Search NASA⌕ Search

SEARCH · Search NASA

Results for “VISCOSITY”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Viscosity of mafic magmas at high pressures

While it is accepted that silica-rich melts behave anomalously with a decrease of their viscosity at increased pressures (P), the viscosity of silica-poor melts is much less constrained. However, modeling of mantle melts dynamics throughout Earth's history, including the magma ocean era, requires precise knowledge of the viscous properties of silica-poor magmas. We extend here our previous measurements on fayalite melt to natural end-members pyroxenite melts (MgSiO 3 and CaSiO 3 ) using in situ X-ray radiography up to 8 GPa. For all compositions, viscosity decreases with P, rapidly below 5 GPa and slowly above. The magnitude of the viscosity decrease is larger for pyroxene melts than for fayalite melt and larger for the Ca end-member within pyroxene melts. The anomalous viscosity decrease appears to be a universal behavior for magmas up to 13 GPa, while the P dependence of viscosity beyond this remains to be measured. In conclusion, these results imply that mantle melts are very pervasive at depth.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Plasma viscosity with mass transport in spherical inertial confinement fusion implosion simulations

The effects of viscosity and small-scale atomic-level mixing on plasmas in inertial confinement fusion(ICF) currently represent challenges in ICF research. Many current ICF hydrodynamic codes ignore the effects of viscosity though recent research indicates viscosity and mixing by classical transport processes may have a substantial impact on implosion dynamics. In this paper, we have implemented a Lagrangian hydrodynamic code in one-dimensional spherical geometry with plasmaviscosity and mass transport and including a three temperature model for ions, electrons, and radiation treated in a gray radiation diffusion approximation. The code is used to study ICF implosion differences with and without plasmaviscosity and to determine the impacts of viscosity on temperature histories and neutron yield. It was found that plasmaviscosity has substantial impacts on ICF shock dynamics characterized by shock burn timing, maximum burn temperatures, convergence ratio, and time history of neutron production rates. Finally, plasmaviscosity reduces the need for artificial viscosity to maintain numerical stability in the Lagrangian formulation and also modifies the flux-limiting needed for electron thermal conduction.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Volatility and Viscosity Are Correlated in Terpene Secondary Organic Aerosol Formed in a Flow Reactor

Secondary organic aerosol (SOA) is a complex mixture of largely unspeciated compounds. Volatility and viscosity of the bulk organic aerosol influence new particle formation, processing, and lifetime in the atmosphere. Relationships between these properties are well-defined for pure compounds, but currently unavailable for bulk organic aerosol. In this survey study, we characterized SOA formed from a range of biogenic precursors and conditions in an oxidation flow reactor for volatility (thermodenuder), viscosity (dimer coagulation, isolation, and coalescence), and oxidation state (aerosol chemical speciation monitor). We find linear trends in log-linear and log-log plots of single-parameter representations of volatility and viscosity, with higher condensed phase fractions of extremely low and low volatility material associated with increased viscosity (R=0.69). Per this relationship, a 10% increase in the contribution of these fractions (i.e., lower volatility) results in an increase in viscosity of approximately 200%. The viscosity (at 30°C) of SOA fell between $6.2 × 10^5$ to $8.0 × 10^8$ Pa s, and thus in the semi-solid range. SOA oxidation state ranged from -1.0 and 0.1, and was weakly anti-correlated with volatility (but not viscosity). We found larger SOA mass loadings generally associated with increased volatility and decreased viscosity. Overall, the results of this preliminary study are consistent with “molecular corridor”-style frameworks employing molecular mass and volatility to estimate viscosity to bulk real-world SOA.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Viscosity of glass-forming melt at the bottom of high-level waste melter feed cold caps: Effects of temperature and incorporation of solid components

At the final stages of conversion of melter feed (glass batch) to molten glass, the transient glass-forming melt becomes a continuous liquid phase encapsulating dissolving solid particles and gas bubbles that produce primary foam at the bottom of the cold cap (the reacting melter feed in an electric glass melting furnace). The glass-forming melt viscosity plays a dominant role in primary foam formation, stability, and eventual collapse, thus affecting the rate of melting (the glass production rate per cold cap area). For several melter feeds designed for nuclear waste vitrification, we have traced the glass-forming melt viscosity during the final stages of feed-to-glass conversion as it changes in response to changing temperature and composition (resulting from dissolving solid particles). Starting with a relatively low values at the moment when the melt connects, melt viscosity reaches maximum within the primary foam layer and then decreases to its final melter-operating temperature value. We paid a particular attention to the cold-cap bottom—the boundary between the primary foam layer and the thermal boundary layer—where the melt viscosity affects the rate of melting predominantly through its effect on the temperature at which primary foam is collapsing.

Lee, Seung Min↗
DOE OSTI2019

Directed Hydrogen Bond Placement: Low Viscosity Amine Solvents for CO2 Capture

Capture of CO2 from power generation is required for its conversion or sequestration. Toward this goal, numerous CO2 capture processes have been developed, with the most widely deployed technology utilizing aqueous solutions of amines. Our group has focused on the design of several classes of water-lean solvents in order to identify molecular-level descriptors to control materials properties such as viscosity and regeneration energy. Large scale molecular simulations have shown that strategic placement of hydrogen bonding and tuning of the acid/base equilibria are critical for controlling viscosity at CO2-rich loadings. Here, we extend these principles to a new class of pyridine-based molecules with a secondary amine functionality for binding CO2. The result is a class of water-lean amines that retain high gravimetric capacity (20%) while exhibiting the lowest CO2-rich viscosities (<150 cP, 40 °C) of any 100% concentrated amine currently known. Additionally, these newly identified solvents exhibit regeneration temperatures as low as 60 °C when applying a polarity swing assisted regeneration, resulting in a solvent that can conceptually absorb and desorb CO2 with only a 20 °C temperature swing.

Malhotra, Deepika↗
DOE OSTI2017

Melter feed viscosity during conversion to glass: Comparison between low-activity waste and high-level waste feeds

During nuclear waste vitrification, a melter feed (generally a slurry-like mixture of a nuclear waste and various glass forming and modifying additives) is charged into the melter where undissolved refractory constituents are suspended together with evolved gas bubbles from complex reactions. Knowledge of flow properties of various reacting melter feeds is necessary to understand their unique feed-to-glass conversion processes occurring within a floating layer of melter feed called a cold cap. The viscosity of two low-activity waste (LAW) melter feeds were studied during heating and correlated with volume fractions of undissolved solid phase and gas phase. In contrast to the high-level waste (HLW) melter feed, the effects of undissolved solid and gas phases play comparable roles and are required to represent the viscosity of LAW melter feeds. This study can help bring physical insights to feed viscosity of reacting melter feeds with different compositions and foaming behavior in nuclear waste vitrification.

Jin, Tongan↗
DOE OSTI2016

Highly Branched Polyethylenes as Lubricant Viscosity and Friction Modifiers

A series of highly branched polyethylenes (BPE) were prepared and used in a Group I base oil as potential viscosity and friction modifiers. The lubricating performance of these BPEs supports the expected dual functionality. Changes in polarity, topology, and molecular weight of the BPEs showed significant effects on the lubricants’ performance, which provide scientific insights for polymer design in future lubricant development.

Branchedpolyethylene↗
DOE OSTI2018

Measurement of the Kinematic Viscosity of Melted Mixtures of Sodium, Lithium, and Beryllium Fluorides and the Effect of the Eutectic Additive Cerium Trifluoride on the Viscosity

Experimental data on the kinematic viscosity and liquidus temperature of certain fused mixtures of sodium, lithium, and beryllium fluorides were obtained, by the method of damping of torsional oscillations of a cylinder with the experimental melt, in validation of the concept of molten-salt incinerator reactors for incinerating transuranium elements from spent nuclear fuel from light-water reactors. The measurements were conducted from the liquidus temperature to 800°C. The effect of the addition of cerium trifluoride on the viscosity of the eutectic melt 58NaF–15LiF–27BeF{sub 2} was studied. It was shown that the additive appreciably reduces the viscosity at low temperature and also lowers the liquidus temperature. The parameters characterizing the temperature dependence of viscosity were determined for the experimental melts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Cyanohydridoborate Anions: Synthesis, Salts, and Low‐Viscosity Ionic Liquids

Abstract High‐yield syntheses up to molar scales for salts of [BH(CN) 3 ] − ( 2 ) and [BH 2 (CN) 2 ] − ( 3 ) starting from commercially available Na[BH 4 ] (Na 5 ), Na[BH 3 (CN)] (Na 4 ), BCl 3 , (CH 3 ) 3 SiCN, and KCN were developed. Direct conversion of Na 5 into K 2 was accomplished with (CH 3 ) 3 SiCN and (CH 3 ) 3 SiCl as a catalyst in an autoclave. Alternatively, Na 5 is converted into Na[BH{OC(O) R } 3 ] ( R =alkyl) that is more reactive towards (CH 3 ) 3 SiCN and thus provides an easy access to salts of 2 . Some reaction intermediates were identified, for example, Na[BH(CN){OC(O)Et} 2 ] (Na 7 b ) and Na[BH(CN) 2 {OC(O)Et}] (Na 8 b ). A third entry to 2 and 3 uses ether adducts of BHCl 2 or BH 2 Cl such as the commercial 1,4‐dioxane adducts that react with KCN and (CH 3 ) 3 SiCN. Alkali metal salts of 2 and 3 are convenient starting materials for organic salts, especially for low viscosity ionic liquids (ILs). [EMIm] 3 has the lowest viscosity and highest conductivity with 10.2 mPa s and 32.6 mS cm −1 at 20 °C known for non‐protic ILs. The ILs are thermally, chemically, and electrochemically robust. These properties are crucial for applications in electrochemical devices, for example, dye‐sensitized solar cells (Grätzel cells).

Bischoff, Lisa A.↗
DOE OSTI2019

Viscosities and working region predictions for bismuth aluminoborosilicate glasses

Bismuth aluminoborosilicate glasses were prepared using a standard melt-quench technique, and the viscosity and thermal properties were measured and analyzed. Electron microprobe analysis was used to examine glass homogeneity. Fragility was calculated based on Mauro–Yue–Ellison–Gupta–Allan model fits to the viscosity curves. The system is characterized by an open structure with high fragility (44-59). Based on microanalysis and differential scanning calorimetry results, the addition of network intermediate Al2O3 appears to mitigate both phase separation and crystallization. From thermal property data, mixture models were created to predict the glass transition temperatures and softening temperatures as functions of composition. Based on K-fold validation findings, the first-order mixture model predictions of glass transition and softening appear to approximate actual values better than models with any additional second-order terms.

Gardner, Levi↗
NASA NTRS1992

A new mechanism for viscosity in cloudy accretion disks - Anomalous (turbulent) viscosity

We analyze the dynamics of a rotating cloudy gaseous medium relative to 2D perturbations having wavelengths shorter than the disk thickness. The viscosity due to cloud-cloud collisions is confronted with the derived critical viscosity, below which a collective mode of perturbations in the disk is able to grow until going into the saturation regime where fully developed turbulence is established. It is shown that for the assumed parameters of AGN accretion disks consistent with the observational data, the viscosity due to collective modes usually dominates over that due to cloud-cloud collisions.

Fridman, Aleksei↗
DOE OSTI2019

Sensitivity of Viscosity on Molten Ti Infusion into a B{sub 4}C-Packed Bed at the Microscale

The effect of the surface tension–viscosity dissipation driving liquid Ti flow into a B{sub 4}C packed bed was analyzed at 1941 K and 2573 K. The model consisted of randomized size distributions of pores (1 to 10 µm) mimicking a packed bed to determine the depth of infusion. Statistical uncertainty was determined as a function of viscosity and pore geometry. The computations were performed with our in-house software, which incorporates a directed acyclic graph and modified nodal analysis algorithms.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Acoustic scaling of linear and mode-coupled anisotropic flow; implications for precision extraction of the specific shear viscosity

The n th -order linear flow coefficients v n L ( n = 2 , 3 , 4 , 5 ) , and the corresponding nonlinear mode-coupled ( mc ) coefficients v 4 , ( 2 , 2 ) mc , v 5 , ( 2 , 3 ) mc , v 6 , ( 3 , 3 ) mc , and v 6 , ( 2 , 2 , 2 ) mc , are studied for Pb+Pb collisions at s N N = 2.76 TeV. Both sets of coefficients suggest a common acoustic scaling pattern of exponential viscous modulation, with a rate proportional to the square of the harmonic numbers and the mean transverse momenta (respectively), and inversely proportional to the cube root of the charged particle multiplicity [ ( N ch ) 1 / 3 ] , which characterizes the dimensionless size of the systems produced in the collisions. These patterns and their associated scaling parameters offer new stringent constraints for eccentricity-independent estimates of the specific shear viscosity η s ( T ) and the viscous correction to the thermal distribution function for the matter produced in the collisions. They also give crucial constraints for extraction of the initial-state eccentricity spectrum.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗