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At least 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Thermophysical Properties Measurement of High-Temperature Liquids Under Microgravity Conditions in Controlled Atmospheric Conditions

Microgravity conditions have advantages of measurement of surface tension and viscosity of metallic liquids by the oscillating drop method with an electromagnetic levitation (EML) device. Thus, we are preparing the experiments of thermophysical properties measurements using the Materials-Science Laboratories ElectroMagnetic-Levitator (MSL-EML) facilities in the international Space station (ISS). Recently, it has been identified that dependence of surface tension on oxygen partial pressure (Po2) must be considered for industrial application of surface tension values. Effect of Po2 on surface tension would apparently change viscosity from the damping oscillation model. Therefore, surface tension and viscosity must be measured simultaneously in the same atmospheric conditions. Moreover, effect of the electromagnetic force (EMF) on the surface oscillations must be clarified to obtain the ideal surface oscillation because the EMF works as the external force on the oscillating liquid droplets, so extensive EMF makes apparently the viscosity values large. In our group, using the parabolic flight levitation experimental facilities (PFLEX) the effect of Po2 and external EMF on surface oscillation of levitated liquid droplets was systematically investigated for the precise measurements of surface tension and viscosity of high temperature liquids for future ISS experiments. We performed the observation of surface oscillations of levitated liquid alloys using PFLEX on board flight experiments by Gulfstream II (G-II) airplane operated by DAS. These observations were performed under the controlled Po2 and also under the suitable EMF conditions. In these experiments, we obtained the density, the viscosity and the surface tension values of liquid Cu. From these results, we discuss about as same as reported data, and also obtained the difference of surface oscillations with the change of the EMF conditions.

Watanabe, Masahito↗
NASA NTRS1973

Crystals for surface wave acoustic substrates, appendix C

The growth of single crystals in a space environment is discussed. Several crystals which could be beneficially grown in weightless conditions are identified. For surface wave acoustic applications, the surface perfection and internal crystal perfection which are obtainable in space, are favorably indicated.

Ulrich, D. R.↗
NASA NTRS1989

Surface Tension Confines Cryogenic Liquid

New type of Dewar provides passive, constant-temperature cryogenic cooling for scientific instruments under normal-to low-gravity conditions. Known as Surface-Tension-Contained Liquid Cryogen Cooler (STCLCC), keeps liquid cryogen in known location inside the Dewar by trapping liquid inside spongelike material. Unique sponge material fills most of volume of inner tank. Sponge is all-silica, open-cell material similar to that used for Space Shuttle thermal-protection tiles.

Castles, Stephen H.↗
DOE OSTI2024

Effect of Adsorbed Carboxylates on the Dissolution of Boehmite Nanoplates in Highly Alkaline Solutions

Understanding the dissolution of boehmite in highly alkaline solutions is important to the processing of the complex nuclear wastes stored at the Hanford (WA) and Savannah River (SC) sites. Here, we report the adsorption of model carboxylate anions on boehmite nanoplates in alkaline solutions and their effects on subsequent boehmite dissolution in 3 M NaOH at 80 °C. Although expectedly lower than at circumneutral pH, adsorption of oxalate at pH 13 at room temperature was significant and remained so through a linear decrease to 3 M NaOH conditions with no evidence for the appearance of new phases. Modeling of the adsorption data and rate were consistent with the formation of outer-sphere surface complexes. By using these conditions to preload the boehmite nanoplates with oxalate, and separately acetate, we measured and compared their dissolution behavior at 80 °C and observed a clear suppression of the dissolution rate for the case of adsorbed oxalate by 23% and for adsorbed acetate by 10% compared to pure solids. Ex situ scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization revealed no detectable difference in the morphologic evolution of the dissolving boehmite materials. In conclusion, we nonetheless conclude that pre-adsorbed carboxylate anions, even as nominally weakly bound outer-sphere complexes, can persist on the surface through highly alkaline conditions, decreasing the density of dissolution-active sites and thereby adding an extrinsic control on the dissolution rate.

Adsorption kinetics↗
NASA NTRS2019

Partially Chloritized Smectites: Analogues of Smectites at Gale Crater, Mars

Characterizing the structure and composition of phyllosilicates is important for interpreting the aqueous history of Mars and identifying potential habitable environments. Smectites and chlorites are the most dominant clay types on Mars, and there is evidence of the presence of smectite/chlorite intergrades. Smectite has been detected at Gale Crater, Mars, via orbital observations and in-situ measurements, in abundances up to approximately 25 weight percentage of bulk rock. John Klein (JK) and Cumberland (CB) were analyzed by the Chemistry and Mineralogy (CheMin) and Samples Analysis at Mars (SAM) evolved gas analysis experiment (EGA) instruments, onboard Mars Science Laboratory (MSL), Curiosity, to distinguish clay mineralogy. John Klein has a collapsed 2:1 smectite with a d-spacing of 10 Angstroms, whereas Cumberland smectite did not fully collapse and has a d-spacing of approximately 13.2 Angstroms. It has been suggested that partial chloritization or ‘pillaring’ could be responsible for the expanded Cumberland smectite because pillaring inhibits the collapse of smectites down to 10 Angstrom, even under the desiccating conditions on the martian surface. Clay minerals have been detected in ancient fluvio-lacustrine rocks throughout Curiosity’s traverse and catalog the changes of the lake water chemistry and diagenetic conditions at Gale Crater, Mars. Investigating clay minerals is important for identifying them on the Martian surface, in particular as Curiosity proceeds into the upcoming Clay-bearing Unit.

Tu, V. M.↗
NASA NTRS1979

Laminar and turbulent flows over spherically blunted cone and hyperboloid with massive surface blowing

Numerical solutions are presented for the flow over a spherically blunted cone and hyperboloid with massive surface blowing. Time-dependent viscous shock-layer equations are used to describe the flow field. The boundary conditions on the body surface include a prescribed blowing-rate distribution. The governing equations are solved by a time-asymptotic finite-difference method. Results presented here are only for a perfect gas-type flow at zero angle of attack. Both laminar and turbulent flow solutions are obtained. It is found that the effect of the surface blowing on the laminar flow field is to smooth out the curvature discontinuity at the sphere-cone juncture point, which results in a positive pressure gradient over the body. The shock slope increases on the downstream portion of the body as the surface blowing rate is increased. The turbulent flow with surface blowing is found to redevelop a boundary-layer-like region near the surface. The effects of this boundary-layer region on the flow field and heating rates are discussed.

Kumar, A.↗
NASA NTRS1983

Surface roughness effects with solid lubricants dispersed in mineral oils

The lubricating effectiveness of solid-lubricant dispersions are investigated in both point and line contacts using surfaces with both random and directional roughness characteristics. Friction and wear data obtained at relatively low speeds and at room temperature, indicate that the existence of solid lubricants such as graphite, MoS2, and PTFE in a plain mineral oil generally will not improve the effectiveness of the oil as a lubricant for such surfaces. Under boundary lubrication conditions, the friction force, as a function of time, initially depends upon the directional roughness properties of the contacting surfaces irrespective of whether the base oil or dispersions are used as lubricants.

Cusano, C.↗
NASA NTRS1985

Heat and detachment in core-complex extension

It is proposed here that the Miocene to Recent structural and volcanic features of the Basin and Range Province can be explained by a single thermotectonic process acting through time. This process consists of a thermal pulse resulting in a high-temperature regime that includes a steep thermal front moving first up toward the topographic surface, then down owing to cooling induced by a combination of convection and conduction. Within the front is a condition defining a critical surface that separates brittle from ductile behavior, and is marked by a nearly horizonal detachment fault. The most prominent and structurally highest position of the detachment results from interaction between the critical surface and a hydrothermal system near the topographic surface. These various features can be superposed on older ones through thermal remobilization or structural reactivation.

Lucchitta, I.↗
NASA NTRS2012

Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing - Part 2

Evaluation of metals to predict service life of metal-based structures in corrosive environments has long relied on atmospheric exposure test sites. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions similar to those of the corrosive environment. Their reliability to correlate to atmospheric exposure test results is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated corrosion testing has yet to be universally accepted as a useful tool in predicting the long-term service life of a metal, despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard, and their use is crucial, a method that correlates timescales from accelerated testing to atmospheric exposure would be very valuable. This paper presents work that began with the characterization of the atmospheric environment at the Kennedy Space Center (KSC) Beachside Corrosion Test Site. The chemical changes that occur on low carbon steel, during atmospheric and accelerated corrosion conditions, were investigated using surface chemistry analytical methods. The corrosion rates and behaviors of panels subjected to long-term and accelerated corrosion conditions, involving neutral salt fog and alternating seawater spray, were compared to identify possible timescale correlations between accelerated and long-term corrosion performance. The results, as well as preliminary findings on the correlation investigation, are presented.

Montgomery, Eliza L.↗
NASA NTRS2015

Laser Surface Preparation of Epoxy Composites for Secondary Bonding: Optimization of Ablation Depth

Surface preparation has been identified as one of the most critical aspects of attaining predictable and reliable adhesive bonds. Energetic processes such as laser ablation or plasma treatment are amenable to automation and are easily monitored and adjusted for controlled surface preparation. A laser ablation process was developed to accurately remove a targeted depth of resin, approximately 0.1 to 20 micrometers, from a carbon fiber reinforced epoxy composite surface while simultaneously changing surface chemistry and creating micro-roughness. This work demonstrates the application of this process to prepare composite surfaces for bonding without exposing or damaging fibers on the surface. Composite panels were prepared in an autoclave and had a resin layer approximately 10 micrometers thick above the fiber reinforcement. These composite panels were laser surface treated using several conditions, fabricated into bonded panels and hygrothermally aged. Bond performance of aged, experimental specimens was compared with grit blast surface treated specimens using a modified double cantilever beam test that enabled accelerated saturation of the specimen with water. Comparison of bonded specimens will be used to determine how ablation depth may affect average fracture energies and failure modes.

Palmieri, Frank L.↗
NASA NTRS1987

Generation of liquid water on Mars through the melting of a dusty snowpack

An optical/thermal model for dusty snowpacks at temperate Martian latitudes is used to investigate the possibility of valley network formation by liquid water that was provided by snowmelts, assuming insolation absorption under clear-sky conditions. The mean-annual surface temperatures for snow and the atmospheric exchange terms of the surface energy balance are constrained by global climate model results. Under favorable conditions, liquid water is generated at atmospheric pressures as low as 30-100 mbar, provided that the substrate is composed of regolith; this condition is in keeping with the cratered terrain expected in an ancient Martian surface.

Clow, Gary D.↗
NASA NTRS1945

An analysis of the dissipation of heat in conditions of icing from a section of the wing of the C-46 airplane

A method is given for calculating the temperature that a surface, heated internally by air, will assume in specified conditions of icing. The method can be applied generally to predict the performance, under conditions of icing, of the thermal system for protecting aircraft. Calculations have been made for a section of the wing of the C-46 airplane, and the results agree closely with the temperature measured. The limit of protection when the temperature of the surface reaches 32 degrees F., has been predicted for the leading edge. The temperature of the surface in conditions of icing with air at 0 degree F. also has been calculated. The effect of kinetic heating and the effect of the concentration of free water and size of droplet in the cloud are demonstrated.

Hardy, J K↗
DOE OSTI2022

Effects of Temperature on Flow Fouling of Smooth and Nonwetting Surfaces

Mineral fouling (scaling) of heat transfer surfaces is a pervasive problem in heat exchangers, chemical reactors, and other equipment in energy, environmental, and process industrial applications. Many of the applications involve dynamic flow of fluids with the impurity minerals and, furthermore, operate at elevated temperature. Strategies to mitigate fouling under these conditions are of much value in industrial applications. This paper presents a comparative study of temperature-dependent mineral fouling deposition on smooth surfaces and nonwetting superhydrophobic and lubricant-infused surfaces under dynamic flow conditions. The surfaces are represented in a unified manner using the viscosity ratio of the infused material within the porous asperities on a surface to that of the flowing fluid such that the spectrum of surfaces from superhydrophobic to smooth is captured by the range of viscosity ratios from 0 to ∞. Using a forced convection experimental setup, deposition of calcium sulfate on the surfaces is quantified in terms of asymptotic fouling resistance over a range of temperature, Reynolds number, and mineral foulant supersaturation. Through a systematic set of accelerated fouling experiments, an empirical relationship for the asymptotic fouling resistance is developed in terms of Reynolds number, foulant concentration, temperature, and surface type. The empirical model is validated with a comprehensive set of experimental data from this study as well as from the literature. Optimum nonwetting surface designs for minimizing fouling resistance compared to conventional smooth surfaces are developed as a function of temperature. The results of the study offer insight into the temperature-dependent fouling of surfaces under flow conditions and a rational design of fouling-resistant nonwetting surfaces that can be readily translated to practice.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRSDate not supplied

The Land Surface in Current and Planned MERRA Reanalysis Products

Current global atmospheric reanalysis products such as the European Centre for Medium-Range Weather Forecasts Reanalysis version 5 (ERA5), the NASA Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2), and the Japanese Reanalysis for Three Quarters of a Century (JRA-3Q) provide estimates of land surface states and fluxes, including soil moisture, soil temperature, snow mass, latent and sensible heat fluxes, and runoff, that are widely used in research and applications. These land surface estimates are based on land surface process models and, depending on the reanalysis product, on precipitation observations or the assimilation of land surface observations of soil moisture, soil temperature, snow conditions, and screen-level air temperature and humidity from satellite observations and in situ measurements. In this presentation, we review the land surface modeling and data assimilation components of the suite of current and planned MERRA reanalysis products. In addition to MERRA-2, we will discuss the latest NASA reanalysis, MERRA for the 21st century (M21C), which is currently under production, as well as the development and planning of the next version of the MERRA reanalysis, tentatively labeled MERRA-3. In MERRA-2, observations-based precipitation data products are used to correct the precipitation falling on the land surface. Outside of the high-latitudes and Africa, the daily, 0.5-degree, gauge-based Climate Prediction Center (CPC) Unified (CPCU) product is used. In Africa, the pentad, 2.5-degree, satellite- and gauge-based CPC Merged Analysis of Precipitation (CMAP) product is used. Poleward of 62.5 degrees latitude, the land surface sees the precipitation generated by the atmospheric model in the cycling data assimilation system. This configuration provides improved soil moisture estimates compared to those of the original (version 1) MERRA estimates, which did not benefit from the use of precipitation observations. Moreover, the use of precipitation observations facilitates a seamless spin-up of the land surface initial conditions across the MERRA-2 production streams. The use of a gauge-only precipitation product in MERRA-2 across much of the globe, however, adversely impacts the quality of the MERRA-2 land surface estimates in regions with poor gauge coverage, including most of South America and Australia. Therefore, the forthcoming M21C reanalysis uses satellite- and gauge-based precipitation from the Integrated Multi-satellitE Retrievals for the Global Precipitation Measurement Mission (IMERG). This change results in significant improvements in the quality of the M21C soil moisture estimates in the Southern Hemisphere compared to those from MERRA-2. Planning for MERRA-3 focuses on the assimilation of soil moisture observations from the Soil Moisture Active Passive (SMAP) mission and the Advanced Scatterometer (ASCAT), along with snow cover area fraction observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) to further improve the quality of the land surface estimates from the reanalysis. As a first step towards the assimilation of land surface observations in MERRA-3, the offline (land-only) M21C-Land reanalysis is currently under development as a supplemental M21C product that includes the assimilation of SMAP, ASCAT, and MODIS observations. Preliminary results from M21C and M21C-Land will be discussed in the context of MERRA-2 and plans for MERRA-3.

Rolf Reichle↗
NASA NTRS2005

Intermittent Behavior of the Separated Boundary Layer along the Suction Surface of a Low Pressure Turbine Blade under Periodic Unsteady Flow Conditions

The paper experimentally and theoretically studies the effects of periodic unsteady wake flow and aerodynamic characteristics on boundary layer development, separation and re-attachment along the suction surface of a low pressure turbine blade. The experiments were carried out at Reynolds number of 110,000 (based on suction surface length and exit velocity). For one steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, intermittency behaviors were experimentally and theoretically investigated. The current investigation attempts to extend the intermittency unsteady boundary layer transition model developed in previously to the LPT cases, where separation occurs on the suction surface at a low Reynolds number. The results of the unsteady boundary layer measurements and the intermittency analysis were presented in the ensemble-averaged and contour plot forms. The analysis of the boundary layer experimental data with the flow separation, confirms the universal character of the relative intermittency function which is described by a Gausssian function.

Oeztuerk, B↗
NASA NTRS1992

Development of physical and mathematical models for the Porous Ceramic Tube Plant Nutrification System (PCTPNS)

A physical model of the Porous Ceramic Tube Plant Nutrification System (PCTPNS) was developed through microscopic observations of the tube surface under various operational conditions. In addition, a mathematical model of this system was developed which incorporated the effects of the applied suction pressure, surface tension, and gravitational forces as well as the porosity and physical dimensions of the tubes. The flow of liquid through the PCTPNS was thus characterized for non-biological situations. One of the key factors in the verification of these models is the accurate and rapid measurement of the 'wetness' or holding capacity of the ceramic tubes. This study evaluated a thermistor based moisture sensor device and recommendations for future research on alternative sensing devices are proposed. In addition, extensions of the physical and mathematical models to include the effects of plant physiology and growth are also discussed for future research.

Tsao, D. Teh-Wei↗
NASA NTRS2003

Mechanical Behavior of Advanced Materials for Aerospace Applications

The purpose of this study was to determine whether High Cycle Fatigue (HCF) loading has any deleterious synergistic effect on life when combined with the typical Low Cycle Fatigue (LCF) loading present in engine disks. This interaction is particularly important in the rim region of blisk applications, where fatigue initiations from vibratory stresses (HCF) may be propagated to the disk by LCF. The primary effort in this study was focused on determining and documenting initiation sites and damage mechanisms. Under LCF loading conditions the failures were predominantly surface initiated, while HCF loading favored internal initiations. Deleterious HCF/LCF interactions would always result in a transition from internal to surface initiations. The results indicated that under the relative stress conditions evaluated there was no interaction between HCF and LCF. In FY99 this effort was extended to investigate several other loading conditions (R-ratio effects) as well as interactions between LCF and two-hour tensile dwells. The results will be published as a NASA Technical Memorandum.

Telesman, Ignancy↗
NASA NTRS2003

Validation of the Archived CERES Surface and Atmosphere Radiation Budget (SARB) at SGP

The CERES Surface and Atmosphere Radiation Budget (SARB) product (Charlock et al, 2002) includes the vertical profile of broadband SW, broadband LW, and 8-12 micron window (WN) fluxes; upwelling and downwelling at TOA, 70 hPa, 200 hPa, 500 hPa, and the surface; and for all-sky and clear-sky conditions. We test the archived CERES TRMM record of SARB for January-August 1998 and focus on discrepancies with ground-based measurements at SGP. The CERES SARB is generated by a highly modified Fu-Liou radiative transfer code (Fu and Liou, 1993). The most critical inputs for this application are cloud optical properties (fractional area, optical depth, particle size and phase, height of top, and estimate of geometrical thickness Minnis et al., 2002) from the narrowband VIRS imager. Numerous VIRS pixels (approx. 2km resolution at nadir) are matched to each of the large (approx. 20km) CERES broadband footprints (Wielicki et al, 1996). Other inputs include temperature and humidity from ECMWF (Rabier et al, 1998) , NCEP ozone profiles from SBUV and TOVS (Yang et al, 2001), aerosol optical thickness (AOT) from the Model for Atmospheric Transport and Chemistry (MATCH) aerosol assimilation (Collins et al., 2001) or alternately from the VIRS imager (Ignatov and Stowe, 2000). VIRS AOT is available for clear and partly cloudy ocean footprints during daylight; and only when viewing geometry renders a contribution from sunglint as unlikely. For other footprints, AOT is taken from MATCH. AOT is apportioned into fractions of dust (Tegan and Lacis, 1996), sea salt, sulfate, dust, soluble organic, insoluble organic, and soot (Hess et al., 1996) using the 6-hourly MATCH output. Tuned fluxes are retrieved by adjusting inputs to nudge computed TOA fluxes toward CERES observations (Rose et al, 1997). In clear conditions, the fields of humidity, surface skin temperature, surface albedo and AOT are adjusted to produce a closer match of computed and observed fluxes at TOA. When CERES footprints have clouds, the cloud optical thickness, fractional area within the footprint, and temperature of cloud top are adjusted by the tuning algorithm. Both tuned and untuned fluxes are archived, as are the respective adjustments to any parameters at the surface or within the atmosphere.

Charlock, Thomas P.↗

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