Showing papers on "Viscometer published in 1971"

Rheology of concentrated suspensions

Abstract: The dependence of the viscosities of highly concentrated suspensions on solids concentrations and particle size distributions is investigated by using an orifice viscometer. Based on the extensive amount of data on pertinent systems, an empirical equation which correlates the relative viscosities of suspensions (or relative moduli of filled polymeric materials) as a function of solids concentrations and particle size distributions is proposed. The equation has a constant which characterizes size distributions of spherical particles and can be determined experimentally without measuring viscosities. For uniform-size spherical particles, it reduces to the well-known Einstein equation at dilute solids concentrations.

Reference values of the viscosity of twelve gases at 25°C

Abstract: The paper reports reference values of the viscosity of twelve gases (H2, CH4, CO, C2H4, C2H6, O2, CO2, C3H8, C4H10, SO2, CF4, SF6) at 25°C obtained in an oscillating-disc viscometer. As measured by long-range reproducibility, the precision is ±0.04 %, whereas the accuracy is estimated to be ±0.1 %. The paper also lists linear temperature corrections for viscosity at 25°C with an uncertainly of ±2.5 %.

The viscosity of liquid helium 3

Abstract: A vibrating wire viscometer cooled by a 3he dilution refrigerator has been used to measure the viscosity of liquid 3he over the temperature range 0.05 k to 3.0 k. Over the whole range the results fit the empirical formula zeta=2.21/t2+26.3/t1/3 mup. From 0.05 k to 0.10 k, (zeta t2)-1 decreases by 12.8 +or- 1.5% ; this result is discussed in the light of fermi liquid theory. Preliminary measurements of the viscosity of a saturated solution of 3he in liquid 4he from 0.05 k to 0.13 k are also reported and found to yield relaxation times in fair agreement with the theory of baym and ebner (1967).

Interfacial shear viscosity at fluid-fluid interfaces

Abstract: Fluid-fluid interfaces containing surface-active agents or macromolecules exhibit interfacial shear viscosity phenomena. The purpose of this paper is to investigate theoretically the dynamics of liquid-liquid and liquid-gas interfaces containing surfactants, and to establish the validity of the proposed model from shear flow data at uncontaminated interfaces. A theoretical analysis for the measurement of interfacial shear viscosity at liquid-liquid interfaces with an improved viscous traction surface viscometer is presented. The analysis takes into account the finite depths of the two liquids and permits interpretation of the experimental results in terms of interfacial shear viscosities at the liquid-gas interface in addition to the liquid-liquid interface. Results of the present analysis clearly show a strong coupling of interfacial and bulk fluid flows. Extensive measurements of the interfacial velocities at a xylene-water interface were made. A cetane-water interface was also studied. Interfacial flow data for uncontaminated systems were found to be in excellent agreement with theory.

Determination of the pressure coefficient and pressure effects in capillary flow

Abstract: General expressions for determining the pressure coefficient and axial distribution of the viscosity and pressure in capillary flow are derived for Newtonian and shear-thinning fluids. The pressure-dependent viscosity model is obtained from the WLF equation as derived from Doolittle's free volume theory. The model has also been derived from Eyring's hole theory for viscosity. Poiseuille's equation is modified to correct for the pressure effect on viscosity. A Newtonian, low-molecular-weight polystyrene and a shear-thinning, high-molecular-weight polystyrene were tested in an Instron capillary rheometer. The axial velocity distribution was found to be negligibly affected by pressure whereas the viscosity was shown to increase markedly with a decrease in volume. The resulting pressure effects on the viscosity of both samples were analyzed by using the derived expressions.

Tracer Diffusion and Shear Viscosity for the System Isobutyric Acid–Water near the Critical Mixing Point

Abstract: Tracer diffusion coefficients of 14C isobutyric acid in mixtures of isobutyric acid–water have been measured over the entire concentration range at e = 3.9 × 10−4 above the critical point using the diaphragm cell technique. No anomaly was detected. The temperature dependence of the shear viscosity coefficient for mixtures of critical composition was determined over the temperature range 6.7 × 10−6 < e < 2.8 × 10−2 by a closed capillary viscometer. These data were carefully analyzed in terms of a general power law equation. This analysis suggests that the excess viscosity may not diverge as the critical point is approached from the one‐phase region. Severe rounding occurs for e < 5 × 10−5.

The rheological properties of saliva

Abstract: Saliva is a complex biological fluid that cannot be effectively studied by conventional methods such as theFerranti-Shirley Viscometer. Testing with theWeissenberg Rheogoniometer shows that saliva is viscoelastic and that the dynamic viscosity falls from 400-0.1 Poise over the frequency range 2.5×10−3 to 10 Hertz. The calculated elastic contribution can be correlated with dry weight content. Dynamic viscosity and shear modulus are both reduced in storage, by proteolytic enzymes. The mucolytic agent Ascoxal also brings about a reduction in these parameters but by a different mechanism. A comparison of the results with those obtained previously for sputum, shows, that saliva may be a suitable model system for assessing mucolytic agentsin vitro.

Whole-blood viscosity, hematocrit and plasma protein in normal subjects at different ages.

Abstract: Whole-blood viscosity was measured at six fixed shear rates with a cone-plate viscometer. The 90 healthy subjects were evenly divided as to sex in three age groups from 15 to 80 years. They were selected by the criteria: normal haematocrit, erythrocyte sedimentation rate, serum creatinine concentration, and degree of intravascular erythrocyte aggregation evaluated by con-junctival biomicroscopy; and free of disease affecting known rheological properties of the blood. The viscosity was higher in males than in females. Age was not consistently related to whole-blood viscosity except that women of the oldest age group had a higher whole-blood viscosity at two isolated shear rates than women in the youngest group and the plasma fibrinogen concentration was higher in the old than in the young women. A stepwise regression analysis of rheological factors and whole-blood viscosity showed that the hematocrit had by far the closest relation to the whole-blood viscosity at all shear rates. In the order of decreasing influence were the alpha-globulins, fibrinogen, and serum albumin. There was a sex difference in that the whole-blood viscosity of men was related to the concentration of alphas-globulin, whereas in women the relation was to the alphai-globulin.

Shear Viscosity of 3‐Methylpentane—Nitroethane near the Critical Point

Abstract: Shear viscosity coefficients for a mixture of 3‐methylpentane—nitroethane of critical composition were determined over the temperature range 6×10−6≤ e ≤ 2×10−2 by an improved capillary viscometer. The data were analyzed by alternate procedures both of which give strong support to the view that the viscosity singularity is indeed very weak over a wide temperature range.

Magnetic Densimeter‐Viscometer

Abstract: A combination magnetic densimeter and viscometer, which essentially simultaneously measures the density and viscosity on 0.3 ml specimens of fluids, is described. A small cylindrical buoy is freely suspended magnetically and coaxially with a larger surrounding cylindrical glass tube which contains the fluid in which the buoy is completely immersed. After calibration, the electrical current in the air core solenoids which magnetically support the buoy measures the density of the fluid while the period of revolution at constant power input determines the viscosity. The density can be measured to the order of magnitude of one part in 106 and the viscosity to one part in 104.

Flow of dilatant (shear‐thickening) fluids

Abstract: The conduit laminar flow of dilatant (shear-thickening) fluids was investigated. It was found that such flow agreed with the Metzner-Reed (friction factor-modified Reynolds number) correlation previously verified only for pseudoplastic fluids. The agreement was found to hold even for cases where the flow behavior index was 2.0 or greater, which caused the velocity term V in the modified Reynolds number Dn′ V2−n′/gc8n−1K′ to be raised to the zero or a negative power. It was also demonstrated that conduit laminar flow for dilatant (shear-thickening) fluids could be described solely with the Metzner-Reed correlation and rheological data taken with a small-scale laboratory viscometer. Studies of flow through fittings (90-deg. elbows, globe valves, and couplings) showed a definite effect for non-Newtonian fluids contrary to previous reports for pseudoplastics which indicated essentially Newtonian behavior.

The influence of turbulent flow on the sensory assessment of viscosity in the mouth.

Abstract: Low viscosity Newtonian fluids exhibit turbulence in a cone-plate viscometer at high rates of shear which are comparable to those operating in the mouth during sensory assessment of the viscosity of the same fluids Saliva reduces this effect to some small extent, possibly due to its content of mucin and other proteinaceous substances The net result is that these fluids appear to have a higher viscosity in the mouth than when they are examined in a viscometer at low rates of shear Higher viscosity non-Newtonian food materials such as Carnation milk and ice cream do not exhibit turbulent flow, and the only effect exerted by saliva is a reduction in the viscosity at all rates of shear

A New Kind of Oscillating Crucible Viscometer

Abstract: A new oscillating crucible viscometer, having a torus shaped crucible, is presented. The geometry of the torus allows a rigorous treatment of the fluidodynamical problem for an oscillating viscous liquid. The damping coefficient δ is shown to characterize two possible distinct zones of oscillation: In the first zone, δ rises when the viscosity η of the liquid rises; in the second one, δ is lowered by an increase of η. The second zone proves to be much more convenient for fixing the working point of the instrument because here the sensitivity is expected to be twice that of the first zone. Some preliminary experiments have confirmed the results of the theory.

High Temperature Viscosity Ratios for Neon

Abstract: Capillary flow viscometry measurements were made to determine neon viscosity ratios . η(T)/η(T0). T ranges from 1100 to 2100 °K and T0 is the reference, arbitrarily taken as 283 °K. Results are higher than those of previous workers.

Continuous recording viscometer

Abstract: Disclosed is a system for automatically and continuously measuring and producing a continuous record of apparent viscosity, plastic viscosity and yield point for mud systems during a well drilling operation. Also, a continuous record of the ratio of plastic viscosity to yield point values is obtained by the system. Two viscosity determining units are synchronized relative to one another so that their outputs may be used and combined to obtain the above mentioned parameters. Each unit is comprised of a type of Fann viscometer having a sampling cup with a bottom inlet and an open top where overflow may occur. The speed of rotating cylinders in the respective sampling cups, synchronized relative to one another so that when one viscometer operates at 300 rpm the other viscometer operates at 600 rpm, and the outputs of the viscometers can be electronically combined to yield apparent viscosity, plastic viscosity and yield point, as well as the plastic viscosity-yield point ratio.

Secondary flow in a parallel-disk viscometer

Abstract: A numerical solution of theNavier-Stokes equations is obtained for flow in a parallel-disk viscometer. The inertial secondary flow consists of a single eddy which is well represented away from the free surface by the approximate analytical solution for infinite disks.

A rheogram template for power law fluids: Technique for characterizing the rheological properties of emulsions and polymer solutions

Abstract: A simple “template” method is presented which extends the usefulness of the Brookfield Synchro-Lectric viscometer, with the use of a cylindrical spindle, to meaningful characterization of non-Newtonian fluids which follow the power law. Deviation from Newtonian behavior is characterized by a single constant called the shear thinning index (STI). By the method, a well-defined shear rate can be determined for each rpm setting and corresponding apparent viscosity values can be simply and rapidly obtained. The technique has wide application for the study and characterization of emulsions and polymer solutions. It has recently been employed for determination of agglomerate—creaming tendency in silicone emulsions and in the quality control of Polyox®, poly(ethylene oxide) resins.

Precision Falling Sphere Viscometry

Abstract: Terminal velocity data of spheres falling in a polyisobutylene (PIB) solution were obtained in sealed tubes. The tubes were easily invertible so that the fall of a sphere could be repeated as often as desired. The sealed tubes have the further advantage that degradation of the fluid is greatly reduced when compared to similar experiments in open tubes. Precisely reproducible velocities were obtained by careful temperature control and by measurement of the radial eccentricity. From such data it is possible to calculate the zero‐shear viscosity, η0, provided the range of effective shear rates is sufficiently small. To acquire data in this range it is necessary to use spheres with small effective mass (actual mass less the mass of the displaced fluid). Spheres of various materials (nylon, ruby, steel, and carbide) were used, and their properties were checked by dropping them in a Newtonian fluid of known viscosity. In some cases the sphere properties were found to fall outside the tolerances specified by the...

Extrapolation procedures for zero shear viscosity with a falling sphere viscometer

Abstract: Several theoretical and empirical extrapolation procedures for the determination of zero shear viscosity in a falling sphere viscometer are critically analysed. They are experimentally tested and it is concluded that the extrapolation procedure based onCaswells work appears to be the most appropriate.

Fluid-Dynamic Consideration of Bottom Materials

Abstract: Bottom materials often involve clay-water suspensions which evidence complex rheology. Studies of the non-Newtonian behavior of kaolin are reported herein. Concentric viscometer analysis at concentrations of 5, 10 and 20% by weight indicate Bingham-plastic-body behavior; Newtonian fluid behavior is evidenced at low concentration and alkalinity. The dependence of the fluid properties, yield stress, and plastic viscosity on pH and concentration is characterized; both these properties increase with increase in concentration, or decrease in pH (increase in acidity). Measurements of the drag of simple bodies in this mixture are reported. The drag coefficient of spheres and discs in the laminar boundary-layer region (Reynolds numbers below 2 x 10 5 ) indicate negligible non-Newtonian effect above a Reynolds number of 1,000. At lower Reynolds number, a yield stress effect is superimposed. The dependence of this effect on the Hedstrom number is indicated for values of this parameter up to 4,000. The occurrences with spheres and discs are found to be much the same.

Extension of GPC Techniques

Abstract: Most of the common GPC gels exhibit pore sizes which are too small to separate very extended molecules, e.g., native cellulose in solution. Several gel types were tested with vinyl polymers of molecular weights up to 107 and with cellulose nitrate. Large pore size Styragel with acetone as solvent proved to be the most favorable gel system yielding effective separations for polymers with coil diameters in solution up to 4000 A. The evaluation of GPC runs usually requires a separate calibration procedure. We attempted to determine the molecular weight of the eluate directly as it leaves the column. This is done by a special automatic viscometer that allows measurement of the viscosity of small cuts (e.g., 0.5–1 ml) of the effluent volume. A set of six capillary viscometers are loaded and unloaded continuously. The details of the apparatus are described and examples of the performance reported.

The theory of absolute surface shear viscosity. IV. The double ring couette surface viscometer

Abstract: The hydrodynamic problem of two concentric, counter rotating rings making a knife-edge contact with a viscous surface film supported by a semi-infinite, viscous substrate is discussed. Plots of interfacial velocity profiles are presented, and the relation between the torque on the outer, stationary ring and the surface viscosity is given in the form of interpolation polynomials which permit the calculation of the surface viscosity from experimental values of the torque.

Normal stress effect in dilute polymer solutions

Abstract: The non-linear, steady flow behavior of dilute solutions of poly ethylene oxide at high shear rates is experimentally studied. The shear stress-shear rate relations at low and high shear rates are obtained in capillary tube and in rotational viscometers; the expansion-contraction characteristics of jets are studied by ejecting these liquids from a small diameter capillary tube and then the viscosity and the first normal stress difference are thereby evaluated and related to viscometric functions. Several viscoelastic theories (in particular, Maxwell, Rivlin-Ericksen, and Oldroyd models) are examined for their ability to correlate the results. It is concluded that the experimental technique which has been utilized yields reasonably correct results; however, the effects of viscosity, tube diameter and degradation of polymer molecules on the final results need further study. From examination of viscoelastic theories, it is found that the non-linear theory of Oldroyd correlates the data correctly.

Kinetics of Thixotropy of Aqueous Bentonite Suspension

Abstract: The theological properties of aqueous suspensions of Black Hills bentonite were measured by using a Couette-type viscometer. Three kinds of flow units in aqueous bentonite suspension were postulated. Each has a different average relaxation time, one Newtonian. One of the non-Newtonian types is thixotropic, and the other is non-thixotropic. The thixotropic non-Newtonian unit is transformed to a Newtonian unit by shear stress. If the stress is relieved, the transformed unit returns to its original state. Two flow equations were derived by introducing chemical kinetics consideration for such a transition into the generalized theory of viscous flow. One equation describes the "upcurve," a diagram of rate of sheat versus shear stress, obtained by increasing the rate of shear, and the other relates to the "downcurve" obtained by decreasing the shear rate. The equations satisfactorilly describe the experimental thixotropic hysteresis of bentonite suspensions. The equations also were successfully applied to the flow curves of the suspensions containing various amounts of monovalent electrolyte (KCI).

Ultrasonic and Viscous Behaviour of Polymesomorphic Liquid Crystal

Abstract: The ultrasonic and viscous behaviour of cholesteryl stearate which exhibits multiple mesophase transitions is studied. The variation of ultrasonic velocity ( V ), adiabatic compressibility (β ad ), molar sound velocity ( R ), viscosity (η) and flow activation energy ( E v ) with temperature have been studied in the isotropic, cholesteric and smectic mesophases. The velocity measurements are carried out with a fixed-path double-crystal interferometer and viscosities are measured by a cone-and-plate viscometer within a narrow range of shear rate. The adiabatic compressibility shows abrupt decrease in the vicinity of the thermodynamic transitions between the smectic, cholesteric and isotropic states. The plot of log η vs (1000/ T ) exhibits changes in slopes at the smectic-cholesteric and cholesteric-isotropic transitions. The activation energy for viscous flow is computed. The ultrasonic velocity data in this liquid crystal is reported for the first time.