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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 109 records · Page 6
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NASA NTRSDate not supplied

Abstract: Orion Lighting Workaround for Maintaining Crew Circadian Entrainment

Introduction. Light is the major environmental time cue of our endogenous circadian pacemaker. Suboptimal crew circadian entrainment (CCE) is common and associated with acute and chronic medical symptoms. Additionally, fatigue from suboptimal CCE promotes problematic use of sleep medications. The Orion Cabin Lighting System (OCLS) consists of monochromatic light-emitting diode (LED) lamps. However, light is a powerful suppressor of melatonin and it is a disruptor of CCE if used at incorrect times. A commercial off the shelf (COTS) dynamic lighting system (COTS-DLS) is a potential workaround for maintaining CCE.

Matthew Lindsey↗
NASA NTRS1972

Analysis and testing of high entrainment single nozzle jet pumps with variable mixing tubes

An analytical model was developed to predict the performance characteristics of axisymmetric single-nozzle jet pumps with variable area mixing tubes. The primary flow may be subsonic or supersonic. The computer program uses integral techniques to calculate the velocity profiles and the wall static pressures that result from the mixing of the supersonic primary jet and the subsonic secondary flow. An experimental program was conducted to measure mixing tube wall static pressure variations, velocity profiles, and temperature profiles in a variable area mixing tube with a supersonic primary jet. Static pressure variations were measured at four different secondary flow rates. These test results were used to evaluate the analytical model. The analytical results compared well to the experimental data. Therefore, the analysis is believed to be ready for use to relate jet pump performance characteristics to mixing tube design.

Hickman, K. E.↗
NASA NTRS1978

Effects of entrained water and strong turbulence on afterburning within solid rocket motor plumes

During the first few seconds of the space shuttle trajectory, the solid rocket boosters will be in the proximity of the launch pad. Because of the launch pad structures and the surface of the earth, the turbulent mixing experienced by the exhaust gases will be greatly increased over that for the free flight situation. In addition, a system will be present, designed to protect the lifting vehicle from launch structure vibrations, which will inject quantities of liquid water into the hot plume. The effects of these two phenomena on the temperatures, chemical composition, and flow field present in the afterburning solid rocket motor exhaust plumes of the space shuttle were studied. Results are included from both a computational model of the afterburning and supporting measurements from Titan 3 exhaust plumes taken at Kennedy Space Center with infrared scanned radiometers.

Gomberg, R. I.↗
NASA NTRS1977

Dry air entrainment into convective clouds

A systematic approach to the study of atmospheric turbulent motion is discussed in terms of weather modification. The background of cloud physics, and the mixing process are described. A zero-g study is proposed to enable the basic experimental data to be collected so that theory may be developed to generalize results for practical applications.

Telford, J. W.↗
NASA NTRS1982

Size distribution of oceanic air bubbles entrained in sea-water by wave-breaking

The size of oceanic air bubbles produced by whitecaps and wave-breaking is determined. The production of liquid aerosols at the sea surface is predicted. These liquid aerosols are at the origin of most of the particulate materials exchanged between the ocean and the atmosphere. A prototype was designed and built using an optical technique based on the principle of light scattering at an angle of ninety degrees from the incident light beam. The output voltage is a direct function of the bubble diameter. Calibration of the probe was carried out within a range of 300 microns to 1.2 mm. Bubbles produced by wave-breaking in a large air-sea interaction simulating facility. Experimental results are given in the form of size spectrum.

Resch, F.↗
NASA NTRS1983

An experimental study of entrainment and transport in the turbulent near wake of a circular cylinder

Attention is given to an experimental investigation of transport processes in the near wake of a circular cylinder, for a Reynolds number of 140,000, in which an X-array of hot wire probes mounted on a pair of whirling arms was used for flow measurement. Rotation of the arms in a uniform flow applies a wide range of relative flow angles to these X-arrays, making them inherently self-calibrating in pitch. A phase signal synchronized with the vortex-shedding process allowed a sorting of the velocity data into 16 populations, each having essentially constant phase. An ensemble average for each population yielded a sequence of pictures of the instantaneous mean flow field in which the vortices are frozen, as they would be on a photograph. The measurements also yield nonsteady mean data for velocity, intermittency, vorticity, stress, and turbulent energy production, as a function of phase. Emphasis is given in a discussion of study results to the nonsteady mean flow, which emerges as a pattern of centers and saddles in a frame of reference that moves with the eddies. The kinematics of the vortex formation process are described in terms of the formation and evolution of saddle points between vortices in the first few diameters of the near wake.

Cantwell, B.↗
NASA NTRS1983

Cumulus clouds - Numerical models, observations and entrainment

The first computer simulation of the organization phase of a buoyant atmospheric thermal is described. Although crude, it showed the spontaneous development of a rounded tight-gradient 'cap' and internal vortical circulation. The complexities involved in these 'field of motion' models in part motivated the development of entity models, based upon laboratory thermals. These one-dimensional models and their uses with observations are briefly described as well as their limitations. Finally, an application of Schlesinger's three-dimensional model to a GATE cumulus situation clarifies many apparently conflicting observations and postulates, thereby raising further challenging questions to be addressed jointly by the more sophisticated measuring and modeling tools available in the 1980's.

Simpson, J.↗
NASA NTRS1985

The Role of Entrained Surface Oxides in RS-PM Aluminum Alloys on Resultant Structures and Properties

The RS-PM aluminum alloys which show less than anticipated toughness properties were studied. After eliminating negative variables such as sodium and potassium in lithium containing alloys, hydrogen in all Al alloys, and trapped impurities from the atomization processing the data pointed to fine oxides, as the primary cause of poor toughness properties. The oxide content of aluminum powders increases with: decreasing powder size, deviations from spherical powder shapes, exposure to moist atmospheres either during atomization or in subsequent powder handling, and alloy compositions which contain significant amounts of lithium, magnesium, cerium, and other reactive elements.

Grant, N. J.↗
NASA NTRS1986

Entrainment, transport and concentration of meteorites in polar ice sheets

Glaciers and ice sheets act as slow-moving conveyancing systems for material added to both their upper and lower surfaces. Because the transit time for most materials is extremely long the ice acts as a major global storage facility. The effects of horizontal and vertical motions on the flow patterns of Antarctic ice sheets are summarized. The determination of the source areas of meteorites and their transport paths is a problem of central importance since it relates not only directly to concentration mechanisms but also to the wider issues in glaciology and meteorites. The ice and snow into which a meteorite falls, and which moves with it to the concentration area, encodes information about the infall area. The principle environmental conditions being former elevation, temperature (also related to elevation), and age of the ice. This encoded information could be used to identify the infall area.

Drewry, D. J.↗
NASA NTRS1988

Efficiency of shear induced entrainment in convectively mixed layers

Lidar data of mixed layer height are used to compare the model of process partitioning to that of Eulerian partitioning. It is found that the Eulerian partitioning model more closely follows the data and that the process partitioning model underpredicts the mixed layer depth. The results suggest that shear production and consumption of turbulent kinetic energy at the mixed layer top are local processes.

Boers, Reinout↗
NASA NTRS1991

Cloud albedo control by cloud-top entrainment

Marine stratus and stratocumulus clouds exert a considerable influence on the earth's heat budget, mainly due to their high albedos relative to the ocean surface. It is therefore important to understand the processes that control the radiative properties of these extensive cloud systems, particularly during daylight hours. Aircraft measurements of a stratocumulus cloud deck taken around local noon during the 1987 field phase of the First International Satellite Cloud Climatology Project Regional Experiment are the topic of this paper. A mixing line analysis of data from a series of flight tracks across a strong gradient in cloud albedo provides evidence that variations in the water vapor content of the air above the marine inversion can be responsible for the albedo change. The implications of this unexpected result for climate modeling are discussed.

Hanson, Howard P.↗