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Results for “Kinematic 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.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Theoretical Approach for the Fast Estimation of the Turbulent Kinematic Viscosity for Internal Flows

An analytical expression for turbulent kinematic viscosity (νt), based solely on the hydraulic Reynolds number (Re), was derived and evaluated. The analytical expression is valid for the fast estimation of νt for internal, isotropic, fully developed flows. The expression was compared with experimental and simulation data for air, water, and liquid sodium, and was shown to provide reasonable values for 2100 ≤ Re ≤ 3.6 × 106 and Prandtl number (Pr) range of 0.0107 ≤ Pr ≤ 5.65. In addition, new expressions suitable for the central portion of internal flows, away from the wall, were derived for the turbulent Reynolds number (ReT), showing its relationship to Re, as well as to the ratio of νt and the molecular kinematic viscosity (ν).

42 ENGINEERING↗
DOE OSTI2020

Predicting the Cetane Number, Yield Sooting Index, Kinematic Viscosity, and Cloud Point for Catalytically Upgraded Pyrolysis Oil Using Artificial Neural Networks

Abstract The conversion of biomass using fast pyrolysis has the potential to be significantly less expensive at scale compared to alternative methods such as fermentation and gasification. Selective upgrading of the products of fast pyrolysis through chemical catalysis produces compounds with lower oxygen content and lower acidity; however, identifying the specific catalytic pathways for producing viable fuels and fuel additives often requires a trial-and-error approach. Specifically, key properties of the compounds must be experimentally tested to evaluate the viability of the resultant compounds. The present work proposes predictive models constructed with artificial neural networks (ANNs) for cetane number (CN), yield sooting index (YSI), kinematic viscosity (KV), and cloud point (CP), with blind test set median absolute errors of 5.14 cetane units, 3.36 yield sooting index units, 0.07 millimeters squared per second, and 4.89 degrees Celsius, respectively. Furthermore, the cetane number, yield sooting index, kinematic viscosity, and cloud point were predicted for over three hundred expected products from the catalytic upgrading of pyrolysis oil. It was discovered that 130 of these compounds have predicted cetane numbers greater than 40, with four of these compounds possessing predicted yield sooting index values significantly less than that of diesel fuel and predicted viscosities and cloud points comparable to that of diesel fuel.

09 BIOMASS FUELS↗
NASA NTRS1992

Gravimetric capillary method for kinematic viscosity measurements

A novel version of the capillary method for viscosity measurements of liquids is presented. Viscosity data can be deduced in a straightforward way from mass transfer data obtained by differential weighing during the gravity-induced flow of the liquid between two cylindrical chambers. Tests of this technique with water, carbon tetrachloride, and ethanol suggest that this arrangement provides an accuracy of about +/- 1 percent. The technique facilitates operation under sealed, isothermal conditions and, thus can readily be applied to reactive and/or high vapor pressure liquids.

Rosenberger, Franz↗
NASA NTRS1992

User's Manual for Aerofcn: a FORTRAN Program to Compute Aerodynamic Parameters

The computer program AeroFcn is discussed. AeroFcn is a utility program that computes the following aerodynamic parameters: geopotential altitude, Mach number, true velocity, dynamic pressure, calibrated airspeed, equivalent airspeed, impact pressure, total pressure, total temperature, Reynolds number, speed of sound, static density, static pressure, static temperature, coefficient of dynamic viscosity, kinematic viscosity, geometric altitude, and specific energy for a standard- or a modified standard-day atmosphere using compressible flow and normal shock relations. Any two parameters that define a unique flight condition are selected, and their values are entered interactively. The remaining parameters are computed, and the solutions are stored in an output file. Multiple cases can be run, and the multiple case solutions can be stored in another output file for plotting. Parameter units, the output format, and primary constants in the atmospheric and aerodynamic equations can also be changed.

Conley, Joseph L.↗
NASA NTRS1973

A kinematic eddy viscosity model including the influence of density variations and preturbulence

A model for the kinematic eddy viscosity was developed which accounts for the turbulence produced as a result of jet interactions between adjacent streams as well as the turbulence initially present in the streams. In order to describe the turbulence contribution from jet interaction, the eddy viscosity suggested by Prandtl was adopted, and a modification was introduced to account for the effect of density variation through the mixing layer. The form of the modification was ascertained from a study of the compressible turbulent boundary layer on a flat plate. A kinematic eddy viscosity relation which corresponds to the initial turbulence contribution was derived by employing arguments used by Prandtl in his mixing length hypothesis. The resulting expression for self-preserving flow is similar to that which describes the mixing of a submerged jet. Application of the model has led to analytical predictions which are in good agreement with available turbulent mixing experimental data.

Cohen, L. S.↗
NASA NTRS1992

Lattice Boltzmann model for compressible fluids

A lattice Boltzmann model is derived which simulates compressible fluids. By choosing the parameters of the equilibrium distribution appropriately, the sound speed (which may be set arbitrarily low), bulk viscosity, and kinematic viscosity can be selected. This model simulates compressible flows and can include shocks. With a proper rescaling and zero-sound speed, this model simulates Burgers's equation. The viscosity determined by a Chapman-Enskog expansion compares well with that measured form simulations. The exact solutions of Burgers's equation on the unit circle are compared to solutions of lattice Boltzmann model finding reasonable agreement.

Alexander, F. J.↗
NASA NTRS1990

Stability and slosh wave for rotating bubble due to gravity-jitters under microgravity

Time-dependent fluid behaviors in microgravity environments are examined with particular attention given to the dynamics of bubble configurations. The initial bubble profiles, computed from the steady-state formulation, are used as the initial input for the time dependent computation. The parameters considered are liquid density and its kinematic viscosity, gas density and its kinematic viscosity, surface tension coefficient, angular velocity, and gravity environment. This computer algorithm can be used to simulate the fluid behavior in a microgravity environment, in particular the excitation of slosh waves due to different frequencies of gravity jitters. Results show that lower-frequency gravity jitters excite slosh waves with a higher ratio of maximum amplitude to wave length than that of the slosh waves generated by the higher frequency gravity jitters.

Hung, R. J.↗
NASA NTRS1932

Investigation of Damping Liquids for Aircraft Instruments : II

Data are presented on the kinematic viscosity, in the temperature range -50 degrees to +30 degrees C. of pure liquids and of solutions of animal oils, vegetable oils, mineral oils, glycerine, and ethylene glycol in various low freezing point solvents. It is shown that the thermal coefficient of kinematic viscosity as a function of the kinematic viscosity of the solutions of glycerine and ethylene glycol in alcohols is practically independent of the temperature and the chemical composition of the individual liquids. This is similarly true for the mineral oil group and, for a limited temperature interval, for the pure animal and vegetable oils. The efficiency of naphthol, hydroquinone, and diphenylamine to inhibit the change of viscosity of poppyseed and linseed oils was also investigated.

Houseman, M R↗
NASA NTRS1962

Investigation of the Damping of Liquids in Right-Circular Cylindrical Tanks, Including the Effects of a Time-Variant Liquid Depth

An experimental investigation was conducted to determine the effects of several basic variables upon the damping of the fundamental antisymmetric mode of liquids in right-circular cylindrical tanks without baffles. The variables examined include liquid depth, efflux rate, liquid amplitude, kinematic viscosity, and tank size. The data are presented in dimensionless form and compared with available theory. For the range of variables examined, variations of efflux rate and liquid amplitude were found to have no significant effects on the liquid damping. The following theoretical relationship was found to be adequate for the prediction of the variation of damping with liquid depth, kinematic viscosity, and tank size: [for equation see full text] where v is the kinematic viscosity, R is the cylinder radius, g is the acceleration due to gravity, and h is the liquid depth. However, the constant K was experimentally found in this investigation to have the value 5.23, which is 50 percent higher than the theoretically predicted value.

TANK↗
NASA NTRS1976

Excitation and relaxation of the wobble, precession, and libration of the moon

The rate of meteorite-impact excitation of the free wobble, free precession, and free libration of the moon above a given amplitude is estimated for two crater-size scaling laws and is compared with the rate of damping by tidal and rotational distortion as well as by a possible core-mantle interaction. Criteria for the probable existence and the probable nonexistence of observable amplitudes of the free motions are developed in terms of upper bounds on the damping factor for the various motions and in terms of ranges for the kinematic viscosity of a possible core. It is shown that although observable amplitudes are compatible with reasonable values of the damping factor and kinematic viscosity, other reasonable values could keep the amplitudes below the observable level most of the time. It is found that the free libration is the least likely motion to be observed and that a lunar core with earthlike properties might keep some of the free motions damped, but not all of them. Uncertainties in some of the assumptions used in the analysis are discussed.

Peale, S. J.↗
NASA NTRS1982

Properties of a constricted-tube air-flow levitator

The properties of a constricted-tube gas flow levitator first developed by Berge et al. (1981) have been investigated experimentally in order to predict its behavior in a gravity-free environment and at elevated temperatures. The levitator consists of a constricted (quartz) tube fed at one end by a source of heated air or gas. A spherical sample is positioned by the air stream on the downstream side of the constriction, where it can be melted and resolidified without touching the tube. It is shown experimentally that the kinematic viscosity is the important fluid parameter for operation in thermal equilibrium at high temperatures. If air is heated from room temperature to 1200 C, the kinematic viscosity increases by a factor of 14. To maintain a given value of the Reynolds number, the flow rate would have to be increased by the same factor for a specific geometry of tube and sample. Thus, to maintain stable equilibrium, the flow rate should be increased as the air or other gas is heated. The other stability problem discussed is associated with changes in the shape of a cylindrical sample as it melts.

Rush, J. E.↗
DOE OSTI2020

Multifunctional Tunable Polymethacrylates for Enhanced Shear Stability and Wear Prevention

This paper describes the design, synthesis, and characterization of linear, polar, and non-polar polymethacrylates designed for use as lubricant viscosity index improvers with enhanced shear and anti-wear resistance. The polymers were prepared via Reversible Addition-Fragmentation Chain Transfer (RAFT) to obtain relatively low, narrow, molecular weights, with random polar moieties. The resulting polymers were evaluated as oil solutions to determine their viscosity index, shear stability performance, and antiwear characteristics. The polymers had molecular weights (Mw) ranging from 120-170 kDa, and the resulting viscosity indexes (VIs) in general tracked the Mw. Although the VIs were modest (140-189), all polymers displayed higher values than a commercial product designed for similar applications, both at 2% (w/w) and when kinematic viscosities (KVs) were normalized to the lowest KV100 of ~5cSt. One of the imidazole-containing polymers displayed an anomalously high VI for a low apparent Mw. As hypothesized, many of the polar polymers demonstrated substantial wear reduction compared to the non-polar homopolymers or a commercial benchmark. The low-molecular-weight imidazole-containing polymer produced less than 4% of the wear displayed by the commercial standard. The higher molecular weight polymers containing imidazole, hydroxy group and amino group also produced as little as 10% of the wear shown by the benchmark. The strategy demonstrated the benefit of low, narrow, molecular weight polymers to achieve good shear stability in viscosity modifiers while minimizing wear, rendering them suitable for fluid-power applications.

friction modifiers↗
DOE OSTI2022

Computing the viscous effect in early-time drop impact dynamics

The impact of a liquid drop on a solid surface involves many intertwined physical effects, and is influenced by drop velocity, surface tension, ambient pressure and liquid viscosity, among others. Experiments by Kolinski et al. ( Phys. Rev. Lett. , vol. 112, no. 13, 2014 b , p. 134501) show that the liquid–air interface begins to deviate away from the solid surface even before contact. They found that the lift-off of the interface starts at a critical time that scales with the square root of the kinematic viscosity of the liquid. To understand this, we study the approach of a liquid drop towards a solid surface in the presence of an intervening gas layer. We take a numerical approach to solve the Navier–Stokes equations for the liquid, coupled to the compressible lubrication equations for the gas, in two dimensions. With this approach, we recover the experimentally captured early time effect of liquid viscosity on the drop impact, but our results show that lift-off time and liquid kinematic viscosity have a more complex dependence than the square-root scaling relationship. We also predict the effect of interfacial tension at the liquid–gas interface on the drop impact, showing that it mediates the lift-off behaviour.

42 ENGINEERING↗
NASA NTRS1961

An Experimental Investigation of the Damping of Liquid Oscillations in an Oblate Spheroidal Tank With and Without Baffles

An experimental investigation was conducted to determine the damping of the fundamental antisymmetric mode of oscillation of liquids contained in an oblate spheroidal tank. The decay of the fundamental mode was studied for a range of liquid depths in tanks with and without baffles. In the investigation of baffle effects, ring and cruciform baffles of various sizes were fixed at different locations within the tank. Data presented show the variation of the damping factor with tank fullness and with baffle type, width, location, and orientation as well as the effects of the amplitude of the liquid oscillations and of small variations in the liquid kinematic viscosity on the damping factor. The results of the investigation indicate that the addition of ring baffles to the tank results in an increase in the available effective damping when the baffle plane is in a region near the equilibrium liquid surface, and that cruciform baffles are effective in the damping of the fundamental mode in the near-empty tank. No apparent changes in damping for the tanks having ring baffles were observed as the kinematic viscosity of the liquid was varied over a small range.

Stephens, David G.↗
DOE OSTI2021

Evaluating Diesel/Biofuel Blends Using Artificial Neural Networks and Linear/Nonlinear Equations

Abstract The use of biomass-derived additives in diesel fuel mixtures has the potential to increase the fuel’s efficiency, decrease the formation of particulate matter during its combustion, and retain the fuel’s behavior in cold weather. To this end, identifying compounds that enable these behaviors is paramount. The present work utilizes a series of linear and non-linear equations in series with artificial neural networks to predict the cetane number, yield sooting index, kinematic viscosity, cloud point, and lower heating value of multi-component blends. Property values of pure components are predicted using artificial neural networks trained with existing experimental data, and these predictions and their expected errors are propagated through linear and non-linear equations to obtain property predictions for multi-component blends. Individual component property prediction errors, defined by blind prediction median absolute error, are 4.91 units, 7.84 units, 0.06 cSt, 4.00 °C, and 0.55 MJ/kg for cetane number, yield sooting index, kinematic viscosity, cloud point, and lower heating value respectively. On average, property predictions for blends are shown to be accurate to within 6% of the blends’ experimental values. Further, a multitude of compounds expected to be produced from catalytically upgrading products of fast pyrolysis are evaluated with respect to their behavior in diesel fuel blends.

09 BIOMASS FUELS↗
DOE OSTI2024

Atomistic Simulations for Thermophysical Properties of Uranium-Containing Halide Molten Salts

Characterizing the thermophysical properties in both fuel and coolant salts are critical in modeling, developing, process optimizing and utilizing molten salt reactors (MSRs), as these properties directly relate to operation metrics and can inform on the selection of candidate salts. The demand for consistent, accurate and publicly available thermophysical property data has become more apparent in recent years as interests have increased from molten salt reactor developers. There are a number of challenges in experimentally measuring properties such as thermal conductivity, viscosity, density and heat capacity , which have led to sparse and often times conflicting data points or molten salts in general. Additionally, there are a number of hazards to consider when synthesizing, storing, using, treating and disposing of molten salts. With the advances in computational capabilities over the last 10 years, the use of atomistic simulations can be implemented to support these efforts. The primary objective of this work is characterize the thermophysical transport properties in a number of molten chloride salts, and in particular NaCl-UCl 3 using ab-initio molecular dynamic (AIMD) simulations. In this binary salt the UCl 3 acts as the primary fissile material and NaCl acts as a carrier salt due with its’ high solubility for actinides A number of studies on the thermophysical properties of NaCl-UCl 3 have been published but there is not a vast amount of viscosity data for this system. In 1975, Desyatnik, et al published a study reporting dynamic viscosities that were calculated from kinematic viscosity measurements, and using the coefficients provided the viscosity in a 70:30 NaCl:UCl 3 mixture is 2.29 cP and 2.88 for a 60:40 mixture. Termini et al. recently reported viscosities in the range of 2.75 – 3 cP for the 63:37 NaCl-UCl 3 mixture in the same temperature range using rolling ball viscosity measurements. Computational viscosity of a similar mixture (64:36) can be obtained from the work Andersson et al. using the reported diffusion coefficients, and the hydrodynamic radius from the pair-radial distribution functions (RDFs). Using Eq (1) (vida infra), the viscosity would be 2.50 cP at 1100K. This is not to say that these values are incorrect due to the varying reported values, but aims to highlight the necessity of this work. The data reported in this ongoing work are computations on a 64:36 mixture of NaCl-UCl 3 at 987K. This work is likely to be expanded into varying concentrations of this mixture along with the inclusion of other salt candidate mixtures.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2024

Viscosity bounds in liquids with different structure and bonding types

Recently, it was realized that liquid viscosity has a lower bound which is nearly constant for all liquids and is governed by fundamental physical constants. This was supported by experimental data in noble and molecular liquids. Here, we perform large-scale molecular dynamics simulations to ascertain this bound in two other important liquid types: the ionic molten salt system LiF and metallic Pb. We find that these ionic and metallic systems similarly have lower viscosity bounds corresponding to the minimum of kinematic viscosity of ∼ 10 − 7 m 2 / s . We show that this agrees with experimental data in other systems with different structures and bonding types, including noble, molecular, metallic, and covalent liquids. This expands the universality of viscosity bounds into the main system types known. Published by the American Physical Society 2024

Materials Science↗
NASA NTRS1972

Viscosity of the earth's core

Estimates of the coefficient of kinematical viscosity nu of the earth's liquid metallic core that are given in the geophysical literature range from approximately 0.001 sq cm/s, the viscosity of molten iron at ordinary pressures, to approximately less than 10 to the 8th power sq cm/s, based on the observation that compressional waves traverse the core without suffering serious attenuation. Bumps on the core-mantle boundary with typical horizontal dimensions up to a few thousand km and vertical dimensions h of a few km would produce the topographic coupling between the core and mantle that is evidently implied by the observed decade variations in the length of the day (unless the coupling is due to the presence of rapidly fluctuating magnetic fields in the core).

Hide, R.↗