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We present a short overview of recent investigations of the equilibrium tilt angle profile in a cell limited by two concentric cylinders filled with nematic liquid crystals (NLC), both in presence ...

Numerical solutions are presented for mixed convection in rotating concentric cylinders with a porous sleeve. The porous sleeve is press fitted to the inner surface of the outer cylinder. Whereas t...

Nutrition is one of the most important factors that ensure normal child growth and development. In Kyrgyzstan there are about 160,298 children younger than 1 years of age, for whom special baby food is needed and this need is provided only by expensive imported products. The purpose of the study is to develop recipes and technology of new fruit and vegetable purees for baby food using local raw materials; determination of the basic physicochemical parameters of a new product. As objects of research were selected apple, pear, pumpkin, potatoes. Rheological properties were obtained by shear rate scan tests in a rotational rheometer, with geometry of concentric cylinders in temperatures of 25, 35, 45°C. The thixotropy analysis was made through the calculation of the difference between the areas under up and down cycles' flow curves. In order to describe the rheological behavior of beverage, the flow curves were modeled using equations such as Herschel-Bulkley, Casson, and Ostwald-De-Waele. Based on the values of correlation coefficients and variance of the estimated parameters, Ostwald-De-Waele model was chosen for fitting of experimental data. A special feature of new recipes is the use of uzgen rice (local variety of rice) flour and honey. These ingredients give purees the texture and consitency required for children. Developed canned food due to the balanced content of carbohydrates and organic acids have good sensory properties. The content of carotenoids (pro vitamin A) is 0.4 mg%, which provides a daily rate. All designed purees are recommended as a breakfast purees for babies from 6 to 24 months.

The steady-state magnetohydrodynamics (MHD) flow of a third-grade fluid with a variable viscosity parameter between concentric cylinders (annular pipe) with heat transfer is examined. The temperature of annular pipes is assumed to be higher than the temperature of the fluid. Three types of viscosity models were used, i.e., the constant viscosity model, space dependent viscosity model and the Reynolds viscosity model which is dependent on temperature in an exponential manner. Approximate analytical solutions are presented by using the perturbation technique. The variation of velocity and temperature profile in the fluid is analytically calculated. In addition, equations of motion are solved numerically. The numerical solutions obtained are compared with analytical solutions. Thus, the validity intervals of the analytical solutions are determined.

The paper urges to investigate the enhanced viscous behavior and the heat transfer phenomenon of the unsteady ionic-nano-liquid squeezing flow between the two infinite parallel concentric cylinders. The physical scenario is transformed into a partial differential equation system by the modified Navier stokes equation, the Poisson equation, the Nernst-Plank equations, and the energy equation. The PDE’s system is transformed into the coupled ODE’s system by opting for suitable/applicable transformation. The solution of the coupled differential equations system is carried out by the Parametric continuation method (PCM)and BVP4c Matlab based methods. The effect of the squeeze number, the nanoparticle volume fraction, the Prandtl number, Schmidt number, and the heat source parameter on nano-ionic liquid flow, heat transfer rate, and other physical variables are tabulated, graphed, and discussed. The analysis of the Nusselt number for Cu-water, Al2O3-water, and TiO2- water in response to the Prandtl number(Pr), the Squeeze number(S), and the heat source parameter(Hs) concludes that the Cu-nanoparticle is the best choice for the heat transfer function through the contracting flow channel with the increasing heat transfer parameter(Hs). It is also noticed that the thermal boundary layer tends to decrease for the increasing Prandtl number(Pr) in Cu-water, Al2O3-water, and TiO2-water, which indicates that the convection mode of heat transfer is not efficient in this whole flow set-up. Applications of this study involved in the demands to understand the interfacial electrokinetic phenomena in the liquid transport processes which increase significantly as various Micro-Electro-Mechanical Systems (MEMS) and MicroFluidic devices involve liquid transport processes.

This paper concerns the structural stability of smooth cylindrically symmetric transonic flows in a concentric cylinder. Both cylindrical and axi-symmetric perturbations are considered. The governing system here is of mixed elliptic-hyperbolic and changes type and the suitable formulation of boundary conditions at the boundaries is of great importance. First, we establish the existence and uniqueness of smooth cylindrical transonic spiral solutions with nonzero angular velocity and vorticity which are close to the background transonic flow with small perturbations of the Bernoulli's function and the entropy at the outer cylinder and the flow angles at both the inner and outer cylinders independent of the symmetric axis, and it is shown that in this case, the sonic points of the flow are nonexceptional and noncharacteristically degenerate, and form a cylindrical surface. Second, we also prove the existence and uniqueness of axi-symmetric smooth transonic rotational flows which are adjacent to the background transonic flow, whose sonic points form an axi-symmetric surface. The key elements in our analysis are to utilize the deformation-curl decomposition for the steady Euler system introduced in \cite{WengXin19} to deal with the hyperbolicity in subsonic regions and to find an appropriate multiplier for the linearized second order mixed type equations which are crucial to identify the suitable boundary conditions and to yield the important basic energy estimates., 39 pages

A multi-scale analytical methodology is presented for the prediction of the mechanical properties of 3D-printed materials with continuous fibres constructed with the fused filament fabrication (FFF) technique. Initially, in micro-scale, the properties of the individual printed filaments are evaluated using different micro-models. Next, in meso-scale, the effect of voids is taken into account. Apart from the already existent models, a new concentric cylinder approach is presented for the evaluation of the effect of voids for when a transversely isotropic matrix is considered. Finally, the macro-scale properties are approximated by combining plies with different orientations using classical laminate theory (CLT). The methodology is then validated with previously and newly extracted data from numerous experiments.

This paper investigates the flow field distribution and heat transfer characteristics of turbulent flow between concentric cylinders with slit wall in the outer cylinder. The slit wall cross sections are triangle, rectangle and trapezoid respectively. The governing equations are established by the PANS model which is modified from the standard k - e model. The rotating Reynolds number ranges from 2336 to 4682 and axial Reynolds number ranges from 161 to 645, the influence of slit wall cross section on the formation and intensity of small vortex in slit region is analyzed. The results show that the slit wall geometry has a significant influence on the flow field distribution and its heat transfer process, the main vortex in annular region and small scale vortex in slit region has a tendency to merge together in the model with trapezoid cross section, resulting in more intense mixing of fluid with different temperature, therefore, the slit model with trapezoid cross section shows the best heat transfer performance among three models. The present analysis results may be applied for the structural design and optimization of many related rotating machinery.

Packed beds of spheres are simulated through discrete element method in cylinders with different geometric configurations of internal walls to evaluate their effects on bed porosity. Numerical simulations are validated using well-known literature data. Three containing systems, namely concentric cylinders, angular walls, and a combination of both, are generated. The resulting bulk porosities and porosity profiles of the sphere beds are analyzed. The increase in porosity is proportional to the incorporated wall support, that is, the combination of cylindrical and angular inserts displays the greatest effect. The sinusoidal porosity values near the inserted walls are exhibited. In conclusion, the obtained behaviors and profiles can be used to explore additional effects and further systems.

Understanding the elastic properties of 2D triaxially braided composites (2DTBCs) is fundamental for further analysis and design of structural components made from 2DTBCs. Based on a concentric cylinder model (CCM) and the rule of mixture (RoM), we reformulated the global stiffness of 2DTBCs for the anisotropic carbon fiber reinforcement to replace the currently available formulations for the isotropic glass fiber reinforcement with a replacement scheme. First, the global stiffness calculated from CCM, Quek's model and Shokrieh's model was compared for clarification. It was found that Shokrieh's model had the relatively worse performance under the same conditions. Second, the performances of Shokrieh's model, CCM, Quek's model and CCM+RoM (Reuss-type and Voigt-type) were compared using available experiments under various braiding configurations and our experiments on the hybrid carbon/glass fiber reinforced 2DTBCs, which revealed that Quek's model and CCM+RoM (Reuss-type) could yield equivalently great results, and CCM+RoM (Reuss-type) performed even better in some cases.

Drilling fluids and well cements are example non-Newtonian fluids that are used for geothermal and petroleum well construction. Measurement of the non-Newtonian fluid viscosities are normally performed using a concentric cylinder Couette geometry, where one of the cylinders rotates at a controlled speed or under a controlled torque. In this paper we address Couette flow of yield stress shear thinning fluids in concentric cylinder geometries.We focus on typical oilfield viscometers and discuss effects of yield stress and shear thinning on fluid yielding at low viscometer rotational speeds and errors caused by the Newtonian shear rate assumption. We relate these errors to possible implications for typical wellbore flows. Drilling fluids and well cements are example non-Newtonian fluids that are used for geothermal and petroleum well construction. Measurement of the non-Newtonian fluid viscosities are normally performed using a concentric cylinder Couette geometry, where one of the cylinders rotates at a controlled speed or under a controlled torque. In this paper we address Couette flow of yield stress shear thinning fluids in concentric cylinder geometries.We focus on typical oilfield viscometers and discuss effects of yield stress and shear thinning on fluid yielding at low viscometer rotational speeds and errors caused by the Newtonian shear rate assumption. We relate these errors to possible implications for typical wellbore flows.

A study is made of the hydrodynamic stability of Poiseuille and Couette flows of nanofluids in the channel formed by concentric cylinders. The influence of the concentration and size of silica nanoparticles in ethylene glycol on stability characteristics is considered. The concentrations of the nanoparticles ranges from 0 to 5%, and their size, from 10 to 210 nm. Neutral-stability curves have been constructed; the most unstable modes of perturbations have been found, and their increments have been studied. It has been shown that the action of the nanoparticles is destabilizing in all cases. The higher the concentration of the nanoparticles and the smaller the size of them, the larger the degree of this destabilization. Here, the critical Reynolds numbers decrease substantially and the spectrum of unstable perturbations changes.

This paper presents an experimental and theoretical study of CFRP-confined concrete-filled circular steel tube (CFT) stub columns, which aims at investigating the effects of different numbers of CFRP layers and concrete strengths on the mechanical performance of CFRP-confined CFT stub columns. Based on continuum mechanics, a mechanical model of concentric cylinder consisting of CFRP, circular steel tube and concrete core under concentric loading was established and the corresponding elasto-plastic methods were obtained through a FORTRAN program. The influence of the number of CFRP layers on the ultimatecapacity, ductility and confinement effect of the steel tube on the core concrete wasdiscussed and identified. Finally,based on the limit equilibrium and elasto-plastic methods, a simplified formula for the ultimatecapacity of CFRP-confined CFT stub columns was proposed. Good agreement of the ultimate capacity was found between the elasto-plastic methods and the proposed formula, with the maximum discrepancy less than 12%.

A four-phase concentric cylinder model with interface effect is proposed. Based on the model and surface/interface theory, a generalized self-consistent method is developed for predicting the effective transverse thermal conductivity of nano coated fiber composites . An analytical solution is obtained for effective thermal conductivity by applying complex elastic theory. Comparisons with the finite element analysis (FEA) and other available theoretical methods show the efficiency and the accuracy of the present method. Numerical results show the dependence of the effective thermal conductivity of the nano composites when the size of fiber and coating are on the order of nanometer . The effects of the interface thermal constant and the coating thermal conductivity on the effective thermal conductivity are discussed. The present solutions are useful to the theoretical research and engineering applications of the nano coated fiber composites.

This paper investigates the impact of asymmetric heating or cooling of cylinder surfaces on transient natural convection flow in between vertical concentric cylinders. The outer surface of inner cylinder is assumed to be heated with temperature greater than the cooled inner surface of the outer cylinder. Closed form expressions are obtained by using the well-known Laplace transform technique to solve the governing partial differential equations in Laplace domain, whereas the Riemann-sum approximation is used to invert to time domain. Results show that the role of buoyancy force distribution parameter is to increase temperature, velocity, skin-friction and volume flow rate for both air and water. Further, reverse flow formation can be controlled by using suitable buoyancy force distribution parameter.

Rubber particles can become compressed during testing of asphalt binders modified with crumb rubber (CR) in dynamic shear rheometer (DSR) parallel-plate geometry. This is especially true at...

Yield stress materials have a wide range of commercial applications. Yet, the suitable way of determining the yield stress values of a given material has been the subject of many studies and debates. Yield stresses are dependent on the material (shear) history and composition, which implies that robust protocols should be developed to study the yield stress dependence on a given parameter. In this study, three natural mud samples from a port having different densities were chosen for analysis. Four different geometries including concentric cylinders (Couette), cone and plate, parallel plates, and vane geometries were used. Our aim was to find the geometry and measurement protocol that best adapted to natural mud samples: the measurement should be reasonably fast and the major changes in sample structure (two-step yielding) should be recorded within the same measurement. Various rheological experiments such as stress sweep, oscillatory amplitude sweep, creep and stress growth tests were tested. Two-step yielding behavior was observed for the mud samples in stress sweep and amplitude sweep tests. The first yield point was linked with the breakage of interconnected network of aggregates/flocs while the second one was attributed to the collapse of aggregates into the smaller flocs or individual particles. Stress sweep tests proved to be practical, time efficient, and reliable tests for measuring yield stress values. Our study showed that Couette and parallel plate geometries are the most suitable geometries for analyzing the two yield stresses of the samples. Vane geometry is appropriate to study consolidated (solid-like) systems as for these samples a Couette geometry cannot be used because the bob could get stuck during the experiment.

The micro-electrodes of a pair of concentric cylinders have been designed to estimate the local cell configuration in biological tissues. The micro-electrodes consist with the outer and the inner concentric cylindrical needles of stainless-steel: the diameters of the outer and the inner cylindrical needles are 1.20 mm and 0.60 mm, respectively. The electrodes were inserted into the several types of the normal bovine tissues: the heart, the lever, the kidney, the fatty tissue, or the intestinal mucous membrane, alternatively. The electric voltage between electrodes was measured, while the sinusoidal alternating electric current at the frequency between 1 Hz to 1 MHz flew between the electrodes. The cell density in the tissue was counted at the microscopic image of each tissue. The results show that the capacity component increases with the density of cells. The study demonstrates the designed system of the measurement is effective to estimate the local cell configuration in biological tissues.

In this study, some structure-sensitive thermophysical properties, namely, electrical conductivity, thermal conductivity and thermoelectric power of liquid binary alloys Al33.3Mg66.7, Mg47.6Zn52.4 and Mg33.3Zn66.7 (all in wt.%), as the most promising cast alloys to fabricate components for cars, aircraft and other complex engineering products, were investigated. The electrical conductivity and thermoelectric power were measured in a wide temperature range by the four-point contact method. The thermal conductivity was measured by the steady-state concentric cylinder method. The obtained results are compared with literature experimental and calculated data.

A new, canonical configuration is proposed in this work, combining in a single setup the main features of external flows (flow around a cylinder) as well as of internal flows (flow between two concentric cylinders in rotation). This flexible configuration allows parametric investigations of combined transport processes involving both external ( Re ∞ ) and internal ( Re 0 ) flows, as they are found in many technical devices, for instance in electric machines. The present paper first describes and analyzes entropy generation in this canonical configuration numerically for a constant wall heat flux and fixed cylinder ( Re 0 = 0), in order to check if the entropic concept can be used to assess and improve industrially relevant designs. A thermal optimization of the configuration is performed to compare the changes observed between initial and optimized design. Based on this, it is shown that the Second Law Analysis (SLA) can be used to find regions where heat transfer could be intensified. The irreversibility distribution ϕ comparing entropy generation due to dissipation and due to conduction is found to be a promising indicator to detect regions with a high potential for improving heat transfer in technical devices.

Taper angle is one of the effective methods to reduce the dragload and downdrag of piles under the surcharge load. The model tests on the tapered pile and uniform cross-section pile embedded in sand were carried out under the surcharge load. The values of dragload and downdrag of piles versus the surcharge loads were measured. Based on the concentric cylinder shearing theory, a simplified theoretical model for calculating the dragload and downdrag of tapered piles with small taper angles under the surcharge load was proposed considering the angle effect. The correctness of the developed theoretical model was validated through comparing with the model test results obtained in this study and previous literature. Then the parametric studies of the taper angle, surcharge, strength and modulus of soil were discussed. It is shown that the tapered pile with the taper angle of 3° can reduce approximately 65% of the maximum dragload value and 30% of the downdrag value compared with a uniform cross-section pile. The value of downdrag can be decreased by approximately 50% compared with a uniform cross-section pile in the same average pile diameter.

The occurrence of shear-banding in wormlike micelle solutions has been observed by the birefringence distribution, velocity distribution, and other techniques. In the observation method of the birefringence distribution, however, the birefringence distribution is not enough to understand the banding structure and to examine the micelles' condition such as the generation of the shear-induced structure (SIS) but the orientation distribution is also required. In this study, a new technique to evaluate the distribution of the birefringence, the orientation angle, and the stress-optical coefficient along the radial direction was developed for this purpose. The stress optical coefficient is used as a key factor to recognize the micelles' structure, and the micelle condition in each band is examined. The visualized image by the crossed-Nicol method was precisely quantified by the new image analysis technique using the Hue value as color information. The radial distribution of the orientation angle was evaluated by the extinction position as a function of the distance from the inner wall that was quantified from the dark area shape in the whole circumferences observation image of the concentric cylinder flow. The distribution and the transient behavior of the stress-optical coefficient were calculated based on these results. The shape of the shear-banding visualized by the crossed-Nicol method coincides with the distribution of the stress-optical coefficient, and the SIS is generated only in the inner band. During the temporal stress oscillation phenomenon, the band thickness does not change, but the stress-optical coefficient of the inner SIS-band is synchronized with the stress oscillation in the opposite phase.

The assessment of uncertainty in free release measurements by integral gamma scanning method is described and applied to the measurement of homogeneous and heterogeneous waste drums. It is based on the propagation of distributions using the Monte Carlo method. In addition, two techniques for the uncertainty reduction are also described. The first technique makes use of containers constructed from two concentric cylinders and the second technique is based on the measurement of a group of waste drums. It is proved that the uncertainty of clearance measurements can be reduced using both techniques.

Whether Jupiter rotates as a solid body or has some element of differential rotation along concentric cylinders is unknown. But Jupiter’s zonal wind is not north/south symmetric so at most some average of the north/south zonal winds could be an expression of cylinders. Here we explore the signature in the gravitational moments of such a smooth differential rotation. We carry out this investigation with two general methods for solving for the interior structure of a differentially rotating planet: the CMS method of Hubbard (Hubbard, W.B. [2013]. Astrophys. J. 768, 1–8) and the CLC method of Wisdom (Wisdom, J. [1996]. Non-Perturbative Hydrostatic Equilibrium. http://web.mit.edu/wisdom/www/interior.pdf ). The two methods are in remarkable agreement. We find that for smooth differential rotation the moments do not level off as they do for strong differential rotation.

The use of recirculating aquaculture systems (RAS) permits the production of fish with a small amount of water and they are an alternative to the scarcity and pollution of water resources. The implementation of an annular settler made by concentric cylinder in an RAS tank allowed the optimal growth conditions of the fish and improves the removal of solids naturally with the presence of low water velocities in the sedimentation zone. The hydrodynamic analysis conducted in this study using computational fluid dynamics allowed the evaluation of different parameters for the geometric design of the settler and its effect on the velocity flow fields that directly affect the particle sedimentation process. Through the evaluation of different geometric configurations of the settler, the use of gratings in the perimeter of the settler with maximum height hr = 1/6h, width and separation of 0.5hr, for tank diameter (D) to water depth (h) ratios (D/h) less than 6 was established. These conditions produced velocities between 15−25 cm/s into the cultivation zone, optimal for fish growth. In addition, with the perimetral gratings, velocities less than 2 cm/s are generated inside the settler, situation that benefits the settling of particles and self-cleaning of the tank.

We consider a macroscopic description of the mutual influence between heat flux and vortex polarization in superfluid helium, in which the vortices produce a lateral deviation of the heat flux, and the heat flux produces a lateral drift of vortices. This coupling is a consequence of a microscopic Magnus force and mutual friction force between the vortices and the flow of excitations carrying the heat. We keep track of these effects with simplified macroscopic equations, and we apply them to second sound propagation between rotating concentric cylinders and to spatial distribution of polarization across a rectangular channel with vortices polarized orthogonally to the channel in the presence of an imposed heat flux.

The efficiency of strain-mediated magnetoelectric composites is heavily reliant on the effectiveness of strain transfer between the different constituents. Many analytical and experimental studies have trialed various materials, geometries, and boundary conditions reporting the effect of these attributes on the magnetoelectric response. However, a more sophisticated, but not yet pursued, approach is to investigate the strain distribution in order to discern the factors that are most influential and to provide insight on how these factors should be manipulated to optimize the coupling efficacy. In this study, a mathematical model is developed to observe the radial and tangential strains in a concentric cylinder composite structure consisting of a piezoelectric outer layer bonded with a thin elastic layer to an inner piezomagnetic layer. Results from the study elucidate that the strain distribution behavior was dependent on the mechanical properties of the constituents as well as the bonding condition. Remarkably, analytical results showed that the direct magnetoelectric coefficient can be substantially enhanced, if probing takes place at strategic locations, i.e. , leveraging strain localization, on the piezoelectric layer that maximize the difference between the radial displacements giving rise to higher magnetoelectric response.

The experimental study aims to develop and enhance the performance of tubular still under Egyptian conditions in order to overcome a problem of freshwater shortage in remote areas. This is done through the development of the design of the tubular solar stills through a modification in the design of the absorbent surface to be in the form of half two concentric cylinders containing hybrid storage materials and also added CPC in order to raise the intensity of solar radiation absorbed. To demonstrate the influences of the above modification on the performance of tubular solar still. The traditional tubular still and developed tubular still with hybrid store materials and CPC was designed, implemented and tested in the city of Tanta, Gharbia Governorate, Egypt during the period from July to August 2019 starting from 9:00 am to 9:00 pm. The experimental results presented the accumulated productivity ranges between 5.79–5.94 and 9.56–9.81 lm−2 for conventional tubular and developed tubular stills, respectively. Also, a daily efficiency ranges between 37.2–38.1 and 44.2–45.3%, for conventional tubular still and developed tubular still, respectively. Improvement in the accumulated production and daily efficiency of developed tubular still ranges between 65.1–65.4 and 18.9–19.1% respectively compared to a traditional tubular still.

Evaluar los comportamientos reológicos: tixotropía, esfuerzo umbral y caracterización al flujo; analizándose asimismo, el efecto de la temperatura y la concentración de sólidos sobre el índice de consistencia y de comportamiento al flujo, utilizando viscosímetro del tipo de cilindros concéntricos mediante la metodología propuesta por AOAC.Los niveles de concentración de sólidos solubles y temperaturas de tratamiento térmico considerados en este estudio fueron; entre 16 a 18 °Brix procesada a 80, 85, 90, 95 y 98°C, y 28 °Brix procesada a 5, 15, 25,35, 45,55, 65 y 75°C.En la pulpa simple no se observó comportamiento tixotrópico y tiene comportamiento relativo al de un fluido pseudoplástico del tipo Herschel-Bulkley; en tanto que la concentrada a 28°Brix si tiene comportamiento tixotrópico y un ajuste adecuado al de un fluidopseudoplástico del tipo Herschel-Bulkley. Los índices de consistencia y de comportamiento al flujo tanto de la pulpa simple como el de la concentrada se ubicaron respectivamente, enlos límites siguientes: 2.07±0.76 ≤ k ≤ 3.92±0.46 (Pa-sⁿ); 0.27 ≤ n ≤ 0.35; 0.71±1.64 ≤ 6° ≤ 60.11±5.23 (Pa); 14.7±1.25 ≤ k ≤ 94.22±4.84 (Pa-sⁿ); 0.201±0.007 ≤ n ≤ 0.352±0.014. El esfuerzo umbral e índice de consistencia decrecieron con la concentración de sólidos, en tanto que la temperatura ejerce mayor efecto sobre el índice de consistencia a medida que la concentración de sólidos se incrementa. Evaluate the rheological behavior: thixotropy, yield stress and flow characterization; also analyzed the effect of temperature and concentration on the rate of solid consistency and flow behavior, type viscometer using concentric cylinders through the methodology proposed by AOAC.The levels of soluble solids and heat treatment temperatures were considered in this study; between 16 to 18 ° Brixprocessed 80, 85, 90, 95 and 98 ° C and 28 ° Brix processed at 5, 15, 25, 35, 45, 55, 65 and 75 ° C. In simple pulp thixotropic behavior is not observed and has on the behavior of pseudoplastic fluid Herschel-Bulkley type; while concentrated to 28 ° Brix has thixotropic behavior and if appropriate adjustment of pseudoplastic Herschel-Bulkley fluid type. Rates consistency and flow behavior both simple pulp such as concentrated were placed respectively in the following limits: ± 2.07 0.76 ± 3.92 ≤ k ≤ 0.46 (Pa-sn); 0.27 ≤ n ≤ 0.35; 0.71 ± 1.64 ≤ 6° ≤60.11 ± 5.23 (Pa); 14.7 ≤ k ≤ ± 1.25 94.22 ± 4.84 (Pa-sn); 0.201 ± 0.007 < n < 0.352 ± 0.014. The threshold stress and consistency index decreased with the concentration of solids, while temperature has greater effect on the consistency index as the solids concentration increases.

Viscosity has been determined during isothermal crystallization of an andesite from Tungurahua volcano (Ecuador). Viscosity was continuously recorded using the concentric cylinder method and employing a Pt‐sheathed alumina spindle at 1 bar and from 1400°C to subliquidus temperatures to track rheological changes during crystallization. The disposable spindle was not extracted from the sample but rather left in the sample during quenching thus preserving an undisturbed textural configuration of the crystals. The inspection of products quenched during the crystallization process reveals evidence for heterogeneous crystal nucleation at the spindle and near the crucible wall, as well as crystal alignment in the flow field. At the end of the crystallization, defined when viscosity is constant, plagioclase is homogeneously distributed throughout the crucible (with the single exception of experiment performed at the lowest temperature). In this experiments, the crystallization kinetics appear to be strongly affected by the stirring conditions of the viscosity determinations. A TTT (Time‐Temperature‐Transformation) diagram illustrating the crystallization “nose” for this andesite under stirring conditions and at ambient pressure has been constructed. We further note that at a given crystal content and distribution, the high aspect ratio of the acicular plagioclase yields a shear‐thinning rheology at crystal contents as low as 13 vol %, and that the relative viscosity is higher than predicted from existing viscosity models. These viscosity experiments hold the potential for delivering insights into the relative influences of the cooling path, undercooling, and deformation on crystallization kinetics and resultant crystal morphologies, as well as their impact on magmatic viscosity., Key Points: Viscosity determination at subliquidus temperatures of an andesitic sampleUse of disposable Pt‐sheathed alumina spindlesDescription of viscosity and crystallization kinetics under constant stirring