high-speed streams and an order of magnitude less for the low-speed streams. It is concluded that the pressure and heating due to outwardly propagating Alfven waves are important elements of solar-wind dynamics that cannot be neglected and that wave heating is especially important for the protons in high-speed streams.

Jacques, S. A.↗
NASA NTRS2020

Development of an Aeroservoelastic Model for Gust Load Alleviation of the NASA Common Research Model Wind Tunnel Experiment

As aircraft move to using composite materials as their primary structure they become lighter and more flexible as well. This presents some significant challenges in association with gust load alleviation. In this paper we develop an aeroservoelastic model for use in developing controllers that utilize distributed control surfaces for active gust load alleviation in a set of wind tunnel experiments. The model is based on an preexisting aeroelastic wing tunnel model and compares the baseline functionality to it. We also provide simple full state feedback simulations for the model.

Cramer, Nick↗
NASA NTRS1989

Radiation-driven winds of hot stars. VI - Analytical solutions for wind models including the finite cone angle effect

Analytical solutions for radiation-driven winds of hot stars including the important finite cone angle effect (see Pauldrach et al., 1986; Friend and Abbott, 1986) are derived which approximate the detailed numerical solutions of the exact wind equation of motion very well. They allow a detailed discussion of the finite cone angle effect and provide for given line force parameters k, alpha, delta definite formulas for mass-loss rate M and terminal velocity v-alpha as function of stellar parameters.

Kudritzki, R. P.↗
NASA NTRSDate not supplied

Summary of the NASA Semi-Span High-Lift Common Research Model Wind Tunnel Test at the QinetiQ 5-Metre Low-Speed Facility

A summary and selected results from experimental testing of the NASA 10% scale semi-span High-Lift Common Research Model (CRM-HL) at the QinetiQ 5m (5mWT) pressurized low-speed wind tunnel are presented. There were many objectives of this test, the primary being to define a set of reference configurations for dissemination and use within the CRM-HL ecosystem, one in the landing configuration and one in the takeoff configuration. A database of force, moment, pressure and surface flow visualization data was collected to support several objectives: aerodynamic sensitivity to high-lift device positioning, Reynolds number effects on configuration selection, isolation of the effects of various components of the reference configuration e.g. landing gear, nacelle, horizontal tail, etc., and limited repeatability data for uncertainty quantification assessment. Some results were compared to limited data collected at the NASA Langley Research Center 14x22 wind tunnel to assess half-model effects and facility differences. Half-model effects were further studied with use of floor blowing to change boundary layer profile and assess effects on model aerodynamics. Flow visualization data were gathered with fluorescent mini-tufts and UV oil. Finally, test time was spend working on the development of new Particle Image Velocimetry (PIV) and Model Deformation Measurement (MDM) capabilities at the 5mWT facility.

Ashley Evans↗
NASA NTRS1949

Longitudinal Stability and Control Characteristics of a Semispan Wind-Tunnel Model of the XF7U-1 Airplane and a Comparison with Complete-Model Wind-Tunnel Tests and Semispan-Model Wing-Flow Tests

An investigation was conducted on an 0.08-scale semispan model of the Chance Vought XF7U-1 airplane in the Langley high-speed 7- by 10-foot tunnel in the Mach number range from 0.40 to 0.97. The results are compared with those obtained with an 0.08-scale sting-mounted complete model tested in the same tunnel and with an 0.026-scale semispan model tested by the wing-flow method. The lift-curve slopes obtained for the 0.08-scale semispan model and the 0.026-scale wing-flow model were in good agreement but both were generally lower than the values obtained for the sting model. The results of an unpublished investigation have shown that tunnel-wall boundary-layer and strut-leakage effects can came the difference noted between the lift-curve slopes of the sting and the semispan data. Fair agreement was obtained among the data of the three models as regard the variation of pitching-moment coefficients with lift coefficient. The agreement between the complete and the semispan models was more favorable with the vertical fine on, because the wall-boundary-layer and strut leakage effects were less severe. In the Mach number range between 0.94 and 0.97, ailavator-control reversal was indicated in the wing-flow data near zero lift; Whereas, these same trends were indicated in the larger scale semispan data at somewhat higher lift coefficients.

Goodson, Kenneth W.↗
NASA NTRS1972

A solar-wind model including proton thermal anisotropy.

A relatively simple model is proposed to study the magnetohydrodynamic expansion of the solar wind. The interplanetary space is divided into an 'inner region' and an 'outer region.' In the inner region the solar wind is one-fluid and thermally isotropic. The solar-wind protons are assumed to be completely collisionless in the outer region. Thus the solar wind is two-fluid in nature, and the protons are thermally anisotropic in the outer region. It is assumed that throughout the interplanetary space electrons are thermally isotropic due to collisions or other processes. The electron heat flux is supposed to obey the well-known relationships that the flux is parallel to the magnetic-field vector and is directly proportional to the spatial derivative of the electron temperature.

Whang, Y. C.↗
NASA NTRS1975

Wind modeling and lateral control for automatic landing

For the purposes of aircraft control system design and analysis, the wind can be characterized by a mean component which varies with height and by turbulent components which are described by the von Karman correlation model. The aircraft aero-dynamic forces and moments depend linearly on uniform and gradient gust components obtained by averaging over the aircraft's length and span. The correlations of the averaged components are then approximated by the outputs of linear shaping filters forced by white noise. The resulting model of the crosswind shear and turbulence effects is used in the design of a lateral control system for the automatic landing of a DC-8 aircraft.

Holley, W. E.↗
NASA NTRS1992

Stochastic stellar wind models - Evolved stars

Observational, semiempirical, and theoretical results are presented for individual cool giants and supergiants which show that stochastic stellar wind flows are an extremely important feature in these stars. It is shown that the status of the existing theoretical models is very uncertain, due to the fact that appropriate models must simultaneously take into account a broad variety of strongly coupled physical processes. The potentially important physical processes include global oscillation modes; convection; magnetic fields; the generation, propagation, and interaction of stochastic waves; three-dimensional radiative transfer effects; time-dependent hydrogen ionization; thermal bifurcation and instabilities; and nonequilibrium chemistry, particularly the formation and destruction of molecules and dust.

Cuntz, Manfred↗
NASA NTRS1986

A two-fluid solar wind model with Alfven waves - Parameter study and application to observations

The effects of Alfven waves from the inner corona on the solar wind density profile, flow velocity and on the random motion of protons are studied. Different base densities, temperatures, and wave velocity amplitudes, as well as different flow geometries, are considered. The model calculations are compared to simultaneous observations of the electron density profile and the resonantly scattered Lyman alpha line. Present observations, out to 4 solar radii, can be used to place limits on the coronal base density and temperature, and put an upper limit on the wave amplitude. It is pointed out that future observations of the electron density and the Lyman alpha line, out to larger heliocentric distances, and of lines from heavier elements, should be used to place more stringent constraints on the amplitudes of MHD waves in the corona.

Esser, R.↗
NASA NTRS1980

Planetary boundary-layer wind model evaluation at a mid-Atlantic coastal site

Detailed measurements of the mean flow and turbulence were made with the use of a micrometeorological facility consisting of an instrumented 76-m tall tower located within a 100-m distance from the Atlantic Ocean at Wallops Island, Virginia. Under moderately strong wind conditions, the popular neutral boundary layer flow model fails to provide an adequate description of the actual flow. In addition to detailed flow information for all wind directions, averages of the important flow parameters used for design such as vertical distribution of mean velocity, turbulence intensities and turbulence integral scales were presented for wind direction sectors with near uniform upstream terrain. Power spectra of the three velocity components for the prevailing northwesterly and southerly winds are discussed.

Tieleman, H. W.↗
NASA NTRS1991

A tidal wind model for 85-120 km based on CIRA-86 - A feasibility study

The feasibility of deriving a climatology of the diurnal variations of the wind in the 85-120 km region from the tidal components of density, temperature and composition contained in the new COSPAR CIRA-86 is examined. The CIRA density and temperature model is employed to derive the eastward and northward pressure gradient forces that serve as the forcing functions in the coupled momentum equations. At midlatitudes, the model shows some of the general features observed in the radar tidal data, e.g., the dominant semidiurnal tide with increasing amplitude with height and clockwise (counterclockwise) rotation of the velocity vector seen in the Northern (Southern) Hemisphere.

Fleming, E. L.↗
NASA NTRS1978

The spiral field inhibition of thermal conduction in two-fluid solar wind models

The paper reports on two-field models which include the inhibition of thermal conduction by the spiraling interplanetary field to determine whether any of the major conclusions obtained by Nerney and Barnes (1977) needs to be modified. Comparisons with straight field line models reveal that for most base conditions, the primary effect of the inhibition of thermal conduction is the bottling-up of heat in the electrons as well as the quite different temperature profiles at a large heliocentric radius. The spiral field solutions show that coronal hole boundary conditions do not correspond to states of high-speed streams as observed at 1 AU. The two-fluid models suggest that the spiral field inhibition of thermal conduction in the equatorial plane will generate higher gas pressures in comparison with flows along the solar rotation axis (between 1 and 10 AU). In particular, massive outflows of stellar winds, such as outflow from T Tauri stars, cannot be driven by thermal conduction. The conclusions of Nerney and Barnes remain essentially unchanged.

Nerney, S.↗
NASA NTRS1988

Time-dependent polar wind modeling

In the presence of a strong magnetic field (such as the geomagnetic field) the plasma tends to flow along the magnetic-field lines; therefore, in most ionospheric flow calculations the use of the gyrotropic approximation is justified. Here, it is shown that the gyrotropic 20-moment approximation is equivalent to the gyrotropic 16-moment approximation. Consideration is then given to return-current-generated polar wind transients. Ionospheric return currents generate significant downward heavy ion flows in the topside ionosphere with peak values well exceeding 10 to the 8th/sq cm sec. When the return current ceases, the polar ionosphere rapidly returns to its previous equilibrium state. During the recovery phase of the return-current event, an upward-propagating heavy-ion transient is formed, which is mainly characterized by a relatively short O(+) upwelling event. The H(+) escape flux remains a relatively constant (within 10-20 percent) during field-aligned-current events.

Gombosi, T. I.↗
NASA NTRS2012

Composite Pressure Vessel Variability in Geometry and Filament Winding Model

Composite pressure vessels (CPVs) are used in a variety of applications ranging from carbon dioxide canisters for paintball guns to life support and pressurant storage on the International Space Station. With widespread use, it is important to be able to evaluate the effect of variability on structural performance. Data analysis was completed on CPVs to determine the amount of variation that occurs among the same type of CPV, and a filament winding routine was developed to facilitate study of the effect of manufacturing variation on structural response.

Green, Steven J.↗
NASA NTRS1972

A numerical study of a three dimensional spherical thermospheric density and wind model

Numerical calculations of the generation and propagation of the two important fundamental symmetric tidal wave modes - the diurnal mode (1, 1, 1,) and the semidiurnal mode (2, 2, 2) - were performed applying a realistic model thermosphere and taking into account heat conduction and the temporally and spatially varying ion-neutral collision number. Both wave modes are predominantly generated by the solar EUV heat input. It is shown that the latitude structure of the (1, 1, 1)-mode which is identical with the Hough function(1, -1) within the lower non-dissipative atmosphere degenerates into the spherical function P sub 1, 1 at thermospheric heights. The pressure field of this mode constitutes the observed pressure bulge of the thermosphere, the diurnal component of which peaks at 15 h L. T. The electric polarization field of the geomagnetic Sq current generates a significant fraction of this wave mode at F layer heights. This wave component shifts the total horizontal wind system to earlier times by about 1 hour in agreement with ionospheric observations. The latitude structure of the (2, 2, 2) mode is identical with the Hough function (2, 2) within the lower non-dissipative atmosphere. It degenerates to the spherical function P sub 2, 2 at thermospheric heights.

Volland, H.↗