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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

The Effect of Large-scale Magnetic Fluctuations on Energetic Particle Profiles across Interplanetary Shocks

In situ observations of energetic particles associated with interplanetary (IP) shocks, known as energetic storm particle (ESP) events, often show time-intensity profiles quite different from predictions of classical diffusive shock acceleration theory. We use numerical simulations, including test-particle simulations and hybrid simulations (with fluid electrons and kinetic protons) for shocks propagating into a turbulent magnetic field to study the ESP intensity-time profiles across a strong IP shock. We find that several types of energetic particle intensity profiles similar to in situ observations can be produced in our simulations. The peak of energetic particle count is often near, but can be shifted from, the locations of the shock front, with the peak usually being observed downstream of the shock. These findings may help understand particle acceleration at both traveling IP shocks and shocks in other heliospheric and astrophysical environments.

Lo, Ming-Yuan [New Mexico Consortium (NMC), Los Al↗
NASA NTRS1973

The effect of large-scale eddies on climatic change.

A parameterization for the fluxes of sensible heat by large-scale eddies developed in an earlier paper is incorporated into a model for the mean temperature structure of an atmosphere including only these fluxes and the radiative fluxes. The climatic changes in this simple model are then studied in order to assess the strength of the dynamical feedback and to gain insight into how dynamical parameters may change in more sophisticated climatic models. The model shows the following qualitative changes: (1) an increase in the solar constant leads to increased static stability, decreased dynamic stability, and stronger horizontal and vertical winds; (2) an increase in the amount of atmospheric absorption leads to decreased static and dynamic stability, and stronger horizontal and vertical winds; and (3) an increase in rotation rate leads to greater static and dynamic stability, weaker horizontal winds, and stronger vertical winds.

Stone, P. H.↗
NASA NTRS1975

Data report for tests on the heat transfer effects of the 0.0175 scale Rockwell International Space Shuttle Vehicle model 22-OT in the AEDC 50 inch B wind tunnel (0H4B), volume 1

Results of wind tunnel heat transfer tests of 0.0175-scale Rockwell International Space Shuttle Vehicle configurations for orbiter alone, tank alone, and orbiter plus external tank are presented. Body flap shielding of SSME's during simulated entry was investigated. The tests were conducted at Mach 8 for thirteen Reynolds number.

Foster, T. F.↗
NASA NTRS1975

Data report for tests on the heat transfer effects of the 0.0175-scale Rockwell International Space Shuttle Vehicle model 22-OT in the AEDC 50-inch B wind tunnel (OH4B), volume 3

Results of wind tunnel heat transfer tests of 0.0175-scale Rockwell International Space Shuttle Vehicle configurations for orbiter alone, tank alone, and orbiter plus external tank are presented. Body flap shielding of SSME's during simulated entry was also investigated. The tests were conducted at Mach 8 for thirteen Reynolds number per foot values ranging from 0.5 million to 3.72 million.

Foster, T. F.↗
NASA NTRS1974

The effect of small-scale vertical mixing of horizontal momentum in a general circulation model

Several experiments are described in which the sub-grid-scale vertical eddy viscosity in the GISS global general circulation model was varied. The results show that large viscosities suppress large-scale eddies in middle and high latitudes, but enhance the circulation in the tropical Hadley cell and increase the extent of the tropical easterlies. Comparison with observations shows that the GISS model requires eddy viscosities about 1 sq m per sec or less to give realistic results for middle and high latitudes, and eddy viscosities about 100 sq m per sec to give realistic results for low latitudes. A plausible mechanism for the implied increase in small-scale mixing in low latitudes is cumulus convection.

Stone, P. H.↗
NASA NTRS1976

Results of an investigation of jet plume effects on a 0.010-scale model (75-OTS) of the space shuttle integrated vehicle in the 8 x 7-foot leg of the NASA/Ames unitary wind tunnel (IA82C), volume 1

The primary test objective was to define the base pressure environment of the first and second stage mated vehicle in a supersonic flow field from Mach 2.60 through 3.50 with simulated rocket engine exhaust plumes. The secondary objective was to obtain the pressure environment of the Orbiter at various vent port locations at these same freestream conditions. Data were obtained at angles of attack from -4 deg through +4 deg at zero yaw, and at yaw angles from -4 deg through +4 deg at zero angle of attack, with rocket plume sizes varying from smaller than nominal to much greater than nominal. Failed Orbiter engine data were also obtained. Elevon hinge moments and wing panel load data were obtained during all runs. Photographs of test equipment and tested configurations are shown.

Hawthorne, P. J.↗
NASA NTRS1976

Results of an investigation of jet plume effects on an 0.010-scale model (75-OTS) of the space shuttle integrated vehicle in the 9 x 7-foot leg of the NASA/Ames unitary wind tunnel (IA82B), volume 1

The base pressure environment was investigated for the first and second stage mated vehicle in a supersonic flow field from Mach 1.55 through 2.20 with simulated rocket engine exhaust plumes. The pressure environment was investigated for the orbiter at various vent port locations at these same freestream conditions. The Mach number environment around the base of the model with rocket plumes simulated was examined. Data were obtained at angles of attack from -4 deg through +4 deg at zero yaw, and at yaw angles from -4 deg through +4 deg at zero angle of attack, with rocket plume sizes varying from smaller than nominal to much greater than nominal. Failed orbiter engine data were also obtained. Elevon hinge moments and wing panel load data were obtained during all runs. Photographs of the tested configurations are shown.

Hawthorne, P. J.↗
NASA NTRS1975

The effect of intermediate-scale motions on line formation

The problem of LTE and non-LTE line formation in the presence of nonthermal velocity fields with geometric scales between the microscopic and macroscopic limits is investigated in the cases of periodic sinusoidal and sawtooth waves. For a fixed source function (the LTE case), it is shown that time-averaged line profiles progress smoothly from the microscopic to the macroscopic limits as the geometric scale of the motions increases, that the sinusoidal motions produce symmetric time-averaged profiles, and that the sawtooth motions cause a redshift. In several idealized non-LTE cases, it is found that intermediate-scale velocity fields can significantly increase the surface source functions and line-core intensities. Calculations are made for a two-level atom in an isothermal atmosphere for a range of velocity scales and non-LTE coupling parameters and also for a two-level atom and a four-level representation of Na I line formation in the Harvard-Smithsonian Reference Atmosphere (1971) solar model. It is found that intermediate-scale velocity fields in the solar atmosphere could explain the central intensities of the Na I D lines and other strong absorption lines without invoking previously suggested high electron densities.

Shine, R. A.↗
NASA NTRS1977

Electronic imaging and scanning system

Frequency-variable illumination has been used previously to provide high resolution imaging in one dimension. The paper extends the results on this imaging by frequency scanning to derive the expression for a two-dimensional image. This is the Fourier transformation, with respect to the angle and frequency of illumination, of the electric field detected in the far-field region of the object. The case is considered of a rough object and it is shown that for roughness finer than the resolution of the imaging system, the image has a granular appearance corresponding to the classical speckle effect. Large scale phase perturbations lead to the elevation displacement effect.

Jain, A.↗
NASA NTRS1979

Scaling laws and edge effects for polymer surface discharges

Specimens of Mylar sheet were exposed to a 20 kV electron beam. The resulting surface discharge arcs were photographed and the discharge current into a metal backing plate measured as a function of time. The area of the Mylar sheet was defined by a round aperture in a close-fitting metal mask, and the current pulse characteristics were plotted against area on log-log paper. The plots appear as straight lines (due to power-law behavior) with slopes of 0.50 for the peak current, 1.00 for the charge released, 1.49 for the energy and 0.55 for the pulse duration. Evidence is presented for the occurrence of banded charge distributions near grounded edges, on both Teflon and Mylar.

Balmain, K. G.↗
NASA NTRS1984

Effects of small-scale, high intensity inlet turbulence on flow in a two-dimensional diffuser

The flow through a 2D experimental diffuser with channel width 2.60 cm and divergence angle (2 theta) 9 or 20 deg is investigated experimentally for inlet Reynolds number 78,300 and velocity 43.9 m/s, with and without vertical rods to generate inlet turbulence in excess of the limits defined by Hoffmann (1981) and Hoffmann and Gonzales (1983). Measurements are obtained using a thermal wall-flow-direction probe and a single hot-wire velocity probe, and the results are presented graphically. Significant increases in the pressure-recovery coefficient of the diffuser (10 percent at 9 deg and 22 percent at 20 deg) are attributed to the action of turbulence to reduce distortion and delay separation, thus creating an altered flow condition with symmetrical velocity profiles.

Hoffmann, J. A.↗
NASA NTRS1990

The effect of small-scale roughness on the main flow profile of a laminar boundary layer

The profile distortion due to a single roughness element, to two such elements, and to many elements is investigated. Signal-averaging of the velocity difference due to the roughness being alternately present or absent is employed in order to improve accuracy. The primary objective of examining the distributed-roughness profiles for any evidence of instability-enhancing form is not met, but the results are reconsidered, and relevant hypotheses and suggestions are presented. It is noted that the reason for not meeting the objective of estimating Tollmien-Schlichting amplification from rough-wall profiles is that much of the distortion occurs close to the wall and below the element tops.

Kendall, James M., Jr.↗
NASA NTRS1993

Average effects of large-scale convection on helioseismic line widths and frequencies

The formalism of Lavely and Ritzwoller (1992) is here applied to the model of stationary large-scale solar convection developed by Glatzmaier (1984) in order to determine a characteristic giant-cell convection signature in helioseismic data. Frequency and line-width measurements are presented on spatially filtered spectra, so that references to azimuthal orders apply to the m-value of the spatial filter's spherical harmonic. Attention is given to the 'Q-bowl' pattern of large-scale convection, a systematic, apparent line-broadening.

Lavely, Eugene M.↗
NASA NTRS1956

Some Effects of Small-scale Flow Disturbance on Nozzle-burner Flames

Laminar-like and brush-like propane-air flames were obtained when wire grids were used as turbulence generators in a 1/2-inch nozzle burner. The laminar-like flames for grid-disturbed flow had a slightly higher burning velocity than "true" laminar flames (no grid used). The brush-like flames were similar to those obtained with pipe turbulent flow. Their burning-velocity dependence on a "flow disturbance" Reynolds number compared favorably with that obtained for pipe turbulent flames. Hot-wire-anemometer equipment was used to measure the flow disturbance intensity in the cold flow with and without the grids in place.

COMBUSTION, TURBULENT-FLOW↗