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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 1,351 records · Page 75

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NASA NTRS1992

Waste streams in a crewed space habitat. II

An update is presented of a compilation of generation rates and chemical compositions of potential waste streams in a typical crewed space habitat which was reported in the NASA Technical Memorandum. New topics under consideration include data obtained from Soviet literature on life support issues and data on various minor human body wastes not presented previously (saliva, Flatus, hair, finger- and toenails, dried skin and skin secretions, tears and semen). Attention is also given to the latest information on the environmental control and life support system design parameters for SSF.

Golub, Morton A.↗

NASA NTRS1992

Experimental study of cross-stream mixing in a rectangular duct

An experimental investigation of non-reacting cross-stream jet injection and mixing in a rectangular duct was conducted for application in a low emissions combustor. Planar digital imaging was used to measure concentration distributions in planes perpendicular to the duct axis. Mixing rate was measured for 45 deg slanted slot and round orifice injectors. Five areas of inquiry are discussed: (1) mixing improves continuously with increasing momentum-flux ratio; (2) given a momentum-flux ratio, there is an optimum, orifice spacing; (3) mixing is more dependent on injector geometry than mass flow ratio; (4) mixing is influenced by relative slot orientation; and (5) jet structure is different for round holes and slanted slots injectors. The utility of acquiring multipoint fluctuating properties of the flow field is also demonstrated.

Liscinsky, D. S.↗

NASA NTRS1993

Free-Stream-Capturing Metrics

Report summarizes techniques for preservation of free-stream flows in finite-volume and finite-difference flow computations involving transformations between moving and stationary coordinates. Techniques necessary for accurate computations of complicated flows; such as, computing flow about helicopter rotor by use of grid conforming to and moving with rotor blades.

Obayashi, Shigeru↗

NASA NTRS1991

The dynamics and energetics of midlatitude western boundary currents: A comparison of the Kuroshio Extension and the Gulf Stream

We will use TOPEX/POSEIDON altimetry in combination with ongoing and planned efforts, including data from the European Remote Sensing satellite (ERS-1), in situ measurements designed specifically to complement satellite altimetry, and assimilation of these several data types into eddy-resolving numerical models in order to understand the dynamics and energetics of midlatitude western boundary currents (specifically, the Gulf Stream and the Kuroshio Extension). A better understanding of the recirculation of midlatitude gyres can best be undertaken in the format of such regional, eddy-resolving experiments. Such regional programs will enhance and be enhanced by the larger scale circulation studies of the World Ocean Circulation Experiment (WOCE) as well as by global-scale eddy-resolving models that we will develop prior to the TOPEX/POSEIDON mission. This effort includes participation on the TOPEDX/POSEIDON Science Team.

Mitchell, James L.↗

NASA NTRS1992

On the asteroidal jet-stream Flora A

The problems of the virtual existence of the Flora 1, separated from the rest of the Flora family, and jet-stream Flora A (Alfven 1969) is discussed in connection with the observational selection effects. It is shown that observational selection effects operate as a whole and can be important in incomplete observational data set.

Klacka, Jozef↗

NASA NTRS1992

Activity of the Lyrid meteor stream

The activity of the Lyrid meteor stream is in most years fairly low with a visual rate at maximum (21-22 April) of 5-10 meteors per hour. Short bursts of very high Lyrid activity, with visual hourly rates of 100 or more, have sometimes been reported. These observations generally refer to faint visual meteors. The reported bursts of high activity have occurred in a very narrow interval of solar longitudes (deg 31.24 to 31.38 equinox 1950.0), while the recurrent or 'normal' maximum for bright meteors occurs at solar longitude deg 31.6, or slightly later. A mass separation of the meteors in the shower is thus indicated.

Lindblad, Bertil A.↗

NASA NTRS1993

SPOT satellite mapping of Ice Stream B

Numerous features of glaciological significance appear on two adjoining SPOT High Resolution Visible (HRV) images that cover the onset region of ice stream B. Many small-scale features, such as crevasses and drift plumes, have been previously observed in aerial photography. Subtle features, such as long flow traces that have not been mapped previously, are also clear in the satellite imagery. Newly discovered features include ladder-like runners and rungs within certain shear margins, flow traces that are parallel to ice flow, unusual crevasse patterns, and flow traces originating within shear margins. An objective of our work is to contribute to an understanding of the genesis of the features observed in satellite imagery. The genetic possibilities for flow traces, other lineations, bands of transverse crevasses, shear margins, mottles, and lumps and warps are described.

Merry, Carolyn J.↗

NASA NTRS1993

The mass balance of the ice plain of Ice Stream B and Crary Ice Rise

The region in the mouth of Ice Stream B (the ice plain) and that in the vicinity of Crary Ice Rise are experiencing large and rapid changes. Based on velocity, ice thickness, and accumulation rate data, the patterns of net mass balance in these regions were calculated. Net mass balance, or the rate of ice thickness change, was calculated as the residual of all mass fluxes into and out of subregions (or boxes). Net mass balance provides a measure of the state of health of the ice sheet and clues to the current dynamics.

Bindschadler, Robert↗

NASA NTRS1993

In search of ice-stream sticky spots

The form drag of large bedrock bumps sticking into the base of an ice stream can produce effective 'sticky spots' supporting large basal shear stress. Bedrock regions surrounded by lubricating till at the same topographic level can cause sticky spots, but tend to collect lubricating water and thus are unlikely to support a shear stress of more than a few tenths of a bar unless they contain abundant large bumps. Raised regions on the ice-air surface also can cause moderate increases in the shear stress supported on the bed beneath. Surveys of large-scale bedrock roughness, strain grids across the margins of ice-surface highs, and possibly, water-pressure measurements in regions of thin or zero till would help identify and characterize sticky spots.

Alley, Richard B.↗

NASA NTRS1993

Computational solution of the defect stream-function equation for nonequilibrium turbulent boundary layers

The derivation of the accurate, second-order, almost linear, approximate equation governing the defect stream function for nonequilibrium compressible turbulent boundary layers is reviewed. The similarity of this equation to the heat conduction equation is exploited in the development of an unconditionally stable, tridiagonal computational method which is second-order accurate in the marching direction and fourth-order accurate in the surface-normal direction. Results compare well with experimental data. Nonlinear effects are shown to be small. This two-dimensional method is simple and has been implemented on a programmable calculator.

Barnwell, Richard W.↗

NASA NTRS1992

The shedding of an anticyclonic eddy from the Alaskan Stream as observed by the Geosat altimeter

The evolution of a meander into an anticyclonic eddy which separates from the Alaskan Stream in the vicinity of the central Aleutian Islands is observed in two years of sea surface height anomalies computed from Geosat Exact Repeat Mission altimeter data. The observed region of meander growth and eddy separation agrees with that predicted by theory. Spin down times based on vorticity are much longer than those based on energies. This is consistent with an eddy's ability to maintain its integrity as it decays. Representative height, diameter, and velocity scales of the eddy are characteristic of rings spawned by other current systems. Assuming a ring structure for this eddy, the estimated ring volume represents a 21 percent transport anomaly referred to the mean annual transport into the Bering Sea.

Okkonen, Stephen R.↗

NASA NTRS1993

Discovery of Jovian dust streams and interstellar grains by the Ulysses spacecraft

Within 1 AU from Jupiter, the dust detector aboard the Ulysses spacecraft during the flyby on February 8, 1992 recorded periodic bursts of submicron dust particles with durations ranging from several hours to two days and occurring at about monthly intervals. These particles arrived at Ulysses in collimate streams radiating from close to the line-of-sight direction to Jupiter, suggesting a Jovian origin for the periodic bursts. Ulysses also detected a flux of micron-sized dust particles moving in high-velocity retrograde orbits. These grains are identified here as being of interstellar origin.

Gruen, E.↗

NASA NTRS1993

In-stream measurements of combustion during Mach 5 to 7 tests of the Hypersonic Research Engine (HRE)

Results of in-stream combustion measurements taken during Mach 5 to 7 true simulation testing of the Hypersonic Research Engine/Aerothermodynamic Integration Model (HRE/AIM) are presented. These results, the instrumentation techniques, and configuration changes to the engine installation that were required to test this model are described. In test runs at facility Mach numbers of 5 to 7, an exhaust instrumentation ring which formed an extension of the engine exhaust nozzle shroud provided diagnostic measurements at 10 circumferential locations in the HRE combustor exit plane. The measurements included static and pitot pressures using conventional conical probes, combustion gas temperatures from cooled-gas pyrometer probes, and species concentration from analysis of combustion gas samples. Results showed considerable circumferential variation, indicating that efficiency losses were due to nonuniform fuel distribution or incomplete mixing. Results using the Mach 7 facility nozzle but with Mach 6 temperature simulation, 1590 to 1670 K, showed indications of incomplete combustion. Nitric oxide measurements at the combustor exit peaked at 2000 ppmv for stoichiometric combustion at Mach 6.

Lezberg, Erwin A.↗

NASA NTRS1993

Streaming vorticity flux from oscillating walls with finite amplitude

How to describe vorticity creation from a moving wall is a long standing problem. This paper discusses relevant issues at the fundamental level. First, it is shown that the concept of 'vorticity flux due to wall acceleration' can be best understood by following fluid particles on the wall rather than observing the flow at fixed spatial points. This is of crucial importance when the time-averaged flux is to be considered. The averaged flux has to be estimated in a wall-fixed frame of reference (in which there is no flux due to wall acceleration at all); or, if an inertial frame of reference is used, the generalized Lagrangian mean (GLM) also gives the same result. Then, for some simple but typical configurations, the time-averaged vorticity flux from a harmonically oscillating wall with finite amplitude is analyzed, without appealing to small perturbation. The main conclusion is that the wall oscillation will produce an additional mean vorticity flux (a fully nonlinear streaming effect), which is partially responsible for the mechanism of vortex flow control by waves. The results provide qualitative explanation for some experimentally and/or computationally observed phenomena.

Wu, J. Z.↗

NASA NTRS1922

The Effect on Rudder Control of Slip Stream Body, and Ground Interference

This investigation was undertaken to determine the relative effects of those factors which may interfere with the rudder control of an airplane, with especial reference to the process of landing. It shows that ground interference is negligible, but that the effects of a large rounded body and of the slip stream may combine to interfere seriously with rudder control at low flying speeds and when taxiing.

Hood, H I↗

NASA NTRS1940

Aerodynamic heating and the deflection of drops by an obstacle in an air stream in relation to aircraft icing

Two topics of interest to persons attempting to apply the heat method of preventing ice formation on aircraft are considered. Surfaces moving through air at high speed are shown, both theoretically and experimentally, to be subject to important aerodynamic heating effects that will materially reduce the heat required to prevent ice. Numerical calculations of the path of water drops in an air stream around a circular cylinder are given. From these calculations, information is obtained on the percentage of the swept area cleared of drops.

Kantrowitz, Arthur↗

NASA NTRS1947

Airfoil in sinusoidal motion in a pulsating stream

The forces and moments on a two-dimensional airfoil executing harmonic motions in a pulsating stream are derived on the basis of non-stationary incompressible potential flow theory, with the inclusion of the effect of the continuous sheet of vortices shed from the trailing edge. An assumption as to the form of the wake is made with a certain degree of approximation. A comparison with previous work applicable only to the special case of a stationary airfoil is made by means of a numerical example, and the excellent agreement obtained shows that the wake approximation is quite sufficient. The results obtained are expected to be useful in considerations of forced vibrations and flutter of rotary wing aircraft.

Greenberg, J Mayo↗

NASA NTRS1953

Factors Affecting Laminar Boundary Layer Measurements in a Supersonic Stream

The observed discrepancy at supersonic speeds between theoretical and apparent experimental average flat plate friction-drag coefficients calculated from boundary layer total-pressure surveys was investigated. Effects of the total-pressure probe, heat transfer through the leading edge region, change in leading-edge radius and strength of the leading-edge wave, possible early transition to turbulent flow or “bursts of turbulence,” and the slight stream-wise pressure gradient inherent in flat plate flow were investigated for plates with very sharp leading edges. Only one of these factors, the effect of the total-pressure probe, was found to be significant. Total-pressure probes of different tip heights, when placed in laminar boundary layers developing under identical conditions, were found to yield different values of friction drag coefficient. Extrapolation of these measurements indicates that a probe of vanishing size would yield the theoretical predicted values of average flat plate friction-drag coefficients. A correlation describing the relation between the friction-drag discrepancy and the probe tip height is presented.

Blue, Robert E↗