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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 127 records · Page 7

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NASA NTRS2001

Canaveral National Seashore Water Quality and Aquatic Resource Inventory

Mosquito Lagoon is a shallow, bar-built estuary located on the east central Florida Coast, primarily within the KSC boundary. The lagoon and watershed cover approximately 327 sq km (79422 acres) .The Lagoon occupies 159 sq km (37853 acres). Water depths average approximately 1m. The lagoon volume is approximately 1.6 x 10(exp 8)cu m. Water quality in Mosquito Lagoon is good. Salinity data typically range between 20 ppt and 35 ppt. The lowest value recorded was 4.5 ppt and the highest value was 37 ppt. Water temperatures fluctuate 2 - 3 C over a 24 h period. Cold front passage can rapidly alter water temperatures by 5 - 10 C or more in a short period of time. The highest temperature was 33.4 C and the lowest temperature was 8.8 C after a winter storm. Dissolved oxygen concentrations ranged from a low of 0.4 mg/l to a high of 15.3 mg/l. Extended periods of measurements below the Florida Department of Environmental Protection criteria of 4.0 mg/l were observed in fall and spring months suggesting high system respiration and oxygen demand. Metals such as antimony, arsenic, molybdenum and mercury were report as below detection limits for all samples. Cadmium, copper, chromium, silver, and zinc were found to be periodically above the Florida Department of Environmental Protection criteria for Class II and Class III surface waters.

Hall, C. R.↗

NASA NTRS1975

Effects of transducer flushness on fluctuating surface pressure measurements

The installation flushness of pressure transducers has been found to strongly influence the quality of fluctuating surface pressure data in supersonic-attached turbulent boundary-layer flow. A systematic investigation of the effects of flushness on surface pressure fluctuations beneath a 4-in.-thick boundary layer was conducted in a supersonic wind tunnel at Mach numbers of 1.68, 2.0, and 2.5. Flushness effects on transducer signal amplitude, power spectral density, coherence, and narrowband convection velocity was evaluated. Results show that a very slightly protruding transducer produces adverse effects on the desired pressure fluctuation measurements, whereas a submerged transducer produces small effects. Indications are that a more viable method for enhancing the uniformity and spatial correlation of fluctuating surface pressure data can be achieved by deliberately submerging transducers beneath a surface orifice about 0.010 in. deep.

Hanly, R. D.↗

NASA NTRS1994

A scanning defect mapping system for semiconductor characterization

We have developed an optical scanning system that generates maps of the spatial distributions of defects in single and polycrystalline silicon wafers. This instrument, called Scanning Defect Mapping System, utilizes differences in the scattering characteristics of dislocation etch pits and grain boundaries from a defect-etched sample to identify and count them. This system simultaneously operates in the dislocation mode and the grain boundary (GB) mode. In the 'dislocation mode,' the optical scattering from the etch pits is used to statistically count dislocations, while ignoring the GB's. Likewise, in the 'grain boundary mode' the system only recognizes the local scattering from the GB's to generate grain boundary distributions. The information generated by this instrument is valuable for material quality control, identifying mechanisms of defect generation and the nature of thermal stresses during the crystal growth, and the solar cell process design.

Sopori, Bushnan L.↗

NASA NTRSDate not supplied

The National Airborne Sounder Testbed-Interferometer (Nast-I): Existing Technology for New Science and Application

The National Airborne Sounder Testbed-Interferometer (NAST-I) is an existing ultraspectral infrared sounder flown on high-altitude aircraft that provides high spectral and spatial resolution measurements which continue to advance understanding of science critical for weather, climate, chemistry, and radiation applications. NAST-I provides high-spatial linear resolution equal to 13% of the aircraft altitude at nadir (i.e., 2.6 km IFOV on the ground from an aircraft altitude of 20 km), and high-spectral resolution (0.25 cm-1) measurements within the spectral region of 645–2700 cm-1. The NAST-I suborbital system serves as a spaceborne instrument simulator and pathfinder for future satellite capabilities and airborne science experiments. Present herein are some groundbreaking capabilities of NAST-I measurements and corresponding geophysical retrievals and their potential benefits toward improved atmospheric state and composition characterizations needed for air quality, wildfire, and other science applications and, in particular, for enhanced Planetary Boundary Layer (PBL) characterization and understanding.

Remote sensor↗

NASA NTRS1979

Nonreflective boundary control of a vibrating string

One of the important applications in the developing Large Space Systems Technology will be the electrostatically controlled membrane mirror antenna. A high level of surface quality is achievable using electrostatically tensioned membranes in which surface accuracy is obtained through active control. Electrostatic actuators behind the membrane surface would provide a means of obtaining the prescribed surface shape and also be utilized to suppress the structural vibrations in the system. The surface quality, in this case, would be limited by the size, force field shape, and the number of the electrostatic actuators. An additional control capability is to introduce boundary control at the membrane perimeter. Using this additional control mechanism, structural vibrations can be absorbed at the boundary without being reflected back into the interior regions of the membrane antenna. In this paper, boundary control of a vibrating string is studied. For this system, a nonreflective boundary control is developed in which waves reaching the boundary are absorbed by the appropriate control movement of the boundary. The control is closed-loop and utilizes a single measurement close to the boundary. The closed-loop control is a delay of the measurement. The delay is determined by the velocity of wave propagation in the string and the location of the sensor.

Caglayan, A. K.↗

NASA NTRS1959

Experimental Verification of Boundary-Layer Corrections in Hypersonic Nozzles

The problem of accurately predicting boundary-layer growth for supersonic nozzle design assumes increased importance as the design Mach Number of the nozzles is pushed into the hypersonic regime. Several methods of calculating this growth have been advanced which vary in ease of computation and accuracy of results. Results of the calibrations performed on two hypersonic helium nozzles recently put into operation in the 11-in. Hypersonic Tunnel Section at the NASA Langley Research Center indicate that the method employed for boundary-layer calculations in these nozzles is adequate. The flow in the test region of both nozzles has been found to be of good quality and the Mach Numbers obtained agree very satisfactorily with the desired design Mach Number.

Boundary Layer Equations↗

NASA NTRS1995

A structured multi-block solution-adaptive mesh algorithm with mesh quality assessment

The dynamic solution adaptive grid algorithm, DSAGA3D, is extended to automatically adapt 2-D structured multi-block grids, including adaption of the block boundaries. The extension is general, requiring only input data concerning block structure, connectivity, and boundary conditions. Imbedded grid singular points are permitted, but must be prevented from moving in space. Solutions for workshop cases 1 and 2 are obtained on multi-block grids and illustrate both increased resolution of and alignment with the solution. A mesh quality assessment criteria is proposed to determine how well a given mesh resolves and aligns with the solution obtained upon it. The criteria is used to evaluate the grid quality for solutions of workshop case 6 obtained on both static and dynamically adapted grids. The results indicate that this criteria shows promise as a means of evaluating resolution.

Ingram, Clint L.↗

NASA NTRS1983

Importance of inlet boundary conditions for numerical simulation of combustor flows

Fluid dynamic computer codes for the mathematical simulation of problems in gas turbine engine combustion systems are required as design and diagnostic tools. To eventually achieve a performance standard with these codes of more than qualitative accuracy it is desirable to use benchmark experiments for validation studies. Typical of the fluid dynamic computer codes being developed for combustor simulations is the TEACH (Teaching Elliptic Axisymmetric Characteristics Heuristically) solution procedure. It is difficult to find suitable experiments which satisfy the present definition of benchmark quality. For the majority of the available experiments there is a lack of information concerning the boundary conditions. A standard TEACH-type numerical technique is applied to a number of test-case experiments. It is found that numerical simulations of gas turbine combustor-relevant flows can be sensitive to the plane at which the calculations start and the spatial distributions of inlet quantities for swirling flows.

Sturgess, G. J.↗

NASA NTRS2016

Formation of Oxides in the Interior of Friction Stir Welds

In friction stir welding (FSWing) the actual solid state joining takes place between the faying surfaces which form the weld seam. Thus the seam trace is often investigated for clues when the strength of the weld is reduced. Aluminum and its alloys are known to form a native, protective oxide on the surface. If these native surface oxides are not sufficiently broken up during the FSW process, they are reported to remain in the FSW interior and weaken the bond strength. This type of weld defect has been referred to as a lazy "S", lazy "Z", joint line defect, kissing bond, or residual oxide defect. Usually these defects are mitigated by modification of the process parameters, such as increased tool rotation rate, which causes a finer breakup of the native oxide particles. This study proposes that there may be an alternative mechanism for formation of oxides found within the weld nugget. As the oxidation rate increases at elevated temperatures above 400ºC, it may be possible for enhanced oxidation to occur on the interior surfaces during the FSW process from entrained air entering the seam gap. Normally, FSWs of aluminum alloys are made without a purge gas and it is unknown how process parameters and initial fit up could affect a potential air path into the interior during the processing. In addition, variations in FSW parameters, such as the tool rotation, are known to have a strong influence on the FSW temperature which may affect the oxidation rate if internal surfaces are exposed to entrained air. A series of FSWs were made in 3 different thickness panels of AA2219 (0.95, 1.27 and 1.56 cm) at 2 different weld pitches. As the thickness of the panels increased, there was an increased tendency for a gap to form in advance of the weld tool. If sufficient air is able to enter the workpiece gap prior to consolidation, the weld temperature can increase the oxidation rate on the interior surfaces. These oxidation rates would also be accelerated in areas of localized liquation. Metallographs from the weld panels showed indications of liquation at the grain boundaries. In FSWs of thicker panels, these regions of liquation were found to be heavily oxidized. The quality of the FSWs was evaluated from tensile testing at room temperature. As the panel thickness increased, a slight decrease in tensile strength was observed which was attributed to the presence of oxides. No oxide formation was observed in the thinner workpieces, although there were indications of localized liquation at the grain boundaries. Results from this study will assist in a better understand of the mechanisms of oxide formation in FSW interiors and provide methodology for minimizing their occurrence.

Schneider, Judy↗

NASA NTRS2021

Toward a Global Planetary Boundary Layer Observing System: The NASA PBL Incubation Study Team Report

A global Planetary Boundary Layer (PBL) observing system is urgently needed to address fundamental PBL science questions and societal applications related to weather, climate and air quality. This PBL observing system should optimally combine new space-based observations of the PBL thermodynamic structure with complementary surface-based and suborbital assets, while taking advantage of, and helping improve, modeling and data assimilation systems.

Planetary boundary layer↗

NASA NTRS1981

Investigations of medium wavelength magnetic anomalies in the Eastern Pacific using Magsat data

Processing continued on the data set covering the first three months of the mission. Orbits were selected over a specified range of longitude and latitude and those orbits falling within the geographical boundaries were stored on a disk and a listing made. To verify the quality of the data, plots were made showing altitude vs latitude, anomalous field vs latitude, and corrected anomalous field vs latitude. Results of the plotting showed that: (1) data from the first day of the mission are not usable because they are too noisy; (2) some orbits contain spikes, no doubt a processing error on the tape; (3) some orbits contain a 20 deg region in latitude, offset roughly 30 nT from the rest of the anomalous field profiles; and (4) the correlation between the adjacent orbits is poor. Even the new ring current coefficients provided with a later, corrected set of data tapes did not not yield the desired correlations.

Harrison, C. G. A.↗

NASA NTRS1983

Aerothermal modeling program, phase 1

Aerothermal submodels used in analytical combustor models are analyzed. The models described include turbulence and scalar transport, gaseous full combustion, spray evaporation/combustion, soot formation and oxidation, and radiation. The computational scheme is discussed in relation to boundary conditions and convergence criteria. Also presented is the data base for benchmark quality test cases and an analysis of simple flows.

Srinivasan, R.↗

NASA NTRS1984

Fluvial drainage systems: Margaritifer Sinus and Agyre (NC, NE) quadrangles, Mars

Fluvial drainage systems, delineated by mapping on stereo pairs of Viking Orbiter images, have developed in various-sized basins in the Margaritifer Sinus (MC-19) and Agyre (MC-26) Quadrangles, Mars. The Ladon Valles system is the largest, draining into and through two multi-ringed impact basins. Smaller fluvial basins to the southeast of the Ladon structural basin appear to have internal drainage. An intermediate-scale fluvial basin containing Himera Vallis extends along a north-south axis at 22 W and opens northward toward outflow channels south of Margaritifer Chaos. Stereo-pair mapping was extended furhter to the east, in MC-19 Ne, Se, and MC-26 NE, to investigate sources of outflow to the Ares Vallis system. The direction of flow in the channel at the northeast quadrant of the Ladon Basin is unresolved at present because of the poor quality of images available to form stereo pairs. However, an easterly drainage basin boundary running north-south along longitude 9 W, and extending westward at latitude 32-35 S, encloses a series of longitudinal drainage systems. Both the Parana Valles-Loire Vallis system and the Samara Valles system appear to drain in a northwesterly direction. The Samara flows to the Himera drainage basin, and the Parana-Loire to the northeast Ladon channel area.

Boothroyd, J. C.↗

NASA NTRS1982

NASA participation in the 1980 PEPE/NEROS project: Data archive

Eight experimental air quality measurement systems were investigated during July and August 1980 as part of the EPA PEPE/NEROS fiel measurement program. Data from those efforts have been entered into an archive that may be accessed by other researchers. The data sets consists of airborne measurements of regional mixed layer heights and aerosol and ozone distributions as well as point measurements of meteorological parameters and ozone obtained during diurnal transitions in the planetary boundary layer. This report gives a discussion of each measurement system, a preliminary assessment of data quality, a description of the archive format for each data set, and a summary of several proposed scientific studies which will utilize these data.

Brewer, D. A.↗

NASA NTRSDate not supplied

Importance of Radiative Transfer Models in Atmospheric Remote Sensing

Radiative transfer models (RTMs) play a significant role in the development of satellite instruments for remote sensing applications. These models simulate electromagnetic radiation's propagation through the atmosphere, providing valuable insights into atmosphere-radiation interactions. RTMs facilitate the optimization of satellite instrument designs, ensuring their ability to measure targeted atmospheric and surface properties accurately. Moreover, they aid in simulating instrument’s measurements under various atmospheric conditions, enabling calibration and validation processes to enhance data quality and reliability. RTMs are extensively used in the Observing System Simulation Experiments (OSSE), to generate synthetic observations. By incorporating RTMs into OSSE, we can assess the potential impact of future satellite missions, sensor configurations, and data assimilation techniques. This approach allows for the optimization of satellite instruments and constellations and the evaluation of their influence on weather forecasting, climate monitoring, and other Earth science applications. Another crucial application area of RT models is data assimilation, where they play a fundamental role in combining satellite observations with numerical models to improve atmospheric and environmental predictions. RTMs provide the link between observed radiances and atmospheric parameters, enhancing the accuracy of numerical models and generating more reliable forecasts for weather events, air quality assessments, and climate projections. Moreover, adapting RT models to capture the intricate radiation interactions within the Planetary Boundary Layer will significantly contribute to improving weather forecasting and climate change projections. Current community radiative transfer (RT) models are primarily developed and optimized for operational data assimilation of satellite observations. These models excel at assimilating satellite data into numerical weather prediction models to improve forecast accuracy. However, their focus on data assimilation limits their suitability for other important applications, such as satellite instrument development, OSSE, and Planetary Boundary Layer (PBL) studies. Moreover, for PBL studies, RT models need to be adapted to capture the intricate radiation interactions within this crucial atmospheric layer. Developing RT models that can represent the PBL's unique characteristics, such as surface interactions, will contribute significantly to understanding and predicting weather phenomena, air quality, and climate dynamics. This abstract provides a comprehensive overview of the current status of RT models and highlights their limitations concerning satellite instrument development, OSSE, and PBL studies. Addressing these shortcomings requires concerted efforts to enhance RT models' capabilities and expand their applications beyond data assimilation. By investing in research and development to improve these

Isaac Moradi↗

NASA NTRS2002

Computing Aerodynamic Performance of a 2D Iced Airfoil: Blocking Topology and Grid Generation

The ice accrued on airfoils can have enormously complicated shapes with multiple protruded horns and feathers. In this paper, several blocking topologies are proposed and evaluated on their ability to produce high-quality structured multi-block grid systems. A transition layer grid is introduced to ensure that jaggedness on the ice-surface geometry do not to propagate into the domain. This is important for grid-generation methods based on hyperbolic PDEs (Partial Differential Equations) and algebraic transfinite interpolation. A 'thick' wrap-around grid is introduced to ensure that grid lines clustered next to solid walls do not propagate as streaks of tightly packed grid lines into the interior of the domain along block boundaries. For ice shapes that are not too complicated, a method is presented for generating high-quality single-block grids. To demonstrate the usefulness of the methods developed, grids and CFD solutions were generated for two iced airfoils: the NLF0414 airfoil with and without the 623-ice shape and the B575/767 airfoil with and without the 145m-ice shape. To validate the computations, the computed lift coefficients as a function of angle of attack were compared with available experimental data. The ice shapes and the blocking topologies were prepared by NASA Glenn's SmaggIce software. The grid systems were generated by using a four-boundary method based on Hermite interpolation with controls on clustering, orthogonality next to walls, and C continuity across block boundaries. The flow was modeled by the ensemble-averaged compressible Navier-Stokes equations, closed by the shear-stress transport turbulence model in which the integration is to the wall. All solutions were generated by using the NPARC WIND code.

Chi, X.↗

NASA NTRS1981

Fermi-Compton scattering due to magnetopause surface fluctuations in Jupiter's magnetospheric cavity

The effects of boundary surface fluctuations on a spectrum of electromagnetic radiation trapped in a high Q (quality) cavity are considered. Undulating walls introduce small frequency shifts at reflection to the radiation, and it is argued that the process is entirely analogous to both Fermi (particle) acceleration and inverse Compton scattering. A Fokker-Planck formalism is pursued; it yields a diffusion equation in frequency for which the Green's function and steady-state solutions are found. Applying this analysis to the Jovian continuum radiation discovered by Voyager spacecraft, it is suggested that characteristic diffusion times are greater than 1 year, and that in order to account for the steep frequency spectra observed, an unidentified loss mechanism must operate in the cavity with a decay time constant approximately equal to the characteristic diffusion time divided by 28. A radiator-reactor model of the cavity is investigated to provide an estimate for the intrinsic luminosity of the low frequency (approximately 100 Hz) continuum source whose power is approximately 7 x 10 to the 6th W.

Barbosa, D. D.↗

NASA NTRS1982

Laminar flow control, 1976 - 1982: A selected annotated bibliography

Laminar Flow Control technology development has undergone tremendous progress in recent years as focused research efforts in materials, aerodynamics, systems, and structures have begun to pay off. A virtual explosion in the number of research papers published on this subject has occurred since interest was first stimulated by the 1976 introduction of NASA's Aircraft Energy Efficiency Laminar Flow Control Program. The purpose of this selected bibliography is to list available, unclassified laminar flow (both controlled and natural) research completed from about 1975 to mid 1982. Some earlier pertinent reports are included but listed separately in the Appendix. Reports listed herein emphasize aerodynamics and systems studies, but some structures work is also summarized. Aerodynamic work is mainly limited to the subsonic and transonic sped regimes. Because wind-tunnel flow qualities, such as free stream disturbance level, play such an important role in boundary-layer transition, much recent research has been done in this area and it is also included.

Tuttle, M. H.↗