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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
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.↗
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↗
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.↗
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.↗
NASA NTRS1979

Effect of viscosity on wind-tunnel wall interference for airfoils at high lift

The effect of the walls of a wind tunnel on the subsonic, two-dimensional flow past airfoils at high angles of attack is studied theoretically and experimentally. The computerized analysis, which is based on iteratively coupled potential-flow, boundary-layer, and separated-flow analyses, includes determining the effect of viscosity and flow separation on the airfoil/wall interaction. Predictions of the effects of wind-tunnel wall on the lift of airfoils are compared with wall corrections based on inviscid image analyses, and with experimental data. These comparisons are made for airfoils that are large relative to the size of the test section of the wind tunnel. It is shown that the inviscid image modeling of the wind-tunnel interaction becomes inaccurate at lift coefficients near maximum lift or when the airfoil/wall interaction is particularly strong. It is also shown that the present method of analysis (which includes boundary-layer and flow-separation effects) will provide accurate wind-tunnel wall corrections for lift coefficients up to maximum lift.

Olson, L. E.↗
NASA NTRS2003

A Wind Tunnel Study of Icing Effects on a Business Jet Airfoil

Aerodynamic wind tunnel tests were conducted to study the effects of various ice accretions on the aerodynamic performance of a 36-inch chord, two-dimensional business jet airfoil. Eight different ice shape configurations were tested. Four were castings made from molds of ice shapes accreted in an icing wind tunnel. Two were made using computationally smoothed tracings of two of the ice shapes accreted in the icing tunnel. These smoothed profiles were then extended in the spanwise direction to form a two-dimensional ice shape. The final two configurations were formed by applying grit to the smoothed ice shapes. The ice shapes resulted in as much as 48% reduction in maximum lift coefficient from that of the clean airfoil. Large increases in drag and changes in pitching moment were also observed. The castings and their corresponding smoothed counterparts yielded similar results. Little change in performance was observed with the addition of grit to the smoothed ice shapes. Changes in the Reynolds number (from 3 x 10(exp 6) to 10.5 x 10(exp 6) and Mach number (from 0.12 to 0.28) did not significantly affect the iced-airfoil performance coefficients.

Addy, Harold E., Jr.↗
NASA NTRS1941

Wind-tunnel investigation of effect of interference on lateral-stability characteristics of four NACA 23012 wings, an elliptical and a circular fuselage and vertical fins

Report presents the results of a wind-tunnel investigation of the effect of wing-fuselage interference on lateral-stability characteristics made in the NACA 7 by 10-foot wind tunnel on four fuselages and two fins, representing high-wing, low-wing, and midwing monoplanes. The fuselages are of circular and elliptical cross section. The wings have rounded tips and, in plan form, one is rectangular and the three are tapered 3:1 with various amounts of sweep. The rate of change in the coefficients of rolling moment, yawing moment, and lateral force with angle of yaw is given in a form to show the increment caused by wing-fuselage interference for the model with no fin and the effect of wing-fuselage interference on fin effectiveness. Results for the fuselage-fin combination and the wing tested alone are also given.

House, Rufus O↗
NASA NTRS1983

Feasibility study of a procedure to detect and warn of low-level wind shear

The wind shear program is directed toward investigating the effects of wind shear on aerodynamic performance. Combining the Joint Airport Weather Studies wind shear data with the B-57B gust gradient data, the transient scales of motion involved in wind shear aircraft accidents or mishaps are being identified. The effect of variable winds having these time scales on the aerodynamic coefficients of moist airfoils were fully investigated. Transient and spatial variation of flow over the airfoil may cause premature stall or hysteresis effects which significantly impact the lift and drag (i.e., aerodynamic coefficients). Analysis of airfoil performance subject to 4-D variable flows will be carried out.

Frost, W.↗
NASA NTRS1973

Full-scale wind-tunnel investigation of effects of slot spoilers on the aerodynamic characteristics of a light twin-engine airplane

A wind-tunnel investigation has been conducted to determine the effects of slot spoilers on the longitudinal and lateral aerodynamic characteristics of a full-scale mockup of a light twin-engine airplane. The slots were located along the leading edge of the flaps and were used to modulate the flap-induced lift as a possible means of achieving direct lift control. The data showed that the slots were effective in spoiling up to 61 percent of the flap-induced lift, but that an adverse pitching-moment change (nose up) accompanied opening the slots. Opening the slots was found to decrease slightly the downwash angle at the tail and to increase slightly the longitudinal stability of the model.

Verstynen, H. A., Jr.↗
NASA NTRS1992

Magnetized stimulated scattering in pulsar winds

The effects of stimulated scattering on a collimated high brightness temperature beam of photons traversing a relativistically streaming magnetized plasma are studied. Under the assumption that the center of the photon beam is parallel to the bulk motion, we calculate the scattering rate as a function of the angular spread of the beam and the Lorentz factor gamma. Magnetization changes the photon recoil, without which stimulated scattering has no effect. It also introduces a strong dependence on frequency and polarization: if the photon frequency matches the electron cyclotron frequency, the scattering rate of photons polarized perpendicular to the magnetic field can be substantially enhanced relative to Thomson, and if the photon frequency is much less than the cyclotron frequency, the scattering is suppressed. Applying these calculations to pulsars, we find that stimulated scattering of the radio beam in the magnetized wind believed to exist outside the light cylinder can substantially alter the spectrum and polarization state of the radio signal. We suggest that the scattering rate is so high in some pulsars that the ability of the radio signal to penetrate the pulsar magnetosphere requires modification of either the conventional model of the magnetosphere or assumptions about the effects of stimulated scattering upon a beam.

Sincell, Mark W.↗
NASA NTRS1948

Tests of a Triangular Wing of Aspect Ratio 2 in the Ames 12-foot Pressure Wind Tunnel III : the Effectiveness and Hinge Moments of a Skewed Wing-tip Flap

Results of wind-tunnel tests of a semispan model of a triangular wing of aspect ratio 2 with a skewed wing-tip flap are presented. Lift, drag, pitching-moment, and hinge-moment data are included for subsonic Mach numbers up to 0.95. The flap showed extremely high hinge moments and low effectiveness as a longitudinal control. Although less affected by compressibility, this flap is indicated to be inferior to a constant-chord flap when applied to this triangular wing.

MACH NUMBER EFFECTS - COMPLETE WINGS↗