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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Measurements of the Viscosity of the Undercooled Melts Under the Conditions of Microgravity and Supporting MHD Calculations

This report covers the work to support the measurement of the surface tension and viscosity of undercooled metals with the TEMPUS as a part of the IML-2 mission. This work consisted of two parts. First was the ground-based research program, whose purpose was to establish the feasibility of the flight program and to establish the knowledge base necessary to plan a successful flight program. Analytical calculations established a fundamental understanding of the problem, and then a more rigorous program of numerical calculations was employed in the development of the experimental program. The second part of the covered research was the actual flight program, developed in close collaboration with Prof. Egry. A metal sphere was levitated and melted, and then set oscillating by 'squeezing' it with the magnetic field. The droplet's oscillations were recorded on videotape and digital image analysis was employed in reduction of the data. The experiment was successful because surface tension measurements were obtained for the gold and gold-copper alloy samples. This data provides unique experimental evidence in support of theories about electromagnetic levitation on the ground. Because of unforeseen difficulties with stability of liquid samples in TEMPUS, the viscosity measurements were not possible, but the data collection and analysis techniques were well proven in this mission. Further research is being conducted regarding the measurement of viscosity by this technique.

Szekely, Julian↗
NASA NTRS1998

Measurement of Xenon Viscosity as a Function of Low Temperature and Pressure

The measurement of xenon gas viscosity at low temperatures (175-298 K) and low pressures (350 torr-760 torr) has been performed in support of Hall Thruster testing at NASA Lewis Research Center. The measurements were taken using the capillary flow technique. Viscosity measurements were repeatable to within 3%. The results in this paper are in agreement with data from Hanley and Childs and suggest that the data from Clarke and Smith is approximately 2% low. There are no noticeable pressure effects on xenon absolute viscosity for the pressure range from 350 torr to 760 torr.

Grisnik, Stanley P.↗
NASA NTRS1999

Surface Tension and Viscosity Measurements in Microgravity: Some Results and Fluid Flow Observations during MSL-1

The viscosity of a liquid metal was successfully measured for the first time by a containerless method, the oscillating drop technique. This method also provides a means to obtain a precise, non-contact measurement of the surface tension of the droplet. This technique involves exciting the surface of the molten sample and then measuring the resulting oscillations; the natural frequency of the oscillating sample is determined by its surface tension, and the damping of the oscillations by the viscosity. These measurements were performed in TEMPUS, a microgravity electromagnetic levitator (EML), on the Space Shuttle as a part of the First Microgravity Science Laboratory (MSL-1), which flew in April and July 1997 (STS-83 and STS-94). Some results of the surface tension and viscosity measurements are presented for Pd82Si18. Some observations of the fluid dynamic characteristics (dominant flow patterns, turbulent transition, cavitation, etc.) of levitated droplets are presented and discussed together with magnetohydrodynamic calculations, which were performed to justify these findings.

Hyer, Robert W.↗
NASA NTRS1999

Damping of drop oscillations by surfactants and surface viscosity

An energy equation is derived for the general case of a viscous drop suspended in a viscous medium with surfactants contaminating the interface. It contains terms that clearly identify dissipation contributions from the viscous effects in the bulk fluids, surface shear and dilatational viscosity effects at the interface, and surfactant transport. An efficient boundary integral method is developed which incorporates the effects of a constant surface dilatational viscosity in simulations of an oscillating two-dimensional inviscid drop. Surface dilatational viscosity is shown to have a significant damping effect on the otherwise undamped inviscid oscillations.

Rush, Brian M.↗
NASA NTRS1993

Effect of Bulk Viscosity on the Oscillating Screen Viscometer

Close to the critical temperature, the bulk viscosity of the xenon sample will exceed the shear viscosity by more than a factor of a billion. Nevertheless, the viscometer's low operating frequency ensures that the only significant force on the oscillating screen will be due to the shear viscosity.

Berg, Robert F.↗
NASA NTRS2003

A Reassessment of the Emplacement and Erosional Potential of Turbulent, Low-Viscosity Lavas on the Moon

We have reevaluated the role of thermal erosion by low-viscosity lunar lavas as a mechanism or the formation of the lunar sinuous rilles. We have adapted the model of Williams et aL and used the compositions of an Apollo 12 basalt and a terrestrial komatiitic basalt to investigate the compositional and environmental effects on the flow behavior of low-viscosity lavas on the Moon and Earth. Our model predict that lunar lava could have erupted as turbulent flows that were capable of flowing hundreds of kilometers on a sufficiently flat, unobstructed substrate. These results are consistent with previous studies. Modeling of lava over a substrate of the same composition shows that thermal erosion rates would have been low (approx. 10 cm/d). As a result, long-duration eruptions (approximately months to years) would have been required to incise deep (tens to hundreds of meters) channels. Partial melting and mechanical removal of the substrate, a mechanism suggested by Hulme to enhance erosion, only slightly increases thermal erosion rules. Other factors, such as higher flow rates or lava superheating, could have produced deep rilles by thermal erosion during shorter-duration eruption. A superheated lunar lava not only would have had a higher erosion rate (approx. 40 cm/d) but also would have remained uncrusted for tens of kilometers, which is consistent with the open channel morphology of most sinuous rilles. For lunar lavas with large volatile (t.e., vesicle) contents, the presence of vesicles would have tended to increase viscosity at low strain rates, resulting in shorter turbulent flow distances, lower thermal erosion rates, and thus shallower erosion channel depths for given eruption durations.

William, David A.↗
NASA NTRS2006

Viscosity Measurement for Tellurium Melt

The viscosity of high temperature Te melt was measured using a new technique in which a rotating magnetic field was applied to the melt sealed in a suspended ampoule, and the torque exerted by rotating melt flow on the ampoule wall was measured. Governing equations for the coupled melt flow and ampoule torsional oscillation were solved, and the viscosity was extracted from the experimental data by numerical fitting. The computational result showed good agreement with experimental data. The melt velocity transient initiated by the rotating magnetic field reached a stable condition quickly, allowing the viscosity and electrical conductivity of the melt to be determined in a short period.

Lin, Bochuan↗
NASA NTRS2006

A Method for Calculating Viscosity and Thermal Conductivity of a Helium-Xenon Gas Mixture

A method for calculating viscosity and thermal conductivity of a helium-xenon (He-Xe) gas mixture was employed, and results were compared to AiResearch (part of Honeywell) analytical data. The method of choice was that presented by Hirschfelder with Singh's third-order correction factor applied to thermal conductivity. Values for viscosity and thermal conductivity were calculated over a temperature range of 400 to 1200 K for He-Xe gas mixture molecular weights of 20.183, 39.94, and 83.8 kg/kmol. First-order values for both transport properties were in good agreement with AiResearch analytical data. Third-order-corrected thermal conductivity values were all greater than AiResearch data, but were considered to be a better approximation of thermal conductivity because higher-order effects of mass and temperature were taken into consideration. Viscosity, conductivity, and Prandtl number were then compared to experimental data presented by Taylor.

Johnson, Paul K.↗
NASA NTRS2010

Viscosity Measurement via Drop Coalescence: A Space Station Experiment

The concept of using low gravity experimental data together with CFD simulations for measuring the viscosity of highly viscous liquids was recently validated on onboard the International Space Station (ISS). A series of microgravity tests were conducted for this purpose on the ISS in July, 2004 and in May of 2005. In these experiments two liquid drops were brought manually together until they touched and were allowed to coalesce under the action of the capillary force alone. The coalescence process was recorded photographically from which the contact radius speed of the merging drops was measured. The liquid viscosity was determined by fitting the measured data with accurate numerical simulation of the coalescence process. Several liquids were tested and for each liquid several drop diameters were employed. Experimental and numerical results will be presented in which the viscosity of several highly viscous liquids were determined using this technique.

Antar, Basil↗
NASA NTRS1961

Viscosity Difference Measurements for Normal and Para Liquid Hydrogen Mixtures

The absence of experimental data in the literature concerning a viscosity difference for normal and equilibrium liquid hydrogen may be attributed to the limited reproducibility of "oscillating disk" measurements in a liquid-hydrogen environment. Indeed, there is disagreement over the viscosity values for equilibrium liquid hydrogen even without proton spin considerations. Measurements presented here represent the first application of the piezoelectric alpha quartz torsional oscillator technique to liquid-hydrogen viscosity measurements.

Webeler, R.↗
NASA NTRS2018

A Deep X-Ray Look at Abell 2142-Viscosity Constraints from Kelvin-Helmholtz Eddies, a Displaced Cool Peak that Makes a Warm Core, and A Possible Plasma Depletion Layer

cold fronts in detail. We find that the southern cold front exhibits well-developed Kelvin–Helmholtz (KH) eddies seen in the sky plane. Comparing their wavelength and amplitude with those in hydrodynamic simulations of cold fronts in viscous gas, and estimating the gas tangential velocity from centripetal acceleration, we constrain the effective viscosity to be at most 1/5 of Spitzer isotropic viscosity, but consistent with full Braginskii anisotropic viscosity for magnetized plasma. While the northwestern front does not show obvious eddies, its shape and the structure of its brightness profile suggest KH eddies seen in projection. The southern cold front continues in a spiral to the center of the cluster, ending with another cold front only 12 kpc from the gas density peak. The cool peak itself is displaced ∼30 kpc from the brightest cluster galaxy (BCG) (the biggest such offset among centrally peaked clusters), while the X-ray emission on a larger scale is still centered on the BCG, indicating that the BCG is at the center of the gravitational potential and the cool gas is sloshing in it. The specific entropy index of the gas in the peak (K≈49 keV sq.cm) makes A2142 a rare “warm core”; apparently the large displacement of the cool peak by sloshing is the reason. Finally, we find a subtle narrow, straight channel with a 10% drop in X-ray brightness, aligned with the southern cold front—possibly a plasma depletion layer in projection.

Wang, Qian H. S.↗
DOE OSTI2025

pH-SWITCHABLE DYNAMIC BINARY COMPLEXES AS VISCOSITY MODIFYING AGENTS

The study of supramolecular structures has been gaining a lot of momentum in recent years due to their potential application in several interesting areas such as medicine, catalysis, energy, oil and gas, etc. Hydraulic fracturing is one area where the ongoing demand for novel viscosity modifiers has prompted researchers to explore various facets of chemistry. In this study, a dynamic binary complex (DBC) solution is presented, with the potential to be useful in the hydraulic fracturing domain. It has a supramolecular structure that is formed by the self-assembly of oleic acid and diethylenetriamine into an elongated network under alkaline conditions. With less than 2 wt% of constituents in aqueous solution, a viscous gel that exhibits high viscosities even under shear was formed. It was sensitive to pH and salinity, and its zero-shear viscosity could be tuned by a factor of ~280 by changing the pH. Furthermore, its viscous properties were pronounced in the presence of salt. Sand settling tests revealed its potential to hold up sand particles for extended periods of time, longer than 24 hours. In conclusion, this DBC solution system has potential to be utilized as a smart pH-switchable hydraulic fracturing fluid that can be prepared using seawater.

02 PETROLEUM↗
DOE OSTI2019

Effect of Al{sub 2}O{sub 3}/(B{sub 2}O{sub 3 }+ Na{sub 2}O) Ratio on CaO-Al{sub 2}O{sub 3}-Based Mold Fluxes: Melting Property, Viscosity, Heat Transfer, and Structure

CaO-Al{sub 2}O{sub 3}-based mold fluxes, which are under development for the continuous casting of high-Al steel, contain fluxing compounds, such as Na{sub 2}O and B{sub 2}O{sub 3}. The reaction between [Al] and the fluxing agents in mold fluxes leads to an increase in Al{sub 2}O{sub 3} and a decrease in B{sub 2}O{sub 3} and Na{sub 2}O concentrations, changing the properties of mold fluxes. The effect of the Al{sub 2}O{sub 3}/(B{sub 2}O{sub 3 }+ Na{sub 2}O) ratio on the melting properties, viscosity, heat transfer, and structure of the CaO-Al{sub 2}O{sub 3}-based mold fluxes is presented in this work. The increase of the Al{sub 2}O{sub 3}/(B{sub 2}O{sub 3 }+ Na{sub 2}O) ratio in the fluxes raised the melting temperature and high-temperature viscosity of mold fluxes but decreased the heat transfer rate across the flux disks. It also enhanced the degree of polymerization by promoting the formation of 3-D aluminate structure, which accounted for the change of the viscous behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Early-Stage Shear Viscosity far from Equilibrium via Holography

We report shear viscosity is a crucial property of QCD matter which determines the collective behavior of the the quark-gluon plasma (QGP) in ultrarelativistic heavy-ion collisions. Extending the near-equilibrium, high-precision investigations in theory and experiment, we take into account the fact that, in a collision, the QGP is generated far from equilibrium. We use the AdS/CFT correspondence to study a strongly coupled plasma and find a significant impact on the ratio of shear viscosity to entropy density, η/s. In particular, we investigate the initial heating phase and find a decrease reaching down to below 60% followed by an overshoot to 110% of the near-equilibrium value. This finding might be highly relevant for the extraction of transport coefficients from anisotropic flow measurements at RHIC and LHC.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Viscosity-Controlled Thiol–Ene Reaction and Its Impact on Mechanical Response of Dynamic Networks

The impact of curing conditions on the final properties of thioester-thiol-based dynamic polymer networks was systematically investigated. Despite identical monomer and cross-linker compositions, networks synthesized in the absence of solvent exhibited significantly higher shear moduli and longer relaxation times compared to those cured in solvent. These differences arise from viscosity-controlled photoinitiated thiol–ene reactions, where reduced chain mobility under solvent-free conditions suppresses termination between two polymer radicals, leading to higher reaction conversion. Fourier Transform Infrared (FTIR) spectroscopy and solid-state NMR (ssNMR) spectroscopy confirmed a greater degree of “click” reaction completion in higher viscosity environments. Control experiments revealed that prolonged radical lifetimes and suppressed termination reactions under solvent-free curing conditions contribute to these variations. Here, this study highlights the crucial role of processing conditions in determining cross-link density and, consequently, the dynamic mechanical behavior of polymer networks. It demonstrates that, beyond polymer chemistry, dynamic cross-linker design, and phase separation, curing conditions serve as a key design parameter for tailoring material performance to specific applications.

polymers↗
DOE OSTI2025

Effect of Viscosity of a Deep Eutectic Solvent on CO 2 Capture Performance in an Energy-Efficient Membrane Contactor-Based Process

Greenhouse gas contributions to climate change have driven intense interest in the separation of CO 2 from wet flue gas streams. Deep eutectic solvents (DESs) are an emerging class of highly selective CO 2 absorbents. A prototypical DES, reline, is a mixture of choline chloride and urea. Reline is a thermally stable, nontoxic, and biodegradable solvent with negligible volatility and is inexpensive. We demonstrate a scalable and energy-efficient hollow fiber membrane contactor (HFMC)-based process using a green solvent for CO 2 capture. This process uses reline in HFMC to provide close interfacial interactions and contact between DES and CO 2 . This approach overcomes the disadvantages associated with direct absorption in DES and could potentially be applied to a variety of solvent-based CO 2 capture methods. Commercial, low-cost polymer hollow fiber membranes were evaluated for the capture of CO 2 with reline. From a mixed gas containing N 2 and CO 2 , the DES-based HFMC separated CO 2 with a purity of 97 mol %. The effect of the viscosity of reline on the CO 2 capture performance was investigated by adding water to the reline. The addition of water to reline significantly reduced its viscosity, which led to a permeate flux of 170 mmol/(m 2 ·h) at 35 °C, 4 bar, and 60 wt % water in solvent, which was approximately 8 times higher than that of the pure reline in the membrane contactor system. In situ Fourier transform infrared spectroscopy and nuclear magnetic resonance (NMR) revealed that reline absorbs CO 2 by physical absorption without forming new chemical compounds and that CO 2 separation by reline occurs via the pressure swing mechanism. This research provides fundamental insights about green physical solvent-based separation processes and a pathway toward industrial deployment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Using Ionic Liquid Additive to Enhance Lubricating Performance for Low-Viscosity Engine Oil

Energy efficient lubricants are essential for sustainable transportation, and the trend is to develop and implement lower viscosity lubricants with more effective additives. Ionic liquids (ILs) have been reported as candidate additives with superior friction and wear reducing capabilities. Unlike most literature relying on bench-scale testing of simple oil–IL blends, this study produced low-viscosity (SAE 0W-12) fully formulated engine oils using a phosphonium-organophosphate IL as an antiwear additive and evaluated them in both bench-scale tribological testing and full-scale fired engine dynamometer testing. The experimental formulation containing a combination of ZDDP and IL outperformed the formulations using either ZDDP or IL alone, as well as a commercial SAE 0W-20 engine oil in terms of mitigating boundary friction, wear, and contact fatigue-induced micropitting. Furthermore, racing engine dynamometer tests demonstrated 3–4 °C lower oil temperature, 4–5 ft-lbs higher horsepower output, and up to 9.9% better fuel economy for the IL-containing SAE 0W-12 experimental oil compared with selected commercial SAE 5W-30 and 0W-20 engine oils.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Nanoscale Hybrid Electrolytes with Viscosity Controlled Using Ionic Stimulus for Electrochemical Energy Conversion and Storage

As renewable energy is rapidly integrated into the grid, the challenge has become storing intermittent renewable electricity. Technologies including flow batteries and CO 2 conversion to dense energy carriers are promising storage options for renewable electricity. To achieve this technological advancement, the development of next generation electrolyte materials that can increase the energy density of flow batteries and combine CO 2 capture and conversion is desired. Liquidlike nanoparticle organic hybrid materials (NOHMs) composed of an inorganic core with a tethered polymeric canopy (e.g., polyetheramine (HPE)) have a capability to bind chemical species of interest including CO 2 and redox-active species. In this study, the unique response of NOHM-I-HPE-based electrolytes to salt addition was investigated, including the effects on solution viscosity and structural configurations of the polymeric canopy, impacting transport behaviors. The addition of 0.1 M NaCl drastically lowered the viscosity of NOHM-based electrolytes by up to 90%, reduced the hydrodynamic diameter of NOHM-I-HPE, and increased its self-diffusion coefficient, while the ionic strength did not alter the behaviors of untethered HPE. This study is the first to fundamentally discern the changes in polymer configurations of NOHMs induced by salt addition and provides a comprehensive understanding of the effect of ionic stimulus on their bulk transport properties and local dynamics. These insights could be ultimately employed to tailor transport properties for a range of electrochemical applications.

25 ENERGY STORAGE↗