Gravity driven instabilities in miscible non-Newtonian fluid displacements in porous media
NASA Astrophysics Data System (ADS)
Freytes, V. M.; D'Onofrio, A.; Rosen, M.; Allain, C.; Hulin, J. P.
2001-02-01
Gravity driven instabilities in model porous packings of 1 mm diameter spheres are studied by comparing the broadening of the displacement front between fluids of slightly different densities in stable and unstable configurations. Water, water-glycerol and water-polymer solutions are used to vary independently viscosity and molecular diffusion and study the influence of shear-thinning properties. Both injected and displaced solutions are identical but for a different concentration of NaNO 3 salt used as an ionic tracer and to introduce the density contrast. Dispersivity in stable configuration increases with polymer concentration - as already reported for double porosity packings of porous grains. Gravity-induced instabilities are shown to develop below a same threshold Péclet number Pe for water and water-glycerol solutions of different viscosities and result in considerable increases of the dispersivity. Measured threshold Pe values decrease markedly on the contrary with polymer concentration. The quantitative analysis demonstrates that the development of the instabilities is controlled by viscosity through a characteristic gravity number G (ratio between hydrostatic and viscous pressure gradients). A single threshold value of G accounts for results obtained on Newtonian and non-Newtonian solutions.
Similarity solution for unsteady gravity-driven dry patch in a non-Newtonian fluid flow
NASA Astrophysics Data System (ADS)
Abas, Siti Sabariah; Mohd Yatim, Yazariah
2013-04-01
We consider an unsteady thin-film flow of a non-Newtonian fluid around a dry patch subject to gravitational acceleration on an inclined plane. The general governing partial differential equation is transformed into the second-order ordinary differential equation using a unique travelling-wave similarity transformation. The analysis shows that the dry patch has a parabolic shape and the film thickness was found to increase monotonically away from the dry patch. Numerical solutions of the similarity equation are obtained for the velocity of the dry patch. These numerical solutions are also compared with the asymptotic solutions in the certain limits. The effects of power-law index on the behavior and patterns of the solutions are also discussed.
NASA Astrophysics Data System (ADS)
Di Federico, V.; Longo, S.; Ciriello, V.; Chiapponi, L.
2015-12-01
A theoretical and experimental analysis of non-Newtonian gravity-driven flow in porous media with spatially variable properties is presented. The motivation for our study is the rheological complexity exhibited by several environmental contaminants (wastewater sludge, oil pollutants, waste produced by the minerals and coal industries) and remediation agents (suspensions employed to enhance the efficiency of in-situ remediation). Natural porous media are inherently heterogeneous, and this heterogeneity influences the extent and shape of the porous domain invaded by the contaminant or remediation agent. To grasp the combined effect of rheology and spatial heterogeneity, we consider: a) the release of a thin current of non-Newtonian power-law fluid into a 2-D, semi-infinite and saturated porous medium above a horizontal bed; b) perfectly stratified media, with permeability and porosity varying along the direction transverse (vertical) or parallel (horizontal) to the flow direction. This continuous variation of spatial properties is described by two additional parameters. In order to represent several possible spreading scenarios, we consider: i) instantaneous injection with constant mass; ii) continuous injection with time-variable mass; iii) instantaneous release of a mound of fluid, which can drain freely out of the formation at the origin (dipole flow). Under these assumptions, scalings for current length and thickness are derived in self similar form. An analysis of the conditions on model parameters required to avoid an unphysical or asymptotically invalid result is presented. Theoretical results are validated against multiple sets of experiments, conducted for different combinations of spreading scenarios and types of stratification. Two basic setups are employed for the experiments: I) direct flow simulation in an artificial porous medium constructed superimposing layers of glass beads of different diameter; II) a Hele-Shaw (HS) analogue made of two parallel
Experiments with large diameter gravity driven impacting liquid jets
NASA Astrophysics Data System (ADS)
Storr, G. J.; Behnia, M.
The phenomenon of a liquid jet released under gravity and falling through or impacting onto another liquid before colliding with an obstructing solid surface has been studied experimentally under isothermal conditions. Usually the jet diameter was sufficiently large to ensure jet coherency until collision. Direct flow visualization was used to study jets released into water pools with no air head space and jets impacting onto water pools after falling through an air head space. It is shown that distances predicting the onset of buoyancy and the entrainment of air using derivations from continuous plunging jets, are not applicable for impacting jets. The morphology of jet debris after collision with the solid surfaces correlates with the wetting properties of the jet liquid on the surface.
Gravity-driven instability of a thin liquid film underneath a soft solid.
Lee, S H; Maki, K L; Flath, D; Weinstein, S J; Kealey, C; Li, W; Talbot, C; Kumar, S
2014-11-01
The gravity-driven instability of a thin liquid film located underneath a soft solid material is considered. The equations and boundary conditions governing the solid deformation are systematically converted from a Lagrangian representation to an Eulerian representation, which is the natural framework for describing the liquid motion. This systematic conversion reveals that the continuity-of-velocity boundary condition at the liquid-solid interface is more complicated than has previously been assumed, even in the small-strain limit. We then make clear the conditions under which the commonly used simplified version of this boundary condition is valid. The small-strain approximation, lubrication theory, and linear stability analysis are applied to derive an expression for the growth rate of small-amplitude perturbations. Asymptotic analysis reveals that the coupling between the liquid and solid manifests itself as a lower effective liquid-air interfacial tension that leads to larger instability growth rates. Although this suggests that it is more difficult to maintain a stable liquid coating underneath a soft solid, the effect is expected to be weak for cases of practical interest.
Microfluidic rheology of non-Newtonian liquids.
Girardo, Salvatore; Cingolani, Roberto; Pisignano, Dario
2007-08-01
We investigate the rheological properties of a non-Newtonian glass-former liquid within lithographically defined microchannels in the range of temperatures above the vitrification region. The non-Newtonian behavior of the fluid, as evidenced by rotational rheology, is well described by a power law dependence of the viscosity on the shear rate. Taking into account such non-Newtonian character in the equations for the microfluidic motion, we relate the penetration dynamics into capillaries with the liquid rheological properties. The temperature dependence of the viscosity, determined over 1 order of magnitude in the temperature range 286-333 K and for shear rates between 0.07 and 1 s-1, can be described by a Vogel-Fulcher-Tamman law, consistent with the fragile nature of the investigated compound. Microfluidics is a promising analytical approach for the investigation of the rheology of non-Newtonian fluids within confined microenvironments.
NASA Astrophysics Data System (ADS)
Njifenju, A. Kevin; Bico, José; Andrès, Emmanuelle; Jenffer, P.; Fermigier, Marc
2013-05-01
A visualization technique based on light absorption is used to monitor the thickness profile of a liquid film flowing on an inclined plane with high spatial and temporal resolutions. Surface waves are observed for a certain range of experimental parameters as expected from the classical stability analysis from Benjamin (J Fluid Mech 2:554-574, 1957). The liquid films are found systematically thicker than predicted by Nusselt (Z Ver Dtsch Ing 60:541, 1916) in the case of ideal viscous flows. We interpret this increase in thickness as a consequence of the propagation of waves on the films. The wave dynamics are in qualitative agreement with the asymptotic development from Anshus (Ind Eng Chem Fundam 11:502-508, 1972). Although the wavelength distribution is rather broad, space-time analysis indicates a well-defined phase velocity. Representing the wave velocity of a corrected Reynolds number allows to superimpose the experimental data into a single master curve.
Dense, gravity-driven granular-liquid flows down steep channels
NASA Astrophysics Data System (ADS)
Armanini, A.; Larcher, M.; Nucci, E.
2011-12-01
Debris flows are complex natural phenomena, characterized by a mixture of poorly sorted sediments and water driven by gravity. Depending on the size distribution, on the volume concentration of sediments and on the geometry and topography of the channel, flow conditions may be very different, ranging from very fast flows, dominated by granular collisions and by the turbulence on the liquid phase, to very slow and dense flows, dominated by the frictional contacts among the grains. To investigate the basic physics of debris flows, it is very useful to analyze the flow of a mixture of identical spherical particles saturated by water and driven by gravity down a steep channel in steady flow condition (Armanini et al. 2005). The flow presents three regions: an external one, near to the free surface, dominated by nearly instantaneous contacts among the particles (collisional regime), an internal region dominated by prolonged contacts among the particles (frictional regime) and a static bed in which the particles are immobile. The detailed vertical structure of this kind of flows was obtained by means of experiments carried out by Armanini et al. (2005) and Larcher et al. (2007). Armanini et al. (2009) analysed the stratification of rheological mechanisms inside the flow, focusing on the coexistence of frictional and collisional regimes, on the stress transmission inside the flow and on particles kinematics. In particular, it was observed that debris flows may show locally a typical intermittence of the flow regime, switching alternatively from frictional to collisional. While the rheology of the collisional layers is well described by the dense gas analogy (kinetic theory), a persuasive theoretical description of the frictional regime does not yet exist. A Coulombian scheme is often assumed, but this hypothesis is rather limitative because it requires a constant concentration or a distribution of particles concentration known a priori. An interesting scheme of this kind
Sheet atomization of non-Newtonian liquids
NASA Astrophysics Data System (ADS)
Hartranft, Thomas Jay
This experimental investigation examines the "airless" sheet atomization of non-Newtonian fluids using an elliptically-shaped nozzle, which induces a fan-shaped wavy sheet. The goal is to investigate the effects of small magnitudes of extensional viscosity on the sheet breakup features. This, in turn, offers insights for manipulating atomization drop sizes, which can then be applied to industrial spray applications like paint spraying. To further this linkage, these research solutions are formulated to mimic the high-shear-rate viscosity behavior of marine paints. An extensive rheology effort precedes the spray research in order to quantify the extensional viscosity in the fluid that exits the spray nozzle. Glycerin/water-based solutions are formulated to have nearly constant shear viscosity and surface tension while exhibiting over a 1000:1 range of extensional viscosity due to the addition of 50--800 ppm by weight of 9 x 10 6 molecular weight polyacrylamide. These extensional viscosities are measured using a contraction rheometer, which shows that they increase in proportion to the polymer molecular weight and concentration. The polymer molecular weight significantly degrades due to the large strain rates of the spray nozzle. This necessitates the determination of these degraded-solution molecular weights to facilitate correlation with the sheet breakup features. The sprayed fluids are found to have residual molecular weights of only 300,000--500,000 after being sprayed at 7--21 MPa (1000--3000 psi). These molecular weights, in turn, are used with an experimental correlation to estimate the residual extensional viscosities, which are reduced by a factor of about 80:1 from their non-pre-strained magnitudes. In spite of these significant molecular weight and extensional viscosity degradations, polymer concentrations of only 50--800 ppm visibly and quantitatively change the sheet breakup features. The 800 ppm addition has the largest changes with a 30% increase of
Dynamics of Non-Newtonian Liquid Droplet Collision
NASA Astrophysics Data System (ADS)
Chen, Xiaodong; Yang, Vigor
2012-11-01
Collision of Newtonian liquid droplets has been extensively investigated both experimentally and numerically for decades. Limited information, however, is available about non-Newtonian droplet collision dynamics. In the present work, high-fidelity numerical simulations were performed to study the situation associated with shear-thinning non-Newtonian liquids. The formulation is based on a complete set of conservation equations for the liquid and the surrounding gas phases. An improved volume-of-fluid (VOF) method, combined with an innovative topology-oriented adaptive mesh refinement (TOAMR) technique, was developed and implemented to track the interfacial dynamics. The complex evolution of the droplet surface over a broad range of length scales was treated accurately and efficiently. In particular, the thin gas film between two approaching droplets and subsequent breakup of liquid threads were well-resolved. Various types of droplet collision were obtained, including coalescence, bouncing, and reflexive and stretching separations. A regime diagram was developed and compared with that for Newtonian liquids. Fundamental mechanisms and key parameters that dictate droplet behaviors were identified. In addition, collision-induced atomization was addressed. This work was sponsored by the U.S. Army Research Office under the Multi-University Research Initiative under contract No. W911NF-08-1-0124. The support and encouragement provided by Dr. Ralph Anthenien are gratefully acknowledged.
Impinging jet spray formation using non-Newtonian liquids
NASA Astrophysics Data System (ADS)
Rodrigues, Neil S.
Over the past two decades there has been a heightened interest in implementing gelled propellants for rocket propulsion, especially for hypergolic bi-propellants such as monomethylhydrazine (MMH) and nitrogen tetroxide oxidizer (NTO). Due to the very high level of toxicity of hypergolic liquid rocket propellants, increasing safety is an important area of need for continued space exploration and defense operations. Gelled propellants provide an attractive solution to meeting the requirements for safety, while also potentially improving performance. A gelling agent can be added to liquid propellants exhibiting Newtonian behavior to transform the liquid into a non-Newtonian fluid with some solid-like behavior, i.e. a gel. Non-Newtonian jet impingement is very different from its Newtonian counterpart in terms of fluid flow, atomization, and combustion. This is due to the added agents changing physical properties such as the bulk rheology (viscosity) and interfacial rheology (surface tension). Spray characterization of jet impingement with Newtonian liquids has been studied extensively in existing literature. However, there is a scarcity in literature of studies that consider the spray characterization of jet impingement with gelled propellants. This is a rather critical void since a major tradeoff of utilizing gelled propellants is the difficulty with atomization due to the increased effective viscosity. However, this difficulty can be overcome by using gels that exhibit shear-thinning behavior---viscosity decreases with increasing strain rate. Shear-thinning fluids are ideal because they have the distinct advantage of only flowing easily upon pressure. Thereby, greatly reducing the amount of propellant that could be accidentally leaked during both critical functions such as liftoff or engagement in the battlefield and regular tasks like refilling propellant tanks. This experimental work seeks to help resolve the scarcity in existing literature by providing drop size
NASA Astrophysics Data System (ADS)
Li, Jian; Kang, Ruimei; Tang, Xiaohua; She, Houde; Yang, Yaoxia; Zha, Fei
2016-03-01
Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as they can be used for the filtration of heavy oil or the absorption of floating oil from water/oil mixtures. However, most of the superhydrophobic materials used for oil/water separation lose their superhydrophobicity when exposed to hot (e.g. >50 °C) water and strong corrosive liquids. Herein, we demonstrate superhydrophobic overlapped candle soot (CS) and silica coated meshes that can repel hot water (about 92 °C) and strong corrosive liquids, and were used for the gravity driven separation of oil-water mixtures in hot water and strong acidic, alkaline, and salty environments. To the best of our knowledge, we are unaware of any previously reported studies on the use of superhydrophobic materials for the separation of oil from hot water and corrosive aqueous media. In addition, the as-prepared robust superhydrophobic CS and silica coated meshes can separate a series of oils and organic solvents like kerosene, toluene, petroleum ether, heptane and chloroform from water with a separation efficiency larger than 99.0%. Moreover, the as-prepared coated mesh still maintained a separation efficiency above 98.5% and stable recyclability after 55 cycles of separation. The robust superhydrophobic meshes developed in this work can therefore be practically used as a highly efficient filtration membrane for the separation of oil from harsh water conditions, benefiting the environment and human health.Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as
Li, Jian; Kang, Ruimei; Tang, Xiaohua; She, Houde; Yang, Yaoxia; Zha, Fei
2016-04-14
Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as they can be used for the filtration of heavy oil or the absorption of floating oil from water/oil mixtures. However, most of the superhydrophobic materials used for oil/water separation lose their superhydrophobicity when exposed to hot (e.g. >50 °C) water and strong corrosive liquids. Herein, we demonstrate superhydrophobic overlapped candle soot (CS) and silica coated meshes that can repel hot water (about 92 °C) and strong corrosive liquids, and were used for the gravity driven separation of oil-water mixtures in hot water and strong acidic, alkaline, and salty environments. To the best of our knowledge, we are unaware of any previously reported studies on the use of superhydrophobic materials for the separation of oil from hot water and corrosive aqueous media. In addition, the as-prepared robust superhydrophobic CS and silica coated meshes can separate a series of oils and organic solvents like kerosene, toluene, petroleum ether, heptane and chloroform from water with a separation efficiency larger than 99.0%. Moreover, the as-prepared coated mesh still maintained a separation efficiency above 98.5% and stable recyclability after 55 cycles of separation. The robust superhydrophobic meshes developed in this work can therefore be practically used as a highly efficient filtration membrane for the separation of oil from harsh water conditions, benefiting the environment and human health.
Gravity-Driven Hydraulic Fractures
NASA Astrophysics Data System (ADS)
Germanovich, L. N.; Garagash, D.; Murdoch, L. C.; Robinowitz, M.
2014-12-01
This study is motived by a new method for disposing of nuclear waste by injecting it as a dense slurry into a hydraulic fracture that grows downward to great enough depth to permanently isolate the waste. Disposing of nuclear waste using gravity-driven hydraulic fractures is mechanically similar to the upward growth of dikes filled with low density magma. A fundamental question in both applications is how the injected fluid controls the propagation dynamics and fracture geometry (depth and breadth) in three dimensions. Analog experiments in gelatin [e.g., Heimpel and Olson, 1994; Taisne and Tait, 2009] show that fracture breadth (the short horizontal dimension) remains nearly stationary when the process in the fracture "head" (where breadth is controlled) is dominated by solid toughness, whereas viscous fluid dissipation is dominant in the fracture tail. We model propagation of the resulting gravity-driven (buoyant or sinking), finger-like fracture of stationary breadth with slowly varying opening along the crack length. The elastic response to fluid loading in a horizontal cross-section is local and can be treated similar to the classical Perkins-Kern-Nordgren (PKN) model of hydraulic fracturing. The propagation condition for a finger-like crack is based on balancing the global energy release rate due to a unit crack extension with the rock fracture toughness. It allows us to relate the net fluid pressure at the tip to the fracture breadth and rock toughness. Unlike the PKN fracture, where breadth is known a priori, the final breadth of a finger-like fracture is a result of processes in the fracture head. Because the head is much more open than the tail, viscous pressure drop in the head can be neglected leading to a 3D analog of Weertman's hydrostatic pulse. This requires relaxing the local elasticity assumption of the PKN model in the fracture head. As a result, we resolve the breadth, and then match the viscosity-dominated tail with the 3-D, toughness
Mansour, A.; Chigier, N.
1994-06-01
The changes in the physical processes of atomization as a result of adding a high molecular weight polymer in low concentrations to liquid have been studied. Both Newtonian and non-Newtonian liquids were investigated with particular emphasis on the non-Newtonian rheological characteristics. It was found that viscoelastic liquids are much more difficult to atomize than viscoinelastic liquids. Viscoinelastic liquids showed a breakup behavior similar to that of water sprays. Viscoelastic materials showed remarkably different breakup patterns. The ligaments were seen to undergo a very large stretching motion before they breakup, resulting in long threads of liquid attached to droplets. The normal stresses developed in viscoelastic materials are much higher than their associated shear stresses. Consequently, the development of the large normal stresses appears to be the most important rheological mechanism that inhibits breakup. The non-Newtonian liquids selected for the experiment were aqueous solutions of Xanthan gum and Polyacrylamide E10.
On predicting the onset of transient convection in porous media saturated with Non-Newtonian liquid
NASA Astrophysics Data System (ADS)
Tan, K. K.; Pua, S. Y.; Yang, A.
2017-06-01
The onset of transient convection in non-Newtonian liquid immersing porous media was simulated using a Computational Fluid Dynamics (CFD) package for the thermal boundary condition of Fixed Surface Temperature (FST). Most of the simulated values of stability criteria were found to be in good agreement with the predicted and theoretical values of transient critical Rayleigh number for non-Newtonian liquid defined by Tan and Thorpe (1992) for power-law fluids. The critical transient Rayleigh numbers for convection in porous media were found to be in good agreement with theoretical values by using apparent viscosity µapp at zero shear. The critical time and critical depth for transient heat conduction were then determined accurately that
Zhu, W; Aitken, B G; Sen, S
2017-02-28
All families of inorganic glass-forming liquids display non-Newtonian rheological behavior in the form of shear thinning at high shear rates. Experimental evidence is presented to demonstrate the existence of remarkable universality in this behavior, irrespective of chemical composition, structure, topology, and viscosity. However, contrary to intuition, in all cases the characteristic shear rates that mark the onset of shear thinning in these liquids are orders of magnitude slower than the global shear relaxation rates. Attempt is made to reconcile such differences within the framework of the cooperative structural relaxation model of glass-forming liquids.
NASA Astrophysics Data System (ADS)
Zhu, W.; Aitken, B. G.; Sen, S.
2017-02-01
All families of inorganic glass-forming liquids display non-Newtonian rheological behavior in the form of shear thinning at high shear rates. Experimental evidence is presented to demonstrate the existence of remarkable universality in this behavior, irrespective of chemical composition, structure, topology, and viscosity. However, contrary to intuition, in all cases the characteristic shear rates that mark the onset of shear thinning in these liquids are orders of magnitude slower than the global shear relaxation rates. Attempt is made to reconcile such differences within the framework of the cooperative structural relaxation model of glass-forming liquids.
Collision Dynamics and Internal Mixing of Droplets of Non-Newtonian Liquids
NASA Astrophysics Data System (ADS)
Sun, Kai; Zhang, Peng; Law, Chung K.; Wang, Tianyou
2015-11-01
The efficient internal mixing of colliding droplets upon coalescence is critical to various technological processes such as color manipulation in ink-jet printing and the initiation of the liquid-phase reaction of gelled hypergolic propellants in rocket engines. Recognizing that such processes can be optimized by varying the impact inertia as well as employing fluids of non-Newtonian rheology, the head-on collision, coalescence, and internal mixing pattern between two impacting equal-sized droplets of non-Newtonian fluids is computationally investigated by using the lattice Boltzmann method. Results show that, with increasing non-Newtonian effects, droplet deformation and separation following coalescence is promoted for shear-thinning fluids, while permanent coalescence allowing an extended duration for mixing is promoted for shear-thickening fluids. Furthermore, large-scale internal mixing is promoted for the colliding droplets with larger shear-thinning disparity, while coalescence and mixing is synergistically facilitated for the collision between a shear-thinning droplet and a shear-thickening droplet. The individual and coupled influences of viscosity on the droplet deformation and impact inertia, internal motion, viscous loss, and merging of the colliding interfaces leading to the observed outcomes are mechanistically identified and described.
Theory of creeping gravity currents of a non-Newtonian liquid
Gratton, Julio; Minotti, Fernando; Mahajan, Swadesh M.
1999-12-01
Recently several experiments on creeping gravity currents have been performed, using highly viscous silicone oils and putties. The interpretation of the experiments relies on the available theoretical results that were obtained by means of the lubrication approximation with the assumption of a Newtonian rheology. Since very viscous fluids are usually non-Newtonian, an extension of the theory to include non-Newtonian effects is needed. We derive the governing equations for unidirectional and axisymmetric creeping gravity currents of a non-Newtonian liquid with a power-law rheology, generalizing the usual lubrication approximation. The equations differ from those for Newtonian liquids, being nonlinear in the spatial derivative of the thickness of the current. Similarity solutions for currents whose volume varies as a power of time are obtained. For the spread of a constant volume of liquid, analytic solutions are found that are in good agreement with experiment. We also derive solutions of the waiting-time type, as well as those describing steady flows from a constant source to a sink. General traveling-wave solutions are given, and analytic formulas for a simple case are derived. A phase plane formalism that allows the systematic derivation of self-similar solutions is introduced. The application of the Boltzmann transform is briefly discussed. All the self-similar solutions obtained here have their counterparts in Newtonian flows, as should be expected because the power-law rheology involves a single-dimensional parameter as the Newtonian constitutive relation. Thus one finds similarity solutions whenever the analogous Newtonian problem is self-similar, but now the spreading relations are rheology-dependent. In most cases this dependence is weak but leads to significant differences easily detected in experiments. The present results may also be of interest for geophysics since the lithosphere deforms according to an average power-law rheology. (c) 1999 The American
Theory of creeping gravity currents of a non-Newtonian liquid
NASA Astrophysics Data System (ADS)
Gratton, Julio; Minotti, Fernando; Mahajan, Swadesh M.
1999-12-01
Recently several experiments on creeping gravity currents have been performed, using highly viscous silicone oils and putties. The interpretation of the experiments relies on the available theoretical results that were obtained by means of the lubrication approximation with the assumption of a Newtonian rheology. Since very viscous fluids are usually non-Newtonian, an extension of the theory to include non-Newtonian effects is needed. We derive the governing equations for unidirectional and axisymmetric creeping gravity currents of a non-Newtonian liquid with a power-law rheology, generalizing the usual lubrication approximation. The equations differ from those for Newtonian liquids, being nonlinear in the spatial derivative of the thickness of the current. Similarity solutions for currents whose volume varies as a power of time are obtained. For the spread of a constant volume of liquid, analytic solutions are found that are in good agreement with experiment. We also derive solutions of the waiting-time type, as well as those describing steady flows from a constant source to a sink. General traveling-wave solutions are given, and analytic formulas for a simple case are derived. A phase plane formalism that allows the systematic derivation of self-similar solutions is introduced. The application of the Boltzmann transform is briefly discussed. All the self-similar solutions obtained here have their counterparts in Newtonian flows, as should be expected because the power-law rheology involves a single-dimensional parameter as the Newtonian constitutive relation. Thus one finds similarity solutions whenever the analogous Newtonian problem is self-similar, but now the spreading relations are rheology-dependent. In most cases this dependence is weak but leads to significant differences easily detected in experiments. The present results may also be of interest for geophysics since the lithosphere deforms according to an average power-law rheology.
Non-Newtonian Liquid Flow through Small Diameter Piping Components: CFD Analysis
NASA Astrophysics Data System (ADS)
Bandyopadhyay, Tarun Kanti; Das, Sudip Kumar
2016-10-01
Computational Fluid Dynamics (CFD) analysis have been carried out to evaluate the frictional pressure drop across the horizontal pipeline and different piping components, like elbows, orifices, gate and globe valves for non-Newtonian liquid through 0.0127 m pipe line. The mesh generation is done using GAMBIT 6.3 and FLUENT 6.3 is used for CFD analysis. The CFD results are verified with our earlier published experimental data. The CFD results show the very good agreement with the experimental values.
Non-Newtonian flow of an ultralow-melting chalcogenide liquid in strongly confined geometry
Wang, Siyuan; Jain, Chhavi; Wondraczek, Katrin; Kobelke, Jens; Wondraczek, Lothar; Troles, Johann; Caillaud, Celine; Schmidt, Markus A.
2015-05-18
The flow of high-viscosity liquids inside micrometer-size holes can be substantially different from the flow in the bulk, non-confined state of the same liquid. Such non-Newtonian behavior can be employed to generate structural anisotropy in the frozen-in liquid, i.e., in the glassy state. Here, we report on the observation of non-Newtonian flow of an ultralow melting chalcogenide glass inside a silica microcapillary, leading to a strong deviation of the shear viscosity from its value in the bulk material. In particular, we experimentally show that the viscosity is radius-dependent, which is a clear indication that the microscopic rearrangement of the glass network needs to be considered if the lateral confinement falls below a certain limit. The experiments have been conducted using pressure-assisted melt filling, which provides access to the rheological properties of high-viscosity melt flow under previously inaccessible experimental conditions. The resulting flow-induced structural anisotropy can pave the way towards integration of anisotropic glasses inside hybrid photonic waveguides.
Flow of a Non-Newtonian Liquid with a Free Surface
NASA Astrophysics Data System (ADS)
Borzenko, E. I.; Shrager, G. R.
2016-07-01
A fountain flow of a non-Newtonian liquid filling a vertical plane channel was investigated. The problem of this flow was solved by the finite-difference method on the basis of a system of complete equations of motion with natural boundary conditions on the free surface of the liquid. The stability of calculations was provided by regularization of the rheological Ostwald-de Waele law. It is shown that the indicated flow is divided into a zone of two-dimensional flow in the neighborhood of the free surface and a zone of one-dimensional flow at a distance from this surface. A parametric investigation of the dependence of the kinetic characteristics of the fountain flow and the behavior of its free surface on the determining criteria of this flow and its rheological parameters has been performed.
Deshpande, S.D.
1985-01-01
Non-Newtonian liquid-gas stratified flow data in 0.026- and 0.052-m-diameter pipes were obtained. Interfacial level gradients between the two phases were observed. The Heywood-Charles model is found to be valid for pseudoplastic liquid-gas uniform stratified flow. Two-phase drag reduction in non-Newtonian systems was not achieved as the transition to semi-slug flow occurred before the model criteria were reached. Interfacial liquid and gas shear stresses were compared. A new parameter ..sigma../sup 2/ is introduced which is a numerical indication of the interfacial level gradient. Two-phase drag reduction was experimentally observed in polymer solution-air plug-slug flow in 0.026- and 0.052-m-diameter pipes. The Hubbard-Dukler pressure drop model was extended to non-Newtonian systems. Reasonable agreement between the experiment and the model predictions is obtained. However, more work needs to be done in order to better understand the two-phase drag reduction phenomena. Liquid holdup correlations were developed for both Newtonian and non-Newtonian systems which successfully correlate the holdup over a wide range of parameters. The Petukhov correlation is found to be better than the Dittus-Boelter correlation in predicting the single-phase water heat-transfer coefficients.
NASA Astrophysics Data System (ADS)
Jin, Guang Lin; Ahn, Won-Gi; Kim, See Jo; Nam, Jaewook; Jung, Hyun Wook; Hyun, Jae Chun
2016-05-01
In this study, a strategy for designing optimal shim configuration inside a slot die is suggested to assure the uniform coating flow distribution of various non-Newtonian shear-thinning liquids at the die exit in a slot coating system. Flow patterns of non-Newtonian liquids inside the slot die, via three-dimensional computations, have been compared using various shim geometries which can adjust the flow region in a slot manifold. The rather non-uniform (parabolic) velocity distributions of shear-thinning liquids at the die exit under the basic shim condition could be effectively flattened by the modification of shim geometry without the change of die manifold structure. Dimensions of hybrid shims for controlling flow features at edge and center regions within slit channel are positively tuned, according to the shear-thinning level of coating liquids.
Gas-driven displacement of a non-Newtonian liquid in a radial Hele-Shaw cell
NASA Astrophysics Data System (ADS)
White, Andrew; Ward, Thomas
2012-11-01
The displacement of a non-Newtonian liquid by a less viscous fluid has applications in a number of industries such as lubricating oils, injection molding and cement placement in oil wells to name a few. A convenient geometry to study such a problem is that of the Hele-Shaw cell due to its ability to effectively reduce the flow to two dimensions when the gap spacing is much smaller than the other spatial dimensions. We will study the radial displacement of a finite drop of non-Newtonian shear-thinning and extensionally-thickening liquid by a gas at constant pressure in a Hele-Shaw cell with gap spacing O(10-100) microns. Different concentrations of a polymer in oil will be used to examine changes in the displacement rate, residual film thickness and resulting Saffman-Taylor instability as the viscoelastic time scale overtakes that of the bulk displacement.
Electro-hydrodynamic instability in a microchannel between a Newtonian and a non-Newtonian liquid
NASA Astrophysics Data System (ADS)
Ersoy, Gülsüm; Kerem Uguz, A.
2012-06-01
We perform linear stability analysis of the interface between a Newtonian fluid and a non-Newtonian fluid, assumed to obey the Upper Convective Maxwell model, flowing in a channel due to a pressure gradient subject to an electric field applied normal to the interface. The fluids are assumed to be immiscible, incompressible and leaky dielectric. A detailed parametric study of the effects of the system parameters, such as Weissenberg number, Reynolds number, applied potential and physical and electrical properties of the fluids, is conducted. It is found that increasing the applied voltage could be stabilizing or destabilizing depending on the electrical properties of the liquids, and increasing the Weissenberg number decreases the maximum growth rate without changing the corresponding wavenumber and increases the critical wavenumber. The effect of the height ratio of the liquids is analyzed through neutral curves for given electric numbers, i.e. applied potential. The critical wavenumber decreases with height ratio and converges to a value for all the electric numbers considered.
NASA Astrophysics Data System (ADS)
Galiullina, G. R.; Vachagina, E. K.; Khalitova, G. R.
2010-03-01
In the present paper, we consider the heat transfer of non-Newtonian liquid flows moving in convergent- divergent channels with common boundary. The case of flows moving in opposite directions was addressed. At the common boundary, continuity conditions for temperature and heat flow were adopted. A mathematical model, a calculation algorithm, and simulation data are reported. Plots of numerical data characterizing the channel flows are presented. A comparative analysis of heat transfer in smooth and convergent-divergent channels is given.
NASA Astrophysics Data System (ADS)
Sen, S.; Zhu, W.; Aitken, B. G.
2017-07-01
The steady and oscillatory shear rate dependence of viscosity of a supercooled chalcogenide liquid of composition As10Se90 is measured at Newtonian viscosities ranging between 103 and 107 Pa s using capillary and parallel plate rheometry. The liquid displays strong violation of the Cox-Merz rule in the non-Newtonian regime where the viscosity under steady shear is nearly an order of magnitude lower than that under oscillatory shear. This behavior is argued to be related to the emergence of unusually large (6-8 nm) cooperatively rearranging regions with long relaxation times in the liquid that result from significant structural rearrangements under steady shear.
Digilov, Rafael M
2008-12-02
The impact of non-Newtonian behavior and the dynamic contact angle on the rise dynamics of a power law liquid in a vertical capillary is studied theoretically and experimentally for quasi-steady-state flow. An analytical solution for the time evolution of the meniscus height is obtained in terms of a Gaussian hypergeometric function, which in the case of a Newtonian liquid reduces to the Lucas-Washburn equation modified by the dynamic contact angle correction. The validity of the solution is checked against experimental data on the rise dynamics of a shear-thinning cmc solution in a glass microcapillary, and excellent agreement is found.
Simultaneous pulsatile flow and oscillating wall of a non-Newtonian liquid
NASA Astrophysics Data System (ADS)
Herrera-Valencia, E. E.; Sánchez-Villavicencio, M. L.; Calderas, F.; Pérez-Camacho, M.; Medina-Torres, L.
2016-11-01
In this work, analytical predictions of the rectilinear flow of a non-Newtonian liquid are given. The fluid is subjected to a combined flow: A pulsatile time-dependent pressure gradient and a random longitudinal vibration at the wall acting simultaneously. The fluctuating component of the combined pressure gradient and oscillating flow is assumed to be of small amplitude and can be adequately represented by a weakly stochastic process, for which a quasi-static perturbation solution scheme is suggested, in terms of a small parameter. This flow is analyzed with the Tanner constitutive equation model with the viscosity function represented by the Ellis model. According to the coupled Tanner-Ellis model, the flow enhancement can be separated in two contributions (pulsatile and oscillating mechanisms) and the power requirement is always positive and can be interpreted as the sum of a pulsatile, oscillating, and the coupled systems respectively. Both expressions depend on the amplitude of the oscillations, the perturbation parameter, the exponent of the Ellis model (associated to the shear thinning or thickening mechanisms), and the Reynolds and Deborah numbers. At small wall stress values, the flow enhancement is dominated by the axial wall oscillations whereas at high wall stress values, the system is governed by the pulsating noise perturbation. The flow transition is obtained for a critical shear stress which is a function of the Reynolds number, dimensionless frequency and the ratio of the two amplitudes associated with the pulsating and oscillating perturbations. In addition, the flow enhancement is compared with analytical and numerical predictions of the Reiner-Phillipoff and Carreau models. Finally, the flow enhancement and power requirement are predicted using biological rheometric data of blood with low cholesterol content.
NASA Astrophysics Data System (ADS)
Iwamatsu, Masao
2017-07-01
The spreading of a cap-shaped spherical droplet of non-Newtonian power-law liquids, both shear-thickening and shear-thinning liquids, that completely wet a spherical substrate is theoretically investigated in the capillary-controlled spreading regime. The crater-shaped droplet model with the wedge-shaped meniscus near the three-phase contact line is used to calculate the viscous dissipation near the contact line. Then the energy balance approach is adopted to derive the equation that governs the evolution of the contact line. The time evolution of the dynamic contact angle θ of a droplet obeys a power law θ ˜t-α with the spreading exponent α , which is different from Tanner's law for Newtonian liquids and those for non-Newtonian liquids on a flat substrate. Furthermore, the line-tension dominated spreading, which could be realized on a spherical substrate for late-stage of spreading when the contact angle becomes low and the curvature of the contact line becomes large, is also investigated.
Measurements of gravity driven granular channel flows
NASA Astrophysics Data System (ADS)
Facto, Kevin
This dissertation presents experiments that studied two gravity driven granular channel flows. The first experiment used magnetic resonance imaging to measure the density and displacement distributions of poppy seeds flowing in a rough walled channel. Time-averaged measurements of normalized velocity and density showed little flow speed dependence. Instantaneous measurements, however, showed marked velocity dependence in the displacement distributions. There was evidence of aperiodic starting and stopping at lower flow speeds and the onset of density waves on a continuous flow at higher speeds. The second experiment measured forces in all three spatial directions at the boundary of a flow of steel balls. The relationship between the normal and the tangential forces were examined statistically and compared to the Coulomb friction model. For both large and small forces, the tangential and normal forces are unrelated, as there appears to be a strong tendency for the tangential force to maintain a value that will bear the weight the weight of the particles in flow.
Bentzen, T R; Ratkovich, N; Madsen, S; Jensen, J C; Bak, S N; Rasmussen, M R
2012-01-01
Fouling is the main bottleneck of the widespread use of MBR systems. One way to decrease and/or control fouling is by process hydrodynamics. This can be achieved by the increase of liquid cross-flow velocity. In rotational cross-flow MBR systems, this is attained by the spinning of, for example, impellers. Validation of the CFD (computational fluid dynamics) model was made against laser Doppler anemometry (LDA) tangential velocity measurements (error less than 8%) using water as a fluid. The shear stress over the membrane surface was inferred from the CFD simulations for water. However, activated sludge (AS) is a non-Newtonian liquid, for which the CFD model was modified incorporating the non-Newtonian behaviour of AS. Shear stress and area-weighted average shear stress relationships were made giving error less that 8% compared with the CFD results. An empirical relationship for the area-weighted average shear stress was developed for water and AS as a function of the angular velocity and the total suspended solids concentration. These relationships can be linked to the energy consumption of this type of systems.
Time-Resolved imaging Studies of Laser-Induced Jet Formation in Non-Newtonian Liquid Films
NASA Astrophysics Data System (ADS)
Turkoz, Emre; Arnold, Craig
2016-11-01
Blister-actuated laser-induced forward transfer (BA-LIFT) is a nozzle-less printing technique that offers an alternative to inkjet printing. The lack of a nozzle allows for a wider range of inks since clogging is not a concern. In this work, a focused laser pulse is absorbed within a polymer layer coated with a thin liquid film. The pulse causes a rapidly expanding blister to be formed that induces a liquid jet. Various well-studied non-Newtonian solutions are tested to examine how the shear-thinning and shear-thickening characteristics affect jet formation. The time delay between pulses is varied along with the energy, and different regimes of transfer are identified. We explore how Ohnesorge number, Weber number and spot size affect the jet formation and evaluate parameters that lead to breakup of jets into droplets.
Steele, Catriona M; James, David F; Hori, Sarah; Polacco, Rebecca C; Yee, Clemence
2014-06-01
Thickened liquids are frequently used in the management of oropharyngeal dysphagia. Previous studies suggest that compression of a liquid bolus between the tongue and the palate in the oral phase of swallowing serves a sensory function, enabling the tuning of motor behavior to match the viscosity of the bolus. However, the field lacks information regarding healthy oral sensory discrimination ability for small differences in liquid viscosity. We undertook to measure oral viscosity discrimination ability for five non-Newtonian xanthan gum-thickened liquids in the nectar- and honey-thick range. Xanthan gum concentration ranged from 0.5 to 0.87 % and increased by an average of 0.1 % between stimuli in the array. This translated to an average apparent viscosity increase of 0.2-fold between adjacent stimuli at 50 reciprocal seconds (/s). A triangle test paradigm was used to study stimulus discrimination in 78 healthy adults in two, sex-balanced age cohorts. Participants were provided 5-ml samples of liquids in sets of three; one liquid differed in xanthan gum concentration from the other two. Participants were required to sample the liquid orally and indicate which sample was perceived to have a different viscosity. A protocol of 20 sets (60 samples) allowed calculation of the minimum difference in xanthan gum concentration detected accurately. On average, participants were able to accurately detect a 0.38-fold increase in xanthan-gum concentration, translating to a 0.67-fold increase in apparent viscosity at 50/s. The data did not suggest the existence of a nonlinear point boundary in apparent viscosity within the range tested. No differences in viscosity discrimination were found between age cohorts or as a function of sex. The data suggest that for xanthan gum-thickened liquids, there may be several increments of detectably different viscosity within the ranges currently proposed for nectar- and honey-thick liquids. If physiological or functional differences in
Tornadolike gravity-driven vortex model
NASA Technical Reports Server (NTRS)
Deissler, R. G.; Boldman, D. R.
1974-01-01
The buoyancy-induced vorticity concentration produced as the fluid in a vortex accelerates vertically was studied. The boiloff from liquid nitrogen, to which a small amount of initial vorticity was added, provided a source of cool, heavy gas in which a concentration of vorticity took place. Condensation streamers made the flow visible. It is shown that the presence of a surface boundary layer is not necessary for the effective concentration of vorticity. A simple theoretical analysis of the phenomenon was also made. A radial contraction of the flow with vertical position and a characteristic hook shape in the top view of the streamlines were observed in both theory and experiment. The vorticity concentration observed may be similar to that which occurs in tornadoes.
Gravity driven flows of bubble suspensions.
NASA Astrophysics Data System (ADS)
Zenit, Roberto; Koch, Donald L.; Sangani, Ashok K.
1999-11-01
Experiments on vertical and inclined channels were performed to study the behavior of a mono-dispersed bubble suspension for which the dual limit of large Reynolds number and small Weber number is satisfied. A uniform stream of 1.5 mm diameter bubbles is produced by a bank of identical capillaries and coalescence is inhibited by addition of salt to the water. Measurements of the liquid velocity and bubble-probe collision rate are obtained with a hot wire anemometer. The gas volume fraction, bubble velocity, velocity variance and chord length are measured using a dual impedance probe. Image analysis is used to quantify the distributions of bubble size and aspect ratio. For vertical channels the bubble velocity is observed to decrease as the bubble concentration increases in accord with the predictions of Spelt and Sangani (1998). The bubble velocity variance arises largely due to bubble-wall and bubble-bubble collisions. For inclined channels, the strength of the shear flow is controlled by the extent of bubble segregation and the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion for a range of gas volume fractions and channel inclination angles.
Gravity-driven infiltration instability in initially dry nonhorizontal fractures
Nicholl, M.J.; Glass, R.J. ); Wheatcraft, S.W. )
1994-09-01
Experimental evidence demonstrating gravity-driven wetting front instability in an initially dry natural fracture is presented. An experimental approach is developed using a transparent analog rough-walled fracture to explore gravity-driven instability. Three different boundary conditions were observed to produce unstable fronts in the analog fracture: application of fluid at less than the imbibition capacity, inversion of a density-stratified system, and redistribution of flow at the cessation of stable infiltration. The redistribution boundary condition (analogous to the cessation of ponded infiltration) is considered in a series of systematic experiments. Gravitational gradient and magnitude of the fluid input were varied during experimentation. Qualitative observations imply that finger development is strongly correlated to the structure of the imbibition front at the onset of flow redistribution. Measurements of finger width is compared to theoretical predictions based on linear stability theory. 28 refs., 11 fig., 1 tab.
The Effect of Surface Tension on the Gravity-driven Thin Film Flow of Newtonian and Power-law Fluids
Hu, Bin; Kieweg, Sarah L.
2012-01-01
Gravity-driven thin film flow is of importance in many fields, as well as for the design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. There have been many prior works on gravity-driven thin films. However, the incorporation of surface tension effect has not been well studied for non-Newtonian fluids. After surface tension effect was incorporated into our 2D (i.e. 1D spreading) power-law model, we found that surface tension effect not only impacted the spreading speed of the microbicide gel, but also had an influence on the shape of the 2D spreading profile. We observed a capillary ridge at the front of the fluid bolus. Previous literature shows that the emergence of a capillary ridge is strongly related to the contact line fingering instability. Fingering instabilities during epithelial coating may change the microbicide gel distribution and therefore impact how well it can protect the epithelium. In this study, we focused on the capillary ridge in 2D flow and performed a series of simulations and showed how the capillary ridge height varies with other parameters, such as surface tension coefficient, inclination angle, initial thickness, and power-law parameters. As shown in our results, we found that capillary ridge height increased with higher surface tension, steeper inclination angle, bigger initial thickness, and more Newtonian fluids. This study provides the initial insights of how to optimize the flow and prevent the appearance of a capillary ridge and fingering instability. PMID:23687391
Hu, Bin; Kieweg, Sarah L
2012-07-15
Gravity-driven thin film flow is of importance in many fields, as well as for the design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. There have been many prior works on gravity-driven thin films. However, the incorporation of surface tension effect has not been well studied for non-Newtonian fluids. After surface tension effect was incorporated into our 2D (i.e. 1D spreading) power-law model, we found that surface tension effect not only impacted the spreading speed of the microbicide gel, but also had an influence on the shape of the 2D spreading profile. We observed a capillary ridge at the front of the fluid bolus. Previous literature shows that the emergence of a capillary ridge is strongly related to the contact line fingering instability. Fingering instabilities during epithelial coating may change the microbicide gel distribution and therefore impact how well it can protect the epithelium. In this study, we focused on the capillary ridge in 2D flow and performed a series of simulations and showed how the capillary ridge height varies with other parameters, such as surface tension coefficient, inclination angle, initial thickness, and power-law parameters. As shown in our results, we found that capillary ridge height increased with higher surface tension, steeper inclination angle, bigger initial thickness, and more Newtonian fluids. This study provides the initial insights of how to optimize the flow and prevent the appearance of a capillary ridge and fingering instability.
Electrokinetics of non-Newtonian fluids: a review.
Zhao, Cunlu; Yang, Chun
2013-12-01
This work presents a comprehensive review of electrokinetics pertaining to non-Newtonian fluids. The topic covers a broad range of non-Newtonian effects in electrokinetics, including electroosmosis of non-Newtonian fluids, electrophoresis of particles in non-Newtonian fluids, streaming potential effect of non-Newtonian fluids and other related non-Newtonian effects in electrokinetics. Generally, the coupling between non-Newtonian hydrodynamics and electrostatics not only complicates the electrokinetics but also causes the fluid/particle velocity to be nonlinearly dependent on the strength of external electric field and/or the zeta potential. Shear-thinning nature of liquids tends to enhance electrokinetic phenomena, while shear-thickening nature of liquids leads to the reduction of electrokinetic effects. In addition, directions for the future studies are suggested and several theoretical issues in non-Newtonian electrokinetics are highlighted. © 2013.
On the flow of a non-Newtonian liquid induced by intestine-like contractions.
Phan-Thien, N; Low, H T
1989-02-01
This paper considers the flow of an inelastic liquid which is generated by contractions like those of the intestine. Unlike regular peristaltic motion, these contractions occur locally over a finite length and have a finite amplitude. We adopt a contraction model due to Macagno and Christensen and repeat their analysis for an inelastic liquid. Our analysis, which is based on a Boundary Element Method, indicates that the net flow rate depends very weakly on the power-law index. The pumping action is therefore similar to that of a positive displacement pump.
Condensation during gravity driven ECC: Experiments with PACTEL
Munther, R.; Kalli, H.; Kouhia, J.
1995-09-01
This paper provides the results of the second series of gravity driven emergency core cooling (ECC) experiments with PACTEL (Parallel Channel Test Loop). The simulated accident was a small break loss-of-coolant accident (SBLOCA) with a break in a cold leg. The ECC flow was provided from a core makeup tank (CMT) located at a higher elevation than the main part of the primary system. The CMT was pressurized with pipings from the pressurizer and a cold leg. The tests indicated that steam condensation in the CMT can prevent ECC and lead to core uncovery.
A gravity-driven low-rate particle feeder
NASA Astrophysics Data System (ADS)
Chen, Wei-Yin; Gowan, George; Shi, Guang; Wan, Shaolong
2008-08-01
A gravity-driven particle feeder has been designed, fabricated, and tested to feed particles at low rates. A solenoid and a digital timer regulate the feed rate. This design avoids moving parts at the system periphery and thus avoids possible air leakages. It does not use pressurized gas to blow the particles into the desired location and thus pressure disturbance is avoided. The feeder can be operated at either a batch or a near continuous mode. Moreover, feeding a single large particle at a desired time is also feasible in such gaseous environments.
Basal entrainment by Newtonian gravity-driven flows
NASA Astrophysics Data System (ADS)
Bates, Belinda M.; Andreini, Nicolas; Ancey, Christophe
2016-05-01
Gravity-driven flows can erode the bed along which they descend and increase their mass by a factor of 10 or more. This process is called "basal entrainment." Although documented by field observations and laboratory experiments, it remains poorly understood. This paper examines what happens when a viscous gravity-driven flow generated by releasing a fixed volume of incompressible Newtonian fluid encounters a stationary layer (composed of fluid with the same density and viscosity). Models based on depth-averaged mass and momentum balance equations deal with bed-flow interfaces as shock waves. In contrast, we use an approach involving the long-wave approximation of the Navier-Stokes equations (lubrication theory), and in this context, bed-flow interfaces are acceleration waves that move quickly across thin stationary layers. The incoming flow digs down into the bed, pushing up downstream material, thus advancing the flow front. Extending the method used by Huppert ["The propagation of two-dimensional and axisymmetric viscous gravity currents over a rigid horizontal surface," J. Fluid Mech. 121, 43-58 (1982)] for modeling viscous dam-break waves, we end up with a nonlinear diffusion equation for the flow depth, which is solved numerically. Theory is compared with experimental results. Excellent agreement is found in the limit of low Reynolds numbers (i.e., for flow Reynolds numbers lower than 20) for the front position over time and flow depth profile.
Fluid bulk velocity and attenuation measurements in non-Newtonian liquids using a dipstick sensor
NASA Astrophysics Data System (ADS)
Cegla, F. B.; Cawley, P.; Lowe, M. J. S.
2006-02-01
This paper reports an evaluation of a method to measure acoustic fluid bulk properties in order to characterize the fluid. The method is based on a 'dipstick' that is inserted into the liquid of interest; a propagating interface wave, called the quasi-Scholte mode, is used to extract the necessary information. Quasi-Scholte mode measurements on four different silica-suspensions are compared to experiments in a conventional ultrasonic test cell. The results show that the liquid bulk velocity can accurately be retrieved by means of the new approach and errors range within the uncertainties imposed by the experimental setup (0.5%). Further bulk velocity measurements on distilled water and a 5% ethanol-distilled-water mixture over a range of temperatures illustrate that the method can successfully monitor small changes in velocity. The values of fluid attenuation measured by the two techniques agree well in their qualitative trends but quantitative differences of up to 20% are encountered. Errors in the measurements are believed to be mainly due to geometrical features of the current setup.
Contact Line Instability of Gravity-Driven Flow of Power-Law Fluids.
Hu, Bin; Kieweg, Sarah L
2015-11-01
The moving contact line of a thin fluid film can often corrugate into fingers, which is also known as a fingering instability. Although the fingering instability of Newtonian fluids has been studied extensively, there are few studies published on contact line fingering instability of non-Newtonian fluids. In particular, it is still unknown how shear-thinning rheological properties can affect the formation, growth, and shape of a contact line instability. Our previous study (Hu and Kieweg, 2012) showed a decreased capillary ridge formation for more shear-thinning fluids in a 2D model (i.e. 1D thin film spreading within the scope of lubrication theory). Those results motivated this study's hypothesis: more shear-thinning fluids should have suppressed finger growth and longer finger wavelength, and this should be evident in linear stability analysis (LSA) and 3D (i.e. 2D spreading) numerical simulations. In this study, we developed a LSA model for the gravity-driven flow of shear-thinning films, and carried out a parametric study to investigate the impact of shear-thinning on the growth rate of the emerging fingering pattern. A fully 3D model was also developed to compare and verify the LSA results using single perturbations, and to explore the result of multiple-mode, randomly imposed perturbations. Both the LSA and 3D numerical results confirmed that the contact line fingers grow faster for Newtonian fluids than the shear-thinning fluids on both vertical and inclined planes. In addition, both the LSA and 3D model indicated that the Newtonian fluids form fingers with shorter wavelengths than the shear-thinning fluids when the plane is inclined; no difference in the most unstable (i.e. emerging) wavelength was observed at vertical. This study also showed that the distance between emerging fingers was smaller on a vertical plane than on a less-inclined plane for shear-thinning fluids, as previously shown for Newtonian fluids. For the first time for shear
Photonic crystal beads from gravity-driven microfluidics.
Gu, Hongcheng; Rong, Fei; Tang, Baocheng; Zhao, Yuanjin; Fu, Degang; Gu, Zhongze
2013-06-25
This Letter reports a simple method for the mass production of 3D colloidal photonic crystal beads (PCBs) by using a gravity-driven microfluidic device and online droplet drying method. Compared to traditional methods, the droplet templates of the PCBs are generated by using the ultrastable gravity as the driving force for the microfluidics, thus the PCBs are formed with minimal polydispersity. Moreover, drying of the droplet templates is integrated into the production process, and the nanoparticles in the droplets self-assemble online. Overall, this process results in PCBs with good morphology, low polydispersity, brilliant structural colors, and narrow stop bands. PCBs could be bulk generated by this process for many practical applications, such as multiplex-encoded assays and the construction of novel optical materials.
Basal entrainment by Newtonian gravity-driven flows
NASA Astrophysics Data System (ADS)
Bates, Belinda; Andreini, Nicolas; Ancey, Christophe
2016-04-01
Gravity-driven flows can erode the bed along which they descend and increase their mass by a factor of 10 or more. This process is called basal entrainment. Although documented by field observations and laboratory experiments, it remains poorly understood. We look into this issue by studying eroding dam-break waves. More specifically we would like to determine what happens when a viscous gravity-driven flow generated by releasing a fixed volume of incompressible Newtonian fluid encounters a stationary erodible layer (composed of fluid with the same density and viscosity). Models based on depth-averaged mass and momentum balance equations deal with bed-flow interfaces as shock waves. In contrast, we use an approach involving the long-wave approximation of the Navier-Stokes equations (lubrication theory), and in this context, bed-flow interfaces are acceleration waves that move quickly across thin stationary layers. The incoming flow digs down into the bed, pushing up downstream material, thus advancing the flow front. Extending the method used by Huppert [J. Fluid Mech. 121, 43--58 (1982)] for modelling viscous dam-break waves, we end up with a nonlinear diffusion equation for the flow depth, which is solved numerically. Theory is compared with experimental results. Excellent agreement is found in the limit of low Reynolds numbers (i.e., for flow Reynolds numbers lower than 20) for the front position over time and flow depth profile. The Newtonian model has sometimes been used to describe the flow behaviour of natural materials such as snow and debris suspensions, but the majority of existing approaches rely on more elaborate constitutive equations. So there is no direct application of the results presented here to real flow conditions. Yet, our study sheds light on the mechanisms involved in basal entrainment. We provide evidence that the whole layer of loose material is entrained quickly once the flow makes contact with the erodible layer. As this process occurs
Biodegradation of Microcystins during Gravity-Driven Membrane (GDM) Ultrafiltration
Kohler, Esther; Villiger, Jörg; Posch, Thomas; Derlon, Nicolas; Shabarova, Tanja; Morgenroth, Eberhard; Pernthaler, Jakob; Blom, Judith F.
2014-01-01
Gravity-driven membrane (GDM) ultrafiltration systems require little maintenance: they operate without electricity at ultra-low pressure in dead-end mode and without control of the biofilm formation. These systems are already in use for water purification in some regions of the world where adequate treatment and distribution of drinking water is not readily available. However, many water bodies worldwide exhibit harmful blooms of cyanobacteria that severely lower the water quality due to the production of toxic microcystins (MCs). We studied the performance of a GDM system during an artificial Microcystis aeruginosa bloom in lake water and its simulated collapse (i.e., the massive release of microcystins) over a period of 21 days. Presence of live or destroyed cyanobacterial cells in the feed water decreased the permeate flux in the Microcystis treatments considerably. At the same time, the microbial biofilms on the filter membranes could successfully reduce the amount of microcystins in the filtrate below the critical threshold concentration of 1 µg L−1 MC for human consumption in three out of four replicates after 15 days. We found pronounced differences in the composition of bacterial communities of the biofilms on the filter membranes. Bacterial genera that could be related to microcystin degradation substantially enriched in the biofilms amended with microcystin-containing cyanobacteria. In addition to bacteria previously characterized as microcystin degraders, members of other bacterial clades potentially involved in MC degradation could be identified. PMID:25369266
Noncommutative minisuperspace, gravity-driven acceleration, and kinetic inflation
NASA Astrophysics Data System (ADS)
Rasouli, S. M. M.; Moniz, Paulo Vargas
2014-10-01
In this paper, we introduce a noncommutative version of the Brans-Dicke (BD) theory and obtain the Hamiltonian equations of motion for a spatially flat Friedmann-Lemaître-Robertson-Walker universe filled with a perfect fluid. We focus on the case where the scalar potential as well as the ordinary matter sector are absent. Then, we investigate gravity-driven acceleration and kinetic inflation in this noncommutative BD cosmology. In contrast to the commutative case, in which the scale factor and BD scalar field are in a power-law form, in the noncommutative case the power-law scalar factor is multiplied by a dynamical exponential warp factor. This warp factor depends on the noncommutative parameter as well as the momentum conjugate associated to the BD scalar field. We show that the BD scalar field and the scale factor effectively depend on the noncommutative parameter. For very small values of this parameter, we obtain an appropriate inflationary solution, which can overcome problems within BD standard cosmology in a more efficient manner. Furthermore, a graceful exit from an early acceleration epoch towards a decelerating radiation epoch is provided. For late times, due to the presence of the noncommutative parameter, we obtain a zero acceleration epoch, which can be interpreted as the coarse-grained explanation.
Biodegradation of microcystins during gravity-driven membrane (GDM) ultrafiltration.
Kohler, Esther; Villiger, Jörg; Posch, Thomas; Derlon, Nicolas; Shabarova, Tanja; Morgenroth, Eberhard; Pernthaler, Jakob; Blom, Judith F
2014-01-01
Gravity-driven membrane (GDM) ultrafiltration systems require little maintenance: they operate without electricity at ultra-low pressure in dead-end mode and without control of the biofilm formation. These systems are already in use for water purification in some regions of the world where adequate treatment and distribution of drinking water is not readily available. However, many water bodies worldwide exhibit harmful blooms of cyanobacteria that severely lower the water quality due to the production of toxic microcystins (MCs). We studied the performance of a GDM system during an artificial Microcystis aeruginosa bloom in lake water and its simulated collapse (i.e., the massive release of microcystins) over a period of 21 days. Presence of live or destroyed cyanobacterial cells in the feed water decreased the permeate flux in the Microcystis treatments considerably. At the same time, the microbial biofilms on the filter membranes could successfully reduce the amount of microcystins in the filtrate below the critical threshold concentration of 1 µg L(-1) MC for human consumption in three out of four replicates after 15 days. We found pronounced differences in the composition of bacterial communities of the biofilms on the filter membranes. Bacterial genera that could be related to microcystin degradation substantially enriched in the biofilms amended with microcystin-containing cyanobacteria. In addition to bacteria previously characterized as microcystin degraders, members of other bacterial clades potentially involved in MC degradation could be identified.
Gravity-Driven Thin Film Flow of an Ellis Fluid.
Kheyfets, Vitaly O; Kieweg, Sarah L
2013-12-01
The thin film lubrication approximation has been studied extensively for moving contact lines of Newtonian fluids. However, many industrial and biological applications of the thin film equation involve shear-thinning fluids, which often also exhibit a Newtonian plateau at low shear. This study presents new numerical simulations of the three-dimensional (i.e. two-dimensional spreading), constant-volume, gravity-driven, free surface flow of an Ellis fluid. The numerical solution was validated with a new similarity solution, compared to previous experiments, and then used in a parametric study. The parametric study centered around rheological data for an example biological application of thin film flow: topical drug delivery of anti-HIV microbicide formulations, e.g. hydroxyethylcellulose (HEC) polymer solutions. The parametric study evaluated how spreading length and front velocity saturation depend on Ellis parameters. A lower concentration polymer solution with smaller zero shear viscosity (η0), τ1/2, and λ values spread further. However, when comparing any two fluids with any possible combinations of Ellis parameters, the impact of changing one parameter on spreading length depends on the direction and magnitude of changes in the other two parameters. In addition, the isolated effect of the shear-thinning parameter, λ, on the front velocity saturation depended on τ1/2. This study highlighted the relative effects of the individual Ellis parameters, and showed that the shear rates in this flow were in both the shear-thinning and plateau regions of rheological behavior, emphasizing the importance of characterizing the full range of shear-rates in rheological measurements. The validated numerical model and parametric study provides a useful tool for future steps to optimize flow of a fluid with rheological behavior well-described by the Ellis constitutive model, in a range of industrial and biological applications.
Fortunato, Luca; Jeong, Sanghyun; Wang, Yiran; Behzad, Ali R; Leiknes, TorOve
2016-12-01
Fouling in membrane bioreactors (MBR) is acknowledged to be complex and unclear. An integrated characterization methodology was employed in this study to understand the fouling on a gravity-driven submerged MBR (GD-SMBR). It involved the use of different analytical tools, including optical coherence tomography (OCT), liquid chromatography with organic carbon detection (LC-OCD), total organic carbon (TOC), flow cytometer (FCM), adenosine triphosphate analysis (ATP) and scanning electron microscopy (SEM). The three-dimensional (3D) biomass morphology was acquired in a real-time through non-destructive and in situ OCT scanning of 75% of the total membrane surface directly in the tank. Results showed that the biomass layer was homogeneously distributed on the membrane surface. The amount of biomass was selectively linked with final destructive autopsy techniques. The LC-OCD analysis indicated the abundance of low molecular weight (LMW) organics in the fouling composition. Three different SEM techniques were applied to investigate the detailed fouling morphology on the membrane. Copyright © 2016 Elsevier Ltd. All rights reserved.
Diffusive smoothing of surfzone bathymetry by gravity-driven sediment transport
NASA Astrophysics Data System (ADS)
Moulton, M. R.; Elgar, S.; Raubenheimer, B.
2012-12-01
Gravity-driven sediment transport often is assumed to have a small effect on the evolution of nearshore morphology. Here, it is shown that down-slope gravity-driven sediment transport is an important process acting to smooth steep bathymetric features in the surfzone. Gravity-driven transport can be modeled as a diffusive term in the sediment continuity equation governing temporal (t) changes in bed level (h): ∂h/∂t ≈ κ ▽2h, where κ is a sediment diffusion coefficient that is a function of the bed shear stress (τb) and sediment properties, such as the grain size and the angle of repose. Field observations of waves, currents, and the evolution of large excavated holes (initially 10-m wide and 2-m deep, with sides as steep as 35°) in an energetic surfzone are consistent with diffusive smoothing by gravity. Specifically, comparisons of κ estimated from the measured bed evolution with those estimated with numerical model results for several transport theories suggest that gravity-driven sediment transport dominates the bed evolution, with κ proportional to a power of τb. The models are initiated with observed bathymetry and forced with observed waves and currents. The diffusion coefficients from the measurements and from the model simulations were on average of order 10-5 m2/s, implying evolution time scales of days for features with length scales of 10 m. The dependence of κ on τb varies for different transport theories and for high and low shear stress regimes. The US Army Corps of Engineers Field Research Facility, Duck, NC provided excellent logistical support. Funded by a National Security Science and Engineering Faculty Fellowship, a National Defense Science and Engineering Graduate Fellowship, and the Office of Naval Research.
The moving-boundary approach for modeling gravity-driven stable and unstable flow in soils
NASA Astrophysics Data System (ADS)
Brindt, Naaran; Wallach, Rony
2017-01-01
The Richards equation is unsuccessful at describing gravity-driven unstable flow with nonmonotonic water content distribution. This shortcoming is resolved in the current study by introducing the moving-boundary approach. Following this approach, the flow domain is divided into two subdomains with a sharp change in fluid saturation between them (moving boundary). The upper subdomain consists of water and air, whose relationship varies with space and time following the imposed boundary condition at the soil surface calculated by the Richards equation. The lower subdomain consists of an initially dry soil that remains constant. The location of the boundary between the two subdomains is part of the solution, rendering the problem nonlinear. The moving boundary solution was used after verification to demonstrate the effect of contact angle, soil characteristic curves and incoming flux on the dynamic water-entry pressure of the soil, which depends on the soil's wettability, incoming flux at the soil surface and the wetting front's propagation rate. Lower soil wettability hinders spontaneous invasion of the dry pores and, together with a higher input flux, induces water accumulation behind the wetting front (saturation overshoot). The wetting front starts to propagate once the pressure building up behind it exceeds the dynamic water-entry pressure. To conclude, the physically based novel moving-boundary approach for solving stable and gravity-driven unstable flow in soils was developed and verified. It supports the conjecture that saturation overshoot is a prerequisite for gravity-driven fingering.
The moving boundary approach to modeling gravity-driven stable and unstable flow in soils
NASA Astrophysics Data System (ADS)
Brindt, Naaran; Wallach, Rony
2016-04-01
Many field and laboratory studies in the last 40 years have found that water flow in homogeneous soil profiles may occur in preferential flow pathways rather than in a laterally uniform wetting front, as expected from classical soil physics theory and expressed by the Richards equation. The water-content distribution within such gravity-driven fingers was found to be nonmonotonic due to water accumulation behind a sharp wetting front (denoted as saturation overshoot). The unstable flow was first related to soil coarseness. However, its appearance in water-repellent soils led the authors to hypothesize that gravity-driven unstable flow formation is triggered by a non-zero contact angle between water and soil particles. Despite its widespread occurrence, a macroscopic-type model describing the nonmonotonic water distribution and sharp wetting front is still lacking. The moving boundary approach, which divides the flow domain into two well-defined subdomains with a sharp change in fluid saturation between them, is suggested to replace the classical approach of solving the Richards equation for the entire flow domain. The upper subdomain consists of water and air, whose relationship varies with space and time following the imposed boundary condition at the soil surface as calculated by the Richards equation. The lower subdomain also consists of water and air, but their relationship remains constant following the predetermined initial condition. The moving boundary between the two subdomains is the sharp wetting front, whose location is part of the solution. As such, the problem is inherently nonlinear. The wetting front's movement is controlled by the dynamic water-entry pressure of the soil, which depends on soil wettability and the front's propagation rate. A lower soil wettability, which hinders the spontaneous invasion of dry pores and increases the water-entry pressure, induces a sharp wetting front and water accumulation behind it. The wetting front starts to
Gravity-driven structures and rift basin evolution: Rio Muni Basin, offshore equatorial West Africa
Turner, J.P.
1995-08-01
Offshore Equatorial Guinea, west Africa, gravity-driven nappes, more than 1 km thick and 15 km from head to toe, provide key evidence in reconstructing the late synrift: evolution of this part of the South Atlantic margin basin system. Furthermore, Aptian-Cenomanian carbonate and clastic rocks in the nappes` allochthonous hanging walls are attracting interest as a new exploration play in west Africa. The nappes exhibit a range of geometries that suggest they share many of the same deformation processes as thin-skin thrust and linked extensional fault systems. Not only are these structures significant in their own right, representing a rare example of gravity tectonics in the virtual absence of major halokinesis, but their presence may record an other-wise undetectable process active during the transition from a rift basin to a passive continental margin. A review of Equatorial Guinea in its pre-Atlantic configuration, alongside neighboring basins in Brazil (the Sergipe-Alagoas basin) and Gabon, suggests that gravity gliding was sustained by a relatively steep, westward paleoslope promoted by east-ward offset of the locus of thermal uplift from the rift basin (i.e., a simple shear model of basin formation). In contrast to gravity-driven structures in most postrift settings, the Equatorial Guinea nappes developed at the close of the Aptian-Albian synrift episode in response to a growing bathymetric deep caused by rapid subsidence outpacing restricted sedimentation.
Tang, Xiaomin; Si, Yang; Ge, Jianlong; Ding, Bin; Liu, Lifang; Zheng, Gang; Luo, Wenjing; Yu, Jianyong
2013-12-07
Creating an efficient, cost-effective method that can provide simple, practical and high-throughput separation of oil-water mixtures has proved extremely challenging. This work responds to these challenges by designing, fabricating and evaluating a novel fluorinated polybenzoxazine (F-PBZ) modified nanofibrous membrane optimized to achieve gravity driven oil-water separation. The membrane design is then realized by a facile combination of electrospun poly(m-phenylene isophthalamide) (PMIA) nanofibers and an in situ polymerized F-PBZ functional layer incorporating SiO2 nanoparticles (SiO2 NPs). By employing the F-PBZ/SiO2 NP modification, the pristine hydrophilic PMIA nanofibrous membranes are endowed with promising superhydrophobicity with a water contact angle of 161° and superoleophilicity with an oil contact angle of 0°. This new membrane shows high thermal stability (350 °C) and good repellency to hot water (80 °C), and achieves an excellent mechanical strength of 40.8 MPa. Furthermore, the as-prepared membranes exhibited fast and efficient separation of oil-water mixtures by a solely gravity driven process, which makes them good candidates for industrial oil-polluted water treatments and oil spill cleanup, and also provided new insights into the design and development of functional nanofibrous membranes through F-PBZ modification.
ELIASSI,MEHDI; GLASS JR.,ROBERT J.
2000-03-08
The authors consider the ability of the numerical solution of Richards equation to model gravity-driven fingers. Although gravity-driven fingers can be easily simulated using a partial downwind averaging method, they find the fingers are purely artificial, generated by the combined effects of truncation error induced oscillations and capillary hysteresis. Since Richards equation can only yield a monotonic solution for standard constitutive relations and constant flux boundary conditions, it is not the valid governing equation to model gravity-driven fingers, and therefore is also suspect for unsaturated flow in initially dry, highly nonlinear, and hysteretic media where these fingers occur. However, analysis of truncation error at the wetting front for the partial downwind method suggests the required mathematical behavior of a more comprehensive and physically based modeling approach for this region of parameter space.
NASA Astrophysics Data System (ADS)
Guémas, Marine; Sellier, Antoine; Pigeonneau, Franck
2015-04-01
The axisymmetric gravity-driven dynamics of a bubble rising toward a free surface is addressed for gas-liquid interfaces having unequal surface tensions. The liquid flow is governed by the Stokes equations which are here solved using a boundary element method in axisymmetric configuration. Within this framework, two dimensionless numbers arise: the Bond number Bo1 based on the surface tension of the bubble interface and the surface tension ratio γ ˆ comparing the free surface and bubble surface tensions. Under a careful and discussed selection of the code key settings (number of boundary elements, initial bubble location, and distance beyond which the free surface is truncated), it has been possible to numerically and accurately track in time the bubble and free surface shapes for several values of ( Bo 1 , γ ˆ ) . The long-time shapes are found to deeply depend upon both Bo1 and γ ˆ and also to compare well with the shapes predicted in Princen and Mason ["Shape of a fluid drop at a fluid-liquid interface. II. Theory for three-phase systems," J. Colloid. Sci. 20, 246-266 (1965)] using a hydrostatic model in which both surfaces are touching. Similarly, the drainage dynamics of the liquid film thickness between the bubble and the free surface depends on ( Bo 1 , γ ˆ ) . The long-time film thickness exponentially decays in time and a so-called thinning rate α for which the numerical behaviors and a simple model reveal two basic behaviors: (i) at small Bond number, α behaves as 1/Bo1 and (ii) at large Bond number, α is nearly constant. In addition, it is found that in the entire range of the quantity χ = ( 1 + γ ˆ ) Bo 1 / ( 2 γ ˆ ) , the thinning rate α is well approximated by the function 1/(18χ) + α∞ with α∞ ≈ 0.158. Such a result also permits one to estimate the typical drainage time versus the initial bubble radius a, the liquid density ρ and viscosity μ, the gravity and the free surface, and bubble surface tensions.
Experimental and Numerical Investigation of Gravity-Driven Pipe Flow With Cavitation
Giese, Tobias; Laurien, Eckart; Schwarz, Wolfgang
2002-07-01
Gravity driven pipe flows contain no risk of pump failure and are considered to be reliable even under accident conditions. However, accurate prediction methods are only available for single phase flow. In case of the occurrence of two-phase flow (caused e.g. by boiling or cavitation), a considerable reduction in mass flux can be observed. In this study, an experimental and numerical investigation of gravity driven two-phase pipe flow was performed in order to understand and model such flows. An experiment was conducted to analyse gravity driven flow of water near saturation temperature in a complex pipe consisting of several vertical and horizontal sections. The diameter was 100 mm with a driving height of 13 m between an elevated tank and the pipe outlet. The experiment shows that cavitation leads to formation of steam. The two-phase character of the flow causes a significant reduction of mass flux in comparison to a single phase flow case. The experimental flow rate was reproduced by one dimensional single and two phase flow analysis based on standard one dimensional methods including models for steam formation. The main part of this study consists of a three dimensional CFD analysis of the two phase flow. A three dimensional model for cavitation and recondensation phenomena based on thermal transport processes was developed, implemented and validated against our experimental data. Due to the fact that beside bubbly flow, also the stratified and droplet flow regimes occur, a new approach to model phase interaction terms of the Two-Fluid Model for mass, momentum and energy is presented. Thereby, the transition from one flow regime to another is taken into account. The experimental mass flow rate can be predicted with an accuracy of 10%. The three dimensional analysis of the flow situation demonstrates the influence of pipe elements such as horizontal and vertical sections, bends and valves of the pipe on the mass flux and the steam distribution. The analysis of
Du, Wen-Bin; Fang, Qun; He, Qiao-Hong; Fang, Zhao-Lun
2005-03-01
In this work, a simple, robust, and automated microfluidic chip-based FIA system with gravity-driven flows and liquid-core waveguide (LCW) spectrometric detection was developed. The high-throughput sample introduction system was composed of a capillary sampling probe and an array of horizontally positioned microsample vials with a slot fabricated on the bottom of each vial. FI sample loading and injection were performed by linearly moving the array of vials filled alternately with 50-microL samples and carrier, allowing the probe inlet to enter the solutions in the vials through the slots sequentially and the sample and carrier solution to be introduced into the chip driven by gravity. The performance of the system was demonstrated using the complexation of o-phenanthroline with Fe(II) as a model reaction. A 20-mm-long Teflon AF 2400 capillary (50-microm i.d., 375-microm o.d.) was connected to the chip to function as a LCW detection flow cell with a cell volume of 40 nL and effective path length of 1.7 cm. Linear absorbance response was obtained in the range of 1.0-100 microM Fe(II) (r2=0.9967), and a good reproducibility of 0.6% RSD (n=18) was achieved. The sensitivity was comparable with that obtained using conventional FIA systems, which typically consume 10,000-fold more sample. The highest sampling throughput of 1000 h-1 was obtained by using injection times of 0.08 and 3.4 s for sample and carrier solution, respectively, with a sample consumption of only 0.6 nL for each cycle.
A discontinuous Galerkin method for gravity-driven viscous fingering instabilities in porous media
Scovazzi, G.; Gerstenberger, A.; Collis, S. S.
2013-01-01
We present a new approach to the simulation of gravity-driven viscous fingering instabilities in porous media flow. These instabilities play a very important role during carbon sequestration processes in brine aquifers. Our approach is based on a nonlinear implementation of the discontinuous Galerkin method, and possesses a number of key features. First, the method developed is inherently high order, and is therefore well suited to study unstable flow mechanisms. Secondly, it maintains high-order accuracy on completely unstructured meshes. The combination of these two features makes it a very appealing strategy in simulating the challenging flow patterns and very complex geometries of actual reservoirs and aquifers. This article includes an extensive set of verification studies on the stability and accuracy of the method, and also features a number of computations with unstructured grids and non-standard geometries.
NASA Astrophysics Data System (ADS)
Tang, Xiaomin; Si, Yang; Ge, Jianlong; Ding, Bin; Liu, Lifang; Zheng, Gang; Luo, Wenjing; Yu, Jianyong
2013-11-01
Creating an efficient, cost-effective method that can provide simple, practical and high-throughput separation of oil-water mixtures has proved extremely challenging. This work responds to these challenges by designing, fabricating and evaluating a novel fluorinated polybenzoxazine (F-PBZ) modified nanofibrous membrane optimized to achieve gravity driven oil-water separation. The membrane design is then realized by a facile combination of electrospun poly(m-phenylene isophthalamide) (PMIA) nanofibers and an in situ polymerized F-PBZ functional layer incorporating SiO2 nanoparticles (SiO2 NPs). By employing the F-PBZ/SiO2 NP modification, the pristine hydrophilic PMIA nanofibrous membranes are endowed with promising superhydrophobicity with a water contact angle of 161° and superoleophilicity with an oil contact angle of 0°. This new membrane shows high thermal stability (350 °C) and good repellency to hot water (80 °C), and achieves an excellent mechanical strength of 40.8 MPa. Furthermore, the as-prepared membranes exhibited fast and efficient separation of oil-water mixtures by a solely gravity driven process, which makes them good candidates for industrial oil-polluted water treatments and oil spill cleanup, and also provided new insights into the design and development of functional nanofibrous membranes through F-PBZ modification.Creating an efficient, cost-effective method that can provide simple, practical and high-throughput separation of oil-water mixtures has proved extremely challenging. This work responds to these challenges by designing, fabricating and evaluating a novel fluorinated polybenzoxazine (F-PBZ) modified nanofibrous membrane optimized to achieve gravity driven oil-water separation. The membrane design is then realized by a facile combination of electrospun poly(m-phenylene isophthalamide) (PMIA) nanofibers and an in situ polymerized F-PBZ functional layer incorporating SiO2 nanoparticles (SiO2 NPs). By employing the F-PBZ/SiO2 NP
Model for density waves in gravity-driven granular flow in narrow pipes.
Ellingsen, Simen A; Gjerden, Knut S; Grøva, Morten; Hansen, Alex
2010-06-01
A gravity-driven flow of grains through a narrow pipe in vacuum is studied by means of a one-dimensional model with two coefficients of restitution. Numerical simulations show clearly how density waves form when a strikingly simple criterion is fulfilled: that dissipation due to collisions between the grains and the walls of the pipe is greater per collision than that which stems from collisions between particles. Counterintuitively, the highest flow rate is observed when the number of grains per density wave grows large. We find strong indication that the number of grains per density wave always approaches a constant as the particle number tends to infinity, and that collapse to a single wave, which was often observed also in previous simulations, occurs because the number of grains is insufficient for multiple wave formation.
Gravity-driven granular flow in a silo: Characterizing local forces and rearrangements
NASA Astrophysics Data System (ADS)
Thackray, Emma; Nordstrom, Kerstin
2017-06-01
While the gravity-driven flow of a granular material in a silo geometry can be modeled by the Beverloo equation, the mesoscale-level particle rearrangements and interactions that drive this flow are not wellunderstood. We have constructed a quasi-two-dimensional system of bidisperse, millimeter-scale disks with photoelastic properties that make force networks within the material visible. The system is contained in an acrylic box with an adjustable bottom opening. We can approach the clogging transition by adjusting this opening. By placing the system between cross-polarizers, we can obtain high-speed video of this system during flow, and extract intensity signals that can be used to identify and quantify localized, otherwise indeterminate forces. We can simultaneously track individual particle motions, which can be used to identify shear transformation zones in the system. In this paper, we present our results thus far.
A discontinuous Galerkin method for gravity-driven viscous fingering instabilities in porous media
NASA Astrophysics Data System (ADS)
Scovazzi, G.; Gerstenberger, A.; Collis, S. S.
2013-01-01
We present a new approach to the simulation of gravity-driven viscous fingering instabilities in porous media flow. These instabilities play a very important role during carbon sequestration processes in brine aquifers. Our approach is based on a nonlinear implementation of the discontinuous Galerkin method, and possesses a number of key features. First, the method developed is inherently high order, and is therefore well suited to study unstable flow mechanisms. Secondly, it maintains high-order accuracy on completely unstructured meshes. The combination of these two features makes it a very appealing strategy in simulating the challenging flow patterns and very complex geometries of actual reservoirs and aquifers. This article includes an extensive set of verification studies on the stability and accuracy of the method, and also features a number of computations with unstructured grids and non-standard geometries.
NASA Astrophysics Data System (ADS)
Xue, Liang; Wang, Shouyu; Yan, Keding; Sun, Nan; Ferraro, Pietro; Li, Zhenhua; Liu, Fei
2014-04-01
Phase distribution detection of cells and tissues is concerned since it is an important auxiliary method for observing biological samples. High speed and large amount cell detection is needed for its high detecting efficiency. In this paper, we have proposed a simple large scale biological sample phase detection device called gravity driven high throughput phase detecting cytometer based on quantitative interferometric microscopy to obtain flowing red blood cells phase. The system could realize high throughput phase detecting and statistical analysis with high detecting speed and in real time. The statistical characteristics of red blood cells could be obtained which might be helpful for biological analysis and disease detection. We believe this method is a powerful tool to quantitatively measure the phase distribution of biological samples.
Estuarine sediment transport by gravity-driven movement of the nepheloid layer, Long Island Sound
NASA Astrophysics Data System (ADS)
Poppe, L. J.; McMullen, K. Y.; Williams, S. J.; Crocker, J. M.; Doran, E. F.
2008-08-01
Interpretation of sidescan-sonar imagery provides evidence that down-slope gravity-driven movement of the nepheloid layer constitutes an important mode of transporting sediment into the basins of north-central Long Island Sound, a major US East Coast estuary. In the Western Basin, this transport mechanism has formed dendritic drainage systems characterized by branching patterns of low backscatter on the seafloor that exceed 7.4 km in length and progressively widen down-slope, reaching widths of over 0.6 km at their southern distal ends. Although much smaller, dendritic patterns of similar morphology are also present in the northwestern part of the Central Basin. Because many contaminants display affinities for adsorption onto fine-grained sediments, and because the Sound is affected by seasonal hypoxia, mechanisms and dispersal pathways by which inorganic and organic sediments are remobilized and transported impact the eventual fate of the contaminants and environmental health of the estuary.
Estuarine sediment transport by gravity-driven movement of the nepheloid layer, Long Island Sound
Poppe, L.J.; McMullen, K.Y.; Williams, S.J.; Crocker, J.M.; Doran, E.F.
2008-01-01
Interpretation of sidescan-sonar imagery provides evidence that down-slope gravity-driven movement of the nepheloid layer constitutes an important mode of transporting sediment into the basins of north-central Long Island Sound, a major US East Coast estuary. In the Western Basin, this transport mechanism has formed dendritic drainage systems characterized by branching patterns of low backscatter on the seafloor that exceed 7.4 km in length and progressively widen down-slope, reaching widths of over 0.6 km at their southern distal ends. Although much smaller, dendritic patterns of similar morphology are also present in the northwestern part of the Central Basin. Because many contaminants display affinities for adsorption onto fine-grained sediments, and because the Sound is affected by seasonal hypoxia, mechanisms and dispersal pathways by which inorganic and organic sediments are remobilized and transported impact the eventual fate of the contaminants and environmental health of the estuary. ?? Springer-Verlag 2008.
Drop formation in non-Newtonian fluids.
Aytouna, Mounir; Paredes, Jose; Shahidzadeh-Bonn, Noushine; Moulinet, Sébastien; Wagner, Christian; Amarouchene, Yacine; Eggers, Jens; Bonn, Daniel
2013-01-18
We study the pinch-off dynamics of droplets of yield stress and shear thinning fluids. To separate the two non-Newtonian effects, we use a yield stress material for which the yield stress can be tuned without changing the shear thinning behavior, and a shear thinning system (without a yield stress) for which the shear thinning can be controlled over a large range, without introducing too much elasticity into the system. We find that the pinch-off remains very similar to that of constant viscosity Newtonian liquids, and consequently thinning in shear flow does not imply a thinning in elongational flow.
Coupled capillary and gravity-driven instability in a liquid film overlying a porous layer
NASA Astrophysics Data System (ADS)
Desaive, Th.; Lebon, G.; Hennenberg, M.
2001-12-01
In this work, we study the problem of onset of thermal convection in a fluid layer overlying a porous layer, the whole system being heated from below. We use Brinkman's model to describe the porous medium and determine the corresponding linear stability equations. The eigenvalue problem is solved by means of a modified Galerkin method. The behavior of the critical wave number and temperature gradient is discussed in terms of the various parameters of the system. We also emphasize the influence of the boundary conditions at the upper surface of the fluid layer; in particular, we examine the role of a free surface whose surface tension is temperature dependent (Marangoni effect). Comparison with earlier works is also made.
NASA Astrophysics Data System (ADS)
Botella, Olivier; Ait-Messaoud, Mazigh; Pertat, Adrien; Cheny, Yoann; Rigal, Claire
2015-04-01
This paper presents the extension of a well-established immersed boundary/cut-cell method, the LS-STAG method (Cheny and Botella in J Comput Phys 229:1043-1076, 2010), to non-Newtonian flow computations in 2D irregular geometries. One of the distinguished features of our IB method is to use level-set techniques in the cut-cells near the irregular boundary, where accurate discretization is of paramount importance for stability and accuracy of the computations. For this purpose, we present here an accurate discretization of the velocity gradients and shear rate in the cut-cells that fits elegantly in the framework of the velocity-pressure-stress staggered arrangement and the special quadratures developed previously for viscoelastic flows. After assessing the accuracy of the discretization on a benchmark solution for power-law fluids, the LS-STAG code is applied to the flow of various shear-thinning xanthan solutions in a wide-gap, non-coaxial, Taylor-Couette reactor for which rheological characterization, experimental flow measurements (PIV) and FLUENT simulations have recently been performed in our group. Our numerical investigation will give new insight on the flow patterns (onset, size and position of the recirculation zone) and will firmly correlate them to global flow properties such as shear-thinning index, generalized Reynolds number and torque ratio at the cylinders.
Modeling gravity-driven fingering in rough-walled fractures using modified percolation theory
Glass, R.J.
1992-12-31
Pore scale invasion percolation theory is modified for imbibition of.wetting fluids into fractures. The effects of gravity, local aperture field geometry, and local in-plane air/water interfacial curvatureare included in the calculation of aperture filling potential which controls wetted structure growth within the fracture. The inclusion of gravity yields fingers oriented in the direction of the gravitational gradient. These fingers widen and tend to meander and branch more as the gravitational gradient decreases. In-plane interfacial curvature also greatly affects the wetted structure in both horizontal and nonhorizontal fractures causing the formation of macroscopic wetting fronts. The modified percolation model is used to simulate imbibition into an analogue rough-walled fracture where both fingering and horizontal imbibition experiments were previously conducted. Comparison of numerical and experimental results showed reasonably good agreement. This process oriented physical and numerical modeling is-a necessary step toward including gravity-driven fingering in models of flow and transport through unsaturated, fractured rock.
Mauduit, T.; Gwenael G.; Brun, J.P.
1995-08-01
The West African Margin, (Gulf of Guinea) presents spectacular examples of gravity driven deformation above a salt decollement (i.e. growth faulting, rafts, diapirs and contractional structures) which have been documented by numerous Oil and Gas investigations. Seismic data demonstrate that the variation of deformation styles in space and time appear to be function of: regional geometry of the margin (i.e. value of basal slope and presence/absence of residual reliefs below the salt layers) and, mode, rate and repartition of sedimentation. The role and effects of the above parameters were analyzed using laboratory modeling investigation based on basic structural patterns identified through seismic data. Models are built with sand and silicone putty, that respectively represent the frictional behavior of upper Cretaceous-Cenozoic cover and the viscous behavior of the upper Aptian salt. They are scaled to fit observed natural configurations. Results are compared with examples from the Gulf of Guinea on the basis of seismic data. This approach allowed to better understand the evolution of the margin and therefore the reservoir distributions and traps geometries.
Gravity-Driven Acceleration and Kinetic Inflation in Noncommutative Brans-Dicke Setting
NASA Astrophysics Data System (ADS)
Rasouli, S. M. M.; Vargas Moniz, Paulo
By assuming the spatially flat FLRW line-element and employing the Hamiltonian formalism, a noncommutative (NC) setting of the Brans-Dicke (BD) theory is introduced. We investigate gravity-driven acceleration and kinetic inflation in this NC BD cosmology. Despite to the commutative case, in which both the scale factor and BD scalar field are obtained in power-law forms (in terms of the cosmic time), in our herein NC model, we see that the power-law scalar factor is multiplied by a dynamical exponential warp factor. This warp factor depends on not only the noncommutative parameter but also the momentum conjugate associated to the BD scalar field. For very small values of this parameter, we obtain an appropriate inflationary solution, which can overcome problems within standard BD cosmology in a more efficient manner. Moreover, we see that a graceful exit from an early acceleration epoch towards a decelerating radiation epoch is provided. For late times, due to the presence of the NC parameter, we obtain a zero acceleration epoch, which can be interpreted as the coarse-grained explanation.
NASA Technical Reports Server (NTRS)
Zoutendyk, J. A.; Akutagawa, W. M.
1982-01-01
Experimental results are summarized, and it is pointed out that gravity-driven convection can alter the diffusive-advective mass transport behavior in the growth of crystals by physical vapor transport. Specially designed and constructed transparent furnaces are described which are being used to study the effects of gravity in the crystal growth of the compound semiconductors PbTe and CdTe. The theory underlying vapor transport behavior is reviewed, with attention given to the vapor-solid behavior of compound materials, to one-dimensional mass transport, and to gravity-induced (natural) convection. In the transparent furnaces, the quartz capillary tube mounted along the axis of the main quartz ampoule is used to measure the temperature at the growth surface (vapor-solid crystal interface) and the source, as well as the complete temperature profile along the axis of the tube. The light-pipe works to remove heat from the growth end of the ampoule by radiative heat transfer. The ampoules are sealed after being evacuated to the low 10 to the -8th torr range with a cryogenic vacuum pump.
Comparative study of disinfectants for use in low-cost gravity driven household water purifiers.
Patil, Rajshree A; Kausley, Shankar B; Balkunde, Pradeep L; Malhotra, Chetan P
2013-09-01
Point-of-use (POU) gravity-driven household water purifiers have been proven to be a simple, low-cost and effective intervention for reducing the impact of waterborne diseases in developing countries. The goal of this study was to compare commonly used water disinfectants for their feasibility of adoption in low-cost POU water purifiers. The potency of each candidate disinfectant was evaluated by conducting a batch disinfection study for estimating the concentration of disinfectant needed to inactivate a given concentration of the bacterial strain Escherichia coli ATCC 11229. Based on the concentration of disinfectant required, the size, weight and cost of a model purifier employing that disinfectant were estimated. Model purifiers based on different disinfectants were compared and disinfectants which resulted in the most safe, compact and inexpensive purifiers were identified. Purifiers based on bromine, tincture iodine, calcium hypochlorite and sodium dichloroisocyanurate were found to be most efficient, cost effective and compact with replacement parts costing US$3.60-6.00 for every 3,000 L of water purified and are thus expected to present the most attractive value proposition to end users.
NASA Astrophysics Data System (ADS)
Ripepe, Maurizio; Donne, Dario Delle; Genco, Riccardo; Maggio, Giuseppe; Pistolesi, Marco; Marchetti, Emanuele; Lacanna, Giorgio; Ulivieri, Giacomo; Poggi, Pasquale
2015-05-01
Effusive eruptions are explained as the mechanism by which volcanoes restore the equilibrium perturbed by magma rising in a chamber deep in the crust. Seismic, ground deformation and topographic measurements are compared with effusion rate during the 2007 Stromboli eruption, drawing an eruptive scenario that shifts our attention from the interior of the crust to the surface. The eruption is modelled as a gravity-driven drainage of magma stored in the volcanic edifice with a minor contribution of magma supplied at a steady rate from a deep reservoir. Here we show that the discharge rate can be predicted by the contraction of the volcano edifice and that the very-long-period seismicity migrates downwards, tracking the residual volume of magma in the shallow reservoir. Gravity-driven magma discharge dynamics explain the initially high discharge rates observed during eruptive crises and greatly influence our ability to predict the evolution of effusive eruptions.
Ripepe, Maurizio; Donne, Dario Delle; Genco, Riccardo; Maggio, Giuseppe; Pistolesi, Marco; Marchetti, Emanuele; Lacanna, Giorgio; Ulivieri, Giacomo; Poggi, Pasquale
2015-05-18
Effusive eruptions are explained as the mechanism by which volcanoes restore the equilibrium perturbed by magma rising in a chamber deep in the crust. Seismic, ground deformation and topographic measurements are compared with effusion rate during the 2007 Stromboli eruption, drawing an eruptive scenario that shifts our attention from the interior of the crust to the surface. The eruption is modelled as a gravity-driven drainage of magma stored in the volcanic edifice with a minor contribution of magma supplied at a steady rate from a deep reservoir. Here we show that the discharge rate can be predicted by the contraction of the volcano edifice and that the very-long-period seismicity migrates downwards, tracking the residual volume of magma in the shallow reservoir. Gravity-driven magma discharge dynamics explain the initially high discharge rates observed during eruptive crises and greatly influence our ability to predict the evolution of effusive eruptions.
Richman, M.W.
1992-01-01
In this quarter, we extended our study of the effects of isotropic boundary vibrations to steady, gravity driven, inclined granular flows. These flows are more complex than those considered last quarter because of the presence of slip and mean velocity gradients at the boundary. Consequently, it was first necessary to modify the boundary conditions derived by Richman (1992) to account for corrections to the flow particle velocity distribution function from velocity gradients. In what follows we only summarize the results obtained.
Optimization of gravity-driven membrane (GDM) filtration process for seawater pretreatment.
Wu, Bing; Hochstrasser, Florian; Akhondi, Ebrahim; Ambauen, Noëmi; Tschirren, Lukas; Burkhardt, Michael; Fane, Anthony G; Pronk, Wouter
2016-04-15
Seawater pretreatment by gravity-driven membrane (GDM) filtration at 40 mbar has been investigated. In this system, a beneficial biofilm develops on the membrane that helps to stabilize flux. The effects of membrane type, prefiltration and system configuration on stable flux, biofilm layer properties and dissolved carbon removal were studied. The results show that the use of flat sheet PVDF membranes with pore sizes of 0.22 and 0.45 μm in GDM filtration achieved higher stabilized permeate fluxes (7.3-8.4 L/m(2)h) than that of flat sheet PES 100 kD membranes and hollow fibre PVDF 0.1 μm membranes. Pore constriction and cake filtration were identified as major membrane fouling mechanisms, but their relative contributions varied with filtration time for the various membranes. Compared to raw seawater, prefiltering of seawater with meshes at sizes of 10, 100 and 1000 μm decreased the permeate flux, which was attributed to removal of beneficial eukaryotic populations. Optical coherence tomography (OCT) showed that the porosity of the biofouling layer was more significantly related with permeate flux development rather than its thickness and roughness. To increase the contact time between the biofilm and the dissolved organics, a hybrid biofilm-submerged GDM reactor was evaluated, which displayed significantly higher permeate fluxes than the submerged GDM reactor. Although integrating the biofilm reactor with the membrane system displayed better permeate quality than the GDM filtration cells, it could not effectively reduce dissolved organic substances in the seawater. This may be attributed to the decomposition/degradation of solid organic substances in the feed and carbon fixation by the biofilm. Further studies of the dynamic carbon balance are required.
New early warning system for gravity-driven ruptures based on codetection of acoustic signal
NASA Astrophysics Data System (ADS)
Faillettaz, J.
2016-12-01
Gravity-driven rupture phenomena in natural media - e.g. landslide, rockfalls, snow or ice avalanches - represent an important class of natural hazards in mountainous regions. To protect the population against such events, a timely evacuation often constitutes the only effective way to secure the potentially endangered area. However, reliable prediction of imminence of such failure events remains challenging due to the nonlinear and complex nature of geological material failure hampered by inherent heterogeneity, unknown initial mechanical state, and complex load application (rainfall, temperature, etc.). Here, a simple method for real-time early warning that considers both the heterogeneity of natural media and characteristics of acoustic emissions attenuation is proposed. This new method capitalizes on codetection of elastic waves emanating from microcracks by multiple and spatially separated sensors. Event-codetection is considered as surrogate for large event size with more frequent codetected events (i.e., detected concurrently on more than one sensor) marking imminence of catastrophic failure. Simple numerical model based on a Fiber Bundle Model considering signal attenuation and hypothetical arrays of sensors confirms the early warning potential of codetection principles. Results suggest that although statistical properties of attenuated signal amplitude could lead to misleading results, monitoring the emergence of large events announcing impeding failure is possible even with attenuated signals depending on sensor network geometry and detection threshold. Preliminary application of the proposed method to acoustic emissions during failure of snow samples has confirmed the potential use of codetection as indicator for imminent failure at lab scale. The applicability of such simple and cheap early warning system is now investigated at a larger scale (hillslope). First results of such a pilot field experiment are presented and analysed.
Non-Newtonian flow of bubbly magma in volcanic conduits
NASA Astrophysics Data System (ADS)
Colucci, Simone; Papale, Paolo; Montagna, Chiara Paola
2017-04-01
The dynamics of magma ascent along volcanic conduits towards the Earth's surface affects eruptive styles and contributes to volcanic hazard. The rheology of ascending magmatic mixtures is known to play a major role on mass flow rate as well as on pressure and exit velocity at the vent, even determining effusive vs explosive eruptive behaviour. In this work we explore the effects of bubble-induced non-Newtonian rheology on the dynamics of magma flow in volcanic conduits. We develop a quasi-2D model of magma ascent that incorporates a rheological constitutive equation describing the strain-dependent effect of gas bubbles on the viscosity of the multiphase magma. Non-Newtonian magma flow is investigated through a parametric study where the viscosity of the melt and the water content are varied over natural ranges. Our results show that non-Newtonian rheology leads to greater exit velocity, mass flow, and density. The pressure distribution along the conduit remains very similar to the Newtonian case, deviating only at the conduit exit. Plug-like velocity profiles develop approaching the conduit exit, when mixture velocity is high, and are favored by smaller liquid viscosity. Since the mass flow rate, the density and the velocity of the mixture exiting from the conduit are fundamental for quantifying and assessing the transport and emplacement dynamics, neglecting the non-Newtonian effect of bubble-bearing magmas may result in misinterpretation of the deposit and, consequently, eruptive behavior.
Non-Newtonian flow of bubbly magma in volcanic conduits
NASA Astrophysics Data System (ADS)
Colucci, S.; Papale, P.; Montagna, C. P.
2017-03-01
The dynamics of magma ascent along volcanic conduits toward the Earth's surface affects eruptive styles and contributes to volcanic hazard. The rheology of ascending magmatic mixtures is known to play a major role on mass flow rate as well as on pressure and exit velocity at the vent, even determining effusive versus explosive eruptive behavior. In this work we explore the effects of bubble-induced non-Newtonian rheology on the dynamics of magma flow in volcanic conduits. We develop a quasi 2-D model of magma ascent that incorporates a rheological constitutive equation describing the strain-dependent effect of gas bubbles on the viscosity of the multiphase magma. Non-Newtonian magma flow is investigated through a parametric study where the viscosity of the melt and the water content are varied over natural ranges. Our results show that non-Newtonian rheology leads to greater exit velocity, mass flow, and density. The pressure distribution along the conduit remains very similar to the Newtonian case, deviating only at the conduit exit. Plug-like velocity profiles develop approaching the conduit exit, when mixture velocity is high, and are favored by smaller liquid viscosity. Since the mass flow rate, the density and the velocity of the mixture exiting from the conduit are fundamental for quantifying and assessing the transport and emplacement dynamics, neglecting that the non-Newtonian effect of bubble-bearing magmas may result in misinterpretation of the deposit and, consequently, eruptive behavior.
Wu, Bing; Christen, Tino; Tan, Hwee Sin; Hochstrasser, Florian; Suwarno, Stanislaus Raditya; Liu, Xin; Chong, Tzyy Haur; Burkhardt, Michael; Pronk, Wouter; Fane, Anthony G
2017-05-01
As a low energy and chemical free process, gravity-driven membrane (GDM) filtration has shown a potential for seawater pretreatment in our previous studies. In this study, a pilot submerged GDM reactor (effective volume of 720 L) was operated over 250 days and the permeate flux stabilized at 18.6 ± 1.4 L/m(2)h at a hydrostatic pressure of 40 mbar. This flux was higher than those in the lab-scale GDM reactor (16.3 ± 0.2 L/m(2)h; effective volume of 8.4 L) and in the filtration cell system (2.7 ± 0.6 L/m(2)h; feed side volume of 0.0046 L) when the same flat sheet membrane was used. Interestingly, when the filtration cell was submerged into the GDM reactor, the flux (17.2 L/m(2)h) was comparable to the submerged membrane module. Analysis of cake layer morphology and foulant properties indicated that a thicker but more porous cake layer with less accumulation of organic substances (biopolymers and humics) contributed to the improved permeate flux. This phenomenon was possibly associated with longer residence time of organic substances and sufficient space for the growth, predation, and movement of the eukaryotes in the GDM reactor. In addition, the permeate flux of the submerged hollow fibre membrane increased with decreasing packing density. It is thought that the movement of large-sized eukaryotes could be limited when the space between hollow fibres was reduced. In terms of pretreatment, the GDM systems effectively removed turbidity, viable cells, and transparent exopolymer particles from the feed seawater. Importantly, extending the reactor operation time produced a permeate with less assimilable organic carbon and biopolymers. Thus, the superior quality of the GDM permeate has the potential to alleviate subsequent reverse osmosis membrane fouling for seawater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.
Seismogenic slump folds formed by gravity-driven tectonics down a negligible subaqueous slope
NASA Astrophysics Data System (ADS)
Alsop, G. Ian; Marco, Shmuel
2013-10-01
The Late Pleistocene Lisan Formation contains superb examples of soft-sediment deformation generated during gravity-driven slumping and failure down extremely gentle (< 1°) slopes towards the palaeo-Dead Sea Basin. Following a previously established framework, portions of individual slumps are broadly categorised into coherent, semi-coherent, and incoherent domains, reflecting increasing deformation and disarticulation of sediment. We present new structural data collected from each of these (overlapping) domains that demonstrate how the orientation of fold hinges and axial planes becomes more dispersed as slumps become increasingly incoherent. Such patterns are the reverse to that typically encountered in lithified rocks where increasing deformation results in clustering of linear elements towards the flow direction, and may reflect greater heterogeneity and disarticulation within slumps. Use of folds to determine palaeoslopes should therefore be limited to those from coherent slumps, where the opportunity for hinge dislocation and rotation is more limited. Within coherent and semi-coherent slumps, folds are reworked to create classic Type 1, 2 and 3 refold patterns during a single progressive deformation perhaps lasting just a matter of minutes. It is noteworthy that slump folds are typically lacking in smaller parasitic folds, implying that instantaneous development and/or limited viscosity contrasts have hindered the formation of second order folds. As deformation intensifies within semi-coherent to incoherent slumps, some fold hinges rotate towards the flow direction to create sheath folds. However, many fold hinges do not rotate into the flow direction, but rather roll downslope to form a new category of spiral folds. Extreme deformation may also generate semi-detached fold trains in which the short limbs of verging fold pairs are relatively thickened resulting in en-echelon X folds. The hinges of the sheared fold pair are reduced to apophyses, although these
NASA Astrophysics Data System (ADS)
Hu, Bin; Kieweg, Sarah
2010-11-01
Gravity-driven thin film flow down an incline is studied for optimal design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. We develop a 3D FEM model using non-Newtonian mechanics to model the flow of gels in response to gravity, surface tension and shear-thinning. Constant volume setup is applied within the lubrication approximation scope. The lengthwise profiles of the 3D model agree with our previous 2D finite difference model, while the transverse contact line patterns of the 3D model are compared to the experiments. With incorporation of surface tension, capillary ridges are observed at the leading front in both 2D and 3D models. Previously published studies show that capillary ridge can amplify the fingering instabilities in transverse direction. Sensitivity studies (2D & 3D) and experiments are carried out to describe the influence of surface tension and shear-thinning on capillary ridge and fingering instabilities.
NASA Technical Reports Server (NTRS)
Yuan, S. W. K.
1985-01-01
This investigation of vapor-liquid phase separation (VLPS) of He 2 is related to long-term storage of cryogenic liquid. The VLPS system utilizes porous plugs in order to generate thermomechanical (thermo-osmotic) force which in turn prevents liquid from flowing out of the cryo-vessel (e.g., Infrared Astronomical Satellite). An apparatus was built and VLPS data were collected for a 2 and a 10 micrometer sintered stainless steel plug and a 5 to 15 micrometer sintered bronze plug. The VLPS data obtained at high temperature were in the nonlinear turbulent regime. At low temperature, the Stokes regime was approached. A turbulent flow model was developed, which provides a phenomenological description of the VLPS data. According to the model, most of the phase separation data are in the turbulent regime. The model is based on concepts of the Gorter-Mellink transport involving the mutual friction known from the zero net mass flow (ZNMF) studies. The latter had to be modified to obtain agreement with the present experimental VLPS evidence. In contrast to the well-known ZNMF mode, the VLPS results require a geometry dependent constant (Gorter-Mellink constant). A theoretical interpretation of the phenomenological equation for the VLPS data obtained, is based on modelling of the dynamics of quantized vortices proposed by Vinen. In extending Vinen's model to the VLPS transport of He 2 in porous media, a correlation between the K*(GM) and K(p) was obtained which permits an interpretation of the present findings. As K(p) is crucial, various methods were introduced to measure the permeability of the porous media at low temperatures. Good agreement was found between the room temperature and the low temperature K(p)-value of the plugs.
Pierce, Eric T; Kumar, Vikram; Zheng, Hui; Peterfreund, Robert A
2013-03-01
Gravity-driven micro-drip infusion sets allow control of medication dose delivery by adjusting drops per minute. When the roller clamp is fully open, flow in the drip chamber can be a continuous fluid column rather than discrete, countable, drops. We hypothesized that during this "wide-open" state, drug delivery becomes dependent on factors extrinsic to the micro-drip set and is therefore difficult to predict. We conducted laboratory experiments to characterize volume delivery under various clinically relevant conditions of wide-open flow in an in vitro laboratory model. A micro-drip infusion set, plugged into a bag of normal saline, was connected to a high-flow stopcock at the distal end. Vertically oriented IV catheters (gauges 14-22) were connected to the stopcock. The fluid meniscus height in the bag was fixed (60-120 cm) above the outflow point. The roller clamp on the infusion set was in fully open position for all experiments resulting in a continuous column of fluid in the drip chamber. Fluid volume delivered in 1 minute was measured 4 times with each condition. To model resistive effects of carrier flow, volumetric infusion pumps were used to deliver various flow rates of normal saline through a carrier IV set into which a micro-drip infusion was "piggybacked." We also compared delivery by micro-drip infusion sets from 3 manufacturers. The volume of fluid delivered by gravity-driven infusion under wide-open conditions (continuous fluid column in drip chamber) varied 2.9-fold (95% confidence interval, 2.84-2.96) depending on catheter size and fluid column height. Total model resistance of the micro-drip with stopcock and catheter varied with flow rate. Volume delivered by the piggybacked micro-drip decreased up to 29.7% ± 0.8% (mean ± SE) as the carrier flow increased from 0 to 1998 mL/min. Delivery characteristics of the micro-drip infusion sets from 3 different manufacturers were similar. Laboratory simulation of clinical situations with gravity-driven
Gbewonyo, K.; Wang, D.I.C.
1983-12-01
The performance of a penicillin fermentation was assessed in a laboratory-scale bubble column fermentor, with mycelial growth confined to the pore matrix of celite beads. Final cell densities of 29 g/L and penicillin titres of 5.5 g/L were obtained in the confined cell cultures. In comparison, cultures of free mycelial cells grown in the absence of beads experienced dissolved oxygen limitations in the bubble column, giving only 17 g/L final cell concentrations with equally low penicillin titres of 2 g/L. The better performance of the confined cell cultures was attributed to enhanced gas liquid mass transfer rates, with mass transfer coefficients (k /SUB L/ a) two to three times higher than those determined in the free cell cultures. Furthermore, the confined cell cultures showed more efficient utilization of power input for mass transfer, providing up to 50% reduction in energy requirements for aeration.
Sarman, Sten Wang, Yong-Lei; Laaksonen, Aatto
2016-02-07
The self-diffusion coefficients of nematic phases of various model systems consisting of regular convex calamitic and discotic ellipsoids and non-convex bodies such as bent-core molecules and soft ellipsoid strings have been obtained as functions of the shear rate in a shear flow. Then the self-diffusion coefficient is a second rank tensor with three different diagonal components and two off-diagonal components. These coefficients were found to be determined by a combination of two mechanisms, which previously have been found to govern the self-diffusion of shearing isotropic liquids, namely, (i) shear alignment enhancing the diffusion in the direction parallel to the streamlines and hindering the diffusion in the perpendicular directions and (ii) the distortion of the shell structure in the liquid whereby a molecule more readily can escape from a surrounding shell of nearest neighbors, so that the mobility increases in every direction. Thus, the diffusion parallel to the streamlines always increases with the shear rate since these mechanisms cooperate in this direction. In the perpendicular directions, these mechanisms counteract each other so that the behaviour becomes less regular. In the case of the nematic phases of the calamitic and discotic ellipsoids and of the bent core molecules, mechanism (ii) prevails so that the diffusion coefficients increase. However, the diffusion coefficients of the soft ellipsoid strings decrease in the direction of the velocity gradient because the broadsides of these molecules are oriented perpendicularly to this direction due the shear alignment (i). The cross coupling coefficient relating a gradient of tracer particles in the direction of the velocity gradient and their flow in the direction of the streamlines is negative and rather large, whereas the other coupling coefficient relating a gradient in the direction of the streamlines and a flow in the direction of the velocity gradient is very small.
NASA Astrophysics Data System (ADS)
Sarman, Sten; Wang, Yong-Lei; Laaksonen, Aatto
2016-02-01
The self-diffusion coefficients of nematic phases of various model systems consisting of regular convex calamitic and discotic ellipsoids and non-convex bodies such as bent-core molecules and soft ellipsoid strings have been obtained as functions of the shear rate in a shear flow. Then the self-diffusion coefficient is a second rank tensor with three different diagonal components and two off-diagonal components. These coefficients were found to be determined by a combination of two mechanisms, which previously have been found to govern the self-diffusion of shearing isotropic liquids, namely, (i) shear alignment enhancing the diffusion in the direction parallel to the streamlines and hindering the diffusion in the perpendicular directions and (ii) the distortion of the shell structure in the liquid whereby a molecule more readily can escape from a surrounding shell of nearest neighbors, so that the mobility increases in every direction. Thus, the diffusion parallel to the streamlines always increases with the shear rate since these mechanisms cooperate in this direction. In the perpendicular directions, these mechanisms counteract each other so that the behaviour becomes less regular. In the case of the nematic phases of the calamitic and discotic ellipsoids and of the bent core molecules, mechanism (ii) prevails so that the diffusion coefficients increase. However, the diffusion coefficients of the soft ellipsoid strings decrease in the direction of the velocity gradient because the broadsides of these molecules are oriented perpendicularly to this direction due the shear alignment (i). The cross coupling coefficient relating a gradient of tracer particles in the direction of the velocity gradient and their flow in the direction of the streamlines is negative and rather large, whereas the other coupling coefficient relating a gradient in the direction of the streamlines and a flow in the direction of the velocity gradient is very small.
NASA Astrophysics Data System (ADS)
Golykh, R. N.
2016-06-01
Progress of technology and medicine dictates the ever-increasing requirements (heat resistance, corrosion resistance, strength properties, impregnating ability, etc.) for non-Newtonian fluids and materials produced on their basis (epoxy resin, coating materials, liquid crystals, etc.). Materials with improved properties obtaining is possible by modification of their physicochemical structure. One of the most promising approaches to the restructuring of non-Newtonian fluids is cavitation generated by high-frequency acoustic vibrations. The efficiency of cavitation in non-Newtonian fluid is determined by dynamics of gaseous bubble. Today, bubble dynamics in isotropic non-Newtonian fluids, in which cavitation bubble shape remains spherical, is most full investigated, because the problem reduces to ordinary differential equation for spherical bubble radius. However, gaseous bubble in anisotropic fluids which are most wide kind of non-Newtonian fluids (due to orientation of macromolecules) deviates from spherical shape due to viscosity dependence on shear rate direction. Therefore, the paper presents the mathematical model of gaseous bubble dynamics in anisotropic non-Newtonian fluids. The model is based on general equations for anisotropic non-Newtonian fluid flow. The equations are solved by asymptotic decomposition of fluid flow parameters. It allowed evaluating bubble size and shape evolution depending on rheological properties of liquid and acoustic field characteristics.
Scarritt, Michelle E; Pashos, Nicholas C; Motherwell, Jessica M; Eagle, Zachary R; Burkett, Brian J; Gregory, Ashley N; Mostany, Ricardo; Weiss, Daniel J; Alvarez, Diego F; Bunnell, Bruce A
2016-12-12
Effective re-endothelialization is critical for the use of decellularized scaffolds for ex vivo lung engineering. Current approaches yield insufficiently re-endothelialized scaffolds that hemorrhage and become thrombogenic upon implantation. Herein, gravity-driven seeding coupled with bioreactor culture facilitated widespread distribution and engraftment of endothelial cells throughout rat lung scaffolds. Initially, human umbilical vein endothelial cells (HUVECs) were seeded into the pulmonary artery by either gravity-driven, variable flow perfusion seeding or pump-driven, pulsatile flow perfusion seeding. Gravity seeding evenly distributed cells and supported cell survival and re-lining of the vascular walls while perfusion pump-driven seeding led to increased cell fragmentation and death. Using gravity seeding, rat pulmonary artery endothelial cells (PAECs) and rat pulmonary vein endothelial cells (PVECs) attached in intermediate and large vessels, while rat pulmonary microvascular endothelial cells (MVECs) deposited mostly in microvessels. Combination seeding of PAECs, PVECs, and MVECs led to positive VE-cadherin staining. In addition, combination seeding improved barrier function as assessed by serum albumin extravasation; however, leakage was observed in the distal portions of the re-endothelialized tissue suggesting that recellularization of the alveoli is necessary to complete barrier function of the capillary-alveolar network. Overall, these data indicate that vascular recellularization of rat lung scaffolds is achieved through gravity seeding. This article is protected by copyright. All rights reserved.
An extension of the Savage-Hutter gravity driven granular flow model on arbitrary topography in 1D
NASA Astrophysics Data System (ADS)
Fellin, Wolfgang; Ostermann, Alexander; Staggl, Gregor
2015-04-01
In an implementation of the Savage-Hutter model in a GIS (geographic information system, e.g. GRASS GIS) curvature terms must be accounted for. We extend the work of Bouchut et al. (2003) to include friction between flowing mass and bed, as well as the active/passive earth pressure coefficient to model the behavior of the granular flow according to the original Savage-Hutter idea. Conservation of mass and momentum in curvilinear coordinates are integrated over the flow height yielding a shallow water model. This work is part of the project avaflow: http://www.avaflow.org/ References: F. Bouchut, A. Mangeney-Castelnau, B. Perthame, J.-P. Vilotte, A new model of Saint Venant and Savage-Hutter type for gravity driven shallow water flows, C.R. Acad. Sci. Paris, série I 336 (2003), 531-536.
NASA Astrophysics Data System (ADS)
Abas, Siti Sabariah; Yatim, Yazariah Mohd
2017-08-01
Rivulet flows occur in a wide range of practical situations ranging from industrial situation such as coating processes to geophysical situation such as lava flow, and extensive efforts have been made to investigate it. In this study, a lubrication approximation is used to investigate the gravity-driven draining of unsteady, slender, symmetric rivulet of Newtonian fluid down an inclined plane, with strong surface-tension effect. A travelling-wave similarity solution is obtained representing a quartic transverse profile rivulet and that it has a uniform thickness at any position x and time t which widen or narrow according to (x - ct)1/4, where c is a velocity of a rivulet and thicken or thin according to a free parameter F0.
The extensional rheology of non-Newtonian materials
NASA Technical Reports Server (NTRS)
Spiegelberg, Stephen H.; Gaudet, Samuel; Mckinley, Gareth H.
1994-01-01
It has been proposed to measure the extensional viscosity function of a non-Newtonian polymer solution in a reduced gravity environment as part of the Advanced Fluid Module. In ground-based extensional measurements, the no-sip boundary condition at solid-fluid interfaces always result in appreciable shear gradients in the test fluid; however the removal of gravitational body forces permits controlled extensional deformation of containerless test samples and the first unambiguous measurements of this kind. Imperative to successful implementation of this experiment is the generation and subsequent deformation of a stable cylindrical column of test fluid. A study of the generation and deformation of liquid bridges demonstrates that Newtonian liquid bridges undergo capillary breakup as anticipated when stretched beyond a critical aspect ratio; non-Newtonian liquid bridges, however, are stabilized by the strain-hardening phenomenon exhibited by these materials. Numerical simulations of Newtonian breakup are compared with experimental results, and show that previous ground-based attempts at measuring the extensional viscosity of Newtonian fluids are of limited accuracy.
Multiphase hydrodynamic modeling and analysis of non-Newtonian coal/water slurry rheology
Wang, C.S.; Lyczkowski, R.W.; Berry, G.F.
1988-03-01
A multiphase non-Newtonian hydrodynamic model has been developed to predict the spatial and temporal distributions of pressure, relative motion between solids and liquid, solids concentration, and slurry shear rate and viscosity. This model includes separate continuity and momentum equations for each phase and extends the well accepted power-law, non-Newtonian constitutive relationship for shear stress calculations. The model has been partially validated by comparison with single-phase power-law non-Newtonian flow theory and the literature data. The present model has also been used to analyze the pure water, No. 2 diesel fuel and coal/water slurry data measured by using high pressure and high shear rate capillary tube systems. Excellent agreement has been obtained between the calculated and measured values on mixture shear rates and viscosity, mass flow rates, and pressure. 19 refs., 5 figs., 4 tabs.
The Rayleigh-Taylor instability of Newtonian and non-Newtonian fluids
NASA Astrophysics Data System (ADS)
Doludenko, A. N.; Fortova, S. V.; Son, E. E.
2016-10-01
Along with Newtonian fluids (for example, water), fluids with non-Newtonian rheology are widespread in nature and industry. The characteristic feature of a non-Newtonian fluid is the non-linear dependence between the shear stress and shear rate tensors. The form of this relation defines the types of non-Newtonian behavior: viscoplastic, pseudoplastic, dilatant and viscoelastic. The present work is devoted to the study of the Rayleigh-Taylor instability in pseudoplastic fluids. The main aim of the work is to undertake a direct three-dimensional numerical simulation of the mixing of two media with various rheologies and obtain the width of the mixing layer and the kinetic energy spectra, depending on the basic properties of the shear thinning liquids and the Atwood number. A theoretical study is carried out on the basis of the Navier-Stokes equation system for weakly compressible media.
Numerical modeling of gravity-driven bubble flows with account of polydispersion
NASA Astrophysics Data System (ADS)
Chernyshev, A. S.; Schmidt, A. A.
2016-10-01
The present study is focused on the investigation of motion of bubble-liquid medium inside the bubble columns or vertical pipes with account of polydisperse phenomena by the means of numerical simulation. The underlying mathematical model is based on the Euler- Euler approach with interphase interaction described by the momentum and mass transfer between phases, along with the k-w-SST turbulence model which includes turbulence generation by the bubble motion and bubble path dispersion. Polydispersion is taken into account by the multi-class model with piecewise-constant distribution of bubble sizes per cell. Simulation of downward flow inside the straight vertical pipe resulted in maximum of the bubble void fraction close to the pipe center which is in good correlation with the experimental data. Simulation of multiphase flow inside rectangular bubble column with off-center sparger resulted in vertical bubble-liquid jet which is biased towards nearby wall with the correct prediction of attachment point location.
NASA Astrophysics Data System (ADS)
Tian, Ruijun
Two typical unsteady fluid-structure interaction problems have been investigated in the present study. One of them was about actively plunged flexible hydrofoil; the other was about gravity-driven falling plates in water. Real-time velocity field and dynamic response on the moving objects were measured to study these unsteady and highly nonlinear problems. For a long time, scientists have believed that bird and insect flight benefits greatly from the flexibility and morphing facility of their wings via flapping motion. A significant advantage flexible wing models have over quasi-steady rigid wing models is a much higher lift generation capability. Both experimental and computational studies have shown that the leading and trailing edge vortexes (LEV and TEV) play a major role in the efficient generation of such unconventionally high lift force. In this study, two NACA0012 miniature hydrofoils, one flexible and the other rigid, were actively plunged at various frequencies in a viscous glycerol-water solution to study the influence of flexibility. Two-dimensional, phase-locked particle image velocimetry (PIV) measurements were conducted to investigate the temporal and spacial development of LEVs and TEVs. Simultaneous measurements of lift and thrust forces were recorded to reveal the relationship between hydrodynamic force and the evolution of the surrounding flow field. Results from the flexible hydrofoil were compared to those from the rigid one in order to quantitatively analyze the effects of flexibility. The second problem focused on fluid-structure interaction of gravity driven falling plates. Falling leaves and paper cards in air has drawn plenty of research interest in the past decades to investigate the interaction between the fluid flow and the falling object. In this research, time-resolved PIV were employed to experimentally visualize the flow field evolution around the gravity-driven falling plates. The plates were made of different materials with
NASA Astrophysics Data System (ADS)
Kravitz, Katherine; Mueller, Karl; Upton, Phaedra
2017-04-01
The Grabens of Canyonlands National Park is a well-exposed gravity driven system of salt structures driven by the incision of the Colorado River canyon toward a 300 m thick evaporite layer. The region contains an array of normal faults with displacement accommodated by a combination of salt flow and overburden gliding toward the canyon and provides the opportunity to explore salt deformation mechanics in three dimensions. Maybe describe other structures besides faults? Meander anticline, diapirs. Using a combination of interferometric synthetic aperture radar (InSAR) and three-dimensional numerical modeling, we: 1) quantify displacement rates and kinematics of the region, 2) explore how various parameters driving deformation interact and control deformation, and 3) use these results to understand the mechanics of a gravity driven salt system. Initial InSAR results show average line-of-sight (LOS) displacement of 1-3 mm/yr throughout the deforming region. The data set can additionally provide a time series from 1992-2011 and multiple components of deformation using both ascending and descending scenes. Three-dimensional numerical models were created to explore the roles of overburden rheology, salt geometry, and topography on salt deformation. We converted the model displacement into LOS displacement rates for direct comparison to InSAR rates. Within the Grabens, overburden rheology plays an important role on deformation patterns. Not only do preexisting weaknesses allow propagation of deformation away from the river canyon and an increase in overburden displacement rates, the mechanics in the region are spatially complex. The models indicate a transition from gravity spreading to gliding dependent on topography, where spreading is dominant below horsts and transitions to gliding toward the grabens. Additionally, salt flow is more sensitive to smaller scale topographic features and is diverted toward individual side tributaries and grabens on spatial scales of
Yoon, Hyun; Na, Seung-Heon; Choi, Jae-Young; Latthe, Sanjay S; Swihart, Mark T; Al-Deyab, Salem S; Yoon, Sam S
2014-10-07
We prepared a simple, low-cost membrane suitable for gravity-driven oil-water separation and water purification. Composite membranes with selective wettability were fabricated from a mixture of aqueous poly(diallyldimethylammonium chloride) solution, sodium perfluorooctanoate, and silica nanoparticles. Simply dip-coating a stainless steel mesh using this mixture produced the oil-water separator. The contact angles (CAs) of hexadecane and water on the prepared composite membranes were 95 ± 2° and 0°, respectively, showing the oleophobicity and superhydrophilicity of the membrane. In addition, a graphene plug was stacked below the membrane to remove water-soluble organics by adsorption. As a result, this multifunctional device not only separates hexadecane from water, but also purifies water by the permeation of the separated water through the graphene plug. Here, methylene blue (MB) was removed as a demonstration. Membranes were characterized by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy to elucidate the origin of their selective wettability.
Tang, Xiaobin; Ding, An; Qu, Fangshu; Jia, Ruibao; Chang, Haiqing; Cheng, Xiaoxiang; Liu, Bin; Li, Guibai; Liang, Heng
2016-08-01
A pilot-scale gravity-driven membrane (GDM) filtration system under low gravitational pressure without any pre-treatment, backwash, flushing, or chemical cleaning was carried out to investigate the effect of operation parameters (including operation pressure, aeration mode, and intermittent filtration) on the effluent quality and permeability development. The results revealed that GDM system exhibited an efficient performance for the removal of suspended substances and organic compounds. The stabilization of flux occurred and the average values of stable flux were 6.6, 8.1, and 8.6 Lm(-2) h(-1) for pressures of 65, 120, and 200 mbar, respectively. In contrast, flux stabilization was not observed under continuous and intermittent aeration conditions. However, aeration (especially continuous aeration) was effective to improve flux and alleviate membrane fouling during 1-month operation. Moreover, intermittent filtration would influence the stabilization of permeate flux, resulting in a higher stable flux (ranging from 6 to 13 Lm(-2) h(-1)). The stable flux significantly improved with the increase of intermittent period. Additionally, GDM systems exhibited an efficient recovery of flux after simple physical cleaning and the analyses of resistance reversibility demonstrated that most of the total resistance was hydraulic reversible resistance (50-75 %). Therefore, it is expected that the results of this study can develop strategies to increase membrane permeability and reduce energy consumption in GDM systems for decentralized water supply.
Zhang, Yandong; Li, Haifang; Ma, Yuan; Lin, Jin-Ming
2014-03-07
This work presents a paper spray mass spectrometry-based method, to analyze microdroplets produced in a gravity-driven microchip. Droplets at ambient pressure were passively transferred from the chip to a paper substrate by the capillary wicking effect. Paper spray ionization was then performed for mass spectrometry (MS) analysis of droplet contents. The qualitative and quantitative analytical performances of this technique for single droplets were demonstrated. This manually controlled interface is straightforward, low-cost and simple to implement. Moreover, paper spray ionization MS holds promise in the direct analysis of real biological/chemical microreaction samples because of its tolerance with complex matrices. As a proof-of-concept example, the droplet-based acetylcholine hydrolysis was carried out to demonstrate the validation of our method for the direct analysis of micro-chemical/biological reactions. We also introduced a flow injection analysis (FIA) system combined with our droplet system to generate a concentration gradient. As a result, the microreaction can be performed at different concentrations and kinetic information can be obtained in one sample injection. In conclusion, the combination of a microdroplet chip with paper spray ionization and the introduction of the FIA system and make our droplet-MS scheme a useful platform for monitoring and analyzing organic-phase chemical/biological reactions.
Laschi, Serena; Miranda-Castro, Rebeca; González-Fernández, Eva; Palchetti, Ilaria; Reymond, Frédéric; Rossier, Joël S; Marrazza, Giovanna
2010-11-01
In this work, the characterisation and the optimisation of hybridisation assays based on a novel, rapid and sensitive micro-analytical, gravity-driven, flow device is reported. This device combines a special chip containing eight polymer microchannels, with a portable, computer-controlled instrument. The device is used as a platform for affinity experiments using oligonucleotide-modified paramagnetic particles. In our approach, both hybridisation and labelling events are performed on streptavidin-coated paramagnetic microparticles functionalized with a biotinylated capture probe. Modified particles, introduced in the microchannel inlet of the chip, accumulate near the electrode surface by virtue of a magnetic holder. After hybridisation with the complementary sequence, the hybrid is labelled with an alkaline phosphatase conjugate. The electrochemical substrate for alkaline phosphatase revelation is p-aminophenyl phosphate. Solutions and reagents are sequentially passed through the microchannels, until enzyme substrate is added for in situ signal detection. Upon readout, the magnet array is flipped away, beads are removed by addition of regeneration buffer, and the so-regenerated chip is ready for further analysis. This protocol has been applied to the analytical detection of specific DNA sequences of Legionella pneumophila, with an RSD=8.5% and a detection limit of 0.33 nM.
Kinetics of gravity-driven slug flow in partially wettable capillaries of varying cross section
NASA Astrophysics Data System (ADS)
Nissan, Alon; Wang, Qiuling; Wallach, Rony
2016-11-01
A mathematical model for slug (finite liquid volume) motion in not-fully-wettable capillary tubes with sinusoidally varying cross-sectional areas was developed. The model, based on the Navier-Stokes equation, accounts for the full viscous terms due to nonuniform geometry, the inertial term, the slug's front and rear meniscus hysteresis effect, and dependence of contact angle on flow velocity (dynamic contact angle). The model includes a velocity-dependent film that is left behind the advancing slug, reducing its mass. The model was successfully verified experimentally by recording slug movement in uniform and sinusoidal capillary tubes with a gray-scale high-speed camera. Simulation showed that tube nonuniformity has a substantial effect on slug flow pattern: in a uniform tube it is monotonic and depends mainly on the slug's momentary mass/length; an undulating tube radius results in nonmonotonic flow characteristics. The static nonzero contact angle varies locally in nonuniform tubes owing to the additional effect of wall slope. Moreover, the nonuniform cross-sectional area induces slug acceleration, deceleration, blockage, and metastable-equilibrium locations. Increasing contact angle further amplifies the geometry effect on slug propagation. The developed model provides a modified means of emulating slug flow in differently wettable porous media for intermittent inlet water supply (e.g., raindrops on the soil surface).
Low-Reynolds-number gravity-driven migration and deformation of bubbles near a free surface
NASA Astrophysics Data System (ADS)
Pigeonneau, Franck; Sellier, Antoine
2011-09-01
We investigate numerically the axisymmetric migration of bubbles toward a free surface, using a boundary-integral technique. Our careful numerical implementation allows to study the bubble(s) deformation and film drainage; it is benchmarked against several tests. The rise of one bubble toward a free surface is studied and the computed bubble shape compared with the results of Princen [J. Colloid Interface Sci. 18, 178 (1963)]. The liquid film between the bubble and the free surface is found to drain exponentially in time in full agreement with the experimental work of Debrégeas et al. [Science 279, 1704 (1998)]. Our numerical results also cast some light on the role played by the deformation of the fluid interfaces and it turns out that for weakly deformed interfaces (high surface tension or a tiny bubble) the film drainage is faster than for a large fluid deformation. By introducing one or two additional bubble(s) below the first one, we examine to which extent the previous trends are affected by bubble-bubble interactions. For instance, for a 2-bubble chain, decreasing the bubble-bubble separation increases the deformation of the last bubble in the chain. Finally, the exponential drainage of the film between the free surface and the closest bubble is preserved, yet the drainage is enhanced.
Gravity-driven microfluidic particle sorting device with hydrodynamic separation amplification.
Huh, Dongeun; Bahng, Joong Hwan; Ling, Yibo; Wei, Hsien-Hung; Kripfgans, Oliver D; Fowlkes, J Brian; Grotberg, James B; Takayama, Shuichi
2007-02-15
This paper describes a simple microfluidic sorting system that can perform size profiling and continuous mass-dependent separation of particles through combined use of gravity (1 g) and hydrodynamic flows capable of rapidly amplifying sedimentation-based separation between particles. Operation of the device relies on two microfluidic transport processes: (i) initial hydrodynamic focusing of particles in a microchannel oriented parallel to gravity and (ii) subsequent sample separation where positional difference between particles with different mass generated by sedimentation is further amplified by hydrodynamic flows whose streamlines gradually widen out due to the geometry of a widening microchannel oriented perpendicular to gravity. The microfluidic sorting device was fabricated in poly(dimethylsiloxane), and hydrodynamic flows in microchannels were driven by gravity without using external pumps. We conducted theoretical and experimental studies on fluid dynamic characteristics of laminar flows in widening microchannels and hydrodynamic amplification of particle separation. Direct trajectory monitoring, collection, and post-analysis of separated particles were performed using polystyrene microbeads with different sizes to demonstrate rapid (<1 min) and high-purity (>99.9%) separation. Finally, we demonstrated biomedical applications of our system by isolating small-sized (diameter <6 microm) perfluorocarbon liquid droplets from polydisperse droplet emulsions, which is crucial in preparing contrast agents for safe, reliable ultrasound medical imaging, tracers for magnetic resonance imaging, or transpulmonary droplets used in ultrasound-based occlusion therapy for cancer treatment. Our method enables straightforward, rapid, real-time size monitoring and continuous separation of particles in simple stand-alone microfabricated devices without the need for bulky and complex external power sources. We believe that this system will provide a useful tool to separate
Electrophoresis in a non-Newtonian fluid: sphere in a spherical cavity.
Lee, Eric; Huang, Yu Fen; Hsu, Jyh Ping
2003-02-15
The electrophoretic behavior of a sphere in a non-Newtonian fluid is investigated theoretically by analyzing the phenomenon that occurs in a spherical cavity under the condition of a weak applied electrical field. Non-Newtonian behavior in the liquid phase may be due to, for example, the addition of polymer to a colloidal dispersion to improve its stability. It may also arise from the increase in the volume fraction of the dispersed phase such as the slurry used in chemical mechanical polishing. A Carreau model is adopted to characterize the shear-thinning behavior of the liquid phase. We show that the difference between the mobility of the particle based on the present model and that based on the corresponding Newtonian fluid increases with the decrease in the thickness of a double layer. The shear-thinning nature of the liquid phase has the effect of increasing the mobility.
Non-Newtonian gravity or gravity anomalies?
NASA Technical Reports Server (NTRS)
Rubincam, David P.; Chao, B. Fong; Schatten, Kenneth H.; Sager, William W.
1988-01-01
Geophysical measurements of G differ from laboratory values, indicating that gravity may be non-Newtonian. A spherical harmonic formulation is presented for the variation of (Newtonian) gravity inside the Earth. Using the GEM-10B Earth Gravitational Field Model, it is shown that long-wavelength gravity anomalies, if not corrected, may masquerade as non-Newtonian gravity by providing significant influences on experimental observation of delta g/delta r and G. An apparent contradiction in other studies is also resolved: i.e., local densities appear in equations when average densities of layers seem to be called for.
NASA Astrophysics Data System (ADS)
Robson, A. G.; King, R. C.; Holford, S. P.
2016-08-01
We use three-dimensional (3D) seismic reflection data to analyse the structural style and growth of a normal fault array located at the present-day shelf-edge break and into the deepwater province of the Otway Basin, southern Australia. The Otway Basin is a Late Jurassic to Cenozoic, rift-to-passive margin basin. The seismic reflection data images a NW-SE (128-308) striking, normal fault array, located within Upper Cretaceous clastic sediments and which consists of ten fault segments. The fault array contains two hard-linked fault assemblages, separated by only 2 km in the dip direction. The gravity-driven, down-dip fault assemblage is entirely contained within the 3D seismic survey, is located over a basement plateau and displays growth commencing and terminating during the Campanian-Maastrichtian, with up to 1.45 km of accumulated throw (vertical displacement). The up-dip normal fault assemblage penetrates deeper than the base of the seismic survey, but is interpreted to be partially linked along strike at depth to major basement-involved normal faults that can be observed on regional 2D seismic lines. This fault assemblage displays growth initiating in the Turonian-Santonian and has accumulated up to 1.74 km of throw. Our detailed analysis of the 3D seismic data constraints post-Cenomanian fault growth of both fault assemblages into four evolutionary stages: [1] Turonian-Santonian basement reactivation during crustal extension between Australia and Antarctica. This either caused the upward propagation of basement-involved normal faults or the nucleation of a vertically isolated normal fault array in shallow cover sediments directly above the reactivated basement-involved faults; [2] continued Campanian-Maastrichtian crustal extension and sediment loading eventually created gravitational instability on the basement plateau, nucleating a second, vertically isolated normal fault array in the cover sediments; [3] eventual hard-linkage of fault segments in both fault
Shao, Senlin; Feng, Yijing; Yu, Huarong; Li, Jiangyun; Li, Guibai; Liang, Heng
2017-01-01
Gravity-driven membrane (GDM) filtration is a promising decentralized drinking water treatment process. To improve the performance of GDM system, a thin layer of adsorbent was pre-deposited on the membrane surface prior to filtration (adsorbent-laden GDM system). The tested adsorbents include powdered activated carbon (PAC) and anion exchange resin (AER), and an unmodified GDM system and a SiO2-laden GDM system were used as controls. In the adsorbent-laden GDM systems, the adsorption of the PAC and AER increased the removal efficiency of natural organic matter by 7.2-43.5% and microcystin-LR, atrazine, and bisphenol A by 7.9-81.2%. The presence of adsorbent particles increased the amount of microorganisms in the cake layer and therefore increased the removal efficiency of assimilable organic matter (AOC) by 20.1-34.4%. In the adsorbent-laden GDM systems, the physically irrecoverable fouling decreased because of the reduction in membrane foulants by the adsorbent layer. However, the presence of adsorbent particles in the cake layer counteracted this effect and increased the physically recoverable fouling. Consequently, the pre-deposited adsorbent layers had only a limited effect on the stabilized flux (2.26-2.65 L/m(2) h). A bilayer structure was found in the cake layer of the adsorbent-laden GDM systems via scanning electron microscopy (SEM), and the cake layer was looser in the presence of adsorbent particles. These results demonstrate that pre-depositing a thin layer of adsorbents on the membrane surface of the GDM system can significantly improve the quality of the permeate without decreasing the stabilized flux. Copyright Â© 2016 Elsevier Ltd. All rights reserved.
Derlon, Nicolas; Koch, Nicolas; Eugster, Bettina; Posch, Thomas; Pernthaler, Jakob; Pronk, Wouter; Morgenroth, Eberhard
2013-04-15
The impact of different feed waters in terms of eukaryotic populations and organic carbon content on the biofilm structure formation and permeate flux during Gravity-Driven Membrane (GDM) filtration was investigated in this study. GDM filtration was performed at ultra-low pressure (65 mbar) in dead-end mode without control of the biofilm formation. Different feed waters were tested (River water, pre-treated river water, lake water, and tap water) and varied with regard to their organic substrate content and their predator community. River water was manipulated either by chemically inhibiting all eukaryotes or by filtering out macrozoobenthos (metazoan organisms). The structure of the biofilm was characterized at the meso- and micro-scale using Optical Coherence Tomography (OCT) and Confocal Laser Scanning Microscopy (CLSM), respectively. Based on Total Organic Carbon (TOC) measurements, the river waters provided the highest potential for bacterial growth whereas tap water had the lowest. An increasing content in soluble and particulate organic substrate resulted in increasing biofilm accumulation on membrane surface. However, enhanced biofilm accumulation did not result in lower flux values and permeate flux was mainly influenced by the structure of the biofilm. Metazoan organisms (in particular nematodes and oligochaetes) built-up protective habitats, which resulted in the formation of open and spatially heterogeneous biofilms composed of biomass patches. In the absence of predation by metazoan organisms, a flat and compact biofilm developed. It is concluded that the activity of metazoan organisms in natural river water and its impact on biofilm structure balances the detrimental effect of a high biofilm accumulation, thus allowing for a broader application of GDM filtration. Finally, our results suggest that for surface waters with high particulate organic carbon (POC) content, the use of worms is suitable to enhance POC removal before ultrafiltration units
NASA Astrophysics Data System (ADS)
Masters, Roy
2010-03-01
Flowing global gravitation initially produced space without time or mass. Space-time and mass are properties of flowing global gravitation. From its fabric, primal mass spins spontaneously giving rise to local gravitational space-time curvatures. Global gravity is the unifying background field. Gravity began flowing from its singularity with a big whoosh. It curves with angular rotational precession, creating a spatial geometry similar to the windings of a ball of string. Three-dimensional global gravity swirls locally into massive densities. Concurrently with these densities, local gravity curvatures of space-time arise. The expanse between celestial objects is not completely empty, void space as generally believed; it is antecedent gravity, a prerequisite associated field necessary for originating the first quantum particles. Gravity is dark energy; gravity's spin, as the second fundamental force, is electromagnetic dark matter. Electromagnetic masses attract then gravity compresses hot, dense and small---then bang, the first hydrogen star of which there are many. There may have been many big bangs, but no Big Bang that ultimately created the universe.
Gupta, Renu; Bansal, Ajay
2013-08-01
Axial dispersion is an important parameter in the performance of packed bed reactors. A lot of fluids exhibit non-Newtonian behaviour but the effect of rheological parameters on axial dispersion is not available in literature. The effect of rheology on axial dispersion has been analysed for viscoinelastic and viscoelastic non-Newtonian fluids. Aqueous solutions of carboxymethyl cellulose and polyacrylamide have been chosen to represent viscoinelastic and viscoelastic liquid-phases. Axial dispersion has been measured in terms of BoL number. The single parameter axial dispersion model has been applied to analyse RTD response curve. The BoL numbers were observed to increase with increase in liquid flow rate and consistency index 'K' for viscoinelastic as well as viscoelastic fluids. Bodenstein correlation for Newtonian fluids proposed has been modified to account for the effect of fluid rheology. Further, Weissenberg number is introduced to quantify the effect of viscoelasticity.
Nonlinear drainage of some non-Newtonian free films
NASA Astrophysics Data System (ADS)
Tabakova, S.
2015-10-01
In the present work we apply the generalized lubrication approach (including inertial, viscous, capillary and van-der-Waals forces) to study the dynamics of a free thin film of a non-Newtonian fluid, whose viscosity is described by the Power law and Carreau models. For planar films with fully mobile surfaces, this approach leads to a system of two nonlinear PDE for the film thickness and lateral velocity. This system is solved numerically in the case of laterally bounded free films. The calculations of the film shape and velocity are presented using data of some real liquids: blood and aqueous solution of 0.5% hydroxyethylcellulose. It is shown that the Power law model predicts a very different viscosity to the Carreau model viscosity, although that the film profiles are not very different for all film wetting angles.
NASA Astrophysics Data System (ADS)
Iverson, R. M.; Schaeffer, D. G.
2009-12-01
Landslides provide accessible sites for studying diverse styles of displacement that may serve as analogs for fault slip in Earth's crust. Field observations and large-scale experiments demonstrate that landslides can exhibit slow, stable creep, episodic stick-slip, or runaway acceleration - similar to the diverse styles of motion inferred for faults and subduction zones. A mechanical model that explains all of these styles of landsliding considers gravity-driven motion of a water-saturated, poroelastic slide block regulated by pore-pressure change in a dilating or contracting basal shear zone that exchanges water with the block. If the shear zone exhibits rate-independent Coulomb friction, the stability of slide-block motion depends only on the sign of the Coulomb dilatancy angle, ψ (ψ > 0 implies dilation and stable creep; ψ < 0 implies contraction and runaway acceleration) and on evolution of ψ with displacement. If the shear zone exhibits nonlinearly rate-weakening friction together with ψ > 0, however, the model predicts that a transition (i.e., a Hopf bifurcation) occurs from stable, creeping motion to periodic stick-slip. The bifurcation is sharply demarcated by a line that transects a parameter space defined by the logarithms of two dimensionless parameters, one proportional to the ratio of the intrinsic timescales for downslope motion and pore-pressure diffusion in the slide block, and one proportional to the ratio of the intrinsic velocity scales for pore-fluid flow and rate-weakening of friction in the basal shear zone. In the unstable (upper) part of this parameter space, the amplitude and period of stick-slip oscillations increase with distance from the bifurcation line. Significantly, stick-slip behavior predicted by the model occurs in the absence of an elastic driving force; the elastic spring in classic spring-slider earthquake models is effectively replaced by pore-pressure diffusion, and the energy necessary to drive this dissipative but
Akhondi, Ebrahim; Wu, Bing; Sun, Shuyang; Marxer, Brigit; Lim, Weikang; Gu, Jun; Liu, Linbo; Burkhardt, Michael; McDougald, Diane; Pronk, Wouter; Fane, Anthony G
2015-03-01
In this study gravity-driven membrane (GDM) ultrafiltration is investigated for the pretreatment of seawater before reverse osmosis (RO). The impacts of temperature (21 ± 1 and 29 ± 1 °C) and hydrostatic pressure (40 and 100 mbar) on dynamic flux development and biofouling layer structure were studied. The data suggested pore constriction fouling was predominant at the early stage of filtration, during which the hydrostatic pressure and temperature had negligible effects on permeate flux. With extended filtration time, cake layer fouling played a major role, during which higher hydrostatic pressure and temperature improved permeate flux. The permeate flux stabilized in a range of 3.6 L/m(2) h (21 ± 1 °C, 40 mbar) to 7.3 L/m(2) h (29 ± 1 °C, 100 mbar) after slight fluctuations and remained constant for the duration of the experiments (almost 3 months). An increase in biofouling layer thickness and a variable biofouling layer structure were observed over time by optical coherence tomography and confocal laser scanning microscopy. The presence of eukaryotic organisms in the biofouling layer was observed by light microscopy and the microbial community structure of the biofouling layer was analyzed by sequences of 16S rRNA genes. The magnitude of permeate flux was associated with the combined effect of the biofouling layer thickness and structure. Changes in the biofouling layer structure were attributed to (1) the movement and predation behaviour of the eukaryotic organisms which increased the heterogeneous nature of the biofouling layer; (2) the bacterial debris generated by eukaryotic predation activity which reduced porosity; (3) significant shifts of the dominant bacterial species over time that may have influenced the biofouling layer structure. As expected, most of the particles and colloids in the feed seawater were removed by the GDM process, which led to a lower RO fouling potential. However, the dissolved organic carbon in the
NASA Astrophysics Data System (ADS)
Favelukis, Moshe; Lavrenteva, Olga M.; Nir, Avinoam
2006-09-01
We consider the deformation and breakup of a non-Newtonian slender drop in a Newtonian liquid, subject to an axisymmetric extensional flow, and the influence of inertia in the continuous phase. The non-Newtonian fluid inside the drop is described by the simple power-law model and the unsteady deformation of the drop is represented by a single partial differential equation. The steady-state problem is governed by four parameters: the capillary number; the viscosity ratio; the external Reynolds number; and the exponent characterizing the power-law model for the non-Newtonian drop. For Newtonian drops, as inertia increases, drop breakup is facilitated. However, for shear thinning drops, the influence of increasing inertia results first in preventing and then in facilitating drop breakup. Multiple stationary solutions were also found and a stability analysis has been performed in order to distinguish between stable and unstable stationary states.
NASA Astrophysics Data System (ADS)
Cruciani, F.; Barchi, M. R.; Koyi, H. A.; Porreca, M.
2017-08-01
The deepwater fold-and-thrust belts (DWFTBs) are geological structures recently explored thanks to advances in offshore seismic imaging by oil industry. In this study we present a kinematic analysis based on three balanced cross-sections of depth-converted, 2-D seismic profiles along the offshore Lamu Basin (East African passive margin). This margin is characterized by a regional-scale DWFTB (> 450 km long), which is the product of gravity-driven contraction on the shelf that exhibits complex structural styles and differing amount of shortening along strike. Net shortening is up to 48 km in the northern wider part of the fold-and-thrust belt (≈ 180 km), diminishing to < 15 km toward the south, where the belt is markedly narrower (≈ 50 km). The three balanced profiles show a shortening percentage around 20% (comparable with the maximum values documented in other gravity-driven DWFTBs), with a significant variability along dip: higher values are achieved in the outer (i.e. down-dip) portion of the system, dominated by basinward-verging, imbricate thrust sheets. Fold wavelength increases landward, where doubly-verging structures and symmetric detachment folds accommodate a lower amount of shortening. Similar to other cases, a linear and systematic relationship between sedimentary thickness and fold wavelength is observed. Reconstruction of the rate of shortening through time within a fold-and-thrust belt shows that after an early phase of slow activation (Late Cretaceous), > 95% of net shortening was produced in < 10 Myr (during Paleocene). During this acme phase, which followed a period of high sedimentation rate, thrusts were largely synchronous and the shortening rate reached a maximum value of 5 mm/yr. The kinematic evolution reconstructed in this study suggests that the structural evolution of gravity-driven fold-and-thrust belts differs from the accretionary wedges and the collisional fold-and-thrust belts, where thrusts propagate in-sequence and shortening
Non-Newtonian fluid flow over a heterogeneously slippery surface
NASA Astrophysics Data System (ADS)
Haase, A. Sander; Wood, Jeffery A.; Sprakel, Lisette M. J.; Lammertink, Rob G. H.
2015-11-01
The no-slip boundary condition does not always hold. In the past, we have investigated the influence of effective wall slip on interfacial transport for a bubble mattress - a superhydrophobic surface consisting of an array of transverse gas-filled grooves. We proved experimentally that the amount of effective wall slip depends on the bubble protrusion angle and the surface porosity (Karatay et al., PNAS 110, 2013), and predicted that mass transport can be enhanced significantly (Haase et al., Soft Matter 9, 2013). Both studies involve the flow of water. In practise, however, many liquids encountered are non-Newtonian, like blood and polymer solutions. This raises some interesting questions. How does interfacial transport depend on the rheological properties of the liquid? Does the time-scale of the experiment matter? A bubble mattress is a suitable platform to investigate this, due to local variations in shear rate. We predict that for shear-thinning liquids, compared to water, the amount of wall slip can be enhanced considerably, although this depends on the applied flow rate. Experiments are performed to proof this behaviour. Simulations are used to assess what will happen when the characteristic time-scale of the system matches the relaxation time of the visco-elastic liquid. R.G.H.L. acknowledges the European Research Council for the ERC starting grant 307342-TRAM.
NASA Astrophysics Data System (ADS)
Düll, Wolf-Patrick; Schneider, Guido; Wayne, C. Eugene
2016-05-01
In 1968 V.E. Zakharov derived the Nonlinear Schrödinger equation for the two-dimensional water wave problem in the absence of surface tension, that is, for the evolution of gravity driven surface water waves, in order to describe slow temporal and spatial modulations of a spatially and temporarily oscillating wave packet. In this paper we give a rigorous proof that the wave packets in the two-dimensional water wave problem in a canal of finite depth can be approximated over a physically relevant timespan by solutions of the Nonlinear Schrödinger equation.
NASA Astrophysics Data System (ADS)
Robin, Cécile; Guillocheau, François; Rouby, Delphine; Nalpas, Thierry; Jermannaud, Paul; Raillard, Stéphane
2013-04-01
We studied the evolution of the gravity flow sedimentary within a large shelf-edge delta (Eastern Niger delta) over the last 2,5Myr taking into account the influence of the contemporaneous gravity driven deformation and sedimentary supply. To do this, we mapped (i) the shoreline geometry and (ii) the associated turbiditic systems for 9 intervals using a classification based on three morphological end-members: erosive, constructive and depositional modes. We characterized the depositional profile of the passive margin delta from the littoral domain to the abyssal plain and its spatial and temporal variability. We showed that, at the scale of the delta, the depositional profile varied from (i) a shelf edge delta profile with a slope break at the location of the shoreline during progradation to (ii) a ramp profile characteristic of a mid-shelf delta during retrogradation. Thus, during a stratigraphic cycle, the delta front evolved from a prograding slope break during the development of the HST, to steepening clinoforms during the development of the LST that progressively flattened out during the TST to reach a ramp profile at the MFS. The turbiditic systems (including MTC) initiate near the shoreline, at the toe of the delta front. Also, they form preferentially down slope synthetic faults or within antithetic fault relays. They are initially erosive, becoming constructive further down slope and eventually depositional. They may become erosive again as they cut through the compressional structures. We showed that the stratigraphic state (progradation/retrogradation) controls the amount of sediment reaching the platform and strongly impacts the density of gravity flow sedimentary systems (low density during progradation and high density during progradation). On the other hand, the gravity driven deformation controls the slope of the sea-floor and, in doing so, their morphology (erosive/constructive/depositional). Within this framework, lateral migrations of the delta
NASA Astrophysics Data System (ADS)
Khojasteh, Danial; Mousavi, Seyed Mahmood; Kamali, Reza
2017-05-01
In the present study, the behaviors of Newtonian and shear-thinning non-Newtonian droplets impinging on heated hydrophilic and hydrophobic surfaces have been investigated numerically using Ansys-Fluent. In this context, the volume-of-fluid technique is applied to track the free-surface of the liquid, and variable time-step is also utilized to control the Courant number. Furthermore, we have considered the dependence of viscosity, density and surface tension on temperature during the simulation. The results are compared to available experimental data at the same conditions, such as boundary conditions. The results demonstrate that there is a good agreement between the obtained results and the experimental trends, concerning normalized diameter profiles at various Weber numbers. Therefore, the focus of the present study is an assessment of the effects of variations in Weber number, contact angle and surface temperature for Newtonian and non-Newtonian liquids on dynamics behavior of droplet in collision with hydrophobic and hydrophilic surfaces. The results represent that the behaviors of Newtonian and non-Newtonian droplets are totally different, indicating the droplet sensitivity to the working parameters.
NASA Astrophysics Data System (ADS)
Khojasteh, Danial; Mousavi, Seyed Mahmood; Kamali, Reza
2016-11-01
In the present study, the behaviors of Newtonian and shear-thinning non-Newtonian droplets impinging on heated hydrophilic and hydrophobic surfaces have been investigated numerically using Ansys-Fluent. In this context, the volume-of-fluid technique is applied to track the free-surface of the liquid, and variable time-step is also utilized to control the Courant number. Furthermore, we have considered the dependence of viscosity, density and surface tension on temperature during the simulation. The results are compared to available experimental data at the same conditions, such as boundary conditions. The results demonstrate that there is a good agreement between the obtained results and the experimental trends, concerning normalized diameter profiles at various Weber numbers. Therefore, the focus of the present study is an assessment of the effects of variations in Weber number, contact angle and surface temperature for Newtonian and non-Newtonian liquids on dynamics behavior of droplet in collision with hydrophobic and hydrophilic surfaces. The results represent that the behaviors of Newtonian and non-Newtonian droplets are totally different, indicating the droplet sensitivity to the working parameters.
CFD simulation of non-Newtonian fluid flow in anaerobic digesters.
Wu, Binxin; Chen, Shulin
2008-02-15
A general mathematical model that predicts the flow fields in a mixed-flow anaerobic digester was developed. In this model, the liquid manure was assumed to be a non-Newtonian fluid, and the flow governed by the continuity, momentum, and k-epsilon standard turbulence equations, and non-Newtonian power law model. The commercial computational fluid dynamics (CFD) software, Fluent, was applied to simulate the flow fields of lab-scale, scale-up, and pilot-scale anaerobic digesters. The simulation results were validated against the experimental data from literature. The flow patterns were qualitatively compared for Newtonian and non-Newtonian fluids flow in a lab-scale digester. Numerical simulations were performed to predict the flow fields in scale-up and pilot-scale anaerobic digesters with different water pump power inputs and different total solid concentration (TS) in the liquid manure. The optimal power inputs were determined for the pilot-scale anaerobic digester. Some measures for reducing dead and low velocity zones were proposed based upon the CFD simulation results.
Predicting single-phase and two-phase non-Newtonian flow behavior in pipes
Kaminsky, R.D.
1998-12-31
Improved and novel prediction methods are described for single-phase and two-phase flow of non-Newtonian fluids in pipes. Good predictions are achieved for pressure drop, liquid holdup fraction, and two-phase flow regime. The methods are applicable to any visco-inelastic non-Newtonian fluid and include the effect of surface roughness. The methods utilize a reference fluid for which validated models exist. For single-phase flow the use of Newtonian and power-law reference fluids are illustrated. For two-phase flow a Newtonian reference fluid is used. Focus is given to shear-thinning fluids. The approach is theoretically based and is better suited than correlation methods for two-phase flow in high pressure pipelines, for which no experimental data is available in the literature.
Numerical Modeling of Mixing of Chemically Reacting, Non-Newtonian Slurry for Tank Waste Retrieval
Yuen, David A.; Onishi, Yasuo; Rustad, James R.; Michener, Thomas E.; Felmy, Andrew R.; Ten, Arkady A.; Hier, Catherine A.
2000-06-01
Many highly radioactive wastes will be retrieved by installing mixer pumps that inject high-speed jets to stir up the sludge, saltcake, and supernatant liquid in the tank, blending them into a slurry. This slurry will then be pumped out of the tank into a waste treatment facility. Our objectives are to investigate interactions-chemical reactions, waste rheology, and slurry mixing-occurring during the retrieval operation and to provide a scientific basis for the waste retrieval decision-making process. Specific objectives are to: (1) Evaluate numerical modeling of chemically active, non-Newtonian tank waste mixing, coupled with chemical reactions and realistic rheology; (2) Conduct numerical modeling analysis of local and global mixing of non-Newtonian and Newtonian slurries; and (3) Provide the bases to develop a scientifically justifiable, decision-making support tool for the tank waste retrieval operation.
Wen, Jianping; Jia, Xiaoqiang; Cheng, Xianrui; Yang, Peng
2005-05-01
Hydrodynamic and gas-liquid mass transfer characteristics, such as liquid velocity, gas holdup, solid holdup and gas-liquid volumetric mass transfer coefficient, in the riser and downcomer of the gas-liquid-solid three-phase internal loop airlift bioreactors with complete gas recirculation for non-Newtonian fluids, were investigated. A mathematical model for the description of flow behavior and gas-liquid mass transfer of these bioreactors was developed. The predicted results of this model agreed well with the experimental data.
Non-Newtonian and Viscoelastic Properties of Lava Flows
NASA Astrophysics Data System (ADS)
Bagdassarov, N. S.
2004-12-01
Lava flow models require an in-depth knowledge of the rheological properties of lava. Previous measurements have shown that, at typical eruption temperatures, lavas are non-Newtonian. The reasons for this include the formation and destruction of crystal networks and bubble deformation during shear. The effects of bubbles are investigated experimentally in this contribution using analogue fluids with bubble concentrations <20%. The shear-thinning behaviour of bubbly liquids noted by previous workers is shown to be dependent on the previous shearing history of the fluid. This thixotropic behaviour, which was investigated using a rotational vane viscometer, is caused by delayed bubble deformation and recovery when subjected to changes in shear stress. A rotational vane viscometer and torsional deformation apparatus were used to investigate the rheological properties of bubbly liquids and foams in order to determine a viscoelastic transition. These experiments have shown that the foams tested are viscoelastic power law fluids with a yield strength. Non-Newtonian properties and yield strength of foams are shown to be a probable cause of accelerating flow fragmentation in tube flow experiments on expanding foams. The flow of a bubbly fluid through a narrowing conduit may cause a pulsating regime of a flow due to periodic slip and slip-free boundary conditions near the walls of a conduit. Slip boundary conditions can lead to instability in viscoelastic shear flow causing short wavelength fluctuations at high shear rates. This mechanism may also take place during explosive volcanic eruptions. The frequency and amplitude of oscillation shear affect the structure of lavas which are thixotropic non-Newtonian liquids. The frequency dependent structure of lavas can be identified via frequency hysteresis and time-evolution of internal friction and viscosity. The rheological properties of basaltic lavas from Etna, Hawai'i and Vesuvius have been investigated at temperatures
Experiments on densely-loaded non-Newtonian slurries in laminar and turbulent pipe flows
NASA Astrophysics Data System (ADS)
Park, J. T.; Mannheimer, R. J.; Grimley, T. A.; Morrow, T. B.
1988-02-01
An experimental description of the flow structure of non-Newtonian slurries in the laminar, transitional, and full turbulent pipe flow regimes is the primary objective of this research. Measurements include rheological characterization of the fluid and local fluid velocity measurements with a laser Doppler velocimeter (LDV). Optical access to the flow is gained through a test section and model slurry which are both transparent. The model slurry is formulated from silica gel particles and hydrocarbon liquid mixture whose indices of refraction are matched so that light is not scattered from the particles. Experiments are being conducted in a large-scale pipe slurry flow facility with an inside pipe diameter of 51 mm (2 inches). Detailed flow measurements including turbulence quantities such as Reynolds stress were measured with a two-component two-color LDV. The present research indicates that non-Newtonian slurries are possible with concentrations of a few percent by weight of small particles whose sizes are one micron or less. A non-Newtonian slurry from small particles could maintain large particles (100 micron size) at high concentrations in suspension almost indefinitely. Such a slurry would prevent particle fallout and its associated problems. Velocity profiles were acquired by the LDV in the laminar, transitional, and turbulent flow regimes. The velocity profile for laminar flow was in agreement with theory. The range of the transition region was 21 percent of the transition velocity in comparison to 50 percent for a Newtonian fluid.
Experiments on densely-loaded non-Newtonian slurries in laminar and turbulent pipe flows
NASA Astrophysics Data System (ADS)
Park, J. T.; Mannheimer, R. J.; Grimley, T. A.; Morrow, T. B.
1988-05-01
An experimental description of the flow structure of non-Newtonian slurries in the laminar, transitional, and full turbulent pipe flow regimes is the primary objective of this research. Measurements include rheological characterization of the fluid and local fluid velocity measurements with a Laser Doppler Velocimeter (LDV). Optical access to the flow is gained through a test section and model slurry which are both transparent. The model slurry is formulated from silica gel particles and hydrocarbon liquid mixture whose indices of refraction are matched so that light is not scattered from the particles. Experiments are being conducted in a large-scale pipe slurry. Flow measurements including turbulence quantities such as Reynolds stress were measured with a two-component two-color LDV. The present research indicates that non-Newtonian slurries are possible with concentrations of a few percent by weight of small particles whose sizes are two microns or less. A non-Newtonian slurry from small particles could maintain large particles (one millimeter size) at high concentrations in suspension almost indefinitely. Such a slurry would prevent particle fallout and its associated problems.
Experiments on densely-loaded non-Newtonian slurries in laminar and turbulent pipe flows
NASA Astrophysics Data System (ADS)
Park, J. T.; Mannheimer, R. J.; Grimley, T. A.; Morrow, T. B.
1987-10-01
An experimental description of the flow structure of non-Newtonian slurries in the laminar, transitional, and full turbulent pipe flow regimes is the primary objective of this research. Measurements include rheological characterization of the fluid and local fluid velocity measurements with a laser Doppler velocimeter (LDV). Optical access to the flow is gained through a test section and model slurry which are both transparent. The model slurry is formulated from silica gel particles and hydrocarbon liquid mixture whose indices of refraction are matched so that light is not scattered from the particles. Experiments are being conducted in a large-scale pipe slurry flow facility with an inside pipe diameter of 51 mm (2 inches). Detailed flow measurements including turbulence quantities such as Reynolds stress will be taken with a two-component two-color LDV. The present research indicates that non-Newtonian slurries are possible with concentrations of a few percent by weight of small particles whose sizes are one micron or less. A non-Newtonian slurry from small particles could maintain large particles (100 micron size) at high concentrations in suspension almost indefinitely. Such a slurry would prevent particle fallout and its associated problems.
Wzorek, Alicja; Sato, Azusa; Drabowicz, Józef; Soloshonok, Vadim A
2016-10-07
Herein we report a study of the self-disproportionation of enantiomers (SDE) via gravity-driven achiral column chromatography of a series of amides derived from 1-phenylethylamine. We demonstrated that structural and electronic factors of the substituents play an important role in the observed magnitude of the SDE. For the first time, the SDE phenomenon of amides with that of thioamides was compared. We demonstrate that, in sharp contrast to amides, the substitution of the sulphur atom for the oxygen in the acyl group, strongly reduced the observed magnitude of the SDE. These results clearly indicate the importance of the hydrogen bonding for the formation of homo/hetero-chiral association responsible for manifestation of the SDE phenomenon. Copyright © 2016 Elsevier B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Masrouhi, Amara; Bellier, Olivier; Ben Youssef, Mohamed; Koyi, Hemin
2014-09-01
We used structural, stratigraphic and sedimentologic data, together with a comparison of nearby structures and a Bouguer gravity map, to evaluate the evolution of the Bled Dogra salt structure (northern Tunisia) during the Cretaceous. Triassic salt sheets are recognized in the northwestern region of the Tunisian Atlas. These salt sheets are the result of Cretaceous thick and/or thin-skinned extension along the south Tethyan margin. The Bled Dogra salt structure is one of these submarine allochthonous salt sheets, which was emplaced during the Early Cretaceous. The geologic framework, during this period, produces conditions for a predominantly gravity-driven deformation: extension has produced space for the salt to rise; vigorous differential sedimentation created differential loading that resulted in the emplacement and extrusion of a large volume of Triassic salt and formation of large submarine salt sheets. Geologic field data suggest an interlayered Triassic salt sheet within Albian sequences. Salt was extruded at the sea floor during the Early-Middle Albian and was initially buried by Middle-Late Albian strata. The Coniacian corresponds to a second transgressive cover onto the salt sheet after the gliding of the first salt cover (Late Albian-Turonian). In addition, this northwest Tunisian area exposes evidences for salt flow and abundant slump features at the base of a northward facing submarine slope, which was probably dominant from the Early Cretaceous to Santonian. Two gravity deformation processes are recognized: gravity gliding and gravity spreading. Acting concurrently, these two processes appear indistinguishable in this geologic context. Like the present-day salt-involved passive margins - such as the northern Gulf of Mexico, the Atlantic margin of Morocco, the Brazilian Santos basin, the Angola margin, Cadiz in western Iberia, and the Red Sea - the North African Cretaceous passive margin in Tunisia provides evidences that deformation in a passive
Coupling electrokinetics and rheology: Electrophoresis in non-Newtonian fluids.
Khair, Aditya S; Posluszny, Denise E; Walker, Lynn M
2012-01-01
We present a theoretical scheme to calculate the electrophoretic motion of charged colloidal particles immersed in complex (non-Newtonian) fluids possessing shear-rate-dependent viscosities. We demonstrate that this non-Newtonian rheology leads to an explicit shape and size dependence of the electrophoretic velocity of a uniformly charged particle in the thin-Debye-layer regime, in contrast to electrophoresis in Newtonian fluids. This dependence is caused by non-Newtonian stresses in the bulk (electroneutral) fluid outside the Debye layer, whose magnitude is naturally characterized in an electrophoretic Deborah number.
Process averaging in a granular medium with non-Newtonian interlayers
NASA Astrophysics Data System (ADS)
Karakin, A. V.; Shklover, V. E.
1992-08-01
The paper is concerned with the problem of process averaging in three-component media consisting of solid grains, a non-Newtonian viscously deformable material filling the gaps between the grains, and a nonviscous liquid or a gas within the pores. The basic equations are derived in general form for an arbitrary rheological law and then further specified for a power-law rheological behavior. Macrorelations are obtained analytically and in quadratures for shear and tension/compression. A full solution is obtained for a specific type of microstructure. Some particular cases are examined.
Inelastic non-Newtonian flow over heterogeneously slippery surfaces
NASA Astrophysics Data System (ADS)
Haase, A. Sander; Wood, Jeffery A.; Sprakel, Lisette M. J.; Lammertink, Rob G. H.
2017-02-01
In this study, we investigated inelastic non-Newtonian fluid flow over heterogeneously slippery surfaces. First, we simulated the flow of aqueous xanthan gum solutions over a bubble mattress, which is a superhydrophobic surface consisting of transversely positioned no-slip walls and no-shear gas bubbles. The results reveal that for shear-thinning fluids wall slip can be increased significantly, provided that the system is operated in the shear-thinning regime. For a 0.2 wt% xanthan gum solution with a power-law index of n =0.4 , the numerical results indicate that wall slip can be enhanced 3.2 times when compared to a Newtonian liquid. This enhancement factor was also predicted from a theoretical analysis, which gave an expression for the maximum slip length that can be attained over flat, heterogeneously slippery surfaces. Although this equation was derived for a no-slip/no-shear unit length that is much larger than the typical size of the system, we found that it can also be used to predict the enhancement in the regime where the slip length is proportional to the size of the no-shear region or the bubble width. The results could be coupled to the hydrodynamic development or entrance length of the system, as maximum wall slip is only reached when the fluid flow can fully adapt to the no-slip and no-shear conditions at the wall.
Inelastic non-Newtonian flow over heterogeneously slippery surfaces.
Haase, A Sander; Wood, Jeffery A; Sprakel, Lisette M J; Lammertink, Rob G H
2017-02-01
In this study, we investigated inelastic non-Newtonian fluid flow over heterogeneously slippery surfaces. First, we simulated the flow of aqueous xanthan gum solutions over a bubble mattress, which is a superhydrophobic surface consisting of transversely positioned no-slip walls and no-shear gas bubbles. The results reveal that for shear-thinning fluids wall slip can be increased significantly, provided that the system is operated in the shear-thinning regime. For a 0.2 wt% xanthan gum solution with a power-law index of n=0.4, the numerical results indicate that wall slip can be enhanced 3.2 times when compared to a Newtonian liquid. This enhancement factor was also predicted from a theoretical analysis, which gave an expression for the maximum slip length that can be attained over flat, heterogeneously slippery surfaces. Although this equation was derived for a no-slip/no-shear unit length that is much larger than the typical size of the system, we found that it can also be used to predict the enhancement in the regime where the slip length is proportional to the size of the no-shear region or the bubble width. The results could be coupled to the hydrodynamic development or entrance length of the system, as maximum wall slip is only reached when the fluid flow can fully adapt to the no-slip and no-shear conditions at the wall.
Slow viscous stream over a non-Newtonian fluid sphere in an axisymmetric deformed spherical vessel
NASA Astrophysics Data System (ADS)
Jaiswal, B. R.
2016-08-01
The creeping motion of a non-Newtonian (Reiner-Rivlin) liquid sphere at the instant it passes the center of an approximate spherical container is discussed. The flow in the spheroidal container is governed by the Stokes equation, while for the flow inside the Reiner-Rivlin liquid sphere, the expression for the stream function is obtained by expressing it in the power series of a parameter S , characterizing the cross-viscosity. Both the flow fields are then determined explicitly by matching the boundary conditions at the interface of Newtonian fluid and non-Newtonian fluid, and also the condition of imperviousness and no-slip on the outer surface. As an application, we have considered an oblate spheroidal container. The drag and wall effects on the liquid spherical body are evaluated. Their variations with regard to the separation parameter ℓ , viscosity ratio λ, cross-viscosity S, and deformation parameter ɛ are studied and demonstrated graphically. Several renowned cases are derived from the present analysis. It is observed that the drag not only varies with ɛ, but as ℓ increases, the rate of change in behavior of drag force also increases. The influences of these parameters on the wall effects has also been studied and presented in a table.
Undulatory swimming in non-Newtonian fluids
NASA Astrophysics Data System (ADS)
Ardekani, Arezoo; Li, Gaojin
2015-11-01
Microorganisms often swim in complex fluids exhibiting both elasticity and shear-thinning viscosity. The motion of low Reynolds number swimmers in complex fluids is important for better understanding the migration of sperms and formation of bacterial biofilms. In this work, we numerically investigate the effects of non-Newtonian fluid properties, including shear-thinning and elasticity, on the undulatory locomotion. Our results show that elasticity hinders the swimming speed, but a shear-thinning viscosity in the absence of elasticity enhances the speed. The combination of the two effects hinders the swimming speed. The swimming boost in a shear-thinning fluid occurs even for an infinitely long flagellum. The swimming speed has a maximum, whose value depends on the flagellum oscillation amplitude and fluid rheological properties. The power consumption, on the other hand, follows a universal scaling law. This work is supported by NSF CBET-1445955 and Indiana CTSI TR001108.
Hachmon, Guy; Mamet, Noam; Sasson, Sapir; Barkai, Tal; Hadar, Nomi; Abu-Horowitz, Almogit; Bachelet, Ido
2016-01-01
New types of robots inspired by biological principles of assembly, locomotion, and behavior have been recently described. In this work we explored the concept of robots that are based on more fundamental physical phenomena, such as fluid dynamics, and their potential capabilities. We report a robot made entirely of non-Newtonian fluid, driven by shear strains created by spatial patterns of audio waves. We demonstrate various robotic primitives such as locomotion and transport of metallic loads-up to 6-fold heavier than the robot itself-between points on a surface, splitting and merging, shapeshifting, percolation through gratings, and counting to 3. We also utilized interactions between multiple robots carrying chemical loads to drive a bulk chemical synthesis reaction. Free of constraints such as skin or obligatory structural integrity, fluid robots represent a radically different design that could adapt more easily to unfamiliar, hostile, or chaotic environments and carry out tasks that neither living organisms nor conventional machines are capable of.
Non-Newtonian behavior in simple fluids.
Delhommelle, Jerome; Petravic, J; Evans, Denis J
2004-04-01
Using nonequilibrium molecular dynamics simulations, we study the non-Newtonian rheology of a microscopic sample of simple fluid. The calculations were performed using a configurational thermostat which unlike previous nonequilibrium molecular dynamics or nonequilibrium Brownian dynamics methods does not exert any additional constraint on the flow profile. Our findings are in agreement with experimental results on concentrated "hard sphere"-like colloidal suspensions. We observe: (i) a shear thickening regime under steady shear; (ii) a strain thickening regime under oscillatory shear at low frequencies; and (iii) shear-induced ordering under oscillatory shear at higher frequencies. These results significantly differ from previous simulation results which showed systematically a strong ordering for all frequencies. They also indicate that shear thickening can occur even in the absence of a solvent.
NASA Astrophysics Data System (ADS)
Hu, Bin; Kieweg, Sarah
2011-11-01
Many complex fluids of interest exhibit viscoelastic hehavior. Polymeric drug delivery vehicles, such as anti-HIV topical microbicides, are among these fluids. For the optimal design of microbicides, the combined effect of shear-thinning and elastic behavior on the gravity-driven spreading of viscoelastic fluids is studied. We develop a 2D model to simulate the fluids spreading down an incline using ANSYS POLYFLOW software package. Arbitrary Lagrangian-Eulerian (ALE) method combined with Lagrangian remeshing is applied to track the moving free surface of fluids during spreading. Adaptive meshing method is used to generate high quality mesh for the remeshing process. Based on an elastic viscous split stress (EVSS) approach, several differential viscoelastic constitutive models are studied to investigate the combined effect of shear-thinning and elastic behavior. Mesh convergence test and constant volume check are studied to verify the new model. Moreover, the new model with zero elasticity is compared with previous studies of Newtonian and power-law fluids.
Wang, Jianqiang; Wu, Yichao; Yang, Zhe; Guo, Hao; Cao, Bin; Tang, Chuyang Y
2017-05-24
We report a facile method for preparing silver-loaded membranes for point-of-use disinfection and disaster relief applications. A bio-inspired material, polydopamine, was coated onto a highly porous nanofibrous polyacrylonitrile substrate. We then take advantage of the redox properties of polydopamine to form silver nanoparticles in situ. These nanoparticles were uniformly distributed on the surface of nanofibers with no apparent agglomeration at a silver loading up to 4.36 wt.% (cPAN-Ag1.5). The silver-incorporated membrane cPAN-Ag1.5 achieved a high pure water flux of 130 Lm(-2) h(-1) at 10-cm water head, demonstrating the feasibility of energy-efficient gravity-driven filtration and eliminating the need for electrical power. The strong anti-bacterial activity and high physical rejection of the membrane led to an excellent disinfection power, with no viable bacterial cells detected in its permeate water. The membrane exhibited >7 log reduction for E. coli and >6 log reduction for B. subtilis. The strategy reported here provides an efficient and green route to synthesize point-of-use membranes. Combining their excellent permeability and disinfection effectiveness, these membranes offer an ideal solution to water supply in disaster-affected areas.
Conway, Jon R; Keller, Arturo A
2016-07-01
The gravity-driven transport of TiO2, CeO2, and Cu(OH)2 engineered nanomaterials (ENMs) and their effects on soil pH and nutrient release were measured in three unsaturated soils. ENM transport was found to be highly limited in natural soils collected from farmland and grasslands, with the majority of particles being retained in the upper 0-3 cm of the soil profile, while greater transport depth was seen in a commercial potting soil. Physical straining appeared to be the primary mechanism of retention in natural soils as ENMs immediately formed micron-scale aggregates, which was exacerbated by coating particles with Suwannee River natural organic matter (NOM) which promote steric hindrance. Small changes in soil pH were observed in natural soils contaminated with ENMs that were largely independent of ENM type and concentration, but differed from controls. These changes may have been due to enhanced release of naturally present pH-altering ions (Mg(2+), H(+)) in the soil via substitution processes. These results suggest ENMs introduced into soil will likely be highly retained near the source zone. Copyright © 2016 Elsevier Ltd. All rights reserved.
Validation of computational non-Newtonian fluid model for membrane bioreactor.
Sørensen, Lasse; Bentzen, Thomas Ruby; Skov, Kristian
2015-01-01
Membrane bioreactor (MBR) systems are often considered as the wastewater treatment method of the future due to their high effluent quality. One of the main problems with such systems is a relative large energy consumption, compared to conventional activated sludge (CAS) systems, which has led to further research in this specific area. A powerful tool for optimizing MBR-systems is computational fluid dynamics (CFD) modelling, which gives researchers the ability to describe the flow in the systems. A parameter which is often neglected in such models is the non-Newtonian properties of active sludge, which is of great importance for MBR systems since they operate at sludge concentrations up to a factor of 10 compared to CAS systems, resulting in strongly shear thinning liquids. A CFD-model is validated against measurements conducted in a system with rotating cross-flow membranes submerged in non-Newtonian liquids, where tangential velocities are measured with a Laser Doppler Anemometer (LDA). The CFD model is found to be capable of modelling the correct velocities in a range of setups, making CFD models a powerful tool for optimization of MBR systems.
Experiments on densely-loaded non-Newtonian slurries in laminar and turbulent pipe flows
NASA Astrophysics Data System (ADS)
Mannheimer, R. J.; Grimley, T. A.; Park, J. T.; Morrow, T. B.
1987-04-01
The structure of non-Newtonian slurries in laminar, transitional, and turbulent flow regimes in pipes is studied. Experiments are conducted in a large-scale pipe slurry flow facility with an inside pipe diameter of 51 mm. Flow measurements including turbulence quantities such as Reynolds stress are taken with a two-component laser-Doppler velocimeter in a transparent test section with a transparent model slurry. Two transparent model slurries have been developed with non-Newtonian rheological properties. Silica gel particles with diameters on the order of one micron are suspended in two different hydrocarbon liquid mixtures with viscosities of 1.19 and 6.39 cS. In rheological measurements with a concentric cylinder viscometer, slurries from both liquid mixtures exhibited slip. From a linear regression analysis with a power-law model, slurries with the higher viscosity fluid had yield values of 80 and 30 dyn/sq cm for silica gel concentrations of 5.6 and 4.0% by weight, respectively, and the exponents were 0.584 and 0.763. The measured refractive index for the transparent slurries is 1.454 where the difference in refractive index between the fluid and silica gel is estimated to be less than 0.001. Bench scale tests with large diameter silica gel particles on the order of 100 microns have produced slurries with excessive turbidity. A silica gel manufactured by a different process which may form a less turbid slurry is currently under investigation.
Flow instabilities during annular displacement of one non-Newtonian fluid by another
NASA Astrophysics Data System (ADS)
Tehrani, M. A.; Bittleston, S. H.; Long, P. J. G.
1993-02-01
This paper describes an experimental setup for axial laminar flow of liquids in the annulus between two eccentered cylinders. The design uses a conductivity method for measuring peak axial velocities around the annulus, and for the determination of displacement efficiency when displacing one fluid by another (displacement efficiency being defined as the ratio of volume of displaced fluid removed from the annulus, to the volume of the annulus, after a given number of annular volumes have been pumped). In an eccentric annulus, lower axial velocity in the narrow side produces “channeling” of the displacing fluid in the wide side and reduces the displacement efficiency. A positive density contrast between the two fluids can increase the efficiency by promoting azimuthal flow of the (denser) displacing fluid towards the narrow side. In this paper we report that gravity driven azimuthal flow is prone to severe instabilities which accelerate the displacement process but may leave behind an immobile strip of the displaced fluid in the narrow side.
Richman, M.W.
1992-12-01
In this quarter, we extended our study of the effects of isotropic boundary vibrations to steady, gravity driven, inclined granular flows. These flows are more complex than those considered last quarter because of the presence of slip and mean velocity gradients at the boundary. Consequently, it was first necessary to modify the boundary conditions derived by Richman (1992) to account for corrections to the flow particle velocity distribution function from velocity gradients. In what follows we only summarize the results obtained.
Physiological non-Newtonian blood flow through single stenosed artery
NASA Astrophysics Data System (ADS)
Mamun, Khairuzzaman; Rahman, Mohammad Matiur; Akhter, Most. Nasrin; Ali, Mohammad
2016-07-01
A numerical simulation to investigate the Non-Newtonian modelling effects on physiological flows in a three dimensional idealized artery with a single stenosis of 85% severity. The wall vessel is considered to be rigid. Oscillatory physiological and parabolic velocity profile has been imposed for inlet boundary condition. Where the physiological waveform is performed using a Fourier series with sixteen harmonics. The investigation has a Reynolds number range of 96 to 800. Low Reynolds number k - ω model is used as governing equation. The investigation has been carried out to characterize two Non-Newtonian constitutive equations of blood, namely, (i) Carreau and (ii) Cross models. The Newtonian model has also been investigated to study the physics of fluid. The results of Newtonian model are compared with the Non-Newtonian models. The numerical results are presented in terms of pressure, wall shear stress distributions and the streamlines contours. At early systole pressure differences between Newtonian and Non-Newtonian models are observed at pre-stenotic, throat and immediately after throat regions. In the case of wall shear stress, some differences between Newtonian and Non-Newtonian models are observed when the flows are minimum such as at early systole or diastole.
Physical-based non-Newtonian fluid animation using SPH
NASA Astrophysics Data System (ADS)
Mao, Hai
Fluids are commonly seen in our daily lives. They exhibit a wide range of motions, which depend on their physical properties, and often result in amazing visual phenomena. Hence, fluid animation is a popular topic in computer graphics. The animation results not only enrich a computer-generated virtual world but have found applications in generating special effects in motion pictures and in computer games. The three-dimensional (3D) Navier-Stokes (NS) equation is a comprehensive mechanical description of the fluid motions. Smoothed Particle Hydrodynamics (SPH) is a popular particle-based fluid modeling formulation. In physical-based fluid animation, the fluid models are based on the 3D NS equation, which can be solved using SPH based methods. Non-Newtonian fluids form a rich class of fluids. Their physical behavior exhibits a strong and complex stress-strain relationship which falls outside the modeling range of Newtonian fluid mechanics. In physical-based fluid animation, most of the fluid models are based on Newtonian fluids, and hence they cannot realistically animate non-Newtonian fluid motions such as stretching, bending, and bouncing. Based on the 3D NS equation and SPH, three original contributions are presented in this dissertation, which address the following three aspects of fluid animation: (1) particle-based non-Newtonian fluids, (2) immiscible fluid-fluid collision, and (3) heating non-Newtonian fluids. Consequently, more varieties of non-Newtonian fluid motions can be animated, which include stretching, bending, and bouncing.
Thermocapillary flow of a non-Newtonian nanoliquid film over an unsteady stretching sheet
NASA Astrophysics Data System (ADS)
Narayana, Mahesha; Metri, Prashant G.; Silvestrov, Sergei
2017-01-01
The influence of surface tension on the laminar flow of a thin film of a non-Newtonian nanoliquid over an unsteady stretching sheet is considered. Surface tension is assumed vary linearly with temperature. An effective medium theory (EMT) based model is used for the thermal conductivity of the nanoliquid. Metal and metal oxide nanoparticles are considered in carboxymethyl cellulose (CMC) - water base liquid. The unsteady boundary layer equations are transformed to a system of non-linear ordinary differential equations with the application of similarity transformations. Resultant two-point boundary value problem is solved numerically using a shooting method together with Runge-Kutta-Fehlberg and Newton-Raphson schemes. The effect of surface tension on the dynamics of the considered problem is presented graphically and analyzed in detail. The clear liquid results form special case of the present study.
Derlon, Nicolas; Mimoso, Joao; Klein, Theresa; Koetzsch, Stefan; Morgenroth, Eberhard
2014-09-01
This study evaluates the effect of the presence of biofilms on membrane surfaces on the quality of permeate produced during Gravity-driven membrane ultrafiltration. GDM ultrafiltration is applied to the decentralized production of drinking water. A second objective was to evaluate to what extent permeate quality is enhanced by pre-treating feed-water (using a packed bed biofilm reactor or a slow sand filter). The influence of the ageing of the biofilm on the permeate quality was evaluated and compared to the effect of virgin membranes. Permeate quality was evaluated in terms of Assimilable Organic Carbon (AOC) content and dissolved organic carbon fractions (e.g. biopolymers). Our results indicate that virgin ultrafiltration membrane remove a small fraction of the AOC and biopolymers (rejection <10%). The presence of a young and thin biofilm on the surface of the ultrafiltration membranes increases the permeate quality due to the degradation of AOC (>80%). However, over long-term the hydrolysis of the organic matter that accumulated on membrane surfaces increases the AOC content of the permeate, thus deteriorating the permeate quality. Pre-treatment of the feed-water help to control the biofilm accumulation and thus to limit the deterioration of the permeate quality. Permeate flux stabilised at average values of 7.5-8.9 L m(-2) h(-1). But the presence of pre-treatment helped to increase permeate flux (+12 and 19%, with the packed bed biofilm reactor and with the slow sand filter, respectively). Overall our study demonstrates that tolerating the presence of biofilm on membrane surface has a beneficial effect on the quality of permeate even if its quantity is decreased.
NASA Astrophysics Data System (ADS)
Jablonská, Danica; Di Celma, Claudio; Tondi, Emanuele
2016-04-01
Gravitational phenomena on the paleoslope of continental margins play a significant role both in redistribution of sediment and formation of new structural features within sedimentary basins worldwide. Mass-transport deposits (MTDs) represent important heterogeneities within the succession and occur on various scales (tens of centimetres to hundreds of metres). Small- to medium-scale MTDs (up to tens of meters) act as layers of different petrophysical properties, whereas large-scale MTDs (tens to hundreds of meters) form both stratigraphic and structural discontinuities (faults, thrusts, erosional surfaces, dykes or injections) within the succession. The Maiolica Formation, Early Cretaceous deep basinal succession cropping out in Gargano Promontory of Southeast Italy is represented by undisturbed intervals of flat-lying thin-bedded, cherty micritic limestone interstratified with intervals of lithologically similar, but structurally distorted beds. For this reason, the studied outcrops provide a good opportunity to characterize the geometry and the internal deformation of small- and medium-scale carbonate MTDs. At the outcrop scale, small- to medium-sized MTDs can be simply identified as sheets of deformed strata alternated with packages of undeformed beds. However, several observed features such as folded stylolites with radially oriented peaks within some of these deformed packages and the presence of large vertical clastic-dyke-like bodies in the succession suggest that some of these deformed packages represent deep-seated basal gliding horizons of large-scale MTDs. In this study, we present MTDs on two different scales that have a crucial influence on the evolution of slope to basinal successions. Moreover, we define the features that distinguish superficial MTDs from the deep-seated gravity-driven deformation horizons within basinal carbonates.
Wzorek, Alicja; Klika, Karel D; Drabowicz, Józef; Sato, Azusa; Aceña, José Luis; Soloshonok, Vadim A
2014-07-14
This work explores the self-disproportionation of enantiomers (SDE) of chiral sulfoxides via achiral, gravity-driven column chromatography using methyl n-pentyl sulfoxide as a case study. A major finding of this work is the remarkable persistence and high magnitude of the SDE for the analyte. Thus, it is the first case where SDE is observed even in the presence of MeOH in the mobile phase. The study demonstrated the practical preparation, in line with theory, of enantiomerically pure (>99.9% ee) samples of methyl n-pentyl sulfoxide starting from a sample of only modest ee (<35%). Remarkably, it was found that the order of elution was inverted, i.e. enantiomerically depleted fractions preceded later eluting enantiomerically enriched ones, when the stationary phase was changed from silica gel to aluminum oxide. To the best of our knowledge, this is the first occurrence of inverted SDE behavior due solely to a change in the stationary phase. Aberrant SDE behavior was observed in that the ee did not always fall continuously during the progression of the chromatography, and this was attributed to the complexity of the system at hand which cannot be described in simple terms such as the formation only of homo- and heterochiral dimers based on a single interaction. The results nevertheless suggest that all compounds with a chiral sulfoxide moiety in their structure are likely to exhibit the SDE phenomenon and thus this work constitutes the first example of SDE predictability. Moreover, it could well be that optical purification based on the SDE phenomenon is a simple, convenient, and inexpensive method for the optical purification of this class of compounds with a high degree of proficiency.
Accuracy of non-Newtonian Lattice Boltzmann simulations
NASA Astrophysics Data System (ADS)
Conrad, Daniel; Schneider, Andreas; Böhle, Martin
2015-11-01
This work deals with the accuracy of non-Newtonian Lattice Boltzmann simulations. Previous work for Newtonian fluids indicate that, depending on the numerical value of the dimensionless collision frequency Ω, additional artificial viscosity is introduced, which negatively influences the accuracy. Since the non-Newtonian fluid behavior is incorporated through appropriate modeling of the dimensionless collision frequency, a Ω dependent error EΩ is introduced and its influence on the overall error is investigated. Here, simulations with the SRT and the MRT model are carried out for power-law fluids in order to numerically investigate the accuracy of non-Newtonian Lattice Boltzmann simulations. A goal of this accuracy analysis is to derive a recommendation for an optimal choice of the time step size and the simulation Mach number, respectively. For the non-Newtonian case, an error estimate for EΩ in the form of a functional is derived on the basis of a series expansion of the Lattice Boltzmann equation. This functional can be solved analytically for the case of the Hagen-Poiseuille channel flow of non-Newtonian fluids. With the help of the error functional, the prediction of the global error minimum of the velocity field is excellent in regions where the EΩ error is the dominant source of error. With an optimal simulation Mach number, the simulation is about one order of magnitude more accurate. Additionally, for both collision models a detailed study of the convergence behavior of the method in the non-Newtonian case is conducted. The results show that the simulation Mach number has a major impact on the convergence rate and second order accuracy is not preserved for every choice of the simulation Mach number.
Non-Newtonian Aspects of Artificial Intelligence
NASA Astrophysics Data System (ADS)
Zak, Michail
2016-05-01
The challenge of this work is to connect physics with the concept of intelligence. By intelligence we understand a capability to move from disorder to order without external resources, i.e., in violation of the second law of thermodynamics. The objective is to find such a mathematical object described by ODE that possesses such a capability. The proposed approach is based upon modification of the Madelung version of the Schrodinger equation by replacing the force following from quantum potential with non-conservative forces that link to the concept of information. A mathematical formalism suggests that a hypothetical intelligent particle, besides the capability to move against the second law of thermodynamics, acquires such properties like self-image, self-awareness, self-supervision, etc. that are typical for Livings. However since this particle being a quantum-classical hybrid acquires non-Newtonian and non-quantum properties, it does not belong to the physics matter as we know it: the modern physics should be complemented with the concept of the information force that represents a bridge to intelligent particle. As a follow-up of the proposed concept, the following question is addressed: can artificial intelligence (AI) system composed only of physical components compete with a human? The answer is proven to be negative if the AI system is based only on simulations, and positive if digital devices are included. It has been demonstrated that there exists such a quantum neural net that performs simulations combined with digital punctuations. The universality of this quantum-classical hybrid is in capability to violate the second law of thermodynamics by moving from disorder to order without external resources. This advanced capability is illustrated by examples. In conclusion, a mathematical machinery of the perception that is the fundamental part of a cognition process as well as intelligence is introduced and discussed.
CFD simulation of gas and non-Newtonian fluid two-phase flow in anaerobic digesters.
Wu, Binxin
2010-07-01
This paper presents an Eulerian multiphase flow model that characterizes gas mixing in anaerobic digesters. In the model development, liquid manure is assumed to be water or a non-Newtonian fluid that is dependent on total solids (TS) concentration. To establish the appropriate models for different TS levels, twelve turbulence models are evaluated by comparing the frictional pressure drops of gas and non-Newtonian fluid two-phase flow in a horizontal pipe obtained from computational fluid dynamics (CFD) with those from a correlation analysis. The commercial CFD software, Fluent12.0, is employed to simulate the multiphase flow in the digesters. The simulation results in a small-sized digester are validated against the experimental data from literature. Comparison of two gas mixing designs in a medium-sized digester demonstrates that mixing intensity is insensitive to the TS in confined gas mixing, whereas there are significant decreases with increases of TS in unconfined gas mixing. Moreover, comparison of three mixing methods indicates that gas mixing is more efficient than mixing by pumped circulation while it is less efficient than mechanical mixing.
Squeeze film lubrication for non-Newtonian fluids with application to manual medicine.
Chaudhry, Hans; Bukiet, Bruce; Roman, Max; Stecco, Antonio; Findley, Thomas
2013-01-01
In this paper, we computed fluid pressure and force on fascia sheets during manual therapy treatments using Squeeze Film Lubrication theory for non-Newtonian fluids. For this purpose, we developed a model valid for three dimensional fluid flow of a non-Newtonian liquid. Previous models considered only one-dimensional flows in two dimensions. We applied this model to compare the one-dimensional flow of HA, considered as a lubricating fluid, around or within the fascia during sliding, vibration, and back-and-forth sliding manipulation treatment techniques. The fluid pressure of HA increases dramatically as fascia is deformed during manual therapies. The fluid force increases more during vertical vibratory manipulation treatment than in constant sliding, and back and forth motion. The variation of fluid pressure/force causes HA to flow near the edges of the fascial area under manipulation in sliding and back and forth motion which may result in greater lubrication. The fluid pressure generated in manual therapy techniques may improve sliding and permit muscles to work more efficiently.
Resuspension of non-Newtonian slurries by submerged jet-nozzles
Reshma, Reshma; Daas, Mutaz; Srivastava, Rajiv; Tansel, Berrin
2007-07-15
Experiments were conducted to determine the fluid velocity required for resuspension and removal of the radioactive waste sludge, which is characterized as a non-Newtonian fluid, from the tanks at the Savannah river site (SRS) (Georgia, USA) to accelerate the closure of the tanks with high level waste (HLW). Five different non-Newtonian fluids, which simulated the actual waste characteristics, were used to investigate the resuspension of the slurries with a jet-nozzle mixer. The laboratory tests were conducted at different flow rates and jet-nozzle orientations in a cylindrical tank with 0.3-m diameter and 0.46 m in height. Resuspension of the slurries was achieved by the submerged jets produced by two horizontal discharge nozzles located under the liquid level and positioned at 180 from each other. The fluids exhibited Bingham plastic behavior; therefore, the mixing power depends not only on the Reynolds number but also on the yield stress and high shear viscosity. A similarity analysis was performed to determine the effective cleaning radius (ECR) of the jet. The mixing efficiency was evaluated by visual analysis of the images during the experiments conducted at three nozzle orientations at 0 , 45 , and 90 and two nozzle exit velocities of 2.33 m/s and 0.56 m/s. The centerline velocity decayed with the distance from the jet-nozzle. The experimental results were compared with other mixing models. (author)
Spreading of completely wetting, non-Newtonian fluids with non-power-law rheology.
Min, Qi; Duan, Yuan-Yuan; Wang, Xiao-Dong; Liang, Zhan-Peng; Lee, Duu-Jong; Su, Ay
2010-08-01
Spreading non-Newtonian liquids with non-power-law rheology on completely wetting surfaces are seldom investigated. This study assessed the wetting behavior of polydimethylsiloxane (PDMS), a Newtonian fluid, two carboxymethylcellulose (CMC) sodium solutions, a PDMS+2%w/w silica nanoparticle suspension and three polyethylene glycol (PEG400)+5-10%w/w silica nanoparticle suspensions (non-power-law fluids) on a mica surface. The theta(D)-U and R-t data for spreading drops of the six tested, non-power-law fluids can be described by power-law wetting models. We propose that this behavior is attributable to a uniform shear rate (a few tens to a few hundreds of s(-1)) distributed over the thin-film regime that controls spreading dynamics. Estimated film thickness was below the resolution of an optical microscope for direct observation. Approximating a general non-Newtonian fluid spreading as a power-law fluid greatly simplifies theoretical analysis and data interpretation.
Numerical simulation of the non-Newtonian mixing layer
NASA Technical Reports Server (NTRS)
Azaiez, Jalel; Homsy, G. M.
1993-01-01
This work is a continuing effort to advance our understanding of the effects of polymer additives on the structures of the mixing layer. In anticipation of full nonlinear simulations of the non-Newtonian mixing layer, we examined in a first stage the linear stability of the non-Newtonian mixing layer. The results of this study show that, for a fluid described by the Oldroyd-B model, viscoelasticity reduces the instability of the inviscid mixing layer in a special limit where the ratio (We/Re) is of order 1 where We is the Weissenberg number, a measure of the elasticity of the flow, and Re is the Reynolds number. In the present study, we pursue this project with numerical simulations of the non-Newtonian mixing layer. Our primary objective is to determine the effects of viscoelasticity on the roll-up structure. We also examine the origin of the numerical instabilities usually encountered in the simulations of non-Newtonian fluids.
Flow Curve Determination for Non-Newtonian Fluids.
ERIC Educational Resources Information Center
Tjahjadi, Mahari; Gupta, Santosh K.
1986-01-01
Describes an experimental program to examine flow curve determination for non-Newtonian fluids. Includes apparatus used (a modification of Walawender and Chen's set-up, but using a 50cc buret connected to a glass capillary through a Tygon tube), theoretical information, procedures, and typical results obtained. (JN)
Flow Curve Determination for Non-Newtonian Fluids.
ERIC Educational Resources Information Center
Tjahjadi, Mahari; Gupta, Santosh K.
1986-01-01
Describes an experimental program to examine flow curve determination for non-Newtonian fluids. Includes apparatus used (a modification of Walawender and Chen's set-up, but using a 50cc buret connected to a glass capillary through a Tygon tube), theoretical information, procedures, and typical results obtained. (JN)
NASA Astrophysics Data System (ADS)
Kordilla, Jannes; Noffz, Torsten; Dentz, Marco; Tartakovsky, Alexandre
2017-04-01
Fractures and fracture networks have a high potential to contribute to the formation of preferential flow paths, and thus control important catchment-scale parameters, such as aquifer vulnerability, mass arrival times and dispersion dynamics. Particularly, the unsaturated zone of fractured porous aquifers exhibits highly space- and time-variant coupling of phase saturation and flow (transport) dynamics and remains an extremely challenging aspect of vadose zone research. Non-Darcian and highly non-linear unsaturated flow modes, strongly deviate from the classical laminar and low Capillary number flow regimes and therefore most volume-effective approaches fails to capture important flow and transport characteristics. Here we study unsaturated gravity-driven free-surface flows on a synthetic surface intersected by a horizontal fracture and demonstrate the importance of flow modes (droplet; rivulet) on the partitioning behavior at the fracture intersection. We present (1) laboratory experiments, (2) three-dimensional smoothed particle hydrodynamics (SPH) simulations using a heavily parallelized code, and (3) an analytical solution. The flow-rate-dependent mode switching from droplets to rivulets is reproduced by the SPH model, and the transition ranges agree with the laboratory experiments. We show that flow modes heavily influence the bypass behavior. Flows favoring the formation of droplets exhibit a much stronger bypass capacity compared to rivulet flows, where nearly the whole fluid mass is initially stored within the horizontal fracture. This behavior is demonstrated for a multi-inlet laboratory setup where the inlet-specific flow rate is chosen so that either a droplet or rivulet flow persists. The effect of fluid buffering within the horizontal fracture is presented in terms of dimensionless fracture inflow so that characteristic scaling regimes can be recovered. For both cases (rivulets and droplets), the flow within the horizontal fracture transitions into a
NASA Astrophysics Data System (ADS)
Basteev, A. V.; Dashkov, A. V.; Kravchenko, O. V.; Repalova, O. N.; Forfutdinov, V. V.
2010-07-01
The process of growth of the boundary crystallized phase in the motion of a heated non-Newtonian fluid in a channel with a cold wall has been studied experimentally. As the fluid, polypropylene with pseudoplastic properties was used. Experimental curves of the growth of the wall crystallized phase as a function of time were obtained for different values of the initial fluid melt temperature. The experimental value of the Nusselt number at the solid-liquid interface has been computed.
Girardo, Salvatore; Cingolani, Roberto; Pisignano, Dario
2007-10-28
We present a study of the rheological phenomenology of a non-Newtonian glass former within hybrid microchannels above the vitrification region. We determined the temperature behavior of the viscosity, which is well fitted by a Vogel-Fulcher-Tamman law for shear rates between 4 x 10(-2) and 9 x 10(-1) s(-1). The microflow viscosity was compared with previously reported conductivity data of the investigated molecular system. Our findings provide an insight into the coupling between the structural dynamics in the bulk and that within the microchannels, suggesting lithographically defined microfluidic systems as promising tools for the investigation of the rheological properties of complex liquids.
Coalescence of drops and bubbles rising through a non-Newtonian fluid in a tube.
Al-Matroushi, Eisa; Borhan, Ali
2009-04-01
We conducted an experimental study of the interaction and coalescence of two drops (of the same fluid) or bubbles translating under the action of buoyancy in a cylindrical tube. The close approach of two Newtonian fluid particles of different size in a non-Newtonian continuous phase was examined using image analysis, and measurements of the coalescence time are reported for various particle size ratios, Bond numbers, and particle-to-suspending-fluid viscosity ratios. The flow disturbance behind the leading bubble and the viscoelastic nature of the continuous phase seemed to retard bubble coalescence. The time scale for coalescence of liquid drops in highly elastic continuous phase was influenced by the relative motion of the drops and their coalescence behavior.
EXPERIMENTAL BUBBLE FORMATION IN A LARGE SCALE SYSTEM FOR NEWTONIAN AND NONNEWTONIAN FLUIDS
Leishear, R; Michael Restivo, M
2008-06-26
The complexities of bubble formation in liquids increase as the system size increases, and a photographic study is presented here to provide some insight into the dynamics of bubble formation for large systems. Air was injected at the bottom of a 28 feet tall by 30 inch diameter column. Different fluids were subjected to different air flow rates at different fluid depths. The fluids were water and non-Newtonian, Bingham plastic fluids, which have yield stresses requiring an applied force to initiate movement, or shearing, of the fluid. Tests showed that bubble formation was significantly different in the two types of fluids. In water, a field of bubbles was formed, which consisted of numerous, distributed, 1/4 to 3/8 inch diameter bubbles. In the Bingham fluid, large bubbles of 6 to 12 inches in diameter were formed, which depended on the air flow rate. This paper provides comprehensive photographic results related to bubble formation in these fluids.
NASA Astrophysics Data System (ADS)
Di Federico, V.; Longo, S.; Ciriello, V.; Chiapponi, L.
2016-12-01
Several environmental contaminants and remediation agents exhibit rheological complexity. Crude oil and displacing agents in EOR operations are rheologically nonlinear. These applications prompt the need for a theoretical analysis of non-Newtonian flow in natural porous and fractured media, considering gravity-driven and confined flows, different geometries and diverse boundary conditions. We present a review of the results obtained by our group concerning the modeling of power-law fluids, as this constitutive law is amenable to self-similar solutions which may act as benchmarks even for more complex rheology. First, closed form results were obtained for gravity currents advancing in plane or cylindrical geometry, deriving scalings for current length and thickness. Analogous results were obtained for confined flows in various geometries; here, scalings were obtained for pressure front and pressure field. Based on these benchmarks, the analytical models were refined introducing two additional factors: medium heterogeneity and topographic control. The inherent hetehrogeneity of natural media was modeled within a simplified framework considering continuous variations of spatial properties. Topographic control was introduced considering flows in porous channels of different shapes. Both factors proved relevant for the spreading of gravity currents as they influence the extent and shape of porous domain invaded by the contaminant, or reached by the remediation agent. Our theoretical results were validated against multiple sets of experiments, conducted with different combinations of spreading scenarios and types of heterogeneity or channelization. Two basic experimental setups were employed, adopting either reconstructed porous media made of glass beads, or Hele-Shaw analogues. To this end, existing Hele-Shaw analogies for porous flow of power-law fluids were extended to heterogeneous media. All scalings derived for the current front and thickness were confirmed by our
Steady flow of a non-Newtonian fluid through a contraction
NASA Technical Reports Server (NTRS)
Gatski, T. B.; Lumley, J. L.
1978-01-01
A steady-state analysis is conducted to examine the basic flow structure of a non-Newtonian fluid in a domain including an inflow region, a contraction region, and an outflow region. A Cartesian grid system is used throughout the entire flow domain, including the contraction region, thus creating an irregular grid cell structure adjacent to the curved boundary. At node points adjacent to the curved boundary symmetry conditions are derived for the different flow variables in order to solve the governing difference equations. Attention is given to the motion and non-Newtonian constitutive equations, the boundary conditions, the numerical modeling of the non-Newtonian equations, the stream function contour lines for the non-Newtonian fluid, the vorticity contour lines for the non-Newtonian fluid, the velocity profile across the contraction, and the shear stress contour lines for the non-Newtonian fluid.
Steady flow of a non-Newtonian fluid through a contraction
NASA Technical Reports Server (NTRS)
Gatski, T. B.; Lumley, J. L.
1978-01-01
A steady-state analysis is conducted to examine the basic flow structure of a non-Newtonian fluid in a domain including an inflow region, a contraction region, and an outflow region. A Cartesian grid system is used throughout the entire flow domain, including the contraction region, thus creating an irregular grid cell structure adjacent to the curved boundary. At node points adjacent to the curved boundary symmetry conditions are derived for the different flow variables in order to solve the governing difference equations. Attention is given to the motion and non-Newtonian constitutive equations, the boundary conditions, the numerical modeling of the non-Newtonian equations, the stream function contour lines for the non-Newtonian fluid, the vorticity contour lines for the non-Newtonian fluid, the velocity profile across the contraction, and the shear stress contour lines for the non-Newtonian fluid.
Measurement of viscosity of highly viscous non-Newtonian fluids by means of ultrasonic guided waves.
Kazys, Rymantas; Mazeika, Liudas; Sliteris, Reimondas; Raisutis, Renaldas
2014-04-01
In order to perform monitoring of the polymerisation process, it is necessary to measure viscosity. However, in the case of non-Newtonian highly viscous fluids, viscosity starts to be dependent on the vibration or rotation frequency of the sensing element. Also, the sensing element must possess a sufficient mechanical strength. Some of these problems may be solved applying ultrasonic measurement methods, however until now most of the known investigations were devoted to measurements of relatively low viscosities (up to a few Pas) of Newtonian liquids. The objective of the presented work is to develop ultrasonic method for measurement of viscosity of high viscous substances during manufacturing process in extreme conditions. For this purpose the method based on application of guided Lamb waves possessing the predominant component of in-plane displacements (the S0 and the SH0 modes) and propagating in an aluminium planar waveguide immersed in a viscous liquid has been investigated. The simulations indicated that in the selected modes mainly in-plane displacements are dominating, therefore the attenuation of those modes propagating in a planar waveguide immersed in a viscous liquid is mainly caused by viscosity of the liquid. The simulation results were confirmed by experiments. All measurements were performed in the viscosity standard Cannon N2700000. Measurements with the S0 wave mode were performed at the frequency of 500kHz. The SH0 wave mode was exited and used for measurements at the frequency of 580kHz. It was demonstrated that by selecting the particular mode of guided waves (S0 or SH0), the operation frequency and dimensions of the aluminium waveguide it is possible to get the necessary viscosity measurement range and sensitivity. The experiments also revealed that the measured dynamic viscosity is strongly frequency dependent and as a characteristic feature of non-Newtonian liquids is much lower than indicated by the standards. Therefore, in order to get the
Turbulence modeling based on non-Newtonian constitutive laws
NASA Astrophysics Data System (ADS)
Mompean, G.; Qiu, X.; Schmitt, F. G.; Thompson, R.
2011-12-01
This work revisits the analogy between Newtonian turbulence and non-Newtonian laminar flows. Several direct numerical simulations (DNS) data of a plane channel flow, for a large range of Reynolds numbers (180 <= Reτ <= 2000) were explored. The profiles of mean velocity and second moment quantities were used to extract viscometric functions in the non-Newtonian modeling framework. The Reynolds stress tensor is expressed in terms of a set of basis kinematic tensors based on a projection of a nonlinear framework. The coefficients of the model are given as functions of the intensity of the mean strain tensor. The apparent eddy turbulent viscosity, the first and second normal stress differences are presented as function of the shear rate. One of the advantages of the new algebraic nonlinear power law constitutive equation derived in the paper, is that is only dependent on the mean velocity gradient and can be integrated up to the wall.
Time decay rates of non-Newtonian flows in RN+
NASA Astrophysics Data System (ADS)
Dong, Bo-Qing; Chen, Zhi-Min
2006-12-01
This paper is concerned with time decay rates of the weak solutions of an incompressible non-Newtonian fluid motion model in half spaces for n[greater-or-equal, slanted]3. With the use of the spectral decomposition of the Stokes operator and Lp-Lq estimates, it is shown that the weak solutions decay in L2 norm like when the initial velocity u0[set membership, variant]L2[intersection]Lr for 1[less-than-or-equals, slant]r<2. The higher decay rates are obtained, if u0 satisfies the additional moment condition Moreover, the error estimates between the non-Newtonian flow and the Navier-Stokes flow are discussed.
Geophysical Aspects of Non-Newtonian Fluid Mechanics
NASA Astrophysics Data System (ADS)
Balmforth, N. J.; Craster, R. V.
Non-Newtonian fluid mechanics is a vast subject that has several journals partly, or primarily, dedicated to its investigation (Journal of Non-Newtonian Fluid Mechanics, Rheologica Acta, Journal of Fluid Mechanics, Journal of Rheology, amongst others). It is an area of active research, both for industrial fluid problems and for applications elsewhere, notably geophysically motivated issues such as the flow of lava and ice, mud slides, snow avalanches and debris flows. The main motivati on for this research activity is that, apart from some annoyingly common fluids such as air and water, virtually no fluid is actually Newtonian (that is, having a simple linear relation between stress and strain-rate characterized by a constant viscosity). Several textbooks are useful sources of information; for example, [1-3] are standard texts giving mathematical and engineering perspectives upon the subject. In these lecture notes, Ancey's chapter on rheology (Chap. 3) gives further introduction.
Verification of vertically rotating flume using non-newtonian fluids
Huizinga, R.J.
1996-01-01
Three tests on non-Newtonian fluids were used to verify the use of a vertically rotating flume (VRF) for the study of the rheological properties of debris flow. The VRF is described and a procedure for the analysis of results of tests made with the VRF is presented. The major advantages of the VRF are a flow field consistent with that found in nature, a large particle-diameter threshold, inexpensive operation, and verification using several different materials; the major limitations are a lack of temperature control and a certain error incurred from the use of the Bingham plastic model to describe a more complex phenomenon. Because the VRF has been verified with non-Newtonian fluids as well as Newtonian fluids, it can be used to measure the rheological properties of coarse-grained debris-flow materials.
Non-Newtonian Viscosity of Complex-Plasma Fluids
Ivlev, A. V.; Kompaneets, R.; Hoefner, H.; Sidorenko, I.; Morfill, G. E.; Steinberg, V.
2007-04-06
Investigations of shear flows in three-dimensional complex-plasma fluids produced in a dc discharge were carried out. The shear was induced either by an inhomogeneous gas flow or by a laser beam. The viscosity of complex plasmas was measured over a broad range of shear rates, up to the hydrodynamic limit when the discreteness becomes important. Analysis of the measurements reveals non-Newtonian behavior of complex plasmas accompanied by substantial shear thinning.
Non-newtonian viscosity of complex-plasma fluids.
Ivlev, A V; Steinberg, V; Kompaneets, R; Höfner, H; Sidorenko, I; Morfill, G E
2007-04-06
Investigations of shear flows in three-dimensional complex-plasma fluids produced in a dc discharge were carried out. The shear was induced either by an inhomogeneous gas flow or by a laser beam. The viscosity of complex plasmas was measured over a broad range of shear rates, up to the hydrodynamic limit when the discreteness becomes important. Analysis of the measurements reveals non-Newtonian behavior of complex plasmas accompanied by substantial shear thinning.
Stabilization of Rayleigh-Taylor instability in a non-Newtonian incompressible complex plasma
Garai, S.; Janaki, M. S.; Chakrabarti, N.
2015-03-15
The stabilization of Rayleigh-Taylor (RT) instability is investigated in a non-Newtonian unmagnetized dusty plasma with an experimentally verified model of shear flow rate dependent viscosity. It has been found that non-Newtonian property has also a significant role in stabilization of RT instability along with velocity shear stabilization in the short wavelength regime. The effect of the non-Newtonian parameters is more profound in the higher velocity shear rate regime. A detailed study is reported on the role of non-Newtonian effect on RT instability with conventional dust fluid equations using standard numerical eigenvalue analysis.
Kheyfets, Vitaly O.; Kieweg, Sarah L.
2013-01-01
HIV/AIDS is a growing global pandemic. A microbicide is a formulation of a pharmaceutical agent suspended in a delivery vehicle, and can be used by women to protect themselves against HIV infection during intercourse. We have developed a three-dimensional (3D) computational model of a shear-thinning power-law fluid spreading under the influence of gravity to represent the distribution of a microbicide gel over the vaginal epithelium. This model, accompanied by a new experimental methodology, is a step in developing a tool for optimizing a delivery vehicle's structure/function relationship for clinical application. We compare our model with experiments in order to identify critical considerations for simulating 3D free-surface flows of shear-thinning fluids. Here we found that neglecting lateral spreading, when modeling gravity-induced flow, resulted in up to 47% overestimation of the experimental axial spreading after 90 s. In contrast, the inclusion of lateral spreading in 3D computational models resulted in rms errors in axial spreading under 7%. In addition, the choice of the initial condition for shape in the numerical simulation influences the model's ability to describe early time spreading behavior. Finally, we present a parametric study and sensitivity analysis of the power-law parameters' influence on axial spreading, and to examine the impact of changing rheological properties as a result of dilution or formulation conditions. Both the shear-thinning index (n) and consistency (m) impacted the spreading length and deceleration of the moving front. The sensitivity analysis showed that gels with midrange m and n values (for the ranges in this study) would be most sensitive (over 8% changes in spreading length) to 10% changes (e.g., from dilution) in both rheological properties. This work is applicable to many industrial and geophysical thin-film flow applications of non-Newtonian fluids; in addition to biological applications in microbicide drug delivery
Kheyfets, Vitaly O; Kieweg, Sarah L
2013-06-01
HIV/AIDS is a growing global pandemic. A microbicide is a formulation of a pharmaceutical agent suspended in a delivery vehicle, and can be used by women to protect themselves against HIV infection during intercourse. We have developed a three-dimensional (3D) computational model of a shear-thinning power-law fluid spreading under the influence of gravity to represent the distribution of a microbicide gel over the vaginal epithelium. This model, accompanied by a new experimental methodology, is a step in developing a tool for optimizing a delivery vehicle's structure/function relationship for clinical application. We compare our model with experiments in order to identify critical considerations for simulating 3D free-surface flows of shear-thinning fluids. Here we found that neglecting lateral spreading, when modeling gravity-induced flow, resulted in up to 47% overestimation of the experimental axial spreading after 90 s. In contrast, the inclusion of lateral spreading in 3D computational models resulted in rms errors in axial spreading under 7%. In addition, the choice of the initial condition for shape in the numerical simulation influences the model's ability to describe early time spreading behavior. Finally, we present a parametric study and sensitivity analysis of the power-law parameters' influence on axial spreading, and to examine the impact of changing rheological properties as a result of dilution or formulation conditions. Both the shear-thinning index (n) and consistency (m) impacted the spreading length and deceleration of the moving front. The sensitivity analysis showed that gels with midrange m and n values (for the ranges in this study) would be most sensitive (over 8% changes in spreading length) to 10% changes (e.g., from dilution) in both rheological properties. This work is applicable to many industrial and geophysical thin-film flow applications of non-Newtonian fluids; in addition to biological applications in microbicide drug delivery.
NASA Astrophysics Data System (ADS)
Gray, J. D.; Owen, I.; Escudier, M. P.
2007-10-01
Dimensional analysis has been applied to an unsteady pulsatile flow of a shear-thinning power-law non-Newtonian liquid. An experiment was then designed in which both Newtonian and non-Newtonian liquids were used to model blood flow through a large-scale (38.5 mm dia.), simplified, rigid arterial junction (a distal anastomosis of a femorodistal bypass). The flow field within the junction was obtained by Particle Imaging Velocimetry and near-wall velocities were used to calculate the wall shear stresses. Dimensionless wall shear stresses were obtained at different points in the cardiac cycle for two different but dynamically similar non-Newtonian fluids; the good agreement between the measured dimensionless wall shear stresses confirm the validity of the dimensional analysis. However, blood exhibits a constant viscosity at high-shear rates and to obtain complete dynamic similarity between large-scale experiments and life-scale flows, the high-shear viscosity also needs to be included in the analysis. How this might be done is discussed in the paper.
Convection in ice I with non-Newtonian rheology: Application to the icy Galilean satellites
NASA Astrophysics Data System (ADS)
Barr, Amy Courtright
2004-12-01
Observations from the Galileo spacecraft suggest that the Jovian icy satellites Europa, Ganymede, and Callisto have liquid water oceans beneath their icy surfaces. The outer ice I shells of the satellites represent a barrier between their surfaces and their oceans and serve to decouple fluid motions in their deep interiors from their surfaces. Understanding heat and mass transport by convection within the outer ice I shells of the satellites is crucial to understanding their geophysical and astrobiological evolution. Recent laboratory experiments suggest that deformation in ice I is accommodated by several different creep mechanisms. Newtonian deformation creep accommodates strain in warm ice with small grain sizes. However, deformation in ice with larger grain sizes is controlled by grain-size-sensitive and dislocation creep, which are non-Newtonian. Previous studies of convection have not considered this complex rheological behavior. This thesis revisits basic geophysical questions regarding heat and mass transport in the ice I shells of the satellites using a composite Newtonian/ non-Newtonian rheology for ice I. The composite rheology is implemented in a numerical convection model developed for Earth's mantle to study the behavior of an ice I shell during the onset of convection and in the stagnant lid convection regime. The conditions required to trigger convection in a conductive ice I shell depend on the grain size of the ice, and the amplitude and wavelength of temperature perturbation issued to the ice shell. If convection occurs, the efficiency of heat and mass transport is dependent on the ice grain size as well. If convection occurs, fluid motions in the ice shells enhance the nutrient flux delivered to their oceans, and coupled with resurfacing events, may provide a sustainable biogeochemical cycle. The results of this thesis suggest that evolution of ice grain size in the satellites and the details of how tidal dissipation perturbs the ice shell to
Ochowiak, Marek; Matuszak, Magdalena; Włodarczak, Sylwia
2017-08-01
The article contains results of the experimental studies on atomization process of inhaled drugs and aqueous solutions of glycerol with aqueous solutions of glycerol polyacrylamide (Rokrysol WF1) in pneumatic nebulizers. In experiments, the different concentration of aqueous solutions of glycerol polyacrylamide have been tested. In addition, the effect of nebulizer design on atomization process has been determined. The one of the main elements of medical pneumatic nebulizer is nebulizer cup. The experiment with this scope is new and is very important from the point of view of aerosol therapy. The results have been obtained by the use of the digital microphotography technique. In order to determine a physicochemical properties of tested liquids, a rheological measurements and measurements of the surface tension were carried out. The differences between characteristics of aerosol for the liquids have been observed. The analysis of the droplets size distributions shows that the different diameters of droplets for Newtonian and non-Newtonian fluids have been formed during atomization in pneumatic nebulizers equipped with different nebulizer cups. The effect of the mouthpiece location on the droplets diameters has been shown. Precise design of nebulizer and nebulizer cups, and also physicochemical properties of atomized liquids are of high importance in order to the effectiveness of drug delivery to patient's respiratory tracts.
The Non-Newtonian Rheology of Real Magmas: insights into 3D microstructures
NASA Astrophysics Data System (ADS)
Pistone, M.; Caricchi, L.; Ulmer, P.; Reusser, E.; Marone, F.; Burlini, L.
2010-12-01
We present high-resolution 3D microstructures of three-phase magmas composed of melt, bubbles and crystals in different proportions deformed at magmatic pressure and temperature conditions. This study aims to constrain the dependence of rheological and physical properties of magmas on the viscosity of the silicate melt, the applied deformation rate, the relative contents of crystals and bubbles and on the interactions between these phases. The starting material is composed of a hydrous haplogranitic melt containing H2O (2.26 wt%) and CO2 (624 ppm) and different proportions of quartz crystals (between 24 and 65 vol%; 63-125 μm in diameter) and bubbles (between 9 and 12 vol%; 5-150 μm in diameter). Experiments were performed in simple shear using a HT-HP internally-heated Paterson-type rock deformation apparatus (Paterson and Olgaard, 2000) at strain rates ranging between 5×10-5 s-1 and 4×10-3 s-1, at a constant pressure of 200 MPa and temperatures ranging between 723 and 1023 K. Synchrotron based X-ray tomographic microscopy performed at the TOMCAT beamline (Stampanoni et al., 2006) at the Swiss Light Source enabled quantitative evaluation of the 3D microstructure. At high temperature and low strain rate conditions the silicate melt behaves as a Newtonian liquid (Webb and Dingwell, 1990). Higher deformation rates and the contemporary presence of gas bubbles and solid crystals make magma rheology more complex and non-Newtonian behaviour occurs. In all experimental runs two different non-Newtonian effects were observed: shear thinning (decrease of viscosity with increasing strain rate) in high crystal-content magmas (55-65 vol% crystals; 9-10 vol% bubbles) and shear thickening (increase of viscosity with increasing strain rate) in magmas at lower degree of crystallinity (24 vol% crystals; 12 vol% bubbles). Both behaviours were observed at intermediate crystal-content (44 vol% crystals; 12 vol% bubbles), with an initial thickening that subsequently gives way to
Crossover phenomena in non-Newtonian viscous fingers at a finite viscosity ratio
NASA Astrophysics Data System (ADS)
Nagatani, Takashi
1990-04-01
A viscous fingering of non-Newtonian fluids at a finite viscosity ratio is considered in order to study the effect of non-Newtonian fluid on crossover phenomena. The crossover from the fractal pattern to the dense structure is investigated by using a two-parameter position-space renormalization-group method. The global flow diagrams in two-parameter space are obtained. It is found that there are two nontrivial fixed points: the fractal point and the Eden point. When the viscosity ratio is finite, the pattern must eventually cross over to the dense structure. The dependences of the crossover phenomena on the parameter k, which describes the different non-Newtonian fluids, are shown. It is found that the non-Newtonian fluids have important effects on the fractal point and the crossover line but the crossover exponent is independent of the non-Newtonian property.
Non-Newtonian flow of dilute ferrofluids in a uniform magnetic field.
Weng, Huei Chu; Chen, Chieh-Li; Chen, Cha'o-Kuang
2008-11-01
Nonequilibrium magnetization states predict non-Newtonian ferrofluid properties. It is desirable to understand the corresponding flow fields and characteristics. In this study, we derive a magnetoviscosity expression coming from the effective-field method and describing the shear-thinning non-Newtonian behavior of dilute ferrofluids with finite magnetic anisotropy. A mathematical model is developed of non-Newtonian plane flow with respect to shear and pressure driving mechanisms in the presence of an applied stationary uniform magnetic field oriented in the direction perpendicular to vorticity. The results reveal that the non-Newtonian effect tends to increase the velocity and angular velocity but to reduce the magnetization strength. Moreover, an enhanced flow rate and reduced flow drag may be obtained. The maximum non-Newtonian effect is found at a ratio of the Néel relaxation time to the Brownian relaxation time of the order of 0.1.
Fast imaging technique to study drop impact dynamics of non-Newtonian fluids.
Xu, Qin; Peters, Ivo; Wilken, Sam; Brown, Eric; Jaeger, Heinrich
2014-03-05
In the field of fluid mechanics, many dynamical processes not only occur over a very short time interval but also require high spatial resolution for detailed observation, scenarios that make it challenging to observe with conventional imaging systems. One of these is the drop impact of liquids, which usually happens within one tenth of millisecond. To tackle this challenge, a fast imaging technique is introduced that combines a high-speed camera (capable of up to one million frames per second) with a macro lens with long working distance to bring the spatial resolution of the image down to 10 µm/pixel. The imaging technique enables precise measurement of relevant fluid dynamic quantities, such as the flow field, the spreading distance and the splashing speed, from analysis of the recorded video. To demonstrate the capabilities of this visualization system, the impact dynamics when droplets of non-Newtonian fluids impinge on a flat hard surface are characterized. Two situations are considered: for oxidized liquid metal droplets we focus on the spreading behavior, and for densely packed suspensions we determine the onset of splashing. More generally, the combination of high temporal and spatial imaging resolution introduced here offers advantages for studying fast dynamics across a wide range of microscale phenomena.
Controlling and minimizing fingering instabilities in non-Newtonian fluids.
Fontana, João V; Dias, Eduardo O; Miranda, José A
2014-01-01
The development of the viscous fingering instability in Hele-Shaw cells has great practical and scientific importance. Recently, researchers have proposed different strategies to control the number of interfacial fingering structures, or to minimize as much as possible the amplitude of interfacial disturbances. Most existing studies address the situation in which an inviscid fluid displaces a viscous Newtonian fluid. In this work, we report on controlling and minimizing protocols considering the situation in which the displaced fluid is a non-Newtonian, power-law fluid. The necessary changes on the controlling schemes due to the shear-thinning and shear thickening nature of the displaced fluid are calculated analytically and discussed.
Particle manipulations in non-Newtonian microfluidics: A review.
Lu, Xinyu; Liu, Chao; Hu, Guoqing; Xuan, Xiangchun
2017-08-15
Microfluidic devices have been widely used since 1990s for diverse manipulations of particles (a general term of beads, cells, vesicles, drops, etc.) in a variety of applications. Compared to the active manipulation via an externally imposed force field, the passive manipulation of particles exploits the flow-induced intrinsic lift and/or drag to control particle motion with several advantages. Along this direction, inertial microfluidics has received tremendous interest in the past decade due to its capability to handle a large volume of samples at a high throughput. This inertial lift-based approach in Newtonian fluids, however, becomes ineffective and even fails for small particles and/or at low flow rates. Recent studies have demonstrated the potential of elastic lift in non-Newtonian fluids for manipulating particles with a much smaller size and over a much wider range of flow rates. The aim of this article is to provide an overview of the various passive manipulations, including focusing, separation, washing and stretching, of particles that have thus far been demonstrated in non-Newtonian microfluidics. Copyright © 2017 Elsevier Inc. All rights reserved.
Electro-osmotic mobility of non-Newtonian fluids.
Zhao, Cunlu; Yang, Chun
2011-03-23
Electrokinetically driven microfluidic devices are usually used to analyze and process biofluids which can be classified as non-Newtonian fluids. Conventional electrokinetic theories resulting from Newtonian hydrodynamics then fail to describe the behaviors of these fluids. In this study, a theoretical analysis of electro-osmotic mobility of non-Newtonian fluids is reported. The general Cauchy momentum equation is simplified by incorporation of the Gouy-Chapman solution to the Poisson-Boltzmann equation and the Carreau fluid constitutive model. Then a nonlinear ordinary differential equation governing the electro-osmotic velocity of Carreau fluids is obtained and solved numerically. The effects of the Weissenberg number (Wi), the surface zeta potential (ψ¯s), the power-law exponent(n), and the transitional parameter (β) on electro-osmotic mobility are examined. It is shown that the results presented in this study for the electro-osmotic mobility of Carreau fluids are quite general so that the electro-osmotic mobility for the Newtonian fluids and the power-law fluids can be obtained as two limiting cases.
Intermittent outgassing through a non-Newtonian fluid.
Divoux, Thibaut; Bertin, Eric; Vidal, Valérie; Géminard, Jean-Christophe
2009-05-01
We report an experimental study of the intermittent dynamics of a gas flowing through a column of a non-Newtonian fluid. In a given range of the imposed constant flow rate, the system spontaneously alternates between two regimes: bubbles emitted at the bottom either rise independently one from the other or merge to create a winding flue which then connects the bottom air entrance to the free surface. The observations are reminiscent of the spontaneous changes in the degassing regime observed on volcanoes and suggest that, in the nature, such a phenomenon is likely to be governed by the non-Newtonian properties of the magma. We focus on the statistical distribution of the lifespans of the bubbling and flue regimes in the intermittent steady state. The bubbling regime exhibits a characteristic time whereas, interestingly, the flue lifespan displays a decaying power-law distribution. The associated exponent, which is significantly smaller than the value 1.5 often reported experimentally and predicted in some standard intermittency scenarios, depends on the fluid properties and can be interpreted as the ratio of two characteristic times of the system.
Electro-osmotic mobility of non-Newtonian fluids
Zhao, Cunlu; Yang, Chun
2011-01-01
Electrokinetically driven microfluidic devices are usually used to analyze and process biofluids which can be classified as non-Newtonian fluids. Conventional electrokinetic theories resulting from Newtonian hydrodynamics then fail to describe the behaviors of these fluids. In this study, a theoretical analysis of electro-osmotic mobility of non-Newtonian fluids is reported. The general Cauchy momentum equation is simplified by incorporation of the Gouy–Chapman solution to the Poisson–Boltzmann equation and the Carreau fluid constitutive model. Then a nonlinear ordinary differential equation governing the electro-osmotic velocity of Carreau fluids is obtained and solved numerically. The effects of the Weissenberg number (Wi), the surface zeta potential (ψ¯s), the power-law exponent(n), and the transitional parameter (β) on electro-osmotic mobility are examined. It is shown that the results presented in this study for the electro-osmotic mobility of Carreau fluids are quite general so that the electro-osmotic mobility for the Newtonian fluids and the power-law fluids can be obtained as two limiting cases. PMID:21503161
Air Sparging for Mixing Non-Newtonian Slurries
Bamberger, Judith A.; Enderlin, Carl W.; Tzemos, Spyridon
2010-01-01
The mechanics of air sparger systems have been primarily investigated for aqueous-based Newtonian fluids. Tilton et al. (1982) [1] describes the fluid mechanics of air sparging systems in non-Newtonian fluids as having two primary flow regions. A center region surrounding the sparger, referred to as the region of bubbles (ROB), contains upward flow due to the buoyant driving force of the rising bubbles. In an annular region, outside the ROB, referred to as the zone of influence (ZOI), the fluid flow is reversed and is opposed to the direction of bubble rise. Outside the ZOI the fluid is unaffected by the air sparger system. The flow regime in the ROB is often turbulent, and the flow regime in the ZOI is laminar; the flow regime outside the ZOI is quiescent. Tests conducted with shear thinning non-Newtonian fluid in a 34-in. diameter tank showed that the ROB forms an approximately inverted cone that is the envelop of the bubble trajectories. The depth to which the air bubbles reach below the sparger nozzle is a linear function of the air-flow rate. The recirculation time through the ZOI was found to vary proportionally with the inverse square of the sparging air-flow rate. Visual observations of the ROB were made in both water and Carbopol®. The bubbles released from the sparge tube in Carbopol® were larger than those in water
NASA Astrophysics Data System (ADS)
Tan, Yunkai; He, Zhenbin; Xu, Tao; Fang, Xiaoming; Gao, Xuenong; Zhang, Zhengguo
2017-09-01
An aqueous solution of Xanthan Gum (XG) at a weight fraction as high as 0.2% was used as the base liquid, the stable MWCNTs-dispersed non-Newtonian nanofluids at different weight factions of MWCNTs was prepared. The base fluid and all nanofluids show pseudoplastic (shear-thinning) rheological behavior. Experiments were performed to compare the shell-side forced convective heat transfer coefficient and pressure drop of non-Newtonian nanofluids to those of non-Newtonian base fluid in an integrally helical baffle heat exchanger with low-finned tubes. The experimental results showed that the enhancement of the convective heat transfer coefficient increases with an increase in the Peclet number and the nanoparticle concentration. For nanofluids with 1.0, 0.5 and 0.2 wt% of multi-walled carbon nanotubes (MWCNTs), the heat transfer coefficients respectively augmented by 24.3, 13.2 and 4.7% on average and the pressure drops become larger than those of the base fluid. The comprehensive thermal performance factor is higher than one and increases with an increasing weight fraction of MWCNTs. A remarkable heat transfer enhancement in the shell side of helical baffle heat exchanger with low-finned tubes can be obtained by adding MWCNTs into XG aqueous solution based on thermal resistance analysis. New correlations have been suggested for the shell-side friction coefficient and the Nusselt numbers of non-Newtonian nanofluids and give very good agreement with experimental data.
Mansour, A.; Chigier, N.
1993-12-31
In this progress report the authors report on progress in making experimental measurements to describe the rheological properties of non-Newtonian fluids. Non-Newtonian liquids exhibit a non linear relationship between the shear stress and the shear rate. A typical time-dependent rheological phenomenon is thixotropy. Thixotropic fluids show a limited decrease in the shear viscosity of the fluid with time under a suddenly applied constant stress. Thixotropic fluids also show a hysteresis loop and a decaying stress on the shear stress-shear rate plot. Here the authors are using a power law model to describe the behavior of such non-Newtonian liquids.
Convex functions and some inequalities in terms of the Non-Newtonian Calculus
NASA Astrophysics Data System (ADS)
Unluyol, Erdal; Salas, Seren; Iscan, Imdat
2017-04-01
Differentiation and integration are basic operations of calculus and analysis. Indeed, they are many versions of the subtraction and addition operations on numbers, respectively. From 1967 till 1970 Michael Grossman and Robert Katz [1] gave definitions of a new kind of derivative and integral, converting the roles of subtraction and addition into division and multiplication, and thus establish a new calculus, called Non-Newtonian Calculus. So, in this paper, it is investigated to the convex functions and some inequalities in terms of Non-Newtonian Calculus. Then we compare with the Newtonian and Non-Newtonian Calculus.
Sinking of spherical slablets through a non-Newtonian mantle
NASA Astrophysics Data System (ADS)
Stegman, D. R.; Crameri, F.; Petersen, R. I.; Tackley, P. J.
2013-12-01
The dominant driving force for plate tectonics is slab pull, in which sinking slabs pull the trailing plate. Forward plate velocities are typically similar in magnitude (7 cm/yr) as estimates for sinking velocities of slabs through the upper mantle. However, these estimates are based on data for slabs that are coherent into the transition zone as well as models that considered the upper mantle to be entirely Newtonian. Dislocation creep in the upper mantle can strongly influence mantle flow, and is likely activated for flow around vertically sinking slabs in the uppermost mantle. Thus, it is possible that in some scenarios, a non-Newtonian mantle will have an influence on plate motions but it is unclear to what degree. To address this question, we investigate how the non-Newtonian rheology modifies the sinking velocities of slablets (spherical, negatively buoyant and highly viscous blobs). The model set-up is similar to a Stokes sphere sinking, but is in 2-D cartesian with temperature-and stress-dependent rheology. For these numerical models, we use the StagYY code and also includes a pseudo-free surface (';sticky air') with a thin surface thermal boundary. The sinking blob is both highly viscous and compositionally dense, but is the same temperature as the background fluid which eliminates thermal diffusion and associated variations in thermal buoyancy. The model domain is 2x1 and allows enough distance to the sidewalls so that sinking velocites are not influenced by the boundary conditions. We compare our results with those previously obtained for salt diapirs rising through a power-law rheology mantle/crust (Weinberg, 1993; Weinberg and Podladchikov, 1994) which provided both numerical and analytic results. Previous results indicate a speed-up of an order of magnitude is possible. We then extend the models and analysis to mantle convection systems that include for single-sided subduction. Surface plate motions are driven by the subducting slabs to which they are
NASA Astrophysics Data System (ADS)
Kuchumov, Alex G.; Gilev, Valeriy; Popov, Vitaliy; Samartsev, Vladimir; Gavrilov, Vasiliy
2014-02-01
The paper presents an experimental study of pathological human bile taken from the gallbladder and bile ducts. The flow dependences were obtained for different types of bile from patients with the same pathology, but of different age and sex. The parameters of the Casson's and Carreau's equations were found for bile samples. Results on the hysteretic bile behavior at loading-unloading tests are also presented, which proved that the pathologic bile is a non-Newtonian thixotropic liquid. The viscosity of the gallbladder bile was shown to be higher compared to the duct bile. It was found that at higher shear stress the pathological bile behaves like Newtonian fluid, which is explained by reorientation of structural components. Moreover, some pathological bile flow in the biliary system CFD simulations were performed. The velocity and pressure distributions as well as flow rates in the biliary segments during the gallbladder refilling and emptying phases are obtained. The results of CFD simulations can be used for surgeons to assess the patient's condition and choose an adequate treatment.
Inline Ultrasonic Rheometry of a Non-Newtonian Waste Simulant
Pfund, David M.; Pappas, Richard A.
2004-03-31
This is a discussion of non-invasive determination of the viscosity of a non-Newtonian fluid in laminar pipe flow over the range of shear rates present in the pipe. The procedure requires knowledge of the flow profile in and the pressure drop along the long straight run of pipe. The profile is determined by using a pulsed ultrasonic Doppler velocimeter. This approach is ideal for making non-invasive, real-time measurements for monitoring and control. Rheograms of a shear thinning, thixotropic gel which is often used as a Hanford waste simulant are presented. The operating parameters and limitations of the ultrasound based instrument will be discussed. The component parts of the instrument have been packaged into a unit for field use. The presentation also discusses the features and engineering optimizations done to enhance field usability of the instrument.
Laminar boundary-layer flow of non-Newtonian fluid
NASA Technical Reports Server (NTRS)
Lin, F. N.; Chern, S. Y.
1979-01-01
A solution for the two-dimensional and axisymmetric laminar boundary-layer momentum equation of power-law non-Newtonian fluid is presented. The analysis makes use of the Merk-Chao series solution method originally devised for the flow of Newtonian fluid. The universal functions for the leading term in the series are tabulated for n from 0.2 to 2. Equations governing the universal functions associated with the second and the third terms are provided. The solution together with either Lighthill's formula or Chao's formula constitutes a simple yet general procedure for the calculation of wall shear and surface heat transfer rate. The theory was applied to flows over a circular cylinder and a sphere and the results compared with published data.
Electrokinetic flow of non-Newtonian fluids in microchannels.
Berli, Claudio L A; Olivares, María L
2008-04-15
A theoretical description of the electrokinetic flow of non-Newtonian fluids through slit and cylindrical microchannels is presented. Calculations are based on constitutive models of the fluid viscosity, and take into account wall depletion effects of colloids and polymer solutions. The resulting equations allow one to predict the flow rate and electric current as functions of the simultaneously applied electric potential and pressure gradients. It is found that (i) nonlinear effects induced by the shear-dependent viscosity are limited to the pressure-driven component of the flow, and (ii) the reciprocity between electroosmosis and streaming current is complied. Thus a generalized form of the force-flux relations is proposed, which is of interest in microfluidic applications.
Laminar boundary-layer flow of non-Newtonian fluid
NASA Technical Reports Server (NTRS)
Lin, F. N.; Chern, S. Y.
1979-01-01
A solution for the two-dimensional and axisymmetric laminar boundary-layer momentum equation of power-law non-Newtonian fluid is presented. The analysis makes use of the Merk-Chao series solution method originally devised for the flow of Newtonian fluid. The universal functions for the leading term in the series are tabulated for n from 0.2 to 2. Equations governing the universal functions associated with the second and the third terms are provided. The solution together with either Lighthill's formula or Chao's formula constitutes a simple yet general procedure for the calculation of wall shear and surface heat transfer rate. The theory was applied to flows over a circular cylinder and a sphere and the results compared with published data.
Dynamic wetting with viscous Newtonian and non-Newtonian fluids.
Wei, Y; Rame, E; Walker, L M; Garoff, S
2009-11-18
We examine various aspects of dynamic wetting with viscous Newtonian and non-Newtonian fluids. Rather than concentrating on the mechanisms that relieve the classic contact line stress singularity, we focus on the behavior in the wedge flow near the contact line which has the dominant influence on wetting with these fluids. Our experiments show that a Newtonian polymer melt composed of highly flexible molecules exhibits dynamic wetting behavior described very well by hydrodynamic models that capture the critical properties of the Newtonian wedge flow near the contact line. We find that shear thinning has a strong impact on dynamic wetting, by reducing the drag of the solid on the fluid near the contact line, while the elasticity of a Boger fluid has a weaker impact on dynamic wetting. Finally, we find that other polymeric fluids, nominally Newtonian in rheometric measurements, exhibit deviations from Newtonian dynamic wetting behavior.
Skyrmions: a showcase for non-Newtonian kinematics
NASA Astrophysics Data System (ADS)
Beekman, Aron; Nagaosa, Naoto
2014-03-01
Consisting of hundreds or thousands of spins, skyrmions in magnets can nevertheless be regarded as individual particles that keep their identity due to topological protection. These particles interact with externally imposed waves like electric current or magnons. We have recently shown that they do this in a completely counterintuitive, non-Newtonian way. For instance, elastic scattering causes the skyrmion to move in the direction opposite to the incoming wave. The underlying reason is that the skyrmion momentum is descendant from the ferromagnetic dynamics, such that the skyrmion center of mass coordinates are each other's canonical conjugates. Here we argue that this is a general feature of dynamics of excitations in media with broken time-reversal symmetry, and is strongly related to the existence of Berry phases. Supported by the Foreign Postdoctoral Researcher program at RIKEN.
The physics of coal liquid slurry atomization. Final report to Department of Energy - PETC
Chigier, N.; Mansour, A.
1995-10-01
The stability of turbulent columns of liquid injected into a quiescent environment was studied. Laser Doppler Anemometry measurements of the flow patterns and turbulence characteristics in free liquid jets were made. Turbulence decay along Newtonian jets was investigated along with the effects of turbulence on the resulting droplet size distributions after breakup. The rate of decay of turbulence properties along the jet were investigated. Disintegration of liquid jets injected into a high-velocity gas stream has also been studied. Newtonian and non-Newtonian liquids were studied with particular emphasis on the non-Newtonian rheological characteristics. Determination was made of the extent that the addition of high molecular weight polymer to liquids change the breakup process. Shear thinning, extension thinning and extension thickening fluids were investigated. Shear viscosities were measured over five decades of shear rates. The contraction flow technique was also used for measurement of the extensional viscosity of non-Newtonian liquids. The die-swell technique was also used to determine the first normal stress difference. The near field produced by a co-axial airblast atomizer was investigated using the phase Doppler particle analyzer. Whether or not the classical wave mechanism and empirical models reported for airblast atomization of low viscosity liquid are applicable to airblast atomization of viscous non-Newtonian liquids was determined. The theoretical basis of several models which give the best fit to the experimental data for airblast atomization of non-Newtonian liquids was also discussed. The accuracy of the wave mechanism-based models in predicting droplets sizes after breakup of viscous non-Newtonian liquids using an airblast atomizer has also been demonstrated.
Using ultrasonic Doppler velocimetry to investigate the mixing of non-Newtonian fluids
NASA Astrophysics Data System (ADS)
Patel, Dineshkumar; Ein-Mozaffari, Farhad; Mehrvar, Mehrab
2012-12-01
Mixing is a critical unit operation, which is widely used in chemical and allied industries. Mixing of non-Newtonian fluids is a challenging task due to the complex rheology exhibited by these fluids. Pseudoplastic fluids with yield stress are an important class of non-Newtonian fluids. In this study, we utilized ultrasonic Doppler velocimetry (UDV) to explore the flow field generated by different impellers in the agitation of xanthan gum solutions and pulp suspensions, which are yield-pseudoplastic fluids.
Effect of non-Newtonian viscosity on the fluid-dynamic characteristics in stenotic vessels
NASA Astrophysics Data System (ADS)
Huh, Hyung Kyu; Ha, Hojin; Lee, Sang Joon
2015-08-01
Although blood is known to have shear-thinning and viscoelastic properties, the effects of such properties on the hemodynamic characteristics in various vascular environments are not fully understood yet. For a quantitative hemodynamic analysis, the refractive index of a transparent blood analogue needs to be matched with that of the flowing conduit in order to minimize the errors according to the distortion of the light. In this study, three refractive index-matched blood analogue fluids with different viscosities are prepared—one Newtonian and two non-Newtonian analogues—which correspond to healthy blood with 45 % hematocrit (i.e., normal non-Newtonian) and obese blood with higher viscosity (i.e., abnormal non-Newtonian). The effects of the non-Newtonian rheological properties of the blood analogues on the hemodynamic characteristics in the post-stenosis region of an axisymmetric stenosis model are experimentally investigated using particle image velocimetry velocity field measurement technique and pathline flow visualization. As a result, the centerline jet flow from the stenosis apex is suppressed by the shear-thinning feature of the blood analogues when the Reynolds number is smaller than 500. The lengths of the recirculation zone for abnormal and normal non-Newtonian blood analogues are 3.67 and 1.72 times shorter than that for the Newtonian analogue at Reynolds numbers smaller than 200. The Reynolds number of the transition from laminar to turbulent flow for all blood analogues increases as the shear-thinning feature increases, and the maximum wall shear stresses in non-Newtonian fluids are five times greater than those in Newtonian fluids. However, the shear-thinning effect on the hemodynamic characteristics is not significant at Reynolds numbers higher than 1000. The findings of this study on refractive index-matched non-Newtonian blood analogues can be utilized in other in vitro experiments, where non-Newtonian features dominantly affect the flow
Effects of non-Newtonian gravity on the properties of strange stars
NASA Astrophysics Data System (ADS)
Lu, Zhen-Yan; Peng, Guang-Xiong; Zhou, Kai
2017-02-01
The properties of strange star matter are studied in the equivparticle model with inclusion of non-Newtonian gravity. It is found that the inclusion of non-Newtonian gravity makes the equation of state stiffer if Witten’s conjecture is true. Correspondingly, the maximum mass of strange stars becomes as large as two times the solar mass, and the maximum radius also becomes bigger. The coupling to boson mass ratio has been constrained within the stability range of strange quark matter.
Aspects of non-Newtonian flow and displacement in porous media
Shah, C.; Yortsos, Y.C.
1993-02-01
The rheology of many heavy oils has been shown to be non-Newtonian, Bingham plastics being one manifestation of heavy oil flow. In EOR applications, non-Newtonian fluids such as low concentration polymer solutions, emulsions, gels etc. are simultaneously injected to increase the viscosity of driving agents that displace oil. Such rheologically complex fluids are used to improve sweep efficiencies, divert displacing fluids and block swept zones. The present study has been undertaken to understand the flow of non-Newtonian fluids through porous media. The work considered involves the numerical (pore network) modeling of both single and multiphase flow of power-law and Bingham plastic fluids in network-like porous media. We consider aspects of both single- and multi-phase flow and displacement. Section 2 describes elementary aspects of non-Newtonian flow and some simple models for porous media. Viscoelastic effects in the flow of non-Newtonian fluids are also discussed. The section includes a brief literature review on non-Newtonian flow in porous media. Section 3 describes single-phase flow.
Mathematical Analysis of Non-Newtonian Blood Flow in Stenosis Narrow Arteries
Sriyab, Somchai
2014-01-01
The flow of blood in narrow arteries with bell-shaped mild stenosis is investigated that treats blood as non-Newtonian fluid by using the K-L model. When skin friction and resistance of blood flow are normalized with respect to non-Newtonian blood in normal artery, the results present the effect of stenosis length. When skin friction and resistance of blood flow are normalized with respect to Newtonian blood in stenosis artery, the results present the effect of non-Newtonian blood. The effect of stenosis length and effect of non-Newtonian fluid on skin friction are consistent with the Casson model in which the skin friction increases with the increase of ither stenosis length or the yield stress but the skin friction decreases with the increase of plasma viscosity coefficient. The effect of stenosis length and effect of non-Newtonian fluid on resistance of blood flow are contradictory. The resistance of blood flow (when normalized by non-Newtonian blood in normal artery) increases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length. The resistance of blood flow (when normalized by Newtonian blood in stenosis artery) decreases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length. PMID:25587350
Theoretical studies of non-Newtonian and Newtonian fluid flow through porous media
Wu, Yu-Shu.
1990-02-01
A comprehensive theoretical study has been carried out on the flow behavior of both single and multiple phase non-Newtonian fluids in porous media. This work is divided into three parts: development of numerical and analytical solutions; theoretical studies of transient flow of non-Newtonian fluids in porous media; and applications of well test analysis and displacement efficiency evaluation to field problems. A fully implicit, integral finite difference model has been developed for simulation of non-Newtonian and Newtonian fluid flow through porous media. Several commonly-used rheological models of power-law and Bingham plastic non-Newtonian fluids have been incorporated in the simulator. A Buckley-Leverett type analytical solution for one-dimensional, immiscible displacement involving non-Newtonian fluids in porous media has been developed. An integral method is also presented for the study of transient flow of Bingham fluids in porous media. In addition, two well test analysis methods have been developed for analyzing pressure transient tests of power-law and Bingham fluids, respectively. Applications are included to demonstrate this new technology. The physical mechanisms involved in immiscible displacement with non-Newtonian fluids in porous media have been studied using the Buckley-Leverett type analytical solution. In another study, an idealized fracture model has been used to obtain some insights into the flow of a power-law fluid in a double-porosity medium. Transient flow of a general pseudoplastic fluid has been studied numerically. 125 refs., 91 figs., 12 tabs.
Mathematical analysis of non-Newtonian blood flow in stenosis narrow arteries.
Sriyab, Somchai
2014-01-01
The flow of blood in narrow arteries with bell-shaped mild stenosis is investigated that treats blood as non-Newtonian fluid by using the K-L model. When skin friction and resistance of blood flow are normalized with respect to non-Newtonian blood in normal artery, the results present the effect of stenosis length. When skin friction and resistance of blood flow are normalized with respect to Newtonian blood in stenosis artery, the results present the effect of non-Newtonian blood. The effect of stenosis length and effect of non-Newtonian fluid on skin friction are consistent with the Casson model in which the skin friction increases with the increase of either stenosis length or the yield stress but the skin friction decreases with the increase of plasma viscosity coefficient. The effect of stenosis length and effect of non-Newtonian fluid on resistance of blood flow are contradictory. The resistance of blood flow (when normalized by non-Newtonian blood in normal artery) increases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length. The resistance of blood flow (when normalized by Newtonian blood in stenosis artery) decreases when either the plasma viscosity coefficient or the yield stress increases, but it decreases with the increase of stenosis length.
Analysis of non-Newtonian effects on Low-Density Lipoprotein accumulation in an artery.
Iasiello, Marcello; Vafai, Kambiz; Andreozzi, Assunta; Bianco, Nicola
2016-06-14
In this work, non-Newtonian effects on Low-Density Lipoprotein (LDL) transport across an artery are analyzed with a multi-layer model. Four rheological models (Carreau, Carreau-Yasuda, power-law and Newtonian) are used for the blood flow through the lumen. For the non-Newtonian cases, the arterial wall is modeled with a generalized momentum equation. Convection-diffusion equation is used for the LDL transport through the lumen, while Staverman-Kedem-Katchalsky, combined with porous media equations, are used for the LDL transport through the wall. Results are presented in terms of filtration velocity, Wall Shear Stresses (WSS) and concentration profiles. It is shown that non-Newtonian effects on mass transport are negligible for a healthy intramural pressure value. Non-Newtonian effects increase slightly with intramural pressure, but Newtonian assumption can still be considered reliable. Effects of arterial size are also analyzed, showing that Newtonian assumption can be considered valid for both medium and large arteries, in predicting LDL deposition. Finally, non-Newtonian effects are also analyzed for an aorta-common iliac bifurcation, showing that Newtonian assumption is valid for mass transport at low Reynolds numbers. At a high Reynolds number, it has been shown that a non-Newtonian fluid model can have more impact due to the presence of flow recirculation.
Numerical simulation of non-Newtonian blood flow dynamics in human thoracic aorta.
Caballero, A D; Laín, S
2015-08-01
Three non-Newtonian blood viscosity models plus the Newtonian one are analysed for a patient-specific thoracic aorta anatomical model under steady-state flow conditions via wall shear stress (WSS) distribution, non-Newtonian importance factors, blood viscosity and shear rate. All blood viscosity models yield a consistent WSS distribution pattern. The WSS magnitude, however, is influenced by the model used. WSS is found to be the lowest in the vicinity of the three arch branches and along the distal walls of the branches themselves. In this region, the local non-Newtonian importance factor and the blood viscosity are elevated, and the shear rate is low. The present study revealed that the Newtonian assumption is a good approximation at mid-and-high flow velocities, as the greater the blood flow, the higher the shear rate near the arterial wall. Furthermore, the capabilities of the applied non-Newtonian models appeared at low-flow velocities. It is concluded that, while the non-Newtonian power-law model approximates the blood viscosity and WSS calculations in a more satisfactory way than the other non-Newtonian models at low shear rates, a cautious approach is given in the use of this blood viscosity model. Finally, some preliminary transient results are presented.
Theoretical Studies of Non-Newtonian and Newtonian Fluid Flowthrough Porous Media
Wu, Y.S.
1990-02-01
A comprehensive theoretical study has been carried out on the flow behavior of both single and multiple phase non-Newtonian fluids in porous media. This work is divided into three parts: (1) development of numerical and analytical solutions; (2) theoretical studies of transient flow of non-Newtonian fluids in porous media; and (3) applications of well test analysis and displacement efficiency evaluation to field problems. A fully implicit, integral finite difference model has been developed for simulation of non-Newtonian and Newtonian fluid flow through porous media. Several commonly-used rheological models of power-law and Bingham plastic non-Newtonian fluids have been incorporated in the simulator. A Buckley-Leverett type analytical solution for one-dimensional, immiscible displacement involving non-Newtonian fluids in porous media has been developed. Based on this solution, a graphic approach for evaluating non-Newtonian displacement efficiency has been developed. The Buckley-Leverett-Welge theory is extended to flow problems with non-Newtonian fluids. An integral method is also presented for the study of transient flow of Bingham fluids in porous media. In addition, two well test analysis methods have been developed for analyzing pressure transient tests of power-law and Bingham fluids, respectively. Applications are included to demonstrate this new technology. The physical mechanisms involved in immiscible displacement with non-Newtonian fluids in porous media have been studied using the Buckley-Leverett type analytical solution. The results show that this kind of displacement is a complicated process and is determined by the rheological properties of the non-Newtonian fluids and the flow conditions, in addition to relative permeability data. In another study, an idealized fracture model has been used to obtain some insights into the flow of a power-law fluid in a double-porosity medium. For flow at a constant rate, non-Newtonian flow behavior in a fractured
Huang, Y; Wang, Y L; Wong, T N
2017-08-22
Monodispersity and fast generation are innate advantages of microfluidic droplets. Other than the normally adopted simple Newtonian fluids such as a water/oil emulsion system, fluids with complex rheology, namely, non-Newtonian fluids, which are being widely adopted in industries and bioengineering, have gained increasing research interest on the microscale. However, challenges occur in controlling the dynamic behavior due to their complex properties. In this sense, the AC electric field with merits of fast response and easiness in fulfilling "Lab on a chip" has attracted our attention. We design and fabricate flow-focusing microchannels with non-contact types of electrodes for the investigation. We firstly compare the formation of a non-Newtonian droplet with that of a Newtonian one under an AC electric field and discover that viscoelasticity contributes to the discrepancies significantly. Then we explore the effect of AC electric fields on the filament thinning and droplet formation dynamics of one non-Newtonian fluid which has a similar rheological behavior to bio samples, such as DNA or blood samples. We investigate the dynamics of the thinning process of the non-Newtonian filament under the influence of an AC electric field and implement a systematic exploration of the non-Newtonian droplet generation influenced by parameters such as the flow conditions (flow rate Q, capillary number Ca), fluid property (Weissenberg number Wi), applied voltage (U) and frequency (f) of the AC electric field. We present the dependencies of the flow condition and electric field on the non-Newtonian droplet formation dynamics, and conclude with an operating diagram, taking into consideration all the above-mentioned parameters. Results show that the electric field plays a critical role in controlling the thinning process of the filament and the size of the generated droplet. Furthermore, for the first time, we quantitatively measure the flow field of the non-Newtonian droplet
Non-Newtonian effects of blood flow on hemodynamics in distal vascular graft anastomoses.
Chen, Jie; Lu, Xi-Yun; Wang, Wen
2006-01-01
Non-Newtonian fluid flow in a stenosed coronary bypass is investigated numerically using the Carreau-Yasuda model for the shear thinning behavior of the blood. End-to-side coronary bypass anastomosis is considered in a simplified model geometry where the host coronary artery has a 75% severity stenosis. Different locations of the bypass graft to the stenosis and different flow rates in the graft and in the host artery are studied. Particular attention is given to the non-Newtonian effect of the blood on the primary and secondary flow patterns in the host coronary artery and the wall shear stress (WSS) distribution there. Interaction between the jet flow from the stenosed artery and the flow from the graft is simulated by solving the three-dimensional Navier-Stokes equation coupled with the non-Newtonian constitutive model. Results for the non-Newtonian flow, the Newtonian flow and the rescaled Newtonian flow are presented. Significant differences in axial velocity profiles, secondary flow streamlines and WSS between the non-Newtonian and Newtonian fluid flows are revealed. However, reasonable agreement between the non-Newtonian and the rescaled Newtonian flows is found. Results from this study support the view that the residual flow in a partially occluded coronary artery interacts with flow in the bypass graft and may have significant hemodynamic effects in the host vessel downstream of the graft. Non-Newtonian property of the blood alters the flow pattern and WSS distribution and is an important factor to be considered in simulating hemodynamic effects of blood flow in arterial bypass grafts.
NASA Astrophysics Data System (ADS)
De Vita, F.; de Tullio, M. D.; Verzicco, R.
2016-04-01
This work focuses on the comparison between Newtonian and non-Newtonian blood flows through a bileaflet mechanical heart valve in the aortic root. The blood, in fact, is a concentrated suspension of cells, mainly red blood cells, in a Newtonian matrix, the plasma, and consequently its overall behavior is that of a non-Newtonian fluid owing to the action of the cells' membrane on the fluid part. The common practice, however, assumes the blood in large vessels as a Newtonian fluid since the shear rate is generally high and the effective viscosity becomes independent of the former. In this paper, we show that this is not always the case even in the aorta, the largest artery of the systemic circulation, owing to the pulsatile and transitional nature of the flow. Unexpectedly, for most of the pulsating cycle and in a large part of the fluid volume, the shear rate is smaller than the threshold level for the blood to display a constant effective viscosity and its shear thinning character might affect the system dynamics. A direct inspection of the various flow features has shown that the valve dynamics, the transvalvular pressure drop and the large-scale features of the flow are very similar for the Newtonian and non-Newtonian fluid models. On the other hand, the mechanical damage of the red blood cells (hemolysis), induced by the altered stress values in the flow, is larger for the non-Newtonian fluid model than for the Newtonian one.
The physics of coal liquid slurry atomization. Annual topical report, 14 March 1993--14 March 1994
Chigier, N.
1994-06-01
The stability of turbulent columns of liquid injected into a quiescent environment has been studied. Turbulence decay along Newtonian jets was investigated along with the effects of turbulence on the resulting droplet size distributions after breakup. Disintegration of liquid jets injected into a high-velocity gas stream has also been studied. Newtonian and non-Newtonian liquids were studied with particular emphasis on the non-Newtonian rheological characteristics. Determination was made of the extent that the addition of high molecular weight polymer to liquids changes the breakup process. Shear thinning, extension thinning and extension thickening fluids were investigated. The non-Newtonian viscosities were measured over five decades of shear rates for 12 solutions of polymeric materials. By using the die-swell technique, the first normal stress difference was determined for all solutions. By using the contraction flow technique, the extensional viscosity levels were determined for the most viscous solutions. The near field produced by a co-axial airblast atomizer was investigated using the phase Doppler particle analyzer. The classical wave mechanism and empirical models reported for air-blast atomization of low viscosity liquid were shown to be applicable to air-blast atomization of viscous non-Newtonian liquids. The theoretical basis of several models which give the best fit to the experimental data for air-blast atomization of non-Newtonian liquids was addressed. Conclusions to date are discussed for the following areas: Turbulence characteristics in liquid jets; The effect of turbulence on the stability of liquid columns; The rheology of mobile polymeric solutions; and Air blast atomization of non-Newtonian liquids.
Dynamic viscosity measurement in non-Newtonian graphite nanofluids.
Duan, Fei; Wong, Ting Foong; Crivoi, Alexandru
2012-07-02
: The effective dynamic viscosity was measured in the graphite water-based nanofluids. The shear thinning non-Newtonian behavior is observed in the measurement. On the basis of the best fitting of the experimental data, the viscosity at zero shear rate or at infinite shear rate is determined for each of the fluids. It is found that increases of the particle volume concentration and the holding time period of the nanofluids result in an enhancement of the effective dynamic viscosity. The maximum enhancement of the effective dynamic viscosity at infinite rate of shear is more than 24 times in the nanofluids held for 3 days with the volume concentration of 4% in comparison with the base fluid. A transmission electron microscope is applied to reveal the morphology of aggregated nanoparticles qualitatively. The large and irregular aggregation of the particles is found in the 3-day fluids in the drying samples. The Raman spectra are extended to characterize the D and G peaks of the graphite structure in the nanofluids. The increasing intensity of the D peak indicates the nanoparticle aggregation growing with the higher concentration and the longer holding time of the nanofluids. The experimental results suggest that the increase on effective dynamic viscosity of nanofluids is related to the graphite nanoparticle aggregation in the fluids.
Dynamic viscosity measurement in non-Newtonian graphite nanofluids
2012-01-01
The effective dynamic viscosity was measured in the graphite water-based nanofluids. The shear thinning non-Newtonian behavior is observed in the measurement. On the basis of the best fitting of the experimental data, the viscosity at zero shear rate or at infinite shear rate is determined for each of the fluids. It is found that increases of the particle volume concentration and the holding time period of the nanofluids result in an enhancement of the effective dynamic viscosity. The maximum enhancement of the effective dynamic viscosity at infinite rate of shear is more than 24 times in the nanofluids held for 3 days with the volume concentration of 4% in comparison with the base fluid. A transmission electron microscope is applied to reveal the morphology of aggregated nanoparticles qualitatively. The large and irregular aggregation of the particles is found in the 3-day fluids in the drying samples. The Raman spectra are extended to characterize the D and G peaks of the graphite structure in the nanofluids. The increasing intensity of the D peak indicates the nanoparticle aggregation growing with the higher concentration and the longer holding time of the nanofluids. The experimental results suggest that the increase on effective dynamic viscosity of nanofluids is related to the graphite nanoparticle aggregation in the fluids. PMID:22747975
Turbulent Entrainment into Non-Newtonian Fluid Mud Gravity Currents
NASA Astrophysics Data System (ADS)
Jacobson, Michael; Testik, Firat
2011-11-01
This study presents insights into turbulent entrainment of ambient water into fluid mud gravity currents. It is well established that fluid mud suspensions exhibit pseudo-plastic behavior. Gravity current laboratory experiments were conducted for constant-volume release configuration with different initial concentrations of fluid mud, representing different rheological properties (i.e. different Power-law model constants). A high quality data set of concentration and velocity profiles of fluid mud gravity currents was collected to calculate the entrainment velocity, we. The entrainment ratio (E =we / U , U - characteristic velocity) was calculated following the well-accepted Morton-Taylor-Turner entrainment hypothesis, which states that the inflow across the edge of a turbulent flow is proportional to some characteristic velocity. The entrainment ratio was further measured qualitatively using a light opaqueness technique. A semi-empirical parameterization for the entrainment ratio is proposed. The findings of this study are expected to be of significance for modeling various non-Newtonian gravity currents, in particular for modeling fluid mud gravity currents generated during dredge disposal operations in coastal waters. Contact Author.
NASA Astrophysics Data System (ADS)
Amiri Delouei, A.; Nazari, M.; Kayhani, M. H.; Kang, S. K.; Succi, S.
2016-04-01
In the current study, a direct-forcing immersed boundary-non-Newtonian lattice Boltzmann method (IB-NLBM) is developed to investigate the sedimentation and interaction of particles in shear-thinning and shear-thickening fluids. In the proposed IB-NLBM, the non-linear mechanics of non-Newtonian particulate flows is detected by combination of the most desirable features of immersed boundary and lattice Boltzmann methods. The noticeable roles of non-Newtonian behavior on particle motion, settling velocity and generalized Reynolds number are investigated by simulating benchmark problem of one-particle sedimentation under the same generalized Archimedes number. The effects of extra force due to added accelerated mass are analyzed on the particle motion which have a significant impact on shear-thinning fluids. For the first time, the phenomena of interaction among the particles, such as Drafting, Kissing, and Tumbling in non-Newtonian fluids are investigated by simulation of two-particle sedimentation and twelve-particle sedimentation. The results show that increasing the shear-thickening behavior of fluid leads to a significant increase in the kissing time. Moreover, the transverse position of particles for shear-thinning fluids during the tumbling interval is different from Newtonian and the shear-thickening fluids. The present non-Newtonian particulate study can be applied in several industrial and scientific applications, like the non-Newtonian sedimentation behavior of particles in food industrial and biological fluids.
Helton, Kristen L; Yager, Paul
2007-11-01
As part of a project to develop an integrated microfluidic biosensor for the detection of small molecules in saliva, practical issues of extraction of analytes from non-Newtonian samples using an H-filter were explored. The H-filter can be used to rapidly and efficiently extract small molecules from a complex sample into a simpler buffer. The location of the interface between the sample and buffer streams is a critical parameter in the function of the H-filter, so fluorescence microscopy was employed to monitor the interface position; this revealed apparently anomalous fluorophore diffusion from the samples into the buffer solutions. Using confocal microscopy to understand the three-dimensional distribution of the fluorophore, it was found that the interface between the non-Newtonian sample and Newtonian buffer was both curved and unstable. The core of the non-Newtonian sample extended into the Newtonian buffer and its position was unstable, producing a fluorescence intensity profile that gave rise to the apparently anomalously fast fluorophore transport. These instabilities resulted from the pairing of rheologically dissimilar fluid streams and were flowrate dependent. We conclude that use of non-Newtonian fluids, such as saliva, in the H-filter necessitates pretreatment to reduce viscoelasticity. The interfacial variation in position, stability and shape caused by the non-Newtonian samples has substantial implications for the use of biological samples for quantitative analysis and analyte extraction in concurrent flow extraction devices.
Non-Newtonian rheology of bubble-bearing magmas: effects on conduit dynamics.
NASA Astrophysics Data System (ADS)
Colucci, Simone; Papale, Paolo; Montagna, Chiara
2015-04-01
Non-Newtonian rheology typically arises in magmas from the presence of a dispersed phase. In particular bubbles can reduce or increase the relative viscosity, depending on size and strain regime (i.e., capillary number), for example large bubbles, as well as low strain, reduce the apparent viscosity. In a Non-Newtonian regime it is not possible to define a strain-rate-independent viscosity and the velocity profile is complex. In this work we extended the 1D, steady, isothermal, multiphase non-homogeneous magma ascent model of Papale (2001) to 1.5D to include the Non-Newtonian effect of a bubble-bearing magma. The model has been tested with a basaltic test case. In this way we were able to calculate depth-dependent Non-newtonian velocity profiles across the conduit radius along with shear strain-rate and viscosity distributions. Moreover, the model could quantify the effects of the Non-Newtonian rheology on conduit flow dynamics, in terms of flow variables (e.g. velocity, pressure). P. Papale (2001). Dynamics of magma flow in volcanic conduits with variable fragmentation efficiency and nonequilibrium pumice degassing. JGR, 106, 11043-11065.
Diagnosis at a glance of biological non-Newtonian fluids with Film Interference Flow Imaging (FIFI)
NASA Astrophysics Data System (ADS)
Hidema, R.; Yamada, N.; Furukawa, H.
2012-04-01
In the human body, full of biological non-Newtonian fluids exist. For example, synovial fluids exist in our joints, which contain full of biopolymers, such as hyaluronan and mucin. It is thought that these polymers play critical roles on the smooth motion of the joint. Indeed, luck of biopolymers in synovial fluid cause joint pain. Here we study the effects of polymer in thin liquid layer by using an original experimental method called Film Interference Flow Imaging (FIFI). A vertically flowing soap film containing polymers is made as two-dimensional flow to observe turbulence. The thickness of water layer is about 4 μm sandwiched between surfactant mono-layers. The interference pattern of the soap film is linearly related to the flow velocity in the water layer through the change in the thickness of the film. Thus the flow velocity is possibly analyzed by the single image analysis of the interference pattern, that is, FIFI. The grid turbulence was made in the flowing soap films containing the long flexible polymer polyethyleneoxide (PEO, Mw=3.5x106), and rigid polymer hydroxypropyl cellulose (HPC, Mw > 1.0 x106). The decaying process of the turbulence is affected by PEO and HPC at several concentrations. The effects of PEO are sharply seen even at low concentrations, while the effects of HPC are gradually occurred at much higher concentration compared to the PEO. It is assumed that such a difference between PEO and HPC is due to the polymer stretching or polymer orientation under turbulence, which is observed and analyzed by FIFI. We believe the FIFI will be applied in the future to examine biological fluids such as synovial fluids quickly and quantitatively.
Mounding of a non-Newtonian jet impinging on a solid substrate.
Schunk, Peter Randall; Grillet, Anne Mary; Roberts, Scott A.; Baer, Thomas A.; Rao, Rekha Ranjana
2010-06-01
When a fluid jet impinges on a solid substrate, a variety of behaviors may occur around the impact region. One example is mounding, where the fluid enters the impact region faster than it can flow away, forming a mound of fluid above the main surface. For some operating conditions, this mound can destabilize and buckle, entraining air in the mound. Other behaviors include submerging flow, where the jet impinges into an otherwise steady pool of liquid, entraining a thin air layer as it enters the pool. This impact region is one of very high shear rates and as such, complex fluids behave very differently than do Newtonian fluids. In this work, we attempt to characterize this range of behavior for Newtonian and non-Newtonian fluids using dimensionless parameters. We model the fluid as a modified Bingham-Carreau-Yasuda fluid, which exhibits the full range of pseudoplastic flow properties throughout the impact region. Additionally, we study viscoelastic effects through the use of the Giesekus model. Both 2-D and 3-D numerical simulations are performed using a variety of finite element method techniques for tracking the jet interface, including Arbitrary Lagrangian Eulerian (ALE), diffuse level sets, and a conformal decomposition finite element method (CDFEM). The presence of shear-thinning characteristics drastically reduces unstable mounding behavior, yet can lead to air entrainment through the submerging flow regime. We construct an operating map to understand for what flow parameters mounding and submerging flows will occur, and how the fluid rheology affects these behaviors. This study has many implications in high-speed industrial bottle filling applications.
The stretching of an electrified non-Newtonian jet: A model for electrospinning
NASA Astrophysics Data System (ADS)
Feng, J. J.
2002-11-01
Electrospinning uses an external electrostatic field to accelerate and stretch a charged polymer jet, and may produce ultrafine "nanofibers." Many polymers have been successfully electrospun in the laboratory. Recently Hohman [et al.] [Phys. Fluids, 13, 2201 (2001)] proposed an electrohydrodynamic model for electrospinning Newtonian jets. A problem arises, however, with the boundary condition at the nozzle. Unless the initial surface charge density is zero or very small, the jet bulges out upon exiting the nozzle in a "ballooning instability," which never occurs in reality. In this paper, we will first describe a slightly different Newtonian model that avoids the instability. Well-behaved solutions are produced that are insensitive to the initial charge density, except inside a tiny "boundary layer" at the nozzle. Then a non-Newtonian viscosity function is introduced into the model and the effects of extension thinning and thickening are explored. Results show two distinct regimes of stretching. For a "mildly stretched" jet, the axial tensile force in the fiber resists stretching, so that extension thinning promotes stretching and thickening hinders stretching. For a "severely stretched" jet, on the other hand, the tensile force enhances stretching at the beginning of the jet and suppresses it farther downstream. The effects of extensional viscosity then depend on the competition between the upstream and downstream dynamics. Finally, we use an empirical correlation to simulate strain hardening typical of polymeric liquids. This generally steepens the axial gradient of the tensile stress. Stretching is more pronounced at the beginning but weakens later, and ultimately thicker fibers are produced because of strain hardening.
NASA Astrophysics Data System (ADS)
Cruciani, Francesco; Barchi, Massimiliano R.
2016-03-01
In recent decades, advances in seismic processing and acquisition of new data sets have revealed the presence of many deepwater fold-and-thrust belts (DW-FTBs), often developing along continental passive margins. These kinds of tectonic features have been intensively studied, due to their substantial interest. This work presents a regional-scale study of the poorly explored Lamu Basin DW-FTB, a margin-scale, gravity-driven system extending for more than 450 km along the continental passive margin of Kenya and southern Somalia (East Africa). A 2-D seismic data set was analyzed, consisting of both recently acquired high-quality data and old reprocessed seismic profiles, for the first detailed structural and stratigraphic interpretation of this DW-FTB. The system originated over an Early to mid-Cretaceous shale detachment due to a mainly gravity-spreading mechanism. Analysis of synkinematic strata indicates that the DW-FTB was active from the Late Cretaceous to the Early Miocene, but almost all of the deformation occurred before the Late Paleocene. The fold-and-thrust system displays a marked N-S variation in width, the northern portion being more than 150 km wide and the southern portion only a few dozen kilometers wide; this along-strike variation is thought to be related to the complex tectonosedimentary evolution of the continental margin at the Somalia-Kenya boundary, also reflected in the present-day bathymetry. Locally, a series of volcanic edifices stopped the basinward propagation of the DW-FTB. A landward change in the dominant structural style, from asymmetric imbricate thrust sheets to pseudo-symmetric detachment folds, is generally observed, related to the landward thickening of the detached shales.
Numerical Modeling of Mixing of Chemically Reacting, Non-Newtonian Slurry for Tank Waste Retrieval
Yuen, D.A.; Onishi, Y.
2001-09-30
In the U.S. Department of Energy (DOE) complex, 100 million gallons of radioactive and chemical wastes from plutonium production are stored in 281 underground storage tanks. Retrieval of the wastes from the tanks is the first step in its ultimate treatment and disposal. Because billions of dollars are being spent on this effort, waste retrieval demands a strong scientific basis for its successful completion. As will be discussed in Section 4.2, complex interactions among waste chemical reactions, rheology, and mixing of solid and liquid tank waste (and possibly with a solvent) will occur in DSTs during the waste retrieval (mixer pump) operations. The ultimate goal of this study was to develop the ability to simulate the complex chemical and rheological changes that occur in the waste during processing for retrieval. This capability would serve as a scientific assessment tool allowing a priori evaluation of the consequences of proposed waste retrieval operations. Hanford tan k waste is a multiphase, multicomponent, high-ionic strength, and highly basic mixture of liquids and solids. Wastes stored in the 4,000-m3 DSTs will be mixed by 300-hp mixer pumps that inject high-speed (18.3 m/s) jets to stir up the sludge and supernatant liquid for retrieval. During waste retrieval operations, complex interactions occur among waste mixing, chemical reactions, and associated rheology. Thus, to determine safe and cost-effective operational parameters for waste retrieval, decisions must rely on new scientific knowledge to account for physical mixing of multiphase flows, chemical reactions, and waste rheology. To satisfy this need, we integrated a computational fluid dynamics code with state-of-the-art equilibrium and kinetic chemical models and non-Newtonian rheology (Onishi et al. 1999). This development is unique and holds great promise for addressing the complex phenomena of tank waste retrieval. The current model is, however, applicable only to idealized tank waste
Determination of the Köthe-Toeplitz Duals over the Non-Newtonian Complex Field
Kadak, Uğur
2014-01-01
The important point to note is that the non-Newtonian calculus is a self-contained system independent of any other system of calculus. Therefore the reader may be surprised to learn that there is a uniform relationship between the corresponding operators of this calculus and the classical calculus. Several basic concepts based on non-Newtonian calculus are presented by Grossman (1983), Grossman and Katz (1978), and Grossman (1979). Following Grossman and Katz, in the present paper, we introduce the sets of bounded, convergent, null series and p-bounded variation of sequences over the complex field C* and prove that these are complete. We propose a quite concrete approach based on the notion of Köthe-Toeplitz duals with respect to the non-Newtonian calculus. Finally, we derive some inclusion relationships between Köthe space and solidness. PMID:25028678
Determination of the Köthe-Toeplitz duals over the non-Newtonian complex field.
Kadak, Uğur
2014-01-01
The important point to note is that the non-Newtonian calculus is a self-contained system independent of any other system of calculus. Therefore the reader may be surprised to learn that there is a uniform relationship between the corresponding operators of this calculus and the classical calculus. Several basic concepts based on non-Newtonian calculus are presented by Grossman (1983), Grossman and Katz (1978), and Grossman (1979). Following Grossman and Katz, in the present paper, we introduce the sets of bounded, convergent, null series and p-bounded variation of sequences over the complex field C* and prove that these are complete. We propose a quite concrete approach based on the notion of Köthe-Toeplitz duals with respect to the non-Newtonian calculus. Finally, we derive some inclusion relationships between Köthe space and solidness.
Non-Newtonian bile flow in elastic cystic duct: one- and three-dimensional modeling.
Li, W G; Luo, X Y; Chin, S B; Hill, N A; Johnson, A G; Bird, N C
2008-11-01
Bile flow is thought to play an essential role in the pathophysiological genesis of cholelithiasis (gallstone formation) and in gallbladder pain. In this paper, we extend our previous study of the human biliary system (Li et al., 2007, J. Biomech. Eng., 129:164-173) to include two important factors: the non-Newtonian properties of bile, and elastic deformation of the cystic duct. A one-dimensional (1D) model is analyzed and compared with three-dimensional (3D) fluid-structure interaction simulations. It is found that non-Newtonian bile raises resistance to the flow of bile, which can be augmented significantly by the elastic deformation (collapse) of the cystic duct. We also show that the 1D model predicts the pressure drop of the cystic duct flow well for all cases considered (Newtonian or non-Newtonian flow, rigid or elastic ducts), when compared with the full 3D simulations.
Numerical Simulation of non-Newtonian Fluid Flows through Fracture Network
NASA Astrophysics Data System (ADS)
Dharmawan, I. A.; Ulhag, R. Z.; Endyana, C.; Aufaristama, M.
2016-01-01
We present a numerical simulation of non-Newtonian fluid flow in a twodimensional fracture network. The fracture is having constant mean aperture and bounded with Hurst exponent surfaces. The non-Newtonian rheology behaviour of the fluid is described using the Power-Law model. The lattice Boltzmann method is employed to calculate the solutions for non-Newtonian flow in finite Reynolds number. We use a constant force to drive the fluid within the fracture, while the bounceback rules and periodic boundary conditions are applied for the fluid-solid interaction and inflow outlflow boundary conditions, respectively. The validation study of the simulation is done via parallel plate flow simulation and the results demonstrated good agreement with the analytical solution. In addition, the fluid flow properties within the fracture network follow the relationships of power law fluid while the errors are becoming larger if the fluid more shear thinning.
NASA Astrophysics Data System (ADS)
Tkachenko, E. M.; Zaitsev, D. V.; Orlik, E. V.; Kabov, O. A.
2016-10-01
Thin and ultra thin liquid films driven by a forced gas/vapor flow (stratified or annular flows), i.e. shear-driven liquid films in a narrow channel, is one of the promising candidate for the thermal management of advanced semiconductor devices with high local heat release. In experiments performed in this paper with locally heated shear-driven liquid films of water the effect of various conditions, such as flow rates of liquid and gas and channel height, on critical heat flux (CHF) was investigated. In experiments the record value of CHF as high as 540 W/cm2 has been achieved. The heat spreading into the substrate and the heat loses into the atmosphere in total don't exceed 30% at heat fluxes higher than 200 W/cm2. Comparison of shear-driven liquid films and gravity-driven liquid films showed that CHF in shear-driven films up to 10 times higher than in gravity-driven liquid films. Thus, prospect of using shear- driven films of water in modern cooling systems of semiconductor devices was confirmed.
Sinking of spherical slablets through a non-Newtonian mantle
NASA Astrophysics Data System (ADS)
Crameri, Fabio; Stegman, Dave; Petersen, Robert; Tackley, Paul
2014-05-01
The dominant driving force for plate tectonics is slab pull, in which sinking slabs pull the trailing plate. Forward plate velocities are typically similar in magnitude (7 cm/yr) as estimates for sinking velocities of slabs through the upper mantle. However, these estimates are based on data for slabs that are coherent into the transition zone as well as models that considered the upper mantle to be entirely Newtonian. Dislocation creep in the upper mantle can strongly influence mantle flow, and is likely activated for flow around vertically sinking slabs in the uppermost mantle. Thus, it is possible that in some scenarios, a non-Newtonian mantle will have an influence on plate motions but it is unclear to what degree. To address this question, we investigate how the non-Newtonian rheology modifies the sinking velocities of slablets (spherical, negatively buoyant and highly viscous blobs). The model set-up is similar to a Stokes sphere sinking, but is in 2-D cartesian with temperature-and stress-dependent rheology. For these numerical models, we use the Stag-YY code (e.g., Tackley 2008) and apply a pseudo-free surface using the 'sticky-air' approach (Matsumoto and Tomoda 1983; Schmeling et al, 2008, Crameri et al., 2012). The sinking blob is both highly viscous and compositionally dense, but is the same temperature as the background fluid which eliminates thermal diffusion and associated variations in thermal buoyancy. The model domain is 2x1 or 4x1 and allows enough distance to the sidewalls so that sinking velocities are not influenced by the boundary conditions. We compare our results with those previously obtained for salt diapirs rising through a power-law rheology mantle/crust (Weinberg, 1993; Weinberg and Podladchikov, 1994), which provided both numerical and analytic results. Previous results indicate a speed-up of an order of magnitude is possible. Finally, we then extend the models and analysis to mantle convection systems that include for single
MASS TRANSFER COEFFICIENTS FOR A NON-NEWTONIAN FLUID AND WATER WITH AND WITHOUT ANTI-FOAM AGENTS
Leishear, R.
2009-09-09
Mass transfer rates were measured in a large scale system, which consisted of an 8.4 meter tall by 0.76 meter diameter column containing one of three fluids: water with an anti-foam agent, water without an anti-foam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated, and due to flammability concerns oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from solution as air bubbled up, or sparged, through the solution from the bottom of the column. Air sparging was supplied by a single tube which was co-axial to the column, the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2, 5, and 10 mm/second were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels.
Quantum signatures of non-Newtonian orbits in the asymmetric infinite square well.
Timberlake, Todd K; Nelson, Molly M
2009-03-01
An infinite square well with a rectangular step is one of the simplest systems to exhibit non-Newtonian ray-splitting periodic orbits in the classical limit. We examine eigenvalue spacings in the quantum version of this system. The sequence of spacings shows deviations from uniformity at energies just above the step height and distinct resonance features are visible at certain energies. Semiclassical analysis shows that these features are directly related to the presence of non-Newtonian orbits in the classical system. In addition, the resonance features are shown to produce revivals in suitably constructed wave packets peaked at the resonance energy.
Stretch flow of confined non-Newtonian fluids: nonlinear fingering dynamics.
Brandão, Rodolfo; Fontana, João V; Miranda, José A
2013-12-01
We employ a weakly nonlinear perturbative scheme to investigate the stretch flow of a non-Newtonian fluid confined in Hele-Shaw cell for which the upper plate is lifted. A generalized Darcy's law is utilized to model interfacial fingering formation in both the weak shear-thinning and weak shear-thickening limits. Within this context, we analyze how the interfacial finger shapes and the nonlinear competition dynamics among fingers are affected by the non-Newtonian nature of the stretched fluid.
Numerical study of purely viscous non-Newtonian flow in an abdominal aortic aneurysm.
Marrero, Victor L; Tichy, John A; Sahni, Onkar; Jansen, Kenneth E
2014-10-01
It is well known that blood has non-Newtonian properties, but it is generally accepted that blood behaves as a Newtonian fluid at shear rates above 100 s-1. However, in transient conditions, there are times and locations where the shear rate is well below 100 s-1, and it is reasonable to infer that non-Newtonian effects could become important. In this study, purely viscous non-Newtonian (generalized Newtonian) properties of blood are incorporated into the simulation-based framework for cardiovascular surgery planning developed by Taylor et al. (1999, "Predictive Medicine: Computational Techniques in Therapeutic Decision Making," Comput. Aided Surg., 4, pp. 231-247; 1998, "Finite Element Modeling of Blood Flow in Arteries," Comput. Methods Appl. Mech. Eng., 158, pp. 155-196). Equations describing blood flow are solved in a patient-based abdominal aortic aneurysm model under steady and physiological flow conditions. Direct numerical simulation (DNS) is used, and the complex flow is found to be constantly transitioning between laminar and turbulent in both the spatial and temporal sense. It is found for the case simulated that using the non-Newtonian viscosity modifies the solution in subtle ways that yield a mesh-independent solution with fewer degrees of freedom than the Newtonian counterpart. It appears that in regions of separated flow, the lower shear rate produces higher viscosity with the non-Newtonian model, which reduces the associated resolution needs. When considering the real case of pulsatile flow, high shear layers lead to greater unsteadiness in the Newtonian case relative to the non-Newtonian case. This, in turn, results in a tendency for the non-Newtonian model to need fewer computational resources even though it has to perform additional calculations for the viscosity. It is also shown that both viscosity models predict comparable wall shear stress distribution. This work suggests that the use of a non-Newtonian viscosity models may be attractive
Gravity driven instability in elastic solid layers.
Mora, Serge; Phou, Ty; Fromental, Jean-Marc; Pomeau, Yves
2014-10-24
We demonstrate the instability of the free surface of a soft elastic solid facing downwards. Experiments are carried out using a gel of constant density ρ, shear modulus μ, put in a rigid cylindrical dish of depth h. When turned upside down, the free surface of the gel undergoes a normal outgoing acceleration g. It remains perfectly flat for ρgh/μ<α* with α*≃6, whereas a steady pattern spontaneously appears in the opposite case. This phenomenon results from the interplay between the gravitational energy and the elastic energy of deformation, which reduces the Rayleigh waves celerity and vanishes it at the threshold.
Gravity-driven dense granular flows
ERTAS,DENIZ; GREST,GARY S.; HALSEY,THOMAS C.; DEVINE,DOV; SILBERT,LEONARDO E.
2000-03-29
The authors report and analyze the results of numerical studies of dense granular flows in two and three dimensions, using both linear damped springs and Hertzian force laws between particles. Chute flow generically produces a constant density profile that satisfies scaling relations suggestive of a Bagnold grain inertia regime. The type for force law has little impact on the behavior of the system. Failure is not initiated at the surface, consistent with the absence of surface flows and different principal stress directions at vs. below the surface.
The mechanics of gravity-driven faulting
NASA Astrophysics Data System (ADS)
Barrows, L.; Barrows, V.
2010-04-01
Faulting can result from either of two different mechanisms. These involve fundamentally different energetics. In elastic rebound, locked-in elastic strain energy is transformed into the earthquake (seismic waves plus work done in the fault zone). In force-driven faulting, the forces that create the stress on the fault supply work or energy to the faulting process. Half of this energy is transformed into the earthquake and half goes into an increase in locked-in elastic strain. In elastic rebound the locked-in elastic strain drives slip on the fault. In force-driven faulting it stops slip on the fault. Tectonic stress is reasonably attributed to gravity acting on topography and the Earth's lateral density variations. This includes the thermal convection that ultimately drives plate tectonics. Mechanical analysis has shown the intensity of the gravitational tectonic stress that is associated with the regional topography and lateral density variations that actually exist is comparable with the stress drops that are commonly associated with tectonic earthquakes; both are in the range of tens of bar to several hundred bar. The gravity collapse seismic mechanism assumes the fault fails and slips in direct response to the gravitational tectonic stress. Gravity collapse is an example of force-driven faulting. In the simplest case, energy that is released from the gravitational potential of the stress-causing topography and lateral density variations is equally split between the earthquake and the increase in locked-in elastic strain. The release of gravitational potential energy requires a change in the Earth's density distribution. Gravitational body forces are solely dependent on density so a change in the density distribution requires a change in the body forces. This implies the existence of volumetric body-force displacements. The volumetric body-force displacements are in addition to displacements generated by slip on the fault. They must exist if gravity participates in the energetics of the faulting process. From the perspective of gravitational tectonics, the gravity collapse mechanism is direct and simple. The related mechanics are more subtle. If gravity is not deliberately and explicitly included in an earthquake model, then gravity is locked out of the energetics of the model. The earthquake model (but not necessarily the physical reality) is then elastic rebound.
The Energetics of Gravity Driven Faulting
NASA Astrophysics Data System (ADS)
Barrows, L.
2007-12-01
Faulting can result from either of two different mechanisms. These involve fundamentally different energetics. In displacement-bounded faulting, locked-in elastic strain energy is transformed into seismic waves plus work done in the fault zone. Elastic rebound is an example of displacement-bounded faulting. In force-driven faulting, the forces that create the stress on the fault supply work or energy to the faulting process. Half of this energy is transformed into seismic waves plus work done in the fault zone and half goes into an increase in locked-in elastic strain. In displacement-bounded faulting the locked-in elastic strain drives slip on the fault. In force-driven faulting it stops slip on the fault. Tectonic stress is reasonably attributed to gravity acting on topography and the Earth's lateral density variations. This includes the thermal convection that ultimately drives plate tectonics. The gravity collapse seismic mechanism assumes the fault fails and slips in direct response to the gravitational tectonic stress. Gravity collapse is an example of force-driven faulting. In the simplest case, energy that is released from the gravitational potential of the topography and internal stress-causing density variations is equally split between the seismic waves plus work done in the fault zone and the increase in locked-in elastic strain. The release of gravitational potential energy requires a change in the Earth's density distribution. Gravitational body forces are solely dependent on density so a change in the density distribution requires a change in the body forces. This implies the existence of volumetric body-force displacements. The volumetric body-force displacements are in addition to displacements generated by slip on the fault. They must exist if gravity participates in the energetics of the faulting process. From the perspective of gravitational tectonics, the gravity collapse mechanism is direct and simple. The related mechanics are a little more subtle. If gravity is not deliberately and explicitly included in an earthquake model, then gravity is locked out of the energetics of the model. The earthquake model (but not necessarily the physical reality) is then elastic rebound.
A Colorful Mixing Experiment in a Stirred Tank Using Non-Newtonian Blue Maize Flour Suspensions
ERIC Educational Resources Information Center
Trujilo-de Santiago, Grissel; Rojas-de Gante, Cecillia; García-Lara, Silverio; Ballesca´-Estrada, Adriana; Alvarez, Marion Moise´s
2014-01-01
A simple experiment designed to study mixing of a material of complex rheology in a stirred tank is described. Non-Newtonian suspensions of blue maize flour that naturally contain anthocyanins have been chosen as a model fluid. These anthocyanins act as a native, wide spectrum pH indicator exhibiting greenish colors in alkaline environments, blue…
On line and double integrals in the non-Newtonian sense
NASA Astrophysics Data System (ADS)
ćakmak, Ahmet Faruk; Başar, Feyzi
2014-08-01
This paper is devoted to line and double integrals in the sense of non-Newtonian calculus (*-calculus). Moreover, in the sense of *-calculus, the fundamental theorem of calculus for line integrals and double integrals are stated and proved, and some applications are presented.
ERIC Educational Resources Information Center
Binous, Housam
2007-01-01
We study four non-Newtonian fluid mechanics problems using Mathematica[R]. Constitutive equations describing the behavior of power-law, Bingham and Carreau models are recalled. The velocity profile is obtained for the horizontal flow of power-law fluids in pipes and annuli. For the vertical laminar film flow of a Bingham fluid we determine the…
Learning about Non-Newtonian Fluids in a Student-Driven Classroom
ERIC Educational Resources Information Center
Dounas-Frazer, D. R.; Lynn, J.; Zaniewski, A. M.; Roth, N.
2013-01-01
We describe a simple, low-cost experiment and corresponding pedagogical strategies for studying fluids whose viscosities depend on shear rate, referred to as "non-Newtonian fluids." We developed these materials teaching for the Compass Project, an organization that fosters a creative, diverse, and collaborative community of science…
Revisiting Newtonian and Non-Newtonian Fluid Mechanics Using Computer Algebra
ERIC Educational Resources Information Center
Knight, D. G.
2006-01-01
This article illustrates how a computer algebra system, such as Maple[R], can assist in the study of theoretical fluid mechanics, for both Newtonian and non-Newtonian fluids. The continuity equation, the stress equations of motion, the Navier-Stokes equations, and various constitutive equations are treated, using a full, but straightforward,…
Learning about Non-Newtonian Fluids in a Student-Driven Classroom
ERIC Educational Resources Information Center
Dounas-Frazer, D. R.; Lynn, J.; Zaniewski, A. M.; Roth, N.
2013-01-01
We describe a simple, low-cost experiment and corresponding pedagogical strategies for studying fluids whose viscosities depend on shear rate, referred to as "non-Newtonian fluids." We developed these materials teaching for the Compass Project, an organization that fosters a creative, diverse, and collaborative community of science…
NASA Astrophysics Data System (ADS)
De Rosis, Alessandro
2014-11-01
In this paper, the fluid dynamics induced by a rigid lamina undergoing harmonic oscillations in a non-Newtonian calm fluid is investigated. The fluid is modelled through the lattice Boltzmann method and the flow is assumed to be nearly incompressible. An iterative viscosity-correction based procedure is proposed to properly account for the non-Newtonian fluid feature and its accuracy is evaluated. In order to handle the mutual interaction between the lamina and the encompassing fluid, the Immersed Boundary method is adopted. A numerical campaign is performed. In particular, the effect of the non-Newtonian feature is highlighted by investigating the fluid forces acting on a harmonically oscillating lamina for different values of the Reynolds number. The findings prove that the non-Newtonian feature can drastically influence the behaviour of the fluid and, as a consequence, the forces acting upon the lamina. Several considerations are carried out on the time history of the drag coefficient and the results are used to compute the added mass through the hydrodynamic function. Moreover, the computational cost involved in the numerical simulations is discussed. Finally, two applications concerning water resources are investigated: the flow through an obstructed channel and the particle sedimentation. Present findings highlight a strong coupling between the body shape, the Reynolds number, and the flow behaviour index.
A Colorful Mixing Experiment in a Stirred Tank Using Non-Newtonian Blue Maize Flour Suspensions
ERIC Educational Resources Information Center
Trujilo-de Santiago, Grissel; Rojas-de Gante, Cecillia; García-Lara, Silverio; Ballesca´-Estrada, Adriana; Alvarez, Marion Moise´s
2014-01-01
A simple experiment designed to study mixing of a material of complex rheology in a stirred tank is described. Non-Newtonian suspensions of blue maize flour that naturally contain anthocyanins have been chosen as a model fluid. These anthocyanins act as a native, wide spectrum pH indicator exhibiting greenish colors in alkaline environments, blue…
Revisiting Newtonian and Non-Newtonian Fluid Mechanics Using Computer Algebra
ERIC Educational Resources Information Center
Knight, D. G.
2006-01-01
This article illustrates how a computer algebra system, such as Maple[R], can assist in the study of theoretical fluid mechanics, for both Newtonian and non-Newtonian fluids. The continuity equation, the stress equations of motion, the Navier-Stokes equations, and various constitutive equations are treated, using a full, but straightforward,…
ERIC Educational Resources Information Center
Binous, Housam
2007-01-01
We study four non-Newtonian fluid mechanics problems using Mathematica[R]. Constitutive equations describing the behavior of power-law, Bingham and Carreau models are recalled. The velocity profile is obtained for the horizontal flow of power-law fluids in pipes and annuli. For the vertical laminar film flow of a Bingham fluid we determine the…
Ultrasonic atomization: effect of liquid phase properties.
Avvaru, Balasubrahmanyam; Patil, Mohan N; Gogate, Parag R; Pandit, Aniruddha B
2006-02-01
Experiments have been conducted to understand the mechanism by which the ultrasonic vibration at the gas liquid interface causes the atomization of liquid. For this purpose, aqueous solutions having different viscosities and liquids showing Newtonian (aqueous solution of glycerin) and non-Newtonian behavior (aqueous solution of sodium salt of carboxy methyl cellulose) were employed. It has been found that the average droplet size produced by the pseudo-plastic liquid is less than that produced by the viscous Newtonian liquid having viscosity equal to zero-shear rate viscosity of the shear thinning liquid. The droplet size was found to increase initially with an increase in the viscosity up to a certain threshold viscosity after which the droplet size was found to decrease again. Also droplet size distribution is found to be more compact (uniform sizes) with an increasing viscosity of the atomizing liquid. The presence of the cavitation and its effect on the atomization has been semi quantitatively confirmed using energy balance and by the measurement of the droplet ejection velocities and validated on the basis of the decomposition of the aqueous KI solution. A correlation has been proposed for the prediction of droplet size for aqueous Newtonian fluids and fluids showing non-Newtonian behavior based on the dimensionless numbers incorporating the operating parameters of the ultrasonic atomizer and the liquid phase physico-chemical properties.
Studying Mixing in Non-Newtonian Blue Maize Flour Suspensions Using Color Analysis
Trujillo-de Santiago, Grissel; Rojas-de Gante, Cecilia; García-Lara, Silverio; Ballescá-Estrada, Adriana; Alvarez, Mario Moisés
2014-01-01
Background Non-Newtonian fluids occur in many relevant flow and mixing scenarios at the lab and industrial scale. The addition of acid or basic solutions to a non-Newtonian fluid is not an infrequent operation, particularly in Biotechnology applications where the pH of Non-Newtonian culture broths is usually regulated using this strategy. Methodology and Findings We conducted mixing experiments in agitated vessels using Non-Newtonian blue maize flour suspensions. Acid or basic pulses were injected to reveal mixing patterns and flow structures and to follow their time evolution. No foreign pH indicator was used as blue maize flours naturally contain anthocyanins that act as a native, wide spectrum, pH indicator. We describe a novel method to quantitate mixedness and mixing evolution through Dynamic Color Analysis (DCA) in this system. Color readings corresponding to different times and locations within the mixing vessel were taken with a digital camera (or a colorimeter) and translated to the CIELab scale of colors. We use distances in the Lab space, a 3D color space, between a particular mixing state and the final mixing point to characterize segregation/mixing in the system. Conclusion and Relevance Blue maize suspensions represent an adequate and flexible model to study mixing (and fluid mechanics in general) in Non-Newtonian suspensions using acid/base tracer injections. Simple strategies based on the evaluation of color distances in the CIELab space (or other scales such as HSB) can be adapted to characterize mixedness and mixing evolution in experiments using blue maize suspensions. PMID:25401332
Studying mixing in Non-Newtonian blue maize flour suspensions using color analysis.
Trujillo-de Santiago, Grissel; Rojas-de Gante, Cecilia; García-Lara, Silverio; Ballescá-Estrada, Adriana; Alvarez, Mario Moisés
2014-01-01
Non-Newtonian fluids occur in many relevant flow and mixing scenarios at the lab and industrial scale. The addition of acid or basic solutions to a non-Newtonian fluid is not an infrequent operation, particularly in Biotechnology applications where the pH of Non-Newtonian culture broths is usually regulated using this strategy. We conducted mixing experiments in agitated vessels using Non-Newtonian blue maize flour suspensions. Acid or basic pulses were injected to reveal mixing patterns and flow structures and to follow their time evolution. No foreign pH indicator was used as blue maize flours naturally contain anthocyanins that act as a native, wide spectrum, pH indicator. We describe a novel method to quantitate mixedness and mixing evolution through Dynamic Color Analysis (DCA) in this system. Color readings corresponding to different times and locations within the mixing vessel were taken with a digital camera (or a colorimeter) and translated to the CIELab scale of colors. We use distances in the Lab space, a 3D color space, between a particular mixing state and the final mixing point to characterize segregation/mixing in the system. Blue maize suspensions represent an adequate and flexible model to study mixing (and fluid mechanics in general) in Non-Newtonian suspensions using acid/base tracer injections. Simple strategies based on the evaluation of color distances in the CIELab space (or other scales such as HSB) can be adapted to characterize mixedness and mixing evolution in experiments using blue maize suspensions.
Non-Newtonian Rheology of Calc-Alkaline Obsidian at High Stresses and Strain Rates
NASA Astrophysics Data System (ADS)
Dingwell, D. B.; Hess, K.; Lavallee, Y.; Cordonnier, B.; Mueller, S.
2005-12-01
The importance of the Non-Newtonian regime at high stress and strain rates has been reported for a variety of silicate melts subject to different tests but never for natural samples bearing their original contents of magmatic water and microlite content. Here, we used a unique high-load (<500 MPa), high-temperature (<1300°C) deformation apparatus for studying in situ the Non-Newtonian flow behaviour of magmas. A series of experiments were performed on calc-alkaline obsidian lavas from Lipari (Italy), Iceland, and Cougar Creek Dome, Yellowstone (USA), and compared to depolymerized melt (NIST 710). The samples were heated to relevant magmatic effusive temperatures that yielded similar relaxation timescales and were deformed under constant stress in the range of 100 to 200 MPa. The onset of the Non-Newtonian flow regime, registered by a decreasing viscosity with time (at fixed strain rate), occurred at 120 MPa for the depolymerized melt. The Non-Newtonian flow behavior was observed up to pressures as high as approx. 180 MPa, where the samples fragmented readily (hot cracking). In contrast, all three calc-alkaline rhyolitic melt remained in a Newtonian regime up to approx. 160 MPa. The window of Non-Newtonian behavior was, however, very narrow and most samples fragmented instantaneously in the attempt of pursuing the deformation. If this is not an experimental artefact, we conclude that modeling of the flow behaviour of a ascending crystal- and bubble-free calc-alkaline rhyolitic dome magma can be performed using a simple Newtonian fluid approximation. Thus the Non-Arrhenian model of Hess and Dingwell (1996) for the compositional and temperature dependence of viscosity could be applied.
Extension of Murray's law using a non-Newtonian model of blood flow
Revellin, Rémi; Rousset, François; Baud, David; Bonjour, Jocelyn
2009-01-01
Background So far, none of the existing methods on Murray's law deal with the non-Newtonian behavior of blood flow although the non-Newtonian approach for blood flow modelling looks more accurate. Modeling In the present paper, Murray's law which is applicable to an arterial bifurcation, is generalized to a non-Newtonian blood flow model (power-law model). When the vessel size reaches the capillary limitation, blood can be modeled using a non-Newtonian constitutive equation. It is assumed two different constraints in addition to the pumping power: the volume constraint or the surface constraint (related to the internal surface of the vessel). For a seek of generality, the relationships are given for an arbitrary number of daughter vessels. It is shown that for a cost function including the volume constraint, classical Murray's law remains valid (i.e. ΣRc = cste with c = 3 is verified and is independent of n, the dimensionless index in the viscosity equation; R being the radius of the vessel). On the contrary, for a cost function including the surface constraint, different values of c may be calculated depending on the value of n. Results We find that c varies for blood from 2.42 to 3 depending on the constraint and the fluid properties. For the Newtonian model, the surface constraint leads to c = 2.5. The cost function (based on the surface constraint) can be related to entropy generation, by dividing it by the temperature. Conclusion It is demonstrated that the entropy generated in all the daughter vessels is greater than the entropy generated in the parent vessel. Furthermore, it is shown that the difference of entropy generation between the parent and daughter vessels is smaller for a non-Newtonian fluid than for a Newtonian fluid. PMID:19445663
Extension of Murray's law using a non-Newtonian model of blood flow.
Revellin, Rémi; Rousset, François; Baud, David; Bonjour, Jocelyn
2009-05-15
So far, none of the existing methods on Murray's law deal with the non-Newtonian behavior of blood flow although the non-Newtonian approach for blood flow modelling looks more accurate. MODELING: In the present paper, Murray's law which is applicable to an arterial bifurcation, is generalized to a non-Newtonian blood flow model (power-law model). When the vessel size reaches the capillary limitation, blood can be modeled using a non-Newtonian constitutive equation. It is assumed two different constraints in addition to the pumping power: the volume constraint or the surface constraint (related to the internal surface of the vessel). For a seek of generality, the relationships are given for an arbitrary number of daughter vessels. It is shown that for a cost function including the volume constraint, classical Murray's law remains valid (i.e. SigmaR(c) = cste with c = 3 is verified and is independent of n, the dimensionless index in the viscosity equation; R being the radius of the vessel). On the contrary, for a cost function including the surface constraint, different values of c may be calculated depending on the value of n. We find that c varies for blood from 2.42 to 3 depending on the constraint and the fluid properties. For the Newtonian model, the surface constraint leads to c = 2.5. The cost function (based on the surface constraint) can be related to entropy generation, by dividing it by the temperature. It is demonstrated that the entropy generated in all the daughter vessels is greater than the entropy generated in the parent vessel. Furthermore, it is shown that the difference of entropy generation between the parent and daughter vessels is smaller for a non-Newtonian fluid than for a Newtonian fluid.
Castellanos, Maria Monica; Pathak, Jai A.; Leach, William; Bishop, Steven M.; Colby, Ralph H.
2014-01-01
A monoclonal antibody solution displays an increase in low shear rate viscosity upon aggregation after prolonged incubation at 40°C. The morphology and interactions leading to the formation of the aggregates responsible for this non-Newtonian character are resolved using small-angle neutron scattering. Our data show a weak repulsive barrier before proteins aggregate reversibly, unless a favorable contact with high binding energy occurs. Two types of aggregates were identified after incubation at 40°C: oligomers with radius of gyration ∼10 nm and fractal submicrometer particles formed by a slow reaction-limited aggregation process, consistent with monomers colliding many times before finding a favorable strong interaction site. Before incubation, these antibody solutions are Newtonian liquids with no increase in low shear rate viscosity and no upturn in scattering at low wavevector, whereas aggregated solutions under the same conditions have both of these features. These results demonstrate that fractal submicrometer particles are responsible for the increase in low shear rate viscosity and low wavevector upturn in scattered intensity of aggregated antibody solutions; both are removed from aggregated samples by filtering. PMID:25028888
High-gravity spreading of liquid puddles on wetting flexible substrates
NASA Astrophysics Data System (ADS)
Yang, Chen; Burrous, Adam; Xie, Jingjin; Shaikh, Hassan; Elike-Avion, Akofa; Rojas Rodriguez, Luis; Ramachandran, Adithya; Choi, Wonjae; Mazzeo, Aaron D.
2016-02-01
This letter describes a mechanical approach of using high gravity to decrease the capillary length and increase the spreading rate of liquid puddles on wetting flexible substrates. By using centrifugation and a flexible substrate floating on a high-density liquid, uniform acceleration enhances the spreading of liquid puddles. Under high gravity of 600 g, the capillary length reduces by a factor of 24.5 to ˜60 μm. The reduction in capillary length results in gravity dominating the spreading of small puddles that would otherwise have slower spreading driven by both surface tension and gravity of 1 g. The resulting measurements suggest that derived expressions in the literature for gravity-driven spreading of puddles under earth's standard gravity extend to predicting the behavior of sufficiently large puddles spreading on flexible substrates exposed to more than 100 g of acceleration. This work explores the spreading of puddles/coatings under high gravity, and the techniques described in this work will allow further interrogation of the transition between surface tension- and gravity-driven spreading.
Nesvizhevsky, V V; Protasov, K V
2005-01-01
An upper limit to non-Newtonian attractive forces is obtained from the measurement of quantum states of neutrons in the Earth's gravitational field. This limit improves the existing constraints in the nanometer range.
Edited by Guenther, Chris; Garg, Rahul
2013-08-19
The Department of Energy’s (DOE) National Energy Technology Laboratory (NETL) sponsored a workshop on non-Newtonian multiphase slurry at NETL’s Morgantown campus August 19 and 20, 2013. The objective of this special two-day meeting of 20-30 invited experts from industry, National Labs and academia was to identify and address technical issues associated with handling non-Newtonian multiphase slurries across various facilities managed by DOE. Particular emphasis during this workshop was placed on applications managed by the Office of Environmental Management (EM). The workshop was preceded by two webinars wherein personnel from ORP and NETL provided background information on the Hanford WTP project and discussed the critical design challenges facing this project. In non-Newtonian fluids, viscosity is not constant and exhibits a complex dependence on applied shear stress or deformation. Many applications under EM’s tank farm mission involve non-Newtonian slurries that are multiphase in nature; tank farm storage and handling, slurry transport, and mixing all involve multiphase flow dynamics, which require an improved understanding of the mechanisms responsible for rheological changes in non-Newtonian multiphase slurries (NNMS). To discuss the issues in predicting the behavior of NNMS, the workshop focused on two topic areas: (1) State-of-the-art in non-Newtonian Multiphase Slurry Flow, and (2) Scaling up with Confidence and Ensuring Safe and Reliable Long-Term Operation.
Soulis, Johannes V; Giannoglou, George D; Chatzizisis, Yiannis S; Seralidou, Kypriani V; Parcharidis, George E; Louridas, George E
2008-01-01
The capabilities and limitations of various molecular viscosity models, in the left coronary arterial tree, were analyzed via: molecular viscosity, local and global non-Newtonian importance factors, wall shear stress (WSS) and wall shear stress gradient (WSSG). The vessel geometry was acquired using geometrically correct 3D intravascular ultrasound (3D IVUS). Seven non-Newtonian molecular viscosity models, plus the Newtonian one, were compared. The WSS distribution yielded a consistent LCA pattern for nearly all non-Newtonian models. High molecular viscosity, low WSS and low WSSG values occurred at the outer walls of the major bifurcation in proximal LCA regions. The Newtonian blood flow was found to be a good approximation at mid- and high-strain rates. The non-Newtonian Power Law, Generalized Power Law, Carreau and Casson and Modified Cross blood viscosity models gave comparable molecular viscosity, WSS and WSSG values. The Power Law and Walburn-Schneck models over-estimated the non-Newtonian global importance factor I(G) and under-estimated the area averaged WSS and WSSG values. The non-Newtonian Power Law and the Generalized Power Law blood viscosity models were found to approximate the molecular viscosity and WSS calculations in a more satisfactory way.
NASA Astrophysics Data System (ADS)
Sojka, Paul E.; Rodrigues, Neil S.
2015-11-01
The current study investigates the drop characteristics of three Carboxymethylcellulose (CMC) sprays produced by the impingement of two liquid jets. The three water-based solutions used in this work (0.5 wt.-% CMC-7MF, 0.8 wt.-% CMC-7MF, and 1.4 wt.-% CMC-7MF) exhibited strong shear-thinning, non-Newtonian behavior - characterized by the Bird-Carreau rheological model. A generalized Bird-Carreau jet Reynolds number was used as the primary parameter to characterize the drop size and the drop velocity, which were measured using Phase Doppler Anemometry (PDA). PDA optical configuration enabled a drop size measurement range of approximately 2.3 to 116.2 μm. 50,000 drops were measured at each test condition to ensure statistical significance. The arithmetic mean diameter (D10) , Sauter mean diameter (D32) , and mass median diameter (MMD) were used as representative diameters to characterize drop size. The mean axial drop velocity Uz -mean along with its root-mean square Uz -rms were used to characterize drop velocity. Incredibly, measurements for all three CMC liquids and reference DI water sprays seemed to follow a single curve for D32 and MMD drop diameters in the high generalized Bird-Carreau jet Reynolds number range considered in this work (9.21E +03
A deformable plate interacting with a non-Newtonian fluid in three dimensions
NASA Astrophysics Data System (ADS)
Zhu, Luoding; Yu, Xijun; Liu, Nansheng; Cheng, Yongguang; Lu, Xiyun
2017-08-01
We consider a deformable plate interacting with a non-Newtonian fluid flow in three dimensions as a simple model problem for fluid-structure-interaction phenomena in life sciences (e.g., red blood cell interacting with blood flow). A power-law function is used for the constitutive equation of the non-Newtonian fluid. The lattice Boltzmann equation (the D3Q19 model) is used for modeling the fluid flow. The immersed boundary (IB) method is used for modeling the flexible plate and handling the fluid-plate interaction. The plate drag and its scaling are studied; the influences of three dimensionless parameters (power-law exponent, bending modulus, and generalized Reynolds number) are investigated.
Vortex rings in non-Newtonian viscoelastic fluids play yo-yo
NASA Astrophysics Data System (ADS)
Albagnac, Julie; Laupsien, David; Anne-Archard, Dominique
2014-11-01
Vortex rings are coherent vortical structures widely presents in geophysical flows and engineering applications. Numerous applications imply industrial processes including food processing, or petrol industry. Those applications are very often confronted with non-Newtonian fluids. Nevertheless, to the best of our knowledge, only few studies dealing with vortex dynamics in non-Newtonian shear-thinning fluids exist, and none with viscoelastic ones. The aim for the present study is to characterize experimentally the dynamics of vortex rings generated thanks to a piston-cylinder apparatus in various viscoelastic fluids as a function of the generalized Reynolds number, the piston stroke and the final piston position relative to the cylinder exit. In particular, the elastic property of the fluid will be highlighted by the furling-unfurling of vortex rings.
Spreading of Non-Newtonian and Newtonian Fluids on a Solid Substrate under Pressure
NASA Astrophysics Data System (ADS)
Dutta Choudhury, Moutushi; Chandra, Subrata; Nag, Soma; Das, Shantanu; Tarafdar, Sujata
2011-09-01
Strongly non-Newtonian fluids namely, aqueous gels of starch, are shown to exhibit visco-elastic behavior, when subjected to a load. We study arrowroot and potato starch gels. When a droplet of the fluid is sandwiched between two glass plates and compressed, the area of contact between the fluid and plates increases in an oscillatory manner. This is unlike Newtonian fluids, where the area increases monotonically in a similar situation. The periphery moreover, develops an instability, which looks similar to Saffman Taylor fingers. This is not normally seen under compression. The loading history is also found to affect the manner of spreading. We attempt to describe the non-Newtonian nature of the fluid through a visco-elastic model incorporating generalized calculus. This is shown to reproduce qualitatively the oscillatory variation in the surface strain.
A comparison of numerical methods for non-Newtonian fluid flows in a sudden expansion
NASA Astrophysics Data System (ADS)
Ilio, G. Di; Chiappini, D.; Bella, G.
2016-06-01
A numerical study on incompressible laminar flow in symmetric channel with sudden expansion is conducted. In this work, Newtonian and non-Newtonian fluids are considered, where non-Newtonian fluids are described by the power-law model. Three different computational methods are employed, namely a semi-implicit Chorin projection method (SICPM), an explicit algorithm based on fourth-order Runge-Kutta method (ERKM) and a Lattice Boltzmann method (LBM). The aim of the work is to investigate on the capabilities of the LBM for the solution of complex flows through the comparison with traditional computational methods. In the range of Reynolds number investigated, excellent agreement with the literature results is found. In particular, the LBM is found to be accurate in the prediction of the fluid flow behavior for the problem under consideration.
Massoudi, M.C.; Tran, P.X.
2007-06-15
After providing a brief review of the constitutive modeling of the stress tensor for granular materials using non-Newtonian fluid models, we study the flow between two horizontal flat plates. It is assumed that the granular media behaves as a non-Newtonian fluid (of the Reiner–Rivlin type); we use the constitutive relation derived by Rajagopal and Massoudi [Rajagopal, K. R. and M. Massoudi, “A Method for measuring material moduli of granular materials: flow in an orthogonal rheometer,” Topical Report, DOE/PETC/TR-90/3, 1990] which can predict the normal stress differences. The lower plate is fixed and heated, and the upper plate (which is at a lower temperature than the lower plate) is set into motion with a constant velocity. The steady fully developed flow and the heat transfer equations are made dimensionless and are solved numerically; the effects of different dimensionless numbers and viscous dissipation are discussed.
Non-Newtonian Viscosity Modeling of Crude Oils—Comparison Among Models
NASA Astrophysics Data System (ADS)
Ramírez-González, Patsy V.; Aguayo, Juan Pablo; Quiñones-Cisneros, Sergio E.; Deiters, Ulrich K.
2009-04-01
The presence of precipitated wax or even just low temperatures may induce non-Newtonian rheological behavior in crude oils. Such behavior can be found at operating conditions, for instance, in reservoirs at deep-water conditions. Therefore, reliable rheological models for crude oils applicable over the wide range of conditions the fluid may encounter are essential for a large number of oil technology applications. Such models must also be composition dependent, as many applications require predicting the rheological behavior of the fluid under strong compositional changes, e.g., recovery applications such as vapor extraction (VAPEX) processes or blending of fluids for improved rheological characteristics for piping, among many other applications. In this study, a comparative analysis between some published models applicable to the description of the non-Newtonian behavior of crude oils is carried out. Emphasis is placed on the stability of the model predictions within the wide range of conditions that may be encountered.
FDA's nozzle numerical simulation challenge: non-Newtonian fluid effects and blood damage.
Trias, Miquel; Arbona, Antonio; Massó, Joan; Miñano, Borja; Bona, Carles
2014-01-01
Data from FDA's nozzle challenge-a study to assess the suitability of simulating fluid flow in an idealized medical device-is used to validate the simulations obtained from a numerical, finite-differences code. Various physiological indicators are computed and compared with experimental data from three different laboratories, getting a very good agreement. Special care is taken with the derivation of blood damage (hemolysis). The paper is focused on the laminar regime, in order to investigate non-Newtonian effects (non-constant fluid viscosity). The code can deal with these effects with just a small extra computational cost, improving Newtonian estimations up to a ten percent. The relevance of non-Newtonian effects for hemolysis parameters is discussed.
Perrin, Christian L; Tardy, Philippe M J; Sorbie, Ken S; Crawshaw, John C
2006-03-15
The in situ rheology of polymeric solutions has been studied experimentally in etched silicon micromodels which are idealizations of porous media. The rectangular channels in these etched networks have dimensions typical of pore sizes in sandstone rocks. Pressure drop/flow rate relations have been measured for water and non-Newtonian hydrolyzed-polyacrylamide (HPAM) solutions in both individual straight rectangular capillaries and in networks of such capillaries. Results from these experiments have been analyzed using pore-scale network modeling incorporating the non-Newtonian fluid mechanics of a Carreau fluid. Quantitative agreement is seen between the experiments and the network calculations in the Newtonian and shear-thinning flow regions demonstrating that the 'shift factor,'alpha, can be calculated a priori. Shear-thickening behavior was observed at higher flow rates in the micromodel experiments as a result of elastic effects becoming important and this remains to be incorporated in the network model.
Fingering instability in non-Newtonian fluids during squeeze flow in a Hele-Shaw cell
NASA Astrophysics Data System (ADS)
Dutta Choudhury, M.; Tarafdar, S.
2015-05-01
Instability at the interface separating different fluids, may develop under different conditions, leading to increased roughness of the boundary. A difference in viscosity of the fluids is usually responsible for viscous fingering, this occurs when the pressure on the low viscosity side is higher. We report here a reverse effect when a non-Newtonian fluid is squeezed between two plane surfaces by applying a force. We observe that a wave-like irregularity develops on the interface, though the viscosity of the air surrounding the fluid is negligible compared to the apparent viscosity of the thick potato starch gel under study. Development of the wavelength of the undulations as a function of the fluid composition and other factors is studied. We suggest a qualitative explanation for this effect, which is observed only in non-Newtonian fluids.
FDA’s Nozzle Numerical Simulation Challenge: Non-Newtonian Fluid Effects and Blood Damage
Trias, Miquel; Arbona, Antonio; Massó, Joan; Miñano, Borja; Bona, Carles
2014-01-01
Data from FDA’s nozzle challenge–a study to assess the suitability of simulating fluid flow in an idealized medical device–is used to validate the simulations obtained from a numerical, finite-differences code. Various physiological indicators are computed and compared with experimental data from three different laboratories, getting a very good agreement. Special care is taken with the derivation of blood damage (hemolysis). The paper is focused on the laminar regime, in order to investigate non-Newtonian effects (non-constant fluid viscosity). The code can deal with these effects with just a small extra computational cost, improving Newtonian estimations up to a ten percent. The relevance of non-Newtonian effects for hemolysis parameters is discussed. PMID:24667931
Lattice Boltzmann Modeling of Non-Newtonian Fluid Flow in Porous Medium Systems
NASA Astrophysics Data System (ADS)
Hauswirth, S.; Dye, A. L.; Schultz, P. B.; Bowers, C.; Miller, C. T.
2016-12-01
The ability to predict the behavior of non-Newtonian fluids in porous medium systems is critical for a wide-range of applications, including hydraulic fracturing, enhanced oil recovery, contaminant remediation, and biological systems. Development of accurate macroscale models of such systems requires an understanding of the relationship between the fluid and medium properties at the microscale and averaged macroscale properties. This study focuses specifically on guar gum, a major component of hydraulic fracturing fluids that exhibits Cross-model rheology. A lattice Boltzmann method (LBM) incorporating non-Newtonian behavior was developed and validated against a semi-analytical solution for Cross-model fluid flow between parallel plates. The developed LBM was then used to simulate a series of one-dimensional column flow experiments conducted with a range of fluids and porous medium materials. The computational results were used in conjunction with the experimental data to investigate the relationships between fluid and media properties, microscale physics, and macroscale parameters.
Effect of non-newtonian behavior on hemodynamics of cerebral aneurysms.
Fisher, Carolyn; Rossmann, Jenn Stroud
2009-09-01
Blood flow dynamics near and within cerebral aneurysms have long been implicated in aneurysm growth and rupture. In this study, the governing equations for pulsatile flow are solved in their finite volume formulation to simulate blood flow in a range of three-dimensional aneurysm geometries. Four constitutive models are applied to investigate the influence of non-Newtonian behavior on flow patterns and fluid mechanical forces. The blood's non-Newtonian behavior is found to be more significant, in particular, vascular geometries, and to have pronounced effects on flow and fluid mechanical forces within the aneurysm. The choice of constitutive model has measurable influence on the numerical prediction of aneurysm rupture risk due to fluid stresses, though less influence than aneurysm morphology.
Dynamic wetting of non-newtonian fluids: multicomponent molecular-kinetic approach.
Liang, Zhan-Peng; Wang, Xiao-Dong; Duan, Yuan-Yuan; Min, Qi; Wang, Chi; Lee, Duu-Jong
2010-09-21
Hydrodynamic models are generally applied to describe the dynamic wetting of newtonian or non-newtonian fluids on a solid surface. Conversely, the molecular-kinetic paradigm is only utilized for spreading newtonian fluids while considering the movement of a contact line as a molecular hopping process. This study extended the molecular-kinetic paradigm to the wetting behavior of non-newtonian fluids, while assuming there are n fluid components at the contact line regime interacting simultaneously with a solid surface during front movement. The limiting cases of the derived model at slow and fast moving speeds were discussed. Moreover, the derived model was validated based on dynamic contact angle data of three carboxymethylcellulose (CMC) aqueous solutions measured using the force-balance method. Best-fit parameters were used to interpret the wetting dynamics of CMC solutions.
Shape optimization in unsteady blood flow: a numerical study of non-Newtonian effects.
Abraham, Feby; Behr, Marek; Heinkenschloss, Matthias
2005-06-01
This paper presents a numerical study of non-Newtonian effects on the solution of shape optimization problems involving unsteady pulsatile blood flow. We consider an idealized two dimensional arterial graft geometry. Our computations are based on the Navier-Stokes equations generalized to non-Newtonian fluid, with the modified Cross model employed to account for the shear-thinning behavior of blood. Using a gradient-based optimization algorithm, we compare the optimal shapes obtained using both the Newtonian and generalized Newtonian constitutive equations. Depending on the shear rate prevalent in the domain, substantial differences in the flow as well as in the computed optimal shape are observed when the Newtonian constitutive equation is replaced by the modified Cross model. By varying a geometric parameter in our test case, we investigate the influence of the shear rate on the solution.
NEWTONIAN AND NON-NEWTONIAN MAGNETIC-FIELD RELAXATIONS IN SOLAR-CORONAL MHD
Low, B. C.
2013-05-01
This paper treats the relaxation of a magnetic field into a minimum-energy force-free state in a cold (pressure-less) viscous fluid, under the frozen-in condition of perfect electrical conductivity and letting the viscosity-dissipated energy be completely lost. A non-Newtonian fluid in popular use is studied in relation to the Newtonian viscous fluid, as two alternative numerical means to (1) construct force-free fields representing solar coronal structures in realistic geometry and (2) investigate the Parker theory of spontaneous formation of electric current sheets as a basic MHD process. Faraday's induction equation imposes an independent condition on the fluid velocity at rigid, perfectly conducting boundaries. This boundary condition is quite compatible with Newtonian mechanics but not with the non-Newtonian fluid model where velocity is equated to the Lorentz force with a free, positive multiplicative-factor. This defining property gives rise to unphysical or artificial singularities not previously known that are completely distinct from the physically admissible singularities representing the current sheets of the Parker theory. In particular, the non-Newtonian fluid takes a magnetic field with neutral points from any one of a continuum of initial states into an unphysical state instead of the proper force-free end-state accessible by Newtonian relaxation. The validity of previously published MHD results based on this non-Newtonian fluid, including some counterclaims against the Parker theory, is dubious. Investigating the Parker theory requires numerical relaxation models capable of anticipating and accurately describing inevitable current-sheet singularities. By including a weak resistivity to dissipate the inevitable current sheets as they form, the field can change topology intermittently to seek a terminal force-free state free of singularities. The minimum-energy state of this more complete model corresponds to the long-lived relaxed structures in the
Supersoft symmetry energy encountering non-Newtonian gravity in neutron stars.
Wen, De-Hua; Li, Bao-An; Chen, Lie-Wen
2009-11-20
Considering the non-Newtonian gravity proposed in grand unification theories, we show that the stability and observed global properties of neutron stars cannot rule out the supersoft nuclear symmetry energies at suprasaturation densities. The degree of possible violation of the inverse-square law of gravity in neutron stars is estimated using an equation of state of neutron-rich nuclear matter consistent with the available terrestrial laboratory data.
Supersoft Symmetry Energy Encountering Non-Newtonian Gravity in Neutron Stars
Wen Dehua; Li Baoan; Chen Liewen
2009-11-20
Considering the non-Newtonian gravity proposed in grand unification theories, we show that the stability and observed global properties of neutron stars cannot rule out the supersoft nuclear symmetry energies at suprasaturation densities. The degree of possible violation of the inverse-square law of gravity in neutron stars is estimated using an equation of state of neutron-rich nuclear matter consistent with the available terrestrial laboratory data.
Velocity and shear rate estimates of some non-Newtonian oscillatory flows in tubes
NASA Astrophysics Data System (ADS)
Kutev, N.; Tabakova, S.; Radev, S.
2016-10-01
The two-dimensional Newtonian and non-Newtonian (Carreau viscosity model used) oscillatory flows in straight tubes are studied theoretically and numerically. The corresponding analytical solution of the Newtonian flow and the numerical solution of the Carreau viscosity model flow show differences in velocity and shear rate. Some estimates for the velocity and shear rate differences are theoretically proved. As numerical examples the blood flow in different type of arteries and the polymer flow in pipes are considered.
Increasing heat transfer of non-Newtonian nanofluid in rectangular microchannel with triangular ribs
NASA Astrophysics Data System (ADS)
Shamsi, Mohammad Reza; Akbari, Omid Ali; Marzban, Ali; Toghraie, Davood; Mashayekhi, Ramin
2017-09-01
In this study, computational fluid dynamics and the laminar flow of the non-Newtonian fluid have been numerically studied. The cooling fluid includes water and 0.5 wt% Carboxy methyl cellulose (CMC) making the non-Newtonian fluid. In order to make the best of non-Newtonian nanofluid in this simulation, solid nanoparticles of Aluminum Oxide have been added to the non-Newtonian fluid in volume fractions of 0-2% with diameters of 25, 45 and 100 nm. The supposed microchannel is rectangular and two-dimensional in Cartesian coordination. The power law has been used to speculate the dynamic viscosity of the cooling nanofluid. The field of numerical solution is simulated in the Reynolds number range of 5 < Re < 300. A constant heat flux of 10,000 W/m2 is exercised on the lower walls of the studied geometry. Further, the effect of triangular ribs with angle of attacks of 30°, 45° and 60° is studied on flow parameters and heat transfer due to the fluid flow. The results show that an increase in the volume fraction of nanoparticles as well as the use for nanoparticles with smaller diameters lead to greater heat transfer. Among all the studied forms, the triangular rib from with an angle of attack 30° has the biggest Nusselt number and the smallest pressure drop along the microchannel. Also, an increase in the angle of attack and as a result of a sudden contact between the fluid and the ribs and also a reduction in the coflowing length (length of the rib) cause a cut in heat transfer by the fluid in farther parts from the solid wall (tip of the rib).
Investigating the impact of non-Newtonian blood models within a heart pump.
Al-Azawy, Mohammed G; Turan, A; Revell, A
2017-01-01
A detailed computational fluid dynamics (CFD) study of transient, turbulent blood flow through a positive displacement left ventricular assist device is performed. Two common models for non-Newtonian blood flow are compared to the Newtonian model to investigate their impact on predicted levels of shear rate and wall shear stress. Given that both parameters are directly relevant to the evaluation of risk from thrombus and haemolysis, there is a need to assess the sensitivity to modelling non-Newtonian flow effects within a pulsatile turbulent flow, in order to identify levels of uncertainly in CFD. To capture the effects of turbulence, the elliptic blending Reynolds stress model is used in the present study, on account of superior performance of second moment closure schemes previously identified by the present authors. The CFD configuration includes two cyclically rotating valves and a moving pusher plate to periodically vary the chamber volume. An overset mesh algorithm is used for each instance of mesh motion, and a zero gap technique was employed to ensure full valve closure. The left ventricular assist device was operated at a pumping rate of 86 BPM (beats per minute) and a systolic duration of 40% of the pumping cycle, in line with existing experimental data to which comparisons are made. The sensitivity of the variable viscosity models is investigated in terms of mean flow field, levels of turbulence and global shear rate, and a non-dimensional index is used to directly evaluate the impact of non-Newtonian effects. The clinical relevance of the results is reported along with a discussion of modelling uncertainties, observing that the turbulent kinetic energy is generally predicted to be higher in non-Newtonian flow than that observed in Newtonian flow. Copyright © 2016 John Wiley & Sons, Ltd.
Effect of non-Newtonian fluid properties on bovine sperm motility.
Hyakutake, Toru; Suzuki, Hiroki; Yamamoto, Satoru
2015-09-18
The swimming process by which mammal spermatozoa progress towards an egg within the reproductive organs is important in achieving successful internal fertilization. The viscosity of oviductal mucus is more than two orders of magnitude greater than that of water, and oviductal mucus also has non-Newtonian properties. In this study, we experimentally observed sperm motion in fluids with various fluid rheological properties and investigated the influence of varying the viscosity and whether the fluid was Newtonian or non-Newtonian on the sperm motility. We selected polyvinylpyrrolidone and methylcellulose as solutes to create solutions with different rheological properties. We used the semen of Japanese cattle and investigated the following parameters: the sperm velocity, the straight-line velocity and the amplitude from the trajectory, and the beat frequency from the fragellar movement. In a Newtonian fluid environment, as the viscosity increased, the motility of the sperm decreased. However, in a non-Newtonian fluid, the straight-line velocity and beat frequency were significantly higher than in a Newtonian fluid with comparable viscosity. As a result, the linearity of the sperm movement increased. Additionally, increasing the viscosity brought about large changes in the sperm flagellar shape. At low viscosities, the entire flagellum moved in a curved flapping motion, whereas in the high-viscosity, only the tip of the flagellum flapped. These results suggest that the bovine sperm has evolved to swim toward the egg as quickly as possible in the actual oviduct fluid, which is a high-viscosity non-Newtonian fluid. Copyright © 2015 Elsevier Ltd. All rights reserved.
Classical XY model with conserved angular momentum is an archetypal non-Newtonian fluid.
Evans, R M L; Hall, Craig A; Simha, R Aditi; Welsh, Tom S
2015-04-03
We find that the classical one-dimensional XY model, with angular-momentum-conserving Langevin dynamics, mimics the non-Newtonian flow regimes characteristic of soft matter when subjected to counterrotating boundaries. An elaborate steady-state phase diagram has continuous and first-order transitions between states of uniform flow, shear-banding, solid-fluid coexistence and slip planes. Results of numerical studies and a concise mean-field constitutive relation offer a paradigm for diverse nonequilibrium complex fluids.
Convective Instability in Ice I with Non-Newtonian Rheology: Application to the Galilean Satellites
NASA Technical Reports Server (NTRS)
Barr, A. C.; Zhong, S.; Pappalardo, R. T.
2004-01-01
At the temperatures and stresses associated with the onset of convection in an ice I shell of the Galilean satellites, ice behaves as a non-Newtonian fluid with a viscosity that depends on both temperature and strain rate. The convective stability of a non-Newtonian ice shell can be judged by comparing the Rayleigh number of the shell to a critical value. Previous studies suggest that the critical Rayleigh number for a non-Newtonian fluid depends on the initial conditions in the fluid layer, in addition to the thermal, rheological, and physical properties of the fluid. We seek to extend the existing definition of the critical Rayleigh number for a non-Newtonian, basally heated fluid by quantifying the conditions required to initiate convection in an ice I layer initially in conductive equilibrium. We find that the critical Rayleigh number for the onset of convection in ice I varies as a power (-0.6 to -0.5) of the amplitude of the initial temperature perturbation issued to the layer, when the amplitude of perturbation is less than the rheological temperature scale. For larger-amplitude perturbations, the critical Rayleigh number achieves a constant value. We characterize the critical Rayleigh number as a function of surface temperature of the satellite, melting temperature of ice, and rheological parameters so that our results may be extrapolated for use with other rheologies and for a generic large icy satellite. The values of critical Rayleigh number imply that triggering convection from a conductive equilibrium in a pure ice shell less than 100 km thick in Europa, Ganymede, or Callisto requires a large, localized temperature perturbation of a few kelvins to tens of kelvins to soften the ice and therefore may require tidal dissipation in the ice shell.
Non-Newtonian Momentum Transfer past an Isothermal Stretching Sheet with Applied Suction
NASA Astrophysics Data System (ADS)
Veena, P. H.; Suresh, B.; Pravin, V. K.; Goud, A. M.
2017-08-01
The paper discusses the flow of an incompressible non-Newtonian fluid due to stretching of a plane elastic surface in a saturated porous medium in the approximation of boundary layer theory. An exact analytical solution of non-linear MHD momentum equation governing the self-similar flow is given. The skin friction co-efficient decreases with an increase in the visco-elastic parameter k1 and increase in the values of both the magnetic parameter and permeability parameter.
Convective Instability in Ice I with Non-Newtonian Rheology: Application to the Galilean Satellites
NASA Technical Reports Server (NTRS)
Barr, A. C.; Zhong, S.; Pappalardo, R. T.
2004-01-01
At the temperatures and stresses associated with the onset of convection in an ice I shell of the Galilean satellites, ice behaves as a non-Newtonian fluid with a viscosity that depends on both temperature and strain rate. The convective stability of a non-Newtonian ice shell can be judged by comparing the Rayleigh number of the shell to a critical value. Previous studies suggest that the critical Rayleigh number for a non-Newtonian fluid depends on the initial conditions in the fluid layer, in addition to the thermal, rheological, and physical properties of the fluid. We seek to extend the existing definition of the critical Rayleigh number for a non-Newtonian, basally heated fluid by quantifying the conditions required to initiate convection in an ice I layer initially in conductive equilibrium. We find that the critical Rayleigh number for the onset of convection in ice I varies as a power (-0.6 to -0.5) of the amplitude of the initial temperature perturbation issued to the layer, when the amplitude of perturbation is less than the rheological temperature scale. For larger-amplitude perturbations, the critical Rayleigh number achieves a constant value. We characterize the critical Rayleigh number as a function of surface temperature of the satellite, melting temperature of ice, and rheological parameters so that our results may be extrapolated for use with other rheologies and for a generic large icy satellite. The values of critical Rayleigh number imply that triggering convection from a conductive equilibrium in a pure ice shell less than 100 km thick in Europa, Ganymede, or Callisto requires a large, localized temperature perturbation of a few kelvins to tens of kelvins to soften the ice and therefore may require tidal dissipation in the ice shell.
Smart Fluids in Hydrology: Use of Non-Newtonian Fluids for Pore Structure Characterization
NASA Astrophysics Data System (ADS)
Abou Najm, M. R.; Atallah, N. M.; Selker, J. S.; Roques, C.; Stewart, R. D.; Rupp, D. E.; Saad, G.; El-Fadel, M.
2015-12-01
Classic porous media characterization relies on typical infiltration experiments with Newtonian fluids (i.e., water) to estimate hydraulic conductivity. However, such experiments are generally not able to discern important characteristics such as pore size distribution or pore structure. We show that introducing non-Newtonian fluids provides additional unique flow signatures that can be used for improved pore structure characterization while still representing the functional hydraulic behavior of real porous media. We present a new method for experimentally estimating the pore structure of porous media using a combination of Newtonian and non-Newtonian fluids. The proposed method transforms results of N infiltration experiments using water and N-1 non-Newtonian solutions into a system of equations that yields N representative radii (Ri) and their corresponding percent contribution to flow (wi). This method allows for estimating the soil retention curve using only saturated experiments. Experimental and numerical validation comparing the functional flow behavior of different soils to their modeled flow with N representative radii revealed the ability of the proposed method to represent the water retention and infiltration behavior of real soils. The experimental results showed the ability of such fluids to outsmart Newtonian fluids and infer pore size distribution and unsaturated behavior using simple saturated experiments. Specifically, we demonstrate using synthetic porous media that the use of different non-Newtonian fluids enables the definition of the radii and corresponding percent contribution to flow of multiple representative pores, thus improving the ability of pore-scale models to mimic the functional behavior of real porous media in terms of flow and porosity. The results advance the knowledge towards conceptualizing the complexity of porous media and can potentially impact applications in fields like irrigation efficiencies, vadose zone hydrology, soil
Mathematical modelling of peristaltic transport of a non-Newtonian fluid.
Mernone, A; Mazumdar, J
1998-09-01
The paper considers the phenomena of peristaltic transport of a non-Newtonian fluid represented as a power law fluid. The governing equations are the modified Navier-Stokes equations and the continuity equation in axisymmetric form. A solution is sought in terms of a perturbation series and it is shown the close proximity between analytical and numerical solutions when considering stream functions for various values of the flow behaviour index.
Smoothed particle hydrodynamics non-Newtonian model for ice-sheet and ice-shelf dynamics
Pan, W.; Tartakovsky, A. M.; Monaghan, J. J.
2013-06-01
Mathematical modeling of ice sheets is complicated by the non-linearity of the governing equations and boundary conditions. Standard grid-based methods require complex front tracking techniques and have limited capability to handle large material deformations and abrupt changes in bottom topography. As a consequence, numerical methods are usually restricted to shallow ice sheet and ice shelf approximations. We propose a new smoothed particle hydrodynamics (SPH) non-Newtonian model for coupled ice sheet and ice shelf dynamics. SPH, a fully Lagrangian particle method, is highly scalable and its Lagrangian nature and meshless discretization are well suited to the simulation of free surface flows, large material deformation, and material fragmentation. In this paper, SPH is used to study 3D ice sheet/ice shelf behavior, and the dynamics of the grounding line. The steady state position of the grounding line obtained from SPH simulations is in good agreement with laboratory observations for a wide range of simulated bedrock slopes, and density ratios, similar to those of ice and sea water. The numerical accuracy of the SPH algorithm is verif;ed by simulating Poiseuille flow, plane shear flow with free surface and the propagation of a blob of ice along a horizontal surface. In the laboratory experiment, the ice was represented with a viscous Newtonian fluid. In the present work, however, the ice is modeled as both viscous Newtonian fluid and non-Newtonian fluid, such that the effect of non-Newtonian rheology on the dynamics of grounding line was examined. The non-Newtonian constitutive relation is prescribed to be Glen’s law for the creep of polycrystalline ice. A V-shaped bedrock ramp is further introduced to model the real geometry of bedrock slope.
Pulsatile non-Newtonian haemodynamics in a 3D bifurcating abdominal aortic aneurysm model.
Ma, J; Turan, A
2011-08-01
Numerical prediction of non-Newtonian blood flow in a 3D abdominal aortic aneurysm bifurcating model is carried out. The non-Newtonian Carreau model is used to characterise the shear thinning behaviour of the human blood. A physical inlet velocity waveform incorporating a radial velocity distribution reasonably representative of a practical case configuration is employed. Case studies subject to both equal and unequal outlet pressures at iliac bifurcations are presented to display convincingly the downstream pressure influences on the flow behaviour within the aneurysm. Simulations indicate that the non-Newtonian aspects of the blood cannot at all be neglected or given a cursory treatment. The wall shear stress (WSS) is found to change significantly at both the proximal and distal ends of the aneurysm. At the peak systole, the WSS is peak around the bifurcation point, whereas the WSS becomes zero in the bifurcation point. Differential downstream pressure fields display significant effects regarding the flow evolution in the iliac arteries, whereas little or no effects are observed directly on the flow details in the aneurysm.
Conceptual coherence of non-Newtonian worldviews in Force Concept Inventory data
NASA Astrophysics Data System (ADS)
Scott, Terry F.; Schumayer, Dániel
2017-06-01
The Force Concept Inventory is one of the most popular and most analyzed multiple-choice concept tests used to investigate students' understanding of Newtonian mechanics. The correct answers poll a set of underlying Newtonian concepts and the coherence of these underlying concepts has been found in the data. However, this inventory was constructed after several years of research into the common preconceptions held by students and using these preconceptions as distractors in the questions. Their sole purpose is to deflect non-Newtonian candidates away from the correct answer. Alternatively, one can argue that the responses could also be treated as polling these preconceptions. In this paper we shift the emphasis of the analysis away from the correlation structure of the correct answers and look at the latent traits underlying the incorrect responses. Our analysis models the data employing exploratory factor analysis, which uses regularities in the data to suggest the existence of underlying structures in the cognitive processing of the students. This analysis allows us to determine whether the data support the claim that there are alternate non-Newtonian worldviews on which students' incorrect responses are based. The existence of such worldviews, and their coherence, could explain the resilience of non-Newtonian preconceptions and would have significant implications to the design of instruction methods. We find that there are indeed coherent alternate conceptions of the world which can be categorized using the results of the research that led to the construction of the Force Concept Inventory.
Microsphere interaction with non-Newtonian solid-supported films to model respiratory therapies
NASA Astrophysics Data System (ADS)
Lee, Nathan; Ally, Javed; Kappl, Michael; Butt, Hans-Jürgen
2012-10-01
Films used as lubricants and particle filters interact with microspheres. One example of a biological particle filter is the mucus lining the human respiratory system. In the conducting airways of the respiratory tract, a 10 μm thick layer of mucus sits on top of a periciliary layer. These cilia sweep the mucus towards the nose and mouth whereby debris, such as dust and bacteria that are trapped by the mucus layer, may be expelled from the body. Mucus, like other biofluids, can be modeled after a non-Newtonian fluid due to their viscoelastic properties. Interactions between particles and non-Newtonian thin films have not been widely characterized. Atomic force microscopy (AFM) is an ideal technique due to its ability to measure in the microNewtown and micrometer scale. The AFM setup also allows for calculation of the force from direct contact of the particle with the film. Data from these experiments may further the development aerosol-based respiratory therapies. Factors such as particle size and approach speed are necessary to determine improved parameters for drug deposition and retention. It is the goal of this study to analyze interaction forces between particles and non-Newtonian solid-supported films.
Slip-Flow and Heat Transfer of a Non-Newtonian Nanofluid in a Microtube
Niu, Jun; Fu, Ceji; Tan, Wenchang
2012-01-01
The slip-flow and heat transfer of a non-Newtonian nanofluid in a microtube is theoretically studied. The power-law rheology is adopted to describe the non-Newtonian characteristics of the flow, in which the fluid consistency coefficient and the flow behavior index depend on the nanoparticle volume fraction. The velocity profile, volumetric flow rate and local Nusselt number are calculated for different values of nanoparticle volume fraction and slip length. The results show that the influence of nanoparticle volume fraction on the flow of the nanofluid depends on the pressure gradient, which is quite different from that of the Newtonian nanofluid. Increase of the nanoparticle volume fraction has the effect to impede the flow at a small pressure gradient, but it changes to facilitate the flow when the pressure gradient is large enough. This remarkable phenomenon is observed when the tube radius shrinks to micrometer scale. On the other hand, we find that increase of the slip length always results in larger flow rate of the nanofluid. Furthermore, the heat transfer rate of the nanofluid in the microtube can be enhanced due to the non-Newtonian rheology and slip boundary effects. The thermally fully developed heat transfer rate under constant wall temperature and constant heat flux boundary conditions is also compared. PMID:22615961
Numerical Experiments in Complex Hæmodynamic Flows. Non-Newtonian Effects
NASA Astrophysics Data System (ADS)
Basombrío, Fernando G.; Dari, Enzo A.; Buscaglia, Gustavo C.; Feijóo, Raúl A.
Numerical experiments for non-trivial flows, close to realistic situations in hæmodynamics, are described and interpreted. Two geometries have been selected: an axisymmetric corrugated tube (with periodic boundary conditions) and a 3D bifurcation with an obstructed end (anastomosis). Results concern sensitivity of errors associated to the time-step size and mesh refinement, but essentially consist of the quantitative estimation of non-Newtonian effects based on Casson's rheological model, treated in retarded form. The time-step lag of such effects is the main reason for evaluating the sensitivity of errors. Due to the high computational cost characterizing the problems to be faced, we expect that the present results will be useful when real geometries should be modeled. The main conclusions are that non-Newtonian effects may be relevant (especially for secondary flows) and that, in most cases, for the same level of errors the use of Casson's law does not generate excessive additional computational costs. Thus, within this strategy, the user can accurately solve the problem using this rheological model without having to worry if the non-Newtonian effects are important or not.
Pore-Scale Modeling of Non-Newtonian Shear-Thinning Fluids in Blood Oxygenator Design.
Low, Kenny W Q; van Loon, Raoul; Rolland, Samuel A; Sienz, Johann
2016-05-01
This paper reviews and further develops pore-scale computational flow modeling techniques used for creeping flow through orthotropic fiber bundles used in blood oxygenators. Porous model significantly reduces geometrical complexity by taking a homogenization approach to model the fiber bundles. This significantly simplifies meshing and can avoid large time-consuming simulations. Analytical relationships between permeability and porosity exist for Newtonian flow through regular arrangements of fibers and are commonly used in macroscale porous models by introducing a Darcy viscous term in the flow momentum equations. To this extent, verification of analytical Newtonian permeability-porosity relationships has been conducted for parallel and transverse flow through square and staggered arrangements of fibers. Similar procedures are then used to determine the permeability-porosity relationship for non-Newtonian blood. The results demonstrate that modeling non-Newtonian shear-thinning fluids in porous media can be performed via a generalized Darcy equation with a porous medium viscosity decomposed into a constant term and a directional expression through least squares fitting. This concept is then investigated for various non-Newtonian blood viscosity models. The proposed methodology is conducted with two different porous model approaches, homogeneous and heterogeneous, and validated against a high-fidelity model. The results of the heterogeneous porous model approach yield improved pressure and velocity distribution which highlights the importance of wall effects.
Mantle flow pressure and the angle of subduction - Non-Newtonian corner flows
NASA Technical Reports Server (NTRS)
Tovish, A.; Schubert, G.; Luyendyk, B. P.
1978-01-01
Corner flows of Newtonian and non-Newtonian fluids are used to model the flow in a subduction zone which is viscously driven by the motions of the converging plates and the descending slab. The pressures induced by the flow tend to lift the slab up beneath the overriding plate thereby offsetting the tendency of gravity to align the slab with the vertical. The low angles of subduction observed in Peru and Central Chile may be the result of strong dynamic pressures forcing the slab up against the overriding plate. Viscous coupling between the overriding plate and the downgoing slab is essential if the nonvertical dips of slabs are a consequence of the balance between gravitational and pressure torques. For a Newtonian mantle, shear stresses and pressures on the top of the slab are comparable. If the mantle is non-Newtonian, however, the pressures greatly exceed the shear stresses, for most acute dip angles. Thus frictional forces on the top and bottom surfaces of slabs are less important in resisting slab descent into a non-Newtonian mantle than they are in resisting penetration into a Newtonian mantle.
SPH non-Newtonian Model for Ice Sheet and Ice Shelf Dynamics
Tartakovsky, Alexandre M.; Pan, Wenxiao; Monaghan, Joseph J.
2012-07-07
We propose a new three-dimensional smoothed particle hydrodynamics (SPH) non-Newtonian model to study coupled ice sheet and ice shelf dynamics. Most existing ice sheet numerical models use a grid-based Eulerian approach, and are usually restricted to shallow ice sheet and ice shelf approximations of the momentum conservation equation. SPH, a fully Lagrangian particle method, solves the full momentum conservation equation. SPH method also allows modeling of free-surface flows, large material deformation, and material fragmentation without employing complex front-tracking schemes, and does not require re-meshing. As a result, SPH codes are highly scalable. Numerical accuracy of the proposed SPH model is first verified by simulating a plane shear flow with a free surface and the propagation of a blob of ice along a horizontal surface. Next, the SPH model is used to investigate the grounding line dynamics of ice sheet/shelf. The steady position of the grounding line, obtained from our SPH simulations, is in good agreement with laboratory observations for a wide range of bedrock slopes, ice-to-fluid density ratios, and flux. We examine the effect of non-Newtonian behavior of ice on the grounding line dynamics. The non-Newtonian constitutive model is based on Glen's law for a creeping flow of a polycrystalline ice. Finally, we investigate the effect of a bedrock geometry on a steady-state position of the grounding line.
Studies on heat transfer to Newtonian and non-Newtonian fluids in agitated vessel
NASA Astrophysics Data System (ADS)
Triveni, B.; Vishwanadham, B.; Venkateshwar, S.
2008-09-01
Heat transfer studies to Newtonian and non-Newtonian fluids are carried out in a stirred vessel fitted with anchor/turbine impeller and a coil for heating/cooling with an objective of determining experimentally the heat transfer coefficient of few industrially important systems namely castor oil and its methyl esters, soap solution, CMC and chalk slurries. The effect of impeller geometry, speed and aeration is investigated. Generalized Reynolds and Prandtl numbers are calculated using an apparent viscosity for non-Newtonian fluids. The data is correlated using a Sieder-Tate type equation. A trend of increase in heat transfer coefficient with RPM in presence and absence of solids has been observed. Relatively high values of Nusselt numbers are obtained for non-Newtonian fluids when aeration is coupled with agitation. The contribution of natural convection to heat transfer has been accounted for by incorporating the Grashof number. The correlations developed based on these studies are applied for design of commercial scale soponification reactor. Power per unit volume resulted in reliable design of a reactor.
Transfer of Microparticles across Laminar Streams from Non-Newtonian to Newtonian Fluid.
Ha, Byunghang; Park, Jinsoo; Destgeer, Ghulam; Jung, Jin Ho; Sung, Hyung Jin
2016-04-19
Engineering inertial lift forces and elastic lift forces is explored to transfer microparticles across laminar streams from non-Newtonian to Newtonian fluid. A co-stream of non-Newtonian flow loaded with microparticles (9.9 and 2.0 μm in diameter) and a Newtonian carrier medium flow in a straight rectangular conduit is devised. The elastic lift forces present in the non-Newtonian fluid, undeterred by particle-particle interaction, successfully pass most of the larger (9.9 μm) particles over to the Newtonian fluid. The Newtonian fluid takes over the larger particles and focus them on the equilibrium position, separating the larger particles from the smaller particles. This mechanism enabled processing of densely suspended particle samples. The method offers dilution-free (for number densities up to 10,000 μL(-1)), high throughput (6700 beads/s), and highly efficient (>99% recovery rate, >97% purity) particle separation operated over a wide range of flow rate (2 orders of magnitude).
Are Non-Newtonian Effects Important in Hemodynamic Simulations of Patients With Autogenous Fistula?
Javid Mahmoudzadeh Akherat, S M; Cassel, Kevin; Boghosian, Michael; Dhar, Promila; Hammes, Mary
2017-04-01
Given the current emphasis on accurate computational fluid dynamics (CFD) modeling of cardiovascular flows, which incorporates realistic blood vessel geometries and cardiac waveforms, it is necessary to revisit the conventional wisdom regarding the influences of non-Newtonian effects. In this study, patient-specific reconstructed 3D geometries, whole blood viscosity data, and venous pulses postdialysis access surgery are used as the basis for the hemodynamic simulations of renal failure patients with native fistula access. Rheological analysis of the viscometry data initially suggested that the correct choice of constitutive relations to capture the non-Newtonian behavior of blood is important because the end-stage renal disease (ESRD) patient cohort under observation experience drastic variations in hematocrit (Hct) levels and whole blood viscosity throughout the hemodialysis treatment. For this purpose, various constitutive relations have been tested and implemented in CFD practice, namely Quemada and Casson. Because of the specific interest in neointimal hyperplasia and the onset of stenosis in this study, particular attention is placed on differences in nonhomeostatic wall shear stress (WSS) as that drives the venous adaptation process that leads to venous geometric evolution over time in ESRD patients. Surprisingly, the CFD results exhibit no major differences in the flow field and general flow characteristics of a non-Newtonian simulation and a corresponding identical Newtonian counterpart. It is found that the vein's geometric features and the dialysis-induced flow rate have far greater influence on the WSS distribution within the numerical domain.
Slip-flow and heat transfer of a non-newtonian nanofluid in a microtube.
Niu, Jun; Fu, Ceji; Tan, Wenchang
2012-01-01
The slip-flow and heat transfer of a non-Newtonian nanofluid in a microtube is theoretically studied. The power-law rheology is adopted to describe the non-Newtonian characteristics of the flow, in which the fluid consistency coefficient and the flow behavior index depend on the nanoparticle volume fraction. The velocity profile, volumetric flow rate and local Nusselt number are calculated for different values of nanoparticle volume fraction and slip length. The results show that the influence of nanoparticle volume fraction on the flow of the nanofluid depends on the pressure gradient, which is quite different from that of the Newtonian nanofluid. Increase of the nanoparticle volume fraction has the effect to impede the flow at a small pressure gradient, but it changes to facilitate the flow when the pressure gradient is large enough. This remarkable phenomenon is observed when the tube radius shrinks to micrometer scale. On the other hand, we find that increase of the slip length always results in larger flow rate of the nanofluid. Furthermore, the heat transfer rate of the nanofluid in the microtube can be enhanced due to the non-Newtonian rheology and slip boundary effects. The thermally fully developed heat transfer rate under constant wall temperature and constant heat flux boundary conditions is also compared.
Mantle flow pressure and the angle of subduction - Non-Newtonian corner flows
NASA Technical Reports Server (NTRS)
Tovish, A.; Schubert, G.; Luyendyk, B. P.
1978-01-01
Corner flows of Newtonian and non-Newtonian fluids are used to model the flow in a subduction zone which is viscously driven by the motions of the converging plates and the descending slab. The pressures induced by the flow tend to lift the slab up beneath the overriding plate thereby offsetting the tendency of gravity to align the slab with the vertical. The low angles of subduction observed in Peru and Central Chile may be the result of strong dynamic pressures forcing the slab up against the overriding plate. Viscous coupling between the overriding plate and the downgoing slab is essential if the nonvertical dips of slabs are a consequence of the balance between gravitational and pressure torques. For a Newtonian mantle, shear stresses and pressures on the top of the slab are comparable. If the mantle is non-Newtonian, however, the pressures greatly exceed the shear stresses, for most acute dip angles. Thus frictional forces on the top and bottom surfaces of slabs are less important in resisting slab descent into a non-Newtonian mantle than they are in resisting penetration into a Newtonian mantle.
Chen, Jie; Lu, Xi-Yun
2004-12-01
The non-Newtonian fluid flow in a bifurcation model with a non-planar daughter branch is investigated by using finite element method to solve the three-dimensional Navier-Stokes equations coupled with a non-Newtonian constitutive model, in which the shear thinning behavior of the blood fluid is incorporated by the Carreau-Yasuda model. The objective of this study is to investigate the influence of the non-Newtonian property of fluid as well as of curvature and out-of-plane geometry in the non-planar daughter vessel on wall shear stress (WSS) and flow phenomena. In the non-planar daughter vessel, the flows are typified by the skewing of the velocity profile towards the outer wall, creating a relatively low WSS at the inner wall. In the downstream of the bifurcation, the velocity profiles are shifted towards the flow divider. The low WSS is found at the inner walls of the curvature and the lateral walls of the bifurcation. Secondary flow patterns that swirl fluid from the inner wall of curvature to the outer wall in the middle of the vessel are also well documented for the curved and bifurcating vessels. The numerical results for the non-Newtonian fluid and the Newtonian fluid with original Reynolds number and the corresponding rescaled Reynolds number are presented. Significant difference between the non-Newtonian flow and the Newtonian flow is revealed; however, reasonable agreement between the non-Newtonian flow and the rescaled Newtonian flow is found. Results of this study support the view that the non-planarity of blood vessels and the non-Newtonian properties of blood are an important factor in hemodynamics and may play a significant role in vascular biology and pathophysiology.
Li, Lin; Walker, Andrew M; Rival, David E
2014-01-01
Although a blood analog of aqueous glycerol and xanthan gum was found to replicate the viscoelastic behavior of blood, measurements were restricted to laminar flow. To expand the characterization of a non-Newtonian blood analog of aqueous glycerol and xanthan gum to transitional Reynolds numbers to quantify its behavior as a function of both natural and shear-layer-induced mechanisms. A Newtonian analog and a shear-thinning aqueous glycerol, xanthan gum solution were circulated through an in vitro flow loop replicating both a straight and obstructed artery where transition was initiated through natural and shear-layer-induced mechanisms respectively. Steady and pulsatile pressure drop measurements for both fluids were acquired across a range of Reynolds numbers up to 7600 and Womersley numbers of 4 and 6. In steady and pulsatile straight flow, the non-Newtonian analog presented with reduced pressure drops and prolonged laminar flow to Reynolds numbers of 3200 and 3800 respectively. Upon blockage inclusion, non-Newtonian minor losses were comparable to Newtonian in steady flow and greater in pulsatile flow suggesting an elongation of downstream non-Newtonian recirculation. Although non-Newtonian total system pressure drops in both straight and obstructed flows were lower, the ratio of pressure drop difference between the two fluids decreased through shear-layer-induced transition. These findings not only demonstrated the suitability of using a xanthan gum analog to model blood flow in transitional regimes, but also presented the respective differences in analog behavior as a function of transition mechanism.
Meyer, Perry A.; Kurath, Dean E.; Bamberger, Judith A.; Barnes, Steven M.; Etchells, Arthur W.
2006-03-02
The Waste Treatment Plant (WTP) under construction at the Hanford Site will use pulse jet mixer (PJM) technology for mixing and gas retention control applications in tanks expected to contain waste slurries exhibiting a non-Newtonian rheology. This paper presents the results of theoretical and experimental studies undertaken to establish a methodology to perform reduced-scale mixing tests with PJM systems in non-Newtonian fluids. A theoretical model for mixing cavern formation from steady and pulsed jets is developed and compared with data from a single unsteady jet in a yield stress simulant. Dimensional analysis is used to identify the important dimensionless parameters affecting mixing performance in more complex systems. Scaling laws are proposed based on the modeling and dimensional analysis. Experimental validation of the scaling laws governing unsteady jet mixing in non-Newtonian fluids are also presented. Tests were conducted at three scales using two non-Newtonian simulants. The data were compared non-dimensionally, and the important scale laws were confirmed. The key dimensionless parameters were found to be the Strouhal number (which describes unsteady pulse jet mixer operation), the yield Reynolds number (which governs cavern formation due to non-Newtonian fluid behavior), and the viscous Reynolds number (which determines the flow regime and the degree of turbulence). The experimentally validated scaling laws provide the basis for reduced scale testing of prototypic WTP mixing systems. It is argued that mixing systems developed from reduced scale testing will produce conservative designs at full scale.
NASA Technical Reports Server (NTRS)
Van Den Berg, Arie P.; Yuen, David A.; Van Keken, Peter E.
1995-01-01
Numerical simulations of mantle convection with a composite temperature-dependent, Newtonian and non-Newtonian creep law have revealed a transition in the dominant creep mechanism with the increasing vigour of convection. Newtonian creep is found to dominate in the low Rayleigh number regime. With sufficiently high effective Rayleigh number, the overall creep mechanism in the convective flow becomes non-Newtonian. The transitional Rayleigh number increases strongly with the activation energy. These results would suggest a scenario that in the early epochs of Earth the flow in the mantle would have been governed by non-Newtonian rheology and would have exhibited both strong spatial and temporal fluctuations. With time the flow mechanism would behave like a Newtonian fluid and would have a different time-dependent character. In time-dependent Newtonian-dominated flows there are still localized features with distinctly non-Newtonian character. Our analysis of the relative contributions to the lateral viscosity field supports the idea that the inference of the nature of lateral viscosity heterogeneities by seismic tomography may be strongly contaminated by the dominant non-Newtonian contributions to the total lateral viscosity field.
NASA Technical Reports Server (NTRS)
Van Den Berg, Arie P.; Yuen, David A.; Van Keken, Peter E.
1995-01-01
Numerical simulations of mantle convection with a composite temperature-dependent, Newtonian and non-Newtonian creep law have revealed a transition in the dominant creep mechanism with the increasing vigour of convection. Newtonian creep is found to dominate in the low Rayleigh number regime. With sufficiently high effective Rayleigh number, the overall creep mechanism in the convective flow becomes non-Newtonian. The transitional Rayleigh number increases strongly with the activation energy. These results would suggest a scenario that in the early epochs of Earth the flow in the mantle would have been governed by non-Newtonian rheology and would have exhibited both strong spatial and temporal fluctuations. With time the flow mechanism would behave like a Newtonian fluid and would have a different time-dependent character. In time-dependent Newtonian-dominated flows there are still localized features with distinctly non-Newtonian character. Our analysis of the relative contributions to the lateral viscosity field supports the idea that the inference of the nature of lateral viscosity heterogeneities by seismic tomography may be strongly contaminated by the dominant non-Newtonian contributions to the total lateral viscosity field.
Choi, Hyo Won; Barakat, Abdul I
2005-01-01
Endothelial cell (EC) responsiveness to shear stress is essential for vasoregulation and plays a role in atherogenesis. Although blood is a non-Newtonian fluid, EC flow studies in vitro are typically performed using Newtonian fluids. The goal of the present study was to determine the impact of non-Newtonian behavior on the flow field within a model flow chamber capable of producing flow disturbance and whose dimensions permit Reynolds and Womersley numbers comparable to those present in vivo. We performed two-dimensional computational fluid dynamic simulations of steady and pulsatile laminar flow of Newtonian and non-Newtonian fluids over a backward facing step. In the non-Newtonian simulations, the fluid was modeled as a shear-thinning Carreau fluid. Steady flow results demonstrate that for Re in the range 50-400, the flow recirculation zone downstream of the step is 22-63% larger for the Newtonian fluid than for the non-Newtonian fluid, while spatial gradients of shear stress are larger for the non-Newtonian fluid. In pulsatile flow, the temporal gradients of shear stress within the flow recirculation zone are significantly larger for the Newtonian fluid than for the non-Newtonian fluid. These findings raise the possibility that in regions of flow disturbance, EC mechanotransduction pathways stimulated by Newtonian and non-Newtonian fluids may be different.
Minale, Mario; Caserta, Sergio; Guido, Stefano
2010-01-05
In this work, the microconfined shear deformation of a droplet in an equiviscous non-Newtonian immiscible fluid is investigated by modeling and experiments. A phenomenological model based on the assumption of ellipsoidal shape and taking into account wall effects is proposed for systems made of non-Newtonian second-order fluids. The model, without any adjustable parameters, is tested by comparison with experiments under simple shear flow performed in a sliding plate apparatus, where the ratio between the distance between the confining walls and the droplet radius can be varied. The agreement between model predictions and experimental data is good both in steady state shear and in transient drop retraction upon cessation of flow. The results obtained in this work are relevant for microfluidics applications where non-Newtonian fluids are used.
Smart Fluids in Hydrology: Use of Non-Newtonian Fluids for Pore Structure Characterization
NASA Astrophysics Data System (ADS)
Abou Najm, Majdi; Atallah, Nabil; Selker, John; Roques, Clément; Stewart, Ryan; Rupp, David; Saad, George; El-Fadel, Mutasem
2016-04-01
Classic porous media characterization relies on typical infiltration experiments with Newtonian fluids (i.e., water) to estimate hydraulic conductivity. However, such experiments are generally not able to discern important characteristics such as pore size distribution or pore structure. We show that introducing non-Newtonian fluids provides additional unique flow signatures that can be used for improved pore structure characterization. We present a new method that transforms results of N infiltration experiments using water and N-1 non-Newtonian solutions into a system of equations that yields N representative radii (Ri) and their corresponding percent contribution to flow (wi). Those radii and weights are optimized in terms of flow and porosity to represent the functional hydraulic behavior of real porous media. The method also allows for estimating the soil retention curve using only saturated experiments. Experimental and numerical validation revealed the ability of the proposed method to represent the water retention and functional infiltration behavior of real soils. The experimental results showed the ability of such fluids to outsmart Newtonian fluids and infer pore size distribution and unsaturated behavior using simple saturated experiments. Specifically, we demonstrate using synthetic porous media composed of different combinations of sizes and numbers of capillary tubes that the use of different non-Newtonian fluids enables the prediction of the pore structure. The results advance the knowledge towards conceptualizing the complexity of porous media and can potentially impact applications in fields like irrigation efficiencies, vadose zone hydrology, soil-root-plant continuum, carbon sequestration into geologic formations, soil remediation, petroleum reservoir engineering, oil exploration and groundwater modeling.
Soulis, Johannes V.; Fytanidis, Dimitrios K.; Lampri, Olga P.; Giannoglou, George D.
2016-01-01
Background The temporal variation of the hemodynamic mechanical parameters during cardiac pulse wave is considered as an important atherogenic factor. Applying non-Newtonian blood molecular viscosity simulation is crucial for hemodynamic analysis. Understanding low density lipoprotein (LDL) distribution in relation to flow parameters will possibly spot the prone to atherosclerosis aorta regions. Methods The biomechanical parameters tested were averaged wall shear stress (AWSS), oscillatory shear index (OSI) and relative residence time (RRT) in relation to the LDL concentration. Four non-Newtonian molecular viscosity models and the Newtonian one were tested for the normal human aorta under oscillating flow. The analysis was performed via computational fluid dynamic. Results Tested viscosity blood flow models for the biomechanical parameters yield a consistent aorta pattern. High OSI and low AWSS develop at the concave aorta regions. This is most noticeable in downstream flow region of the left subclavian artery and at concave ascending aorta. Concave aorta regions exhibit high RRT and elevated LDL. For the concave aorta site, the peak LDL value is 35.0% higher than its entrance value. For the convex site, it is 18.0%. High LDL endothelium regions located at the aorta concave site are well predicted with high RRT. Conclusions We are in favor of using the non-Newtonian power law model for analysis. It satisfactorily approximates the molecular viscosity, WSS, OSI, RRT and LDL distribution. Concave regions are mostly prone to atherosclerosis. The flow biomechanical factor RRT is a relatively useful tool for identifying the localization of the atheromatic plaques of the normal human aorta. PMID:28197271
Experimental evidence for use of Non-Newtonian fluids for pore structure characterization
NASA Astrophysics Data System (ADS)
Abou Najm, Majdi; Hauswirth, Scott
2017-04-01
Recent advancements in non-Newtonian fluids research have led to the theoretical development of new method for pore structure characterization. Given the complexity of the developed framework, a numerical solver, referred to as "AAPP method", was built to accommodate a wide range of possible fluid properties and experimental conditions. Using this solver, numerical evaluations revealed promising utility for complementing the use of water in saturated infiltration experiments with different (N-1) non-Newtonian fluids to obtain N different effective pore radii and their contribution to total flow. The method was then tested with synthetic porous media composed of different combinations of capillary tubes showing the ability of the N-1 non-Newtonian fluids to predict with acceptable accuracy the distribution of the pore structure. The numerical evaluations and the experimentation with simple synthetic porous media revealed promising potential out of this method: an ability to predict pore structure that is far beyond the ability of what a similar or even larger number of Newtonian fluids alone can do. To demonstrate the ability on real soils, a series of one-dimensional column experiments was conducted with varying porous medium packings, including a range of Accusands and a polydisperse sand/glass bead mixture. For each packing, distilled water and three concentrations each of guar gum and xanthan gum were injected at a range of flow rates, and the resulting pressure was measured. Data collected from the column experiments were used as inputs for the "AAPP method" to calculate representative pore radii for each media. The model output for varying fluid/flow rate permutations were combined to produce a distribution of pore radii. Independently, the pore radii were determined by x-ray micro-computed tomography (microCT) and these results were compared with results obtained from the new method, and were found to be in good agreement.
Chen, Jie; Lu, Xi-Yun
2006-01-01
The pulsatile flow of non-Newtonian fluid in a bifurcation model with a non-planar daughter branch is investigated numerically by using the Carreau-Yasuda model to take into account the shear thinning behavior of the analog blood fluid. The objective of this study is to deal with the influence of the non-Newtonian property of fluid and of out-of-plane curvature in the non-planar daughter vessel on wall shear stress (WSS), oscillatory shear index (OSI), and flow phenomena during the pulse cycle. The non-Newtonian property in the daughter vessels induces a flattened axial velocity profile due to its shear thinning behavior. The non-planarity deflects flow from the inner wall of the vessel to the outer wall and changes the distribution of WSS along the vessel, in particular in systole phase. Downstream of the bifurcation, the velocity profiles are shifted toward the flow divider, and low WSS and high shear stress temporal oscillations characterized by OSI occur on the outer wall region of the daughter vessels close to the bifurcation. Secondary motions become stronger with the addition of the out-of-plane curvature induced by the bending of the vessel, and the secondary flow patterns swirl along the non-planar daughter vessel. A significant difference between the non-Newtonian and the Newtonian pulsatile flow is revealed during the pulse cycle; however, reasonable agreement between the non-Newtonian and the rescaled Newtonian flow is found. Calculated results for the pulsatile flow support the view that the non-planarity of blood vessels and the non-Newtonian properties of blood are an important factor in hemodynamics and may play a significant role in vascular biology and pathophysiology.
Matrix transformations between certain sequence spaces over the non-Newtonian complex field.
Kadak, Uğur; Efe, Hakan
2014-01-01
In some cases, the most general linear operator between two sequence spaces is given by an infinite matrix. So the theory of matrix transformations has always been of great interest in the study of sequence spaces. In the present paper, we introduce the matrix transformations in sequence spaces over the field ℂ(*) and characterize some classes of infinite matrices with respect to the non-Newtonian calculus. Also we give the necessary and sufficient conditions on an infinite matrix transforming one of the classical sets over ℂ(*) to another one. Furthermore, the concept for sequence-to-sequence and series-to-series methods of summability is given with some illustrated examples.
Learning About Non-Newtonian Fluids in a Student-Driven Classroom
NASA Astrophysics Data System (ADS)
Dounas-Frazer, D. R.; Lynn, J.; Zaniewski, A. M.; Roth, N.
2013-01-01
We describe a simple, low-cost experiment and corresponding pedagogical strategies for studying fluids whose viscosities depend on shear rate, referred to as "non-Newtonian fluids." We developed these materials teaching for the Compass Project, an organization that fosters a creative, diverse, and collaborative community of science students at UC Berkeley. Incoming freshmen worked together in a week-long residential program to explore physical phenomena through a combination of conceptual model-building and hands-on experimentation. During the program, students were exposed to three major aspects of scientific discovery: developing a model, testing the model, and investigating deviations from the model.
Theory of non-Newtonian viscosity of red blood cell suspension: effect of red cell deformation.
Murata, T
1983-01-01
The effects of the deformation of red blood cells on non-Newtonian viscosity of a concentrated red cell suspension are investigated theoretically. To simplify the problem an elastic spherical shell filled with an incompressible Newtonian fluid is considered as a model of a normal red cell. The equation of the surface of the shell suspended in a steady simple shear flow is calculated on the assumption that the deformation from a spherical shape is very small. The relative viscosity of a concentrated suspension of such particles is obtained based on the "free surface cell" method proposed by Happel. It is shown that the relative viscosity decreases as the shear rate increases.
Simulation of non-Newtonian oil-water core annular flow through return bends
NASA Astrophysics Data System (ADS)
Jiang, Fan; Wang, Ke; Skote, Martin; Wong, Teck Neng; Duan, Fei
2017-07-01
The volume of fluid (VOF) model is used together with the continuum surface force (CSF) model to numerically simulate the non-Newtonian oil-water core annular flow across return bends. A comprehensive study is conducted to generate the profiles of pressure, velocity, volume fraction and wall shear stress for different oil properties, flow directions, and bend geometries. It is revealed that the oil core may adhere to the bend wall under certain operating conditions. Through the analysis of the total pressure gradient and fouling angle, suitable bend geometric parameters are identified for avoiding the risk of fouling.
Postglacial rebound with a non-Newtonian upper mantle and a Newtonian lower mantle rheology
NASA Technical Reports Server (NTRS)
Gasperini, Paolo; Yuen, David A.; Sabadini, Roberto
1992-01-01
A composite rheology is employed consisting of both linear and nonlinear creep mechanisms which are connected by a 'transition' stress. Background stress due to geodynamical processes is included. For models with a non-Newtonian upper-mantle overlying a Newtonian lower-mantle, the temporal responses of the displacements can reproduce those of Newtonian models. The average effective viscosity profile under the ice-load at the end of deglaciation turns out to be the crucial factor governing mantle relaxation. This can explain why simple Newtonian rheology has been successful in fitting the uplift data over formerly glaciated regions.
Non-Newtonian fluid effects on surface reactions in a microfluidic flow cell
NASA Astrophysics Data System (ADS)
Akgül, M. Bahattin; Sarı, Gözde; Pakdemirli, Mehmet
2012-11-01
Mass transfer over a reactive surface in microfluidic flow cells plays a key role in understanding biomoleculer interactions and diagnosis of small molecules for biomedical and environmental applications. The effects of Non-Newtonian power law fluid on the binding reaction kinetic of immunoglobulin G in a flow cell are analyzed in this study. Governing equations for the fluid flow, mass transport and surface reaction are derived. The finite element method is employed to solve resulting equations. In addition, the effects of volumetric flow rate, fluid behavior index and reaction constants on the surface reaction are analyzed and presented graphically.
NASA Technical Reports Server (NTRS)
Pappalardo, R. T.; Barr, A. C.
2004-01-01
Numerical modeling of non-Newtonian convection in ice shows that convection controlled by grain boundary sliding rheology may occur in Europa. This modeling confirms that thermal convection alone cannot produce significant dome elevations. Domes may instead be produced by diapirs initiated by thermal convection that in turn induces compositional segregation. Exclusion of impurities from warm upwellings would allow sufficient buoyancy for icy plumes to account for the observed approximately 100 m topography of domes, provided the ice shell has a small effective elastic thickness (approximately 0.2 to 0.5 km) and contains low eutectic-point impurities at the few percent level.
Homogenization of an incompressible non-Newtonian flow through a thin porous medium
NASA Astrophysics Data System (ADS)
Anguiano, María; Suárez-Grau, Francisco Javier
2017-04-01
In this paper, we consider a non-Newtonian flow in a thin porous medium Ω _{ɛ} of thickness ɛ which is perforated by periodically solid cylinders of size a_{ɛ}. The flow is described by the 3D incompressible Stokes system with a nonlinear viscosity, being a power of the shear rate (power law) of flow index 1
A fractional-order Maxwell model for non-Newtonian fluids
NASA Astrophysics Data System (ADS)
Carrera, Y.; Avila-de la Rosa, G.; Vernon-Carter, E. J.; Alvarez-Ramirez, J.
2017-09-01
This work considers an extension of the fractional-order Maxwell arrangement to incorporate a relaxation process with non-Newtonian viscosity behavior. The resulting model becomes a fractional-order nonlinear differential equation with stable solution converging asymptotically to a unique equilibrium point. Expressions for the corresponding storage and loss moduli as function of strain frequency and amplitude are computed via a first-harmonic analysis of the differential equation. Some distinctive features and their relationship to the classical and fractional-order linear Maxwell models are discussed. Three examples are used to illustrate the ability of the fractional-order Maxwell model to describe experimental data.
Numerical Solution of Hydrodynamics Lubrications with Non-Newtonian Fluid Flow
NASA Astrophysics Data System (ADS)
Osman, Kahar; Sheriff, Jamaluddin Md; Bahak, Mohd. Zubil; Bahari, Adli; Asral
2010-06-01
This paper focuses on solution of numerical model for fluid film lubrication problem related to hydrodynamics with non-Newtonian fluid. A programming code is developed to investigate the effect of bearing design parameter such as pressure. A physical problem is modeled by a contact point of sphere on a disc with certain assumption. A finite difference method with staggered grid is used to improve the accuracy. The results show that the fluid characteristics as defined by power law fluid have led to a difference in the fluid pressure profile. Therefore a lubricant with special viscosity can reduced the pressure near the contact area of bearing.
Pullback Asymptotic Behavior of Solutions for a 2D Non-autonomous Non-Newtonian Fluid
NASA Astrophysics Data System (ADS)
Liu, Guowei
2016-10-01
This paper studies the pullback asymptotic behavior of solutions for the non-autonomous incompressible non-Newtonian fluid in 2D bounded domains. Firstly, with a little high regularity of the force, the semigroup method and ɛ -regularity method are used to establish the existence of compact pullback absorbing sets. Then, with a minimal regularity of the force, by verifying the flattening property also known as the "Condition (C)", the author proves the existence of pullback attractors for the universe of fixed bounded sets and for the another universe given by a tempered condition. Furthermore, the regularity of pullback attractors is given.
Flow non-normality-induced transient growth in superposed Newtonian and non-Newtonian fluid layers.
Camporeale, C; Gatti, F; Ridolfi, L
2009-09-01
In recent years non-normality and transient growths have attracted much interest in fluid mechanics. Here, we investigate these topics with reference to the problem of interfacial instability in superposed Newtonian and non-Newtonian fluid layers. Under the hypothesis of the lubrication theory, we demonstrate the existence of significant transient growths in the parameter space region where the dynamical system is asymptotically stable, and show how they depend on the main physical parameters. In particular, the key role of the density ratio is highlighted.
Weak solutions for a non-Newtonian diffuse interface model with different densities
NASA Astrophysics Data System (ADS)
Abels, Helmut; Breit, Dominic
2016-11-01
We consider weak solutions for a diffuse interface model of two non-Newtonian viscous, incompressible fluids of power-law type in the case of different densities in a bounded, sufficiently smooth domain. This leads to a coupled system of a nonhomogenouos generalized Navier-Stokes system and a Cahn-Hilliard equation. For the Cahn-Hilliard part a smooth free energy density and a constant, positive mobility is assumed. Using the {{L}∞} -truncation method we prove existence of weak solutions for a power-law exponent p>\\frac{2d+2}{d+2} , d = 2, 3.
Postglacial rebound with a non-Newtonian upper mantle and a Newtonian lower mantle rheology
NASA Technical Reports Server (NTRS)
Gasperini, Paolo; Yuen, David A.; Sabadini, Roberto
1992-01-01
A composite rheology is employed consisting of both linear and nonlinear creep mechanisms which are connected by a 'transition' stress. Background stress due to geodynamical processes is included. For models with a non-Newtonian upper-mantle overlying a Newtonian lower-mantle, the temporal responses of the displacements can reproduce those of Newtonian models. The average effective viscosity profile under the ice-load at the end of deglaciation turns out to be the crucial factor governing mantle relaxation. This can explain why simple Newtonian rheology has been successful in fitting the uplift data over formerly glaciated regions.
Rheological non-Newtonian behaviour of ethylene glycol-based Fe2O3 nanofluids.
Pastoriza-Gallego, María Jose; Lugo, Luis; Legido, José Luis; Piñeiro, Manuel M
2011-10-25
The rheological behaviour of ethylene glycol-based nanofluids containing hexagonal scalenohedral-shaped α-Fe2O3 (hematite) nanoparticles at 303.15 K and particle weight concentrations up to 25% has been carried out using a cone-plate Physica MCR rheometer. The tests performed show that the studied nanofluids present non-Newtonian shear-thinning behaviour. In addition, the viscosity at a given shear rate is time dependent, i.e. the fluid is thixotropic. Finally, using strain sweep and frequency sweep tests, the storage modulus G', loss modulus G″ and damping factor were determined as a function of the frequency showing viscoelastic behaviour for all samples.
NASA Technical Reports Server (NTRS)
Pappalardo, R. T.; Barr, A. C.
2004-01-01
Numerical modeling of non-Newtonian convection in ice shows that convection controlled by grain boundary sliding rheology may occur in Europa. This modeling confirms that thermal convection alone cannot produce significant dome elevations. Domes may instead be produced by diapirs initiated by thermal convection that in turn induces compositional segregation. Exclusion of impurities from warm upwellings would allow sufficient buoyancy for icy plumes to account for the observed approximately 100 m topography of domes, provided the ice shell has a small effective elastic thickness (approximately 0.2 to 0.5 km) and contains low eutectic-point impurities at the few percent level.
Non-Newtonian Blood Flow in Portal Vein with Thrombosis: A Study by Computational Fluid Dynamics
NASA Astrophysics Data System (ADS)
Soares, A. A.; Gonzaga, S.; Silva, José Silvestre; Marinho, D.; Silva, A.; Rouboa, Abel
2011-09-01
We investigate the effects on non-Newtonian blood flow model on the wall shear stress (wss), velocity and viscosity distributions. The 3D Navier-Stokes equations coupled with viscosity models describing the steady flow in Portal Vein have been solved numerically. Three blood viscosity models (Newtonian, Power-law and Carreau) are used in numerical simulations. The results highlight the influence of these models on the blood flow and show that the viscosity model of blood may have significant impact on the numerical results especially in the region of the thrombosis.
Apparao, Siddangouda; Biradar, Trimbak Vaijanath; Naduvinamani, Neminath Bhujappa
2014-01-01
Theoretical study of non-Newtonian effects of second-order fluids on the performance characteristics of inclined slider bearings is presented. An approximate method is used for the solution of the highly nonlinear momentum equations for the second-order fluids. The closed form expressions for the fluid film pressure, load carrying capacity, frictional force, coefficient of friction, and centre of pressure are obtained. The non-Newtonian second order fluid model increases the film pressure, load carrying capacity, and frictional force whereas the center of pressure slightly shifts towards exit region. Further, the frictional coefficient decreases with an increase in the bearing velocity as expected for an ideal fluid. PMID:27437446
Apparao, Siddangouda; Biradar, Trimbak Vaijanath; Naduvinamani, Neminath Bhujappa
2014-01-01
Theoretical study of non-Newtonian effects of second-order fluids on the performance characteristics of inclined slider bearings is presented. An approximate method is used for the solution of the highly nonlinear momentum equations for the second-order fluids. The closed form expressions for the fluid film pressure, load carrying capacity, frictional force, coefficient of friction, and centre of pressure are obtained. The non-Newtonian second order fluid model increases the film pressure, load carrying capacity, and frictional force whereas the center of pressure slightly shifts towards exit region. Further, the frictional coefficient decreases with an increase in the bearing velocity as expected for an ideal fluid.
Alshare, Aiman; Tashtoush, Bourhan; El-Khalil, Hossam H
2013-11-01
Steady flow simulations of blood flow in an axisymmetric stenosed artery, subjected to a static magnetic field, are performed to investigate the influence of artery size, magnetic field strength, and non-Newtonian behavior on artery wall shear stress and pressure drop in the stenosed section. It is found that wall shear stress and pressure drop increase by decreasing artery size, assuming non-Newtonian fluid, and increasing magnetic field strength. In the computations, the shear thinning behavior of blood is accounted for by the Carreau-Yasuda model. Computational results are compared and found to be inline with available experimental data.
Novel Microstructures for Polymer-Liquid Crystal Composite Materials
NASA Technical Reports Server (NTRS)
Magda, Jules J.
2004-01-01
There are a number of interface-dominated composite materials that contain a liquid crystalline (LC) phase in intimate contact with an isotropic phase. For example, polymer- dispersed liquid crystals, used in the fabrication of windows with switchable transparency, consist of micron size LC droplets dispersed in an isotropic polymer matrix. Many other types of liquid crystal composite materials can be envisioned that might have outstanding optical properties that could be exploited in novel chemical sensors, optical switches, and computer displays. This research project was based on the premise that many of these potentially useful LC composite materials can only be fabricated under microgravity conditions where gravity driven flows are absent. In the ground-based research described below, we have focused on a new class of LC composites that we call thermotropic- lyotropic liquid crystal systems (TLLCs). TLLCs consist of nanosize droplets of water dispersed in an LC matrix, with surfactants at the interface that stabilize the structure. By varying the type of surfactant one can access almost an infinite variety of unusual LC composite microstructures. Due to the importance of the interface in these types of systems, we have also developed molecular simulation models for liquid crystals at interfaces, and made some of the first measurements of the interfacial tension between liquid crystals and water.
NASA Astrophysics Data System (ADS)
Coyajee, Emil; Boersma, Bendiks Jan
2009-07-01
The gravity-driven motion of a droplet impacting on a liquid-liquid interface is studied. The full Navier-Stokes equations are solved on a fixed, uniform grid using a finite difference/front-capturing method. For the representation of fluid-fluid interfaces, a coupled Level-Set/Volume-Of-Fluid method [M. Sussman, E.G. Puckett, A coupled Level-Set and Volume-of-Fluid method for computing 3D and axisymmetric incompressible two-phase flows, J. Comp. Phys. 162 (2000) 301-337] is used, in which we introduce the novel approach of describing separate interfaces with different marker functions. As a consequence, we prevent numerical coalescence of the droplet and the liquid-liquid interface without excessive (local) grid refinement. To validate our method, numerical simulations of the drop impact event are compared with experiments [Z. Mohamed-Kassim, E.K. Longmire, Drop impact on a liquid-liquid interface, Phys. Fluids 15 (2003) 3263-3273]. Furthermore, a comparison is made with the numerical results of [A. Esmaeeli, G. Tryggvason, Direct numerical simulations of bubbly flows. Part 2. Moderate Reynolds number arrays, J. Fluid Mech. 385 (1999) 325-358] for an array of rising bubbles. The investigation shows that the multiple marker approach successfully prevents numerical coalescence of interfaces and adequately captures the effect of surface tension.
Transition to Non-Newtonian behavior of blood suspensions flowing in small tubes
NASA Astrophysics Data System (ADS)
Caswell, Bruce; Lei, Huan; Fedosov, Dmitry; Karniadakis, George
2011-11-01
Blood flow in tubes is widely considered to be Newtonian down to diameters of about 200 microns. We have employed a multi-scale, Dissipative Particle Dynamics (DPD) model of the red blood cell (RBC) to investigate suspensions driven through small tubes (diameters 20-150 microns). The cross-stream stress gradient induces radial migration of the suspended RBCs resulting in the formation of a hematocrit (H) peak at the centerline, and at the wall a cell-free layer (CFL) whose edge is the point of maximum RBC distortion. This suggests that hard-sphere suspension theories will not capture well blood flow in tubes. For the larger tubes the velocity profiles beyond the CFL are essentially parabolic even though the core H is non-uniform. As the diameter decreases: (1) the CFL moves inward and the central H peak grows, but for the smallest (20 microns) the H peak is shifted off-center, (2) the bulk velocity profiles become similar to those of a shear-thinning non-Newtonian fluid. However, accurate modeling of the velocity field of the bulk flow in small tubes as a homogeneous non-Newtonian fluid can only be achieved if model parameters are taken to depend on tube diameter and pressure drop.
Non-Newtonian Crystal- and Bubble-Rich Lava Rheology in Compression
NASA Astrophysics Data System (ADS)
Lavallee, Y.; Hess, K.; Cordonnier, B.; Dingwell, D. B.
2006-12-01
Volcanic eruption models are still hampered by the lack of multiphase magmatic rheology laws. Fortunately, the lack of sufficient rheological data for lavas bearing crystals and vesicles is now being systematically experimentally addressed. Most rheological models consider suspension rheology according to the Einstein- Roscoe equation or a modification of it. This approach does not contain a Non-Newtonian description (strain- rate dependence). Here, experiments using high-load, high-temperature uniaxial apparatus were carried out to simulate multiphase lava deformation under stresses ranging from 1 to 70 MPa. Samples from Unzen, Colima, Anak Krakatau and Bezymianny (containing 30, 50, 70 and 80 % phenocrysts, and 5, 8, 23 and 9 % vesicles, respectively) were chosen for this study. Obtained results reveal that multiphase lavas behave as pseudo-plastic fluids exhibiting an important component of shear thinning. The viscosity of all lavas decreases exponentially by ca. 1.5 log units between the strain rates of 10-6 and 10-3 s-1; point at which viscous heating and micro-cracking begin to be detected. The strong exponential dependence of the viscosity on strain rate holds the promise of yielding a Non-Newtonian rheology law and consequentially challenges the completeness of the Einstein-Roscoe equation to treat suspension rheology in volcanic eruption models.
NASA Astrophysics Data System (ADS)
Singh, U. P.; Medhavi, Amit; Gupta, R. S.; Bhatt, Siddharth Shankar
2017-07-01
Peristaltic transport is an important mechanism of physiological phenomenon and peristaltic pumps. With the advancement of medical science, it has been established that the physiological fluids do not behave like Newtonian fluids. Therefore, in order to understand the behaviour and properties of physiological fluids during peristalsis, selection of appropriate fluid model is of great importance. In the present investigation, properties of peristaltic transport through nonuniform tube have been studied for non-Newtonian fluids using Rabinowitsch fluid model. Theoretical analysis has been presented for long wavelength and low Reynolds number approximation. To analyse various properties of the flow, analytical expressions for velocity, pressure gradient, pressure rise, friction force, and temperature have been obtained. The numerical results for the same have been obtained to present the effect of various physical and flow parameters on fluid velocity, pressure rise, friction force, and temperature. Significant variation of these properties has been observed in the analysis for non-Newtonian nature of the fluid and nonuniformity of the tube.
Non-Newtonian fluid model incorporated into elastohydrodynamic lubrication of rectangular contacts
NASA Technical Reports Server (NTRS)
Jacobson, B. O.; Hamrock, B. J.
1984-01-01
A procedure is outlined for the numerical solution of the complete elastohydrodynamic lubrication of rectangular contacts incorporating a non-Newtonian fluid model. The approach uses a Newtonian model as long as the shear stress is less than a limiting shear stress. If the shear stress exceeds the limiting value, the shear stress is set equal to the limiting value. The numerical solution requires the coupled solution of the pressure, film shape, and fluid rheology equations from the inlet to the outlet. Isothermal and no-side-leakage assumptions were imposed in the analysis. The influence of dimensionless speed, load, materials, and sliding velocity and limiting-shear-strength proportionality constant on dimensionless minimum film thickness was investigated. Fourteen cases were used in obtaining the minimum-film-thickness equation for an elastohydrodynamically lubricated rectangular contact incorporating a non-Newtonian fluid model. Computer plots are also presented that indicate in detail pressure distribution, film shape, shear stress at the surfaces, and flow throughout the conjunction.
Non-Newtonian Fluid Model Incorporated into Elastohydrodynamic Lubrication of Rectangular Contacts
NASA Technical Reports Server (NTRS)
Jacobson, B. O.; Hamrock, B. J.
1983-01-01
A procedure is outlined for the numerical solution of the complete elastohydrodynamic lubrication of rectangular contacts incorporating a non-Newtonian fluid model. The approach uses a Newtonian model as long as the shear stress is less than a limiting shear stress. If the shear stress exceeds the limiting value, the shear stress is set equal to the limiting value. The numerical solution requires the coupled solution of the pressure, film shape, and fluid rheology equations from the inlet to the outlet. Isothermal and no-side-leakage assumptions were imposed in the analysis. The influence of dimensionless speed, load, materials, and sliding velocity and limiting-shear-strength proportionality constant on dimensionless minimum film thickness was investigated. Fourteen cases were used in obtaining the minimum-film-thickness equation for an elastohydrodynamically lubricated rectangular contact incorporating a non-Newtonian fluid model. Computer plots are also presented that indicate in detail pressure distribution, film shape, shear stress at the surfaces, and flow throughout the conjunction.
Minimal model for zero-inertia instabilities in shear-dominated non-Newtonian flows.
Boi, S; Mazzino, A; Pralits, J O
2013-09-01
The emergence of fluid instabilities in the relevant limit of vanishing fluid inertia (i.e., arbitrarily close to zero Reynolds number) has been investigated for the well-known Kolmogorov flow. The finite-time shear-induced order-disorder transition of the non-Newtonian microstructure and the corresponding viscosity change from lower to higher values are the crucial ingredients for the instabilities to emerge. The finite-time low-to-high viscosity change for increasing shear characterizes the rheopectic fluids. The instability does not emerge in shear-thinning or -thickening fluids where viscosity adjustment to local shear occurs instantaneously. The lack of instabilities arbitrarily close to zero Reynolds number is also observed for thixotropic fluids, in spite of the fact that the viscosity adjustment time to shear is finite as in rheopectic fluids. Renormalized perturbative expansions (multiple-scale expansions), energy-based arguments (on the linearized equations of motion), and numerical results (of suitable eigenvalue problems from the linear stability analysis) are the main tools leading to our conclusions. Our findings may have important consequences in all situations where purely hydrodynamic fluid instabilities or mixing are inhibited due to negligible inertia, as in microfluidic applications. To trigger mixing in these situations, suitable (not necessarily viscoelastic) non-Newtonian fluid solutions appear as a valid answer. Our results open interesting questions and challenges in the field of smart (fluid) materials.
Non-Newtonian fluid model incorporated into elastohydrodynamic lubrication of rectangular contacts
NASA Technical Reports Server (NTRS)
Jacobson, B. O.; Hamrock, B. J.
1984-01-01
A procedure is outlined for the numerical solution of the complete elastohydrodynamic lubrication of rectangular contacts incorporating a non-Newtonian fluid model. The approach uses a Newtonian model as long as the shear stress is less than a limiting shear stress. If the shear stress exceeds the limiting value, the shear stress is set equal to the limiting value. The numerical solution requires the coupled solution of the pressure, film shape, and fluid rheology equations from the inlet to the outlet. Isothermal and no-side-leakage assumptions were imposed in the analysis. The influence of dimensionless speed, load, materials, and sliding velocity and limiting-shear-strength proportionality constant on dimensionless minimum film thickness was investigated. Fourteen cases were used in obtaining the minimum-film-thickness equation for an elastohydrodynamically lubricated rectangular contact incorporating a non-Newtonian fluid model. Computer plots are also presented that indicate in detail pressure distribution, film shape, shear stress at the surfaces, and flow throughout the conjunction.
Newtonian and non-Newtonian blood flow in coiled cerebral aneurysms.
Morales, Hernán G; Larrabide, Ignacio; Geers, Arjan J; Aguilar, Martha L; Frangi, Alejandro F
2013-09-03
Endovascular coiling aims to isolate the aneurysm from blood circulation by altering hemodynamics inside the aneurysm and triggering blood coagulation. Computational fluid dynamics (CFD) techniques have the potential to predict the post-operative hemodynamics and to investigate the complex interaction between blood flow and coils. The purpose of this work is to study the influence of blood viscosity on hemodynamics in coiled aneurysms. Three image-based aneurysm models were used. Each case was virtually coiled with a packing density of around 30%. CFD simulations were performed in coiled and untreated aneurysm geometries using a Newtonian and a Non-Newtonian fluid models. Newtonian fluid slightly overestimates the intra-aneurysmal velocity inside the aneurysm before and after coiling. There were numerical differences between fluid models on velocity magnitudes in coiled simulations. Moreover, the non-Newtonian fluid model produces high viscosity (>0.007 [Pas]) at aneurysm fundus after coiling. Nonetheless, these local differences and high-viscous regions were not sufficient to alter the main flow patterns and velocity magnitudes before and after coiling. To evaluate the influence of coiling on intra-aneurysmal hemodynamics, the assumption of a Newtonian fluid can be used.
Electrophoresis of a concentrated aqueous dispersion of non-Newtonian drops.
Lee, Eric; Chang, Chia-Jeng; Hsu, Jyh-Ping
2005-02-15
The electrophoresis of a concentrated dispersion of non-Newtonian drops in an aqueous medium, which has not been investigated theoretically in the literature, is analyzed under conditions of low zeta potential and weak applied electric field. The results obtained provide a theoretical basis for the characterization of the nature of an emulsion and a microemulsion system. A Carreau fluid, which has wide applications in practice, is chosen for the non-Newtonian drops, and the unit cell model of Kuwabara is adopted to simulate a dispersion. The effects of the key parameters of a dispersion, including its concentration, the shear-thinning nature of the drop fluid, and the thickness of the double layer, on the electrophoretic behavior of a drop are discussed. In general, the more significant the shear-thinning nature of the drop fluid is, the larger the mobility is, and this effect is pronounced as the thickness of the double layer decreases. However, if the double layer is sufficiently thick, this effect becomes negligible. In general, the higher the concentration of drops is, the smaller the mobility is; however, if the double layer is either sufficiently thin or sufficiently thick, this effect becomes unimportant.
Analysis of flow behavior of non-Newtonian fluids based on a concept of traveling force.
Furuse, H; Toda, K
1999-01-01
The non-Newtonian flow behavior of a culture fluid with suspended adhesive particles of microbes and polysaccharides is analyzed in this study based on a new concept. The concept assumes that the force generated by the contact between particles under shearing flow due to mixing is decreasingly transmitted through the fluid in radial directions. A viscosity equation that includes the degree of force transmisson is derived by considering the shear stress to the force. On the other hand, the shear stress dependence on the concentration of bound particles is expressed in an equation by introducing an effective shear stress that works on the contact sites of the bindings and varies the concentration. Relating the degree of force transmission to the concentration derives a non-Newtonian viscosity equation in terms of shear stress (or shear rate), in which zero-shear viscosity is correlated with both the particle concentration and molecular weight of polymers. It is confirmed that calculations based on the equation are in good agreement with experimental results previously reported for aqueous solutions of several polysaccharides.
Electroosmotic flows of non-Newtonian power-law fluids in a cylindrical microchannel.
Zhao, Cunlu; Yang, Chun
2013-03-01
EOF of non-Newtonian power-law fluids in a cylindrical microchannel is analyzed theoretically. Specially, exact solutions of electroosmotic velocity corresponding to two special fluid behavior indices (n = 0.5 and 1.0) are found, while approximate solutions are derived for arbitrary values of fluid behavior index. It is found that because of the approximation for the first-order modified Bessel function of the first kind, the approximate solutions introduce largest errors for predicting electroosmotic velocity when the thickness of electric double layer is comparable to channel radius, but can accurately predict the electroosmotic velocity when the thickness of electric double layer is much smaller or larger than the channel radius. Importantly, the analysis reveals that the Helmholtz-Smoluchowski velocity of power-law fluids in cylindrical microchannels becomes dependent on geometric dimensions (radius of channel), standing in stark contrast to the Helmholtz-Smoluchowski velocity over planar surfaces or in parallel-plate microchannels. Such interesting and counterintuitive effects can be attributed to the nonlinear coupling among the electrostatics, channel geometry, and non-Newtonian hydrodynamics. Furthermore, a method for enhancement of EOFs of power-law fluids is proposed under a combined DC and AC electric field. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Mixing of non-Newtonian fluids in wavy serpentine microchannel using electrokinetically driven flow.
Cho, Ching-Chang; Chen, Chieh-Li; Chen, Cha'o-Kuang
2012-03-01
A numerical investigation is performed into the mixing performance of electrokinetically driven non-Newtonian fluids in a wavy serpentine microchannel. The flow behavior of the non-Newtonian fluids is described using a power-law model. The simulations examine the effects of the flow behavior index, the wave amplitude, the wavy-wall section length, and the applied electric field strength on the mixing performance. The results show that the volumetric flow rate of shear-thinning fluids is higher than that of shear-thickening fluids, and therefore results in a poorer mixing performance. It is shown that for both types of fluid, the mixing performance can be enhanced by increasing the wave amplitude, extending the length of the wavy-wall section, and reducing the strength of the electric field. Thus, although the mixing efficiency of shear-thinning fluids is lower than that of shear-thickening fluids, the mixing performance can be improved through an appropriate specification of the flow and geometry parameters. For example, given a shear-thinning fluid with a flow behavior index of 0.8, a mixing efficiency of 87% can be obtained by specifying the wave amplitude as 0.7, the wavy-wall section length as five times the characteristic length, the nondimensional Debye-Huckel parameter as 100, and the applied electric field strength as 43.5 V/cm. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Direct numerical simulations for non-Newtonian rheology of concentrated particle dispersions.
Iwashita, Takuya; Yamamoto, Ryoichi
2009-12-01
The non-Newtonian behavior of a monodisperse concentrated dispersion of spherical particles was investigated using a direct numerical simulation method, which takes into account hydrodynamic interactions and thermal fluctuations accurately. Simulations were performed under steady shear flow with periodic boundary conditions in the three directions. The apparent shear viscosity of the dispersions was calculated at volume fractions ranging from 0.31 to 0.56. Shear-thinning behavior was clearly observed at high volume fractions. The low- and high-limiting viscosities were then estimated from the apparent viscosity by fitting these data into a semiempirical formula. Furthermore, the short-time motions were examined for Brownian particles fluctuating in concentrated dispersions, for which the fluid inertia plays an important role. The mean square displacement was monitored in the vorticity direction at several different Peclet numbers and volume fractions so that the particle diffusion coefficient is determined from the long-time behavior of the mean square displacement. Finally, the relationship between the non-Newtonian viscosity of the dispersions and the structural relaxation of the dispersed Brownian particles is examined.
Experimental Investigation and Pore-Scale Modeling of Non-Newtonian Fluid Flow in Porous Media
NASA Astrophysics Data System (ADS)
Hauswirth, S.; Dye, A. L.; Miller, C. T.; Tapscott, C.; Schultz, P. B.
2015-12-01
Systems involving the flow of non-Newtonian fluids in porous media arise in a number of settings, including hydraulic fracturing, enhanced oil recovery, contaminant remediation, and biological systems. Development of accurate macroscale models of such systems requires an understanding of the relationship between the fluid and medium properties at the microscale and averaged macroscale properties. This study investigates the flow of aqueous solutions of guar gum, a major component of hydraulic fracturing fluids that exhibits Cross model rheological behavior. The rheological properties of solutions containing varying concentrations of guar gum were characterized using a rotational rheometer and the data were fit to a model relating viscosity to shear rate and concentration. Flow experiments were conducted in a porous medium-packed column to measure the pressure response during the flow of guar gum solutions at a wide range of flow rates and determine apparent macroscale viscosities and shear rates. To investigate the relationship between the fluid rheology, microscale physics, and the observed macroscale properties, a lattice Boltzmann pore scale simulator incorporating non-Newtonian behavior was developed. The model was validated, then used to simulate systems representative of the column experiments, allowing direct correlation of detailed microscale physics to the macroscale observations.
Study on local resistance of non-Newtonian power law fluid in elbow pipes
NASA Astrophysics Data System (ADS)
Zhang, Hao; Xu, Tiantian; Zhang, Xinxin; Wang, Yuxiang; Wang, Yuancheng; Liu, Xueting
2016-06-01
This paper focuses on the flow characteristic and local resistance of non-Newtonian power law fluid in a curved 90° bend pipe with circular cross-sections, which are widely used in industrial applications. By employing numerical simulation and theoretical analysis the properties of the flow and local resistance of power law fluid under different working conditions are obtained. To explore the change rule the experiment is carried out by changing the Reynolds number, the wall roughness and different diameter ratio of elbow pipe. The variation of the local resistance coefficient with the Reynolds number, the diameter ratio and the wall roughness is presented comprehensively in the paper. The results show that the local resistance force coefficient hardly changes with Reynolds number of the power law fluid; the wall roughness has a significant impact on the local resistance coefficient. As the pipe wall roughness increasing, the coefficient of local resistance force will increase. The main reason of the influence of the roughness on the local resistance coefficient is the increase of the eddy current region in the power law fluid flow, which increases the kinetic energy dissipation of the main flow. This paper provides theoretical and numerical methods to understand the local resistance property of non-Newtonian power law fluid in elbow pipes.
Performance Characteristics of Two-Lobe Bearings Operating with Non-Newtonian Lubricants
NASA Astrophysics Data System (ADS)
Koravadi, Jagannath; Raghunandana, Kurkal; Chincholkar, Avinash Manohar
This study presents a steady state and transient solution for a finite width two-lobe bearing operating with a non-Newtonian lubricant, obeying the power law model. A non-linear time-transient analysis is carried out and the orbital stability of journal is ensured by solving the equation of motion by fourth order Runge-Kutta method. Using the expressions for eccentricity ratio of lower and upper lobes and film thickness for each lobe, the modified Reynolds equation is solved separately for each lobe by finite difference technique with a successive over-relaxation scheme. Performance parameters of two-lobe bearing like load carrying capacity, Sommerfeld number, attitude angle; flow and friction parameter are determined and compared with the established results for Newtonian lubricants. Stability parameters are compared with circular bearings. It is found that the non-Newtonian effects are very prominent in the determination of load capacity, flow and friction characteristics of two-lobe bearings. Stability parameters of two-lobe bearings are considerably higher for all eccentricity ratios compared to circular bearings; hence these bearings are better suited for applications where whirl instability limits the speed at which the bearing can be operated.
Gijsen, F J; Allanic, E; van de Vosse, F N; Janssen, J D
1999-07-01
A numerical and experimental investigation of unsteady entry flow in a 90 degrees curved tube is presented to study the impact of the non-Newtonian properties of blood on the velocity distribution. The time-dependent flow rate for the Newtonian and the non-Newtonian blood analog fluid were identical. For the numerical computation, a Carreau-Yasuda model was employed to accommodate the shear thinning behavior of the Xanthan gum solution. The viscoelastic properties were not taken into account. The experimental results indicate that significant differences between the Newtonian and non-Newtonian fluid are present. The numerical results for both the Newtonian and the non-Newtonian fluid agree well with the experimental results. Since viscoelasticity was not included in the numerical code, shear thinning behavior of the blood analog fluid seems to be the dominant non-Newtonian property, even under unsteady flow conditions. Finally, a comparison between the non-Newtonian fluid model and a Newtonian fluid at a rescaled Reynolds number is presented. The rescaled Reynolds number, based on a characteristic rather than the high-shear rate viscosity of the Xanthan gum solution, was about three times as low as the original Reynolds number. Comparison reveals that the character of flow of the non-Newtonian fluid is simulated quite well by using the appropriate Reynolds number.
NASA Astrophysics Data System (ADS)
Akbari, Omid Ali; Toghraie, Davood; Karimipour, Arash; Marzban, Ali; Ahmadi, Gholam Reza
2017-02-01
In this investigation, the behavior of non-Newtonian nanofluid hydrodynamic and heat transfer are simulated. In this study, we numerically simulated a laminar forced non-Newtonian nanofluid flow containing a 0.5 wt% carboxy methyl cellulose (CMC) solutionin water as the base fluid with alumina at volume fractions of 0.5 and 1.5 as the solid nanoparticle. Numerical solution was modelled in Cartesian coordinate system in a two-dimensional microchannel in Reynolds number range of 10≤Re≤1000. The analyzed geometrical space here was a rectangular part of whose upper and bottom walls was influenced by a constant temperature. The effect of volume fraction of the nanoparticles, Reynolds number and non-Newtonian nanofluids was studied. In this research, the changes pressure drop, the Nusselt number, dimensionless temperature and heat transfer coefficient, caused by the motion of non-Newtonian nanofluids are described. The results indicated that the increase of the volume fraction of the solid nanoparticles and a reduction in the diameter of the nanoparticles would improve heat transfer which is more significant in Reynolds number. The results of the introduced parameters in the form of graphs drawing and for different parameters are compared.
On the rheology of refractive-index-matched, non-Newtonian blood-analog fluids for PIV experiments
NASA Astrophysics Data System (ADS)
Najjari, Mohammad Reza; Hinke, Jessica A.; Bulusu, Kartik V.; Plesniak, Michael W.
2016-06-01
Four commonly used refractive-index (RI)-matched Newtonian blood-analog fluids are reviewed, and different non-Newtonian blood-analogs, with RI of 1.372-1.495, are investigated. Sodium iodide (NaI), sodium thiocyanate (NaSCN) and potassium thiocyanate are used to adjust the RI of blood-analogs to that of test sections for minimizing optical distortions in particle image velocimetry data, and xanthan gum (XG) is added to the fluids to give them non-Newtonian properties (shear thinning and viscoelasticity). Our results support the general belief that adding NaI to Newtonian fluids matches the RI without changing the kinematic viscosity. However, in contrast to claims made in a few studies that did not measure rheology, our investigation revealed that adding NaI or NaSCN to XG-based non-Newtonian fluids changes the viscosity of the fluids considerably and reduces the shear-thinning property. Therefore, the RI of non-Newtonian blood-analog fluids with XG cannot be adjusted easily by varying the concentration of NaI or NaSCN and needs more careful rheological study.
Sun, Kai; Wang, Tianyou; Zhang, Peng; Law, Chung K
2015-02-01
The coalescence of two initially stationary droplets of shear-thinning fluids in a gaseous environment is investigated numerically using the lattice Boltzmann method, with particular interest in non-Newtonian flow effects on the internal mixing subsequent to coalescence. Coalescence of equal-sized droplets, with one being Newtonian while the other is non-Newtonian, leads to the non-Newtonian droplet wrapping around the Newtonian one and hence minimal fine-scale mixing. For unequal-sized droplets, mixing is greatly promoted if both droplets are shear-thinning. When only one of the droplets is shear-thinning, the non-Newtonian effect from the smaller droplet is found to be significantly more effective than that from the larger droplet in facilitating internal jetlike mixing. Parametric study with the Carreau-Yasuda model indicates that the phenomena are universal to a wide range of shear-thinning fluids, given that the extent of shear thinning reaches a certain level, and the internal jet tends to be thicker and develops more rapidly with increasing extent of the shear-thinning effect.
NASA Astrophysics Data System (ADS)
Marrero, Victor; Sahni, Onkar; Jansen, Kenneth; Tichy, John; Taylor, Charles
2008-11-01
In recent years the methods of computational fluid dynamics (CFD) have been applied to the human cardiovascular system to better understand the relationship between arterial blood flow and the disease process, for example in an abdominal aortic aneurysm (AAA). Obviously, the technical challenges associated with such modeling are formidable. Among the many problems to be addressed, in this paper we add yet another complication -- the known non-Newtonian nature of blood. In this preliminary study, we used a patient-based AAA model with rigid walls. The pulsatile nature of the flow and the RCR outflow boundary condition are considered. We use the Carreau-Yasuda model to describe the non-Newtonian viscosity variation. Preliminary results for 200K, 2M, and 8M elements mesh are presented for the Newtonian and non-Newtonian cases. The broad fundamental issue we wish to eventually resolve is whether or not non-Newtonian effects in blood flow are sufficiently strong in unhealthy vessels that they must be addressed in meaningful simulations. Interesting differences during the flow cycle shed light on the problem, but further research is needed.
NASA Astrophysics Data System (ADS)
Miklosovic, David Scott
Significant work has been done in the last 10 years to advance the technology of long-term mechanical circulatory assistance, particularly the left ventricular assist device (LVAD). Traditionally, rotary LVADs have been developed using conventional fluid dynamic design methods and Newtonian scaling laws, since non-Newtonian effects were previously assumed to be of second-order importance. To evaluate centrifugal pump performance scaling and flow patterns in a non-Newtonian fluid, the Large-Scale Rotor Testbed (LSRT) at The Ohio State University was developed to test two 9X-scale blood pump impellers in a baseline volute housing of the Innovative Ventricular Assist System (IVAS) designed by the Cleveland Clinic Foundation. Non-Newtonian fluids yielded pump performance deficits of first-order importance, or up to 11% of the Newtonian performance. Thus, the non-Newtonian effects were of the same magnitude as substantial variations in the impeller geometry. Moreover, the dimensionless pressure- and flow-coefficients showed that the non-Newtonian performance deviated from the similarity laws at critical Reynolds numbers that were 2.4--2.7 times higher than the Newtonian value of 71,000. Above the critical Reynolds number, the non-Newtonian fluids followed a similarity behavior, but it was different from the Newtonian case. The deviation increased with the magnitude of shear-thinning behavior as measured by the Weissenberg number. Shear-thinning xanthan gum solutions were used as non-Newtonian test fluids in concentrations from 0 to 1,200 ppm. Fluid samples were characterized in a Couette rheometer to determine viscosity behavior, biological degradation, and shear-induced polymer chain breakdown. The solutions proved to be stable and useful for a duration of up to two weeks of routine LSRT testing. Because the LSRT pump operates in a low-specific speed, low-flow regime, flow visualizations revealed a strong adverse pressure gradient and a prominent inverse Ekman layer in
Hippelheuser, James E; Lauric, Alexandra; Cohen, Alex D; Malek, Adel M
2014-11-28
Most computational fluid dynamic (CFD) simulations of aneurysm hemodynamics assume constant (Newtonian) viscosity, even though blood demonstrates shear-thinning (non-Newtonian) behavior. We sought to evaluate the effect of this simplifying assumption on hemodynamic forces within cerebral aneurysms, especially in regions of low wall shear stress, which are associated with rupture. CFD analysis was performed for both viscosity models using 3D rotational angiography volumes obtained for 26 sidewall aneurysms (12 with blebs, 12 ruptured), and parametric models incorporating blebs at different locations (inflow/outflow zone). Mean and lowest 5% values of time averaged wall shear stress (TAWSS) computed over the dome were compared using Wilcoxon rank-sum test. Newtonian modeling not only resulted in higher aneurysmal TAWSS, specifically in areas of low flow and blebs, but also showed no difference between aneurysms with or without blebs. In contrast, for non-Newtonian analysis, bleb-bearing aneurysms showed significantly lower 5% TAWSS compared to those without (p=0.005), despite no significant difference in mean dome TAWSS (p=0.32). Non-Newtonian modeling also accentuated the differences in dome TAWSS between ruptured and unruptured aneurysms (p<0.001). Parametric models further confirmed that realistic non-Newtonian viscosity resulted in lower bleb TAWSS and higher focal viscosity, especially when located in the outflow zone. The results show that adopting shear-thinning non-Newtonian blood viscosity in CFD simulations of intracranial aneurysms uncovered hemodynamic differences induced by bleb presence on aneurysmal surfaces, and significantly improved discriminant statistics used in risk stratification. These findings underline the possible implications of using a realistic model of blood viscosity in predictive computational hemodynamics.
Sharifi, Alireza; Niazmand, Hamid
2015-10-01
Carotid siphon is known as one of the risky sites among the human intracranial arteries, which is prone to formation of atherosclerotic lesions. Indeed, scientists believe that accumulation of low density lipoprotein (LDL) inside the lumen is the major cause of atherosclerosis. To this aim, three types of internal carotid artery (ICA) siphon have been constructed to examine variations of hemodynamic parameters in different regions of the arteries. Providing real physiological conditions, blood considered as non-Newtonian fluid and real velocity and pressure waveforms have been employed as flow boundary conditions. Moreover, to have a better estimation of risky sites, the accumulation of LDL particles has been considered, which has been usually ignored in previous relevant studies. Governing equations have been discretized and solved via open source OpenFOAM software. A new solver has been built to meet essential parameters related to the flow and mass transfer phenomena. In contrast to the common belief regarding negligible effect of blood non-Newtonian behavior inside large arteries, current study suggests that the non-Newtonian blood behavior is notable, especially on the velocity field of the U-type model. In addition, it is concluded that neglecting non-Newtonian effects underestimates the LDL accumulation up to 3% in the U-type model at the inner side of both its bends. However, in the V and C type models, non-Newtonian effects become relatively small. Results also emphasize that the outer part of the second bend at the downstream is also at risk similar to the inner part of the carotid bends. Furthermore, from findings it can be implied that the risky sites strongly depend on the ICA shape since the extension of the risky sites are relatively larger for the V-type model, while the LDL concentrations are higher for the C-type model.
Propagation of Gravity Currents of non-Newtonian Power-Law Fluids in Porous Media
NASA Astrophysics Data System (ADS)
Di Federico, V.; Longo, S.; Ciriello, V.; Chiapponi, L.
2014-12-01
A comprehensive analytical and experimental framework is presented to describe gravity-driven motions of rheologically complex fluids through porous media. These phenomena are relevant in geophysical, environmental, industrial and biological applications. The fluid is characterized by an Ostwald-DeWaele constitutive equation with behaviour index n. The flow is driven by the release of fluid at the origin of an infinite porous domain. In order to represent several possible spreading scenarios, we consider: i) different domain geometries: plane, radial, and channelized, with the channel shape parameterized by k; ii) instantaneous or continuous injection, depending on the time exponent of the volume of fluid in the current, α; iii) horizontal or inclined impermeable boundaries. Systematic heterogeneity along the streamwise and/or transverse direction is added to the conceptualization upon considering a power-law permeability variation governed by two additional parameters ω and β. Scalings for current length and thickness are derived in self similar form coupling the modified Darcy's law accounting for the fluid rheology with the mass balance equation. The length, thickness, and aspect ratio of the current are studied as functions of model parameters; several different critical values of α emerge and govern the type of dependency, as well as the tendency of the current to accelerate or decelerate and become thicker or thinner at a given point. The asymptotic validity of the solutions is limited to certain ranges of model parameters. Experimental validation is performed under constant volume, constant and variable flux regimes in tanks/channels filled with transparent glass beads of uniform or variable diameter, using shear-thinning suspensions and Newtonian mixtures. The experimental results for the length and profile of the current agree well with the self-similar solutions at intermediate and late times.
Viscoelastic Flows in Simple Liquids Generated by Vibrating Nanostructures
NASA Astrophysics Data System (ADS)
Sader, John; Pelton, Matthew; Chakraborty, Debadi; Malachosky, Edward; Guyot-Sionnest, Philippe
2014-11-01
Newtonian fluid mechanics, in which the shear stress is proportional to the strain rate, is synonymous with the flow of simple liquids like water. We report the measurement and theoretical verification of non-Newtonian, viscoelastic flow phenomena produced by the high-frequency (>20 GHz) vibration of gold nanoparticles immersed in water-glycerol mixtures. The observed viscoelasticity is not due to molecular confinement, but is a bulk continuum effect arising from the short time scale of vibration. This represents the first direct mechanical measurement of the intrinsic viscoelastic properties of simple bulk liquids, and opens a new paradigm for understanding extremely high frequency fluid mechanics, nanoscale sensing technologies, and biophysical processes.
NASA Technical Reports Server (NTRS)
DiSalvo, Roberto; Deaconu, Stelu; Majumdar, Alok
2006-01-01
One of the goals of this program was to develop the experimental and analytical/computational tools required to predict the flow of non-Newtonian fluids through the various system components of a propulsion system: pipes, valves, pumps etc. To achieve this goal we selected to augment the capabilities of NASA's Generalized Fluid System Simulation Program (GFSSP) software. GFSSP is a general-purpose computer program designed to calculate steady state and transient pressure and flow distributions in a complex fluid network. While the current version of the GFSSP code is able to handle various systems components the implicit assumption in the code is that the fluids in the system are Newtonian. To extend the capability of the code to non-Newtonian fluids, such as silica gelled fuels and oxidizers, modifications to the momentum equations of the code have been performed. We have successfully implemented in GFSSP flow equations for fluids with power law behavior. The implementation of the power law fluid behavior into the GFSSP code depends on knowledge of the two fluid coefficients, n and K. The determination of these parameters for the silica gels used in this program was performed experimentally. The n and K parameters for silica water gels were determined experimentally at CFDRC's Special Projects Laboratory, with a constant shear rate capillary viscometer. Batches of 8:1 (by weight) water-silica gel were mixed using CFDRC s 10-gallon gelled propellant mixer. Prior to testing the gel was allowed to rest in the rheometer tank for at least twelve hours to ensure that the delicate structure of the gel had sufficient time to reform. During the tests silica gel was pressure fed and discharged through stainless steel pipes ranging from 1", to 36", in length and three diameters; 0.0237", 0.032", and 0.047". The data collected in these tests included pressure at tube entrance and volumetric flowrate. From these data the uncorrected shear rate, shear stress, residence time
Enderlin, Carl W.; Bontha, Jagannadha R.; Bamberger, Judith A.; Nigl, Franz
2011-01-01
Pulse jet mixing systems are being developed for use in the Waste Treatment Plant in Washington State. To assist with system development, scaled tests were conducted to obtain experimental measurements of the cloud height for Newtonian slurries and cavern heights for a Non-Newtonian yield stress material. The measurements were required to assess the effective mixing and material mobilization produced during pulse jet mixer operation. The cloud height measurements were obtained for a single steady-state jet directed downward in a spherical-bottom tank. The cloud tests used glass beads in water to evaluate the height of the suspended slurry as a function of jet velocity. Cloud testing revealed that the glass bead material was suspended in the tank quickly and developed a distinctive height for each combination of flow rate and particulate size tested. The solids loading had minimal impact on the cloud height for a given particle size. During all cloud tests, the surface of the tank remained relatively calm, indicating that the slurry was dissipating the mixing energy of the relatively high velocity jet. Cavern tests were conducted to obtain experimental data of non-Newtonian fluid mixing for fluid properties similar to those of certain tank wastes. A transparent material that exhibited a yield stress and shear thinning behavior was used to obtain measurements of steady-state cavern heights as a function of jet velocity. For the non-Newtonian fluid cavern tests, distinct cavern volumes were readily developed for the four velocities tested. A linear relationship was observed to exist between cavern height and nozzle velocity. Since the experimental work detailed in this paper was completed, additional scaled tests have been conducted with pneumatic drive systems and direct drive systems similar to that described for this effort. Data from both types of measurements are shown to be linear; however, effects from the reciprocating drive systems that are not yet
Viscosity and non-Newtonian features of thickened fluids used for dysphagia therapy.
O'Leary, Mark; Hanson, Ben; Smith, Christina
2010-08-01
Thickening agents based primarily on granulated maize starch are widely used in the care of patients with swallowing difficulties, increasing viscosity of consumed fluids. This slows bolus flow during swallowing, allowing airway protection to be more properly engaged. Thickened fluids have been shown to exhibit time-varying behavior and are non-Newtonian, complicating assessment of fluid thickness, potentially compromising efficacy of therapy. This work aimed to quantify the flow properties of fluids produced with commercial thickeners at shear rates representative of slow tipping in a beaker to fast swallowing. Results were presented as indices calculated using a power-law model representing apparent viscosity (consistency index) and non-Newtonian nature of flow (flow behavior index). Immediately following mixing, 3 fluid thicknesses showed distinct consistency indices and decreasing flow behavior index with increasing thickener concentration. An increase in consistency index over 30 min was observed, but only for samples that were repeatedly sheared during acquisition. Three-hour measurements showed changes in consistency index across fluids with the largest being a 25% rise from initial value. This may have implications for efficacy of treatment, as fluids are not always consumed immediately upon mixing. Flow behavior indices were comparable across thickeners exhibiting similar rises over time. The indices were a more complete method of quantifying flow properties compared with single viscosity measurements, allowing an increased depth of analysis. The non-Newtonian nature of fluids perhaps renders them particularly suitable for use as dysphagia therapies, and such analysis may allow the possibility of altering these properties to optimize therapeutic efficacy to be explored. Practical Application: Effective treatment of swallowing disorders relies upon the appropriate choice and subsequent reproduction of drinks thickened to one of a number of predetermined
Force effects on rotor of squeeze film damper using Newtonian and non-Newtonian fluid
NASA Astrophysics Data System (ADS)
Dominik, Šedivý; Petr, Ferfecki; Simona, Fialová
2017-09-01
This article presents the evaluation of force effects on rotor of squeeze film damper. Rotor is eccentric placed and its motion is translate-circular. The amplitude of rotor motion is smaller than its initial eccentricity. The force effects are calculated from pressure and viscous forces which were gained by using computational modeling. Two types of fluid were considered as filling of damper. First type of fluid is Newtonian (has constant viscosity) and second type is magnetorheological fluid (does not have constant viscosity). Viscosity of non-Newtonian fluid is given using Bingham rheology model. Yield stress is a function of magnetic induction which is described by many variables. The most important variables of magnetic induction are electric current and gap width which is between rotor and stator. Comparison of application two given types of fluids is shown in results.
Non-Newtonian Characteristics of Gochujang and Chogochujang at Different Temperatures
Choi, Ji Eun; Lee, Jun Ho
2017-01-01
This study was conducted to determine the rheological properties of gochujang and chogochujang at different temperatures (25, 35, and 45°C). Rheological properties of the samples were determined using a rotational rheometer at a shear range of 1 to 40 s−1. Gochujang and chogochujang were found to be non-Newtonian fluids according to the Herschel-Bulkley model. Yield stress and consistency coefficient of gochujang at different temperatures were higher than those of chogochujang, whereas the opposite was observed for flow behavior index. Moreover, all rheological properties of gochujang and chogochujang decreased with increasing temperature. The consistency coefficient was related to temperature using an Arrhenius-type relationship. Gochujang (14.48 kJ/mol) had slightly higher activation energy than chogochujang (14.03 kJ/mol). PMID:28401090
Magnetohydrodynamic third-grade non-Newtonian nanofluid flow through a porous coaxial cylinder
NASA Astrophysics Data System (ADS)
Sadikin, Zubaidah; Kechil, Seripah Awang
2015-10-01
The convective flow of third grade non-Newtonian nanofluid through porous coaxial cylinders with inclined magnetic field is investigated. The governing partial differential equations are transformed to a system of nonlinear ordinary differential equations using the non-dimensional quantities. The transformed system of nonlinear ordinary differential equations is solved numerically using the fourth-order Runge-Kutta method. The viscosity of the nanofluid is considered as a function of temperature in form of Vogel's model. Numerical solutions are obtained for the velocity, temperature and nanoparticles concentration. The effects of the some physical parameters particularly the angle of inclination, the magnetic, Brownian motion and thermophoresis parameters on non-dimensional velocity, temperature and nanoparticles concentration are analyzed. It is found that as the angle of inclination of magnetic field increases, the velocity decreases. The results also show that increasing the thermophoresis parameter and Brownian motion, the temperature increases. By increasing the Brownian motion or decreasing the thermophoresis parameter, nanoparticles concentration increases.
Rheological non-Newtonian behaviour of ethylene glycol-based Fe2O3 nanofluids
2011-01-01
The rheological behaviour of ethylene glycol-based nanofluids containing hexagonal scalenohedral-shaped α-Fe2O3 (hematite) nanoparticles at 303.15 K and particle weight concentrations up to 25% has been carried out using a cone-plate Physica MCR rheometer. The tests performed show that the studied nanofluids present non-Newtonian shear-thinning behaviour. In addition, the viscosity at a given shear rate is time dependent, i.e. the fluid is thixotropic. Finally, using strain sweep and frequency sweep tests, the storage modulus G', loss modulus G″ and damping factor were determined as a function of the frequency showing viscoelastic behaviour for all samples. PMID:22027018
Matrix Transformations between Certain Sequence Spaces over the Non-Newtonian Complex Field
Efe, Hakan
2014-01-01
In some cases, the most general linear operator between two sequence spaces is given by an infinite matrix. So the theory of matrix transformations has always been of great interest in the study of sequence spaces. In the present paper, we introduce the matrix transformations in sequence spaces over the field ℂ* and characterize some classes of infinite matrices with respect to the non-Newtonian calculus. Also we give the necessary and sufficient conditions on an infinite matrix transforming one of the classical sets over ℂ* to another one. Furthermore, the concept for sequence-to-sequence and series-to-series methods of summability is given with some illustrated examples. PMID:25110740
Test of non-Newtonian gravitational forces at micrometer range with two-dimensional force mapping
NASA Astrophysics Data System (ADS)
Wang, Jianbo; Guan, Shengguo; Chen, Kai; Wu, Wenjie; Tian, Zhaoyang; Luo, Pengshun; Jin, Aizi; Yang, Shanqing; Shao, Chenggang; Luo, Jun
2016-12-01
We report an isoelectronic test of non-Newtonian forces at micrometer range by sensing the lateral force between a gold sphere and a density modulation source mass using a soft cantilever. Two-dimensional (2D) force mapping, in combination with in situ topographic imaging, is applied to verify the isoelectronic property of the surface. The force signal is found to be electrostatic force dominated, which is correlated with the density modulation structure for thinner gold coating and reduced by thicker gold coating and thermal annealing. Maximum likelihood estimation is used to extract the constraint on the hypothetical force based on the 2D data, and the experiment sets a constraint on the Yukawa type forces without subtraction of the model dependent force background. This result would be a meaningful complementary to previous tests with different methods.
Motion of a Non-Newtonian Fluid in the Wake of a Flat Plate
NASA Astrophysics Data System (ADS)
Zhou, Min; Ladeinde, Foluso; Bluestein, Danny
2004-11-01
A theoretical analysis of two-dimensional steady state laminar flow of a non-Newtonian fluid in the wake of a flat plate is presented. This is a simplified model for blood flow over the bi-leaflet of a mechanical heart valve. The present analysis is also intended to validate large eddy simulations, which are currently being carried out for a more elaborate model of the heart valve. By introducing the power-law model, the Goldstein's near wake solution and Tollmien's first asymptotic approximation in the far wake are extended for applicability to blood flow. On the symmetry line, two velocity distributions are obtained as functions of the distance behind the plate, one from the near wake and the other from the far wake. These are matched to form a continuous distribution. For the other regions, the velocity distribution could be determined by interpolation. The results are contrasted with previous work on Newtonian fluids.
Exact Solutions for Stokes' Flow of a Non-Newtonian Nanofluid Model: A Lie Similarity Approach
NASA Astrophysics Data System (ADS)
Aziz, Taha; Aziz, A.; Khalique, C. M.
2016-07-01
The fully developed time-dependent flow of an incompressible, thermodynamically compatible non-Newtonian third-grade nanofluid is investigated. The classical Stokes model is considered in which the flow is generated due to the motion of the plate in its own plane with an impulsive velocity. The Lie symmetry approach is utilised to convert the governing nonlinear partial differential equation into different linear and nonlinear ordinary differential equations. The reduced ordinary differential equations are then solved by using the compatibility and generalised group method. Exact solutions for the model equation are deduced in the form of closed-form exponential functions which are not available in the literature before. In addition, we also derived the conservation laws associated with the governing model. Finally, the physical features of the pertinent parameters are discussed in detail through several graphs.
NASA Astrophysics Data System (ADS)
Zaman, Akbar; Ali, Nasir; Sajid, M.
2016-01-01
Slip effects on unsteady non-Newtonian blood hydro-magnetic flow through an inclined catheterized overlapping stenotic artery are analyzed. The constitutive equation of power law model is employed to simulate the rheological characteristics of the blood. The governing equations giving the flow derived by assuming the flow to be unsteady and two-dimensional. Mild stenosis approximation is employed to obtain the reduced form of the governing equations. Finite difference method is employed to obtain the solution of the non-linear partial differential equation in the presence of slip at the surface. An extensive quantitative analysis is performed for the effects of slip parameter, Hartmann number, cathetered parameter and arterial geometrical parameters of stenosis on the quantities of interest such as axial velocity, flow rate, resistance impedance and wall shear stress. The streamlines for the blood flow through the artery are also included.
Calculation of the Pitot tube correction factor for Newtonian and non-Newtonian fluids.
Etemad, S Gh; Thibault, J; Hashemabadi, S H
2003-10-01
This paper presents the numerical investigation performed to calculate the correction factor for Pitot tubes. The purely viscous non-Newtonian fluids with the power-law model constitutive equation were considered. It was shown that the power-law index, the Reynolds number, and the distance between the impact and static tubes have a major influence on the Pitot tube correction factor. The problem was solved for a wide range of these parameters. It was shown that employing Bernoulli's equation could lead to large errors, which depend on the magnitude of the kinetic energy and energy friction loss terms. A neural network model was used to correlate the correction factor of a Pitot tube as a function of these three parameters. This correlation is valid for most Newtonian, pseudoplastic, and dilatant fluids at low Reynolds number.
Non-Newtonian Characteristics of Gochujang and Chogochujang at Different Temperatures.
Choi, Ji Eun; Lee, Jun Ho
2017-03-01
This study was conducted to determine the rheological properties of gochujang and chogochujang at different temperatures (25, 35, and 45°C). Rheological properties of the samples were determined using a rotational rheometer at a shear range of 1 to 40 s(-1). Gochujang and chogochujang were found to be non-Newtonian fluids according to the Herschel-Bulkley model. Yield stress and consistency coefficient of gochujang at different temperatures were higher than those of chogochujang, whereas the opposite was observed for flow behavior index. Moreover, all rheological properties of gochujang and chogochujang decreased with increasing temperature. The consistency coefficient was related to temperature using an Arrhenius-type relationship. Gochujang (14.48 kJ/mol) had slightly higher activation energy than chogochujang (14.03 kJ/mol).
Lattice Boltzmann method for non-Newtonian (power-law) fluids.
Gabbanelli, Susana; Drazer, German; Koplik, Joel
2005-10-01
We study an ad hoc extension of the lattice Boltzmann method that allows the simulation of non-Newtonian fluids described by generalized Newtonian models. We extensively test the accuracy of the method for the case of shear-thinning and shear-thickening truncated power-law fluids in the parallel plate geometry, and show that the relative error compared to analytical solutions decays approximately linear with the lattice resolution. Finally, we also tested the method in the reentrant-flow geometry, in which the shear rate is no longer a scalar and the presence of two singular points requires high accuracy in order to obtain satisfactory resolution in the local stress near these points. In this geometry, we also found excellent agreement with the solutions obtained by standard finite-element methods, and the agreement improves with higher lattice resolution.
Frogs use a viscoelastic tongue and non-Newtonian saliva to catch prey.
Noel, Alexis C; Guo, Hao-Yuan; Mandica, Mark; Hu, David L
2017-02-01
Frogs can capture insects, mice and even birds using only their tongue, with a speed and versatility unmatched in the world of synthetic materials. How can the frog tongue be so sticky? In this combined experimental and theoretical study, we perform a series of high-speed films, material tests on the tongue, and rheological tests of the frog saliva. We show that the tongue's unique stickiness results from a combination of a soft, viscoelastic tongue coupled with non-Newtonian saliva. The tongue acts like a car's shock absorber during insect capture, absorbing energy and so preventing separation from the insect. The shear-thinning saliva spreads over the insect during impact, grips it firmly during tongue retraction, and slides off during swallowing. This combination of properties gives the tongue 50 times greater work of adhesion than known synthetic polymer materials such as the sticky-hand toy. These principles may inspire the design of reversible adhesives for high-speed application.
Generalized multiscale finite element method for non-Newtonian fluid flow in perforated domain
NASA Astrophysics Data System (ADS)
Chung, E. T.; Iliev, O.; Vasilyeva, M. V.
2016-10-01
In this work, we consider a non-Newtonian fluid flow in perforated domains. Fluid flow in perforated domains have a multiscale nature and solution techniques for such problems require high resolution. In particular, the discretization needs to honor the irregular boundaries of perforations. This gives rise to a fine-scale problems with many degrees of freedom which can be very expensive to solve. In this work, we develop a multiscale approach that attempt to solve such problems on a coarse grid by constructing multiscale basis functions. We follow Generalized Multiscale Finite Element Method (GMsFEM) [1, 2] and develop a multiscale procedure where we identify multiscale basis functions in each coarse block using snapshot space and local spectral problems [3, 4]. We show that with a few basis functions in each coarse block, one can accurately approximate the solution, where each coarse block can contain many small inclusions.
Mathematical simulation of nonisothermal filling of plane channel with non-Newtonian fluid
NASA Astrophysics Data System (ADS)
Borzenko, E.; Ryltseva, K.; Frolov, O.; Shrager, G.
2016-10-01
In this paper, the fountain flow of a non-Newtonian fluid during the filling of a plane vertical channel with due account of dissipative heating is investigated. The rheological features of the medium are defined by Ostwald de Waele power-law with exponential temperature dependence of viscosity. The numerical solution of the problem is obtained using a finite-difference method, based on the SIMPLE algorithm, and the method of invariants for compliance with the natural boundary conditions on free surface. It was shown that the flow separates into a two-dimensional flow zone in the vicinity of the free surface and a onedimensional flow zone away from it. The parametrical investigations of kinematic and thermophysical properties of the flow and the dependence of the free surface behavior on the basic criteria and rheological parameters are implemented.
Acoustic waveform of continuous bubbling in a non-Newtonian fluid.
Vidal, Valérie; Ichihara, Mie; Ripepe, Maurizio; Kurita, Kei
2009-12-01
We study experimentally the acoustic signal associated with a continuous bubble bursting at the free surface of a non-Newtonian fluid. Due to the fluid rheological properties, the bubble shape is elongated, and, when bursting at the free surface, acts as a resonator. For a given fluid concentration, at constant flow rate, repetitive bubble bursting occurs at the surface. We report a modulation pattern of the acoustic waveform through time. Moreover, we point out the existence of a precursor acoustic signal, recorded on the microphone array, previous to each bursting. The time delay between this precursor and the bursting signal is well correlated with the bursting signal frequency content. Their joint modulation through time is driven by the fluid rheology, which strongly depends on the presence of small satellite bubbles trapped in the fluid due to the yield stress.
Non-newtonian fluid flow through three-dimensional disordered porous media.
Morais, Apiano F; Seybold, Hansjoerg; Herrmann, Hans J; Andrade, José S
2009-11-06
We investigate the flow of various non-newtonian fluids through three-dimensional disordered porous media by direct numerical simulation of momentum transport and continuity equations. Remarkably, our results for power-law (PL) fluids indicate that the flow, when quantified in terms of a properly modified permeability-like index and Reynolds number, can be successfully described by a single (universal) curve over a broad range of Reynolds conditions and power-law exponents. We also study the flow behavior of Bingham fluids described in terms of the Herschel-Bulkley model. In this case, our simulations reveal that the interplay of (i) the disordered geometry of the pore space, (ii) the fluid rheological properties, and (iii) the inertial effects on the flow is responsible for a substantial enhancement of the macroscopic hydraulic conductance of the system at intermediate Reynolds conditions.
A modified model for non-newtonian viscosity behavior of Aureobasidium pullulans culture fluid.
Furuse, Hisamoto; Yabe, Isamu; Asakura, Tomoko; Miyawaki, Osato; Toda, Kiyoshi
2003-01-01
The culture fluid of the fungus Aureobasidium pullulans and the exopolysaccharide solution obtained by removal of the microbial cells exhibit a marked shear dependence of viscosity. The viscosity in a high shear rate region was a little higher than that predicted by a non-Newtonian viscosity equation derived previously on the basis of the concept of traveling force. In a sample exhibiting such high shear rate dependence, a hydrodynamic effect based on the fluid structure of the binding of contacting polymers and suspended microbial cells on viscosity becomes comparatively significant. A model for the shear rate dependence of the viscosity is needed to elucidate the mechanism of the viscosity behavior. A term concerning the increase in viscosity caused by the binding of polymers and the microbial cells suspended in a medium was added to the previous viscosity equation. The experimental shear dependence of the viscosity was well simulated by the modified viscosity equation.
Shape optimization in steady blood flow: a numerical study of non-Newtonian effects.
Abraham, Feby; Behr, Marek; Heinkenschloss, Matthias
2005-04-01
We investigate the influence of the fluid constitutive model on the outcome of shape optimization tasks, motivated by optimal design problems in biomedical engineering. Our computations are based on the Navier-Stokes equations generalized to non-Newtonian fluid, with the modified Cross model employed to account for the shear-thinning behavior of blood. The generalized Newtonian treatment exhibits striking differences in the velocity field for smaller shear rates. We apply sensitivity-based optimization procedure to a flow through an idealized arterial graft. For this problem we study the influence of the inflow velocity, and thus the shear rate. Furthermore, we introduce an additional factor in the form of a geometric parameter, and study its effect on the optimal shape obtained.
Shear-induced effects in confined non-Newtonian fluids under tension.
Miranda, José A
2004-01-01
We study the influence of shear effects on the adhesive performance of a non-Newtonian fluid under tension, confined between two parallel flat plates. The upper plate is subjected to a pulling force, which is recorded during the separation process. We approach the problem analytically, and use a modified Darcy's law in the weak shear limit to derive the adhesive force and the separation energy. Our theoretical results demonstrate that, for relatively small separations, the adhesion strength is considerably reduced (enhanced) if the fluid is shear thinning (thickening). For larger plate separations, shear effects become negligible, and usual Newtonian behavior is observed. These findings are confirmed by a numerical solution of a more realistic version of the problem, which considers weak shear effects, plus the intrinsic elasticity of the lifting apparatus.
Non-Newtonian Flow of Blood in Arterioles: Consequences for Wall Shear Stress Measurements
SRIRAM, Krishna; INTAGLIETTA, Marcos; TARTAKOVSKY, Daniel M.
2014-01-01
We model blood in a microvessel as an inhomogeneous non-Newtonian fluid, whose viscosity varies with hematocrit and shear rate in accordance with the Quemada rheological relation. The flow is assumed to consist of two distinct, immiscible and homogeneous fluid layers: an inner region densely packed with red blood cells, and an outer cell-free layer whose thickness depends on discharge hematocrit. We demonstrate that the proposed model provides a realistic description of velocity profiles, tube hematocrit, core hematocrit and apparent viscosities over a wide range of vessel radii and discharge hematocrits. Our analysis reveals the importance of incorporating this complex blood rheology into estimates of wall shear stress in micro-vessels. The latter is accomplished by specifying a correction factor, which accounts for the deviation of blood flow from the Poiseuille law. PMID:24703006
Simulation of a pulsatile non-Newtonian flow past a stenosed 2D artery with atherosclerosis.
Tian, Fang-Bao; Zhu, Luoding; Fok, Pak-Wing; Lu, Xi-Yun
2013-09-01
Atherosclerotic plaque can cause severe stenosis in the artery lumen. Blood flow through a substantially narrowed artery may have different flow characteristics and produce different forces acting on the plaque surface and artery wall. The disturbed flow and force fields in the lumen may have serious implications on vascular endothelial cells, smooth muscle cells, and circulating blood cells. In this work a simplified model is used to simulate a pulsatile non-Newtonian blood flow past a stenosed artery caused by atherosclerotic plaques of different severity. The focus is on a systematic parameter study of the effects of plaque size/geometry, flow Reynolds number, shear-rate dependent viscosity and flow pulsatility on the fluid wall shear stress and its gradient, fluid wall normal stress, and flow shear rate. The computational results obtained from this idealized model may shed light on the flow and force characteristics of more realistic blood flow through an atherosclerotic vessel. Copyright © 2013. Published by Elsevier Ltd.
Walker, Andrew M; Johnston, Clifton R; Rival, David E
2014-01-01
Particle image velocimetry (PIV) was used to investigate the influence of a non-Newtonian blood analog of aqueous xanthan gum on flow separation in laminar and transitional environments and in both steady and pulsatile flow. Initial steady pressure drop measurements in laminar and transitional flow for a Newtonian analog showed an extension of laminar behavior to Reynolds number (Re) ~ 2900 for the non-Newtonian case. On a macroscale level, this showed good agreement with porcine blood. Subsequently, PIV was used to measure flow patterns and turbulent statistics downstream of an axisymmetric stenosis in the aqueous xanthan gum solution and for a Newtonian analog at Re ~ 520 and Re ~ 1250. The recirculation length for the non-Newtonian case was reduced at Re ~ 520 resultant from increased viscosity at low shear strain rates. At Re ~ 1250, peak turbulent intensities and turbulent shear stresses were dampened by the non-Newtonian fluid in close proximity to the blockage outlet. Although the non-Newtonian case's recirculation length was increased at peak pulsatile flow, turbulent shear stress was found to be elevated for the Newtonian case downstream from the blockage, suggesting shear layer fragmentation and radial transport. Our findings conclude that the xanthan gum elastic polymer prolongs flow stabilization, which in turn emphasizes the importance of non-Newtonian blood characteristics on the resulting flow patterns in such cardiovascular environments.
Morphological stability of an interface between two non-Newtonian fluids moving in a Hele-Shaw cell.
Martyushev, L M; Birzina, A I
2015-01-01
The problem of the morphological stability of an interface in the case of the displacement of one non-Newtonian fluid by another non-Newtonian fluid in a radial Hele-Shaw cell has been considered. Both fluids have been described by the two-parameter Ostwald-de Waele power-law model. The nonzero viscosity of the displacing fluid has been taken into account. A generalized Darcy's law for the system under consideration, as well as an equation for the determination of the critical size of morphological stability with respect to harmonic perturbations (linear analysis), has been derived. Morphological phase diagrams have been constructed, and the region of the parameters in which nonequilibrium reentrant morphological transitions are possible has been revealed.
Akbarzadeh, Pooria
2017-08-07
In this paper, the heat and flow characteristic of third-grade non-Newtonian biofluids flow through a vertical porous human vessel due to peristaltic wall motion are studied. The third-grade model can describe shear thinning (or shear thickening) and normal stress differences, which is acceptable for biofluids modeling. In order to solve the governing equations, the assumption of long-wavelength approximation is utilized. This hypothesis emphasizes that the wavelength of the peristaltic wall motion is large in comparison with the radius of the human vessel, which is widely acceptable in biological investigations. The analytical perturbation method is employed to solve the governing equations. Consequently, analytical expressions for the velocity profile, shear stress, temperature field, and biofluid flow rate are obtained. In addition, the effects of the governing parameters such as the third-grade non-Newtonian parameter, Grashof Number, Eckert number, and porosity, on the results are examined.
NASA Astrophysics Data System (ADS)
Ilyasov, A. M.; Bulgakova, G. T.
2016-08-01
This paper describes a mathematical model of the main fracture isolation in porous media by water-based mature gels. While modeling injection, water infiltration from the gel pack through fracture walls is taking into account, due to which the polymer concentration changes and the residual water resistance factor changes as a consequence. The salutation predicts velocity and pressure fields of the non-Newtonian incompressible fluid filtration for conditions of a non-deformable formation as well as a gel front trajectory in the fracture. The mathematical model of agent injection into the main fracture is based on the fundamental laws of continuum mechanics conservation describing the flow of non-Newtonian and Newtonian fluids separated by an interface plane in a flat channel with permeable walls. The mathematical model is based on a one-dimensional isothermal approximation, with dynamic parameters pressure and velocity, averaged over the fracture section.
NASA Astrophysics Data System (ADS)
Sahebi, S. A. R.; Pourziaei, H.; Feizi, A. R.; Taheri, M. H.; Rostamiyan, Y.; Ganji, D. D.
2015-12-01
In this paper, natural convection of non-Newtonian bio-nanofluids flow between two vertical flat plates is investigated numerically. Sodium Alginate (SA) and Sodium Carboxymethyl Cellulose (SCMC) are considered as the base non-Newtonian fluid, and nanoparticles such as Titania ( TiO2 and Alumina ( Al2O3 were added to them. The effective thermal conductivity and viscosity of nanofluids are calculated through Maxwell-Garnetts (MG) and Brinkman models, respectively. A fourth-order Runge-Kutta numerical method (NUM) and three Weighted Residual Methods (WRMs), Collocation (CM), Galerkin (GM) and Least-Square Method (LSM) and Finite-Element Method (FEM), are used to solve the present problem. The influence of some physical parameters such as nanofluid volume friction on non-dimensional velocity and temperature profiles are discussed. The results show that SCMC- TiO2 has higher velocity and temperature values than other nanofluid structures.
Substitute fluid examinations for liquid manure
NASA Astrophysics Data System (ADS)
Schrader, Kevin; Riedel, Marco; Eichert, Helmut
For the farming industry it is essential to use liquid manure as natural fertilizer. Through new agricultural regulation 2015 in Germany the industry must develop new liquid manure spreader systems because the ammonia and methane emission are limited. In a research project the University of Applied Sciences Zwickau and some other industry partners will develop such a new innovative liquid manure spreader. The new liquid manure spreader should use pulsating air to distribute the liquid manure exactly. The pulsating air, which flows through the pipelines, should be analysed at a test station. For examinations at this test station it is important to find another substitute fluid because liquid manure smells strong, is not transparent and is also not homogeneous enough for scientific investigations. Furthermore it is important to ensure that the substitute fluid is, like liquid manure, a non-Newtonian fluid. The substitute fluid must be a shear-thinning substance - this means the viscosity decrease at higher shear rate. Many different samples like soap-water-farragoes, jelly-water-farragoes, agar-water-farragoes, soap-ethanol-farragoes and more are, for the project, examined in regard of their physical properties to find the best substitute fluid. The samples are examined at the rotational viscometer for viscosity at various shear rates and then compared with the viscosity values of liquid manure.
Substitute fluid examinations for liquid manure
NASA Astrophysics Data System (ADS)
Schrader, Kevin; Riedel, Marco; Eichert, Helmut
2016-11-01
For the farming industry it is essential to use liquid manure as natural fertilizer. Through new agricultural regulation 2015 in Germany the industry must develop new liquid manure spreader systems because the ammonia and methane emission are limited. In a research project the University of Applied Sciences Zwickau and some other industry partners will develop such a new innovative liquid manure spreader. The new liquid manure spreader should use pulsating air to distribute the liquid manure exactly. The pulsating air, which flows through the pipelines, should be analysed at a test station. For examinations at this test station it is important to find another substitute fluid because liquid manure smells strong, is not transparent and is also not homogeneous enough for scientific investigations. Furthermore it is important to ensure that the substitute fluid is, like liquid manure, a non-Newtonian fluid. The substitute fluid must be a shear-thinning substance - this means the viscosity decrease at higher shear rate. Many different samples like soap-water-farragoes, jelly-water-farragoes, agar-water-farragoes, soap-ethanol-farragoes and more are, for the project, examined in regard of their physical properties to find the best substitute fluid. The samples are examined at the rotational viscometer for viscosity at various shear rates and then compared with the viscosity values of liquid manure.
NASA Technical Reports Server (NTRS)
Gecim, B.; Winer, W. O.
1980-01-01
The non-Newtonian constitutive equation of Winer and Bair (1979) is applied to a conventional isothermal film thickness analysis of line contact lubrication of rolling elements providing dimensionless film thickness equations for four lubrication methods. The equations can be applied to high viscosity and rolling speed and low limiting shear stress cases where Newtonian methods are not applicable. This analysis is based on a reasonable range of limiting shear stress which is smaller than the Newtonian values for low viscosity lubricants.
Lu, Gui; Wang, Xiao-Dong; Duan, Yuan-Yuan
2016-10-01
Dynamic wetting is an important interfacial phenomenon in many industrial applications. There have been many excellent reviews of dynamic wetting, especially on super-hydrophobic surfaces with physical or chemical coatings, porous layers, hybrid micro/nano structures and biomimetic structures. This review summarizes recent research on dynamic wetting from the viewpoint of the fluids rather than the solid surfaces. The reviewed fluids range from simple Newtonian fluids to non-Newtonian fluids and complex nanofluids. The fundamental physical concepts and principles involved in dynamic wetting phenomena are also reviewed. This review focus on recent investigations of dynamic wetting by non-Newtonian fluids, including the latest experimental studies with a thorough review of the best dynamic wetting models for non-Newtonian fluids, to illustrate their successes and limitations. This paper also reports on new results on the still fledgling field of nanofluid wetting kinetics. The challenges of research on nanofluid dynamic wetting is not only due to the lack of nanoscale experimental techniques to probe the complex nanoparticle random motion, but also the lack of multiscale experimental techniques or theories to describe the effects of nanoparticle motion at the nanometer scale (10(-9) m) on the dynamic wetting taking place at the macroscopic scale (10(-3) m). This paper describes the various types of nanofluid dynamic wetting behaviors. Two nanoparticle dissipation modes, the bulk dissipation mode and the local dissipation mode, are proposed to resolve the uncertainties related to the various types of dynamic wetting mechanisms reported in the literature.
NASA Astrophysics Data System (ADS)
Thohura, Sharaban; Molla, Md. Mamun; Sarker, M. M. A.
2016-07-01
A study on the natural convection flow of non-Newtonian fluid along a vertical thin cylinder with constant wall temperature using modified power law viscosity model has been done. The basic equations are transformed to non dimensional boundary layer equations and the resulting systems of nonlinear partial differential equations are then solved employing marching order implicit finite difference method. The evolution of the surface shear stress in terms of local skin-friction, the rate of heat transfer in terms of local Nusselt number, velocity and temperature profiles for shear thinning as well as shear-thickening fluid considering the different values of Prandtl number have been focused. For the Newtonian fluids the present numerical results are compared with available published results which show a good agreement indeed. From the results it can be concluded that, at the leading edge, a Newtonian-like solution exists as the shear rate is not large enough to trigger non-Newtonian effects. Non-Newtonian effects can be found when the shear-rate increases beyond a threshold value.
NASA Astrophysics Data System (ADS)
Tong, Dengke; Wang, Ruihe
2004-08-01
In this paper, fractional order derivative, fractal dimension and spectral dimension are introduced into the seepage flow mechanics to establish the relaxation models of non-Newtonian viscoelastic fluids with the fractional derivative in fractal reservoirs. A new type integral transform is introduced, and the flow characteristics of non-Newtonian viscoelastic fluids with the fractional order derivative through a fractal reservoir are studied by using the integral transform, the discrete Laplace transform of sequential fractional derivatives and the generalized Mittag-Leffler functions. Exact solutions are obtained for arbitrary fractional order derivative. The long-time and short-time asymptotic solutions for an infinite formation are also obtained. The pressure transient behavior of non-Newtonian viscoelastic fluids flow through an infinite fractal reservoir is studied by using the Stehfest's inversion method of the numerical Laplace transform. It is shown that the clearer the viscoelastic characteristics of the fluid, the more the fluid is sensitive to the order of the fractional derivative. The new type integral transform provides a new analytical tool for studying the seepage mechanics of fluid in fractal porous media.
Akbarzadeh, Pooria
2016-04-01
In this paper, the unsteady pulsatile magneto-hydrodynamic blood flows through porous arteries concerning the influence of externally imposed periodic body acceleration and a periodic pressure gradient are numerically simulated. Blood is taken into account as the third-grade non-Newtonian fluid. Besides the numerical solution, for small Womersley parameter (such as blood flow through arterioles and capillaries), the analytical perturbation method is used to solve the nonlinear governing equations. Consequently, analytical expressions for the velocity profile, wall shear stress, and blood flow rate are obtained. Excellent agreement between the analytical and numerical predictions is evident. Also, the effects of body acceleration, magnetic field, third-grade non-Newtonian parameter, pressure gradient, and porosity on the flow behaviors are examined. Some important conclusions are that, when the Womersley parameter is low, viscous forces tend to dominate the flow, velocity profiles are parabolic in shape, and the center-line velocity oscillates in phase with the driving pressure gradient. In addition, by increasing the pressure gradient, the mean value of the velocity profile increases and the amplitude of the velocity remains constant. Also, when non-Newtonian effect increases, the amplitude of the velocity profile. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
Simulating non-Newtonian flows with the moving particle semi-implicit method with an SPH kernel
NASA Astrophysics Data System (ADS)
Xiang, Hao; Chen, Bin
2015-02-01
The moving particle semi-implicit (MPS) method and smoothed particle hydrodynamics (SPH) are commonly used mesh-free particle methods for free surface flows. The MPS method has superiority in incompressible flow simulation and simple programing. However, the crude kernel function is not accurate enough for the discretization of the divergence of the shear stress tensor by the particle inconsistency when the MPS method is extended to non-Newtonian flows. This paper presents an improved MPS method with an SPH kernel to simulate non-Newtonian flows. To improve the consistency of the partial derivative, the SPH cubic spline kernel and the Taylor series expansion are combined with the MPS method. This approach is suitable for all non-Newtonian fluids that can be described with τ = μ(|γ|) Δ (where τ is the shear stress tensor, μ is the viscosity, |γ| is the shear rate, and Δ is the strain tensor), e.g., the Casson and Cross fluids. Two examples are simulated including the Newtonian Poiseuille flow and container filling process of the Cross fluid. The results of Poiseuille flow are more accurate than the traditional MPS method, and different filling processes are obtained with good agreement with previous results, which verified the validation of the new algorithm. For the Cross fluid, the jet fracture length can be correlated with We0.28Fr0.78 (We is the Weber number, Fr is the Froude number).
NASA Astrophysics Data System (ADS)
Adam, Saad; Premnath, Kannan
2016-11-01
Fluid mechanics of non-Newtonian fluids, which arise in numerous settings, are characterized by non-linear constitutive models that pose certain unique challenges for computational methods. Here, we consider the lattice Boltzmann method (LBM), which offers some computational advantages due to its kinetic basis and its simpler stream-and-collide procedure enabling efficient simulations. However, further improvements are necessary to improve its numerical stability and accuracy for computations involving broader parameter ranges. Hence, in this study, we extend the cascaded LBM formulation by modifying its moment equilibria and relaxation parameters to handle a variety of non-Newtonian constitutive equations, including power-law and Bingham fluids, with improved stability. In addition, we include corrections to the moment equilibria to obtain an inertial frame invariant scheme without cubic-velocity defects. After preforming its validation study for various benchmark flows, we study the physics of non-Newtonian flow over pairs of circular and square cylinders in a tandem arrangement, especially the wake structure interactions and their effects on resulting forces in each cylinder, and elucidate the effect of the various characteristic parameters.
NASA Astrophysics Data System (ADS)
Le, N. T. P.; Xiao, H.; Myong, R. S.
2014-09-01
The discontinuous Galerkin (DG) method has been popular as a numerical technique for solving the conservation laws of gas dynamics. In the present study, we develop an explicit modal DG scheme for multi-dimensional conservation laws on unstructured triangular meshes in conjunction with non-Newtonian implicit nonlinear coupled constitutive relations (NCCR). Special attention is given to how to treat the complex non-Newtonian type constitutive relations arising from the high degree of thermal nonequilibrium in multi-dimensional gas flows within the Galerkin framework. The Langmuir velocity slip and temperature jump conditions are also implemented into the two-dimensional DG scheme for high Knudsen number flows. As a canonical scalar case, Newtonian and non-Newtonian convection-diffusion Burgers equations are studied to develop the basic building blocks for the scheme. In order to verify and validate the scheme, we applied the scheme to a stiff problem of the shock wave structure for all Mach numbers and to the two-dimensional hypersonic rarefied and low-speed microscale gas flows past a circular cylinder. The computational results show that the NCCR model yields the solutions in better agreement with the direct simulation Monte Carlo (DSMC) data than the Newtonian linear Navier-Stokes-Fourier (NSF) results in all cases of the problem studied.
NASA Astrophysics Data System (ADS)
Javidi, Mahyar; Pope, Michael A.; Hrymak, Andrew N.
2016-06-01
A mathematical model for the dip coating process has been developed for cylindrical geometries with non-Newtonian fluids. This investigation explores the effects of the substrate radius and hydrodynamic behavior of the non-Newtonian viscous fluid on the resulting thin film on the substrate. The coating fluid studied, Dymax 1186-MT, is a resin for fiber optics and used as a matrix to suspend 1 vol. % titanium dioxide particles. The coating substrate is a 100 μm diameter fiber optic diffuser. Ellis viscosity model is applied as a non-Newtonian viscous model for coating thickness prediction, including the influence of viscosity in low shear rates that occurs near the surface of the withdrawal film. In addition, the results of the Newtonian and power law models are compared with the Ellis model outcomes. The rheological properties and surface tension of fluids were analyzed and applied in the models and a good agreement between experimental and analytical solutions was obtained for Ellis model.
The effects of non-Newtonian viscosity on the deformation of red blood cells in a shear flow
NASA Astrophysics Data System (ADS)
Sesay, Juldeh
2005-11-01
The analyses of the effects of non-Newtonian viscosity on the membrane of red blood cells (RBCs) suspended in a shear flow are presented. The specific objective is to investigate the mechanical deformation on the surfaces of an ellipsoidal particle model. The hydrodynamic stresses and other forces on the surface of the particle are used to determine the cell deformation. We extended previous works, which were based on the Newtonian fluid models, to the non-Newtonian case, and focus on imposed shear rate values between 1 and 100 per second. Two viscosity models are investigated, which respectively correspond to a normal person and a patient with cerebrovascular accident (CVA). The results are compared with those obtained assuming a Newtonian model. We observed that the orientation of the cell influences the deformation and the imposed shear rate drives the local shear rate distribution along the particle surface. The integral particle deformation for the non-Newtonian models in the given shear rate regime is higher than that for the Newtonian reference model. Finally, the deformation of the cell surface decreases as the dissipation ratio increases.
Effect of shear-thinning behaviour on liquid-liquid plug flow in microchannels
NASA Astrophysics Data System (ADS)
Roumpea, Evangelia; Chinaud, Maxime; Weheliye, Weheliye Hashi; Angeli, Panagiota; Kahouadji, Lyes; Matar, Omar K.
2016-11-01
The present work investigates the dynamics of plug formation of shear-thinning solutions in a 200 μm microchannel using a two-colour micro-PIV system. Measurements, including phase-averaged velocity fields, have been conducted both at the T-junction inlet and the main channel to enhance understanding of non-Newtonian liquid-liquid flows. Two aqueous glycerol solutions containing xanthan gum are used as the non-Newtonian fluids while 5 cSt silicone oil is the Newtonian phase. The current experimental results revealed a pronounced impact of the xanthan gum (shear-thinning behaviour) on the flow pattern transition boundaries, and enhance the fluid flowrates where plug flow occurred. The addition of polymer resulted also in different hydrodynamic characteristics such as a bullet-shaped plug and an increased film thickness between the plug and the wall. In the present work, the technique allows to capture the velocity field of both phases simultaneously. Experimental results are compared with the numerical simulations provided by the code BLUE. Project funded under the UK Engineering and Physical Sciences Research Council (EPSRC) Programme Grant MEMPHIS.
Raffai, Peter; Szeifert, Gabor; Matone, Luca; Bartos, Imre; Marka, Zsuzsa; Aso, Yoichi; Ricci, Fulvio; Marka, Szabolcs
2011-10-15
We present an experimental opportunity for the future to measure possible violations to Newton's 1/r{sup 2} law in the 0.1-10 m range using dynamic gravity field generators (DFG) and taking advantage of the exceptional sensitivity of modern interferometric techniques. The placement of a DFG in proximity to one of the interferometer's suspended test masses generates a change in the local gravitational field that can be measured at a high signal to noise ratio. The use of multiple DFGs in a null-experiment configuration allows us to test composition-independent non-Newtonian gravity significantly beyond the present limits. Advanced and third-generation gravitational-wave detectors are representing the state-of-the-art in interferometric distance measurement today, therefore, we illustrate the method through their sensitivity to emphasize the possible scientific reach. Nevertheless, it is expected that due to the technical details of gravitational-wave detectors, DFGs shall likely require dedicated custom-configured interferometry. However, the sensitivity measure we derive is a solid baseline indicating that it is feasible to consider probing orders of magnitude into the pristine parameter well beyond the present experimental limits significantly cutting into the theoretical parameter space.
NASA Astrophysics Data System (ADS)
Bose, Sayan; Banerjee, Moloy
2015-01-01
Magnetic nanoparticles drug carriers continue to attract considerable interest for drug targeting in the treatment of cancer and other pathological conditions. Magnetic carrier particles with surface-bound drug molecules are injected into the vascular system upstream from the desired target site, and are captured at the target site via a local applied magnetic field. Herein, a numerical investigation of steady magnetic drug targeting (MDT) using functionalized magnetic micro-spheres in partly occluded blood vessel having a 90° bent is presented considering the effects of non-Newtonian characteristics of blood. An Eulerian-Lagrangian technique is adopted to resolve the hemodynamic flow and the motion of the magnetic particles in the flow using ANSYS FLUENT. An implantable infinitely long cylindrical current carrying conductor is used to create the requisite magnetic field. Targeted transport of the magnetic particles in a partly occluded vessel differs distinctly from the same in a regular unblocked vessel. Parametric investigation is conducted and the influence of the insert configuration and its position from the central plane of the artery (zoffset), particle size (dp) and its magnetic property (χ) and the magnitude of current (I) on the "capture efficiency" (CE) is reported. Analysis shows that there exists an optimum regime of operating parameters for which deposition of the drug carrying magnetic particles in a target zone on the partly occluded vessel wall can be maximized. The results provide useful design bases for in vitro set up for the investigation of MDT in stenosed blood vessels.
Wu, Binxin
2010-12-01
In this paper, 12 turbulence models for single-phase non-newtonian fluid flow in a pipe are evaluated by comparing the frictional pressure drops obtained from computational fluid dynamics (CFD) with those from three friction factor correlations. The turbulence models studied are (1) three high-Reynolds-number k-ε models, (2) six low-Reynolds-number k-ε models, (3) two k-ω models, and (4) the Reynolds stress model. The simulation results indicate that the Chang-Hsieh-Chen version of the low-Reynolds-number k-ε model performs better than the other models in predicting the frictional pressure drops while the standard k-ω model has an acceptable accuracy and a low computing cost. In the model applications, CFD simulation of mixing in a full-scale anaerobic digester with pumped circulation is performed to propose an improvement in the effective mixing standards recommended by the U.S. EPA based on the effect of rheology on the flow fields. Characterization of the velocity gradient is conducted to quantify the growth or breakage of an assumed floc size. Placement of two discharge nozzles in the digester is analyzed to show that spacing two nozzles 180° apart with each one discharging at an angle of 45° off the wall is the most efficient. Moreover, the similarity rules of geometry and mixing energy are checked for scaling up the digester.
Wu, Binxin
2011-02-01
This study evaluates six turbulence models for mechanical agitation of non-Newtonian fluids in a lab-scale anaerobic digestion tank with a pitched blade turbine (PBT) impeller. The models studied are: (1) the standard k-ɛ model, (2) the RNG k-ɛ model, (3) the realizable k-ɛ model, (4) the standard k-ω model, (5) the SST k-ω model, and (6) the Reynolds stress model. Through comparing power and flow numbers for the PBT impeller obtained from computational fluid dynamics (CFD) with those from the lab specifications, the realizable k-ɛ and the standard k-ω models are found to be more appropriate than the other turbulence models. An alternative method to calculate the Reynolds number for the moving zone that characterizes the impeller rotation is proposed to judge the flow regime. To check the effect of the model setup on the predictive accuracy, both discretization scheme and numerical approach are investigated. The model validation is conducted by comparing the simulated velocities with experimental data in a lab-scale digester from literature. Moreover, CFD simulation of mixing in a full-scale digester with two side-entry impellers is performed to optimize the installation. Copyright © 2010 Elsevier Ltd. All rights reserved.
Viscosity effects in foam drainage: Newtonian and non-newtonian foaming fluids.
Safouane, M; Saint-Jalmes, A; Bergeron, V; Langevin, D
2006-02-01
We have studied the drainage of foams made from Newtonian and non-Newtonian solutions of different viscosities. Forced-drainage experiments first show that the behavior of Newtonian solutions and of shear-thinning ones (foaming solutions containing either Carbopol or Xanthan) are identical, provided one considers the actual viscosity corresponding to the shear rate found inside the foam. Second, for these fluids, a drainage regime transition occurs as the bulk viscosity is increased, illustrating a coupling between surface and bulk flow in the channels between bubbles. The properties of this transition appear different from the ones observed in previous works in which the interfacial viscoelasticity was varied. Finally, we show that foams made of solutions containing long flexible PolyEthylene Oxide (PEO) molecules counter-intuitively drain faster than foams made with Newtonian solutions of the same viscosity. Complementary experiments made with fluids having all the same viscosity but different responses to elongational stresses (PEO-based Boger fluids) suggest an important role of the elastic properties of the PEO solutions on the faster drainage.
Bleyer, J; Coussot, P
2014-06-01
We study the flow, through a model two-dimensional porous medium, of Newtonian fluids, power-law fluids, and viscoplastic fluids in the laminar regime and with moderate or dominant effects of the yielding term. A numerical technique able to take properly into account yielding effects in viscoplastic flows without any regularization is used to determine the detailed flow characteristics. We show that as soon as the distance between the disks forming the porous medium is sufficiently small, the velocity field and in particular the distribution function of the velocity of these different fluids in a wide range of flow regimes are similar. Moreover, the volume fraction of fluid at rest is negligible even at low flow rate. Thus the non-Newtonian character of a fluid flowing through such a complex geometry tends to be broken. We suggest that this is due to the fact that in a flow through a channel of rapidly varying cross section, the deformation, and thus the flow field, is imposed on the fluid, a situation that is encountered almost everywhere in a porous medium. These results make it possible to deduce a general expression for Darcy's law of these fluid types and estimate the parameters appearing in this expression.
A Numerical Study of Mesh Adaptivity in Multiphase Flows with Non-Newtonian Fluids
NASA Astrophysics Data System (ADS)
Percival, James; Pavlidis, Dimitrios; Xie, Zhihua; Alberini, Federico; Simmons, Mark; Pain, Christopher; Matar, Omar
2014-11-01
We present an investigation into the computational efficiency benefits of dynamic mesh adaptivity in the numerical simulation of transient multiphase fluid flow problems involving Non-Newtonian fluids. Such fluids appear in a range of industrial applications, from printing inks to toothpastes and introduce new challenges for mesh adaptivity due to the additional ``memory'' of viscoelastic fluids. Nevertheless, the multiscale nature of these flows implies huge potential benefits for a successful implementation. The study is performed using the open source package Fluidity, which couples an unstructured mesh control volume finite element solver for the multiphase Navier-Stokes equations to a dynamic anisotropic mesh adaptivity algorithm, based on estimated solution interpolation error criteria, and conservative mesh-to-mesh interpolation routine. The code is applied to problems involving rheologies ranging from simple Newtonian to shear-thinning to viscoelastic materials and verified against experimental data for various industrial and microfluidic flows. This work was undertaken as part of the EPSRC MEMPHIS programme grant EP/K003976/1.
Mass transport in a porous microchannel for non-Newtonian fluid with electrokinetic effects.
Mondal, Sourav; De, Sirshendu
2013-03-01
Quantification of mass transfer in porous microchannel is of paramount importance in several applications. Transport of neutral solute in presence of convective-diffusive EOF having non-Newtonian rheology, in a porous microchannel was presented in this article. The governing mass transfer equation coupled with velocity field was solved along with associated boundary conditions using a similarity solution method. An analytical solution of mass transfer coefficient and hence, Sherwood number were derived from first principles. The corresponding effects of assisting and opposing pressure-driven flow and EOF were also analyzed. The influence of wall permeation, double-layer thickness, rheology, etc. on the mass transfer was also investigated. Permeation at the wall enhanced the mass transfer coefficient more than five times compared to impervious conduit in case of pressure-driven flow assisting the EOF at higher values of κh. Shear thinning fluid exhibited more enhancement of Sherwood number in presence of permeation compared to shear thickening one. The phenomenon of stagnation was observed at a particular κh (∼2.5) in case of EOF opposing the pressure-driven flow. This study provided a direct quantification of transport of a neutral solute in case of transdermal drug delivery, transport of drugs from blood to target region, etc.
Viscoelastic fluid-structure interaction between a non-Newtonian fluid flow and flexible cylinder
NASA Astrophysics Data System (ADS)
Dey, Anita; Modarres-Sadeghi, Yahya; Rothstein, Jonathan
2016-11-01
It is well known that when a flexible or flexibly-mounted structure is placed perpendicular to the flow of a Newtonian fluid, it can oscillate due to the shedding of separated vortices at high Reynolds numbers. If the same flexible object is placed in non-Newtonian flows, however, the structure's response is still unknown. Unlike Newtonian fluids, the flow of viscoelastic fluids can become unstable at infinitesimal Reynolds numbers due to a purely elastic flow instability. In this talk, we will present a series of experiments investigating the response of a flexible cylinder placed in the cross flow of a viscoelastic fluid. The elastic flow instabilities occurring at high Weissenberg numbers can exert fluctuating forces on the flexible cylinder thus leading to nonlinear periodic oscillations of the flexible structure. These oscillations are found to be coupled to the time-dependent state of viscoelastic stresses in the wake of the flexible cylinder. The static and dynamic responses of the flexible cylinder will be presented over a range of flow velocities, along with measurements of velocity profiles and flow-induced birefringence, in order to quantify the time variation of the flow field and the state of stress in the fluid.
Deciphering physical properties of preferential flowpaths using non-Newtonian fluids
NASA Astrophysics Data System (ADS)
Stewart, R. D.; Abou Najm, M.; Rupp, D. E.
2016-12-01
Soils often contain features such as desiccation cracks, root channels, and animal/insect burrows (i.e., macropores) that can cause the preferential movement of water, solutes, and gases. Current methods to determine the physical and hydraulic properties (e.g., volume, hydraulic conductivity, connectivity) of such pathways typically require destructive sampling, where the soil profile is excavated and/or otherwise disturbed. This effort typically precludes that particular location/feature from continued study. At the same time, these methods often do not allow determination of the independent properties of the macropores and soil matrix, which can be useful when modeling flow and transport processes. Shear-thinning fluids, in which the fluid viscosity varies as a function of soil pore size, can be used to infer and quantify various physical and hydraulic properties in macroporous soils. Moreover, certain shear-thinning fluids, including guar gum, will naturally biodegrade in soils, meaning that they can be used without permanently altering the soil. In this study we present work in which we characterize the shear-thinning behavior of guar gum solutions, and then provide examples of how this substance can be used to 1) quantify the volume of shrinkage cracks, and 2) characterize the effect of insect burrows on water and gas exchange between soils and the atmosphere. Overall, these examples highlight how non-Newtonian fluids are offering new possibilities for understanding and modeling unsaturated zone properties and processes.
Numerical Simulations of Non-Newtonian Convection in Ice: Application to Europa
NASA Technical Reports Server (NTRS)
Barr, A. C.; Pappalardo, R. T.
2003-01-01
Numerical simulations of solid state convection in Europa's ice shell have so far been limited to consideration of Newtonian flow laws, where the viscosity of ice is strongly dependent upon temperature, predicting that a stagnant lid should form at the top (10-40%) of a convecting ice shell. Such large thicknesses seem to contradict estimates of the effective elastic thickness of Europa s ice shell during its geologically active period. Recent laboratory experiments characterize the rheology of ice as the sum of contributions from several temperature and strain rate-dependent creep mechanisms. We present the results of numerical simulations of convection within Europa s ice shell using the finite-element model Citcom, applying the non-Newtonian rheology of grain boundry sliding. Our calculations suggest a shallower brittle/ductile transition and larger interior convective velocities compared to Newtonian rheology. The flow field is time-dependent, with small, localized upwellings and downwellings at the thermal boundary layers that have minimal topographic expression at the surface.
Non-Newtonian stress tensor and thermal conductivity tensor in granular plane shear flow
NASA Astrophysics Data System (ADS)
Alam, Meheboob; Saha, Saikat
2014-11-01
The non-Newtonian stress tensor and the heat flux in the plane shear flow of smooth inelastic disks are analysed from the Grad-level moment equations using the anisotropic Gaussian as a reference. Closed-form expressions for shear viscosity, pressure, first normal stress difference (N1) and the dissipation rate are given as functions of (i) the density or the area fraction (ν), (ii) the restitution coefficient (e), (iii) the dimensionless shear rate (R), (iv) the temperature anisotropy [ η, the difference between the principal eigenvalues of the second moment tensor] and (v) the angle (ϕ) between the principal directions of the shear tensor and the second moment tensor. Particle simulation data for a sheared hard-disk system is compared with theoretical results, with good agreement for p, μ and N1 over a large range of density. In contrast, the predictions from a Navier-Stokes order constitutive model are found to deviate significantly from both the simulation and the moment theory even at moderate values of e. We show that the gradient of the deviatoric part of the kinetic stress drives a heat current and the thermal conductivity is characterized by an anisotropic 2nd rank tensor for which explicit expressions are derived.
Gijsen, F J; van de Vosse, F N; Janssen, J D
1999-06-01
Laser Doppler anemometry experiments and finite element simulations of steady flow in a three dimensional model of the carotid bifurcation were performed to investigate the influence of non-Newtonian properties of blood on the velocity distribution. The axial velocity distribution was measured for two fluids: a non-Newtonian blood analog fluid and a Newtonian reference fluid. Striking differences between the measured flow fields were found. The axial velocity field of the non-Newtonian fluid was flattened, had lower velocity gradients at the divider wall, and higher velocity gradients at the non-divider wall. The flow separation, as found with the Newtonian fluid, was absent. In the computations, the shear thinning behavior of the analog blood fluid was incorporated through the Carreau-Yasuda model. The viscoelastic properties of the fluid were not included. A comparison between the experimental and numerical results showed good agreement, both for the Newtonian and the non-Newtonian fluid. Since only shear thinning was included, this seems to be the dominant non-Newtonian property of the blood analog fluid under steady flow conditions.
Swimming bacteria in liquid crystal
NASA Astrophysics Data System (ADS)
Sokolov, Andrey; Zhou, Shuang; Aranson, Igor; Lavrentovich, Oleg
2014-03-01
Dynamics of swimming bacteria can be very complex due to the interaction between the bacteria and the fluid, especially when the suspending fluid is non-Newtonian. Placement of swimming bacteria in lyotropic liquid crystal produces a new class of active materials by combining features of two seemingly incompatible constituents: self-propelled live bacteria and ordered liquid crystals. Here we present fundamentally new phenomena caused by the coupling between direction of bacterial swimming, bacteria-triggered flows and director orientations. Locomotion of bacteria may locally reduce the degree of order in liquid crystal or even trigger nematic-isotropic phase transition. Microscopic flows generated by bacterial flagella disturb director orientation. Emerged birefringence patterns allow direct optical observation and quantitative characterization of flagella dynamics. At high concentration of bacteria we observed the emergence of self-organized periodic texture caused by bacteria swimming. Our work sheds new light on self-organization in hybrid bio-mechanical systems and can lead to valuable biomedical applications. Was supported by the US DOE, Office of Basic Energy Sciences, Division of Materials Science and Engineering, under the Contract No. DE AC02-06CH11357.
Intermittent gravity-driven flow of grains through narrow pipes
NASA Astrophysics Data System (ADS)
Alvarez, Carlos A.; de Moraes Franklin, Erick
2017-01-01
Grain flows through pipes are frequently found in various settings, such as in pharmaceutical, chemical, petroleum, mining and food industries. In the case of size-constrained gravitational flows, density waves consisting of alternating high- and low-compactness regions may appear. This study investigates experimentally the dynamics of density waves that appear in gravitational flows of fine grains through vertical and slightly inclined pipes. The experimental device consisted of a transparent glass pipe through which different populations of glass spheres flowed driven by gravity. Our experiments were performed under controlled ambient temperature and relative humidity, and the granular flow was filmed with a high-speed camera. Experimental results concerning the length scales and celerities of density waves are presented, together with a one-dimensional model and a linear stability analysis. The analysis exhibits the presence of a long-wavelength instability, with the most unstable mode and a cut-off wavenumber whose values are in agreement with the experimental results.
Kinetics of gravity-driven water channels under steady rainfall.
Cejas, Cesare M; Wei, Yuli; Barrois, Remi; Frétigny, Christian; Durian, Douglas J; Dreyfus, Rémi
2014-10-01
We investigate the formation of fingered flow in dry granular media under simulated rainfall using a quasi-two-dimensional experimental setup composed of a random close packing of monodisperse glass beads. Using controlled experiments, we analyze the finger instabilities that develop from the wetting front as a function of fundamental granular (particle size) and fluid properties (rainfall, viscosity). These finger instabilities act as precursors for water channels, which serve as outlets for water drainage. We look into the characteristics of the homogeneous wetting front and channel size as well as estimate relevant time scales involved in the instability formation and the velocity of the channel fingertip. We compare our experimental results with that of the well-known prediction developed by Parlange and Hill [D. E. Hill and J. Y. Parlange, Soil Sci. Soc. Am. Proc. 36, 697 (1972)]. This model is based on linear stability analysis of the growth of perturbations arising at the interface between two immiscible fluids. Results show that, in terms of morphology, experiments agree with the proposed model. However, in terms of kinetics we nevertheless account for another term that describes the homogenization of the wetting front. This result shows that the manner we introduce the fluid to a porous medium can also influence the formation of finger instabilities. The results also help us to calculate the ideal flow rate needed for homogeneous distribution of water in the soil and minimization of runoff, given the grain size, fluid density, and fluid viscosity. This could have applications in optimizing use of irrigation water.
Kinetics of gravity-driven water channels under steady rainfall
NASA Astrophysics Data System (ADS)
Cejas, Cesare M.; Wei, Yuli; Barrois, Remi; Frétigny, Christian; Durian, Douglas J.; Dreyfus, Rémi
2014-10-01
We investigate the formation of fingered flow in dry granular media under simulated rainfall using a quasi-two-dimensional experimental setup composed of a random close packing of monodisperse glass beads. Using controlled experiments, we analyze the finger instabilities that develop from the wetting front as a function of fundamental granular (particle size) and fluid properties (rainfall, viscosity). These finger instabilities act as precursors for water channels, which serve as outlets for water drainage. We look into the characteristics of the homogeneous wetting front and channel size as well as estimate relevant time scales involved in the instability formation and the velocity of the channel fingertip. We compare our experimental results with that of the well-known prediction developed by Parlange and Hill [D. E. Hill and J. Y. Parlange, Soil Sci. Soc. Am. Proc. 36, 697 (1972), 10.2136/sssaj1972.03615995003600050010x]. This model is based on linear stability analysis of the growth of perturbations arising at the interface between two immiscible fluids. Results show that, in terms of morphology, experiments agree with the proposed model. However, in terms of kinetics we nevertheless account for another term that describes the homogenization of the wetting front. This result shows that the manner we introduce the fluid to a porous medium can also influence the formation of finger instabilities. The results also help us to calculate the ideal flow rate needed for homogeneous distribution of water in the soil and minimization of runoff, given the grain size, fluid density, and fluid viscosity. This could have applications in optimizing use of irrigation water.
Gravity-driven flow over heated, porous, wavy surfaces
NASA Astrophysics Data System (ADS)
Ogden, K. A.; D'Alessio, S. J. D.; Pascal, J. P.
2011-12-01
The method of weighted residuals for thin film flow down an inclined plane is extended to include the effects of bottom waviness, heating, and permeability in this study. A bottom slip condition is used to account for permeability and a constant temperature bottom boundary condition is applied. A weighted residual model (WRM) is derived and used to predict the combined effects of bottom waviness, heating, and permeability on the stability of the flow. In the absence of bottom topography, the results are compared to theoretical predictions from the corresponding Benney equation and also to existing Orr-Sommerfeld predictions. The excellent agreement found indicates that the model does faithfully predict the theoretical critical Reynolds number, which accounts for heating and permeability, and these effects are found to destabilize the flow. Floquet theory is used to investigate how bottom waviness influences the stability of the flow. Finally, numerical simulations of the model equations are also conducted and compared with numerical solutions of the full Navier-Stokes equations for the case with bottom permeability. These results are also found to agree well, which suggests that the WRM remains valid even when permeability is included.
Gravity driven current during sessile drop coalescence on a surface
NASA Astrophysics Data System (ADS)
Zhang, Ying; Oberdick, Samuel; Garoff, Stephen; Anna, Shelley
2013-11-01
We study the mixing behavior of two sessile drops following coalescence on a flat surface. The surface is composed of silicone elastomer on which the drops exhibit contact angles of about 90 degree. The two drops are of equal volume at coalescence, but different densities and viscosities. Using laser induced fluorescence, we obtain both a top view of the contact line motion and a side view of the cross-sectional flow. During the coalescence stage, the initial healing of the meniscus bridge and damping of capillary waves occur on time scales comparable to the inertio-capillary time. However, the interface between the dyed and undyed components remains sharp, with diffusive mixing occurring at much longer timescales. At intermediate time scales the motion is controlled by a gravity current, which leads to the eventual stratification into two separate horizontal layers within the composite drop. Using lubrication analysis, we characterize the gravity current as a function of the drop sizes, and the density and viscosity differences between the two merging fluids. The numerical solution of the lubrication analysis captures the observed scaling of the time dependent interface movement as a function of fluid and geometric parameters.
Gravity driven effect in flowing particle laden thin films
NASA Astrophysics Data System (ADS)
Glidden, Robert; Fox, Christopher; Ward, Thomas; Bertozzi, Andrea
2007-11-01
The flow characteristics of an anisopycnic particle-laden thin film flowing down an inclined plane is analyzed experimentally near the maximum packing limit for polydisperse hard spheres. The mutliphase fluid is a mixture of silicone oil and polydisperse heavy glass beads of varying viscosities and bead diameter, respectively. For the high volume concentrations studied, 50% < φ< 56%, we observe that the elapsed time, t, versus average front position, xN, still scales with the Huppert solution where CN=xN^3/t is a constant [Nature 300(2), 1982]. For very high background fluid viscosities, the particle settling velocity is very slow with respect to the fluid and CN decreases with increasing concentration. As the background fluid viscosity is decreased CN remains relatively constant as the particle density approaches the maximum. We propose that the latter effect may be the result of a transition from viscous fluid flow to that of a lubricated sliding solid body. Experiments are performed to test an empirical correlation for the data in this parameter regime based on this hypothesis.
Gravity-driven soap film dynamics in subcritical regimes
NASA Astrophysics Data System (ADS)
Auliel, M. I.; Castro, F.; Sosa, R.; Artana, G.
2015-10-01
We undertake the analysis of soap-film dynamics with the classical approach of asymptotic expansions. We focus our analysis in vertical soap film tunnels operating in subcritical regimes with elastic Mach numbers Me=O(10-1) . Considering the associated set of nondimensional numbers that characterize this flow, we show that the flow behaves as a two-dimensional (2D) divergence free flow with variable mass density. When the soap film dynamics agrees with that of a 2D and almost constant mass density flow, the regions where the second invariant of the velocity gradient is non-null correspond to regions where the rate of change of film thickness is non-negligible.
On exponential stability of gravity driven viscoelastic flows
NASA Astrophysics Data System (ADS)
Jiang, Fei; Wu, Guochun; Zhong, Xin
2016-05-01
We investigate stability of an equilibrium state to a nonhomogeneous incompressible viscoelastic fluid driven by gravity in a bounded domain Ω ⊂R3 of class C3. First, we establish a critical number κC, which depends on the equilibrium density and the gravitational constant, and is a threshold of the elasticity coefficient κ for instability and stability of the linearized perturbation problem around the equilibrium state. Then we prove that the equilibrium state is exponential stability provided that κ >κC and the initial disturbance quantities around the equilibrium state satisfy some relations. In particular, if the equilibrium density ρ bar is a Rayleigh-Taylor (RT) type and ρbar‧ is a constant, our result strictly shows that the sufficiently large elasticity coefficient can prevent the RT instability from occurrence.
Gravity Driven Universe: Energy from a Unified Field
NASA Astrophysics Data System (ADS)
Masters, Roy
2012-10-01
One way or another, whether push or pull, we know for sure that gravity is omnidirectional with identical mathematics. With PULL, gravity can be seen as as a property of matter. If so something is wrong. The Moon, lifting the tides twice-daily, should have fallen into orbital decay, with Earth having pulled it down eons ago. It is puzzling that physicists are not troubled by the fact that the Moon not only insists on forever lifting the tides, but, adding insult to injury, keeps moving it about 4 cm further away from Earth each year. Now if instead, we consider gravity as driven by an omnidirectional pressure--a PUSH force, another possibility arises. We can consider that it is mysteriously infusing energy into the Earth-Moon system, sustaining the Moon's orbit with the appearance of raising the tides and actually pushing it away from Earth. Here we can show push and pull, while being identical in their mathematics, have different outcomes. With push, gravity is a property of the universe. If this is true, then gravitation is flowing from an everlasting source, and the Earth/Moon system is one example of many other vacuum energy machines in the universe.
NASA Astrophysics Data System (ADS)
Gollakota, Anjani R. K.; Kishore, Nanda
2017-06-01
The bubbles are almost ubiquitous in many chemical and processing industries; and many of the polymeric solutions obey non-Newtonian rheological characteristics. Therefore, in this work the rise and deformation characteristics of spheroid bubbles in Carreau model non-Newtonian fluids are numerically investigated using a level set method. To demonstrate the validity of the moving bubble interface, the present simulations are compared with existing numerical and experimental results available in the literature; and for these comparisons, the computational geometries are considered same as reported in corresponding literatures. The present bubble deformation characteristics are satisfactorily agreeing with their literature counterparts. After establishing the validity of the numerical solution procedure, the same method is applied to obtain the deformation characteristics of an air bubble in Carreau model non-Newtonian fluids. Further, the results in terms of the volume fraction images, streamlines, and viscosity profiles around the deforming bubbles are presented as function of the bubble rise time.
Frolov, S V; Sindeev, S V; Liepsch, D; Balasso, A
2016-05-18
According to the clinical data, flow conditions play a major role in the genesis of intracranial aneurysms. The disorder of the flow structure is the cause of damage of the inner layer of the vessel wall, which leads to the development of cerebral aneurysms. Knowledge of the alteration of the flow field in the aneurysm region is important for treatment. The aim is to study quantitatively the flow structure in an patient-specific aneurysm model of the internal carotid artery using both experimental and computational fluid dynamics (CFD) methods with Newtonian and non-Newtonian fluids. A patient-specific geometry of aneurysm of the internal carotid artery was used. Patient data was segmented and smoothed to obtain geometrical model. An elastic true-to-scale silicone model was created with stereolithography. For initial investigation of the blood flow, the flow was visualized by adding particles into the silicone model. The precise flow velocity measurements were done using 1D Laser Doppler Anemometer with a spatial resolution of 50 μ m and a temporal resolution of 1 ms. The local velocity measurements were done at a distance of 4 mm to each other. A fluid with non-Newtonian properties was used in the experiment. The CFD simulations for unsteady-state problem were done using constructed hexahedral mesh for Newtonian and non-Newtonian fluids. Using 1D laser Doppler Anemometer the minimum velocity magnitude at the end of systole -0.01 m/s was obtained in the aneurysm dome while the maximum velocity 1 m/s was at the center of the outlet segment. On central cross section of the aneurysm the maximum velocity value is only 20% of the average inlet velocity. The average velocity on the cross-section is only 11% of the inlet axial velocity. Using the CFD simulation the wall shear stresses for Newtonian and non-Newtonian fluid at the end of systolic phase (t= 0.25 s) were computed. The wall shear stress varies from 3.52 mPa (minimum value) to 10.21 Pa (maximum value) for the
Physics of Life: A Model for Non-Newtonian Properties of Living Systems
NASA Technical Reports Server (NTRS)
Zak, Michail
2010-01-01
This innovation proposes the reconciliation of the evolution of life with the second law of thermodynamics via the introduction of the First Principle for modeling behavior of living systems. The structure of the model is quantum-inspired: it acquires the topology of the Madelung equation in which the quantum potential is replaced with the information potential. As a result, the model captures the most fundamental property of life: the progressive evolution; i.e. the ability to evolve from disorder to order without any external interference. The mathematical structure of the model can be obtained from the Newtonian equations of motion (representing the motor dynamics) coupled with the corresponding Liouville equation (representing the mental dynamics) via information forces. All these specific non-Newtonian properties equip the model with the levels of complexity that matches the complexity of life, and that makes the model applicable for description of behaviors of ecological, social, and economical systems. Rather than addressing the six aspects of life (organization, metabolism, growth, adaptation, response to stimuli, and reproduction), this work focuses only on biosignature ; i.e. the mechanical invariants of life, and in particular, the geometry and kinematics of behavior of living things. Living things obey the First Principles of Newtonian mechanics. One main objective of this model is to extend the First Principles of classical physics to include phenomenological behavior on living systems; to develop a new mathematical formalism within the framework of classical dynamics that would allow one to capture the specific properties of natural or artificial living systems such as formation of the collective mind based upon abstract images of the selves and non-selves; exploitation of this collective mind for communications and predictions of future expected characteristics of evolution; and for making decisions and implementing the corresponding corrections if
Electro-osmosis of non-Newtonian fluids in porous media using lattice Poisson-Boltzmann method.
Chen, Simeng; He, Xinting; Bertola, Volfango; Wang, Moran
2014-12-15
Electro-osmosis in porous media has many important applications in various areas such as oil and gas exploitation and biomedical detection. Very often, fluids relevant to these applications are non-Newtonian because of the shear-rate dependent viscosity. The purpose of this study was to investigate the behaviors and physical mechanism of electro-osmosis of non-Newtonian fluids in porous media. Model porous microstructures (granular, fibrous, and network) were created by a random generation-growth method. The nonlinear governing equations of electro-kinetic transport for a power-law fluid were solved by the lattice Poisson-Boltzmann method (LPBM). The model results indicate that: (i) the electro-osmosis of non-Newtonian fluids exhibits distinct nonlinear behaviors compared to that of Newtonian fluids; (ii) when the bulk ion concentration or zeta potential is high enough, shear-thinning fluids exhibit higher electro-osmotic permeability, while shear-thickening fluids lead to the higher electro-osmotic permeability for very low bulk ion concentration or zeta potential; (iii) the effect of the porous medium structure depends significantly on the constitutive parameters: for fluids with large constitutive coefficients strongly dependent on the power-law index, the network structure shows the highest electro-osmotic permeability while the granular structure exhibits the lowest permeability on the entire range of power law indices considered; when the dependence of the constitutive coefficient on the power law index is weaker, different behaviors can be observed especially in case of strong shear thinning. Copyright © 2014 Elsevier Inc. All rights reserved.
Widmer Soyka, René P; López, Alejandro; Persson, Cecilia; Cristofolini, Luca; Ferguson, Stephen J
2013-11-01
Fluids present or used in biology, medicine and (biomedical) engineering are often significantly non-Newtonian. Furthermore, they are chemically complex and can interact with the porous matrix through which they flow. The porous structures themselves display complex morphological inhomogeneities on a wide range of length scales. In vertebroplasty, a shear-thinning fluid, e.g. poly(methyl methacrylate) (PMMA), is injected into the cavities of vertebral trabecular bone for the stabilization of fractures and metastatic lesions. The main objective of this study was therefore to provide a protocol for numerically investigating the rheological properties of PMMA-based bone cements to predict its spreading behavior while flowing through vertebral trabecular bone. A numerical upscaling scheme based on a dimensionless formulation of the Navier-Stokes equation is proposed in order to relate the pore-scale rheological properties of the PMMA that were experimentally estimated using a plate rheometer, to the continuum-scale. On the pore length scale, a viscosity change on the order of one magnitude was observed whilst the shear-thinning properties caused a viscosity change on the order of only 10% on the continuum length scale and in a flow regime that is relevant for vertebroplasty. An experimental validation, performed on human cadaveric vertebrae (n=9), showed a significant improvement of the cement spreading prediction accuracy with a non-Newtonian formulation. A root mean square cement surface prediction error of 1.53mm (assuming a Newtonian fluid) and 1.37mm (assuming a shear-thinning fluid) was found. Our findings highlight the importance of incorporating the non-Newtonian fluids properties in computational models of porous media at the appropriate length scale.
Ali, N; Asghar, Z; Anwar Bég, O; Sajid, M
2016-05-21
Gliding bacteria are an assorted group of rod-shaped prokaryotes that adhere to and glide on certain layers of ooze slime attached to a substratum. Due to the absence of organelles of motility, such as flagella, the gliding motion is caused by the waves moving down the outer surface of these rod-shaped cells. In the present study we employ an undulating surface model to investigate the motility of bacteria on a layer of non-Newtonian slime. The rheological behavior of the slime is characterized by an appropriate constitutive equation, namely the Carreau model. Employing the balances of mass and momentum conservation, the hydrodynamic undulating surface model is transformed into a fourth-order nonlinear differential equation in terms of a stream function under the long wavelength assumption. A perturbation approach is adopted to obtain closed form expressions for stream function, pressure rise per wavelength, forces generated by the organism and power required for propulsion. A numerical technique based on an implicit finite difference scheme is also employed to investigate various features of the model for large values of the rheological parameters of the slime. Verification of the numerical solutions is achieved with a variational finite element method (FEM). The computations demonstrate that the speed of the glider decreases as the rheology of the slime changes from shear-thinning (pseudo-plastic) to shear-thickening (dilatant). Moreover, the viscoelastic nature of the slime tends to increase the swimming speed for the shear-thinning case. The fluid flow in the pumping (generated where the organism is not free to move but instead generates a net fluid flow beneath it) is also investigated in detail. The study is relevant to marine anti-bacterial fouling and medical hygiene biophysics. Copyright © 2016 Elsevier Ltd. All rights reserved.
Self-Consistent Generation of Single-Plume State for Enceladus Using Non-Newtonian Rheology
NASA Astrophysics Data System (ADS)
Besserer, Jonathan; Rozel, A.; Golabek, G. J.; Kaplan, M.; Becker, T. W.; Tackley, P. J.
2013-10-01
The thermal dichotomy of Enceladus suggests an asymmetrical structure in its global heat transfer [1]. So far, most of the models proposed that obtained such a distribution have prescribed an a priori asymmetry, i.e. a mechanical anomaly in the south polar ice shell surface [2], at its base [3], or in core topography [4]. We present here the first set of numerical simulations of convection that yield a stable single-plume state for Enceladus without prescribed mechanical asymmetry. Using the convection code StagYY [5,6] in a 2D-spherical annulus geometry [7], we show that a non-Newtonian rheology is sufficient to create a localized, single hot plume surrounded by a conductive ice mantle. Using a grain size-dependent rheology [8,9], we obtain a self-sustained state in which a region of small angular extent has a sufficiently low viscosity to allow convection to occur due to the stress-dependent part of the rheological law. We find that the single-plume state is very unlikely to remain stable if the rheology is Newtonian. For simplicity, we neglect tidal heating effects. Despite this, our preferred model yields a south polar heat flux which is about half the recently revised observational value [10]. References: [1] Spencer and Nimmo, 2013, An. Rev. Earth Plan. Sci., 41, 693-717 [2] Han et al., 2012, Icarus, 218, 320-330 [3] Běhounková et al. 2012, Icarus, 219, 655-664 [4] Han and Showman, 2012, LPSC, 2028 [5] Tackley, 1993, GRL, 20, 2187-2190 [6] Tackley, 2008, PEPI, 171, 7-18 [7] Hernlund and Tackley, 2008, PEPI, 171, 48-54 [8] Rozel, 2012, GGG, 13, Q10020 [9] Barr and McKinnon, 2007, JGR, 112, E02012 [10] Spencer et al., 2013, EPSC Abstract, 8, EPSC2013-840-1
Accurate prediction of wall shear stress in a stented artery: newtonian versus non-newtonian models.
Mejia, Juan; Mongrain, Rosaire; Bertrand, Olivier F
2011-07-01
A significant amount of evidence linking wall shear stress to neointimal hyperplasia has been reported in the literature. As a result, numerical and experimental models have been created to study the influence of stent design on wall shear stress. Traditionally, blood has been assumed to behave as a Newtonian fluid, but recently that assumption has been challenged. The use of a linear model; however, can reduce computational cost, and allow the use of Newtonian fluids (e.g., glycerine and water) instead of a blood analog fluid in an experimental setup. Therefore, it is of interest whether a linear model can be used to accurately predict the wall shear stress caused by a non-Newtonian fluid such as blood within a stented arterial segment. The present work compares the resulting wall shear stress obtained using two linear and one nonlinear model under the same flow waveform. All numerical models are fully three-dimensional, transient, and incorporate a realistic stent geometry. It is shown that traditional linear models (based on blood's lowest viscosity limit, 3.5 Pa s) underestimate the wall shear stress within a stented arterial segment, which can lead to an overestimation of the risk of restenosis. The second linear model, which uses a characteristic viscosity (based on an average strain rate, 4.7 Pa s), results in higher wall shear stress levels, but which are still substantially below those of the nonlinear model. It is therefore shown that nonlinear models result in more accurate predictions of wall shear stress within a stented arterial segment.
Characterising the rheology of non-Newtonian fluids using PFG-NMR and cumulant analysis.
Blythe, T W; Sederman, A J; Mitchell, J; Stitt, E H; York, A P E; Gladden, L F
2015-06-01
Conventional rheological characterisation using nuclear magnetic resonance (NMR) typically utilises spatially-resolved measurements of velocity. We propose a new approach to rheometry using pulsed field gradient (PFG) NMR which readily extends the application of MR rheometry to single-axis gradient hardware. The quantitative use of flow propagators in this application is challenging because of the introduction of artefacts during Fourier transform, which arise when realistic sampling strategies are limited by experimental and hardware constraints and when particular spatial and temporal resolution are required. The method outlined in this paper involves the cumulant analysis of the acquisition data directly, thereby preventing the introduction of artefacts and reducing data acquisition times. A model-dependent approach is developed to enable the pipe-flow characterisation of fluids demonstrating non-Newtonian power-law rheology, involving the use of an analytical expression describing the flow propagator in terms of the flow behaviour index. The sensitivity of this approach was investigated and found to be robust to the signal-to-noise ratio (SNR) and number of acquired data points, enabling an increase in temporal resolution defined by the SNR. Validation of the simulated results was provided by an experimental case study on shear-thinning aqueous xanthan gum solutions, whose rheology could be accurately characterised using a power-law model across the experimental shear rate range of 1-100 s(-1). The flow behaviour indices calculated using this approach were observed to be within 8% of those obtained using spatially-resolved velocity imaging and within 5% of conventional rheometry. Furthermore, it was shown that the number of points sampled could be reduced by a factor of 32, when compared to the acquisition of a volume-averaged flow propagator with 128 gradient increments, without negatively influencing the accuracy of the characterisation, reducing the
The numerical analysis of non-Newtonian blood flow in human patient-specific left ventricle.
Doost, Siamak N; Zhong, Liang; Su, Boyang; Morsi, Yosry S
2016-04-01
Recently, various non-invasive tools such as the magnetic resonance image (MRI), ultrasound imaging (USI), computed tomography (CT), and the computational fluid dynamics (CFD) have been widely utilized to enhance our current understanding of the physiological parameters that affect the initiation and the progression of the cardiovascular diseases (CVDs) associated with heart failure (HF). In particular, the hemodynamics of left ventricle (LV) has attracted the attention of the researchers due to its significant role in the heart functionality. In this study, CFD owing its capability of predicting detailed flow field was adopted to model the blood flow in images-based patient-specific LV over cardiac cycle. In most published studies, the blood is modeled as Newtonian that is not entirely accurate as the blood viscosity varies with the shear rate in non-linear manner. In this paper, we studied the effect of Newtonian assumption on the degree of accuracy of intraventricular hemodynamics. In doing so, various non-Newtonian models and Newtonian model are used in the analysis of the intraventricular flow and the viscosity of the blood. Initially, we used the cardiac MRI images to reconstruct the time-resolved geometry of the patient-specific LV. After the unstructured mesh generation, the simulations were conducted in the CFD commercial solver FLUENT to analyze the intraventricular hemodynamic parameters. The findings indicate that the Newtonian assumption cannot adequately simulate the flow dynamic within the LV over the cardiac cycle, which can be attributed to the pulsatile and recirculation nature of the flow and the low blood shear rate.
King, D M; Wang, Z; Kendig, J W; Palmer, H J; Holm, B A; Notter, R H
2001-07-01
The bulk shear viscosities of aqueous dispersions of lavaged calf lung surfactant (LS) and its chloroform:methanol extract (CLSE) were measured as a function of concentration, shear rate and temperature. At 10-mg phospholipid per milliliter, dispersions of LS and vortexed CLSE in 0.15 M NaCl (saline) had low viscosities near 1 cp over a range of shear rates from 225 to 1125 s(-1). Lung surfactant viscosity increased with phospholipid concentration and became strongly non-Newtonian with higher values at low shear rates. At 37 degrees C and 40 mg/ml, LS and vortexed CLSE in saline had viscosities of 38 and 34 cp (77 s(-1)) and 12 and 7 cp (770 s(-1)), respectively. Viscosity values for LS and CLSE were dependent on temperature and, at fixed shear, were lower at 23 degrees C than at 37 or 10 degrees C. Hysteresis was also present in viscosity measurements depending on whether shear rate was successively increased or decreased during study. Addition of 5 mM Ca(2+) at 37 degrees C markedly reduced CLSE viscosity at all shear rates and decreased LS viscosity at low shear rates. Dispersion by sonication rather than vortexing increased the viscosity of CLSE at fixed shear, while synthetic phospholipids dispersed by either method had low, relatively Newtonian viscosities. The complex viscous behavior of dispersions of LS and CLSE in saline results from their heterogeneous aggregated microstructure of phospholipids and apoproteins. Viscosity is influenced not only by the aggregate surface area under shear, but also by phospholipid-apoprotein interactions and aggregate structure/deformability. Similar complexities likely affect the viscosities of biologically-derived exogenous surfactant preparations administered to patients in clinical surfactant therapy.
Non-Newtonian hydrodynamics for a dilute granular suspension under uniform shear flow.
Chamorro, Moisés G; Reyes, Francisco Vega; Garzó, Vicente
2015-11-01
We study in this work a steady shearing laminar flow with null heat flux (usually called "uniform shear flow") in a gas-solid suspension at low density. The solid particles are modeled as a gas of smooth hard spheres with inelastic collisions while the influence of the surrounding interstitial fluid on the dynamics of grains is modeled by means of a volume drag force, in the context of a rheological model for suspensions. The model is solved by means of three different but complementary routes, two of them being theoretical (Grad's moment method applied to the corresponding Boltzmann equation and an exact solution of a kinetic model adapted to granular suspensions) and the other being computational (Monte Carlo simulations of the Boltzmann equation). Unlike in previous studies on granular sheared suspensions, the collisional moment associated with the momentum transfer is determined in Grad's solution by including all the quadratic terms in the stress tensor. This theoretical enhancement allows for the detection and evaluation of the normal stress differences in the plane normal to the laminar flow. In addition, the exact solution of the kinetic model gives the explicit form of the velocity moments of the velocity distribution function. Comparison between our theoretical and numerical results shows in general a good agreement for the non-Newtonian rheological properties, the kurtosis (fourth velocity moment of the distribution function), and the velocity distribution of the kinetic model for quite strong inelasticity and not too large values of the (scaled) friction coefficient characterizing the viscous drag force. This shows the accuracy of our analytical results that allows us to describe in detail the flow dynamics of the granular sheared suspension.
Yokuda, Satoru T.; Poloski, Adam P.; Adkins, Harold E.; Casella, Andrew M.; Hohimer, Ryan E.; Karri, Naveen K.; Luna, Maria; Minette, Michael J.; Tingey, Joel M.
2009-05-11
The External Flowsheet Review Team (EFRT) has identified the issues relating to the Waste Treatment and Immobilization Plant (WTP) pipe plugging. Per the review’s executive summary, “Piping that transports slurries will plug unless it is properly designed to minimize this risk. This design approach has not been followed consistently, which will lead to frequent shutdowns due to line plugging.” To evaluate the potential for plugging, testing was performed to determine critical velocities for the complex WTP piping layout. Critical velocity is defined as the point at which a moving bed of particles begins to form on the pipe bottom during slurry-transport operations. Pressure drops across the fittings of the test pipeline were measured with differential pressure transducers, from which the critical velocities were determined. A WTP prototype flush system was installed and tested upon the completion of the pressure-drop measurements. We also provide the data for the overflow relief system represented by a WTP complex piping geometry with a non-Newtonian slurry. A waste simulant composed of alumina (nominally 50 μm in diameter) suspended in a kaolin clay slurry was used for this testing. The target composition of the simulant was 10 vol% alumina in a suspending medium with a yield stress of 3 Pa. No publications or reports are available to confirm the critical velocities for the complex geometry evaluated in this testing; therefore, for this assessment, the results were compared to those reported by Poloski et al. (2008) for which testing was performed for a straight horizontal pipe. The results of the flush test are compared to the WTP design guide 24590-WTP-GPG-M-0058, Rev. 0 (Hall 2006) in an effort to confirm flushing-velocity requirements.
Hayat, Tasawar; Awais, Muhammad; Imtiaz, Amna
2016-01-01
This communication deals with the properties of heat source/sink in a magneto-hydrodynamic flow of a non-Newtonian fluid immersed in a porous medium. Shrinking phenomenon along with the permeability of the wall is considered. Mathematical modelling is performed to convert the considered physical process into set of coupled nonlinear mathematical equations. Suitable transformations are invoked to convert the set of partial differential equations into nonlinear ordinary differential equations which are tackled numerically for the solution computations. It is noted that dual solutions for various physical parameters exist which are analyzed in detail. PMID:27598314
Influence of Dissipation on Heat Transfer During Flow of a Non-Newtonian Fluid in a Porous Channel
NASA Astrophysics Data System (ADS)
Baranov, A. V.; Yunitskii, S. A.
2017-07-01
A study is made of flow and heat transfer during the motion of a non-Newtonian (power-law) fluid in a plane channel filled with porous material. The Brinkman equation is used as the equation of state, and a one-temperature model, in representing the energy equation. Account us taken of dissipative heat releases. The problem is solved for temperature boundary conditions of the first kind. The authors show the influence of dissipation on the development of the temperature profile, and also on the distributions of the local Nusselt number and the mass-mean temperature along the channel.
NASA Astrophysics Data System (ADS)
M. El-Hawary, H.; Mostafa, A. A. Mahmoud; Reda, G. Abdel-Rahman; Abeer, S. Elfeshawey
2014-09-01
The theoretic transformation group approach is applied to address the problem of unsteady boundary layer flow of a non-Newtonian fluid near a stagnation point with variable viscosity and thermal conductivity. The application of a two-parameter group method reduces the number of independent variables by two, and consequently the governing partial differential equations with the boundary conditions transformed into a system of ordinary differential equations with the appropriate corresponding conditions. Two systems of ordinary differential equations have been solved numerically using a fourth-order Runge—Kutta algorithm with a shooting technique. The effects of various parameters governing the problem are investigated.
Ruef, Peter; Gehm, Jutta; Gehm, Lothar; Felbinger, Claudia; Pöschl, Johannes; Kuss, Navina
2014-01-01
The low shear viscometer LS300 permits measurements of viscosity with the same precision of the LS30 but is now fully controlled by the windows based software. That allows to determine viscosity at several shear rates and to establish flow curves enabling determination of the viscosity of non-Newtonian fluids. The viscosity of whole blood of ten adults was determined via flow curves approximated by Casson. The sensitivity of the LS300 was evaluated by determining the viscosity of water at rising temperatures and by establishing flow curves of ten specimen of the same blood sample.
Hayat, Tasawar; Awais, Muhammad; Imtiaz, Amna
2016-01-01
This communication deals with the properties of heat source/sink in a magneto-hydrodynamic flow of a non-Newtonian fluid immersed in a porous medium. Shrinking phenomenon along with the permeability of the wall is considered. Mathematical modelling is performed to convert the considered physical process into set of coupled nonlinear mathematical equations. Suitable transformations are invoked to convert the set of partial differential equations into nonlinear ordinary differential equations which are tackled numerically for the solution computations. It is noted that dual solutions for various physical parameters exist which are analyzed in detail.
Data on the mixing of non-Newtonian fluids by a Rushton turbine in a cylindrical tank.
Khapre, Akhilesh; Munshi, Basudeb
2016-09-01
The paper focuses on the data collected from the mixing of shear thinning non-Newtonian fluids in a cylindrical tank by a Rushton turbine. The data presented are obtained by using Computational Fluid Dynamics (CFD) simulation of fluid flow field in the entire tank volume. The CFD validation data for this study is reported in the research article 'Numerical investigation of hydrodynamic behavior of shear thinning fluids in stirred tank' (Khapre and Munshi, 2015) [1]. The tracer injection method is used for the prediction of mixing time and mixing efficiency of a Rushton turbine impeller.
Liu, Biyue; Tang, Dalin
2011-01-01
The objective of this work is to investigate the effect of non-Newtonian properties of blood on the wall shear stress (WSS) in atherosclerotic coronary arteries using both Newtonian and non-Newtonian models. Numerical simulations were performed to examine how the spatial and temporal WSS distributions are influenced by the stenosis size, blood viscosity, and flow rate. The computational results demonstrated that blood viscosity properties had considerable effect on the magnitude of the WSS, especially where disturbed flow was observed. The WSS distribution is highly non-uniform both temporally and spatially, especially in the stenotic region. The maximum WSS occurred at the proximal side of the stenosis, near the outer wall in the curved artery with no stenosis. The lumen area near the inner wall distal to the stenosis region experienced a lower WSS during the entire cardiac cycle. Among the factors of stenosis size, blood viscosity, and flow rate, the size of the stenosis has the most significant effect on the spatial and temporal WSS distributions qualitatively and quantitatively. PMID:21379375
Secondary flow in a curved artery model with Newtonian and non-Newtonian blood-analog fluids
NASA Astrophysics Data System (ADS)
Najjari, Mohammad Reza; Plesniak, Michael W.
2016-11-01
Steady and pulsatile flows of Newtonian and non-Newtonian fluids through a 180°-curved pipe were investigated using particle image velocimetry (PIV). The experiment was inspired by physiological pulsatile flow through large curved arteries, with a carotid artery flow rate imposed. Sodium iodide (NaI) and sodium thiocyanate (NaSCN) were added to the working fluids to match the refractive index (RI) of the test section to eliminate optical distortion. Rheological measurements revealed that adding NaI or NaSCN changes the viscoelastic properties of non-Newtonian solutions and reduces their shear-thinning property. Measured centerline velocity profiles in the upstream straight pipe agreed well with an analytical solution. In the pulsatile case, secondary flow structures, i.e. deformed-Dean, Dean, Wall and Lyne vortices, were observed in various cross sections along the curved pipe. Vortical structures at each cross section were detected using the d2 vortex identification method. Circulation analysis was performed on each vortex separately during the systolic deceleration phase, and showed that vortices split and rejoin. Secondary flow structures in steady flows were found to be morphologically similar to those in pulsatile flows for sufficiently high Dean number. supported by the George Washington University Center for Biomimetics and Bioinspired Engineering.
Non-Newtonian perspectives on pulsatile blood-analog flows in a 180° curved artery model
NASA Astrophysics Data System (ADS)
van Wyk, Stevin; Prahl Wittberg, Lisa; Bulusu, Kartik V.; Fuchs, Laszlo; Plesniak, Michael W.
2015-07-01
Complex, unsteady fluid flow phenomena in the arteries arise due to the pulsations of the heart that intermittently pumps the blood to the extremities of the body. The many different flow waveform variations observed throughout the arterial network are a result of this process and a function of the vessel properties. Large scale secondary flow structures are generated throughout the aortic arch and larger branches of the arteries. An experimental 180° curved artery test section with physiological inflow conditions was used to validate the computational methods implemented in this study. Good agreement of the secondary flow structures is obtained between experimental and numerical studies of a Newtonian blood-analog fluid under steady-state and pulsatile, carotid artery flow rate waveforms. Multiple vortical structures, some of opposite rotational sense to Dean vortices, similar to Lyne-type vortices, were observed to form during the systolic portion of the pulse. Computational tools were used to assess the effect of blood-analog fluid rheology (i.e., Newtonian versus non-Newtonian). It is demonstrated that non-Newtonian, blood-analog fluid rheology results in shear layer instabilities that alter the formation of vortical structures during the systolic deceleration and onwards during diastole. Additional vortices not observed in the Newtonian cases appear at the inside and outside of the bend at various times during the pulsation. The influence of blood-analog shear-thinning viscosity decreases mean pressure losses in contrast to the Newtonian blood analog fluid.
NASA Astrophysics Data System (ADS)
van Wyk, Stevin; Prahl Wittberg, Lisa; Fuchs, Laszlo; Bulusu, Kartik V.; Plesniak, Michael W.
2013-11-01
The purpose of this study is to investigate the development of vortical flow structures of blood like fluids in a 180 degree tube bend, analogous to the aortic arch. Cardiovascular diseases are localized to regions of curvature in the arterial tree. The pathology of atherogenesis is widely considered an inflammatory response, hypothesized to be modulated by the interplay between Wall Shear Stress (WSS) variations and particulate transport mechanisms from the bulk fluid core to the near wall. The WSS is determined by the local flow characteristics as well as the rheological properties of the blood, which in turn are dependent on the bulk secondary flows. In this work, the time dependent fluid flow under various physiological flow conditions are investigated both experimentally and numerically. A Newtonian blood analog fluid model is considered in both studies to validate both methods and thereby study flow structure development during steady as well as pulsatile conditions. Particle image velocimetry (2C - 2D PIV) is used to acquire velocity field data from an acrylic tube bend. The numerical study is extended to consider the non-Newtonian properties of blood according to an empirical model to identify the relative importance of the non-Newtonian behavior. The studies show complex Dean and Lyne vortex interaction that are enhanced with increasing peak Reynolds numbers.
Soares, Armando A; Gonzaga, Sílvia; Oliveira, Carlos; Simões, André; Rouboa, Abel I
2017-06-01
Hemodynamic in abdominal aorta bifurcation was investigated in a real case using computational fluid dynamics. A Newtonian and non-Newtonian (Walburn-Schneck) viscosity models were compared. The geometrical model was obtained by 3D reconstruction from CT-scan and hemodynamic parameters obtained by laser-Doppler. Blood was assumed incompressible fluid, laminar flow in transient regime and rigid vessel wall. Finite volume-based was used to study the velocity, pressure, wall shear stress (WSS) and viscosity throughout cardiac cycle. Results obtained with Walburn-Schneck's model, during systole, present lower viscosity due to shear thinning behavior. Furthermore, there is a significant difference between the results obtained by the two models for a specific patient. During the systole, differences are more pronounced and are preferably located in the tortuous regions of the artery. Throughout the cardiac cycle, the WSS amplitude between the systole and diastole is greater for the Walburn-Schneck's model than for the Newtonian model. However, the average viscosity along the artery is always greater for the non-Newtonian model, except in the systolic peak. The hemodynamic model is crucial to validate results obtained with CFD and to explore clinical potential.
Bandopadhyay, Aditya; Chakraborty, Suman
2015-03-21
By considering an ion moving inside an imaginary sphere filled with a power-law fluid, we bring out the implications of the fluid rheology and the influence of the proximity of the other ions towards evaluating the conduction current in an ionic solution. We show that the variation of the conductivity as a function of the ionic concentration is both qualitatively and quantitatively similar to that predicted by the Kohlrausch law. We then utilize this consideration for estimating streaming potentials developed across narrow fluidic confinements as a consequence of the transport of ions in a convective medium constituting a power-law fluid. These estimates turn out to be in sharp contrast to the classical estimates of streaming potential for non-Newtonian fluids, in which the effect of rheology of the solvent is merely considered to affect the advection current, disregarding its contributions to the conduction current. Our results have potential implications of devising a new paradigm of consistent estimation of streaming potentials for non-Newtonian fluids, with combined considerations of the confinement effect and fluid rheology in the theoretical calculations.
MHD mixed convection analysis of non-Newtonian power law fluid in an open channel with round cavity
NASA Astrophysics Data System (ADS)
Bose, Pritom; Rakib, Tawfiqur; Das, Sourav; Rabbi, Khan Md.; Mojumder, Satyajit
2017-06-01
In this study, magneto-hydrodynamic (MHD) mixed convection flow through a channel with a round cavity at bottom wall using non-Newtonian power law fluid is analysed numerically. The cavity is kept at uniformly high temperature whereas rest of the bottom wall is insulated and top wall of the channel is maintained at a temperature lower than cavity temperature. Grid independency test and code validation are performed to justify the computational accuracy before solving the present problem. Galerkin weighted residual method is appointed to solve the continuity, momentum and energy equations. The problem is solved for wide range of pertinent parameters like Rayleigh number (Ra= 103 - 105), Hartmann number (Ha= 0 - 60) and power law index (n= 0.5 - 1.5) at constant Richardson number Ri= 1.0. The flow and thermal field have been thoroughly discussed through streamline and isothermal lines respectively. The heat transfer performance of the given study is illustrated by average Nusselt number plots. Result of this investigation indicates that heat transfer is highest for dilatant fluids at this configuration and they perform better (47% more heat transfer) in absence of magnetic field. The retardation of heat transfer is offset by shear thickening nature of non-Newtonian fluid.
Nam, Jeonghun; Lim, Hyunjung; Kim, Dookon; Jung, Hyunwook; Shin, Sehyun
2012-04-07
Pure separation and sorting of microparticles from complex fluids are essential for biochemical analyses and clinical diagnostics. However, conventional techniques require highly complex and expensive labeling processes for high purity separation. In this study, we present a simple and label-free method for separating microparticles with high purity using the elasto-inertial characteristic of a non-Newtonian fluid in microchannel flow. At the inlet, particle-containing sample flow was pushed toward the side walls by introducing sheath fluid from the center inlet. Particles of 1 μm and 5 μm in diameter, which were suspended in viscoelastic fluid, were successfully separated in the outlet channels: larger particles were notably focused on the centerline of the channel at the outlet, while smaller particles continued flowing along the side walls with minimal lateral migration towards the centerline. The same technique was further applied to separate platelets from diluted whole blood. Through cytometric analysis, we obtained a purity of collected platelets of close to 99.9%. Conclusively, our microparticle separation technique using elasto-inertial forces in non-Newtonian fluid is an effective method for separating and collecting microparticles on the basis of size differences with high purity. This journal is © The Royal Society of Chemistry 2012
Bandopadhyay, Aditya; Chakraborty, Suman
2011-10-04
In this work, we explore the possibilities of utilizing the combined consequences of interfacial electrokinetics and rheology toward augmenting the energy transfer efficiencies in narrow fluidic confinements. In particular, we consider the exploitation of steric effects (i.e., effect of finite size of the ionic species) in non-Newtonian fluids over small scales, to report dramatic augmentations in the streaming potential, for shear-thickening fluids. We first derive an expression for the streaming potential considering strong electrical double layer interactions in the confined flow passage and the consequences of the finite conductance of the Stern layer, going beyond the Debye-Hückel limit. With a detailed accounting for the excluded volume effects of the ionic species and their interaction with pertinent interfacial phenomena of special type of rheological fluids such as the power law fluids in the above-mentioned formalism, we demonstrate that a confluence of the steric interactions with the non-Newtonian transport characteristics may result in giant augmentations in the energy transfer efficiency for shear-thickening fluids under appropriate conditions. © 2011 American Chemical Society
NASA Astrophysics Data System (ADS)
Rabbi, Khan Md.; Rakib, Tawfiqur; Das, Sourav; Mojumder, Satyajit; Saha, Sourav
2016-07-01
This paper demonstrates magneto-hydrodynamic (MHD) mixed convection flow through a channel with a rectangular obstacle at the entrance region using non-Newtonian power law fluid. The obstacle is kept at uniformly high temperature whereas the inlet and top wall of the channel are maintained at a temperature lower than obstacle temperature. Poiseuille flow is implemented as the inlet velocity boundary condition. Grid independency test and code validation are performed to justify the computational accuracy before solving the present problem. Galerkin weighted residual method has been appointed to solve the continuity, momentum and energy equations. The problem has been solved for wide range of pertinent parameters like Richardson number (Ri = 0.1 - 10) at a constant Reynolds number (Re = 100), Hartmann number (Ha = 0 - 100), power index (n = 0.6 - 1.6). The flow and thermal field have been thoroughly discussed through streamline and isothermal lines respectively. The heat transfer performance of the given study has been illustrated by average Nusselt number plots. It is observed that increment of Hartmann number (Ha) tends to decrease the heat transfer rate up to a critical value (Ha = 20) and then let increase the heat transfer performance. Thus maximum heat transfer rate has been recorded for higher Hartmann number and Rayleigh number in case of pseudo-plastic (n = 0.6) non-Newtonian fluid flow.
NASA Astrophysics Data System (ADS)
Rabbi, Khan Md.; Shuvo, Moinuddin; Kabir, Rabiul Hasan; Mojumder, Satyajit; Saha, Sourav
2016-07-01
Mixed convection in a lid-driven square enclosure with a rotating cylinder inside has been analyzed using non-Newtonian ferrofluid (Fe3O4-water). Left vertical wall is heated while the right vertical wall is kept cold. Bottom wall and cylinder surface are assumed to be adiabatic. Top wall has a moving lid with a constant velocity U0. Galerkin method of finite element analysis has been used to solve the governing equations. Numerical accuracy of solution is ensured by the grid independency test. A variety of Richardson number (Ri = 0.1 - 10) at a governing Reynolds number (Re = 100), power law index (n = 0.5 - 1.5), rotational speed (Ω = 0 - 15) and solid volume fraction of ferrous particles (φ = 0 - 0.05) are employed for this present problem. To illustrate flow and thermal field, streamline and isotherms are included. Average Nusselt number plots are shown to show overall heat transfer rate. It is observed that better heat transfer is achieved at higher rotational speed (Ω), Richardson number (Ri) and power law index (n). This paper also concludes significant variation in streamline and isotherm patterns for higher solid volume fraction (φ) of non-Newtonian ferrofluid.
Finite-sized gas bubble motion in a blood vessel: Non-Newtonian effects
NASA Astrophysics Data System (ADS)
Mukundakrishnan, Karthik; Ayyaswamy, Portonovo S.; Eckmann, David M.
2008-09-01
We have numerically investigated the axisymmetric motion of a finite-sized nearly occluding air bubble through a shear-thinning Casson fluid flowing in blood vessels of circular cross section. The numerical solution entails solving a two-layer fluid model—a cell-free layer and a non-Newtonian core together with the gas bubble. This problem is of interest to the field of rheology and for gas embolism studies in health sciences. The numerical method is based on a modified front-tracking method. The viscosity expression in the Casson model for blood (bulk fluid) includes the hematocrit [the volume fraction of red blood cells (RBCs)] as an explicit parameter. Three different flow Reynolds numbers, Reapp=ρlUmaxd/μapp , in the neighborhood of 0.2, 2, and 200 are investigated. Here, ρl is the density of blood, Umax is the centerline velocity of the inlet Casson profile, d is the diameter of the vessel, and μapp is the apparent viscosity of whole blood. Three different hematocrits have also been considered: 0.45, 0.4, and 0.335. The vessel sizes considered correspond to small arteries, and small and large arterioles in normal humans. The degree of bubble occlusion is characterized by the ratio of bubble to vessel radius (aspect ratio), λ , in the range 0.9⩽λ⩽1.05 . For arteriolar flow, where relevant, the Fahraeus-Lindqvist effects are taken into account. Both horizontal and vertical vessel geometries have been investigated. Many significant insights are revealed by our study: (i) bubble motion causes large temporal and spatial gradients of shear stress at the “endothelial cell” (EC) surface lining the blood vessel wall as the bubble approaches the cell, moves over it, and passes it by; (ii) rapid reversals occur in the sign of the shear stress (+ → - → +) imparted to the cell surface during bubble motion; (iii) large shear stress gradients together with sign reversals are ascribable to the development of a recirculation vortex at the rear of the bubble
Can we approximate non-Newtonian rheology to model mantle convection?
NASA Astrophysics Data System (ADS)
Hüttig, Christian; Plesa, Ana-Catalina; Tosi, Nicola; Breuer, Doris
2014-05-01
One of the most important parameters in mantle convection studies is the rheology since it is directly responsible for the convective vigor, heat transport and shape of up- and downwellings. Deformation in terrestrial mantles is accommodated by two main deformation mechanisms: diffusion and dislocation creep. While the former probably plays a dominant role at high pressures, the latter is thought to be important at relatively low pressures, as inferred by seismic anisotropy of the Earth's upper mantle [1]. Dislocation creep is more challenging to handle than diffusion creep as the viscosity becomes strain-rate dependent [2], introducing a strong non-linearity that requires much longer computational times. In order to avoid this additional complexity, a Newtonian rheology (i.e. diffusion creep) with reduced activation parameters is often used to mimic non-Newtonian behaviour as described in [3], although this approximation has never been carefully tested for a stagnant-lid regime. Mobile-lid steady-state simulations presented in [3] show that the reduction of the activation parameters should be applied with care and in dependence of the problem considered (e.g., amount of internal heating, pressure- or temperature-dominated viscosity). Nevertheless, this simplification is widely employed in convection studies assuming its presumed general validity (e.g. [4,5]). We perform numerical simulations in 2D Cartesian, cylindrical and 3D spherical geometry using the mantle convection codes YACC [6] and Gaia [7] to investigate the consequences of this simplification for various scenarios. To verify our methods, we rerun some of the cases from [3] finding a good agreement. Using rheological parameters from [2] and the approximation from [3], our results show that some global properties such as mean temperature, root mean square velocity and nusselt number are indeed similar (within ~10%) to those obtained when employing a fully non-linear rheology. However, the mantle
Mathematical modeling of slope flows with entrainment as flows of non-Newtonian fluids
NASA Astrophysics Data System (ADS)
Zayko, Julia; Eglit, Margarita
2015-04-01
Non-Newtonian fluids in which the shear stresses are nonlinear functions of the shear strain rates are used to model slope flows such as snow avalanches, mudflows, debris flows. The entrainment of bottom material is included into the model basing on the assumption that in entraining flows the bed friction is equal to the shear stress of the bottom material (Issler et al, 2011). Unsteady motion down long homogeneous slopes with constant inclines is studied numerically for different flow rheologies and different slope angles. Variation of the velocity profile, increase of the flow depth and velocity due to entrainment as well as the value of the entrainment rate is calculated. Asymptotic formulae for the entrainment rate are derived for unsteady flows of different rheological properties. REFERENCES Chowdhury M., Testik F., 2011. Laboratory testing of mathematical models for high-concentration fluid mud turbidity currents. Ocean Engineering 38, 256-270. Eglit, M.E., Demidov, K.S., 2005. Mathematical modeling of snow entrainment in avalanche motion. Cold Reg. Sci. Technol. 43 (1-2), 10-23. Eglit M. E., Yakubenko A. E., 2012, Mathematical Modeling of slope flows entraining bottom material. Eglit M. E., Yakubenko A. E., 2014, Numerical modeling of slope flows entraining bottom material. Cold Reg. Sci. Technol. 108, 139-148. Issler D, M. Pastor Peréz. 2011. Interplay of entrainment and rheology in snow avalanches; a numerical study. Annals of Glaciology, 52(58), pp.143-147 Kern M. A., Tiefenbacher F., McElwaine J., N., 2004. The rheology of snow in large chute flows. Cold Regions Science and Technology, 39, 181 -192. Naaim, M., Faug, T., Naaim-Bouvet, F., 2003. Dry granular flow modelling including erosion and deposition. Surv. Geophys. 24, 569-585. Naaim, M., Naaim-Bouvet, F., Faug, T., Bouchet, A., 2004. Dense snow avalanche modeling: flow, erosion, deposition and obstacle effects. Cold Reg. Sci. Technol. 39, 193-204. Rougier, J & Kern, M 2010, 'Predicting snow
Finite-sized gas bubble motion in a blood vessel: non-Newtonian effects.
Mukundakrishnan, Karthik; Ayyaswamy, Portonovo S; Eckmann, David M
2008-09-01
We have numerically investigated the axisymmetric motion of a finite-sized nearly occluding air bubble through a shear-thinning Casson fluid flowing in blood vessels of circular cross section. The numerical solution entails solving a two-layer fluid model--a cell-free layer and a non-Newtonian core together with the gas bubble. This problem is of interest to the field of rheology and for gas embolism studies in health sciences. The numerical method is based on a modified front-tracking method. The viscosity expression in the Casson model for blood (bulk fluid) includes the hematocrit [the volume fraction of red blood cells (RBCs)] as an explicit parameter. Three different flow Reynolds numbers, Reapp=rholUmaxdmicroapp , in the neighborhood of 0.2, 2, and 200 are investigated. Here, rhol is the density of blood, Umax is the centerline velocity of the inlet Casson profile, d is the diameter of the vessel, and microapp is the apparent viscosity of whole blood. Three different hematocrits have also been considered: 0.45, 0.4, and 0.335. The vessel sizes considered correspond to small arteries, and small and large arterioles in normal humans. The degree of bubble occlusion is characterized by the ratio of bubble to vessel radius (aspect ratio), lambda , in the range 0.9< or =lambda< or =1.05 . For arteriolar flow, where relevant, the Fahraeus-Lindqvist effects are taken into account. Both horizontal and vertical vessel geometries have been investigated. Many significant insights are revealed by our study: (i) bubble motion causes large temporal and spatial gradients of shear stress at the "endothelial cell" (EC) surface lining the blood vessel wall as the bubble approaches the cell, moves over it, and passes it by; (ii) rapid reversals occur in the sign of the shear stress (+ --> - --> +) imparted to the cell surface during bubble motion; (iii) large shear stress gradients together with sign reversals are ascribable to the development of a recirculation vortex at the
Stewart, Charles W.; Meyer, Perry A.; Kurath, Dean E.; Barnes, Steven M.
2006-03-02
The Waste Treatment Plant (WTP) under construction at the Hanford Site will use pulse jet mixer (PJM) technology for mixing and gas retention control applications in tanks expected to contain waste slurries exhibiting a non-Newtonian rheology. This paper presents the results of theoretical and experimental studies performed to establish the methodology to perform reduced-scale gas retention and release tests with PJM systems in non-Newtonian fluids with gas generation. The technical basis for scaled testing with unsteady jet mixing systems in gas-generating non-Newtonian fluids is presented in the form of a bubble migration model that accounts for the gas generation rate, the average bubble rise velocity, and the geometry of the vessel. Scaling laws developed from the model were validated with gas holdup and release tests conducted at three scales: large scale, 1/4 scale, and 1/9 scale. Experiments were conducted with two non-Newtonian simulants with in-situ gas generation by decomposition of hydrogen peroxide. The data were compared non-dimensionally, and the important scale laws were examined. From these results, scaling laws are developed which allow the design of mixing systems at a reduced scale.
Khali, S; Nebbali, R; Ameziani, D E; Bouhadef, K
2013-05-01
In this work the instability of the Taylor-Couette flow for Newtonian and non-Newtonian fluids (dilatant and pseudoplastic fluids) is investigated for cases of finite aspect ratios. The study is conducted numerically using the lattice Boltzmann method (LBM). In many industrial applications, the apparatuses and installations drift away from the idealized case of an annulus of infinite length, and thus the end caps effect can no longer be ignored. The inner cylinder is rotating while the outer one and the end walls are maintained at rest. The lattice two-dimensional nine-velocity (D2Q9) Boltzmann model developed from the Bhatnagar-Gross-Krook approximation is used to obtain the flow field for fluids obeying the power-law model. The combined effects of the Reynolds number, the radius ratio, and the power-law index n on the flow characteristics are analyzed for an annular space of finite aspect ratio. Two flow modes are obtained: a primary Couette flow (CF) mode and a secondary Taylor vortex flow (TVF) mode. The flow structures so obtained are different from one mode to another. The critical Reynolds number Re(c) for the passage from the primary to the secondary mode exhibits the lowest value for the pseudoplastic fluids and the highest value for the dilatant fluids. The findings are useful for studies of the swirling flow of non-Newtonians fluids in axisymmetric geometries using LBM. The flow changes from the CF to TVF and its structure switches from the two-cells to four-cells regime for both Newtonian and dilatant fluids. Contrariwise for pseudoplastic fluids, the flow exhibits 2-4-2 structure passing from two-cells to four cells and switches again to the two-cells configuration. Furthermore, the critical Reynolds number presents a monotonic increase with the power-law index n of the non-Newtonian fluid, and as the radius ratio grows, the transition flow regimes tend to appear for higher critical Reynolds numbers.
Self-similarity of solitary waves on inertia-dominated falling liquid films.
Denner, Fabian; Pradas, Marc; Charogiannis, Alexandros; Markides, Christos N; van Wachem, Berend G M; Kalliadasis, Serafim
2016-03-01
We propose consistent scaling of solitary waves on inertia-dominated falling liquid films, which accurately accounts for the driving physical mechanisms and leads to a self-similar characterization of solitary waves. Direct numerical simulations of the entire two-phase system are conducted using a state-of-the-art finite volume framework for interfacial flows in an open domain that was previously validated against experimental film-flow data with excellent agreement. We present a detailed analysis of the wave shape and the dispersion of solitary waves on 34 different water films with Reynolds numbers Re=20-120 and surface tension coefficients σ=0.0512-0.072 N m(-1) on substrates with inclination angles β=19°-90°. Following a detailed analysis of these cases we formulate a consistent characterization of the shape and dispersion of solitary waves, based on a newly proposed scaling derived from the Nusselt flat film solution, that unveils a self-similarity as well as the driving mechanism of solitary waves on gravity-driven liquid films. Our results demonstrate that the shape of solitary waves, i.e., height and asymmetry of the wave, is predominantly influenced by the balance of inertia and surface tension. Furthermore, we find that the dispersion of solitary waves on the inertia-dominated falling liquid films considered in this study is governed by nonlinear effects and only driven by inertia, with surface tension and gravity having a negligible influence.
Deposition Velocities of Newtonian and Non-Newtonian Slurries in Pipelines
Poloski, Adam P.; Adkins, Harold E.; Abrefah, John; Casella, Andrew M.; Hohimer, Ryan E.; Nigl, Franz; Minette, Michael J.; Toth, James J.; Tingey, Joel M.; Yokuda, Satoru T.
2009-03-01
correlation used in the WTP design guide has been shown to be inaccurate for Hanford waste feed materials. The use of the Thomas (1979) correlation in the design guide is not conservative—In cases where 100% of the particles are smaller than 74 μm or particles are considered to be homogeneous due to yield stress forces suspending the particles the homogeneous fraction of the slurry can be set to 100%. In such cases, the predicted critical velocity based on the conservative Oroskar and Turian (1980) correlation is reduced to zero and the design guide returns a value from the Thomas (1979) correlation. The measured data in this report show that the Thomas (1979) correlation predictions often fall below that measured experimental values. A non-Newtonian deposition velocity design guide should be developed for the WTP— Since the WTP design guide is limited to Newtonian fluids and the WTP expects to process large quantities of such materials, the existing design guide should be modified address such systems. A central experimental finding of this testing is that the flow velocity required to reach turbulent flow increases with slurry rheological properties due to viscous forces dampening the formation of turbulent eddies. The flow becomes dominated by viscous forces rather than turbulent eddies. Since the turbulent eddies necessary for particle transport are not present, the particles will settle when crossing this boundary called the transitional deposition boundary. This deposition mechanism should be expected and designed for in the WTP.
Janečka, Adam Průša, Vít
2015-04-28
We discuss the benefits of using the so-called implicit type constitutive relations introduced by K. R. Rajagopal, J. Fluid Mech. 550, 243-249 (2006) and K. R. Rajagopal, Appl. Math. 48, 279-319 (2003) in the description of the behaviour of non-Newtonian fluids. In particular, we focus on the benefits of using the implicit type constitutive relations in the mathematical modelling of fluids in which the shear stress/shear rate dependence is given by an S-shaped curve, and in modelling of fluids that exhibit nonzero normal stress differences. We also discuss a thermodynamical framework that allows one to cope with the implicit type constitutive relations.
Yih, K.A.
1998-10-01
Convective heat transfer in a porous medium has a number of thermal engineering applications such as ceramic processing, nuclear reactor cooling system, crude oil drilling, chemical reactor design, ground water pollution and filtration processes. In this paper, the authors have investigated a boundary layer analysis for uniform lateral mass flux effect on natural convection of non-Newtonian power-law fluids along an isothermal or isoflux vertical cone embedded in a porous medium. Numerical results for the dimensionless temperature profiles as well as the local Nusselt number are presented for the mass flux parameter, viscosity index n and geometry shape parameter {lambda}. The local surface heat transfer increases for the case withdrawal of fluid, the increase of the value of {lambda}. The local Nusselt number is found to be significantly affected by the surface mass flux than the viscosity index.
The use of a non-Newtonian fluid to visualize the mixing of a pseudo-homogeneous slurry
Pullum, L.; Welsh, M.C.; Hamilton, N.; Baillie, K.; Kam, P.
1994-12-31
The efficient mixing of suspensions is important t many mineral processing extraction operations. A flow visualization study was undertaken by CSIRO using a pseudo-plastic yield stress fluid in a one-ninth scale model mixing vessel with impellers. The non-Newtonian viscosity characteristics of the model fluid matched those of a slurry encountered in the alumina industry. Flow visualization showed that the fluid foil blades on the impellers were stalled and generated radial flows rather than axial flows, leading to massive scaling in the mixing vessel. Repositioning the impellers brought the blades out of stall and oiled to near ideal mixing. Subsequent installation of the modified agitator configuration in the full size vessel confirmed the scale model results.
NASA Astrophysics Data System (ADS)
Nabwey, Hossam A.; Boumazgour, Mohamed; Rashad, A. M.
2017-03-01
The group method analysis is applied to study the steady mixed convection stagnation-point flow of a non-Newtonian nanofluid towards a vertical stretching surface. The model utilized for the nanofluid incorporates the Brownian motion and thermophoresis effects. Applying the one-parameter transformation group which reduces the number of independent variables by one and thus, the system of governing partial differential equations has been converted to a set of nonlinear ordinary differential equations, and these equations are then computed numerically using the implicit finite-difference scheme. Comparison with previously published studies is executed and the results are found to be in excellent agreement. Results for the velocity, temperature, and the nanoparticle volume fraction profiles as well as the local skin-friction coefficient and local Nusselt number are presented in graphical and tabular forms, and discussed for different values of the governing parameters to show interesting features of the solutions.
NASA Astrophysics Data System (ADS)
Nabwey, Hossam A.; Boumazgour, Mohamed; Rashad, A. M.
2017-07-01
The group method analysis is applied to study the steady mixed convection stagnation-point flow of a non-Newtonian nanofluid towards a vertical stretching surface. The model utilized for the nanofluid incorporates the Brownian motion and thermophoresis effects. Applying the one-parameter transformation group which reduces the number of independent variables by one and thus, the system of governing partial differential equations has been converted to a set of nonlinear ordinary differential equations, and these equations are then computed numerically using the implicit finite-difference scheme. Comparison with previously published studies is executed and the results are found to be in excellent agreement. Results for the velocity, temperature, and the nanoparticle volume fraction profiles as well as the local skin-friction coefficient and local Nusselt number are presented in graphical and tabular forms, and discussed for different values of the governing parameters to show interesting features of the solutions.
Trejo-Soto, C; Costa-Miracle, E; Rodriguez-Villarreal, I; Cid, J; Castro, M; Alarcon, T; Hernandez-Machado, A
2017-04-04
We introduce a new framework to study the non-Newtonian behaviour of fluids at the microscale based on the analysis of front advancement. We apply this methodology to study the non-linear rheology of blood in microchannels. We carry out experiments in which the non-linear viscosity of blood samples is quantified at different haematocrits and ages. Under these conditions, blood exhibits a power-law dependence on the shear rate. In order to analyse our experimental data, we put forward a scaling theory which allows us to define an adhesion scaling number. This theory yields a scaling behaviour of the viscosity expressed as a function of the adhesion capillary number. By applying this scaling theory to samples of different ages, we are able to quantify how the characteristic adhesion energy varies as time progresses. This connection between microscopic and mesoscopic properties allows us to estimate quantitatively the change in the cell-cell adhesion energies as the sample ages.
Viscoelastic flows in simple liquids generated by vibrating nanostructures.
Pelton, Matthew; Chakraborty, Debadi; Malachosky, Edward; Guyot-Sionnest, Philippe; Sader, John E
2013-12-13
Newtonian fluid mechanics, in which the shear stress is proportional to the strain rate, is synonymous with the flow of simple liquids such as water. We report the measurement and theoretical verification of non-Newtonian, viscoelastic flow phenomena produced by the high-frequency (20 GHz) vibration of gold nanoparticles immersed in water-glycerol mixtures. The observed viscoelasticity is not due to molecular confinement, but is a bulk continuum effect arising from the short time scale of vibration. This represents the first direct mechanical measurement of the intrinsic viscoelastic properties of simple bulk liquids, and opens a new paradigm for understanding extremely high frequency fluid mechanics, nanoscale sensing technologies, and biophysical processes.
Viscoelastic Flows in Simple Liquids Generated by Vibrating Nanostructures
NASA Astrophysics Data System (ADS)
Pelton, Matthew; Chakraborty, Debadi; Malachosky, Edward; Guyot-Sionnest, Philippe; Sader, John E.
2013-12-01
Newtonian fluid mechanics, in which the shear stress is proportional to the strain rate, is synonymous with the flow of simple liquids such as water. We report the measurement and theoretical verification of non-Newtonian, viscoelastic flow phenomena produced by the high-frequency (20 GHz) vibration of gold nanoparticles immersed in water-glycerol mixtures. The observed viscoelasticity is not due to molecular confinement, but is a bulk continuum effect arising from the short time scale of vibration. This represents the first direct mechanical measurement of the intrinsic viscoelastic properties of simple bulk liquids, and opens a new paradigm for understanding extremely high frequency fluid mechanics, nanoscale sensing technologies, and biophysical processes.
The determination of viscosity at liquid mixtures - Comparison of approaches
NASA Astrophysics Data System (ADS)
Michal, Schmirler; Hana, Netřebská; Jan, Kolínský
2017-09-01
The research of flow field parameters for non-stationary flow of non-Newtonian fluids carried out at the Institute of Fluid Mechanics and Thermodynamics of CTU showed the need for knowledge of determination of the resulting viscosity of a mixture of several liquids. There are several sources for determining viscosity of mixtures. It is possible either to find theoretical relations in the literature or use technical tables based on experimentally measured data. This article focuses on comparing these approaches with an experiment. The experiment was performed by a Rheotest RN 4.1 rotating viscometer produced by the company RHEOTEST Medingen. The research was carried out using a solution of glycerol and water. The research has shown great differences in results in different approaches for determining the viscosity of the liquid mixtures. The result of this paper is to determine the method of viscosity calculation that is closest to the experimental data.
Mondal, Sourav; De, Sirshendu
2013-01-01
Mass transport of a neutral solute for a power law fluid in a porous microtube under electro-osmotic flow regime is characterized in this study. Combined electro-osmotic and pressure driven flow is conducted herein. An analytical solution of concentration profile within mass transfer boundary layer is derived from the first principle. The solute transport through the porous wall is also coupled with the electro-osmotic flow to predict the solute concentration in the permeate stream. The effects of non-Newtonian rheology and the operating conditions on the permeation rate and permeate solute concentration are analyzed in detail. Both cases of assisting (electro-osmotic and poiseulle flow are in same direction) and opposing flow (the individual flows are in opposite direction) cases are taken care of. Enhancement of Sherwood due to electro-osmotic flow for a non-porous conduit is also quantified. Effects if non-Newtonian rheology on Sherwood number enhancement are observed. PMID:24404046
NASA Astrophysics Data System (ADS)
Kwack, JaeHyuk; Masud, Arif
2014-04-01
This paper presents a stabilized mixed finite element method for shear-rate dependent fluids. The nonlinear viscosity field is a function of the shear-rate and varies uniformly in space and in time. The stabilized form is developed via application of Variational Multiscale (VMS) framework to the underlying generalized Navier-Stokes equation. Linear and quadratic tetrahedral and hexahedral elements are employed with equal-order interpolations for the velocity and pressure fields. A variety of benchmark problems are solved to assess the stability and accuracy properties of the resulting method. The method is then applied to non-Newtonian shear-rate dependent flows in bifurcating artery geometry, and significant non-Newtonian fluid effects are observed. A comparative study of the proposed method shows that the additional computational costs due to the nonlinear shear-rate dependent viscosity are only ten percent more than the computational cost for a Newtonian model.
Numerical Modeling of Mixing of Chemically Reacting, Non-Newtonian Slurry for Tank Waste Retrieval
D.A. Yuen; Y. Onishi; J.R. Rustand; B.E. Wells; T.E. Michener; A.R. Felmy; D.S. Trent; A.A. Ten; C.A. Hier
2002-02-06
Fifty-four million gallons of wastes containing 180-million curies of radioactivity are stored in single (SSTs)- and double-shell underground tanks (DSTs) at the U.S. Department of Energy's Hanford Site in eastern Washington (Gephart and Lundgren 1997). They are a multiphase, multicomponent, high-ionic strength, and highly basic mixture of liquids, solids, and, in some cases, gases. Mixer pumps will be installed in twenty-eight 4,0000-m DSTs to stir radioactive sludge/saltcake and supernatant liquid (and possibly a solvent) so the waste can be retrieved from the tanks for subsequent treatment and disposal. During the retrieval operation, complex interactions occur between waste mixing, chemical reactions, and rheology. Thus, decisions made about waste retrieval must account for these complex interactions.
Nandy, S; Tarbell, J M
1987-01-01
Wall shear stress has been measured by flush-mounted hot film anemometry distal to an Ionescu-Shiley tri-leaflet valve under pulsatile flow conditions. Both Newtonian (aqueous glycerol) and non-Newtonian (aqueous polyacrylamide) blood analog fluids were investigated. Significant differences in the axial distribution of wall shear stress between the two fluids are apparent in flows having nearly identical Reynolds numbers. The Newtonian fluid exhibits a (peak) wall shear rate which is maximized near the valve seat (30 mm) and then decays to a fully developed flow value (by 106 mm). In contrast, the shear rate of the non-Newtonian fluid at 30 mm is less than half that of the Newtonian fluid and at 106 mm is more than twice that of the Newtonian fluid. It is suggested that non-Newtonian rheology influences valve flow patterns either through alterations in valve opening associated with low shear separation zones behind valve leaflets, or because of variations in the rate of jet spreading. More detailed studies are required to clarify the mechanisms. The Newtonian wall shear stresses for this valve are low. The highest value observed anywhere in the aortic chamber was 2.85 N/m2 at a peak Reynolds number of 3694.
NASA Astrophysics Data System (ADS)
Khan, Zeeshan; Khan, Muhammad Altaf; Khan, Ilyas; Islam, Saeed; Siddiqui, Nasir
2017-07-01
We have explored double-layer-coated fiber optics using two-phase immiscible non-Newtonian fluid as a polymeric material. We have considered two layers, the first layer is assumed of soft material and the second consists of hard material. Resin flows are driven by fast-moving glass fiber and the pressurization at the coating die inlet. Two cases of temperature linearly varying at the boundaries have been discussed. The assumption of fully developed flow of non-Newtonian fluid permits an exact solution to the Navier-Stokes equations. The thickness of the secondary coating resin and the shear stress on the glass fiber, which are two basic output variables of practical concern, have been examined by several input parameters: two geometric parameters, i.e., radius of the glass fiber Rw and radius of the coating die Rd; two operational parameters, i.e., the velocity ratio U and power indices n1,2; the non-Newtonian parameter S1,2; and the nondimensional parameters H and ϕ. The comparison of the present work with published result predicts the close agreement.
Amiri Delouei, A; Nazari, M; Kayhani, M H; Succi, S
2014-05-01
In this study, the immersed boundary-thermal lattice Boltzmann method has been used to simulate non-Newtonian fluid flow over a heated circular cylinder. The direct-forcing algorithm has been employed to couple the off-lattice obstacles and on-lattice fluid nodes. To investigate the effect of boundary sharpness, two different diffuse interface schemes are considered to interpolate the velocity and temperature between the boundary and computational grid points. The lattice Boltzmann equation with split-forcing term is applied to consider the effects of the discrete lattice and the body force to the momentum flux, simultaneously. A method for calculating the Nusselt number based on diffuse interface schemes is developed. The rheological and thermal properties of non-Newtonian fluids are investigated under the different power-law indices and Reynolds numbers. The effect of numerical parameters on the accuracy of the proposed method has been investigated in detail. Results show that the rheological and thermal properties of non-Newtonian fluids in the presence of a heated immersed body can be suitably captured using the immersed boundary thermal lattice Boltzmann method.
Etemad, S.G.
1997-11-01
Many important industrial fluids are non-Newtonian in their flow characteristics. These include food materials, soap and detergent slurries, polymer solutions and many others. In the most of the industries such as polymer, foods, petrochemical the heat exchanger is an especially important component of the processing equipment. In the design of heat exchanger, the prediction of the heat transfer coefficient plays a key role as a design factor. Here the Galerkin finite element is used to solve the three dimensional momentum and energy equations for laminar non-Newtonian flow in cross-shaped straight duct. Both flow and heat transfer develop simultaneously from the entrance of the channel. Uniform wall temperature (T) and also constant wall heat flux both axially and peripherally (H2) are used as thermal boundary conditions. The power-law model is chosen to characterize the non-Newtonian behavior of the fluid. The effect of power-law index and geometric parameter on the apparent friction factor as well as Nusselt number are presented and discussed.
NASA Astrophysics Data System (ADS)
Afify, Ahmed A.; El-Aziz, Mohamed Abd
2017-02-01
The steady two-dimensional flow and heat transfer of a non-Newtonian power-law nanofluid over a stretching surface under convective boundary conditions and temperature-dependent fluid viscosity has been numerically investigated. The power-law rheology is adopted to describe non-Newtonian characteristics of the flow. Four different types of nanoparticles, namely copper (Cu), silver (Ag), alumina (Al 2 O 3) and titanium oxide (TiO 2) are considered by using sodium alginate (SA) as the base non-Newtonian fluid. Lie symmetry group transformations are used to convert the boundary layer equations into non-linear ordinary differential equations. The transformed equations are solved numerically by using a shooting method with fourth-order Runge-Kutta integration scheme. The results show that the effect of viscosity on the heat transfer rate is remarkable only for relatively strong convective heating. Moreover, the skin friction coefficient and the rate of heat transfer increase with an increase in Biot number.
NASA Astrophysics Data System (ADS)
Kim, Chang-Beom; Lim, Jaeho; Hong, Hyobong; Kresh, J. Yasha; Wootton, David M.
2015-07-01
Detailed knowledge of the blood velocity distribution over the cross-sectional area of a microvessel is important for several reasons: (1) Information about the flow field velocity gradients can suggest an adequate description of blood flow. (2) Transport of blood components is determined by the velocity profiles and the concentration of the cells over the cross-sectional area. (3) The velocity profile is required to investigate volume flow rate as well as wall shear rate and shear stress which are important parameters in describing the interaction between blood cells and the vessel wall. The present study shows the accurate measurement of non-Newtonian blood velocity profiles at different shear rates in a microchannel using a novel translating-stage optical method. Newtonian fluid velocity profile has been well known to be a parabola, but blood is a non-Newtonian fluid which has a plug flow region at the centerline due to yield shear stress and has different viscosities depending on shear rates. The experimental results were compared at the same flow conditions with the theoretical flow equations derived from Casson non-Newtonian viscosity model in a rectangular capillary tube. And accurate wall shear rate and shear stress were estimated for different flow rates based on these velocity profiles. Also the velocity profiles were modeled and compared with parabolic profiles, concluding that the wall shear rates were at least 1.46-3.94 times higher than parabolic distribution for the same volume flow rate.
NASA Astrophysics Data System (ADS)
Deyranlou, Amin; Niazmand, Hamid; Sadeghi, Mahmood-Reza; Mesri, Yaser
2016-06-01
Blood non-Newtonian behavior on low-density lipoproteins (LDL) accumulation is analyzed numerically, while fluid-multilayered arteries are adopted for nonstenotic and 30%-60% symmetrical stenosed models. Present model considers non-Newtonian effects inside the lumen and within arterial layers simultaneously, which has not been examined in previous studies. Navier-Stokes equations are solved along with the mass transport convection-diffusion equations and Darcy’s model for species transport inside the luminal flow and across wall layers, respectively. Carreau model for the luminal flow and the modified Darcy equation for the power-law fluid within arterial layers are employed to model blood rheological characteristics, appropriately. Results indicate that in large arteries with relatively high Reynolds number Newtonian model estimates LDL concentration patterns well enough, however, this model seriously incompetent for regions with low WSS. Moreover, Newtonian model for plasma underestimates LDL concentration especially on luminal surface and across arterial wall. Therefore, applying non-Newtonian model seems essential for reaching to a more accurate estimation of LDL distribution in the artery. Finally, blood flow inside constricted arteries demonstrates that LDL concentration patterns along the stenoses inside the luminal flow and across arterial layers are strongly influenced as compared to the nonstenotic arteries. Additionally, among four stenosis severity grades, 40% stenosis is prone to more LDL accumulation along the post-stenotic regions.
Vimmr, J; Jonášová, A; Bublík, O
2013-10-01
Considering the fact that hemodynamics plays an important role in the patency and overall performance of implanted bypass grafts, this work presents a numerical investigation of pulsatile non-Newtonian blood flow in three different patient-specific aorto-coronary bypasses. The three bypass models are distinguished from each other by the number of distal side-to-side and end-to-side anastomoses and denoted as single, double and triple bypasses. The mathematical model in the form of time-dependent nonlinear system of incompressible Navier-Stokes equations is coupled with the Carreau-Yasuda model describing the shear-thinning property of human blood and numerically solved using the principle of the SIMPLE algorithm and cell-centred finite volume method formulated for hybrid unstructured tetrahedral grids. The numerical results computed for non-Newtonian and Newtonian blood flow in the three aorto-coronary bypasses are compared and analysed with emphasis placed on the distribution of cycle-averaged wall shear stress and oscillatory shear index. As shown in this study, the non-Newtonian blood flow in all of the considered bypass models does not significantly differ from the Newtonian one. Our observations further suggest that, especially in the case of sequential grafts, the resulting flow field and shear stimulation are strongly influenced by the diameter of the vessels involved in the bypassing. Copyright © 2013 John Wiley & Sons, Ltd.
Nonlinear waves on a liquid film falling down an inclined corrugated surface
NASA Astrophysics Data System (ADS)
Trifonov, Yuri
2017-05-01
In the present study, we performed the direct Navier-Stokes computations on the linear and nonlinear stability of a gravity-driven film flow down an inclined corrugated surface. We focused on the steady-state traveling waves and analyzed their transformations due to the wall corrugations. These solutions have two spatial periods and we have used a double Fourier expansion to compute them. The systematic variations of the Reynolds number and the substrate's periodicity and amplitude were performed in the nonlinear wave analysis. We found that starting from some "critical" values of the Reynolds number, the wall corrugation has a small influence on the film thickness profile of the traveling waves, and it is close to the waves on the liquid film falling down a smooth plate. This "critical" value strongly depends on the substrate's periodicity and amplitude. To our knowledge, this is the first theoretical work where the nonlinear waves on the free surface of a liquid film over the topography is computed using the full Navier-Stokes equations.
Smoothed particle hydrodynamics model of non-aqueous phase liquid flow and dissolution
Tartakovsky, Alexandre M.; Meakin, Paul; Ward, Anderson L.
2009-01-01
A smoothed particle hydrodynamics model was developed to simulate the flow of mixtures of aqueous and non-aqueous phase liquids in porous media and the dissolution of the non-aqueous phase in the aqueous phase. The model was used to study the effects of pore-scale heterogeneity and anisotropy on the steady state dense non-aqueous phase liquid (DNAPL) saturation when gravity driven DNAPL displaces water from initially water saturated porous media. Pore-scale anisotropy was created by using co-oriented non overlapping elliptically shaped grains to represent the porous media. After a steady state DNAPL saturation was reached, water was injected until a new steady state DNAPL saturation was reached. The amount of trapped DNAPL was found to be greater when DNAPL is displaced in the direction of the major axes of the soil grains than when it is displaced in the direction of the minor axes of the soil grains. The amount of trapped DNAPL was also found to increase with decreasing initial saturation of the continuous DNAPL phase. For the conditions used in our simulations, the saturation of the trapped NAPL with a smaller initial DNAPL saturation was more than 3 times larger than the amount of trapped DNAPL with a larger initial saturation. These simulations were carried out assuming that the DNAPL did not dissolve in water. Simulations including the effect of dissolution of DNAPL in the aqueous phase were also performed, and effective (macroscopic) mass transfer coefficients were determined.