Spreading Characteristics of a Jet Expanding from Choked Nozzles at Mach 1.91
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Rousso, Morris D↗
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Evaporation and spreading of isooctane sprays in high velocity air streams
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Bahr, Donald W↗
Contributions to the theory of the spreading of a free jet issuing from a nozzle
For the flow field of a free jet leaving a nozzle of circular cross section in a medium with a straight uniform flow field, approximate formulas are presented for the calculation of the velocity distribution and the dimensions of the core region. The agreement with measured results is satisfactory.
FLOW, TURBULENT - JETS↗
Self-Locking Spreading Pliers
Tool is modified pair of commercial self-locking pliers. Jaws of modified pliers face outward instead of inward. Applies force opposite to that of conventional pliers. Used to force surfaces apart and hold them at fixed separation or to grip a tube from inside.
Bickler, Donald B.↗
Multipath noise reduction spread spectrum signals
The concepts of early-prompt delay tracking, multipath correction of early-prompt delay tracking from correlation shape, and carrier phase multipath correction are addressed. In early-prompt delay tracking, since multipath is always delayed with respect to the direct signals, the system derives phase and pseudorange observables from earlier correlation lags. In multipath correction of early-prompt delay tracking from correlation shape, the system looks for relative variations of amplitude across the code correlation function that do not match the predicted multipath-free code cross-correlation shape. The system then uses deviations from the multipath-free shape to infer the magnitude of multipath, and to generate corrections pseudorange observables. In carrier phase multipath correction, the system looks for variations of phase among plural early and prompt lags. The system uses the measured phase variations, along with the general principle that the multipath errors are larger for later lags, to infer the presence of multipath, and to generate corrections for carrier-phase observables.
Meehan, Thomas K.↗
Axis switching and spreading of an asymmetric jet: Role of vorticity dynamics
The effects of vortex generators and periodic excitation on vorticity dynamics and the phenomenon of axis switching in a free asymmetric jet are studied experimentally. Most of the data reported are for a 3:1 rectangular jet at a Reynolds number of 450,000 and a Mach number of 0.31. The vortex generators are in the form of 'delta tabs', triangular shaped protrusions into the flow, placed at the nozzle exit. With suitable placement of the tabs, axis switching could be either stopped or augmented. Two mechanisms are identified governing the phenomenon. One, as described by previous researchers and referred to here as the omega(sub theta)-induced dynamics, is due to difference in induced velocities for different segments of a rolled up azimuthal vortical structure. The other, omega(sub x)-induced dynamics, is due to the induced velocities of streamwise vortex pairs in the flow. Both dynamics can be active in a natural asymmetric jet; the tendency for axis switching caused by the omega(sub theta)-induced dynamics may be, depending on the streamwise vorticity distribution, either resisted or enhanced by the omega(sub x)-induced dynamics. While this simple framework qualitatively explains the various observations made on axis switching, mechanisms actually in play may be much more complex. The two dynamics are not independent as the flow field is replete with both azimuthal and streamwise vortical structures which continually interact. Phase averaged flow field data for a periodically forced case, over a volume of the flow field, are presented and discussed in an effort to gain insight into the dynamics of these vortical structures.
Zaman, K. B. M. Q.↗
Spread of denitrification from 1987 Antarctic and 1988-1989 Arctic stratospheric vortices
Vertical profiles of N2O and NO(y) taken by the ER-2 outside the vortex are used to construct average vertical profiles of F(NO(y)) = NO(y)/(A-N2O), where A is the tropospheric content of N2O three years prior to the measurements. The southern hemisphere had less nitrous oxide in the range 400 less than Theta less than 470 K, by up to 25% relative to the northern hemisphere. F(NO(y)) is the ratio of NOy produced to N2O lost in a stratospheric air mass since entry from the troposphere. The profiles of F(NO(y)) have the following characteristics: (1) Relative to 1991-1992, a year without denitrification inside or outside the vortex, the northern hemisphere in 1988-1989 showed denitrification outside the vortex ranging up to 25% and averaging 17% above Theta = 425 K. (2) Relative to the northern hemisphere in 1991-1992, the southern hemisphere in 1987 showed denitrification outside the vortex ranging up to 32% and averaging 20% above Theta = 400 K. (3) Below Theta = 400 K the southern hemisphere showed enhancements of F(NO(y)) relative to the northern hemisphere in 1991-1992 ranging up to 200% at Theta = 375 K, outside the vortex. Corresponding profiles of residual water, R(H2O) = H2O - 2(1.6 - CH4), are considered and shown to be consistent with those of F(NO(y)) in the sense that they show deficits outside the Antarctic vortex, which was both dehydrated and denitrified, but not outside the 1988-1989 Arctic vortex, which was denitrified but not dehydrated. R(H2O) is the water content of stratospheric air with the contribution from methane oxidation subtracted. Comparison of F(NO(y)) and R(H2O) below 400 K outside the Antarctic vortex leads to the suggetion that dehydration in the Antarctic vortex occurs by the sedimentation of ice crystals large enough to fall out of the stratosphere, whereas denitrification occurs mainly on mixed nitric acid-water crystals which evaporate below the base of the vortex at Theta = 400 K but above the tropopause.
Tuck, A. F.↗
The Spreading of Variable-Viscosity Axisymmetric Radial Gravity Currents: Applications to the Emplacement of Venusian 'Pancake' Domes
The Magellan images of Venus have revealed a number of intriguing volcanic features, including the steep-sided or 'pancake' domes. These volcanic domes or flows have morphologies that suggest formation by a single continuous emplacement of lava with a higher viscosity than that of the surrounding basaltic plains. Numerous investigators have suggested that such high viscosity is due to high silica content, leading to the conclusion that the domes are evidence of evolved magmatic products on Venus. However, viscosity depends on crystallinity as well as on silica content: high viscosity could therefore also be due to a cooler (and therefore higher crystal content) lava. Models of dome emplacement which include both cooling and composition factors are thus necessary in order to determine the ranges of crystallinity and silica content which might lead to the observed gross dome morphologies. Accordingly, in this study domes are modelled as radial viscous gravity currents with an assumed cooling-induced viscosity increase to include both effects. Analytical and numerical results indicate that pancake dome formation is feasible with compositions ranging from basaltic to rhyolitic. Therefore, observations of gross dome morphology alone are insufficient for determining composition and the domes do not necessarily represent strong evidence for evolved magmatism on Venus.
Sakimoto, S. E. H.↗
Direct Numerical Simulation of Wetting and Spreading Behavior on Heterogeneous and Roughened Substrates
A method of calculation is presented that allows the simulation of the time-dependent three-dimensional motion of thin liquid layers on solid substrates for systems with finite equilibrium contact angles. The contact angle is a prescribed function of position on the substrate. Similar mathematical models are constructed for substrates with a pattern of roughness. Evolution equations are given, using the lubrication approximation, that include viscous, capillary and disjoining forces. Motion to and from dry substrate regions is made possible by use of a thin energetically-stable wetting layer. We simulate motion on heterogeneous substrates with periodic arrays of high contact-angle patches. Two different problems are treated for heterogenous substrates. The first is spontaneous motion driven only by wetting forces. If the contact-angle difference is sufficiently high, the droplet can find several different stable positions, depending on the previous history of the motion. A second simulation treats a forced cyclical motion. Energy dissipation per cycle for a heterogeneous substrate is found to be larger than for a uniform substrate with the same total energy. The Landau-Levich solution for plate removal from a liquid bath is extended to account for a pattern of roughness on the plate.
Schwartz, Leonard W.↗
C-O-H ratios of silicate melt inclusions in basalts from the Galapagos Spreading Center near 95 degrees W: a laser decrepitation mass spectrometry study
Volatile ratios (primarily of H2O and CO2) in individual silicate melt (glass) inclusions in minerals have been analyzed using laser volatilization and mass spectrometry. A Nd-glass laser was used to produce 50-micrometer diameter pits in silicate melt inclusions. Released volatiles were analyzed directly with a computer-controlled quadrupole mass spectrometer. The detection limits for CO2 and H2O were on the order of 3 x 10(-14) and 3 x 10(-13) moles, respectively. The reproducibility for CO2/H2O was better than +/- 9%. The total range of volatile ratios from vitreous silicate glass inclusions contained in a suite of Galapagos lavas were: 0.018 to 1.193 for CO2/H2O; 0.002 to 0.758 for CO/H2O; 0 to 0.454 for CH4/H2O; and 0 to 0.432 for Ar/H2O. The mean CO2/H2O from the propagating rift (0.245 +/- 0.068) silicate glass inclusions is significantly lower than that of the actively failing rift (0.641 +/- 0.241); this difference probably reflects different degrees of degassing during magmatic histories for the two regions. Relatively undifferentiated failing rift magmas must have relatively short crustal residence times prior to eruption and, therefore, have not undergone significant degassing of CO2, as would appear to be the case for the more highly fractionated propagating rift magmas. The laser-mass spectrometric system described herein has the ability to act as a point-source probing device that can differentiate between the various volatile sites in minerals and rocks (as well as synthetic materials) on a micrometer scale.
NASA Discipline Exobiology↗
Understanding Material Property Impacts on Co-Current Flame Spread: Improving Understanding Crucial for Fire Safety
The prospect of long-term manned space flight brings fresh urgency to the development of an integrated and fundamental approach to the study of material flammability. Currently, NASA uses two tests, the upward flame propagation test and heat and visible smoke release rate test, to assess the flammability properties of materials to be used in space under microgravity conditions. The upward flame propagation test can be considered in the context of the 2-D analysis of Emmons. This solution incorporates material properties by a "mass transfer number", B in the boundary conditions.
Ruff, Gary↗
Spreading the Word on Safety
Beginning with the Apollo Program in the early 1960s, the NASA White Sands Test Facility (WSTF) has supported every U.S. human exploration space flight program to date. Located in Las Cruces, New Mexico, WSTF is part of Johnson Space Center. The facility's primary mission is to provide the expertise and infrastructure to test and evaluate spacecraft materials, components, and rocket propulsion systems to enable the safe human exploration and utilization of space. WSTF stores, tests, and disposes of Space Shuttle and International Space Station propellants. Since aerospace fluids can have harmful reactions with the construction materials of the systems containing them, a major component of WSTF's work is the study of propellants and hazardous materials. WSTF has a wide variety of resources to draw upon in assessing the fire, explosion, compatibility, and safety hazards of these fluids, which include hydrogen, oxygen, hydrazine fuels, and nitrogen tetroxide. In addition to developing new test methods, WSTF has created technical manuals and training courses for the safe use of aerospace fluids.
Source record↗
Experimental Investigation of Spreading Characteristics of Choked Jets Expanding into Quiescent Air
Investigations have been conducted to determine by means of total-pressure surveys the boundaries of single and twin jets discharging through convergent nozzles into quiescent air. The jet boundaries for the region from the nozzle outlets to a station 6 nozzle diameters downstream are presented for nozzle pressure ratios ranging from 2.5 t o 16.0 and for twin-Jet nozzle center-line spacings ranging from 1.42 to 2.50 nozzle diameters. The effects of these parameters on the interaction of twin Jets are discussed. In order to ascertain the utility of the results for other than the test conditions, the effects of jet temperature, Reynolds number, and humidity on the pressure boundaries have been briefly investigated. The result indicate that for a jet of 2.6 the pressure boundaries are slightly smaller than those of corresponding unheated jets and that the effects of Reynolds number and humidity are negligible.
Rousso, Morris D.↗
Spread and SpreadRecorder An Architecture for Data Distribution
The Space Acceleration Measurement System (SAMS) project at the NASA Glenn Research Center (GRC) has been measuring the microgravity environment of the space shuttle, the International Space Station, MIR, sounding rockets, drop towers, and aircraft since 1991. The Principle Investigator Microgravity Services (PIMS) project at NASA GRC has been collecting, analyzing, reducing, and disseminating over 3 terabytes of collected SAMS and other microgravity sensor data to scientists so they can understand the disturbances that affect their microgravity science experiments. The years of experience with space flight data generation, telemetry, operations, analysis, and distribution give the SAMS/ PIMS team a unique perspective on space data systems. In 2005, the SAMS/PIMS team was asked to look into generalizing their data system and combining it with the nascent medical instrumentation data systems being proposed for ISS and beyond, specifically the Medical Computer Interface Adapter (MCIA) project. The SpreadRecorder software is a prototype system developed by SAMS/PIMS to explore ways of meeting the needs of both the medical and microgravity measurement communities. It is hoped that the system is general enough to be used for many other purposes.
Wright, Ted↗
Forecasting equatorial spread-F using a global assimilative ionospheric model
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GAIM ionospheric measurements↗
Forecasting equatorial spread-F using a global assimilative ionospheric model
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ionospheric modeling data assimilation↗
Gravity and magma induces spreading of Mount Etna volcano revealed by satellite radar interferometry
Mount Etna underwent a cycle of eruptive activity over the past ten years. Here we compute ground displacement maps and deformation time series from more than 400 radar interferograms to reveal Mount Etna's average and time varying surface deformation from 1992 to 2001.
Geodesy gravity volcanology instruments and techni↗
The NASA Tournament Laboratory (NTL): Improving Data Access at PDS while Spreading Joy and Engaging Students through 16 Micro-Contests
NASA PDS hosts terabytes of valuable data from hundreds of data sources and spans decades of research. Data is stored on flat-file systems regulated through careful meta dictionaries. PDS's data is available to the public through its website which supports data searches through drill-down navigation. While the system returns data quickly, result sets in response to identical input differ depending on the drill-down path a user follows. To correct this Issue, to allow custom searching, and to improve general accessibility, PDS sought to create a new data structure and API, and to use them to build applications that are a joy to use and showcase the value of the data to students, teachers and citizens. PDS engaged TopCoder and Harvard Business School through the NTL to pursue these objectives in a pilot effort. Scope was limited to Small Bodies Node data. NTL analyzed data, proposed a solution, and implemented it through a series of micro-contests. Contest focused on different segments of the problem; conceptualization, architectural design, implementation, testing, etc. To demonstrate the utility of the completed solution, NTL developed web-based and mobile applications that can compare targets, regardless of mission. To further explore the potential of the solution NTL hosted "Mash-up" challenges that integrated the API with other publically available assets, to produce consumer and teaching applications, including an Augmented Reality iPad tool. Two contests were also posted to middle and high school students via the NoNameSite.com platform, and as a result of these contests, PDS/SBN has initiated a Facebook program. These contests defined and implemented a data warehouse with the necessary migration tools to transform legacy data, produced a public web interface for the new search, developed a public API, and produced four mobile applications that we expect to appeal to users both within and, without the academic community.
LaMora, Andy↗