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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1938

The Effect of Surface Irregularities on Wing Drag. I. Rivets and Spot Welds: Rivets and Spot Welds - 1

Tests have been conducted in the NACA 8-foot high-speed wind tunnel to determine the effect of exposed rivet heads and spot welds on wing drag. Most of the tests were made with an airfoil of 5-foot chord. The air speed was varied from 80 to 500 miles per hour and the lift coefficient from 0 to 0.30. The increases in the drag of the 5-foot airfoil varied from 6%, due to countersunk rivets, to 27%, due to 3/32-inch brazier-head rivets, with the rivets in a representative arrangement. The drag increases caused by protruding rivet heads were roughly proportional to the height of the heads. With the front row of rivets well forward, changes in spanwise pitch had negligible effects on drag unless the pitch was more than 2.5% of the chord. Data are presented for evaluating the drag reduction attained by removing rivets from the forward part of the wing surface; for example, it is shown that over 70% of the rivet drag is caused by the rivets on the forward 30% of the airfoil in a typical case.

Hood, Manley J.↗
DOE OSTI2016

Surface area effects on the reduction of U VI in the presence of synthetic montmorillonite

Here, the redox transformations that affect the environmental mobility of metal or radionuclide contaminants typically take place in the presence of mineral or biological surfaces. Adsorption can alter the speciation and free energy of a dissolved ion and can thus change the occurrence, rate, or products of redox reactions relative to those expected in homogenous solution. Here, we investigated the effect of SYn-1, a redox-inactive synthetic montomorillonite clay mineral, on the reduction of U VI by dihydroanthraquinone-2,6 disulfonate (AH 2 QDS, the reduced form of the soluble electron shuttle AQDS). We varied the surface:U ratio in a circumneutral bicarbonate solution and measured the valence and atomic coordination of U in the solids using X-ray absorption spectroscopy (XANES and EXAFS). The spectra show that U IV was the predominant product both in the presence or absence of the clay mineral, indicating that adsorption of U VI to clay mineral surface sites does not affect its ability to be reduced by AH 2 QDS. In the absence of the clay mineral and at low-to-intermediate surface:U ratios the predominant UIV product was nanoparticulate uraninite, UO 2 . At the highest surface:U ratio tested (100 g/L clay mineral and 50 μM U) we observe a decrease in the proportion of uraninite down to 50%, with the remaining U IV present as adsorbed, non-uraninite species. These results are similar to previous findings with magnetite and rutile, where adsorbed U IV were the predominant species below a specific surface coverage and U in excess of this coverage was precipitated as uraninite. The threshold coverage determined here for the SYn-1 clay mineral is 10-100 × lower than that determined for magnetite and rutile, suggesting that clay mineral surfaces may be less important than metal oxides for stabilizing non-uraninite U IV species in natural sediments.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Experimental study of crystallization fouling by calcium carbonate: Effects of surface structure and material

We report mitigation of crystallization fouling on heat transfer surface is crucial for developing highly efficient desalination techniques, because the tenacious and porous crystal layer can drastically deteriorate system efficiency. Surface modification is a potential approach to decrease scale formation and promote crystal removal, but some of the mechanisms between crystallization and substrate properties are still not fully understood. In this study, we use dual-angle microscopic visualization and image processing to quantify three-dimensional crystallization behavior and analyze the impact of surface structure and material. The transition of crystal size and distance with roughness and wettability are identified from statistical analysis. The determination of crystal porosity and effective thermal conductivity is enabled by visualized geometry and measured deposition mass. This study shed lights on potential strategies of surface modification to mitigate scaling in desalination by enhancing scale removal and localizing crystal growth.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Effect of surface ionic screening on the polarization reversal scenario in ferroelectric thin films: Crossover from ferroionic to antiferroionic states

Nonlinear electrostatic interaction between the surface ions of electrochemical nature and ferroelectric dipoles gives rise to the coupled ferroionic states in nanoscale ferroelectrics. Here, we investigated the role of the surface ions formation energy value on the polarization states and polarization reversal mechanisms, domain structure and corresponding phase diagrams of ferroelectric thin films. Using 3D finite elements modeling we analyze the distribution and hysteresis loops of ferroelectric polarization and ionic charge, and dynamics of the domain states. These calculations performed over large parameter space delineate the regions of single- and poly- domain ferroelectric, ferroionic, antiferroionic and non-ferroelectric states as a function of surface ions formation energy, film thickness, applied voltage and temperature. We further map the analytical theory for 1D system onto effective Landau-Ginzburg free energy and establish the correspondence between the 3D numerical and 1D analytical results. In conclusion, this approach allows performing the overview of the ferroionic system phase diagrams and exploring the specifics of switching and domain evolution phenomena.

36 MATERIALS SCIENCE↗
NASA NTRS1978

An Induced Environment Contamination Monitor for the Space Shuttle

The Induced Environment Contamination Monitor (IECM), a set of ten instruments integrated into a self-contained unit and scheduled to fly on shuttle Orbital Flight Tests 1 through 6 and on Spacelabs 1 and 2, is described. The IECM is designed to measure the actual environment to determine whether the strict controls placed on the shuttle system have solved the contamination problem. Measurements are taken during prelaunch, ascent, on-orbit, descent, and postlanding. The on-orbit measurements are molecular return flux, background spectral intensity, molecular deposition, and optical surface effects. During the other mission phases dew point, humidity, aerosol content, and trace gas are measured as well as optical surface effects and molecular deposition. The IECM systems and thermal design are discussed. Preflight and ground operations are presented together with associated ground support equipment. Flight operations and data reduction plans are given.

Miller, E. R.↗
NASA NTRS1992

Stability analysis of surface tension effects on a double-diffusive layer

The linear stability characteristics of a fluid layer with simultaneous temperature and concentration gradients in a reduced gravity field are examined. The surface tension of the fluid is assumed to be a linear function of temperature and concentration. It is concluded that a small amount of gravity may damp out oscillatory instability or may alter its dynamics so that instability appears as steady convection. The onset of salt-finger instability may be in the overstable mode due to the surface tension method. The Lewis and Prandtl numbers of the material have a strong influence on the stability boundaries and onset characteristics of the system.

Chen, C. F.↗
DOE OSTI2017

Evaluating and modeling the effects of surface sampling factors on the recovery of organic chemical attribution signatures using the accelerated diffusion sampler and solvent extraction

In this study, an experimental design matrix was created and executed in order to test the effects of various real-world factors on the ability of the (1) accelerated diffusion sampler with solid phase micro-extraction (ADS-SPME) and (2) solvent extraction to capture organic chemical attribution signatures (CAS) from dimethyl methylphosphonate (DMMP) spiked onto painted wall board (PWB) surfaces. The DMMP CAS organic impurities sampled by ADS-SPME and solvent extraction were analyzed by gas chromatography/mass spectrometry (GC/MS). The number of detected DMMP CAS impurities and their respective GC/MS peak areas were determined as a function of DMMP stock, DMMP spiked volume, exposure time, SPME sampling time, and ADS headspace pressure. Based on the statistical analysis of experimental results, several general conclusions are made: (1) ADS-SPME with vacuum (i.e., reduced pressure) increased the amount of detected CAS impurity, as measured by GC/MS peak area, by a factor of 1.7 to 1.9 for PWB under certain experimental conditions, (2) the amount of detected CAS impurity was most influenced by spiked volume, stock, and ADS headspace pressure, (3) the ADS had no measurable effect on the number of detected DMMP impurities, that is, the ADS (with and without reduced pressure) had no practical effect on the DMMP impurity profile collected from spiked PWB, and (4) solvent extraction out performed ADS-SPME in terms of consistently capturing all or most of the targeted DMMP impurities from spiked PWB.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Use of a liquid-crystal, heater-element composite for quantitative, high-resolution heat transfer coefficients on a turbine airfoil, including turbulence and surface roughness effects

Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at roon temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

Hippensteele, Steven A.↗
NASA NTRS1987

Use of a liquid-crystal and heater-element composite for quantitative, high-resolution heat-transfer coefficients on a turbine airfoil including turbulence and surface-roughness effects

Local heat transfer coefficients were measured along the midchord of a three-times-size turbine vane airfoil in a static cascade operated at room temperature over a range of Reynolds numbers. The test surface consisted of a composite of commercially available materials: a Mylar sheet with a layer of cholestric liquid crystals, which change color with temperature, and a heater made of a polyester sheet coated with vapor-deposited gold, which produces uniform heat flux. After the initial selection and calibration of the composite sheet, accurate, quantitative, and continuous heat transfer coefficients were mapped over the airfoil surface. Tests were conducted at two free-stream turbulence intensities: 0.6 percent, which is typical of wind tunnels; and 10 percent, which is typical of real engine conditions. In addition to a smooth airfoil, the effects of local leading-edge sand roughness were also examined for a value greater than the critical roughness. The local heat transfer coefficients are presented for both free-stream turbulence intensities for inlet Reynolds numbers from 1.20 to 5.55 x 10 to the 5th power. Comparisons are also made with analytical values of heat transfer coefficients obtained from the STAN5 boundary layer code.

Hippensteele, S. A.↗
DOE OSTI2019

The Effects of Surface Longwave Spectral Emissivity on Atmospheric Circulation and Convection over the Sahara and Sahel

This study quantifies the impact of the inclusion of realistic surface spectral emissivity in the Sahara and Sahel on the simulated local climate and beyond. The surface emissivity in these regions can be as low as 0.6–0.7 over the infrared window band while close to unity in other spectral bands, but such spectral dependence has been ignored in current climate models. Realistic surface spectral emissivities over the Sahara and Sahel are incorporated into the Community Earth System Model (CESM) version 1.1.1, while treatments of surface emissivity for the rest of the globe remain unchanged. Both the modified and standard CESM are then forced with prescribed climatological SSTs and fixed present-day forcings for 35-yr simulations. The outputs from the last 30 years are analyzed. Compared to the standard CESM, the modified CESM has warmer surface air temperature, as well as a warmer and wetter planetary boundary layer over the Sahara and Sahel. The modified CESM thus favors more convection in these regions and has more convective rainfall, especially in the Sahara. The moisture convergence induced by such inclusion of surface spectral emissivity also contributes to the differences in simulated precipitation in the Sahel and the region south to it. Compared to observations, inclusion of surface spectral emissivity reduces surface temperature biases in the Sahara and precipitation biases in the Gulf of Guinea but exacerbates the wet biases in the Sahara. Such realistic representation of surface spectral emissivity can help unmask other factors contributing to regional biases in the original CESM.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Graphene: a Barrier to Hydrogen Permeation

Small area freestanding monolayer graphene has been shown to be impermeable to standard gases including hydrogen and helium.1 Several recent reports have suggested that graphene can be used as a hydrogen permeation barrier on metals.2 Those studies have relied on electrochemical hydrogen permeation measurements, which do a good job reproducing bulk permeability compared to gaseous diffusion but do not always reflect the real surface effects due to the difference in driving forces. This problem is magnified when measuring the permeability of thin coatings, which are dominated by surface effects. For this reason, we performed gas driven hydrogen permeation measurements of graphene coated metal samples. The diffusion of hydrogen through a metal can be described using Fick's and Sievert's Laws. Graphene-coated copper foils were prepared using chemical vapor deposition (CVD) with a methane precursor. Photo-reduced graphene samples were prepared by first sputtering a layer (∼15 nm) of copper on top of stainless steel foils. Graphene oxide in ethanol solutions were then drop cast on the surface and photo reduced using a neon lamp. A custom-designed apparatus has been assembled for measuring the hydrogen permeability of various materials. The operating principle of the system is as follows: A sample is sealed between the fore-sample and post-sample chambers using standard vacuum gaskets. Hydrogen is introduced into the fore sample region at varying pressures while the post sample region is maintained under high vacuum. Due to the concentration gradient, hydrogen then diffuses through the material and is detected using a quadrupole mass spectrometer. This process is repeated at several temperatures. The mass spectrometer was calibrated using an orifice with known conductance in place of the sample. Data collection and reduction were automated using scripts written in LabVIEW and Octave, respectively. We saw a decrease in the hydrogen permeability of copper after adding graphene to the surface for small temperature steps. This result is also observed when considering temperature steps of 20 K. Future Work: Apply this methodology to graphene-coated 316L stainless steel. The hydrogen permeability of 316L steel should also decrease with the addition of graphene to the surface. Determine methods for graphene defect reduction.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1981

OEX - Use of the Shuttle Orbiter as a research vehicle

The Orbiter Experiments Program to provide research instrumentation on the Shuttle Orbiter is discussed. Flight aerodynamic problems such as ground-based data limitations, rarefied flow effects, body flap and control surface effectiveness, and windward surface heat transfer are reviewed. Experiments currently under development are described, including experiments on tile gaps and wall catalytic effects which provide the opportunity to obtain data not available in ground facilities and apply the results to improvements in the Orbiter's thermal protection system. Such experiments combined with other instrumentation on the Orbiter should provide benchmark flight data which can make a significant impact on the design of future space transportation systems.

Jones, J. J.↗
NASA NTRS1958

A Theoretical and Experimental Study of Planing Surfaces Including Effects of Cross Section and Plan Form

A summary is given of the background and present status of the pure-planing theory for rectangular flat plates and v-bottom surfaces. The equations reviewed are compared with experiment. In order to extend the range of available planing data, the principal planing characteristics for models having sharp bottom surfaces having constant angles of dead rise of 20 degrees and 40 degrees. Planing data were also obtained for flat-plate surfaces with very slightly rounded chines for which decreased lift and drag coefficients are obtained.

Shuford, Charles L , Jr↗
DOE OSTI2020

Polydopamine Surface Coating Synergizes the Antimicrobial Activity of Silver Nanoparticles

Metal nanoparticles, especially silver nanoparticles (AgNPs), have drawn increasing attention for antimicrobial applications. Most studies have emphasized on the correlations between the antibacterial potency of AgNPs and the kinetics of metallic to ionic Ag conversion, while other antimicrobial mechanisms have been underestimated. In this work, we focused on the surface effects of polydopamine (PDA) coating on the antimicrobial activity of AgNPs. A method of fast deposition of PDA was used to synthesize the PDA-AgNPs with controllable coating thickness ranging from 3 to 25 nm. The antimicrobial activities of the PDA-AgNPs were analyzed by fluorescence-based growth curve assays on Escherichia coli. The results indicated that the PDA-AgNPs exhibited significantly higher antibacterial activities than poly(vinylpyrrolidone)-passivated AgNPs (PVP-AgNPs) and PDA themselves. It was found that the PDA coating synergized with the AgNPs to prominently enhance the potency of the PDA-AgNPs against bacteria. Additionally, the analysis of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy elucidated that the synergistic effects could be originated from the interaction/coordination between Ag and catechol group on the PDA coating. The synergistic effects led to increased generation of reactive oxygen species and the consequent bacterial damage. Overall, these findings demonstrated the importance of the surface effects on the antimicrobial properties of AgNPs. The underlying molecular mechanisms have shined light on the future development of more potent metal nanoparticle-based antimicrobial agents.

36 MATERIALS SCIENCE↗
NASA NTRS2001

Subsurface Sounding of Mars: The Effects of Surface Roughness

The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) will conduct a global survey of Mars from the Mars Express Orbiter starting in 2004. The primary objective of the subsurface observations is to detect material interfaces in the upper several kilometers of the crust of Mars, with a particular emphasis on mapping the 3D distribution of water and ice in that portion of the crust. In order to detect subsurface interfaces, the returned echo from the subsurface must be distinguished from noise and clutter, which can arise from a variety of sources. One source of clutter is surface topography that generates backscattered energy at the same time delay as the subsurface region of interest. Surface topography can affect the detectability of subsurface features in several other ways. Surface roughness at scales comparable or somewhat smaller than the radar wavelength reduces the coherency of the wave as it passes the upper interface. Also, surface slope (tilt) at scales of the radar footprint and larger (> 5 km) affects the apparent Doppler signature of the echoes, and effectively disperses the wave transmitted into the subsurface, making processing and interpretation difficult. In this paper, we report on the roughness characteristics of Mars at these various scales as measured by the Mars Global Surveyor Laser Altimeter (MOLA), and consider the implications for achieving the subsurface sounding goals of MARSIS. Additional information is contained in the original extended abstract.

Plaut, J. J.↗
NASA NTRS1993

A method for the compensation of the effects of surface cloth impressions on polar backscatter applied to porous epoxy and biaxial graphite/epoxy composites

The anisotropy of polar backscatter from graphite/epoxy composites is a potentially useful parameter for the characterization of porosity levels. However, the effects of release-cloth impressions on measured integrated polar backscatter levels are sufficient to inhibit the detection of porosity with this method. Recently, we developed a theoretical model to predict the frequency distribution of the backscattered power along the high-symmetry directions of release-cloth impressions. This study investigates experimentally the usefulness of limiting the bandwidth to regions not dominated by the scattering from the surface impressions, hence increasing the probability of detecting flaws such as porosity.

Madaras, Eric I.↗