Non-Newtonian mechanics of oscillation centers
Dodin, I. Y.; Fisch, N. J.
2008-10-01
Classical particles oscillating in high-frequency or static fields effectively exhibit a modified rest mass meff which determines the oscillation center motion. Unlike the true mass, meff depends on the field parameters and can be a nonanalytic function of the particle average velocity and the oscillation energy; hence non-Newtonian "metaplasmas" that permit a new type of plasma maser, signal rectification, frequency doubling, and one-way walls.
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.
Crossover phenomena in non-Newtonian viscous fingers at a finite viscosity ratio
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.
Simultaneous pulsatile flow and oscillating wall of a non-Newtonian liquid
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.
Directory of Open Access Journals (Sweden)
K.C. Saha
2015-04-01
Full Text Available The effects of MHD free convection heat and mass transfer of power-law Non-Newtonian fluids along a stretching sheet with viscous dissipation has been analyzed. This has been done under the simultaneous action of suction, thermal radiation and uniform transverse magnetic field. The stretching sheet is assumed to continuously moving with a power-law velocity and maintaining a uniform surface heat-flux. The governing non-linear partial differential equations are transformed into non-linear ordinary differential equations, using appropriate similarity transformations and the resulting problem is solved numerically using Nachtsheim-Swigert shooting iteration technique along with sixth order Runge-Kutta integration scheme. A parametric study of the parameters arising in the problem such as the Eckert number due to viscous dissipation, radiation number, buoyancy parameter, Schmidt number, Prandtl number etc are studied and the obtained results are shown graphically and the physical aspects of the problem are discussed.
Kishan, N.; Shashidar Reddy, B.
2013-06-01
The problem of a magneto-hydro dynamic flow and heat transfer to a non-Newtonian power-law fluid flow past a continuously moving flat porous plate in the presence of sucion/injection with heat flux by taking into consideration the viscous dissipation is analysed. The non-linear partial differential equations governing the flow and heat transfer are transformed into non-linear ordinary differential equations using appropriate transformations and then solved numerically by an implicit finite difference scheme. The solution is found to be dependent on various governing parameters including the magnetic field parameter M, power-law index n, suction/injection parameter ƒw, Prandtl number Pr and Eckert number Ec. A systematical study is carried out to illustrate the effects of these major parameters on the velocity profiles, temperature profile, skin friction coefficient and rate of heat transfer and the local Nusslet number.
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.
The flow of a non-Newtonian fluid induced due to the oscillations of a porous plate
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S. Asghar
2004-01-01
Full Text Available An analytic solution of the flow of a third-grade fluid on a porous plate is constructed. The porous plate is executing oscillations in its own plane with superimposed injection or suction. An increasing or decreasing velocity amplitude of the oscillating porous plate is also examined. It is also shown that in case of third-grade fluid, a combination of suction/injection and decreasing/increasing velocity amplitude is possible as well. Several limiting situations with their implications are given and discussed.
Stability Analysis of Non-Newtonian Rimming Flow
Fomin, Sergei; Haine, Peter
2015-01-01
The rimming flow of a viscoelastic thin film inside a rotating horizontal cylinder is studied theoretically. Attention is given to the onset of non-Newtonian free-surface instability in creeping flow. This non-inertial instability has been observed in experiments, but current theoretical models of Newtonian fluids can neither describe its origin nor explain its onset. This study examines two models of non Newtonian fluids to see if the experimentally observed instability can be predicted analytically. The non-Newtonian viscosity and elastic properties of the fluid are described by the Generalized Newtonian Fluid (GNF) and Second Order Viscoelastic Fluid (SOVF) constitutive models, respectively. With linear stability analysis, it is found that, analogously to the Newtonian fluid, rimming flow of viscous non-Newtonian fluids (modeled by GNF) is neutrally stable. However, the viscoelastic properties of the fluid (modeled by SOVF) are found to contribute to the flow destabilization. The instability is shown to in...
Structural Optimization of Non-Newtonian Rectifiers
DEFF Research Database (Denmark)
Jensen, Kristian Ejlebjærg; Okkels, Fridolin
. In this context it is natural to look for other sources of non-linearity and one possibility is to introduce a non-Newtonian working fluid. Non-Newtonian properties are due to stretching of large particles/molecules in the fluid and this is commonly seen for biological samples in “lab-on-a-chip” systems....... The strength of non-Newtonian effects does not depend on the device size. Furthermore a non-Newtonian working fluid removes symmetry properties such that geometry influence is reintroduced, and indeed non-Newtonian effects have been used in experimentally realized microfluidic rectitifiers[1]. The rectifiers...... optimization, which is a kind of design optimization where nothing is assumed about the topology of the design. We will apply a high-level implementation of topology optimization using the density method in a commercial finite element package[2]. However, the modeling of non-Newtonian fluids remains a major...
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.
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.
Rheology and non-Newtonian fluids
Irgens, Fridtjov
2014-01-01
This book gives a brief but thorough introduction to the fascinating subject of non-Newtonian fluids, their behavior and mechanical properties. After a brief introduction of what characterizes non-Newtonian fluids in Chapter 1 some phenomena characteristic of non-Newtonian fluids are presented in Chapter 2. The basic equations in fluid mechanics are discussed in Chapter 3. Deformation kinematics, the kinematics of shear flows, viscometric flows, and extensional flows are the topics in Chapter 4. Material functions characterizing the behavior of fluids in special flows are defined in Chapter 5. Generalized Newtonian fluids are the most common types of non-Newtonian fluids and are the subject in Chapter 6. Some linearly viscoelastic fluid models are presented in Chapter 7. In Chapter 8 the concept of tensors is utilized and advanced fluid models are introduced. The book is concluded with a variety of 26 problems. Solutions to the problems are ready for instructors.
On radial oscillations in viscous accretion discs surrounding neutron stars
Chen, Xingming; Taam, Ronald E.
1992-01-01
Radial oscillations resulting from axisymmetric perturbations in viscous accretion disks surrounding neutron stars in X-ray binary systems have been investigated. Within the framework of the alpha-viscosity model a series of hydrodynamic calculations demonstrates that the oscillations are global for alpha of about 1. On the other hand, for alpha of 0.4 or less, the oscillations are local and confined to the disk boundaries. If viscous stresses acting in the radial direction are included, however, it is found that the disk can be stabilized. The application of such instabilities in accretion disks, without reference to the boundary layer region between the neutron star (or magnetosphere) and the inner edge of the disk, to the phenomenology of quasi-periodic oscillations is brought into question.
Institute of Scientific and Technical Information of China (English)
蒋涛; 任金莲; 徐磊; 陆林广
2014-01-01
为准确、有效地模拟非等温非牛顿黏性流体的流动问题，本文基于一种不含核导数计算的核梯度修正格式和不可压缩条件给出了一种改进光滑粒子动力学(SPH)离散格式，它较传统SPH离散格式具有较高精度和较好稳定性。同时，为准确地描述温度场的演化过程，建立了非牛顿黏性的SPH温度离散模型。通过对等温Poiseuille流、喷射流和非等温Couette流、4：1收缩流进行模拟，并与其他数值结果作对比，分别验证了改进SPH方法模拟非牛顿黏性流动问题的可靠性和提出的SPH温度离散模型求解非等温流动问题的有效性和准确性。随后，运用改进SPH方法结合SPH温度离散模型对环形腔和C形腔内非等温非牛顿黏性流体的充模过程进行了试探性模拟研究，分析了数值模拟的收敛性，讨论了不同位置处热流参数对温度和流动的影响。%In this paper, a corrected smoothed particle hydrodynamics (SPH) method is proposed to solve the problems of non-isothermal non-Newtonian viscous fluid. The proposed particle method is based on the corrected kernel derivative scheme under no kernel derivative and incompressible conditions, which possesses higher accuracy and better stability than the traditional SPH method. Meanwhile, a temperature-discretization scheme is deduced by the concept of SPH method for the purpose of precisely describing the evolutionary process of the temperature field. Reliability of the corrected SPH method for simulating the non-Newtonian viscous fluid flow is demonstrated by simulating the isothermal Poiseuille flow and the jet fluid of filling process; and the validity and accuracy of the proposed SPH discrete scheme in a temperature model for solving the non-isothermal fluid flow are tested by solving the non-isothermal Couette flow and 4:1 contraction flow. Subsequently, the proposed corrected SPH method combined with the SPH temperature
PKN problem for non-Newtonian fluid
Linkov, Alexander
2012-01-01
The paper presents analytical solution for hydraulic fracture driven by a non-Newtonian fluid and propagating under plane strain conditions in cross sections parallel to the fracture front. Conclusions are drawn on the influence of the fluid properties on the fracture propagation.
Effect of a Non-Newtonian Load on Signature S2 for Quartz Crystal Microbalance Measurements
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Jae-Hyeok Choi
2014-01-01
Full Text Available The quartz crystal microbalance (QCM is increasingly used for monitoring the interfacial interaction between surfaces and macromolecules such as biomaterials, polymers, and metals. Recent QCM applications deal with several types of liquids with various viscous macromolecule compounds, which behave differently from Newtonian liquids. To properly monitor such interactions, it is crucial to understand the influence of the non-Newtonian fluid on the QCM measurement response. As a quantitative indicator of non-Newtonian behavior, we used the quartz resonator signature, S2, of the QCM measurement response, which has a consistent value for Newtonian fluids. We then modified De Kee’s non-Newtonian three-parameter model to apply it to our prediction of S2 values for non-Newtonian liquids. As a model, we chose polyethylene glycol (PEG400 with the titration of its volume concentration in deionized water. As the volume concentration of PEG400 increased, the S2 value decreased, confirming that the modified De Kee’s three-parameter model can predict the change in S2 value. Collectively, the findings presented herein enable the application of the quartz resonator signature, S2, to verify QCM measurement analysis in relation to a wide range of experimental subjects that may exhibit non-Newtonian behavior, including polymers and biomaterials.
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.
Electroosmotic mobilities of non-Newtonian fluids
Zhao, Cunlu
2010-01-01
Owing to frequent processing of biofluids in Lab-on-a-chip microfluidic devices, electroosmotic mobilities of non-Newtonian fluids are investigated numerically. The general Cauchy momentum equation governing the electroosmotic velocity is simplified by incorporation of the Gouy-Chapman solution of the Poisson-Boltzmann equation and the Carreau fluid constitutive model. Then the finite element method for solving the simplified version of Cauchy momentum equation is validated through comparisons with two exact solutions, i.e., Newtonian fluids and power-law fluids. Analyses shows that different from Newtonian fluids with a constant dimensionless electroosmotic mobility of unit one, dimensionless electroosmotic mobilities for non-Newtonian Carreau fluids are dependent on four dimensionless groups, such as dimensionless surface zeta potential , Weissenberg number Wi, fluid power-law exponent n and transitional parameter {\\beta}. It is found out that with increasing and decreasing of n and {\\beta}, electroosmotic ...
Non newtonian annular alloy solidification in mould
Energy Technology Data Exchange (ETDEWEB)
Moraga, Nelson O.; Garrido, Carlos P. [Universidad de La Serena, Departamento de Ingenieria Mecanica, La Serena (Chile); Castillo, Ernesto F. [Universidad de Santiago de Chile, Departamento de Ingenieria Mecanica, Santiago (Chile)
2012-08-15
The annular solidification of an aluminium-silicon alloy in a graphite mould with a geometry consisting of horizontal concentric cylinders is studied numerically. The analysis incorporates the behavior of non-Newtonian, pseudoplastic (n=0.2), Newtonian (n=1), and dilatant (n=1.5) fluids. The fluid mechanics and heat transfer coupled with a transient model of convection diffusion are solved using the finite volume method and the SIMPLE algorithm. Solidification is described in terms of a liquid fraction of a phase change that varies linearly with temperature. The final results make it possible to infer that the fluid dynamics and heat transfer of solidification in an annular geometry are affected by the non-Newtonian nature of the fluid, speeding up the process when the fluid is pseudoplastic. (orig.)
Oscillatory Spreading and Surface Instability of a Non-Newtonian Fluid under Compression
Choudhury, Moutushi Dutta; Chandra, Subrata; Nag, Soma; Das, Shantanu; Tarafdar, Sujata
2010-01-01
Starch solutions, which are strongly non-Newtonian, show a surface instability, when subjected to a load. A droplet of the fluid is sandwiched between two glass plates and a weight varying from 1 to 5 kgs. is placed on the top plate. The area of contact between the fluid and plate increases in an oscillatory manner, unlike Newtonian fluids in a similar situation. The periphery moreover, develops a viscous fingering like instability, which is not expected under compression. We attempt to model...
Flux change in viscous laminar flow under oscillating boundary condition
Ueda, R.; Mikada, H.; Goto, T.; Takekawa, J.
2012-12-01
The behavior of interstitial fluid is one of major interest in earth sciences in terms of the exploitation of water resources, the initiation of earthquakes, enhanced oil recovery (EOR), etc. Seismic waves are often known to increase the flux of interstitial fluid but the relationship between the flux and propagating seismic waves have not been well investigated in the past, although seismic stimulation has been applied in the oil industry for enhanced oil recovery (EOR). Many observations indicated that seismic waves could stimulate the oil production due to lowering of apparent viscosity coefficient, to the coalescence and/or the dispersion of droplets of a phase in multiphase fluids. However, the detailed mechanism of seismic stimulation has not been fully understood, either. In this study, We attempt to understand the mechanism of the flux change in viscous laminar flow under oscillating boundary condition for the simulation of interstitial flow. Here, we analyze a monophase flow in a pore throat. We first assume a Hagen-Poiseuille flow of incompressible fluid through a pore-throat in a porous medium. We adopt the Lattice Boltzmann method (LBM) in which the motion of fluid is simulated through the variation of velocity distribution function representing the distribution of discrete particle velocities. We use an improved incompressible LBKG model (d2q9i) proposed in Zou et. al. (1995) to accurately accommodate the boundary conditions of pressure and velocity in the Hagen-Poiseuille flow. We also use an half-way bounce back boundary condition as the velocity boundary condition. Also, we assume a uniform pressure (density) difference between inlet and outlet flow, and the density difference could initiate the flow in our simulation. The oscillating boundary condition is given by the body force acting on fluid particles. In this simulation, we found that the flux change is negligible under small amplitude of oscillation in both horizontal and vertical directions
Li, Jin
2011-01-01
In this paper we consider the Stochastic isothermal, nonlinear, incompressible bipolar viscous fluids driven by a genuine cylindrical fractional Bronwnian motion with Hurst parameter $H \\in (1/4,1/2)$ under Dirichlet boundary condition on 2D square domain. First we prove the existence and regularity of the stochastic convolution corresponding to the stochastic non-Newtonian fluids. Then we obtain the existence and uniqueness results for the stochastic non-Newtonian fluids. Under certain condition, the random dynamical system generated by non-Newtonian fluids has a random attractor.
Non-Newtonian Properties of Relativistic Fluids
Koide, Tomoi
2010-01-01
We show that relativistic fluids behave as non-Newtonian fluids. First, we discuss the problem of acausal propagation in the diffusion equation and introduce the modified Maxwell-Cattaneo-Vernotte (MCV) equation. By using the modified MCV equation, we obtain the causal dissipative relativistic (CDR) fluid dynamics, where unphysical propagation with infinite velocity does not exist. We further show that the problems of the violation of causality and instability are intimately related, and the relativistic Navier-Stokes equation is inadequate as the theory of relativistic fluids. Finally, the new microscopic formula to calculate the transport coefficients of the CDR fluid dynamics is discussed. The result of the microscopic formula is consistent with that of the Boltzmann equation, i.e., Grad's moment method.
Structural Optimization of non-Newtonian Microfluidics
DEFF Research Database (Denmark)
Jensen, Kristian Ejlebjærg
2013-01-01
Many of the biological fluids analyzed in Lab-on-a-Chip systems contain elastic components, which gives the fluids elastic character. Such fluids are said to be non-Newtonian or, more precisely, viscoelastic. They can give rise to exotic effects on the macroscale, which are never seen for fluids...... with components relying on viscoelastic effects, but the non-intuitive nature of these fluids complicates the design process. This thesis combines the method of topology optimization with differential constitutive equations, which govern the flow of viscoelastic fluids. The optimization method iteratively...... experimentally, and compared the results with the established hyperbolic designs. We found superior performance in the parameter regime of the optimization as well as similar optimal performance [P3]. The cross-slot geometry is known to exhibit bistability for viscoelastic fluids. We studied this geometry...
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.
Dean vortex membrane microfiltration non-Newtonian viscosity effects
Schutyser, M.A.I.; Belfort, G.
2002-01-01
Many industrial feeds behave as non-Newtonian fluids, and little understanding exists as to their influence on cross-flow microfiltration (CMF) performance. The viscosity effects of a model non-Newtonian shear-thickening fluid were investigated in CMF with and without suspended silica particles in t
Dean vortex membrane microfiltration non-Newtonian viscosity effects
Schutyser, M.A.I.; Belfort, G.
2002-01-01
Many industrial feeds behave as non-Newtonian fluids, and little understanding exists as to their influence on cross-flow microfiltration (CMF) performance. The viscosity effects of a model non-Newtonian shear-thickening fluid were investigated in CMF with and without suspended silica particles in
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.
Non-Newtonian Aspects of Artificial Intelligence
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.
Theoretical aspects of non-newtonian fluids flow simulation in food technologies
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E. Biletskii
2015-05-01
Full Text Available Introduction. The problems of simulating viscoplastic longitudinal and cross-sectional flow of non-Newtonian fluids are overviewed. Materials and methods. For the first time the superposition method by expressing the components of the stress tensor for building flow fields with higher dimension from flow fields with lower dimension with various boundary conditions when rheological parameters change depending on pressure was used. The flows in the channel are categorized by velocity and pressure values in each point of the section. Results.The theoretical methods for simulating flows of non-Newtonian fluids in channels of different geometry with moving bounds and pressure drop on channel edges with respect to functional connections between main process parameters are described using the superposition method. It is shown that longitudinal and cross-sectional are reduced to the collection of one-dimensional longitudinal flows of the same type which allow to describe three-dimensional isothermal in rectangular channel and two-dimensional flows in flat channels with different channel aspect ratio. The received theoretical two- and three-dimensional model of viscous flows in channels with basic geometry allow to research main regularities of the process and to establish optimal macro-kinetic and macro-dynamic flow characteristics of non-Newtonian materials which are aimed at reducing energy costs and material consumption of food processing equipment. Conclusion.The developed and theoretically reasonable three-dimensional models flows of non-Newtonian fluids in channels allow to perform qualitatively new design of food processing equipment which allows to reduce energy costs and material consumption.
Weak solutions for a non-Newtonian diffuse interface model with different densities
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.
Sinking of spherical slablets through a non-Newtonian mantle
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
Low-frequency oscillations of a cylinder in a viscous fluid
Amin, Norsarahaida
1988-05-01
The flow induced by a circular cylinder oscillating in a viscous fluid when the amplitude of the oscillation is small and the frequecy is low is considered. This solution, obtained by the method of matched asymptotic expansions, is compared with the solution obtained from an Oseen approximation to the governing equations by Andres and Ingard (1953).
Directory of Open Access Journals (Sweden)
Jun Xie
2016-01-01
Full Text Available A weakly compressible moving particle semi-implicit (WC-MPS method is utilized to simulate non-Newtonian free surface flows due to the advantages of particle methods with respect to handling large deformation and fragmentation. The Cross rheology equation was selected in order to capture the viscous features of the mixture flows. To numerically implement the Cross equation, an experiment-based method was proposed to determine the four rheology parameters in the equation. The method of using a WC-MPS model to study non-Newtonian dam break flow problems was then adopted. The capabilities of the proposed method were tested by simulating different materials with the proposed method in modeling non-Newtonian free surface flows. Significant viscous features were reproduced by the proposed model.
Simulation of non-Newtonian ink transfer between two separating plates for gravure-offset printing
Energy Technology Data Exchange (ETDEWEB)
Ahmed, Dewan Hasan [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Sung, Hyung Jin, E-mail: hjsung@kaist.ac.k [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Kim, Dong-Soo [Nano-Mechanical Systems Research Division, Korea Institute of Machinery and Materials, 171, Jang-dong, Yuseong-gu, Daejeon 305-343 (Korea, Republic of)
2011-02-15
The inks used in gravure-offset printing are non-Newtonian fluids with higher viscosities and lower surface tensions compared to Newtonian fluids. This paper examines the transfer of a non-Newtonian ink between two parallel plates when the top plate is moved upward with a constant velocity while the bottom plate is held fixed. Numerical simulations were carried out using the Carreau model to explore the behavior of a non-Newtonian ink in gravure-offset printing. The volume of fluid (VOF) model was adopted to demonstrate the stretching and break-up behaviors of the ink. The results indicate that the ink transfer ratio is greatly influenced by the contact angle, especially the contact angle at the upper plate ({alpha}). For lower values of {alpha}, oscillatory or unstable behavior of the position of minimum thickness of the ink between the two parallel plates during the stretching period is observed. This oscillation gradually diminishes as the contact angle at the upper plate is increased. Moreover, the number of satellite droplets increases as the velocity of the upper plate is increased. The surface tension of the conductive ink shows a positive impact on the ink transfer ratio to the upper plate. Indeed, the velocity of the upper plate has a significant influence on the ink transfer in gravure-offset printing when the Capillary number (Ca) is greater than 1 and the surface tension dominates over the ink transfer process when Ca is less than 1.
Physiological non-Newtonian blood flow through single stenosed artery
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.
Non-Newtonian viscosity in magnetized plasma
Johnson, Robert W
2007-01-01
The particle and momentum balance equations can be solved on concentric circular flux surfaces to determine the effective viscous drag present in a magnetized tokamak plasma in the low aspect ratio limit. An analysis is developed utilizing the first-order Fourier expansion of the poloidal variation of quantities on the flux surface akin to that by Stacey and Sigmar [Phys. Fluids, 28, 9 (1985)]. Expressions to determine the poloidal variations of density, poloidal velocity, toroidal velocity, radial electric field, poloidal electric field, and other radial profiles are presented in a multi-species setting. Using as input experimental data for the flux surface averaged profiles of density, temperature, toroidal current, toroidal momentum injection, and the poloidal and toroidal rotations of at least one species of ion, one may solve the equations numerically for the remaining profiles. The resultant effective viscosities are compared to those predicted by Stacey and Sigmar and Shaing, et al., [Nuclear Fusion, 2...
The Inveterate Tinkerer: 5. Experiments with Non-Newtonian Fluids
Indian Academy of Sciences (India)
Chirag kalelkar
2017-07-01
In this series of articles, the authors discuss various phenomenain fluid dynamics, which may be investigated via tabletopexperiments using low-cost or home-made instruments.The fifth article in this series is about some fascinating experimentswith non-Newtonian fluids.
Pressure Drop of Non-Newtonian Liquid Flow Through Elbows
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Experimental data on the pressure drop across different types of elbow for non-Newtonian pseudoplastic liquid flow in laminar condition have been presented. A generalized correlation has been developed for predicting the frictional pressure drop across the elbows in the horizontal plane.
Numerical Simulation of Bubble Evolution in Non-Newtonian Fluid
Institute of Scientific and Technical Information of China (English)
唐亦农; 陈耀松; 陈文芳
1994-01-01
In this paper the bubble issuing from an orifice at the bottom of the boundary evolution in a finite Non-Newtonian fluid(such as Maxwell fluid,Carreu fluid)is numerically simulated The effects of the rheological behavior,physical parameters and circumstantial conditions are discussed in detail
Flow Curve Determination for Non-Newtonian Fluids.
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)
On preconditioning incompressible non-Newtonian flow problems
He, X.; Neytcheva, M.; Vuik, C.
2013-01-01
This paper deals with fast and reliable numerical solution methods for the incompressible non-Newtonian Navier-Stokes equations. To handle the nonlinearity of the governing equations, the Picard and Newton methods are used to linearize these coupled partial differential equations. For space discreti
Inelastic non-Newtonian flow over heterogeneously slippery surfaces
Haase, A. Sander; Wood, Jeffery A.; Sprakel, Lisette M.J.; Lammertink, Rob G.H.
2017-01-01
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 bub
Oscillations of weakly viscous conducting liquid drops in a strong magnetic field
Priede, Jānis
2010-01-01
We analyse small-amplitude oscillations of weakly viscous and electrically conducting liquid drop in a strong uniform DC magnetic field. An asymptotic solution is obtained showing that magnetic field does not affect the shape eigenmodes, which remain the spherical harmonics as in the non-magnetic case. Strong magnetic field, however, constrains the liquid flow associated with the oscillations and, thus, it reduces the oscillations frequency by increasing the apparent inertia of the liquid. In such a field, liquid oscillates in a two-dimensional (2D) way as solid columns aligned with the field. Two types of oscillations are possible: longitudinal and transversal to the field. Such oscillations are weakly damped by strong magnetic field. The stronger the field, the weaker the damping, except for the axisymmetric transversal modes, which are magnetically overdamped because they are not kinematically compatible with 2D flow. Because magnetic damping decreases inversely with the square of the field strength, visco...
Walker, Andrew M; Johnston, Clifton R; Rival, David E
2012-11-01
Although deployed in the vasculature to expand vessel diameter and improve blood flow, protruding stent struts can create complex flow environments associated with flow separation and oscillating shear gradients. Given the association between magnitude and direction of wall shear stress (WSS) and endothelial phenotype expression, accurate representation of stent-induced flow patterns is critical if we are to predict sites susceptible to intimal hyperplasia. Despite the number of stents approved for clinical use, quantification on the alteration of hemodynamic flow parameters associated with the Gianturco Z-stent is limited in the literature. In using experimental and computational models to quantify strut-induced flow, the majority of past work has assumed blood or representative analogs to behave as Newtonian fluids. However, recent studies have challenged the validity of this assumption. We present here the experimental quantification of flow through a Gianturco Z-stent wire in representative Newtonian and non-Newtonian blood analog environments using particle image velocimetry (PIV). Fluid analogs were circulated through a closed flow loop at physiologically appropriate flow rates whereupon PIV snapshots were acquired downstream of the wire housed in an acrylic tube with a diameter characteristic of the carotid artery. Hemodynamic parameters including WSS, oscillatory shear index (OSI), and Reynolds shear stresses (RSS) were measured. Our findings show that the introduction of the stent wire altered downstream hemodynamic parameters through a reduction in WSS and increases in OSI and RSS from nonstented flow. The Newtonian analog solution of glycerol and water underestimated WSS while increasing the spatial coverage of flow reversal and oscillatory shear compared to a non-Newtonian fluid of glycerol, water, and xanthan gum. Peak RSS were increased with the Newtonian fluid, although peak values were similar upon a doubling of flow rate. The introduction of the
Jayaprasad, N; Bhalerao, M; Sengupta, Anand S; Majumder, Barun
2013-01-01
We design a low-cost, electromagnetically coupled, simple harmonic oscillator and demonstrate free, damped and forced oscillations in an under-graduate (UG) Physics laboratory. It consists of a spring-magnet system that can oscillate inside a cylinder around which copper coils are wound. Such demonstrations can compliment the traditional way in which a Waves & Oscillations course is taught and offers a richer pedagogical experience for students. We also show that with minimal modifications, it can be used to probe the magnitude of viscous damping forces in liquids by analyzing the oscillations of an immersed magnet. Finally, we propose some student activities to explore non-linear damping effects and their characterization using this apparatus.
Chen, Xiaodong
2012-01-01
In this video, Ray-tracing data visualization technique was used to obtain realistic and detailed flow motions during droplet collision. The differences of collision outcome between Newtonian and non-Newtonian were compared. Various types of droplet collision were presented, including bouncing, coalescence, and stretching separation. Because of the reducing of equivalent viscosity caused by shear stress, the gas film between shear-thinning droplet is thinner than Newtonian liquid. Since thinner gas film promotes coalescence, shear thinning liquid has smaller area of bouncing regime in the diagram of Weber number and impact parameter. During the ligament/thread breakup process of stretching separation, two kinds of instabilities are identified, helical and buckling instabilities. Helical instability is analogous to a viscous rotating liquid jet, while the buckling instability is analogous to electrically charged liquid jets of polymer solutions.
Existence for a Class of Non-Newtonian Fluids with a Nonlocal Friction Boundary Condition
Institute of Scientific and Technical Information of China (English)
L.CONSIGLIERI
2006-01-01
We deal with a variational inequality describing the motion of incompressible fluids, whose viscous stress tensors belong to the subdifferential of a functional at the point given by the symmetric part of the velocity gradient, with a nonlocal friction condition on a part of the boundary obtained by a generalized mollification of the stresses. We establish an existence result of a solution to the nonlocal friction problem for this class of non-Newtonian flows. The result is based on the Faedo-Galerkin and Moreau-Yosida methods, the duality theory of convex analysis and the Tychonov-Kakutani-Glicksberg fixed point theorem for multi-valued mappings in an appropriate functional space framework.
Force effects on rotor of squeeze film damper using Newtonian and non-Newtonian fluid
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.
Journal Bearings Lubrication Aspect Analysis Using Non-Newtonian Fluids
Directory of Open Access Journals (Sweden)
Abdessamed Nessil
2013-01-01
Full Text Available The aim of this work is related to an analysis of journal bearings lubrication using non-Newtonian fluids which are described by a power-law model. The performance characteristics of the journal bearings are determined for various values of the non-Newtonian power-law index “” which is equal to: 0.9, 1, and 1.1. Obtained numerical results show that for the dilatant fluids (, the load-carrying capacity, the pressure, the temperature, and the frictional force increased while for the pseudo-plastic fluids ( they decreased. The influence of the thermal effects on these characteristics is important at higher values of the flow behavior index “.” Obtained results are compared to those obtained by others. Good agreement is observed between the different results.
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.
Geophysical Aspects of Non-Newtonian Fluid Mechanics
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.
Non--Newtonian gravity and coherence properties of light
Camacho, A
2001-01-01
In this work the possibility of detecting a non--Newtonian contribution to the gravitational potential by means of its effects upon the first and second--order coherence properties of light is analyzed. It will be proved that, in principle, the effects of a fifth force upon the correlation functions of electromagnetic radiation could be used to detect the existence of new forces. Some constraints upon the experimental parameters will also be deduced.
Non-Newtonian ink transfer in gravure-offset printing
Energy Technology Data Exchange (ETDEWEB)
Ghadiri, Fatemeh; Ahmed, Dewan Hasan [Department of Mechanical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Sung, Hyung Jin, E-mail: hjsung@kaist.ac.k [Department of Mechanical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Shirani, Ebrahim [Department of Mechanical Engineering, Isfahan University of Technology, 841568311, Isfahan (Iran, Islamic Republic of)
2011-02-15
The inks used in gravure-offset printing are non-Newtonian fluids with higher viscosities and lower surface tensions than Newtonian fluids. This paper examines the transfer of a non-Newtonian ink between a flat plate and a groove when the plate is moved upward with a constant velocity while the groove is held fixed. Numerical simulations were carried out with the Carreau model to explore the behavior of this non-Newtonian ink in gravure-offset printing. The volume of fluid (VOF) method was implemented to capture the interface during the ink transfer process. The effects of varying the contact angle of the ink on the flat plate and groove walls and geometrical parameters such as the groove angle and the groove depth on the breakup time of the liquid filament that forms between the plate and the groove and the ink transfer ratio were determined. Our results indicate that increasing the groove contact angle and decreasing the flat plate contact angle enhance the ink transfer ratio and the breakup time. However, increasing the groove depth and the groove angle decreases the transfer ratio and the breakup time. By optimizing these parameters, it is possible to achieve an ink transfer from the groove to the flat plate of approximately 92%. Moreover, the initial width and the vertical velocity of the neck of the ink filament have significant influences on the ink transfer ratio and the breakup time.
Influence of Non-Newtonian rheology on magma degassing
Divoux, Thibaut; Ripepe, Maurizio; Géminard, Jean-Christophe
2011-01-01
Many volcanoes exhibit temporal changes in their degassing process, from rapid gas puffing to lava fountaining and long-lasting quiescent passive degassing periods. This range of behaviors has been explained in terms of changes in gas flux and/or magma input rate. We report here a simple laboratory experiment which shows that the non- Newtonian rheology of magma can be responsible, alone, for such intriguing behavior, even in a stationary gas flux regime. We inject a constant gas flow-rate Q at the bottom of a non-Newtonian fluid column, and demonstrate the existence of a critical flow rate Q* above which the system spontaneously alternates between a bubbling and a channeling regime, where a gas channel crosses the entire fluid column. The threshold Q* depends on the fluid rheological properties which are controlled, in particular, by the gas volume fraction (or void fraction) {\\phi}. When {\\phi} increases, Q* decreases and the degassing regime changes. Non-Newtonian properties of magma might therefore play a...
Mechanical energy and mean equivalent viscous damping for SDOF fractional oscillators
Yuan, Jian; Gai, Mingjiu; Yang, Shujie
2016-01-01
This paper addresses the total mechanical energy of a single degree of freedom fractional oscillator. Based on the energy storage and dissipation properties of the Caputo fractional derivatives, the expression for total mechanical energy in the single degree of freedom fractional oscillator is firstly presented. The energy regeneration due to the external exciting force and the energy loss due to the fractional damping force during the vibratory motion are analyzed. Furthermore, based on the mean energy dissipation of the fractional damping element in steady-state vibration, a new concept of mean equivalent viscous damping is suggested and the value of the damping coefficient is evaluated.
Numerical Well Test Analysis for Polymer Flooding considering the Non-Newtonian Behavior
Directory of Open Access Journals (Sweden)
Jia Zhichun
2015-01-01
Full Text Available Well test analysis for polymer flooding is different from traditional well test analysis because of the non-Newtonian properties of underground flow and other mechanisms involved in polymer flooding. Few of the present works have proposed a numerical approach of pressure transient analysis which fully considers the non-Newtonian effect of real polymer solution and interprets the polymer rheology from details of pressure transient response. In this study, a two-phase four-component fully implicit numerical model incorporating shear thinning effect for polymer flooding based on PEBI (Perpendicular Bisection grid is developed to study transient pressure responses in polymer flooding reservoirs. Parametric studies are conducted to quantify the effect of shear thinning and polymer concentration on the pressure transient response. Results show that shear thinning effect leads to obvious and characteristic nonsmoothness on pressure derivative curves, and the oscillation amplitude of the shear-thinning-induced nonsmoothness is related to the viscosity change decided by shear thinning effect and polymer concentration. Practical applications are carried out with shut-in data obtained in Daqing oil field, which validates our findings. The proposed method and the findings in this paper show significant importance for well test analysis for polymer flooding and the determination of the polymer in situ rheology.
In defense of a non-newtonian economic analysis
Filip, Diana; Piatecki, Cyrille
2014-01-01
The double-entry bookkeeping promoted by Luca Pacioli in the fifteenth century could be considered a strong argument in behalf of the multiplicative calculus which can be developed from the Grossman and Katz non-newtonian calculus concept. In order to emphasize this statement we present a brief history of the accountancy in its early time and we make the point of Ellerman's research concerning the double-entry bookkeeping.; La comptabilité en partie double présentée par Luca Pacioli au quinzi...
Memory Effects and Transport Coefficients for Non-Newtonian Fluids
Kodama, T
2008-01-01
We discuss the roles of viscosity in relativistic fluid dynamics from the point of view of memory effects. Depending on the type of quantity to which the memory effect is applied, different terms appear in higher order corrections. We show that when the memory effect applies on the extensive quantities, the hydrodynamic equations of motion become non-singular. We further discuss the question of memory effect in the derivation of transport coefficients from a microscopic theory. We generalize the application of the Green-Kubo-Nakano (GKN) to calculate transport coefficients in the framework of projection operator formalism, and derive the general formula when the fluid is non-Newtonian.
Static stability of collapsible tube conveying non-Newtonian fluid
Yushutin, V S
2014-01-01
The global static stability of a Starling Resistor conveying non-Newtonian fluid is considered. The Starling Resistor consists of two rigid circular tubes and axisymmetric collapsible tube mounted between them. Upstream and downstream pressures are the boundary condition as well as external to the collapsible tube pressure. Quasi one-dimensional model has been proposed and a boundary value problem in terms of nondimensional parameters obtained. Nonuniqueness of the boundary value problem is regarded as static instability. The analytical condition of instability which defines a surface in parameter space has been studied numerically. The influence of fluid rheology on stability of collapsible tube is established.
Heat Transfer for Power Law Non-Newtonian Fluids
Institute of Scientific and Technical Information of China (English)
ZHENG Lian-Cun; ZHANG Xin-Xin; LU Chun-Qing
2006-01-01
We present a theoretical analysis for heat transfer in power law non-Newtonian fluid by assuming that the thermal diffusivity is a function of temperature gradient. The laminar boundary layer energy equation is considered as an example to illustrate the application. It is shown that the boundary layer energy equation subject to the corresponding boundary conditions can be transformed to a boundary value problem of a nonlinear ordinary differential equation when similarity variables are introduced. Numerical solutions of the similarity energy equation are presented.
Random Attractors of Stochastic Non-Newtonian Fluids
Institute of Scientific and Technical Information of China (English)
Chun-xiao GUO; Bo-ling GUO; Yong-qian HAN
2012-01-01
The present paper investigates the asymptotic behavior of solutions for stochastic non-Newtonian fluids in a two-dimensional domain.Firstly,we prove the existence of random attractors AH(ω) in H; Secondly,we prove the existence of random attractors Av(ω) in V.Then we verify regularity of the random attractors by showing that AH(ω) =Av(ω),which implies the smoothing effect of the fluids in the sense that solution becomes eventually more regular than the initial data.
Test of non-Newtonian gravitational force at micrometer range
Luo, Pengshun; Guan, Shengguo; Wu, Wenjie; Tian, Zhaoyang; Yang, Shanqing; Shao, Chenggang; Luo, Jun
2016-01-01
We report an experimental test of non-Newtonian gravitational forces at mi- crometer range. To experimentally subtract off the Casimir force and the electrostatic force background, differential force measurements were performed by sensing the lateral force between a gold sphere and a density modulated source mass using a soft cantilever. The current sensitivity is limited by the patch electrostatic force, which is further improved by two dimensional (2D) force mapping. The preliminary result sets a model independent constraint on the Yukawa type force at this range.
Air Sparging for Mixing Non-Newtonian Slurries
Energy Technology Data Exchange (ETDEWEB)
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
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.
Dynamics of Non-Newtonian Liquid Droplet Collision
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.
THREE-DIMENSIONAL INSTABILITY OF AN OSCILLATING VISCOUS FLOW PAST A CIRCULAR CYLINDER
Institute of Scientific and Technical Information of China (English)
陆夕云; 凌国灿
2003-01-01
A systematically numerical study of the sinusoidally oscillating viscous flowaround a circular cylinder was performed to investigate vortical instability by solving thethree-dimensional incompressible Navier-Stokes equations. The transition from two- to three-dimensional flow structures along the axial direction due to the vortical instability appears,and the three-dimensional structures lie alternatively on the two sides of the cylinder.Numerical study has been taken for the Keulegan-Carpenter(KC) numbers from 1 to 3.2and frequency parameters from 1O0 to 600. The force behaviors are also studied by solvingthe Morison equation. Calculated results agree well with experimental data and theoreticalprediction.
Steady flow of a non-Newtonian fluid through a contraction
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.
Directory of Open Access Journals (Sweden)
MM Movahedi
2008-03-01
Full Text Available Background: There is considerable evidence that vascular fluid dynamics plays an important role in the developmentand prevalence of atherosclerosis which is one of the most widespread disease in humans .The onset and prevalence of atherosclerosis hemodynamic parameter are largely affected by geometric parameters. If any obstacle interferes with the blood flow, the above parameters change dramatically. Most of the arterial diseases, such as atherosclerosis, occur in the arteries with complex patterns of fluid flow where the blood dynamics plays an important role. Arterial stenosis mostly occurs in an area with a complex pattern of fluid flow, such as coronary artery, aorta bifurcation, carotid and vessels of lower limbs. During the past three decades, many experimental studies have been performed on the hemodynamic role of the blood in forming sediment in the inner wall of the vessels. It has been shown that forming sediment in the inner wall of vessels depends on the velocity of fluid and also on the amount of wall shear stress.Methods: We have examined the effect on the blood flow of local stenosis in carotid artery in numerical form using the incompressible Navier-Stockes equations. The profile of the velocity in different parts and times in the pulsatile cycle, separation and reattachment points on the wall, the distance stability of flow and also alteration caused by the wall shear stress in entire vessel were shown and compared with two behaviors flow (Newtonian and Non-Newtonian.Finally we describe the influence of the severity of the stenosis on the separation and reattachmentpoints for a Non-Newtonian fuid. Results: In the present study, we have pointed very low and high oscillating WSS (Wall Shear Stress values play a significant role in the development of forming sediment in the inner wall of vessels. Also, we obtain this probability is higher for Newtonian than Non-Newtonian fluid behavior.Conclusion: Based on our results, the
Transverse and lateral confinement effects on the oscillations of a free cylinder in a viscous flow
Gianorio, Luciano; Cachile, Mario; Hulin, Jean-Pierre; Auradou, Harold
2013-01-01
The different types of instabilities of free cylinders (diameter $D$, length $L$) have been studied in a viscous flow (velocity $U$) between parallel vertical walls of horizontal width $W$ at a distance $H$: the influence of the confinement parameters $D/H$ and $L/W$ has been investigated. As $D/H$ increases, there is a transition from stable flow to oscillations transverse to the walls and then to a fluttering motion with oscillations of the angle of the axis with respect to the horizontal. The two types of oscillations may be superimposed in the transition domain. The frequency $f$ of the transverse oscillations is independent of the lateral confinement $L/W$ in the range: 0.055 \\le L/W \\le 0.94$ for a given cylinder velocity $V_{cx}$ and increases only weakly with $V_{cx}$. These results are accounted for by assuming a 2D local flow over the cylinder with a characteristic velocity independent of $L/W$ for a given $V_{cx}$ value. The experimental values of $f$ are also independent of the transverse confinem...
Effects of non Newtonian spiral blood flow through arterial stenosis
Hasan, Md. Mahmudul; Maruf, Mahbub Alam; Ali, Mohammad
2016-07-01
The spiral component of blood flow has both beneficial and detrimental effects in human circulatory system. A numerical investigation is carried out to analyze the effect of spiral blood flow through an axisymmetric three dimensional artery having 75% stenosis at the center. Blood is assumed as a Non-Newtonian fluid. Standard k-ω model is used for the simulation with the Reynolds number of 1000. A parabolic velocity profile with spiral flow is used as inlet boundary condition. The peak values of all velocity components are found just after stenosis. But total pressure gradually decreases at downstream. Spiral flow of blood has significant effects on tangential component of velocity. However, the effect is mild for radial and axial velocity components. The peak value of wall shear stress is at the stenosis zone and decreases rapidly in downstream. The effect of spiral flow is significant for turbulent kinetic energy. Detailed investigation and relevant pathological issues are delineated throughout the paper.
Inline Ultrasonic Rheometry of a Non-Newtonian Waste Simulant
Energy Technology Data Exchange (ETDEWEB)
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
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.
Energy Technology Data Exchange (ETDEWEB)
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.
Viscoelastic fluid-structure interaction between a non-Newtonian fluid flow and flexible cylinder
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.
Numerical analysis of non-Newtonian rheology effect on hydrocyclone flow field
Directory of Open Access Journals (Sweden)
Lin Yang
2015-03-01
Full Text Available In view of the limitations of the existing Newton fluid effects on the vortex flow mechanism study, numerical analysis of non Newton fluid effects was presented. Using Reynolds stress turbulence model (RSM and mixed multiphase flow model (Mixture of FLUENT (fluid calculation software and combined with the constitutive equation of apparent viscosity of non-Newtonian fluid, the typical non-Newtonian fluid (drilling fluid, polymer flooding sewage and crude oil as medium and Newton flow field (water as medium were compared by quantitative analysis. Based on the research results of water, the effects of non-Newtonian rheology on the key parameters including the combined vortex motion index n and tangential velocity were analyzed. The study shows that: non-Newtonian rheology has a great effect on tangential velocity and n value, and tangential velocity decreases with non-Newtonian increasing. The three kinds of n values (constant segment are: 0.564(water, 0.769(polymer flooding sewage, 0.708(drilling fluid and their variation amplitudes are larger than Newtonian fluid. The same time, non-Newtonian rheology will lead to the phenomenon of turbulent drag reduction in the vortex flow field. Compared with the existing formula calculation results shown, the calculation result of non-Newtonian rheology is most consistent with the simulation result, and the original theory has large deviations. The study provides reference for theory research of non-Newtonian cyclone separation flow field.
Oscillations in solar jets observed with the SOT of Hinode: viscous effects during reconnection
Tavabi, E.; Koutchmy, S.
2014-07-01
Transverse oscillatory motions and recurrence behavior in the chromospheric jets observed by Hinode/SOT are studied. A comparison is considered with the behavior that was noticed in coronal X-ray jets observed by Hinode/XRT. A jet like bundle observed at the limb in Ca II H line appears to show a magnetic topology that is similar to X-ray jets (i.e., the Eiffel tower shape). The appearance of such magnetic topology is usually assumed to be caused by magnetic reconnection near a null point. Transverse motions of the jet axis are recorded but no clear evidence of twist is appearing from the highly processed movie. The aim is to investigate the dynamical behavior of an incompressible magnetic X-point occurring during the magnetic reconnection in the jet formation region. The viscous effect is specially considered in the closed line-tied magnetic X-shape nulls. We perform the MHD numerical simulation in 2-D by solving the visco-resistive MHD equations with the tracing of velocity and magnetic field. A qualitative agreement with Hinode observations is found for the oscillatory and non-oscillatory behaviors of the observed solar jets in both the chromosphere and the corona. Our results suggest that the viscous effect contributes to the excitation of the magnetic reconnection by generating oscillations that we observed at least inside this Ca II H line cool solar jet bundle.
Gravity driven instabilities in miscible non-Newtonian fluid displacements in porous media
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.
Non-Newtonian Behavior of Diblock and Triblock Copolymer Solutions
Watanabe, Hiroshi
2006-03-01
Non-Newtonian flow behavior was examined for butadiene-styrene (BS) diblock and BSB triblock copolymers dissolved in a S-selective solvent, dibutyl phthalate (DBP). Spherical domains of the non-solvated B blocks were arranged on a bcc lattice in both solutions at equilibrium, as revealed from SANS. The solutions exhibited significant thinning under steady flow, which was well correlated with the disruption of the bcc lattice detected with SANS. The lattice disruption was most prominent at a shear rate comparable to the frequency of B/S concentration fluctuation. For the BS/DBP solution, the recovery of the lattice structure after cessation of flow was the slowest for the most heavily disrupted lattice, as naturally expected. In contrast, for the BSB/DBP solution, the recovery rate was insensitive to the magnitude of lattice disruption. This peculiar behavior of the BSB solution suggests that the rate-determining step of the recovery in this solution is the transient B/S mixing required for reformation of the S bridges connecting the B domains.
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.
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.
Hydromagnetic Non-Darcian Free-Convective Flow of a Non-Newtonian Fluid with Temperature Jump
Directory of Open Access Journals (Sweden)
Ahmed M. Salem
2013-01-01
Full Text Available In the present study, the effect of viscous dissipation on magnetohydrodynamic (MHD non-Darcian free-convection flow of a non-Newtonian power-law fluid past a vertical flat plate in a saturated porous medium with variable viscosity and temperature jump is considered. The fluid is permeated by a transverse magnetic field imposed perpendicularly to the plate on the assumption of a small magnetic Reynolds number. The fluid viscosity is assumed to vary as a reciprocal of linear function of temperature. The governing boundary layer equations and boundary conditions are cast into a dimensionless form and simplified by using a similarity transformation into a system of nonlinear ordinary differential equations and solved numerically. The effects of the governing parameters on the flow fields and heat transfer are shown in graphs and tabular form.
The Construction of Hilbert Spaces over the Non-Newtonian Field
Uğur Kadak; Hakan Efe
2014-01-01
Although there are many excellent ways to present the principle of the classical calculus, the novel presentations probably lead most naturally to the development of the non-Newtonian calculi. In this paper we introduce vector spaces over real and complex non-Newtonian field with respect to the *-calculus which is a branch of non-Newtonian calculus. Also we give the definitions of real and complex inner product spaces and study Hilbert spaces which are special type of normed space and complet...
Generalized Runge-Kutta Method with respect to the Non-Newtonian Calculus
Uğur Kadak; Muharrem Özlük
2015-01-01
Theory and applications of non-Newtonian calculus have been evolving rapidly over the recent years. As numerical methods have a wide range of applications in science and engineering, the idea of the design of such numerical methods based on non-Newtonian calculus is self-evident. In this paper, the well-known Runge-Kutta method for ordinary differential equations is developed in the frameworks of non-Newtonian calculus given in generalized form and then tested for different generating functio...
A Generalization on Weighted Means and Convex Functions with respect to the Non-Newtonian Calculus
Directory of Open Access Journals (Sweden)
Uğur Kadak
2016-01-01
Full Text Available This paper is devoted to investigating some characteristic features of weighted means and convex functions in terms of the non-Newtonian calculus which is a self-contained system independent of any other system of calculus. It is shown that there are infinitely many such useful types of weighted means and convex functions depending on the choice of generating functions. Moreover, some relations between classical weighted mean and its non-Newtonian version are compared and discussed in a table. Also, some geometric interpretations of convex functions are presented with respect to the non-Newtonian slope. Finally, using multiplicative continuous convex functions we give an application.
Convex functions and some inequalities in terms of the Non-Newtonian Calculus
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.
Lubrication performances of short journal bearings operating with non-Newtonian ferrofluids
Energy Technology Data Exchange (ETDEWEB)
Lin, Jaw-Ren [Taoyuan Innovation Inst. of Tech., Jhongli, TW (China). Dept. of Mechanical Engineering; Li, Po-Jui [National Taipei Univ. of Technology, Taipei, TW (China). Dept. of Inst. of Mechatronic Engineering; Hung, Tzu-Chen [National Taipei Univ. of Technology, Taipei, TW (China). Dept. of Mechanical Engineering
2013-03-15
The lubrication performances of short journal bearings operating with non-Newtonian ferrofluids have been investigated in the present study. Based upon the ferrofluid model of Shliomis and the micro-continuum theory of Stokes, a two-dimensional modified Reynolds equation is derived by taking into account the effects of rotation of ferromagnetic particles and the effects of non-Newtonian properties. As an application, the short-bearing approximation is illustrated. Comparing with the conventional non-ferrofluid case, the short journal bearings with ferrofluids in the presence of magnetic fields result in a higher load capacity. Comparing with the Newtonian ferrofluid case, the non-Newtonian effects of couple stresses provide an enhancement in the load capacity, as well as a reduction in the friction parameter. The inclusion of non-Newtonian couple stresses signifies an improvement in performance characteristics of ferrofluid journal bearings. (orig.)
Certain Spaces of Functions over the Field of Non-Newtonian Complex Numbers
Directory of Open Access Journals (Sweden)
Ahmet Faruk Çakmak
2014-01-01
Full Text Available This paper is devoted to investigate some characteristic features of complex numbers and functions in terms of non-Newtonian calculus. Following Grossman and Katz, (Non-Newtonian Calculus, Lee Press, Piegon Cove, Massachusetts, 1972, we construct the field ℂ* of *-complex numbers and the concept of *-metric. Also, we give the definitions and the basic important properties of *-boundedness and *-continuity. Later, we define the space C*(Ω of *-continuous functions and state that it forms a vector space with respect to the non-Newtonian addition and scalar multiplication and we prove that C*(Ω is a Banach space. Finally, Multiplicative calculus (MC, which is one of the most popular non-Newtonian calculus and created by the famous exp function, is applied to complex numbers and functions to investigate some advance inner product properties and give inclusion relationship between C*(Ω and the set of C*′(Ω*-differentiable functions.
Generalized Runge-Kutta Method with respect to the Non-Newtonian Calculus
Directory of Open Access Journals (Sweden)
Uğur Kadak
2015-01-01
Full Text Available Theory and applications of non-Newtonian calculus have been evolving rapidly over the recent years. As numerical methods have a wide range of applications in science and engineering, the idea of the design of such numerical methods based on non-Newtonian calculus is self-evident. In this paper, the well-known Runge-Kutta method for ordinary differential equations is developed in the frameworks of non-Newtonian calculus given in generalized form and then tested for different generating functions. The efficiency of the proposed non-Newtonian Euler and Runge-Kutta methods is exposed by examples, and the results are compared with the exact solutions.
Institute of Scientific and Technical Information of China (English)
Zhao Caidi; Jia Xiaolin; Yang Xinbo
2011-01-01
This paper is joint with [27].The authors prove in this article the existence and reveal its structure of uniform attractor for a two-dimensional nonautonomous incompressible non-Newtonian fluid with a new class of external forces.
H 2-regularity random attractors of stochastic non-Newtonian fluids with multiplicative noise
Institute of Scientific and Technical Information of China (English)
Chun-xiao GUO; Bo-ling GUO; Hui YANG
2014-01-01
In this paper, the authors study the long time behavior of solutions to stochastic non-Newtonian fluids in a two-dimensional bounded domain, and prove the existence of H 2-regularity random attractor.
Upper Semicontinuity of Attractors for a Non-Newtonian Fluid under Small Random Perturbations
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Jianxin Luo
2014-01-01
Full Text Available This paper investigates the limiting behavior of attractors for a two-dimensional incompressible non-Newtonian fluid under small random perturbations. Under certain conditions, the upper semicontinuity of the attractors for diminishing perturbations is shown.
Effect of non-Newtonian viscosity on the fluid-dynamic characteristics in stenotic vessels
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
A Generalization on Weighted Means and Convex Functions with respect to the Non-Newtonian Calculus
Uğur Kadak; Yusuf Gürefe
2016-01-01
This paper is devoted to investigating some characteristic features of weighted means and convex functions in terms of the non-Newtonian calculus which is a self-contained system independent of any other system of calculus. It is shown that there are infinitely many such useful types of weighted means and convex functions depending on the choice of generating functions. Moreover, some relations between classical weighted mean and its non-Newtonian version are compared and discussed in a table...
Certain Spaces of Functions over the Field of Non-Newtonian Complex Numbers
Ahmet Faruk Çakmak; Feyzi Başar
2014-01-01
This paper is devoted to investigate some characteristic features of complex numbers and functions in terms of non-Newtonian calculus. Following Grossman and Katz, (Non-Newtonian Calculus, Lee Press, Piegon Cove, Massachusetts, 1972), we construct the field ${\\Bbb C}^{\\ast}$ of ${\\ast}$ -complex numbers and the concept of ${\\ast}$ -metric. Also, we give the definitions and the basic important properties of ${\\ast}$ -boundedness and ${\\ast}$ -continuity. Later, we define the space ${C}_{\\ast}(...
Determination of the Köthe-Toeplitz Duals over the Non-Newtonian Complex Field
Uğur Kadak
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 introdu...
Decay of solutions to equations modelling incompressible bipolar non-newtonian fluids
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Bo-Qing Dong
2005-11-01
Full Text Available This article concerns systems of equations that model incompressible bipolar non-Newtonian fluid motion in the whole space $mathbb{R}^n$. Using the improved Fourier splitting method, we prove that a weak solution decays in the $L^2$ norm at the same rate as $(1+t^{-n/4}$ as the time $t$ approaches infinity. Also we obtain optimal $L^2$ error-estimates for Newtonian and Non-Newtonian flows.
Time Decay Rates of the Isotropic Non-Newtonian Flows in Rn
Institute of Scientific and Technical Information of China (English)
Bo-Qing Dong
2007-01-01
This paper is concerned with time decay rates for weak solutions to a class system of isotropic incompressible non-Newtonian fluid motion in Rn. With the use of the spectral decomposition methods of Stokes operator, the optimal decay estimates of weak solutions in L2 norm are derived under the different conditions on the initial velocity. Moreover, the error estimates of the difference between non-Newtonian flow and Navier-Stokes flow are also investigated.
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.
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.
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.
Aspects of non-Newtonian flow and displacement in porous media
Energy Technology Data Exchange (ETDEWEB)
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.
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.
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
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.
Applying Tiab’s direct synthesis technique to dilatant non-Newtonian/Newtonian fluids
Directory of Open Access Journals (Sweden)
Javier Andrés Martínez
2011-08-01
Full Text Available Non-Newtonian fluids, such as polymer solutions, have been used by the oil industry for many years as fracturing agents and drilling mud. These solutions, which normally include thickened water and jelled fluids, are injected into the formation to enhanced oil recovery by improving sweep efficiency. It is worth noting that some heavy oils behave non-Newtonianly. Non-Newtonian fluids do not have direct proportionality between applied shear stress and shear rate and viscosity varies with shear rate depending on whether the fluid is either pseudoplastic or dilatant. Viscosity decreases as shear rate increases for the former whilst the reverse takes place for dilatants. Mathematical models of conventional fluids thus fail when applied to non-Newtonian fluids. The pressure derivative curve is introduced in this descriptive work for a dilatant fluid and its pattern was observed. Tiab’s direct synthesis (TDS methodology was used as a tool for interpreting pressure transient data to estimate effective permeability, skin factors and non-Newtonian bank radius. The methodology was successfully verified by its application to synthetic examples. Also, comparing it to pseudoplastic behavior, it was found that the radial flow regime in the Newtonian zone of dilatant fluids took longer to form regarding both the flow behavior index and consistency factor.
A modelling and experimental study of the bubble trajectory in a non-Newtonian crystal suspension
Energy Technology Data Exchange (ETDEWEB)
Hassan, N M S [Process Engineering and Light Metals (PELM) Centre, Faculty of Sciences, Engineering and Health, CQUniversity, Rockhampton, QLD 4702 (Australia); Khan, M M K; Rasul, M G, E-mail: m.rasul@cqu.edu.a [School of Engineering and Built Environment, Faculty of Sciences, Engineering and Health, CQUniversity, Rockhampton, QLD 4702 (Australia)
2010-12-15
This paper presents an experimental and computational study of air bubbles rising in a massecuite-equivalent non-Newtonian crystal suspension. The bubble trajectory inside the stagnant liquid of a 0.05% xanthan gum crystal suspension was investigated and modelled using the computational fluid dynamics (CFD) model to gain an insight into the bubble flow characteristics. The CFD code FLUENT was used for numerical simulation, and the bubble trajectory calculations were performed through a volume of fluid (VOF) model. The influences of the Reynolds number (Re), the Weber number (We) and the bubble aspect ratio (E) on the bubble trajectory are discussed. The conditions for the bubbles' path oscillations are identified. The experimental results showed that the path instability for the crystal suspension was less rapid than in water. The trajectory analysis indicated that 5.76 mm diameter bubbles followed a zigzag motion in the crystal suspension. Conversely, the smaller bubbles (5.76 mm) followed a path of least horizontal movement and larger bubbles (21.21 mm) produced more spiral motion within the crystal suspension. Path instability occurred for bubbles of 15.63 and 21.21 mm diameter, and they induced both zigzag and spiral trajectories within the crystal suspension. At low Re and We, smaller bubbles (5.76 mm) produced a zigzag trajectory, whereas larger bubbles (15.63 and 21.21 mm) showed both zigzag and spiral trajectories at intermediate and moderately high Re and We in the crystal suspension. The simulation results illustrated that a repeating pattern of swirling vortices was created for smaller bubbles due to the unstable wake and unsteady flow of these bubbles. This is the cause of the smaller bubbles moving in a zigzag way. Larger bubbles showed two counter-rotating trailing vortices at the back of the bubble. These vortices induced a velocity component to the gas-liquid interface and caused a deformation. Hence, the larger bubbles produced a path
The Construction of Hilbert Spaces over the Non-Newtonian Field
Directory of Open Access Journals (Sweden)
Uğur Kadak
2014-01-01
the novel presentations probably lead most naturally to the development of the non-Newtonian calculi. In this paper we introduce vector spaces over real and complex non-Newtonian field with respect to the *-calculus which is a branch of non-Newtonian calculus. Also we give the definitions of real and complex inner product spaces and study Hilbert spaces which are special type of normed space and complete inner product spaces in the sense of *-calculus. Furthermore, as an example of Hilbert spaces, first we introduce the non-Cartesian plane which is a nonlinear model for plane Euclidean geometry. Secondly, we give Euclidean, unitary, and sequence spaces via corresponding norms which are induced by an inner product. Finally, by using the *-norm properties of complex structures, we examine Cauchy-Schwarz and triangle inequalities.
Determination of the Köthe-Toeplitz Duals over the Non-Newtonian Complex Field
Directory of Open Access Journals (Sweden)
Uğur Kadak
2014-01-01
Full Text Available 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.
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.
Study on Forced Convective Heat Transfer of Non-Newtonian Nanofluids
Institute of Scientific and Technical Information of China (English)
Yurong He; Yubin Men; Xing Liu; Huilin Lu; Haisheng Chen; Yulong Ding
2009-01-01
This paper is concerned with the forced convective heat transfer of dilute liquid suspensions of nanoparticles (nanofluids) flowing through a straight pipe under laminar conditions. Stable nanofluids are formulated by using the high shear mixing and ultrasonication methods. They are then characterised for their size, surface charge, thermal and rheological properties and tested for their convective heat transfer behaviour. Mathematical model-ling is performed to simulate the convective heat transfer of nanofluids using a single phase flow model and con-sidering nanofluids as both Newtonian and non-Newtonian fluid. Both experiments and mathematical modelling show that nanofluids can substantially enhance the convective heat transfer. Analyses of the results suggest that the non-Newtonian character of nanofluids influences the overall enhancement, especially for nanofluids with an obvious non-Newtonian character.
The Rayleigh-Taylor instability of Newtonian and non-Newtonian fluids
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.
COMPUTER SIMULATION OF NON-NEWTONIAN FLOW AND MASS TRANSPORT THROUGH CORONARY ARTERIAL STENOSIS
Institute of Scientific and Technical Information of China (English)
李新宇; 温功碧; 李丁
2001-01-01
A numerical analysis of Newtonian and non-Newtonian flow in an axi-symmetric tube with a local constriction simulating a stenosed artery under steady and pulsatile flow conditions was carried out. Based on these results, the concentration fields of LDL ( low density lipoprotein ) and Albumin were discussed. According to the results, in great details the macromolecule transport influences of wall shear stress, non-Newtonian fluid character and the scale of the molecule etc are given. The results of Newtonian fluid flow and non Newtonian fluid flow , steady flow and pulsatile flow are compared. These investigations can provide much valuable information about the correlation between the flow properties, the macromolecule transport and the development of atherosclerosis.
Stability analysis of slot-entry hybrid journal bearings operating with non-newtonian lubricant
Directory of Open Access Journals (Sweden)
H.C. Garg
2015-09-01
Full Text Available This paper presents theoretical investigations of rheological effects of lubricant on stability parameters of various configurations of slot-entry hybrid journal bearing system. FEM has been used to solve Reynolds equation governing flow of lubricant in bearing clearance space along with restrictor flow equation using suitable iterative technique. The non-Newtonian lubricant has been assumed to follow cubic shear stress law. The stability parameters in terms of stiffness coefficients, damping coefficients, threshold speed and whirl frequency of different configurations of slot-entry hybrid journal bearing have been computed and presented for wide range of external load while operating with Newtonian and Non-Newtonian lubricants. The computed results reveal that variation of viscosity due to non-Newtonian behavior of lubricant affects bearing stability quite significantly. The results are presented in graphical form and logical conclusions are drawn to identify best possible configuration from stability point of view.
Beyond the Virtual Intracranial Stenting Challenge 2007: non-Newtonian and flow pulsatility effects.
Cavazzuti, Marco; Atherton, Mark; Collins, Michael; Barozzi, Giovanni
2010-09-17
The Virtual Intracranial Stenting Challenge 2007 (VISC'07) is becoming a standard test case in computational minimally invasive cerebrovascular intervention. Following views expressed in the literature and consistent with the recommendations of a report, the effects of non-Newtonian viscosity and pulsatile flow are reported. Three models of stented cerebral aneurysms, originating from VISC'07 are meshed and the flow characteristics simulated using commercial computational fluid dynamics (CFD) software. We conclude that non-Newtonian and pulsatile effects are important to include in order to discriminate more effectively between stent designs.
Applied holography for drop formation of non-Newtonian fluids in centrifugal atomizers
Timko, J. J.
Holography made possible the analysis of drop formation in Newtonian and non-Newtonian fluids. The drops were illuminated at the moment of their formation with an impulse ruby laser, and from the holograms the whole spray was reconstructed with a closed-circuit TV loop. From the pictures taken from different planes of the spray, the size and the spatial distribution of the drops were determined with an electrooptical analyzer. The holographic measuring method provided quantitative data phenomena which were qualitatively observable on high-speed films. The experiments also verified an equation involving dimensionless criteria, deduced fo the atomization of non-Newtonian substances.
A fractional model for time-variant non-Newtonian flow
Directory of Open Access Journals (Sweden)
Yang Xu
2017-01-01
Full Text Available This work applies a fractional flow model to describe a time-variant behavior of non-Newtonian substances. Specifically, we model the physical mechanism underlying the thixotropic and anti-thixotropic phenomena of non-Newtonian flow. This study investigates the behaviors of cellulose suspensions and SMS pastes under constant shear rate. The results imply that the presented model with only two parameters is adequate to fit experimental data. Moreover, the parameter of fractional order is an appropriate index to characterize the state of given substances. Its value indicates the extent of thixotropy and anti-thixotropy with positive and negative order respectively.
Stagnation point flow of an non-Newtonian visco-elastic fluid
Energy Technology Data Exchange (ETDEWEB)
Teipel, I. [Univ. of Hannover, Inst. of Mechanics, Hannover (Germany)
1985-07-01
In this paper the flow near a two-dimensional stagnation point for a particular non-Newtonian fluid has been studied. Non-Newtonian fluids form a wide class of different materials, which will be used very often in chemical industries. From a practical point of view it is of great importance to obtain some results for example concerning the flow rate and the losses in a tube, the drag and the separation point of a boundary layer flow etc. for such fluids. Therefore it is necessary to assume a particular constitutive equation to calculate various aspects. (author)
Numerical Modelling of Non-Newtonian Fluid in a Rotational Cross-Flow MBR
DEFF Research Database (Denmark)
Bentzen, Thomas Ruby; Ratkovich, Nicolas Rios; Rasmussen, Michael R.
2011-01-01
. Validation of the CFD model was made against LDA tangential velocity measurements (error less than 8 %) using water a fluid. The shear stress over the membrane surface was inferred from the CFD simulations for water. However, activated sludge is a non-Newtonian liquid, for which the CFD model was modified...... incorporating the non-Newtonian behaviour of activated sludge. Shear stress and area-weighted average shear stress relationships were made giving error less that 8 % compared to the CFD results. An empirical relationship for the area-weighted average shear stress was developed for water and activated sludge...
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.
Validation of computational non-Newtonian fluid model for membrane bioreactor
DEFF Research Database (Denmark)
Sørensen, Lasse; Bentzen, Thomas Ruby; Skov, Kristian
2015-01-01
for optimizing MBR-systems is computational fluid dynamics (CFD) modelling, giving 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 10 compared to conventional activated sludge (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...
Entropy generation in non-Newtonian ﬂuid ﬂow in a slider bearing
Indian Academy of Sciences (India)
M Pakdemirli; B S Yilbas; M Yurusoy
2004-12-01
In the present study, entropy production in ﬂow ﬁelds due to slider bearings is formulated. The rate of entropy generation is computed for different ﬂuid properties and geometric conﬁgurations of the slider bearing. In order to account for the non-Newtonian effect, a special type of third-grade ﬂuid is considered. It is found that the rate of entropy generation is inﬂuenced signiﬁcantly by the height of the bearing clearance and the non-Newtonian parameter of the ﬂuid.
Deposition Velocities of Newtonian and Non-Newtonian Slurries in Pipelines
Energy Technology Data Exchange (ETDEWEB)
Poloski, Adam P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Adkins, Harold E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Abrefah, John [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Casella, Andrew M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Hohimer, Ryan E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nigl, Franz [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Minette, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Toth, James J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Tingey, Joel M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Yokuda, Satoru T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
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.
The wall shear rate in non-Newtonian turbulent pipe flow
Trinh, K T
2010-01-01
This paper presents a method for calculating the wall shear rate in pipe turbulent flow. It collapses adequately the data measured in laminar flow and turbulent flow into a single flow curve and gives the basis for the design of turbulent flow viscometers. Key words: non-Newtonian, wall shear rate, turbulent, rheometer
Pulsatile Non-Newtonian Laminar Blood Flows through Arterial Double Stenoses
Directory of Open Access Journals (Sweden)
Mir Golam Rabby
2014-01-01
Full Text Available The paper presents a numerical investigation of non-Newtonian modeling effects on unsteady periodic flows in a two-dimensional (2D pipe with two idealized stenoses of 75% and 50% degrees, respectively. The governing Navier-Stokes equations have been modified using the Cartesian curvilinear coordinates to handle complex geometries. The investigation has been carried out to characterize four different non-Newtonian constitutive equations of blood, namely, the (i Carreau, (ii Cross, (iii Modified Casson, and (iv Quemada models. The Newtonian model has also been analyzed to study the physics of fluid and the results are compared with the non-Newtonian viscosity models. The numerical results are represented in terms of streamwise velocity, pressure distribution, and wall shear stress (WSS as well as the vorticity, streamlines, and vector plots indicating recirculation zones at the poststenotic region. The results of this study demonstrate a lower risk of thrombogenesis at the downstream of stenoses and inadequate blood supply to different organs of human body in the Newtonian model compared to the non-Newtonian ones.
STUDIES OF THE REDUCTION OF PIPE FRICTION WITH THE NON-NEWTONIAN ADDITIVE CMC,
water can remarkably reduce the frictional resistance to flow. The material sodium carboxymethylcellulose was added to fresh water and subjected to...pipe friction tests under a wide range of shear rates, additive concentration, and temperature conditions. The frictional data are characterized by application of the power law expression for non-Newtonian fluids. (Author)
Free surface flow of a suspension of rigid particles in a non-Newtonian fluid
DEFF Research Database (Denmark)
Svec, Oldrich; Skocek, Jan; Stang, Henrik
2012-01-01
A numerical framework capable of predicting the free surface flow of a suspension of rigid particles in a non-Newtonian fluid is described. The framework is a combination of the lattice Boltzmann method for fluid flow, the mass tracking algorithm for free surface representation, the immersed...
Application of the homotopy method for analytical solution of non-Newtonian channel flows
Energy Technology Data Exchange (ETDEWEB)
Roohi, Ehsan [Department of Aerospace Engineering, Sharif University of Technology, PO Box 11365-8639, Azadi Avenue, Tehran (Iran, Islamic Republic of); Kharazmi, Shahab [Department of Mechanical Engineering, Sharif University of Technology, PO Box 11365-8639, Azadi Avenue, Tehran (Iran, Islamic Republic of); Farjami, Yaghoub [Department of Computer Engineering, University of Qom, Qom (Iran, Islamic Republic of)], E-mail: roohi@sharif.edu
2009-06-15
This paper presents the homotopy series solution of the Navier-Stokes and energy equations for non-Newtonian flows. Three different problems, Couette flow, Poiseuille flow and Couette-Poiseuille flow have been investigated. For all three cases, the nonlinear momentum and energy equations have been solved using the homotopy method and analytical approximations for the velocity and the temperature distribution have been obtained. The current results agree well with those obtained by the homotopy perturbation method derived by Siddiqui et al (2008 Chaos Solitons Fractals 36 182-92). In addition to providing analytical solutions, this paper draws attention to interesting physical phenomena observed in non-Newtonian channel flows. For example, it is observed that the velocity profile of non-Newtonian Couette flow is indistinctive from the velocity profile of the Newtonian one. Additionally, we observe flow separation in non-Newtonian Couette-Poiseuille flow even though the pressure gradient is negative (favorable). We provide physical reasoning for these unique phenomena.
On line and double integrals in the non-Newtonian sense
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.
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…
Revisiting Newtonian and Non-Newtonian Fluid Mechanics Using Computer Algebra
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,…
HARNACK ESTIMATES FOR WEAK SOLUTIONSOFEQUATIONS OF NON-NEWTONIAN POLYTROPIC FILTRATION
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
An intrinsic Harnack estimate and some sup-estimates are established for nonnegative weak solutions of equations of non-Newtonian polytropic filtration ut -div(｜Dum ｜p-2Dum) =0, m(p- 1) ＜ 1, m＞0, p＞ 1.
RANDOM ATTRACTOR FOR A TWO-DIMENSIONAL INCOMPRESSIBLE NON-NEWTONIAN FLUID WITH MULTIPLICATIVE NOISE
Institute of Scientific and Technical Information of China (English)
Zhao Caidi; Li Yongsheng; Zhou Shengfan
2011-01-01
This article proves that the random dynamical system generated by a two- dimensional incompressible non-Newtonian fluid with multiplicative noise has a global random attractor, which is a random compact set absorbing any bounded nonrandom subset of the phase space.
Modeling of flow of particles in a non-Newtonian fluid using lattice Boltzmann method
DEFF Research Database (Denmark)
Skocek, Jan; Svec, Oldrich; Spangenberg, Jon
2011-01-01
is necessary. In this contribution, the model at the scale of aggregates is introduced. The conventional lattice Boltzmann method for fluid flow is enriched with the immersed boundary method with direct forcing to simulate the flow of rigid particles in a non- Newtonian liquid. Basic ingredients of the model...
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.
Learning about Non-Newtonian Fluids in a Student-Driven Classroom
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…
Unsteady Non-Newtonian Solver on Unstructured Grid for the Simulation of Blood Flow
Directory of Open Access Journals (Sweden)
Guojie Li
2013-01-01
Full Text Available Blood is in fact a suspension of different cells with yield stress, shear thinning, and viscoelastic properties, which can be represented by different non-Newtonian models. Taking Casson fluid as an example, an unsteady solver on unstructured grid for non-Newtonian fluid is developed to simulate transient blood flow in complex flow region. In this paper, a steady solver for Newtonian fluid is firstly developed with the discretization of convective flux, diffusion flux, and source term on unstructured grid. For the non-Newtonian characteristics of blood, the Casson fluid is approximated by the Papanastasiou's model and treated as Newtonian fluid with variable viscosity. Then considering the transient property of blood flow, an unsteady non-Newtonian solver based on unstructured grid is developed by introducing the temporal term by first-order upwind difference scheme. Using the proposed solver, the blood flows in carotid bifurcation of hypertensive patients and healthy people are simulated. The result shows that the possibility of the genesis and development of atherosclerosis is increased, because of the increase in incoming flow shock and backflow areas of the hypertensive patients, whose WSS was 20~87.1% lower in outer vascular wall near the bifurcation than that of the normal persons and 3.7~5.5% lower in inner vascular wall downstream the bifurcation.
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…
Revisiting Newtonian and Non-Newtonian Fluid Mechanics Using Computer Algebra
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,…
A Colorful Mixing Experiment in a Stirred Tank Using Non-Newtonian Blue Maize Flour Suspensions
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…
Heat Transfer of Non-Newtonian Dilatant Power Law Fluids in Square and Rectangular Cavities
Directory of Open Access Journals (Sweden)
I. Vinogradov
2011-01-01
Full Text Available Steady two-dimensional natural convection in fluid filled cavities is numerically investigated for the case of non- Newtonian shear thickening power law liquids. The conservation equations of mass, momentum and energy under the assumption of a Newtonian Boussinesq fluid have been solved using the finite volume method for Newtonian and non-Newtonian fluids. The computations were performed for a Rayleigh number, based on cavity height, of 105 and a Prandtl number of 100. In all of the numerical experiments, the channel is heated from below and cooled from the top with insulated side-walls and the inclination angle is varied. The simulations have been carried out for aspect ratios of 1 and 4. Comparison between the Newtonian and the non-Newtonian cases is conducted based on the dependence of the average Nusselt number on angle of inclination. It is shown that despite significant variation in heat transfer rate both Newtonian and non-Newtonian fluids exhibit similar behavior with the transition from multi-cell flow structure to a single-cell regime.
Viscous flow past a collapsible channel as a model for self-excited oscillation of blood vessels.
Tang, Chao; Zhu, Luoding; Akingba, George; Lu, Xi-Yun
2015-07-16
Motivated by collapse of blood vessels for both healthy and diseased situations under various circumstances in human body, we have performed computational studies on an incompressible viscous fluid past a rigid channel with part of its upper wall being replaced by a deformable beam. The Navier-Stokes equations governing the fluid flow are solved by a multi-block lattice Boltzmann method and the structural equation governing the elastic beam motion by a finite difference method. The mutual coupling of the fluid and solid is realized by the momentum exchange scheme. The present study focuses on the influences of the dimensionless parameters controlling the fluid-structure system on the collapse and self-excited oscillation of the beam and fluid dynamics downstream. The major conclusions obtained in this study are described as follows. The self-excited oscillation can be intrigued by application of an external pressure on the elastic portion of the channel and the part of the beam having the largest deformation tends to occur always towards the end portion of the deformable wall. The blood pressure and wall shear stress undergo significant variations near the portion of the greatest oscillation. The stretching motion has the most contribution to the total potential elastic energy of the oscillating beam.
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.
Studying mixing in Non-Newtonian blue maize flour suspensions using color analysis.
Directory of Open Access Journals (Sweden)
Grissel Trujillo-de Santiago
Full Text Available 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.
Entropy generation in a pipe due to non-Newtonian ﬂuid ﬂow: Constant viscosity case
Indian Academy of Sciences (India)
M Pakdemirli; B S Yilbas
2006-02-01
Non-Newtonian ﬂuid ﬂow in a pipe system is considered and a third grade non-Newtonian ﬂuid is employed in the analysis. The velocity and temperature distributions across the pipe are presented. Entropy generation number due to heat transfer and ﬂuid friction is formulated. The inﬂuences of non-Newtonian parameter and Brinkman number on entropy generation number are examined. It is found that increasing the non-Newtonian parameter reduces the ﬂuid friction in the region close to the pipe wall. This in turn results in low entropy generation with increasing non-Newtonian parameter. Increasing Brinkman number enhances the ﬂuid friction and heat transfer rates; in which case, entropy number increases with increasing Brinkman number.
Yang, Chun; Tang, Dalin; Yuan, Chun; Hatsukami, Thomas S; Zheng, Jie; Woodard, Pamela K
2007-01-01
It has been recognized that fluid-structure interactions (FSI) play an important role in cardiovascular disease initiation and development. However, in vivo MRI multi-component FSI models for human carotid atherosclerotic plaques with bifurcation and quantitative comparisons of FSI models with fluid-only or structure-only models are currently lacking in the literature. A 3D non-Newtonian multi-component FSI model based on in vivo/ex vivo MRI images for human atherosclerotic plaques was introduced to investigate flow and plaque stress/strain behaviors which may be related to plaque progression and rupture. Both artery wall and plaque components were assumed to be hyperelastic, isotropic, incompressible and homogeneous. Blood flow was assumed to be laminar, non-Newtonian, viscous and incompressible. In vivo/ex vivo MRI images were acquired using histologically-validated multi-spectral MRI protocols. The 3D FSI models were solved and results were compared with those from a Newtonian FSI model and wall-only/fluid-only models. A 145% difference in maximum principal stresses (Stress-P(1)) between the FSI and wall-only models and 40% difference in flow maximum shear stress (MSS) between the FSI and fluid-only models were found at the throat of the plaque using a severe plaque sample (70% severity by diameter). Flow maximum shear stress (MSS) from the rigid wall model is much higher (20-40% in maximum MSS values, 100-150% in stagnation region) than those from FSI models.
Wall effects on the terminal velocity of spherical particles in Newtonian and non-Newtonian fluids
Directory of Open Access Journals (Sweden)
ATAÍDE C. H.
1999-01-01
Full Text Available The objective of this work is to study the effect of confining walls on the free settling of spherical particles along the axes of five vertical cylindrical tubes in Newtonian and non-Newtonian liquids. Experimental results were predominantly obtained in the particle flow region between the Stokes and the Newton regimes (intermediate region and displayed Reynolds numbers in the ranges 0.7
Spreading of Non-Newtonian and Newtonian Fluids on a Solid Substrate under Pressure
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.
Spreading of Non-Newtonian and Newtonian Fluids on a Solid Substrate under Pressure
Energy Technology Data Exchange (ETDEWEB)
Choudhury, Moutushi Dutta; Chandra, Subrata; Nag, Soma; Tarafdar, Sujata [Condensed Matter Physics Research Centre, Physics Department, Jadavpur University, Kolkata 700032 (India); Das, Shantanu, E-mail: mou15july@gmail.com [Reactor Control Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India)
2011-09-15
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.
On predicting the onset of transient convection in porous media saturated with Non-Newtonian liquid
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
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.
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.
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.
Turbulent Characteristic of Liquid Around a Chain of Bubbles in Non-Newtonian Fluid
Institute of Scientific and Technical Information of China (English)
李少白; 马友光; 朱春英; 付涛涛; 李怀志
2012-01-01
The turbulence behavior of gas-liquid two-phase flow plays an important role in heat transfer and mass transfer in many chemical processes. In this work, a 2D particle image velocimetry (PIV) was used to investigate the turbulent characteristic of fluid induced by a chain of bubbles rising in Newtonian and non-Newtonian fluids. The instantaneous flow field, turbulent kinetic energy (TKE) and TKE dissipation rate were measured. The results demonstrated that the TKE profiles were almost symmetrical along the column center and showed higher values in the central region of the column. The TKE was enhanced with the increase of gas flow and decrease of liquid viscosity. The maximum TKE dissipation rate appeared on both sides of the bubble chain, and increased with the increase of gas flow rate or liquid viscosity. These results provide an understanding for gas-liquid mass transfer in non-Newtonian fluids.
A comparison of numerical methods for non-Newtonian fluid flows in a sudden expansion
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.
Non-Newtonian Viscosity Modeling of Crude Oils—Comparison Among Models
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.
The effect of the expansion ratio on a turbulent non-Newtonian recirculating flow
Energy Technology Data Exchange (ETDEWEB)
Pereira, A.S. [Departamento de Engenharia Quimica Instituto Superior de Engenharia do Porto (Portugal); Pinho, F.T. [Centro de Estudos de Fenomenos de Transporte, DEMEGI, Faculdade de Engenharia, Universidade do Porto (Portugal)
2002-04-01
Measurements of the mean and turbulent flow characteristics of shear-thinning moderately elastic 0.1% and 0.2% xanthan gum aqueous solutions were carried out in a sudden expansion having a diameter ratio of 2. The inlet flow was turbulent and fully developed, and the results were compared with data for water in the same geometry and with previous published Newtonian and non-Newtonian data in a smaller expansion of diameter ratio equal to 1.538. An increase in expansion ratio led to an increase in the recirculation length and in the axial normal Reynolds stress at identical normalised locations, but the difference between Newtonian and non-Newtonian characteristics was less intense than in the smaller expansion. An extensive comparison of mean and turbulent flow characteristics was carried out in order to understand the variation of flow features. (orig.)
Non-Newtonian ﬂuid ﬂow in annular pipes and entropy generation: Temperature-dependent viscosity
Indian Academy of Sciences (India)
M Yürüsoy; B S Yilbaş; M Pakdemirli
2006-12-01
Non-Newtonian ﬂuid ﬂow in annular pipes is considered and the entropy generation due to ﬂuid friction and heat transfer in them is formulated. A third-grade ﬂuid is employed to account for the non-Newtonian effect, while the Reynolds model is accommodated for temperature-dependent viscosity. Closed-form solutions for velocity, temperature, and entropy ﬁelds are presented. It is found that entropy generation number increases with reducing non-Newtonian parameter, while it is the reverse for the viscosity parameter, which is more pronounced in the region close to the annular pipe inner wall.
Increasing heat transfer of non-Newtonian nanofluid in rectangular microchannel with triangular ribs
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 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).
Directory of Open Access Journals (Sweden)
Yan Zhang
2011-01-01
Full Text Available The problem of steady, laminar, thermal Marangoni convection flow of non-Newtonian power law fluid along a horizontal surface with variable surface temperature is studied. The partial differential equations are transformed into ordinary differential equations by using a suitable similarity transformation and analytical approximate solutions are obtained by an efficient transformation, asymptotic expansion and Padé approximants technique. The effects of power law index and Marangoni number on velocity and temperature profiles are examined and discussed.
Smart Fluids in Hydrology: Use of Non-Newtonian Fluids for Pore Structure Characterization
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
Matrix Transformations between Certain Sequence Spaces over the Non-Newtonian Complex Field
Uğur Kadak; Hakan Efe
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 ...
Non-Newtonian Momentum Transfer past an Isothermal Stretching Sheet with Applied Suction
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.
Simulation of Non-Newtonian Blood Flow by Lattice Boltzman Method
Institute of Scientific and Technical Information of China (English)
JI Yu-Pin; KANG Xiu-Ying; LIU Da-He
2010-01-01
@@ Blood flow under various conditions of vessel is simulated as a non-Newtonian fluid by the two-dimensional Lattice Boltzmann method,in which the Casson model is used to express the relationship between viscosity and shear rate of the blood.The flow field distributions at certain sites near the narrowing and bifurcation of the vessel explain the hemodynamic mechanism of the preclilection of the atherosclerotic lesions for these sites which are consistent with that found by medical studies.
Flow non-normality-induced transient growth in superposed Newtonian and non-Newtonian fluid layers
Ridolfi, Luca; Camporeale, Carlo Vincenzo
2009-01-01
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...
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.
BLOW-UP ESTIMATES FOR A NON-NEWTONIAN FILTRATION SYSTEM
Institute of Scientific and Technical Information of China (English)
杨作东; 陆启韶
2001-01-01
The prior estimate and decay property of positive solutions are derived for a system of quasi-linear elliptic differential equations first. Hence, the result of non-existence for differential equation system of radially nonincreasing positive solutions is implied. By using this non-existence result, blow-up estimates for a class quasi-linear reaction-diffusion systems (non-Newtonian filtration systems ) are established, which extends the result of semi- linear reaction- diffusion ( Fujita type ) systems .
Institute of Scientific and Technical Information of China (English)
Zhongping LI; Wanjuan DU; Chunlai MU
2013-01-01
In this paper,we first find finite travelling-wave solutions,and then investigate the short time development of interfaces for non-Newtonian diffusion equations with strong absorption.We show that the initial behavior of the interface depends on the concentration of the mass of u(x,0) near x =0.More precisely,we find a critical value of the concentration,which separates the heating front of interfaces from the cooling front of them.
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.
Modeling and prediction of non-Newtonian viscosity of crude oils
Energy Technology Data Exchange (ETDEWEB)
Ramirez-Gonzalez, P.V. [Univ. Nacional Autonoma de Mexico (Mexico). Dept. de Ingenieria Quimica; Quinones-Cisneros, S.E.; Manero, O. [Univ. Nacional Autonoma de Mexico (Mexico). Dept. de Reologia, Inst. de Investigaciones en Materiales; Creek, J. [Chevron Energy Technology Co., Houston, TX (United States); Deiters, U.K. [Cologne Univ., Cologne (Germany). Inst. of Physical Chemistry
2008-07-01
Non-Newtonian rheological behaviour in crude oils can be induced by the presence of precipitated wax in reservoir fluids or by low ambient temperatures in heavy oils. This type of behaviour exists at low temperature operating conditions in deep-water production, or in the case of vapor extraction (VAPEX) processes of heavy oils involving strong compositional related changes to the already non-Newtonian viscosity of the oil. Reliable rheological models are needed for crude oils over the wide range of conditions that the fluid may encounter. The models should be of a compositional nature because the rheological behaviour of the fluid must be predicted in many applications, including VAPEX processes or fluid blending for piping. This study compared some published models that describe the non-Newtonian behaviour of crude oils. The emphasis was on the stability of the models predictions within the wide range of conditions that may be encountered. The study also evaluated the prediction potential of the analyzed models.
Studies on heat transfer to Newtonian and non-Newtonian fluids in agitated vessel
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).
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.
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.
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.
Mixed convection heat transfer from a vertical plate to non-Newtonian fluids
Wang, T.-Y.
1995-02-01
The nonsimilar boundary-layer analysis of steady laminar mixed-convection heat transfer between a vertical plate and non-Newtonian fluids is extended and unified. A mixed-convection parameter zeta is proposed to replace the conventional Richardson number, Gr/Re(exp 2/(2 - n)) and to serve as a controlling parameter that determines the relative importance of the forced and the free convection. The value of mixed-convection parameter lies between 0 and 1. In addition, the power-law model is used for non-Newtonian fluids with exponent n less than 1 for pseudoplastics; n = 1 for Newtonian fluids; and n greater than 1 for dilatant fluids. Furthermore, the coordinates and dependent variables are transformed to yield computationally efficient numerical solutions that are valid over the entire range of mixed convection, from the pure forced-convection limit to the pure free-convection limit, and the whole domain of non-Newtonian fluids, from pseudoplastics to dilatant fluids. The effects of the mixed-convection parameter, the power-law viscosity index, and the generalized Prandtl number on the velocity profiles, the temperature profiles, as well as on the wall skin friction and heat transfer rate are clearly illustrated for both cases of buoyancy assisting and opposing flow conditions.
Experiments on densely-loaded non-Newtonian slurries in laminar and turbulent pipe flows
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.
Pore-Scale Modeling of Non-Newtonian Flow in Porous Media
Sochi, Taha
2010-01-01
The thesis investigates the flow of non-Newtonian fluids in porous media using pore-scale network modeling. Non-Newtonian fluids show very complex time and strain dependent behavior and may have initial yield stress. Their common feature is that they do not obey the simple Newtonian relation of proportionality between stress and rate of deformation. They are generally classified into three main categories: time-independent, time-dependent and viscoelastic. Two three-dimensional networks representing a sand pack and Berea sandstone were used. An iterative numerical technique is used to solve the pressure field and obtain the flow rate and apparent viscosity. The time-independent category is investigated using two fluid models: Ellis and Herschel-Bulkley. The analysis confirmed the reliability of the non-Newtonian network model used in this study. Good results are obtained, especially for the Ellis model, when comparing the network model results to experimental data sets found in the literature. The yield-stres...
Directory of Open Access Journals (Sweden)
J. Javorova
2016-06-01
Full Text Available The purpose of this paper is to study the performance of a finite length journal bearing, taking into account effects of non-Newtonian Rabinowitsch flow rheology and elastic deformations of the bearing liner. According to the Rabinowitsch fluid model, the cubic-stress constitutive equation is used to account for the non-Newtonian effects of pseudoplastic and dilatant lubricants. Integrating the continuity equation across the film, the nonlinear non-Newtonian Reynolds-type equation is derived. The elasticity part of the problem is solved on the base of Vlassov model of an elastic foundation. The numerical solution of the modified Reynolds equation is carried out by using FDM with over-relaxation technique. The results for steady state bearing performance characteristics have been calculated for various values of nonlinear factor and elasticity parameters. It was concluded that in comparison with the Newtonian lubricants, higher values of film pressure and load carrying capacity have been obtained for dilatant lubricants, while the case was reversed for pseudoplastic lubricants.
Directory of Open Access Journals (Sweden)
Hailong Ye
2015-04-01
Full Text Available Uniqueness of self-similar very singular solutions with compact support are proved for the non-Newtonian polytropic filtration equation with gradient absorption $$ \\frac{\\partial u}{\\partial t} =\\hbox{div}(|\
NUMERICAL ANALYSIS OF THE NON-NEWTONIAN BLOOD FLOW IN THE NON-PLANAR ARTERY WITH BIFURCATION
Institute of Scientific and Technical Information of China (English)
CHEN Jie; LU Xi-yun; ZHUANG Li-xian; WANG Wen
2004-01-01
A numerical analysis of non-Newtonian fluid flow in non-planar artery with bifurcation was performed by using a finite element method to solve the three-dimensional Navier-Stokes equations coupled with the non-Newtonian constitutive models, including Carreau,Cross and Bingham models. The objective of this study is to investigate the effects of the non-Newtonian properties of blood as well as curvature and out-of-plane geometry in the non-planar daughter vessels on the velocity distribution and wall shear stress. The results of this study support the view that the non-planarity of blood vessels and the non-Newtonian properties of blood are of important in hemodynamics and play a significant role in vascular biology and pathophysiology.
Viscous Driving of Global Oscillations in Accretion Discs Around Black Holes
Miranda, Ryan; Lai, Dong
2014-01-01
We examine the role played by viscosity in the excitation of non-axisymmetric global oscillation modes in accretion discs around black holes using two-dimensional hydrodynamic simulations. The turbulent viscosity is modeled by the $\\alpha$-ansatz, with different equations of state. We consider both discs with transonic radial inflows across the innermost stable circular orbit, and stationary discs truncated by a reflecting wall at their inner edge, representing a magnetosphere. In transonic discs, viscosity can excite several types of global oscillation modes. These modes are either axisymmetric with frequencies close to multiples of the maximum radial epicyclic frequency $\\kappa_\\mathrm{max}$, non-axisymmetric with frequencies close to multiples of of the innermost stable orbit frequency $\\Omega_\\mathrm{ISCO}$, or hybrid modes whose frequencies are linear combinations of these two frequencies. Small values of the viscosity parameter $\\alpha$ primarily produce non-axisymmetric modes, while axisymmetric modes ...
Oscillations in solar Jets Observed with the SOT of Hinode: Viscous Effects during Reconnection
Tavabi, Ehsan
2014-01-01
Transverse oscillatory motions and recurrence behavior in the chromospheric jets observed by Hinode/SOT are studied. A comparison is considered with the behavior that was noticed in coronal X-ray jets observed by Hinode/XRT. A jet like bundle observed at the limb in Ca II H line appears to show a magnetic topology that is similar to X-ray jets (i.e., the Eiffel tower shape). The appearance of such magnetic topology is usually assumed to be caused by magnetic reconnection near a null point. Transverse motions of the jet axis are recorded but no clear evidence of twist is appearing from the highly processed movie. The aim is to investigate the dynamical behavior of an incompressible magnetic X-point occurring during the magnetic reconnection in the jet formation region. The viscous effect is specially considered in the closed line-tied magnetic X-shape nulls. We perform the MHD numerical simulation in 2-D by solving the visco-resistive MHD equations with the tracing of velocity and magnetic field. A qualitative...
Smart Fluids in Hydrology: Use of Non-Newtonian Fluids for Pore Structure Characterization
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.
Microbubble oscillating in a microvessel filled with viscous fluid: A finite element modeling study.
Chen, Chuyi; Gu, Yuyang; Tu, Juan; Guo, Xiasheng; Zhang, Dong
2016-03-01
Understanding the dynamics of coated-microbubble oscillating in an elastic microvessel is important for effective and safe applications of ultrasound contrast agents (UCAs) in imaging and therapy. Numerical simulations are performed based on a two-dimensional (2D) asymmetric finite element model to investigate the influences of both acoustic driving parameters (e.g., pressure and frequency) and material properties (vessel size, microbubble shell visco-elastic parameters and fluid viscosity) on the dynamic interactions in the bubble-blood-vessel system. The results show that, the constrained effect of the blood vessel along the radial direction will induce the asymmetric bubble oscillation and vessel deformation, as well as shifting the bubble resonance frequency toward the higher frequency range. For a bubble (1.5-μm radius) activated by 1-MHz ultrasound pulses in a microvessel with a radius varying between 2 and 6.5 μm, up to 26.95 kPa shear stress could be generated on the vessel wall at a driving pressure of 0.2 MPa, which should be high enough to damage the vascular endothelial cells. The asymmetrical oscillation ratio of the bubble can be aggravated from 0.12% to 79.94% with the increasing acoustic driving pressure and blood viscosity, or the decreasing vessel size and microbubble shell visco-elastic properties. The maximum compression velocity on the bubble shell will be enhanced from 0.19 to 22.79 m/s by the increasing vessel size and acoustic pressure, or the decreasing microbubble shell visco-elasticity and blood viscosity. As the results, the peak values of microstreaming-induced shear stress on the vessel wall increases from 0.003 to 26.95 kPa and the deformation degree of vessel is raised from 1.01 to 1.49, due to the enhanced acoustic amplitude, or the decreasing vessel size, blood viscosity and microbubble shell visco-elasticity. Moreover, it also suggests that, among above impact parameters, microbubble resonance frequency and UCA shell elasticity
Numerical Solution of Hydrodynamics Lubrications with Non-Newtonian Fluid Flow
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.
Non-Newtonian Couette-Poiseuille flow of a dilute gas
Tij, Mohamed; Santos, Andrés
2010-01-01
The steady state of a dilute gas enclosed between two infinite parallel plates in relative motion and under the action of a uniform body force parallel to the plates is considered. The Bhatnagar-Gross-Krook model kinetic equation is analytically solved for this Couette-Poiseuille flow to first order in the force and for arbitrary values of the Knudsen number associated with the shear rate. This allows us to investigate the influence of the external force on the non-Newtonian properties of the...
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.
An overview on the non-newtonian calculus and its potential applications to economics
Filip, Diana; Piatecki, Cyrille
2014-01-01
20; Until now, non-newtonian calculus, multiplicative calculus in particular, has been presented as a curiosity and is nearly ignored for the social scientists field. In this paper, after a brief presentation of this calculus, we try to show how it could be used to re-explore from another perspective classical economic theory, more particularly the economic growth and in the maximum likelihood method from statistics.; Jusqu'à présent, le calcul non-newtonien, calcul multiplicatif en particuli...
Learning about non-Newtonian fluids in a student-driven classroom
Dounas-Frazer, D R; Zaniewski, A M; Roth, N
2012-01-01
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.
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.
Simulation of non-Newtonian oil-water core annular flow through return bends
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.
Non-Newtonian behavior and molecular structure of Cooee bitumen under shear flow
DEFF Research Database (Denmark)
Lemarchand, Claire; Bailey, Nicholas; Daivis, Peter
2015-01-01
The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear are investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity, normal stress differences, and pressure of the bitumen mixture are computed at different shear...... rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid at all temperatures. In addition, the Cooee model is able to reproduce experimental results showing the formation of nanoaggregates composed of stacks of flat aromatic molecules in bitumen. These nanoaggregates...
Pullback Asymptotic Behavior of Solutions for a 2D Non-autonomous Non-Newtonian Fluid
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.
Hodographic study of non-Newtonian MHD aligned steady plane fluid flows
Directory of Open Access Journals (Sweden)
P. V. Nguyen
1990-01-01
Full Text Available A study is made of non-Newtonian HHD aligned steady plane fluid flows to find exact solutions for various flow configurations. The equations of motion have been transformed to the hodograph plane. A Legendre-transform function is used to recast the equations in the hodograph plane in terms of this transform function. Solutions for various flow configurations are obtained. Applications are investigated for the fluids of finite and infinite electrical conductivity bringing out the similarities and contrasts in the solutions of these types of fluids.
Non-Newtonian Liquid Flow through Small Diameter Piping Components: CFD Analysis
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.
A Lagrangian finite element method for the simulation of flow of non-newtonian liquids
DEFF Research Database (Denmark)
Hassager, Ole; Bisgaard, C
1983-01-01
A Lagrangian method for the simulation of flow of non-Newtonian liquids is implemented. The fluid mechanical equations are formulated in the form of a variational principle, and a discretization is performed by finite elements. The method is applied to the slow of a contravariant convected Maxwell...... liquid around a sphere moving axially in a cylinder. The simulations show that the friction factor for a sphere in a narrow cylinder is a rapidly decreasing function of the Deborah number, while the friction factor for a sphere in a very wide cylinder is not significantly affected by fluid elasticity...
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.
Institute of Scientific and Technical Information of China (English)
Yang Yongkuang; Yang Rongtai; Ho Minghsiung; Jheng Mingchang
2004-01-01
A novel numerical method to lubricate a conventional finite diameter conical(cylindrical bearing with a non-Newtonian lubricant, while adhering to the power-law model, is presented. The elastic deformation of bearing and varied viscosity of lubrication due to the pressure distribution of film thickness are also considered. Simulation results indicate that the normal load carrying capacity is more pronounced for higher values of flow behavior index n, higher eccentricity ratios and larger misalignment factors. It is found that the viscosity-pressure to the effect of lubricant viscosity is significant.
Nonlinear shear wave in a non Newtonian visco-elastic medium
Energy Technology Data Exchange (ETDEWEB)
Banerjee, D.; Janaki, M. S.; Chakrabarti, N. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064 (India); Chaudhuri, M. [Max-Planck-Institut fuer extraterrestrische Physik, 85741 Garching (Germany)
2012-06-15
An analysis of nonlinear transverse shear wave has been carried out on non-Newtonian viscoelastic liquid using generalized hydrodynamic model. The nonlinear viscoelastic behavior is introduced through velocity shear dependence of viscosity coefficient by well known Carreau-Bird model. The dynamical feature of this shear wave leads to the celebrated Fermi-Pasta-Ulam problem. Numerical solution has been obtained which shows that initial periodic solutions reoccur after passing through several patterns of periodic waves. A possible explanation for this periodic solution is given by constructing modified Korteweg de Vries equation. This model has application from laboratory to astrophysical plasmas as well as in biological systems.
Structure of a binary mixture under shear: non-Newtonian effects from computer simulation
Energy Technology Data Exchange (ETDEWEB)
Hanley, H.J.M.; Evans, D.J.; Hess, S.
1983-02-01
A binary equimolar dense fluid mixture is subjected to a shear. The orientational distribution of particles of type i around particles of type j (i, j = 1, 2) and the distortion of the radial distribution function is discussed for planar Couette flow. Results are presented in terms of a mixture of soft spheres, for which one species differs substantially in size and mass from the other, simulated on the computer using the technique of shear nonequilbrium molecular dynamics. Transport coefficients, including those associated with normal pressure differences, are given for the mixture and for the species in the mixture. Non-Newtonian phenomena are observed.
Nonlinear Shear Wave in a Non Newtonian Visco-elastic Medium
Janaki, D Banerjee M S; Chaudhuri, M
2013-01-01
An analysis of nonlinear transverse shear wave has been carried out on non-Newtonian viscoelastic liquid using generalized hydrodynamic(GH) model. The nonlinear viscoelastic behavior is introduced through velocity shear dependence of viscosity coefficient by well known Carreau -Bird model. The dynamical feature of this shear wave leads to the celebrated Fermi-Pasta-Ulam (FPU) problem. Numerical solution has been obtained which shows that initial periodic solutions reoccur after passing through several patterns of periodic waves. A possible explanation for this periodic solution is given by constructing modified Korteweg de Vries (mKdV) equation. This model has application from laboratory to astrophysical plasmas as well as biological systems.
OPTIMAL MIXED H- P FINITE ELEMENT METHODS FOR STOKES AND NON-NEWTONIAN FLOW
Institute of Scientific and Technical Information of China (English)
Ping-bing Ming; Zhong-ci Shi
2001-01-01
Based upon a new mixed variational formulation for the three-field Stokes equations and linearized Non-Newtonian flow, an h -p finite element method is presented with or without a stabilization. As to the variational formulation without stabilization, optimal error bounds in h as well as in p are obtained. As with stabilization, optimal error bounds are obtained which is optimal in h and one order deterioration in p for the pressure, that is consistent with numerical results in [9, 12] and therefore solved the problem therein.Moreover, we proposed a stabilized formulation which is optimal in both h and p.
Non-newtonian flow and pressure drop of pineapple juice in a plate heat exchanger
CABRAL, R. A. F.; GUT, J. A. W.; V. R. N. Telis; Telis-Romero, J. [UNESP
2010-01-01
The study of non-Newtonian flow in plate heat exchangers (PHEs) is of great importance for the food industry. The objective of this work was to study the pressure drop of pineapple juice in a PHE with 50º chevron plates. Density and flow properties of pineapple juice were determined and correlated with temperature (17.4 < T < 85.8ºC) and soluble solids content (11.0 < Xs < 52.4 ºBrix). The Ostwald-de Waele (power law) model described well the rheological behavior. The friction factor for non-...
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.
Study on local resistance of non-Newtonian power law fluid in elbow pipes
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.
Zhao, Cunlu
2010-01-01
Numerical analyses of transient electro-osmosis of a typical non-Newtonian liquid induced by DC and AC electric fields in a rectangular microchannel are conducted in the framework of continuum fluid mechanics. The famous power-law constitutive model is used to express the fluid dynamic viscosity in terms of the velocity gradient. Transient start-up characteristics of electro-osmotic power-law liquid flow in rectangular microchannels are simulated by using finite element method. Under a DC electric field, it is found out and the fluid is more inert to the external electric field and the steady-state velocity profile becomes more plug-like with decrease of the flow behavior index of the power-law liquids. The numerical calculations also confirm the validity of the generalized Smoluchowski slip velocity which can serve as the counterpart for the classic Smoluchowski slip velocity when dealing with electrokinetic flow of non-Newtonian power-law fluids. Under AC electric fields, the fluid is more obviously acceler...
Generation of Oil Droplets in a Non-Newtonian Liquid Using a Microfluidic T-Junction
Directory of Open Access Journals (Sweden)
Enrico Chiarello
2015-11-01
Full Text Available We have compared the formation of oil drops in Newtonian and non-Newtonian fluids in a T-junction microfluidic device. As Newtonian fluids, we used aqueous solutions of glycerol, while as non-Newtonian fluids we prepared aqueous solutions of xanthan, a stiff rod-like polysaccharide, which exhibit strong shear-thinning effects. In the squeezing regime, the formation of oil droplets in glycerol solutions is found to scale with the ratio of the dispersed flow rate to the continuous one and with the capillary number associated to the continuous phase. Switching to xanthan solutions does not seem to significantly alter the droplet formation process. Any quantitative difference with respect to the Newtonian liquid can be accounted for by a suitable choice of the capillary number, corresponding to an effective xanthan viscosity that depends on the flow rates. We have deduced ample variations in the viscosity, on the order of 10 and more, during normal operation conditions of the T-junction. This allowed estimating the actual shear rates experienced by the xanthan solutions, which go from tens to hundreds of s−1.
Single-Phase Flow of Non-Newtonian Fluids in Porous Media
Sochi, Taha
2009-01-01
The study of flow of non-Newtonian fluids in porous media is very important and serves a wide variety of practical applications in processes such as enhanced oil recovery from underground reservoirs, filtration of polymer solutions and soil remediation through the removal of liquid pollutants. These fluids occur in diverse natural and synthetic forms and can be regarded as the rule rather than the exception. They show very complex strain and time dependent behavior and may have initial yield-stress. Their common feature is that they do not obey the simple Newtonian relation of proportionality between stress and rate of deformation. Non-Newtonian fluids are generally classified into three main categories: time-independent whose strain rate solely depends on the instantaneous stress, time-dependent whose strain rate is a function of both magnitude and duration of the applied stress and viscoelastic which shows partial elastic recovery on removal of the deforming stress and usually demonstrates both time and str...
Experimental Investigation and Pore-Scale Modeling of Non-Newtonian Fluid Flow in Porous Media
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.
Gas holdup in a reciprocating plate bioreactor: Non-Newtonian - liquid phase
Directory of Open Access Journals (Sweden)
Naseva Olivera S.
2002-01-01
Full Text Available The gas holdup was studied in non-newtonian liquids in a gas-liquid and gas-liquid-solid reciprocating plate bioreactor. Aqueous solutions of carboxy methyl cellulose (CMC; Lucel, Lučane, Yugoslavia of different degrees of polymerization (PP 200 and PP 1000 and concentration (0,5 and 1%, polypropylene spheres (diameter 8.3 mm; fraction of spheres: 3.8 and 6.6% by volume and air were used as the liquid, solid and gas phase. The gas holdup was found to be dependent on the vibration rate, the superficial gas velocity, volume fraction of solid particles and Theological properties of the liquid ohase. Both in the gas-liquid and gas-liquid-solid systems studied, the gas holdup increased with increasing vibration rate and gas flow rate. The gas holdup was higher in three-phase systems than in two-phase ones under otter operating conditions being the same. Generally the gas holdup increased with increasing the volume fraction of solid particles, due to the dispersion action of the solid particles, and decreased with increasing non-Newtonian behaviour (decreasing flow index i.e. with increasing degree of polymerization and solution concentration of CMC applied, as a result of gas bubble coalescence.
Non-Newtonian steady shear flow characteristics of waxy crude oil
Institute of Scientific and Technical Information of China (English)
黄树新; 陈鑫; 鲁传敬; 侯磊; 范毓润
2008-01-01
The experimental research on the non-Newtonian flow characteristic of a waxy crude oil was conducted through a rotational parallel-plates rheometer system.The test temperature is about 6.5 ℃ higher than its gel point.The shear stress and viscosity of the waxy crude oil show sophisticate non-Newtonian characteristics in the shear rate of 10-4-102 s-1,in which the shear stress can be divided into three parts qualitatively,i.e.stress-up region,leveling-off region,and stress-up region.This indicates that there is a yielding process in shearing for the waxy crude oil at the experimental temperature,which is similar to the yield phenomenon in thixotropy-loop test discussed by CHANG and BOGER.Furthermore,the steady shear experiment after the pre-shear process shows that the stress leveling-off region at low shear rate disappears for the waxy crude oil and the stress curve becomes a monotonic climbing one,which demonstrates that the internal structure property presenting through yielding stress at low shear rate can be changed by shearing.The experimental results also show that the internal structure of waxy crude oil presenting at low shear rate has no influence on the shear viscosity obtained at the shear rate higher than 0.1 s-1.The generalized Newtonian model is adopted to describe the shear-thinning viscosity property of the waxy crude oil at high shear rate.
Non-Newtonian fluid model incorporated into elastohydrodynamic lubrication of rectangular contacts
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.
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.
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.
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.
Experimental study on the special shear thinning process of a kind of non-Newtonian fluid
Institute of Scientific and Technical Information of China (English)
CHEN HaoSheng; CHEN DaRong; WANG JiaDao; LI YongJian
2007-01-01
To study the effect of long chain molecule and surface active agent on non-Newtonian fluid properties, rheological experiments on two different fluids have been done. The first group of the fluid is the hydroxyethyl cellulose water solution, and the second is the water solution containing the mixture of dodecyltriethyl ammonium bromide and lauryl sodium sulfate. With the increasing shear rate, shear thinning phenomenon appears in the first group of solution, and a special shear thickening-shear thinning phenomenon appears in the second group. It is considered that the special rheological phenomenon is caused by the difference between the aggregating and the departing speed of the colloidal particles formed in the fluid. The difference between the two speeds relates with the shear rate. The experiment results indicate that the rheological properties can be designed by choosing proper additives at a certain shear rate, and such a fluid with special viscosity variation should be included in the classification of the non-Newtonian fluid.
Pressure falloff behavior in vertically fractured wells: Non-Newtonian power-law fluids
Energy Technology Data Exchange (ETDEWEB)
Vongvuthipornchai, S.; Raghauan, R.; Reynolds, A.C.
1984-09-01
This paper examines pressure falloff behavior in fractured wells following the injection of a non-Newtonian power-law fluid. Results are presented in a form suitable for field application. Responses at wells intercepting infinite-conductivity and uniformflux fractures are considered. Procedures to identify flow regimes are discussed. The solutions presented here are new and to our knowledge not available in the literature. The consequences of neglecting the non-Newtonian characteristics of the injected fluid are examined. The results of this work were obtained by a finite difference model. Procedures to compute the apparent viscosity of power-law fluids for twodimensional flow through porous media are discussed. The formulation given here avoids numerical problems (multiple solutions, cross over, etc.) reported in other studies. Although, the main objective of the work is to examine pressure falloff behavior at fractured wells, the authors also examine responses at unfractured wells. The main objective of this part of a study is to examine the validity of using the superposition principle to analyze pressure falloff data. (The pressure distribution for this problem is governed by a nonlinear partial differential equation.) If the solutions given in the literature are used, then correction factors are needed to analyze pressure falloff data. The results of this phase of the work can also be used to analyze data in fractured wells provided that pseudoradial flow conditions exist.
The Future of Aerospace Propulsion: Visco-elastic non-Newtonian liquids
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Nicole Arockiam
2011-01-01
Full Text Available Aerospace propulsion often involves the spray and combustion of liquids. When a liquid is sprayed, large drops form first, in a process known as primary atomization. Then, each drop breaks up into smaller droplets, in a process known as secondary atomization. This determines final drop sizes, which affect the liquid’s evaporation and mixing rates and ultimately influence combustor efficiency. Little has been published concerning the secondary atomization of visco-elastic non-Newtonian liquids, such as gels. These substances have special potential as aerospace propellants, because they are safer to handle than their Newtonian liquid counterparts, such as water. Additionally, they can be injected at varying rates, allowing for more control than solid propellants. To learn more about the atomization process of these liquids, a liquid drop generator and a high-speed camera were used to create and measure the conditions at which different breakup modes occurred, as well as the time required for the process. These results were compared to experimental and theoretical results for Newtonian liquids. Based on the data, one can conclude that solutions that are more elastic require higher shear forces to break up. In addition, while Newtonian liquids form droplets as they atomize, visco-elastic non-Newtonian solutions form ligaments. As a result, a combustion system utilizing these types of propellants must be capable of generating these forces. It may also be necessary to find a way to transform the ligaments into more spherically-shaped droplets to increase combustion efficiency.
Non-Newtonian flow of an ultralow-melting chalcogenide liquid in strongly confined geometry
Energy Technology Data Exchange (ETDEWEB)
Wang, Siyuan; Jain, Chhavi; Wondraczek, Katrin; Kobelke, Jens [Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena (Germany); Wondraczek, Lothar [Otto Schott Institute of Material Research (OSIM), Friedrich Schiller University Jena, Fraunhoferstr. 6, 07743 Jena (Germany); Troles, Johann; Caillaud, Celine [Université de Rennes I, Equipe Verres et Céramiques, UMR 6226 Sciences Chimiques de Rennes, Campus de Beaulieu, 35042 Rennes (France); Schmidt, Markus A., E-mail: markus.schmidt@ipht-jena.de [Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena (Germany); Otto Schott Institute of Material Research (OSIM), Friedrich Schiller University Jena, Fraunhoferstr. 6, 07743 Jena (Germany)
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.
Experiments on densely-loaded non-Newtonian slurries in laminar and turbulent pipe flows
Park, Joel T.; Mannheimer, Richard J.; Grimley, Terrence A.; Morrow, Thomas B.
1989-06-01
An experimental description of the flow structure of non-Newtonian slurries in the laminar, transitional, and fully-developed turbulent pipe flow regimes was the primary objective of this research. Experiments were conducted in a large-scale pipe slurry flow facility with an inside diameter of 51 mm (2 inches). Approximately, 550 liters (145 gal) of slurry were necessary in the operation of the loop. Detailed velocity profile measurements by a two-color, two-component laser Doppler anemometer (LDA) were accomplished in a transparent test section with an optically transparent slurry. These velocity measurements were apparently the first ever reported for a non-Newtonian slurry with a yield value. The transparent slurry was formulated for these experiments from silica with a particle size of one to two microns, mineral oil, and Stoddard solvent. From linear regression analysis of concentric-cylinder viscometer data, the slurry exhibited yield-power-law behavior with a yield stress of 100 dynes/cm(sup 2), and an exponent of 0.630 for a solids concentration of 5.65 percent by weight. Good agreement was attained with rheological data derived from the pressure drop data in the flow loop under laminar flow conditions. The rheological properties of the transparent slurry were similar to many industrial slurries, including coal slurries, which have a yield value.
Directory of Open Access Journals (Sweden)
Roozbeh Mollaabbasi
2016-01-01
Full Text Available This research deals with experimental work on solid suspension and dispersion in stirred tank reactors that operate with complex fluids. Only suspended speed (Njs throughout the vessel was characterized using Gamma-Ray Densitometry. The outcomes of this study help to understand solid suspension mechanisms involving changes the rheology of the fluid and provide engineering data for designing stirred tanks. All experiments were based on classic radial and axial flow impellers, i.e., Rushton Turbine (RT and Pitched Blade Turbine in down pumping mode (PBT-D. Three different liquids (water, water+CMC, and water+PAA were employed in several concentrations. The CMC solution introduced as a pseudo plastic fluid and PAA solution was applied as a Herschel Bulkley fluid. The rheological properties of these fluids were characterized separately. According to the findings, the critical impeller speeds for solid suspension for non-Newtonian fluids were more eminent than those for water. Experiments were performed to characterize the effects of solid loading, impeller clearance and viscosity on Njs. Also the PSO method is employed to find suitable parameters of Zwietering's correlation for prediction of Njs in Non Newtonian fluids.
Experimental study on the special shear thinning process of a kind of non-Newtonian fluid
Institute of Scientific and Technical Information of China (English)
2007-01-01
To study the effect of long chain molecule and surface active agent on non-Newtonian fluid properties, rheological experiments on two different fluids have been done. The first group of the fluid is the hydroxyethyl cellulose water solution, and the second is the water solution containing the mixture of dodecyl- triethyl ammonium bromide and lauryl sodium sulfate. With the increasing shear rate, shear thinning phenomenon appears in the first group of solution, and a spe- cial shear thickening-shear thinning phenomenon appears in the second group. It is considered that the special rheological phenomenon is caused by the difference between the aggregating and the departing speed of the colloidal particles formed in the fluid. The difference between the two speeds relates with the shear rate. The experiment results indicate that the rheological properties can be designed by choosing proper additives at a certain shear rate, and such a fluid with special vis- cosity variation should be included in the classification of the non-Newtonian fluid.
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.
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
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.
Directory of Open Access Journals (Sweden)
Kishore P.M.
2012-01-01
Full Text Available This investigation is undertaken to study the hydromagnetic flow of a viscous incompressible fluid past an oscillating vertical plate embedded in a porous medium with radiation, viscous dissipation and variable heat and mass diffusion. Governing equations are solved by unconditionally stable explicit finite difference method of DuFort - Frankel’s type for concentration, temperature, vertical velocity field and skin - friction and they are presented graphically for different values of physical parameters involved. It is observed that plate oscillation, variable mass diffusion, radiation, viscous dissipation and porous medium affect the flow pattern significantly.
Gas hold-up in highly viscous pseudoplastic non-Newtonian solutions in three phase sparged reactors
Energy Technology Data Exchange (ETDEWEB)
Dharwadkar, S.V.; Sawant, S.B.; Joshi, J.B.
1987-06-01
Gas hold-up structure was studied in a three phase sparged reactor of 200 mm diameter. Air and aqueous solutions of carboxymethyl cellulose were used as gas and liquid phases. Spherical glass beads formed the solid phase. The superficial gas velocity, rheological properties, particle size and solid loading were varied over a wide range and their effects on gas hold-up structure were studied. A correlation for the estimation of the gas hold-up as a function of superficial gas velocity, apparent liquid viscosity, particle settling velocity and solid loading was established. 26 refs., 6 figs., 2 tabs.
Dynamical behaviour of non newtonian spiral blood flow through arterial stenosis
Ali, Mohammad; Mahmudul Hasan, Md.; Alam Maruf, Mahbub
2017-04-01
The spiral component of blood flow has both beneficial and detrimental effects in human circulatory system. A numerical investigation is carried out to analyze the effects of spiral blood flow through an axisymmetric three dimensional artery having 75% stenosis at the center. Blood is assumed as a non-Newtonian fluid. Standard k-ω model is used for the simulation with the Reynolds number of 1000. A parabolic velocity profile with spiral flow is used as inlet boundary condition. The peak values of all velocity components are found just after stenosis. But total pressure gradually decreases at downstream. Spiral flow of blood has significant effects on tangential component of velocity. However, the effect is mild for radial and axial velocity components. The peak value of wall shear stress is at the stenosis zone and decreases rapidly in downstream. The effect of spiral flow is significant for turbulent kinetic energy. Detailed investigation and relevant pathological issues are delineated throughout the paper.
Rheological non-Newtonian behaviour of ethylene glycol-based Fe2O3 nanofluids
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Pastoriza-Gallego María
2011-01-01
Full Text Available Abstract 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.
Viscosity bio reducer Influence in a non-Newtonian fluid horizontal pipeline pressure gradient
Directory of Open Access Journals (Sweden)
Edgardo Jonathan Suarez-Dominguez
2014-03-01
Full Text Available Due to increased production of heavy and extra heavy crude in Mexico, it has led to the necessity touse chemicals to facilitate the transport in the pipe of our country. Experimental study was conductedto analyze the influence of a viscosity reducer of biological origin (BRV, on the rheological behaviorof heavy oil in the northern region of Mexico, finding that it exhibits a non-Newtonian viscoelasticbehavior, where a concentration increase of BRV leads to a consistency decrease and an increasedflow order, where dilatant behavior was observed in high temperatures. From these results it wasestimated the pressure losses by friction in a horizontal pipe for single phase and two phase flow. Wefound that in all cases the increase in the concentration of BRV reduces these losses.
Magnetohydrodynamic third-grade non-Newtonian nanofluid flow through a porous coaxial cylinder
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.
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.
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.
Mathematical simulation of nonisothermal filling of plane channel with non-Newtonian fluid
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.
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.
Similarity solutions for non-Newtonian power-law fluid flow
Institute of Scientific and Technical Information of China (English)
D.M.WEI; S.AL-ASHHAB
2014-01-01
The problem of the boundary layer flow of power law non-Newtonian fluids with a novel boundary condition is studied. The existence and uniqueness of the solutions are examined, which are found to depend on the curvature of the solutions for different values of the power law index n. It is established with the aid of the Picard-Lindel¨of theorem that the nonlinear boundary value problem has a unique solution in the global domain for all values of the power law index n but with certain conditions on the curva-ture of the solutions. This is done after a suitable transformation of the dependent and independent variables. For 0 1, the solution has a negative or zero curvature on some part of the global domain. Some solutions are presented graphically to illustrate the results and the behaviors of the solutions.
Generalized multiscale finite element method for non-Newtonian fluid flow in perforated domain
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.
A numerical solution for the entrance region of non-newtonian flow in annuli
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Maia M.C.A.
2003-01-01
Full Text Available Continuity and momentum equations applied to the entrance region of an axial, incompressible, isothermal, laminar and steady flow of a power-law fluid in a concentric annulus, were solved by a finite difference implicit method. The Newtonian case was solved used for validation of the method and then compared to reported results. For the non-Newtonian case a pseudoplastic power-law model was assumed and the equations were transformed to obtain a pseudo-Newtonian system which enabled its solution using the same technique as that used for the Newtonian case. Comparison of the results for entrance length and pressure drop with those available in the literature showed a qualitative similarity, but significant quantitative differences. This can be attributed to the differences in entrance geometries and the definition of asymptotic entrance length.
Exact Solutions for Stokes' Flow of a Non-Newtonian Nanofluid Model: A Lie Similarity Approach
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.
The Non-Newtonian Rheology of Real Magmas: insights into 3D microstructures
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
Geometry of elastic hydrofracturing by injection of an over pressured non-Newtonian Fluid
Cerca, Mariano; Barrientos, Bernardino; Soto, Enrique; Mares, Carlos
2009-01-01
The nucleation and propagation of hydrofractures by injection of over pressured fluids in an elastic and isotropic medium are studied experimentally. Non-Newtonian fluids are injected inside a gelatine whose mechanical properties are assumed isotropic at the experimental strain rates. Linear elastic theory predicts that plastic deformation associated to breakage of gelatin bonds is limited to a small zone ahead of the tip of the propagating fracture and that propagation will be maintained while the fluid pressure exceeds the normal stress to the fracture walls (Ch\\'avez-\\'Alvarez,2008) (i.e., the minimum compressive stress), resulting in a single mode I fracture geometry. However, we observed the propagation of fractures type II and III as well as nucleation of secondary fractures, with oblique to perpendicular trajectories with respect to the initial fracture. In the Video (http://hdl.handle.net/1813/14122) experimental evidence shows that the fracture shape depends on the viscoelastic properties of gelatine...
Non-newtonian flow and pressure drop of pineapple juice in a plate heat exchanger
Directory of Open Access Journals (Sweden)
R. A. F. Cabral
2010-12-01
Full Text Available The study of non-Newtonian flow in plate heat exchangers (PHEs is of great importance for the food industry. The objective of this work was to study the pressure drop of pineapple juice in a PHE with 50º chevron plates. Density and flow properties of pineapple juice were determined and correlated with temperature (17.4 < T < 85.8ºC and soluble solids content (11.0 < Xs < 52.4 ºBrix. The Ostwald-de Waele (power law model described well the rheological behavior. The friction factor for non-isothermal flow of pineapple juice in the PHE was obtained for diagonal and parallel/side flow. Experimental results were well correlated with the generalized Reynolds number (20 < Re g < 1230 and were compared with predictions from equations from the literature. The mean absolute error for pressure drop prediction was 4% for the diagonal plate and 10% for the parallel plate.
ON THE FILTRATION OF NON-NEWTONIAN FLUID IN POROUS MEDIA WITH A MULTIPLE PARAMETER MODEL
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A multiple parameter model to describe the Non-Newtonianproperties of fluid filtration in porous media is presented with regard to the pressure gradient expression in terms of the velocity of filtration, where the multiple parameters should be determined by measurements. Based on such a model, an analysis was furnished to deduce the formula for the rate of production of a oil well, and the governing equations for single phase Non-Newtonian fluid fritration. In order to examine the effects of model parameters, the governing equations were numerically solved with the method of cross-diagonal decomposition ZG method. It is found that, for constant rate of production, the power index n of the model influences the pressure distribution considerably, particularly in the vicinity of a single well. The well-bore pressure of Leibenzonian fluid is lower than that of the power-law fluid in the case of the same parameter B and the power index n = 0.5.
Free surface flow of a suspension of rigid particles in a non-Newtonian fluid
DEFF Research Database (Denmark)
Svec, Oldrich; Skocek, Jan; Stang, Henrik
2012-01-01
efficient, allowing simulations of tens of thousands of rigid particles within a reasonable computational time. Furthermore, the framework does not require any fitting constants or parameters devoid of a clear physical meaning and it is stable, robust and can be easily generalized to a variety of problems......A numerical framework capable of predicting the free surface flow of a suspension of rigid particles in a non-Newtonian fluid is described. The framework is a combination of the lattice Boltzmann method for fluid flow, the mass tracking algorithm for free surface representation, the immersed...... boundary method for two-way coupled interactions between fluid and rigid particles and an algorithm for the dynamics and mutual interactions of rigid particles. The framework is able to simulate the flow of suspensions at the level of the largest suspended particles and, at the same time, the model is very...
Modeling of flow of particles in a non-Newtonian fluid using lattice Boltzmann method
DEFF Research Database (Denmark)
Skocek, Jan; Svec, Oldrich; Spangenberg, Jon
2011-01-01
To predict correctly the castings process of self compacting concrete a numerical model capable of simulating flow patterns at the structural scale and at the same time the impact of the varying volume fraction of aggregates and other phenomena at the scale of aggregates on the flow evolution...... is necessary. In this contribution, the model at the scale of aggregates is introduced. The conventional lattice Boltzmann method for fluid flow is enriched with the immersed boundary method with direct forcing to simulate the flow of rigid particles in a non- Newtonian liquid. Basic ingredients of the model...... are presented and discussed with the emphasis on a newly developed algorithm for the dynamics of particles whose interactions strongly depend on velocities of particles. The application of the model is demonstrated by a parametric study with varying volume fractions of aggregates and speed of shearing used...
Numerical simulation of pulsatile non-Newtonian flow in the carotid artery bifurcation
Fan, Yubo; Jiang, Wentao; Zou, Yuanwen; Li, Jinchuan; Chen, Junkai; Deng, Xiaoyan
2009-04-01
Both clinical and post mortem studies indicate that, in humans, the carotid sinus of the carotid artery bifurcation is one of the favored sites for the genesis and development of atherosclerotic lesions. Hemodynamic factors have been suggested to be important in atherogenesis. To understand the correlation between atherogenesis and fluid dynamics in the carotid sinus, the blood flow in artery was simulated numerically. In those studies, the property of blood was treated as an incompressible, Newtonian fluid. In fact, however, the blood is a complicated non-Newtonian fluid with shear thinning and viscoelastic properties, especially when the shear rate is low. A variety of non-Newtonian models have been applied in the numerical studies. Among them, the Casson equation was widely used. However, the Casson equation agrees well only when the shear rate is less than 10 s-1. The flow field of the carotid bifurcation usually covers a wide range of shear rate. We therefore believe that it may not be sufficient to describe the property of blood only using the Casson equation in the whole flow field of the carotid bifurcation. In the present study, three different blood constitutive models, namely, the Newtonian, the Casson and the hybrid fluid constitutive models were used in the flow simulation of the human carotid bifurcation. The results were compared among the three models. The results showed that the Newtonian model and the hybrid model had very similar distributions of the axial velocity, secondary flow and wall shear stress, but the Casson model resulted in significant differences in these distributions from the other two models. This study suggests that it is not appropriate to only use the Casson equation to simulate the whole flow field of the carotid bifurcation, and on the other hand, Newtonian fluid is a good approximation to blood for flow simulations in the carotid artery bifurcation.
Numerical simulation of pulsatile non-Newtonian flow in the carotid artery bifurcation
Institute of Scientific and Technical Information of China (English)
Yubo Fan; Wentao Jiang; Yuanwen Zou; Jinchuan Li; Junkai Chen; Xiaoyan Deng
2009-01-01
Both clinical and post mortem studies indicate that, in humans, the carotid sinus of the carotid artery bifurcation is one of the favored sites for the genesis and development of atherosclerotic lesions. Hemodynamic factors have been suggested to be important in atherogenesis. To understand the correlation between atherogenesis and fluid dynamics in the carotid sinus, the blood flow in artery was simulated numerically. In those studies, the property of blood was treated as an incompressible, Newtonian fluid. In fact,however, the blood is a complicated non-Newtonian fluid with shear thinning and viscoelastic properties, especially when the shear rate is low. A variety of non-Newtonian models have been applied in the numerical studies. Among them,the Casson equation was widely used. However, the Casson equation agrees well only when the shear rate is less than 10s-1. The flow field of the carotid bifurcation usually covers a wide range of shear rate. We therefore believe that it may not be sufficient to describe the property of blood only using the Casson equation in the whole flow field of the carotid bifurcation. In the present study, three different blood constitutive models, namely, the Newtonian, the Casson and the hybrid fluid constitutive models were used in the flow simulation of the human carotid bifurcation. The results were compared among the three models. The results showed that the Newtonian model and the hybrid model had very similar distributions of the axial velocity, secondary flow and wall shear stress, but the Casson model resulted in significant differences in these distributions from the other two models. This study suggests that it is not appropriate to only use the Casson equation to simulate the whole flow field of the carotid bifurcation, and on the other hand, Newtonian fluid is a good approximation to blood for flow simulations in the carotid artery bifurcation.
Break-up of a non-Newtonian jet injected downwards in a Newtonian liquid
Indian Academy of Sciences (India)
Absar M Lakdawala; Rochish Thaokar; Atul Sharma
2015-05-01
The present work on downward injection of non-Newtonian jet is an extension of our recent work (Lakdawala et al, Int. J. Multiphase Flow. 59: 206–220, 2014) on upward injection of Newtonian jet. The non-Newtonian rheology of the jet is described by a Carreau type generalized Newtonian fluid (GNF) model, which is a phenomenological constitutive equation that accounts for both rate-thinning and rate-thickening. Level set method based numerical study is done for Newtonian as well as various types of shear thinning and thickening jet fluid. Effect of average injection velocity ($V_{av,i}$) is studied at a constant Reynolds number Re = 14.15, Weber number W e = 1, Froude number F r = 0.25, density ratio $\\chi$ = 0.001 and viscosity ratio $\\eta$ = 0.01. CFD analysis of the temporal variation of interface and jet length ($L_{j}$) is done to propose different types of jet breakup regimes. At smaller, intermediate and larger values of $V_{av,i}$, the regimes found are periodic uniform drop (P-UD), quasi-periodic non-uniform drop (QP-NUD) and no breakup (NB) regimes for a shear thinning jet; and periodic along with Satellite Drop (P+S), jetting (J) and no breakup (NB) regimes for a shear thickening jet, respectively. This is presented as a drop-formation regime map. Shear thickening (thinning) is shown to produce long (short) jet length. Diameter of the primary drop increases and its frequency of release decreases, due to increase in stability of the jet for shear thickening as compared to thinning fluid.
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.
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
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.
Energy Technology Data Exchange (ETDEWEB)
Lipscombe, T C [Johns Hopkins University, 2715 North Charles Street, Baltimore, MD 21218 (United States)], E-mail: tcl@press.jhu.edu
2010-03-15
We solve exactly the Poiseuille and Couette flows of a non-Newtonian fluid discussed by Roohi et al (2009 Phys. Scr. 79 065009) and thereby show that the approximate analytical solutions provided by the homotopy method must be used with caution.
Boundary layer flow on a moving surface in otherwise quiescent pseudo-plastic non-Newtonian fluids
Institute of Scientific and Technical Information of China (English)
Liancun Zheng; Liu Ting; Xinxin Zhang
2008-01-01
A theoretical analysis for the boundary layer flow over a continuous moving surface in an otherwise quiescent pseudo-plastic non-Newtonian fluid medium was presented. The types of potential flows necessary for similar solutions to the boundary layer equations were determined and the solutions were numerically presented for different values of power law exponent.
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.
Azma, Sahra; Rezazadeh, Ghader; Shabani, Rasoul; Alizadeh-Haghighi, Elnaz
2016-06-01
Viscous damping is a dominant source of energy dissipation in laterally oscillating micro-structures. In micro-resonators in which the characteristic dimensions are comparable to the dimensions of the fluid molecules, the assumption of the continuum fluid theory is no longer justified and the use of micro-polar fluid theory is indispensable. In this paper a mathematical model was presented in order to predict the viscous fluid damping in a laterally oscillating finger of a micro-resonator considering micro-polar fluid theory. The coupled governing partial differential equations of motion for the vibration of the finger and the micro-polar fluid field have been derived. Considering spin and no-spin boundary conditions, the related shape functions for the fluid field were presented. The obtained governing differential equations with time varying boundary conditions have been transformed to an enhanced form with homogenous boundary conditions and have been discretized using a Galerkin-based reduced order model. The effects of physical properties of the micro-polar fluid and geometrical parameters of the oscillating structure on the damping ratio of the system have been investigated.
Institute of Scientific and Technical Information of China (English)
Sahra Azma; Ghader Rezazadeh; Rasoul Shabani; Elnaz Alizadeh-Haghighi
2016-01-01
Viscous damping is a dominant source of energy dissipation in laterally oscillating micro-structures. In micro-resonators in which the characteristic dimensions are compa-rable to the dimensions of the fluid molecules, the assumption of the continuum fluid theory is no longer justified and the use of micro-polar fluid theory is indispensable. In this paper a mathematical model was presented in order to predict the viscous fluid damping in a laterally oscillating finger of a micro-resonator considering micro-polar fluid theory. The coupled governing partial differential equations of motion for the vibration of the finger and the micro-polar fluid field have been derived. Considering spin and no-spin boundary conditions, the related shape functions for the fluid field were presented. The obtained governing differential equations with time varying boundary conditions have been trans-formed to an enhanced form with homogenous boundary conditions and have been discretized using a Galerkin-based reduced order model. The effects of physical properties of the micro-polar fluid and geometrical parameters of the oscillat-ing structure on the damping ratio of the system have been investigated.
DEFF Research Database (Denmark)
Jabbaribehnam, Mirmasoud; Spangenberg, Jon; Hattel, Jesper Henri
2016-01-01
In this paper, the migration of secondary particles in a non-Newtonian ceramic slurry inthe tape casting process is investigated with the purpose of understanding the particle distribution patterns along the casting direction. The Ostwald-de Waele power law model for the non-Newtonian flow...
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.
Directory of Open Access Journals (Sweden)
M. Umamaheswar
2016-09-01
Full Text Available A numerical investigation is carried out on an unsteady MHD free convection flow of a well-known non-Newtonian visco elastic second order Rivlin-Erickson fluid past an impulsively started semi-infinite vertical plate in the presence of homogeneous chemical reaction, thermal radiation, thermal diffusion, radiation absorption and heat absorption with constant mass flux. The presence of viscous dissipation is also considered at the plate under the influence of uniform transverse magnetic field. The flow is governed by a coupled nonlinear system of partial differential equations which are solved numerically by using finite difference method. The effects of various physical parameters on the flow quantities viz. velocity, temperature, concentration, Skin friction, Nusselt number and Sherwood number are studied numerically. The results are discussed with the help of graphs. We observed that the velocity decreases with an increase in magnetic field parameter, Schmidt number, and Prandtl number while it increases with an increase in Grashof number, modified Grashof number, visco-elastic parameter and Soret number. Temperature increases with an increase in radiation absorption parameter, Eckert number and visco-elastic parameter while it decreases with increasing values of radiation parameter, Prandtl number and heat absorption parameter. Concentration increases with increase in Soret number while it decreases with an increase in Schmidt number and chemical reaction parameter.
Nuriev, A. N.; Zakharova, O. S.; Zaitseva, O. N.; Yunusova, A. I.
2016-11-01
A rectilinear motion of a two-mass system in a viscous incompressible fluid is considered. The system consists of a shell having the form of an equilateral triangular cylinder and a movable internal mass. The motion of the system as a whole is forced by longitudinal oscillations of the internal mass relative to the shell. This mechanical system simulates a vibration-driven robot, i.e. a mobile device capable to move in a resistive medium without external moving parts. Investigation of the system is carried out by a direct numerical simulation. A comparative analysis of the characteristics of the motion and flow regimes around the vibration-driven robot is carried out for different internal mass oscillation laws.
Experimental investigation of non-Newtonian/Newtonian liquid-liquid flow in microchannel
Roumpea, Eynagelia-Panagiota; Weheliye, Weheliye; Chinaud, Maxime; Angeli, Panagiota; Lyes Kahouadji Collaboration; Omar. K. Matar Collaboration
2015-11-01
Plug flow of an organic phase and an aqueous non-Newtonian solution was investigated experimentally in a quartz microchannel with I.D. 200 μm. The aqueous phase was a glycerol solution where 1000 and 2000 ppm of xanthan gum was added while the organic phase was silicon oil with 155 and 5 cSt viscosity. The two phases were brought together in a T-junction and their flowrates varied from 0.3 to 6 ml/hr. High speed imaging was used to study the characteristics of the plugs and the effect of the liquid properties on the flow patterns while a two-colour micro-PIV technique was used to investigate velocity profiles and circulation patterns within the plugs. The experimental results revealed that plug length was affected by both flowrate and viscosity. In all cases investigated, a film of the continuous phase always surrounded the plugs and its thickness was compared with existing literature models. Circulation patterns inside plugs were obtained by subtracting the plug velocity and found to be depended on the plug length and the amount of xanthan gum in the aqueous phase. Finally, the dimensionless circulation time was calculated and plotted as a function of the plug length. Department of Chemical Engineering South Kensington Campus Imperial College London SW7 2AZ.
Entropy Generation in Flow of Highly Concentrated Non-Newtonian Emulsions in Smooth Tubes
Directory of Open Access Journals (Sweden)
Rajinder Pal
2014-10-01
Full Text Available Entropy generation in adiabatic flow of highly concentrated non-Newtonian emulsions in smooth tubes of five different diameters (7.15–26.54 mm was investigated experimentally. The emulsions were of oil-in-water type with dispersed-phase concentration (Φ ranging from 59.61–72.21% vol. The emulsions exhibited shear-thinning behavior in that the viscosity decreased with the increase in shear rate. The shear-stress (τ versus shear rate (˙γ data of emulsions could be described well by the power-law model: τ=K˙γn. The flow behavior index n was less than 1 and it decreased sharply with the increase in Φ whereas the consistency index K increased rapidly with the increase in Φ . For a given emulsion and tube diameter, the entropy generation rate per unit tube length increased linearly with the increase in the generalized Reynolds number ( Re_n on a log-log scale. For emulsions with Φ ≤65.15 % vol., the entropy generation rate decreased with the increase in tube diameter. A reverse trend in diameter-dependence was observed for the emulsion with Φ of 72.21% vol. New models are developed for the prediction of entropy generation rate in flow of power-law emulsions in smooth tubes. The experimental data shows good agreement with the proposed models.
Influence of Droplet Size on Exergy Destruction in Flow of Concentrated Non-Newtonian Emulsions
Directory of Open Access Journals (Sweden)
Rajinder Pal
2016-04-01
Full Text Available The influence of droplet size on exergy destruction rate in flow of highly concentrated oil-in-water emulsions was investigated experimentally in a cone and plate geometry. The oil concentration was fixed at 74.5% by volume. At this dispersed-phase (oil concentration, two different droplet size emulsions were prepared: fine and coarse emulsions. The fine and coarse emulsions were mixed in different proportions to vary the droplet size distribution. Although the dispersed and matrix phases of the emulsions were Newtonian in nature, the emulsions exhibited a non-Newtonian (shear-thinning behavior due to the high droplet concentration. The shear stress—shear rate data of the emulsions could be described adequately by a power law model. At low shear rates, the exergy destruction rate per unit volume of emulsion exhibited a minimum at a fine emulsion proportion of 35%. The results from the cone and plate geometry were used to simulate exergy loss in pipeline flow of emulsions. The pumping of emulsions becomes more efficient thermodynamically upon mixing of fine and coarse emulsions provided that the flow regime is maintained to be laminar and that the Reynolds number is kept at a low to moderate value. In the turbulent regime, the exergy loss generally increases upon mixing the fine and coarse emulsions.
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.
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.
Directory of Open Access Journals (Sweden)
Yonghui Xie
2015-01-01
Full Text Available Flow characteristics and heat transfer performances in rectangular tubes with protrusions are numerically investigated in this paper. The thermal heat transfer enhancement of composite structures and flow resistance reduction of non-Newtonian fluid are taken advantage of to obtain a better thermal performance. Protrusion channels coupled with different CMC concentration solutions are studied, and the results are compared with that of smooth channels with water flow. The comprehensive influence of turbulence effects, structural effects, and secondary flow effects on the CMC’s flow in protrusion tubes is extensively investigated. The results indicate that the variation of flow resistance parameters of shear-thinning power-law fluid often shows a nonmonotonic trend, which is different from that of water. It can be concluded that protrusion structure can effectively enhance the heat transfer of CMC solution with low pressure penalty in specific cases. Moreover, for a specific protrusion structure and a fixed flow velocity, there exists an optimal solution concentration showing the best thermal performance.
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.
Study on Flow Characteristic of Non-Newtonian fluid in Eccentric Annulus
Directory of Open Access Journals (Sweden)
Li Mingzhong
2013-08-01
Full Text Available This study studied the flow characteristic of non-newtonian in eccentric annulus of highly-deviated well. On the basis of dimensionless analysis of motion equations and continuity equation, Hele-Shaw model suitable for fluid flow in the annulus was derived. Combined with H-B rheological model, velocity and stream distribution model were founded and calculated by numerical method. Furthermore, two-dimensional flow characteristic in eccentric annulus was got and the influence of different factors (such as yield stress, pressure gradient or eccentricity on velocity distribution in condition of laminar flow was analyzed. Width of flow core in the annular is proportional to yield stress and inversely proportional to pressure gradient. In eccentric annulus, eccentricity influences the stream distribution remarkably: with the increment of eccentricity, the contour lines of stream function gradually centralize in the widest annular gap, however distribute the most loosely in the narrowest annular gap. Axial velocity is the largest in the widest gap. The larger eccentricity is, the larger contrast of axial velocity between in the widest gap and in the narrowest gap is. There is the largest azimuthal velocity in an annular gap of a certain azimuthal angle, however which equals to zero in the widest and narrowest annular gap separately. The larger eccentricity is, the more homogeneous azimuthal velocity is. The velocity contrast in the entire annulus can be smoothed by increasing pressure gradient, power law index or decreasing yield stress.
Non-Newtonian fluids: Frictional pressure loss prediction for fully-developed flow in straight pipes
1991-10-01
ESDU 91025 discusses models used to describe the rheology of time independent pseudohomogeneous non-Newtonian fluids (power-law, Bingham, Herschel-Bulkley and a generalized model due to Metzner and Reed); they are used to calculate the laminar flow pressure drop (which is independent of pipe roughness in this regime). Values of a generalized Reynolds number are suggested to define transitional and turbulent flow. For turbulent flow in smooth pipes, pressure loss is estimated on the basis of an experimentally determined rheogram using either the Dodge-Metzner or Bowen approach depending on the available measurements. Bowen requires results for at least two pipe diameters. The choice of Dodge-Metzner when data are limited is discussed; seven possible methods are assessed against five sets of experimental results drawn from the literature. No method is given for transitional flow, which it is suggested should be avoided, but the turbulent correlation is recommended because it will yield an overestimate. Suggestions are made for the treatment of roughness effects. Several worked examples illustrate the use of the methods and a flowchart guides the user through the process from experimentally characterizing the behavior of the fluid to determining the pressure drop. A computer program, ESDUpac A9125, is also provided.
The effect of non-Newtonian viscosity on the stability of the Blasius boundary layer
Griffiths, P. T.; Gallagher, M. T.; Stephen, S. O.
2016-07-01
We consider, for the first time, the stability of the non-Newtonian boundary layer flow over a flat plate. Shear-thinning and shear-thickening flows are modelled using a Carreau constitutive viscosity relationship. The boundary layer equations are solved in a self-similar fashion. A linear asymptotic stability analysis, that concerns the lower-branch structure of the neutral curve, is presented in the limit of large Reynolds number. It is shown that the lower-branch mode is destabilised and stabilised for shear-thinning and shear-thickening fluids, respectively. Favourable agreement is obtained between these asymptotic predictions and numerical results obtained from an equivalent Orr-Sommerfeld type analysis. Our results indicate that an increase in shear-thinning has the effect of significantly reducing the value of the critical Reynolds number, this suggests that the onset of instability will be significantly advanced in this case. This postulation, that shear-thinning destabilises the boundary layer flow, is further supported by our calculations regarding the development of the streamwise eigenfunctions and the relative magnitude of the temporal growth rates.
Directory of Open Access Journals (Sweden)
Jingya Sun
2014-01-01
Full Text Available Dampers are widely applied to protect devices or human body from severe impact or harmful vibration circumstances. Considering that dampers with low velocity exponent have advantages in energy absorption, they have been widely used in antiseismic structures and shock buffering. Non-Newtonian fluid with strong shear-thinning effect is commonly adopted to achieve this goal. To obtain the damping mechanism and find convenient methods to design the nonlinear fluid damper, in this study, a hydraulic damper is filled with 500,000 cSt silicone oil to achieve a low velocity exponent. Drop hammer test is carried out to experimentally obtain its impact and buffering characteristics. Then a coupling model is built to analyze its damping mechanism, which consists of a model of impact system and a computational fluid dynamics (CFD model. Results from the coupling model can be consistent with the experiment results. Simulation method can help design non-Newtonian fluid dampers more effectively.
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.
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.
Institute of Scientific and Technical Information of China (English)
Mizue MUNEKATA; Hidefumi TAKAKI; Hideki OHBA; Kazuyoshi MATSUZAKI
2005-01-01
Effects of non-Newtonian viscosity for surfactant solution on the vortex characteristics and drag-reducing rate in a swirling pipe flow are investigated by pressure drop measurements, velocity profile measurements and viscosity measurements. Non-Newtonian viscosity is represented by power-law model (τ = kD n). Surfactant solution used has shear-thinning viscosity with n ＜ 1.0. The swirling flow in this study has decay of swirl and vortex-type change from Rankin's combined vortex to forced vortex. It is shown that the effect of shear-thinning viscosity on the decay of swirl intensity is different by vortex category and the critical swirl number with the vortex-type change depends on shear-thinning viscosity.
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.
Energy Technology Data Exchange (ETDEWEB)
Lin, Jaw-Ren; Hung, Chi-Ren; Lu, Rong-Fang [Nanya Institute of Technology, Jhongli, Taiwan (China). Dept. of Mechanical Engineering; Chu, Li-Ming [I-Shou Univ., Kaohsiung, Taiwan (China). Dept. of Mechanical and Automation Engineering
2011-08-15
According to the experimental work of C. Barus in Am. J. Sci. 45, 87 (1893), the dependency of liquid viscosity on pressure is exponential. Therefore, we extend the study of squeeze film problems of long partial journal bearings for Stokes non-Newtonian couple stress fluids by considering the pressure-dependent viscosity in the present paper. Through a small perturbation technique, we derive a first-order closed-form solution for the film pressure, the load capacity, and the response time of partial-bearing squeeze films. It is also found that the non-Newtonian couple-stress partial bearings with pressure-dependent viscosity provide better squeeze-film characteristics than those of the bearing with constant-viscosity situation. (orig.)
Lin, Jaw-Ren; Chu, Li-Ming; Hung, Chi-Ren; Lu, Rong-Fang
2011-09-01
According to the experimental work of C. Barus in Am. J. Sci. 45, 87 (1893) [1], the dependency of liquid viscosity on pressure is exponential. Therefore, we extend the study of squeeze film problems of long partial journal bearings for Stokes non-Newtonian couple stress fluids by considering the pressure-dependent viscosity in the present paper. Through a small perturbation technique, we derive a first-order closed-form solution for the film pressure, the load capacity, and the response time of partial-bearing squeeze films. It is also found that the non-Newtonian couple-stress partial bearings with pressure-dependent viscosity provide better squeeze-film characteristics than those of the bearing with constant-viscosity situation.
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.
Institute of Scientific and Technical Information of China (English)
TONG Dengke; WANG Ruihe
2004-01-01
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 function. 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.
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.
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.
The effects of non-Newtonian viscosity on the deformation of red blood cells in a shear flow
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.
Physics of Life: A Model for Non-Newtonian Properties of Living Systems
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
On Laminar Flow of Non-Newtonian Fluids in Porous Media
Fayed, Hassan E.
2015-10-20
Flow of generalized Newtonian fluids in porous media can be modeled as a bundle of capillary tubes or a pore-scale network. In general, both approaches rely on the solution of Hagen–Poiseuille equation using power law to estimate the variations in the fluid viscosity due to the applied shear rate. Despite the effectiveness and simplicity, power law tends to provide unrealistic values for the effective viscosity especially in the limits of zero and infinite shear rates. Here, instead of using power law, Carreau model (bubbles, drops, and particles in non-Newtonian fluids. Taylor & Francis Group, New York, 2007) is used to determine the effective viscosity as a function of the shear strain rate. Carreau model can predict accurately the variation in the viscosity at all shear rates and provide more accurate solution for the flow physics in a single pore. Using the results for a single pore, normalized Fanning friction coefficient has been calculated and plotted as a function of the newly defined Reynolds number based on pressure gradient. For laminar flow, the variation in the friction coefficient with Reynolds number has been plotted and scaled. It is observed that generalized Newtonian fluid flows show Newtonian nature up to a certain Reynolds number. At high Reynolds number, deviation from the Newtonian behavior is observed. The main contribution of this paper is to present a closed-form solution for the flow in a single pore using Carreau model, which allows for fast evaluation of the relationship between flux and pressure gradient in an arbitrary pore diameter. In this way, we believe that our development will open the perspectives for using Carreau models in pore-network simulations at low computational costs to obtain more accurate prediction for generalized Newtonian fluid flows in porous media.
Mounding of a non-Newtonian jet impinging on a solid substrate.
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Schunk, Peter Randall; Grillet, Anne Mary; Roberts, Scott A.; Baer, Thomas A. (Procter & Gamble, Cincinnati, OH); 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
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.
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.
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.
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
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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.
Experimental model for non-Newtonian fluid viscosity estimation: Fit to mathematical expressions
Directory of Open Access Journals (Sweden)
Guillem Masoliver i Marcos
2017-01-01
Full Text Available The construction process of a viscometer, developed in collaboration with a final project student, is here presented. It is intended to be used by first year's students to know the viscosity as a fluid property, for both Newtonian and non-Newtonian flows. Viscosity determination is crucial for the fluids behaviour knowledge related to their reologic and physical properties. These have great implications in engineering aspects such as friction or lubrication. With the present experimental model device three different fluids are analyzed (water, kétchup and a mixture with cornstarch and water. Tangential stress is measured versus velocity in order to characterize all the fluids in different thermal conditions. A mathematical fit process is proposed to be done in order to adjust the results to expected analytical expressions, obtaining good results for these fittings, with R2 greater than 0.88 in any case.
Khurana, Meenakshi; Rana, Puneet; Srivastava, Sangeet
2016-12-01
In the present paper, we present both linear and nonlinear analyses to investigate thermal instability on a rotating non-Newtonian viscoelastic nanofluid layer under the influence of a magnetic field. In the linear stability analysis, the stationary and oscillatory modes of convection are obtained for various controlling parameters using the normal mode technique. Both Nusselt and Sherwood numbers are calculated after employing the minimal truncated Fourier series to steady and unsteady state. The main findings conclude that rotation and strain retardation parameter increase the value of the critical Rayleigh number in the neutral stability curve which delays the onset of convection in the nanofluid layer while the stress relaxation parameter enhances the convection. The magnetic field stabilizes the system for low values of the Taylor number (rotation) but an inverse trend is observed for high Taylor number. Both Nusselt and Sherwood numbers initially oscillate with time until the steady state prevails and they decrease with both Chandrasekhar and Taylor numbers. The magnitude of the streamlines and the contours of both isotherms and iso-nanohalines concentrate near the boundaries for large values of Ra, indicating an increase in convection.
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.
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.
García Pinar, Alberto; Solano Fernández, Juan Pedro; Viedma Robles, Antonio; Martínez Hernández, David Sebastián
2010-01-01
This work presents an experimental study on the heat transfer enhancement by means of a tube with wire-coil insert,for non-Newtonian laminar and transitional flow. The dimensionless pitch and wire diameter (based on the plain tube inner diameter) were chosen as p/D= 1 and e/D=0.09. Two pseudoplastic test fluids have been used: 1% by weight aqueous solutions of carboxymethyl cellulose (CMC) with high viscosity and medium viscosity. A wide range of flow conditions has been covered: Reynolds ...
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.
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.
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.
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
This paper studies mixed convection,double dispersion and chemical reaction effects on heat and mass transfer in a non-Darcy non-Newtonian fluid over a vertical surface in a porous medium under the constant temperature and concentration.The governing boundary layer equations,namely,momentum,energy and concentration,are converted to ordinary differential equations by introducing similarity variables and then are solved numerically by means of fourth-order Runge-Kutta method coupled with double-shooting techn...
SOLUTION OF THE RAYLEIGH PROBLEM FOR A POWER-LAW NON-NEWTONIAN CONDUCTING FLUID VIA GROUP METHOD
Institute of Scientific and Technical Information of China (English)
Mina B.Abd-el-Malek; Nagwa A.Badran; Hossam S.Hassan
2002-01-01
An investigation is made of the magnetic Rayleigh problem where a semi-infinite plate is given an impulsive motion and thereafter moves with constant velocity in a nonNewtonian power law fluid of infinite extent. The solution of this highly non-linear problem is obtained by means of the transformation group theoretic approach. The one-parameter group transformation reduces the number of independent variables by one and the governing partial differential equation with the boundary conditions reduce to an ordinary differential equation with the appropriate boundary conditions. Effect of the some parameters on the velocity u ( y, t) has been studied and the results are plotted.
MHD flow and heat transfer from continuous surface in uniform free stream of non-Newtonian fluid
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
An analysis is carried out to study the steady flow and heat transfer characteristics from a continuous flat surface moving in a parallel free stream of an electrically conducting non-Newtonian viscoelastic fluid. The flow is subjected to a transverse uniform magnetic field. The constitutive equation of the fluid is modeled by that for a second grade fluid. Numerical results are obtained for the distribution of velocity and temperature profiles. The effects of various physical parameters like viscoelastic parameter, magnetic parameter and Prandtl number on various momentum and heat transfer characteristics are discussed in detail and shown graphically.
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.
Data on the mixing of non-Newtonian fluids by a Rushton turbine in a cylindrical tank
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Akhilesh Khapre
2016-09-01
Full Text Available 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.
MHD non-Newtonian micropolar fluid flow and heat transfer in channel with stretching walls
Institute of Scientific and Technical Information of China (English)
M. ASHRAF; N. JAMEEL; K. ALI
2013-01-01
A study is presented for magnetohydrodynamics (MHD) flow and heat trans-fer characteristics of a viscous incompressible electrically conducting micropolar fluid in a channel with stretching walls. The micropolar model introduced by Eringen is used to describe the working fluid. The transformed self similar ordinary differential equations together with the associated boundary conditions are solved numerically by an algorithm based on quasi-linearization and multilevel discretization. The effects of some physical parameters on the flow and heat transfer are discussed and presented through tables and graphs. The present investigations may be beneficial in the flow and thermal control of polymeric processing.
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Broniarz-Press, Lubomira; Rozanska, Sylwia [Department of Chemical Engineering and Equipment, Faculty of Chemical Technology, Poznan University of Technology, pl. M. Sklodowskiej-Curie 2, PL 60-965 Poznan (Poland)
2008-02-15
In the study the results of the friction factor in boundary layer and the distribution of heat transfer coefficient in non-Newtonian liquid agitated by different impellers, have been presented. It has been established that for studies in Na-CMC and guar gum aqueous solutions by the electrochemical method the following solution of 0.005 (kmol m{sup -3}) K{sub 3}[Fe(CN){sub 6}], 0.005 (kmol m{sup -3}) K{sub 4}[Fe(CN){sub 6}] and 0.3 (kmol m{sup -3}) K{sub 2}SO{sub 4} can be recommended. The common relationship (for a given type of an impeller) between local values of friction coefficient and heat transfer coefficient and Reynolds number proposed by Metzner and Otto [A.B. Metzner, R.E. Otto, Agitation of non-Newtonian fluids, AIChe J. 3 (1957) 3-10] for all power-law fluids, have been obtained. (author)
Lin, Weikang; Chen, Lie-Wen; Wen, De-Hua; Xu, Jun
2013-01-01
A thorough understanding of many astrophysical phenomena and objects requires reliable knowledge about both the equation of state (EOS) of super-dense nuclear matter and the theory of ultra-strong gravity simultaneously because of the EOS-gravity degeneracy. Currently, deviations of the neutron star (NS) mass-radius correlation predicted by various gravity theories are larger than its uncertainties due to the poorly known NS matter content and its EOS. At least two independent observables are required to break the EOS-gravity degeneracy. Using model EOSs for hybrid stars and a Yukawa-type non-Newtonian gravity, we investigate both the mass-radius correlation and pulsating frequencies of NSs. While the maximum mass of NSs increases with increasing strength of the Yukawa-type non-Newtonian gravity, the frequencies of the $f$, $p_1$, $p_2$, and $w_I$ pulsating modes are found to decrease with it, providing a useful reference for future determination simultaneously of both the gravitational theory and the supranu...
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.
Institute of Scientific and Technical Information of China (English)
朱春英; 付涛涛; 高习群; 马友光
2011-01-01
On the basis of Navier-Stockes equation and convection-diffusion equation, combined with surface tension and penetration models, the equations of moment and mass transfer between bubble and the ambient non-Newtonian liquid were established. The formation of a single bubble from a submersed nozzle of 1.0 mm diameter and the mass transfer from an artificially fixed bubble into the ambient liquid were simulated by the volume-of-fluid （VOF） method. Good agreement between simulation results and experimental data confirmed the validity of the numerical method. Furthermore, the concentration distribution around rising bubbles in shear thinning non-Newtonian fluid was simulated. When the process of a single ellipsoidal bubble with the bubble deformation rate below 2.0 rises, the concentration distribution is a single-tail in the bubble＇s wake, but it is fractal when thebubble deformation rate is greater than 2.0. For the overtaking of two in-line rising bubbles, the concentration distribution area between two bubbles broadens gradually and then coalescence occurs. The bifurcation of concentration distribution appears in the rear of the resultant bubble.
Secondary flow in a curved artery model with Newtonian and non-Newtonian blood-analog fluids
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.
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.
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A Mahdy
2016-01-01
Full Text Available In this contribution a numerical study is carried out to analyze the effect of slip at the boundary of unsteady two-dimensional MHD flow of a non-Newtonian fluid over a stretching surface having a prescribed surface temperature in the presence of suction or blowing at the surface. Casson fluid model is used to characterize the non-Newtonian fluid behavior. With the help of similarity transformations, the governing partial differential equations corresponding to the momentum and heat transfer are reduced to a set of non-linear ordinary differential equations, which are then solved for local similar solutions using the very robust computer algebra software MATLAB. The flow features and heat transfer characteristics for different values of the governing parameters are graphically presented and discussed in detail. Comparison with available results for certain cases is excellent. The effect of increasing values of the Casson parameter is seen to suppress the velocity field. But the temperature is enhanced with increasing Casson parameter. For increasing slip parameter, velocity increases and thermal boundary layer becomes thinner in the case of suction or blowing.
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.
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.
Flow of Chemically Reactive non-Newtonian Fluids in Twin-Screw Extruders
Zhu, Weimin; Jaluria, Yogesh
1998-11-01
Many applications of twin-screw extruders are found in the processing of food, plastics, pharmaceutical materials and other highly viscous materials. In reactive extrusion, complex interactions in which the flow pattern, and the heat and mass transfer are affected by viscous dissipation, reaction energy, convection, residence time distribution and rheology of the materials may occur. The fluid flow, heat transfer and chemical reactions in a fully intermeshing, corotating and self wiping twin screw extruder were investigated numerically by using the finite volume method. The screw channel of a twin screw extruder are approximated as translation (parabolic) domain and intermeshing (elliptic) domain. The full governing equations were solved to determine the velocity components in the three coordinate directions. The energy equation is coupled with the equations of motion through viscosity. The Residence Time Distribution (RTD), was obtained by using a particle tracking method. The flow field, temperature field, pressure as well as RTD and chemical conversion were obtained by numerical simulation and the results yielded agreement with experimental measurements and expected physical characteristic of the process.
Study of blades inclination influence of gate impeller with a non-Newtonian fluid of Bingham
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Rahmani Lakhdar
2016-01-01
Full Text Available A large number of chemical operations, biochemical or petrochemical industry is very depending on the rheological fluids nature. In this work, we study the case of highly viscous of viscoplastic fluids in a classical system of agitation: a cylindrical tank with plate bottom without obstacles agitated by gate impeller agitator. We are interested to the laminar, incompressible and isothermal flows. We devote to a numerical approach carried out using an industrial code CFD Fluent 6.3.26 based on the method of finites volumes discretization of Navier - Stokes equations formulated in variables (U.V.P. The threshold of flow related to the viscoplastic behavior is modeled by a theoretical law of Bingham. The results obtained are used to compare between the five configurations suggested of power consumption. We study the influence of inertia by the variation of Reynolds number.
Sultanov, Renat A; Engelbrekt, Brent; Blankenbecler, Richard
2008-01-01
Methods of Computational Fluid Dynamics are applied to simulate pulsatile blood flow in human vessels and in the aortic arch. The non-Newtonian behaviour of the human blood is investigated in simple vessels of actual size. A detailed time-dependent mathematical convergence test has been carried out. The realistic pulsatile flow is used in all simulations. Results of computer simulations of the blood flow in vessels of two different geometries are presented. For pressure, strain rate and velocity component distributions we found significant disagreements between our results obtained with realistic non-Newtonian treatment of human blood and widely used method in literature: a simple Newtonian approximation. A significant increase of the strain rate and, as a result, wall sear stress distribution, is found in the region of the aortic arch. We consider this result as theoretical evidence that supports existing clinical observations and those models not using non-Newtonian treatment underestimate the risk of disru...
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.
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Nabil T. M. Eldabe
2014-01-01
Full Text Available This paper is devoted to the study of the peristaltic motion of non-Newtonian fluid with heat and mass transfer through a porous medium in the channel under the effect of magnetic field. A modified Casson non-Newtonian constitutive model is employed for the transport fluid. A perturbation series’ method of solution of the stream function is discussed. The effects of various parameters of interest such as the magnetic parameter, Casson parameter, and permeability parameter on the velocity, pressure rise, temperature, and concentration are discussed and illustrated graphically through a set of figures.
Chun, Myung-Suk; Chun, Byoungjin; Lee, Ji-Young; Complex Fluids Team
2016-11-01
We investigate the externally time-dependent pulsatile electrokinetic viscous flows by extending the previous simulations concerning the electrokinetic microfluidics for different geometries. The external body force originated from between the nonlinear Poisson-Boltzmann field and the flow-induced electric field is employed in the Cauchy momentum equation, and then the Nernst-Planck equation in connection with the net current conservation is coupled. Our explicit model allows one to quantify the effects of the oscillating frequency and conductance of the Stern layer, considering the shear thinning effect and the strong electric double layer interaction. This presentation reports the new results regarding the implication of optimum frequency pressure pulsations toward realizing mechanical to electrical energy transfer with high conversion efficiencies. These combined factors for different channel dimension are examined in depth to obtain possible enhancements of streaming current, with taking advantage of pulsating pressure field. From experimental verifications by using electrokinetic power chip, it is concluded that our theoretical framework can serve as a useful basis for micro/nanofluidics design and potential applications to the enhanced energy conversion. NRF of Korea (No.2015R1A2A1A15052979) and KIST (No.2E26490).
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A. Zaman
2015-03-01
Full Text Available A two-dimensional model is used to analyze the unsteady pulsatile flow of blood through a tapered artery with stenosis. The rheology of the flowing blood is captured by the constitutive equation of Carreau model. The geometry of the time-variant stenosis has been used to carry out the present analysis. The flow equations are set up under the assumption that the lumen radius is sufficiently smaller than the wavelength of the pulsatile pressure wave. A radial coordinate transformation is employed to immobilize the effect of the vessel wall. The resulting partial differential equations along with the boundary and initial conditions are solved using finite difference method. The dimensionless radial and axial velocity, volumetric flow rate, resistance impedance and wall shear stress are analyzed for normal and diseased artery with particular focus on variation of these quantities with non-Newtonian parameters.
Lemarchand, Claire A; Todd, Billy D; Daivis, Peter J; Hansen, Jesper S
2015-01-01
The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear is investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity and normal stress differences of the bitumen mixture are computed at different shear rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid. The corresponding molecular structure is studied at the same shear rates and temperatures. The Cooee bitumen is able to reproduce experimental results showing the formation of nanoaggregates composed of stacks of flat aromatic molecules. These nanoaggregates are immersed in a solvent of saturated hydrocarbon molecules. The nanoaggregates are shown to break up at very high shear rates, leading only to a minor effect on the viscosity of the mixture. At low shear rates, bitumen can be seen as a colloidal suspension of nanoaggregates in a solvent. The slight anisotropy of the whole sample due to the nanoaggregates is considered and quantified...
El-Amin, Mohamed
2012-06-02
The problem of thermal dispersion effects on unsteady free convection from an isothermal horizontal circular cylinder to a non-Newtonian fluid saturating a porous medium is examined numerically. The Darcy-Brinkman-Forchheimer model is employed to describe the flow field. The thermal diffusivity coefficient has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. The simultaneous development of the momentum and thermal boundary layers are obtained by using finite difference method. The stability conditions are determined for each difference equation. Using an explicit finite difference scheme, solutions at each time-step have been found and then stepped forward in time until reaching steady state solution. Velocity and temperature profiles are shown graphically. It is found that as time approaches infinity, the values of friction factor and heat transfer coefficient approach the steady state values.
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.
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A. O. Morais
2015-06-01
Full Text Available AbstractEnhanced heat transfer in tubes under laminar flow conditions can be found in coils or corrugated tubes or in the presence of high wall relative roughness, curves, pipe fittings or mechanical vibration. Modeling these cases can be complex because of the induced secondary flow. A modification of the Graetz problem for non-Newtonian power-law flow is proposed to take into account the augmented heat transfer by the introduction of an effective radial thermal diffusivity. The induced mixing was modeled as an increased radial heat transfer in a straight tube. Three experiments using a coiled tube and a tubular heat exchanger with high relative wall roughness are presented in order to show how this parameter can be obtained. Results were successfully correlated with Reynolds number. This approach can be useful for modeling laminar flow reactors (LFR and tubular heat exchangers available in the chemical and food industries.
Institute of Scientific and Technical Information of China (English)
HE Wen-zhi; LI Guang-ming; JIANG Zhao-hua; SUO Quan-ling
2007-01-01
Liquids to be broken up using a prefilming airblast atomizer are usually Newton liquids with relatively low viscosities. While in some industrial processes, such as spray drying, liquids to be atomized are high concentration suspensions or non-Newtonian fluids with high viscosities. In this paper, non-Newtonian fluids with viscosity up to 4. 4 Pa · s were effectively atomized using a specially designed prefilming airblast atomizer. The atomizer enabled liquid to extend to a thickness-adjustable film and forced the atomizing air stream to swirl with 30° or 45° through gas distributors with spiral slots. The liquid film was impinged by the swirling air stream resulting in the disintegration of the film into drops. Drop sizes were measured using a laser diffraction technique.An improved four-parameter mathematical model was established to relate the Sauter mean diameter of drops to the atomization conditions in terms of power dependencies on three dimensionless groups: Weber number,Ohnesorge number and air liquid mass ratio. The friction on the surface of the 1iquid film made by swirling air stream played an important role in the prefilming atomization at the conditions of low air velocity and low liquid viscosity. In this case, the liquid film was disintegrated into drops according to the classical wavy-sheet mechanism, thus thinner liquid films and high swirl levels of the atomizing air produced smaller drops. With the increase of the air velocity and the liquid viscosity, the effect of the friction on the prefilming atomization relatively weakened, whereas the impingement on the liquid film made by atomizing air stream in a direction normal to the liquid film and corresponding momentum transfer gradually strengthened and eventually dominated the disruption of liquid into drops, which induced that the initial thickness of the liquid film and the swirl of atomizing air stream exercised a minor influence on the drop sizes.
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Mey, Paula; Varges, Priscilla R.; Mendes, Paulo R. de Souza [Dept. of Mechanical Engineering. Pontificia Universidade Catolica do RJ (PUC-Rio), RJ (Brazil)], e-mails: prvarges@puc-rio.br, pmendes@puc-rio.br
2010-07-01
This research looked for a method to determine the binary diffusion coefficient D of salts in liquids (especially in drilling fluids) not only accurately, but in a reasonable time. We chose to use the Taylor Dispersion Method. This technique has been used for measuring binary diffusion coefficients in gaseous, liquid and supercritical fluids, due to its simplicity and accuracy. In the method, the diffusion coefficient is determined by the analysis of the dispersion of a pulse of soluble material in a solvent flowing laminarly through a tube. This work describes the theoretical basis and the experimental requirements for the application of the Taylor Dispersion Method, emphasizing the description of our experiment. A mathematical formulation for both Newtonian and non-Newtonian fluids is presented. The relevant sources of errors are discussed. The experimental procedure and associated analysis are validated by applying the method in well known systems, such as NaCl in water.D of salts in liquids (especially in drilling fluids) not only accurately, but in a reasonable time. We chose to use the Taylor Dispersion Method. This technique has been used for measuring binary diffusion coefficients in gaseous, liquid and supercritical fluids, due to its simplicity and accuracy. In the method, the diffusion coefficient is determined by the analysis of the dispersion of a pulse of soluble material in a solvent flowing laminarly through a tube. This work describes the theoretical basis and the experimental requirements for the application of the Taylor Dispersion Method, emphasizing the description of our experiment. A mathematical formulation for both Newtonian and non-Newtonian fluids is presented. The relevant sources of errors are discussed. The experimental procedure and associated analysis are validated by applying the method in well known systems, such as NaCl in water. (author)
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Ziye Ling
2017-01-01
Full Text Available In this paper, an aqueous solution of xanthan gum (XG at a weight fraction as high as 0.2% was elected as the non-Newtonian base liquid, the multi-walled carbon nanotubes (MWCNTs dispersed into non-Newtonian XG aqueous at different weight factions of MWCNTs was prepared. Convection heat transfer of non-Newtonian nanofluids in the shell side of helical baffled heat exchanger combined with elliptic tubes has been investigated experimentally and numerically using single-phase flow model. Results showed that the enhancement of the convective heat transfer coefficient increases with an increase in the Reynolds number and the nanoparticle concentration. For nanofluids with 0.2 wt %, 0.5 wt % and 1.0 wt % MWCNTs, the Nusselt number, respectively, increases by 11%, 21% and 35% on average at the same Reynolds number, while the comprehensive thermal performance factors are 3%–5%, 15%–17% and 24%–26% higher than that of base fluid at the same volume rate. A remarkable heat transfer enhancement can be obtained by adding MWCNTs into XG aqueous solution based on thermal resistance analysis. Correlations have been suggested for the shell-side Nusselt number and friction factor of non-Newtonian nanofluids in the helical baffled heat exchanger with elliptic tubes. Good agreements existed between corrections and experimental data.
Directory of Open Access Journals (Sweden)
K. Mehala
2016-12-01
Full Text Available The hydrodynamic bearings are stressed by severe workings conditions, such as speed, load, and the oil will be increasingly solicit by pressure and shear. The Newtonian behavior is far from being awarded in this case, the most loaded bearings operating at very high speeds; the shear rate of the oil is of higher order. A numerical analysis of the behavior of non-Newtonian fluid for plain cylindrical journal bearing finite dimension coated with antifriction material with a high tin content, for to facilitate the accommodation of the surfaces and save the silk of the shaft in the case of a contact. this analyses is implemented using the code-ANSYS CFX, by solving the energy equation with the finite difference method, considering that laminar regime and the fluid is non Newtonian by using the power law Ostwald model, the coefficient n is equal to 1.25 and for different model such as Bingham, cross and Hereshek-Bulkley model. This study aims to better predict the non-Newtonian behavior of the oil film in bearings operating under more severe conditions. The purpose conducted during this study is to predict the effect of non-Newtonian behavior of the film; the journal bearing operating under severe conditions, the speed of rotation varies from 1000 to 9000 rpm and the bearing working under radial load 2 to 10 kN. Temperature and the pressure within the fluid film assumed non-Newtonian are high, with a coefficient n greater than 1 that is to say for viscoelastic fluids.
Di Federico, V.; Ciriello, V.
2011-12-01
Non-Newtonian fluid flow in porous media is of considerable interest in hydrology, chemical and petroleum engineering, and biofluid mechanics. We consider an infinite porous domain of plane (d=1), cylindrical (d=2) or semi-spherical geometry (d=3), having uniform permeability k and porosity Φ, initially at uniform pressure and saturated by a weakly compressible non-Newtonian fluid, and analyze the dynamics of the pressure variation generated within the domain by an instantaneous mass injection m0 in its origin. The fluid is described by a rheological power-law model of given consistency index H and flow behavior index n; the flow law is a modified Darcy's law depending on H, Φ, n. Coupling flow law and mass balance equations yields the nonlinear partial differential equation governing the pressure field; an analytical solution is derived in space r and time t as a function of a self-similar variable η=r/tβ(n). We revisit and expand the work in previous papers by providing a dimensionless general formulation and solution to the problem for d=1,2,3. When a shear-thinning fluid (nfluids; the front velocity is proportional to t(n-2)/2 in plane geometry, t(2n-3)/(3-n) in cylindrical geometry, and t(3n-4)/(4-2n) in semi-spherical geometry. The front position is a markedly increasing function of n and is inversely dependent on d; the pressure front advances at a slower rate for larger values of compressibility, higher injected mass and lower porosity. When pressure is considered, it is seen that an increase in d from 1 to 3 brings about an order of magnitude reduction. An increase in compressibility implies a significant decrease in pressure, especially at early times. To reflect the uncertainty inherent in values of the problem parameters, we then consider selected properties of fluid (flow behavior index n) and porous domain (permeability k, porosity Φ, and medium compressibility cp) as independent random variables with uniform probability distribution. The
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
Linking the fractional derivative and the Lomnitz creep law to non-Newtonian time-varying viscosity
Pandey, Vikash; Holm, Sverre
2016-09-01
Many of the most interesting complex media are non-Newtonian and exhibit time-dependent behavior of thixotropy and rheopecty. They may also have temporal responses described by power laws. The material behavior is represented by the relaxation modulus and the creep compliance. On the one hand, it is shown that in the special case of a Maxwell model characterized by a linearly time-varying viscosity, the medium's relaxation modulus is a power law which is similar to that of a fractional derivative element often called a springpot. On the other hand, the creep compliance of the time-varying Maxwell model is identified as Lomnitz's logarithmic creep law, making this possibly its first direct derivation. In this way both fractional derivatives and Lomnitz's creep law are linked to time-varying viscosity. A mechanism which yields fractional viscoelasticity and logarithmic creep behavior has therefore been found. Further, as a result of this linking, the curve-fitting parameters involved in the fractional viscoelastic modeling, and the Lomnitz law gain physical interpretation.
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M. H. Yazdi
2014-01-01
Full Text Available In the present study, the first and second law analyses of power-law non-Newtonian flow over embedded open parallel microchannels within micropatterned permeable continuous moving surface are examined at prescribed surface temperature. A similarity transformation is used to reduce the governing equations to a set of nonlinear ordinary differential equations. The dimensionless entropy generation number is formulated by an integral of the local rate of entropy generation along the width of the surface based on an equal number of microchannels and no-slip gaps interspersed between those microchannels. The velocity, the temperature, the velocity gradient, and the temperature gradient adjacent to the wall are substituted into this equation resulting from the momentum and energy equations obtained numerically by Dormand-Prince pair and shooting method. Finally, the entropy generation numbers, as well as the Bejan number, are evaluated. It is noted that the presence of the shear thinning (pseudoplastic fluids creates entropy along the surface, with an opposite effect resulting from shear thickening (dilatant fluids.
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M. Rahimi-Gorji
2015-06-01
Full Text Available An analytical investigation is applied for unsteady motion of a rigid spherical particle in a quiescent shear-thinning power-law fluid. The results were compared with those obtained from Collocation Method (CM and the established Numerical Method (Fourth order Runge–Kutta scheme. It was shown that CM gave accurate results. Collocation Method (CM and Numerical Method are used to solve the present problem. We obtained that the CM which was used to solve such nonlinear differential equation with fractional power is simpler and more accurate than series method such as HPM which was used in some previous works by others but the new method named Akbari-Ganji’s Method (AGM is an accurate and simple method which is slower than CM for solving such problems. The terminal settling velocity—that is the velocity at which the net forces on a falling particle eliminate—for three different spherical particles (made of plastic, glass and steel and three flow behavior index n, in three sets of power-law non-Newtonian fluids was investigated, based on polynomial solution (CM. Analytical results obtained indicated that the time of reaching the terminal velocity in a falling procedure is significantly increased with growing of the particle size that validated with Numerical Method. Further, with approaching flow behavior to Newtonian behavior from shear-thinning properties of flow (n → 1, the transient time to achieving the terminal settling velocity is decreased.
A constitutive framework for the non-Newtonian pressure tensor of a simple fluid under planar flows.
Hartkamp, Remco; Todd, B D; Luding, Stefan
2013-06-28
Non-equilibrium molecular dynamics simulations of an atomic fluid under shear flow, planar elongational flow, and a combination of shear and elongational flow are unified consistently with a tensorial model over a wide range of strain rates. A model is presented that predicts the pressure tensor for a non-Newtonian bulk fluid under a homogeneous planar flow field. The model provides a quantitative description of the strain-thinning viscosity, pressure dilatancy, deviatoric viscoelastic lagging, and out-of-flow-plane pressure anisotropy. The non-equilibrium pressure tensor is completely described through these four quantities and can be calculated as a function of the equilibrium material constants and the velocity gradient. This constitutive framework in terms of invariants of the pressure tensor departs from the conventional description that deals with an orientation-dependent description of shear stresses and normal stresses. The present model makes it possible to predict the full pressure tensor for a simple fluid under various types of flows without having to produce these flow types explicitly in a simulation or experiment.
Entropy analysis of convective MHD flow of third grade non-Newtonian fluid over a stretching sheet
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M.M. Rashidi
2017-03-01
Full Text Available The purpose of this article is to study and analyze the convective flow of a third grade non-Newtonian fluid due to a linearly stretching sheet subject to a magnetic field. The dimensionless entropy generation equation is obtained by solving the reduced momentum and energy equations. The momentum and energy equations are reduced to a system of ordinary differential equations by a similarity method. The optimal homotopy analysis method (OHAM is used to solve the resulting system of ordinary differential equations. The effects of the magnetic field, Biot number and Prandtl number on the velocity component and temperature are studied. The results show that the thermal boundary-layer thickness gets decreased with increasing the Prandtl number. In addition, Brownian motion plays an important role to improve thermal conductivity of the fluid. The main purpose of the paper is to study the effects of Reynolds number, dimensionless temperature difference, Brinkman number, Hartmann number and other physical parameters on the entropy generation. These results are analyzed and discussed.
Drag Force of Non-newtonian Fluid on a Continuous Moving Surface with Strong Suction/Blowing
Institute of Scientific and Technical Information of China (English)
郑连存; 张欣欣; 赫冀成
2003-01-01
A theoretical analysis for the laminar boundary layer flow of a non-Newtonian fluid on a continuous moving flat plate with surface strong suction/blowing is made. The types of potential flows necessary for similar solutions to the boundary layer are determined and both analytical and numerical solutions are presented. It is shown that the solution of the boundary layer problem depends not only on the ratio of the velocity of the plate to the velocity of the free stream, but also on the suction/blowing parameter. The skin friction decreases with increasing the parameters of power law and blowing. In the case of existing suction, the shear force decreases with the increases of tangential velocity, the largest shear force occurs at wall and the smallest shear force occurs at the edge of the boundary layer. However, in the case of existing surface blowing, the shear force initially increases with tangentialvelocity and the biggest shear force occurs at the interior of the boundary layer, the skin friction approaches to zero as the blowing rate approaches the critical value.
MASS TRANSFER COEFFICIENTS FOR A NON-NEWTONIAN FLUID AND WATER WITH AND WITHOUT ANTI-FOAM AGENTS
Energy Technology Data Exchange (ETDEWEB)
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.
Yeylaghi, Shahab; Moa, Belaid; Buckham, Bradley; Oshkai, Peter; Vasquez, Jose; Crawford, Curran
2017-09-01
A comprehensive modeling of landslide generated waves using an in-house parallel Incompressible Smoothed Particle Hydrodynamics (ISPH) code is presented in this paper. The study of landslide generated waves is challenging due to the involvement of several complex physical phenomena, such as slide-water interaction, turbulence and complex free surface profiles. A numerical tool that can efficiently calculate both slide motion, impact with the surface and the resulting wave is needed for ongoing study of these phenomena. Mesh-less numerical methods, such as Smoothed Particle Hydrodynamics (SPH), handle the slide motion and the complex free surface profile with ease. In this paper, an in-house parallel explicit ISPH code is used to simulate both subaerial and submarine landslides in 2D and in more realistic 3D applications. Both rigid and deformable slides are used to generate the impulsive waves. A landslide case is simulated where a slide falls into a non-Newtonian reservoir fluid (water-bentonite mixture). A new technique is also proposed to calculate the motion of a rigid slide on an inclined ramp implicitly, without using the prescribed motion in SPH. For all the test cases, results generated from the proposed ISPH method are compared with available experimental data and show good agreement.
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Jamshid M. Nouri
2008-03-01
Full Text Available Mean and rms velocity characteristics of two Newtonian flows at Reynolds numbers of 12,800 (glycerin solution and 48,000 (water and of a non-Newtonian flow (0.2% CMC solution, at a power number similar to the Newtonian glycerin flow in a mixing vessel stirred by a 60° pitched blade impeller have been measured by laser Doppler velocimetry (LDV. The velocity measurements, resolved over 360° and 1.08° of impeller rotation, showed that the mean flow of the two power number matched glycerin and CMC flows were similar to within 3% of the impeller tip velocity and the turbulence intensities generally lower in the CMC flow by up to 5% of the tip velocity. The calculated mean flow quantities showed similar discharge coefficient and pumping efficiency in all three flows and similar strain rate between the two power number matched glycerin and CMC flows; the strain rate of the higher Reynolds number Newtonian flow was found to be slightly higher. The energy balance around the impeller indicated that the CMC flow dissipated up to 9% more of the total input power and converted 7% less into the turbulence compared to the glycerin flow with the same power input which could lead to less effective mixing processes where the micro-mixing is important.
Lemarchand, Claire A.; Bailey, Nicholas P.; Todd, Billy D.; Daivis, Peter J.; Hansen, Jesper S.
2015-06-01
The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear are investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity, normal stress differences, and pressure of the bitumen mixture are computed at different shear rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid at all temperatures. In addition, the Cooee model is able to reproduce experimental results showing the formation of nanoaggregates composed of stacks of flat aromatic molecules in bitumen. These nanoaggregates are immersed in a solvent of saturated hydrocarbon molecules. At a fixed temperature, the shear-shinning behavior is related not only to the inter- and intramolecular alignments of the solvent molecules but also to the decrease of the average size of the nanoaggregates at high shear rates. The variation of the viscosity with temperature at different shear rates is also related to the size and relative composition of the nanoaggregates. The slight anisotropy of the whole sample due to the nanoaggregates is considered and quantified. Finally, the position of bitumen mixtures in the broad literature of complex systems such as colloidal suspensions, polymer solutions, and associating polymer networks is discussed.
Castellanos, Maria Monica; Pathak, Jai A; Leach, William; Bishop, Steven M; Colby, Ralph H
2014-07-15
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.
Viscous-elastic dynamics of power-law fluids within an elastic cylinder
Gat, Amir; Boyko, Evgeniy; Bercovici, Moran
2016-11-01
We study the fluid-structure interaction dynamics of non-Newtonian flow through a slender linearly elastic cylinder at the creeping flow regime. Specifically, considering power-law fluids and applying the thin shell approximation for the elastic cylinder, we obtain a non-homogeneous p-Laplacian equation governing the viscous-elastic dynamics. We obtain exact solutions for the pressure and deformation fields for various initial and boundary conditions, for both shear thinning and shear thickening fluids. In particular, impulse or a step in inlet pressure yield self-similar solutions, which exhibit a compactly supported propagation front solely for shear thinning fluids. Applying asymptotic expansions, we provide approximations for weakly non-Newtonian behavior showing good agreement with the exact solutions sufficiently far from the front.
Mass Transport in a Thin Layer of Bi-Viscous Mud Under Surface Waves
Institute of Scientific and Technical Information of China (English)
NG Chiu-on; FU Sau-chung; BAI Yu-chuan(白玉川)
2002-01-01
The mass transport in a thin layer of non-Newtonian bed mud under surface waves is examined with a two-fluidStokes boundary layer model. The mud is assumed to be a bi-viscous fluid, which tends to resist motion for small-appliedstresses, but flows readily when the yield stress is exceeded. Asymptotic expansions suitable for shallow fluid layers areapplied, and the second-order solutions for the mass transport induced by surface progressive waves are obtained numeri-cally. It is found that the stronger the non-Newtonian behavior of the mud, the more pronounced intermittency of theflow. Consequently, the mass transport velocity is diminished in magnitude, and can even become negative (i. e., oppo-site to wave propagation) for a certain range of yield stress.
Energy Technology Data Exchange (ETDEWEB)
Inoue, M.; Nakayama, A. [Shizuoka University, Shizuoka (Japan). Faculty of Engineering
1996-09-25
Three-dimensional numerical calculations have been performed to simulate the viscous and porous inertia effects on the pressure drop in a non-Newtonian fluid flow through a porous medium. Cubes placed in an infinite space have been proposed as a three-dimensional model of microscopic porous structure. A full set of three-dimensional momentum equations is solved along with the continuity equation at a pore scale, so as to simulate a flow through an infinite number of obstacles arranged in a regular pattern. The microscopic numerical results, thus obtained, are processed to extract the macroscopic relationship between the pressure gradient-mass flow rate. Comparing the results based on the two- and three-dimensional models, it has been found that only the three-dimensional model can capture the porous inertia effects on the pressure drop correctly. 13 refs., 6 figs.
El-Amin, Mohamed
2011-05-14
In this paper, a finite difference scheme is developed to solve the unsteady problem of combined heat and mass transfer from an isothermal curved surface to a porous medium saturated by a non-Newtonian fluid. The curved surface is kept at constant temperature and the power-law model is used to model the non-Newtonian fluid. The explicit finite difference method is used to solve simultaneously the equations of momentum, energy and concentration. The consistency of the explicit scheme is examined and the stability conditions are determined for each equation. Boundary layer and Boussinesq approximations have been incorporated. Numerical calculations are carried out for the various parameters entering into the problem. Velocity, temperature and concentration profiles are shown graphically. It is found that as time approaches infinity, the values of wall shear, heat transfer coefficient and concentration gradient at the wall, which are entered in tables, approach the steady state values.
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Macha Madhu
2015-01-01
Full Text Available Two-dimensional MHD mixed convection boundary layer flow of heat and mass transfer stagnation-point flow of a non-Newtonian power-law nanofluid towards a stretching surface in the presence of thermal radiation and heat source/sink is investigated numerically. The non-Newtonian nanofluid model incorporates the effects of Brownian motion and thermophoresis. The basic transport equations are made dimensionless first and the complete nonlinear differential equations with associated boundary conditions are solved numerically by finite element method (FEM. The numerical calculations for velocity, temperature, and nanoparticles volume fraction profiles for different values of the physical parameters to display the interesting aspects of the solutions are presented graphically and discussed. The skin friction coefficient, the local Nusslet number and the Sherwood number are exhibited and examined. Our results are compatible with the existing results for a special case.
Institute of Scientific and Technical Information of China (English)
闻建平; 贾晓强; 毛国柱
2004-01-01
A small scale isotropic mass transfer model was developed for the local liquid side mass transfer coefficients in gas-liquid-solid three-phase flow airlift loop reactor for Newtonian and non-Newtonian fluids. It is based on Higbie's penetration theory and Kolmogoroff's theory of isotropic turbulence with kl=3√2D∈11/3/π(η1-1/3-λf-1/3)where e1 is local rate of energy dissipation, Af is the local microscale, r/l is the local Kolmogoroff scale and D is the diffusion coefficient. The capability of the proposed model is discussed in the light of experimental data obtained from 12 L gas-liquid-solid three-phase flow airlift loop reactor using Newtonian and non-Newtonian fluids. Good agreement with the experimental data was obtained over a wide range of conditions suggesting a general applicability of the proposed model.
Diffusion Coefficients of L-arginine in Non-Newtonian Fluid%L-精氨酸在非牛顿流体中的扩散系数
Institute of Scientific and Technical Information of China (English)
朱春英; 马友光; 季喜燕
2008-01-01
L-Arginine is an important component of amino acid injection. Its diffusion in body fluid and blood is of key importance to understand drug diffusion and drug release. As a fundamental demand for study and being a considerably valuable reference for application, in this study, the diffusion coefficients of L-arginine in polyacryla-mide(PAM) aqueous solution used as non-Newtonian fluid similar to blood and body fluid were measured using a holographic interferometer. The effects of interaction among molecules and solution concentration on diffusion were analyzed and discussed, respectively. Based on the obstruction-scaling model, a novel modified model was presented for predicting diffusivity of solute in non-Newtonian fluid. Good agreement was achieved between the calculated value and the experimental data.
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Salama Faiza A.
2011-01-01
Full Text Available An analysis is carried out to study the effect of heat and mass transfer on a non-Newtonian-fluid between two infinite parallel walls, one of them moving with a uniform velocity under the action of a transverse magnetic field. The moving wall moves with constant velocity in the direction of fluid flow while the free stream velocity is assumed to follow the exponentially increasing small perturbation law. Time-dependent wall suction is assumed to occur at permeable surface. The governing equations for the flow are transformed into a system of nonlinear ordinary differential equations by perturbation technique and are solved numerically by using the shooting technique with fourth order Runge-Kutta integration scheme. The effect of non-Newtonian parameter, magnetic pressure parameter, Schmidt number, Grashof number and modified Grashof number on velocity, temperature, concentration and the induced magnetic field are discussed. Numerical results are given and illustrated graphically for the considered Problem.
Hundertmark-Zaušková, A.; Lukáčová-Medviďová, M.; Nečasová, Š. (Šárka)
2016-01-01
We study the existence of weak solution for unsteady fluid-structure interaction problem for shear-thickening flow. The time dependent domain has at one part a flexible elastic wall. The evolution of fluid domain is governed by the generalized string equation with action of the fluid forces. The power-law viscosity model is applied to describe shear-dependent non-Newtonian fluids.
2011-01-01
Many experiments have been conducted to study the hydrodynamic characteristics of column reactors and loop reactors. In this present work, a novel combined loop airlift fluidized bed reactor was developed to study the effect of superficial gas and liquid velocities, particle diameter, fluid properties on gas holdup by using Newtonian and non-Newtonian liquids. Compressed air was used as gas phase. Water, 5% n-butanol, various concentrations of glycerol (60 and 80%) were used as Newtonian liqu...
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.
Directory of Open Access Journals (Sweden)
Sivakumar Venkatachalam
2011-09-01
Full Text Available Many experiments have been conducted to study the hydrodynamic characteristics of column reactors and loop reactors. In this present work, a novel combined loop airlift fluidized bed reactor was developed to study the effect of superficial gas and liquid velocities, particle diameter, fluid properties on gas holdup by using Newtonian and non-Newtonian liquids. Compressed air was used as gas phase. Water, 5% n-butanol, various concentrations of glycerol (60 and 80% were used as Newtonian liquids, and different concentrations of carboxy methyl cellulose aqueous solutions (0.25, 0.6 and 1.0% were used as non-Newtonian liquids. Different sizes of spheres, Bearl saddles and Raschig rings were used as solid phases. From the experimental results, it was found that the increase in superficial gas velocity increases the gas holdup, but it decreases with increase in superficial liquid velocity and viscosity of liquids. Based on the experimental results a correlation was developed to predict the gas hold-up for Newtonian and non-Newtonian liquids for a wide range of operating conditions at a homogeneous flow regime where the superficial gas velocity is approximately less than 5 cm/s
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.
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.
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.
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.
Indian Academy of Sciences (India)
AHMED A AFIFY; MOHAMED ABD EL-AZIZ
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 increasewith an increase in Biot number.
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.
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
Shaw, Sachin; Murthy, P V S N
2010-09-01
The present investigation deals with finding the trajectories of the drug dosed magnetic carrier particle in a microvessel with two-phase fluid model which is subjected to the external magnetic field. The radius of the microvessel is divided into the endothelial glycocalyx layer in which the blood is assumed to obey Newtonian character and a core and plug regions where the blood obeys the non-Newtonian Herschel-Bulkley character which is suitable for the microvessel of radius 50 microm. The carrier particles, bound with nanoparticles and drug molecules are injected into the vascular system upstream from malignant tissue, and captured at the tumor site using a local applied magnetic field. The applied magnetic field is produced by a cylindrical magnet positioned outside the body and near the tumor position. The expressions for the fluidic force for the carrier particle traversing in the two-phase fluid in the microvessel and the magnetic force due to the external magnetic field are obtained. Several factors that influence the magnetic targeting of the carrier particles in the microvasculature, such as the size of the carrier particle, the volume fraction of embedded magnetic nanoparticles, and the distance of separation of the magnet from the axis of the microvessel are considered in the present problem. An algorithm is given to solve the system of coupled equations for trajectories of the carrier particle in the invasive case. The trajectories of the carrier particle are found for both invasive and noninvasive targeting systems. A comparison is made between the trajectories in these cases. Also, the present results are compared with the data available for the impermeable microvessel with single-phase fluid flow. Also, a prediction of the capture of therapeutic magnetic nanoparticle in the impermeable microvasculature is made for different radii, distances and volume fractions in both the invasive and noninvasive cases.
Kabinejadian, Foad; Ghista, Dhanjoo N
2012-09-01
We have recently developed a novel design for coronary arterial bypass surgical grafting, consisting of coupled sequential side-to-side and end-to-side anastomoses. This design has been shown to have beneficial blood flow patterns and wall shear stress distributions which may improve the patency of the CABG, as compared to the conventional end-to-side anastomosis. In our preliminary computational simulation of blood flow of this coupled sequential anastomoses design, the graft and the artery were adopted to be rigid vessels and the blood was assumed to be a Newtonian fluid. Therefore, the present study has been carried out in order to (i) investigate the effects of wall compliance and non-Newtonian rheology on the local flow field and hemodynamic parameters distribution, and (ii) verify the advantages of the CABG coupled sequential anastomoses design over the conventional end-to-side configuration in a more realistic bio-mechanical condition. For this purpose, a two-way fluid-structure interaction analysis has been carried out. A finite volume method is applied to solve the three-dimensional, time-dependent, laminar flow of the incompressible, non-Newtonian fluid; the vessel wall is modeled as a linearly elastic, geometrically non-linear shell structure. In an iteratively coupled approach the transient shell equations and the governing fluid equations are solved numerically. The simulation results indicate a diameter variation ratio of up to 4% and 5% in the graft and the coronary artery, respectively. The velocity patterns and qualitative distribution of wall shear stress parameters in the distensible model do not change significantly compared to the rigid-wall model, despite quite large side-wall deformations in the anastomotic regions. However, less flow separation and reversed flow is observed in the distensible models. The wall compliance reduces the time-averaged wall shear stress up to 32% (on the heel of the conventional end-to-side model) and somewhat
A Remark on the Time Decay of Non-Newtonian Flows in R3%关于非牛顿流体衰减性的一个注记
Institute of Scientific and Technical Information of China (English)
殷谷良
2009-01-01
In the study of long time asymptotic behaviors of the solutions to a class system of the incompressible non-Newtonian fluid flows in R3, it is proved that the weak solutions decay in L2 norm at (1+t) and the error of difference between non-Newtonian fluid and linear equation is also investigated. The findings are mainly based on the classic Fourier splitting methods.
Directory of Open Access Journals (Sweden)
Azeem SHAHZAD
2013-02-01
Full Text Available In this article, we study the power law model of steady state, viscous, incompressible MHD flow over a vertically stretching sheet. Furthermore, heat transfer is also addressed by using the convective boundary conditions. The coupled partial differential equations are transformed into ordinary differential equations (ODEs using similarity transformations. The transformed highly non-linear ODEs are solved by using the Homotopy Analysis Method (HAM. The influence of different parameters on the velocity and temperature fields are analyzed and discussed.
Khan, M O; Steinman, D A; Valen-Sendstad, K
2017-07-01
Computational fluid dynamics (CFD) shows promise for informing treatment planning and rupture risk assessment for intracranial aneurysms. Much attention has been paid to the impact on predicted hemodynamics of various modelling assumptions and uncertainties, including the need for modelling the non-Newtonian, shear-thinning rheology of blood, with equivocal results. Our study clarifies this issue by contextualizing the impact of rheology model against the recently demonstrated impact of CFD solution strategy on the prediction of aneurysm flow instabilities. Three aneurysm cases were considered, spanning a range of stable to unstable flows. Simulations were performed using a high-resolution/accuracy solution strategy with Newtonian and modified-Cross rheology models and compared against results from a so-called normal-resolution strategy. Time-averaged and instantaneous wall shear stress (WSS) distributions, as well as frequency content of flow instabilities and dome-averaged WSS metrics, were minimally affected by the rheology model, whereas numerical solution strategy had a demonstrably more marked impact when the rheology model was fixed. We show that point-wise normalization of non-Newtonian by Newtonian WSS values tended to artificially amplify small differences in WSS of questionable physiological relevance in already-low WSS regions, which might help to explain the disparity of opinions in the aneurysm CFD literature regarding the impact of non-Newtonian rheology. Toward the goal of more patient-specific aneurysm CFD, we conclude that attention seems better spent on solution strategy and other likely "first-order" effects (eg, lumen segmentation and choice of flow rates), as opposed to "second-order" effects such as rheology. Copyright © 2016 John Wiley & Sons, Ltd.
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S.Jothimani
2014-08-01
Full Text Available This paper investigates the MHD flow and heat transfer of an electrically conducting non-newtonian power-law fluid over a non-linearly stretching surface along with porous plate in porous medium. The governing equations are reduced to non-linear ordinary differential equations by means of similarity transformations. These equations are then solved numerically with the help ofRunge – Kutta shooting method. The effect of various flow parameters in the form of dimensionless quantities on the flow field are discussed and presented graphically.
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J. Siva Ram Prasad
2016-01-01
Full Text Available We analyzed in this paper the problem of mixed convection along a vertical plate in a non-Newtonian fluid saturated non-Darcy porous medium in the presence of melting and thermal dispersion-radiation effects for aiding and opposing external flows. Similarity solution for the governing equations is obtained for the flow equations in steady state. The equations are numerically solved by using Runge-kutta fourth order method coupled with shooting technique. The effects of melting (M, thermal dispersion (D, radiation (R, magnetic field (MH, viscosity index (n and mixed convection (Ra/Pe on fluid velocity and temperature are examined for aiding and opposing external flows.
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Muhammad Tufail
2016-01-01
Full Text Available The present article examines the flow, heat and mass transfer of a non-Newtonian fluid known as Casson fluid over a stretching surface in the presence of thermal radiations effects. Lie Group analysis is used to reduce the governing partial differential equations into non-linear ordinary differential equations. These equations are then solved by an analytical technique known as Homotopy Analysis Method (HAM. A comprehensive study of the problem is being made for various parameters involving in the equations through tables and graphs.
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M.A. Bosse
2001-03-01
Full Text Available The problem of the effect of Joule heating generation on the hydrodynamic profile and the solute transport found in electrophoretic devices is addressed in this article. The research is focused on the following two problems: The first one is centered around the effect of Joule heating on the hydrodynamic velocity profile and it is referred to as "the carrier fluid problem." The other one is related to the effect of Joule heating on the solute transport inside electrophoretic cells and it is referred to as "the solute problem". The hydrodynamic aspects were studied first to yield the velocity profiles required for analysis of the solute transport problem. The velocity profile obtained in this study is analytical and the results are valid for non-Newtonian fluids carriers. To this end, the power-law model was used to study the effect of the rheology of the material in conjunction with the effect of Joule heating generation inside batch electrophoretic devices. This aspect of the research was then effectively used to study the effect of Joule heating generation on the motion of solutes (such as macromolecules under the influence of non-Newtonian carriers. This aspect of the study was performed using an area-averaging approach that yielded analytical results for the effective diffusivity of the device.
Thandlam, Anil Kumar; Das, Chiranjib; Majumder, Subrata Kumar
2016-08-01
Investigation of wall-liquid mass transfer and heat transfer phenomena with gas-Newtonian and non-Newtonian fluids in vertically helical coil reactor have been reported in this article. Experiments were conducted to investigate the effect of various dynamic and geometric parameters on mass and heat transfer coefficients in the helical coil reactor. The flow pattern-based heat and mass transfer phenomena in the helical coil reactor are highlighted at different operating conditions. The study covered a wide range of geometric parameters such as diameter of the tube (d t ), diameter of the coil (D c ), diameter of the particle (d p ), pitch difference (p/D c ) and concentrations of non-Newtonian liquid. The correlation models for the heat and mass transfer coefficient based on the flow pattern are developed which may be useful in process scale-up of the helical coil reactor for industrial application. The frictional drag coefficient was also estimated and analyzed by mass transfer phenomena based on the electrochemical method.
Jianping; Ping; Lin; Yunlin
2000-07-01
The local overall volumetric gas-liquid mass transfer coefficients at the specified point in a gas-liquid-solid three-phase reversed flow jet loop bioreactor (JLB) with a non-Newtonian fluid was experimentally investigated by a transient gassing-in method. The effects of liquid jet flow rate, gas jet flow rate, particle density, particle diameter, solids loading, nozzle diameter and CMC concentration on the local overall volumetric gas-liquid mass transfer coefficient (K(L)a) profiles were discussed. It was observed that local overall K(L)a profiles in the three-phase reversed flow JLB with non-Newtonian fluid increased with the increase of gas jet flow rate, liquid jet flow rate, particle density and particle diameter, but decreased with the increase of the nozzle diameter and CMC concentration. The presence of solids at a low concentration increased the local overall K(L)a profiles, and the optimum of solids loading for a maximum profile of the local overall K(L)a was found to be 0.18x10(-3)m(3) corresponding to a solids volume fraction, varepsilon(S)=2.8%.
Deyranlou, Amin; Niazmand, Hamid; Sadeghi, Mahmood-Reza
2015-09-18
Low-density lipoprotein (LDL), which is recognized as bad cholesterol, typically has been regarded as a main cause of atherosclerosis. LDL infiltration across arterial wall and subsequent formation of Ox-LDL could lead to atherogenesis. In the present study, combined effects of non-Newtonian fluid behavior and fluid-structure interaction (FSI) on LDL mass transfer inside an artery and through its multilayer arterial wall are examined numerically. Navier-Stokes equations for the blood flow inside the lumen and modified Darcy's model for the power-law fluid through the porous arterial wall are coupled with the equations of mass transfer to describe LDL distributions in various segments of the artery. In addition, the arterial wall is considered as a heterogeneous permeable elastic medium. Thus, elastodynamics equation is invoked to examine effects of different wall elasticity on LDL distribution in the artery. Findings suggest that non-Newtonian behavior of filtrated plasma within the wall enhances LDL accumulation meaningfully. Moreover, results demonstrate that at high blood pressure and due to the wall elasticity, endothelium pores expand, which cause significant variations on endothelium physiological properties in a way that lead to higher LDL accumulation. Additionally, results describe that under hypertension, by increasing angular strain, endothelial junctions especially at leaky sites expand more dramatic for the high elastic model, which in turn causes higher LDL accumulation across the intima layer and elevates atherogenesis risk.
Malkus, David S.
1989-01-01
This project concerned the development of a new fast finite element algorithm to solve flow problems of non-Newtonian fluids such as solutions or melts of polymers. Many constitutive theories for such materials involve single integrals over the deformation history of the particle at the stress evaluation point; examples are the Doi-Edwards and Curtiss-Bird molecular theories and the BKZ family derived from continuum arguments. These theories are believed to be among the most accurate in describing non-Newtonian effects important to polymer process design, effects such as stress relaxation, shear thinning, and normal stress effects. This research developed an optimized version of the algorithm which would run a factor of two faster than the pilot algorithm on scalar machines and would be able to take full advantage of vectorization on machines. Significant progress was made in code vectorization; code enhancement and streamlining; adaptive memory quadrature; model problems for the High Weissenberg Number Problem; exactly incompressible projection; development of multimesh extrapolation procedures; and solution of problems of physical interest. A portable version of the code is in the final stages of benchmarking and testing. It interfaces with the widely used FIDAP fluid dynamics package.
Ramachandra Prasad, V.; Gaffar, S. Abdul; Keshava Reddy, E.; Bég, O. Anwar
2014-07-01
Polymeric enrobing flows are important in industrial manufacturing technology and process systems. Such flows are non-Newtonian. Motivated by such applications, in this article we investigate the nonlinear steady state boundary layer flow, heat, and mass transfer of an incompressible Jefferys non-Newtonian fluid past a vertical porous plate in a non-Darcy porous medium. The transformed conservation equations are solved numerically subject to physically appropriate boundary conditions using a versatile, implicit, Keller-box finite-difference technique. The numerical code is validated with previous studies. The influence of a number of emerging non-dimensional parameters, namely Deborah number (De), Darcy number (Da), Prandtl number (Pr), ratio of relaxation to retardation times (λ), Schmidt number (Sc), Forchheimer parameter (Λ), and dimensionless tangential coordinate (ξ) on velocity, temperature, and concentration evolution in the boundary layer regime are examined in detail. Furthermore, the effects of these parameters on surface heat transfer rate, mass transfer rate, and local skin friction are also investigated. It is found that the boundary layer flow is decelerated with increasing De and Forchheimer parameter, whereas temperature and concentration are elevated. Increasing λ and Da enhances the velocity but reduces the temperature and concentration. The heat transfer rate and mass transfer rates are found to be depressed with increasing De and enhanced with increasing λ. Local skin friction is found to be decreased with a rise in De, whereas it is elevated with increasing λ. An increasing Sc decreases the velocity and concentration but increases temperature.
Thermal stability for a reactive viscous flow in a slab
Okoya, S S
2002-01-01
The paper deals with the effect of dimensionless non - Newtonian coefficient on the thermal stability of a reactive viscous liquid in steady flow between parallel heated plates. It is assumed that the liquid is symmetrically heated and the flow fully developed. Approximate analytical solution is obtained for the velocity of the flow and the criterion for which this solution is valid is determined. After the velocity distribution is known, the temperature distribution may be calculated. Criticality and disappearance of criticality (transition values) are obtained in the following cases: (i) Bimolecular (ii) Arrhenius and (iii) Sensitized temperature dependence. We have observed that nonlinear effect from velocity and temperature fields introduced decaying for the transitional values of the dimensionless central temperature. Other effects of this nonlinearity are reported. We also give results for the plane - Couette flow problem. The results help to enhance understanding of the interplay between Newtonian and ...
Rathod, Maureen L.
Initially 3D FEM simulation of a simplified mixer was used to examine the effect of mixer configuration and operating conditions on dispersive mixing of a non-Newtonian fluid. Horizontal and vertical velocity magnitudes increased with increasing mixer speed, while maximum axial velocity and shear rate were greater with staggered paddles. In contrast, parallel paddles produced an area of efficient dispersive mixing between the center of the paddle and the barrel wall. This study was expanded to encompass the complete nine-paddle mixing section using power-law and Bird-Carreau fluid models. In the center of the mixer, simple shear flow was seen, corresponding with high [special character omitted]. Efficient dispersive mixing appeared near the barrel wall at all flow rates and near the barrel center with parallel paddles. Areas of backflow, improving fluid retention time, occurred with staggered paddles. The Bird-Carreau fluid showed greater influence of paddle motion under the same operating conditions due to the inelastic nature of the fluid. Shear-thinning behavior also resulted in greater maximum shear rate as shearing became easier with decreasing fluid viscosity. Shear rate distributions are frequently calculated, but extension rate calculations have not been made in a complex geometry since Debbaut and Crochet (1988) defined extension rate as the ratio of the third to the second invariant of the strain rate tensor. Extension rate was assumed to be negligible in most studies, but here extension rate is shown to be significant. It is possible to calculate maximum stable bubble diameter from capillary number if shear and extension rates in a flow field are known. Extension rate distributions were calculated for Newtonian and non-Newtonian fluids. High extension and shear rates were found in the intermeshing region. Extension is the major influence on critical capillary number and maximum stable bubble diameter, but when extension rate values are low shear rate has
Institute of Scientific and Technical Information of China (English)
葛雄; 张根广; 颜婷; 王华伟
2011-01-01
There are many differences between the Newtonian fluid and the non-Newtonian fluid, and there is a few or even not teaching apparatus to demonstrate the behavior differences between the Newtonian fluid and the non-Newtonian fluid. To strengthen understanding of the Newtonian fluid and the non-Newtonian fluid, a teaching apparatus to demonstrate the velocity distribution differences in laminar flow between the Newtonian fluid and the non-Newtonian fluid was designed and made based on the flow characteristics differences. The movement behaviors of the Newtonian fluid and the non-Newtonian fluid were displayed by the tracer liquid developed by us. The velocity distribution differences at laminar flow between the Newtonian fluid and the non-Newtonian fluid can be found easily and directly in the demonstration apparatus.%牛顿流体和非牛顿流体存在着较大的差异，有关牛顿流体和非牛顿流体特性差异方面的教学演示仪器还较少，有些还处于空白。为了加强学生对牛顿流体和非牛顿流体的认识，本文根据牛顿流体与非牛顿流体流动特性差异，设计制作了表现牛顿流体和非牛顿流体层流流速分布差异的演示仪器;利用自行研制的示踪液体演示了非牛顿流体和牛顿流体运动过程，直观的展示了牛顿流体与非牛顿流体层流流速分布的差异。
Long waves over a bi-viscous seabed: transverse patterns
Directory of Open Access Journals (Sweden)
J. M. Becker
2002-01-01
Full Text Available The coupled interaction of long standing hydrodynamic waves with a deformable non-Newtonian seabed is examined using a two-layer model for which the upper layer fluid is inviscid and the lower layer is bi-viscous. The two-dimensional response of the system to forcing by a predominantly longitudinal (cross-shore standing wave perturbed by a small transverse (along-shore component is determined. With a constant yield stress in the bi-viscous lower layer, there is little amplification of these transverse per-turbations and the model response typically remains quasi-one-dimensional. However, for a bi-viscous layer with a pressure-dependent yield stress (which represents the effect that the seabed deforms less readily under compression and hence renders the rheology history dependent, the initially small transverse motions are amplified in some parameter regimes and two-dimensional, permanent bedforms are formed in the lower layer. This simple dynamical model is, therefore, able to explain the formation of permanent bedforms with significant cross- and along-shore features by predominantly cross-shore standing wave forcing.
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Macha Madhu
2016-07-01
Full Text Available Magnetohydrodynamic mixed convection boundary layer flow of heat and mass transfer stagnation-point flow of a non-Newtonian power-law nanofluid towards a stretching surface in the presence of thermal radiation is investigated numerically. The non-Newtonian nanofluid model incorporates the effects of Brownian motion and thermophoresis. The basic transport equations are made dimensionless first and the coupled non linear differential equations are solved by finite element method. The numerical calculations for velocity, temperature and concentration profiles for different values of the physical parameters presented graphically and discussed. As well as for skin friction coefficient, local Nusselt and Sherwood numbers exhibited and examined.
Study on flow field characteristics of Non-Newtonian fluid in hydrocyclone%非牛顿流体在分离旋流器内流场特性研究
Institute of Scientific and Technical Information of China (English)
艾志久; 汪利霞; 刘晓明
2011-01-01
运用计算流体动力学(CFD)方法分别对旋流器内非牛顿流体与牛顿流体的流场分别进行数值模拟.分析采用RSM(SSG)雷诺应力模型,得到非牛顿流体与牛顿流体的速度场、压力场以及表观粘度分布规律.研究结果揭示了非牛顿流体在分离旋流器内的流场特性:由于受非牛顿流体表现粘度随剪切速率变化的影响,在同一位置处,非牛顿流体的静压力、轴向速度以及径向速度都大于牛顿流体,而切向速度小于牛顿流体；同时,旋流器内非牛顿流体的零轴速包络面(LZVV)比牛顿流体更加靠近器壁,这导致旋流器中非牛顿流体在同等条件下比牛顿流体的分离效率低；以上这些特性为进一步充分认识用于分离非牛顿流体的旋流器分离机理提供依据.%The method of Computational Fluid Dynamics was used to simulate the fluid field of the non-Newtonian fluid and the Newtonian fluid in the hydrocyclone. The Analysis was operated by reynolds stress model and obtained the velocity field,the pressure field as well as the apparent viscosity distribution of non-Newtonian fluid and the Newtonian fluid. The results revealed the Flow field Characteristics of the non-Newtonian fluids in the hydrocyclone: In the same position .with the effect of apparent viscosity changes of non-Newtonian fluid,the static pressure,the axial velocity as well as radial velocity of non-Newtonian fluid were bigger than Newtonian fluid's.and the radial velocity was less; The locus of zero vertical velocity of hydrocyclone of non-Newtonian was closer to the wall;these characteristics led to lower separation efficiency of non-Newtonian fluid than Newtonian fluid's under the same conditions. This study provided the evidence for new understand of the separation mechanism of non-Newtonian fluid.
Viscous-elastic dynamics of power-law fluids within an elastic cylinder
Boyko, Evgeniy; Bercovici, Moran; Gat, Amir D.
2017-07-01
In a wide range of applications, microfluidic channels are implemented in soft substrates. In such configurations, where fluidic inertia and compressibility are negligible, the propagation of fluids in channels is governed by a balance between fluid viscosity and elasticity of the surrounding solid. The viscous-elastic interactions between elastic substrates and non-Newtonian fluids are particularly of interest due to the dependence of viscosity on the state of the system. In this work, we study the fluid-structure interaction dynamics between an incompressible non-Newtonian fluid and a slender linearly elastic cylinder under the creeping flow regime. Considering power-law fluids and applying the thin shell approximation for the elastic cylinder, we obtain a nonhomogeneous p-Laplacian equation governing the viscous-elastic dynamics. We present exact solutions for the pressure and deformation fields for various initial and boundary conditions for both shear-thinning and shear-thickening fluids. We show that in contrast to Stokes' problem where a compactly supported front is obtained for shear-thickening fluids, here the role of viscosity is inversed and such fronts are obtained for shear-thinning fluids. Furthermore, we demonstrate that for the case of a step in inlet pressure, the propagation rate of the front has a tn/n +1 dependence on time (t ), suggesting the ability to indirectly measure the power-law index (n ) of shear-thinning liquids through measurements of elastic deformation.
Najjari, Mohammad Reza; Plesniak, Michael W.
2016-06-01
Steady flow and physiological pulsatile flow in a rigid 180° curved tube are investigated using particle image velocimetry. A non-Newtonian blood-analog fluid is used, and in-plane primary and secondary velocity fields are measured. A vortex detection scheme ( d 2-method) is applied to distinguish vortical structures. In the pulsatile flow case, four different vortex types are observed in secondary flow: deformed-Dean, Dean, Wall and Lyne vortices. Investigation of secondary flow in multiple cross sections suggests the existence of vortex tubes. These structures split and merge over time during the deceleration phase and in space as flow progresses along the 180° curved tube. The primary velocity data for steady flow conditions reveal additional vortices rotating in a direction opposite to Dean vortices—similar to structures observed in pulsatile flow—if the Dean number is sufficiently high.
Energy Technology Data Exchange (ETDEWEB)
Hady, F. M.; Ibrahim, F. S. [Assiut University, Assiut (Egypt); Abdel-Gaied, S. M.; Eid, M. R. [Assiut University, The New Valley (Egypt)
2011-08-15
The effect of yield stress on the free convective heat transfer of dilute liquid suspensions of nanofluids flowing on a vertical plate saturated in porous medium under laminar conditions is investigated considering the nanofluid obeys the mathematical model of power-law. The model used for non-Newtonian nanofluid incorporates the effects of Brownian motion and thermophoresis. The governing boundary- layer equations are cast into dimensionless system which is solved numerically using a deferred correction technique and Newton iteration. This solution depends on yield stress parameter {Omega}, a power-law index n, Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. Analyses of the results found that the reduced Nusselt and Sherwood numbers are decreasing functions of the higher yield stress parameter for each dimensionless numbers, n and Le, except the reduced Sherwood number is an increasing function of higher Nb for different values of yield stress parameter.
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SUBBARAO ANNASAGARAM
2016-01-01
Full Text Available The laminar boundary layer flow and heat transfer of Casson non-Newtonian fluid from an inclined (solar collector plate in the presence of thermal and hydrodynamic slip conditions is analysed. The inclined plate surface is maintained at a constant temperature. The boundary layer conservation equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller-box finite-difference scheme. Increasing velocity slip induces acceleration in the flow near the inclined plate surface. Increasing velocity slip consistently enhances temperatures throughout the boundary layer regime. An increase in thermal slip parameter strongly decelerates the flow and also reduces temperatures in the boundary layer regime. An increase in Casson rheological parameter acts to elevate considerably the velocity and this effect is pronounced at higher values of tangential coordinate. Temperatures are however very slightly decreased with increasing values of Casson rheological parameter.
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Muhammad Mubashir Bhatti
2017-01-01
Full Text Available In this article, entropy generation on non-Newtonian Eyring-Powell nanofluid has been analysed through a permeable stretching sheet. The governing flow problem is based on linear momentum, thermal energy, and nanoparticle concentration equation which are simplified with the help of similarity transformation variables. The resulting coupled nonlinear ordinary differential equations are solved numerically with the help of Successive Linearization method (SLM and Chebyshev Spectral collocation method. The novel characteristics of all the physical parameters are discussed with the help of graphs and tables. The expression for local Nusselt number and local Sherwood number is also taken into account. It is observed that velocity profile increases due to the greater influence of suction parameter. Moreover, Brownian motion and thermophoresis parameter significantly enhance the temperature profile, however Brownian motion parameter shows converse behaviour on nanoparticle concentration profile. Entropy profile acts as an increasing function of all the pertinent parameters.
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J. L. Vieira Neto
2014-12-01
Full Text Available Helical flow in an annular space occurs during oil drilling operations. The correct prediction of flow of drilling fluid in an annular space between the wellbore wall and the drill pipe is essential to determine the variation in fluid pressure within the wellbore. This paper presents experimental and CFD simulation results of the pressure drop in the flow of non-Newtonian fluids through a concentric annular section and another section with fixed eccentricity (E = 0.75, using aqueous solutions of two distinct polymers (Xanthan Gum and Carboxymethylcellulose. The hydrodynamic behavior in this annular system was analyzed based on the experimental and CFD results, providing important information such as the formation of zones with preferential flows and stagnation regions.
Tip Velocity of Viscous Fingers in Shear-Thinning Fluids in a Hele-Shaw Cell
Yamamoto, Takehiro; Kimoto, Ryusuke; Mori, Noriyasu
Viscous fingering in non-Newtonian fluids in a rectangular Hele-Shaw cell was investigated. The cell was filled with a 0.5 or 1.0wt% aqueous solution of carboxymethylcellulose (CMC), a shear-thinning fluid. Air was injected into the cell and the growth of viscous fingers was observed. The velocity of finger tip was characterized by the pressure gradient. A modified Darcy law was able to describe the characteristics of the tip velocity that the growth rate of the tip velocity increased with increasing pressure gradient in the CMC solutions. The prediction of tip velocity with the modified Darcy law indicated that an effective pressure gradient near the tip was larger than the average pressure gradient between the finger tip and the cell exit and that the rate of increase depended on the cell gap width.
MHD Flow and Heat Transfer Analysis in the Wire Coating Process Using Elastic-Viscous
Directory of Open Access Journals (Sweden)
Zeeshan Khan
2017-01-01
Full Text Available The most important plastic resins used for wire coating are polyvinyl chloride (PVC, nylon, polysulfone, and low-/high-density polyethylene (LDPE/HDPE. In this article, the coating process is performed using elastic-viscous fluid as a coating material for wire coating in a pressure type coating die. The elastic-viscous fluid is electrically conducted in the presence of an applied magnetic field. The governing non-linear equations are modeled and then solved analytically by utilizing an Adomian decomposition method (ADM. The convergence of the series solution is established. The results are also verified by Optimal Homotopy Asymptotic Method (OHAM. The effect of different emerging parameters such as non-Newtonian parameters α and β, magnetic parameter Mand the Brinkman number Br on solutions (velocity and temperature profiles are discussed through several graphs. Additionally, the current results are compared with published work already available.
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.
Choi, Jong Han; Lee, Sangmook; Lee, Jae Wook
2017-02-01
The rheological properties of polymer composites highly filled with different filler materials were examined using a stress-controlled rheometer with a parallel-plate configuration, for particle characterization of the filler materials in plastic (polymer) bonded explosive (PBX). Ethylene vinyl acetate (EVA) with dioctyl adipate (DOA) was used as the matrix phase, which was shown to exhibit Newtonian-like behavior. The dispersed phase consisted of one of two energetic materials, i.e., explosive cyclotrimethylene trinitramine (RDX) or cyclotetramethylene tetranitramine (HMX), or a simulant (Dechlorane) in a bimodal size distribution. Before the test, preshearing was conducted to identify the initial condition of each sample. All examined filled polymer specimens exhibited yield stress and shear-thinning behavior over the investigated frequency range. The complex viscosity dependence on the dynamic oscillation frequency was also fitted using an appropriate rheological model, suggesting the model parameters. Furthermore, the temperature dependency of the different filler particle types was determined for different filler volume fractions. These comparative studies revealed the influence of the particle characteristics on the rheological properties of the filled polymer.
Energy Technology Data Exchange (ETDEWEB)
Guerrero, H; Charles Crawford, C; Mark Fowley, M
2008-08-07
Gas holdup tests were performed in bench-scale and small-scale mechanically-agitated mixing systems at the Savannah River National Laboratory (SRNL) for a simulant of waste from the Hanford Tank 241-AZ-101. These featured additions of DOW Corning Q2-3183A anti-foam agent. Results indicated that this anti-foam agent (AFA) increased gas holdup in the waste simulant by about a factor of four and, counter-intuitively, that the holdup increased as the non-newtonian simulant shear strength decreased (apparent viscosity decreased). Such results raised the potential of increased flammable gas retention in Hanford Waste Treatment and Immobilization Plant (WTP) vessels mixed by air sparging and pulse-jet mixers (PJMs) during a Design Basis Event (DBE). Additional testing was performed to determine the effects of simulant properties, composition of alternate AFAs, and presence of trace noble metals. Key results are that: (1) Increased gas holdup resulting from addition of Q2-3183A is due to a decrease in surface tension that supports small bubbles which have low rise velocities. (2) Dow Corning 1520-US AFA shows it to be a viable replacement to Dow Corning Q2-3183A AFA. This alternative AFA, however, requires significantly higher dosage for the same anti-foam function. (3) Addition of noble metals to the AZ-101 waste simulant does not produce a catalytic gas retention effect with the AFA.
Directory of Open Access Journals (Sweden)
Mehrvar M.
2013-05-01
Full Text Available The identification of non-ideal flows in a continuous-flow mixing of non-Newtonian fluids is a challenging task for various chemical industries: plastic manufacturing, water and wastewater treatment, and pulp and paper manufacturing. Non-ideal flows such as channelling, recirculation, and dead zones significantly affect the performance of continuous-flow mixing systems. Therefore, the main objective of this paper was to develop an identification protocol to measure non-ideal flows in the continuous-flow mixing system. The extent of non-ideal flows was quantified using a dynamic model that incorporated channelling, recirculation, and dead volume in the mixing vessel. To estimate the dynamic model parameters, the system was excited using a frequency-modulated random binary input by injecting the saline solution (as a tracer into the fresh feed stream prior to being pumped into the mixing vessel. The injection of the tracer was controlled by a computer-controlled on-off solenoid valve. Using the trace technique, the extent of channelling and the effective mixed volume were successfully determined and used as mixing quality criteria. Such identification procedures can be applied at various areas of chemical engineering in order to improve the mixing quality.
Almazmumy, Mariam; Ebaid, Abdelhalim
2017-08-01
In this article, the flow and heat transfer of a non-Newtonian nanofluid between two coaxial cylinders through a porous medium has been investigated. The velocity, temperature, and nanoparticles concentration of the present mathematical model are governed by a system of nonlinear ordinary differential equations. The objective of this article is to obtain new exact solutions for the temperature and the nanoparticles concentration and, therefore, compare them with the previous approximate results in the literature. Moreover, the velocity equation has been numerically solved. The effects of the pressure gradient, thermophoresis, third-grade, Brownian motion, and porosity parameters on the included phenomena have been discussed through several tables and plots. It is found that the velocity profile is increased by increasing the pressure gradient parameter, thermophoresis parameter (slightly), third-grade parameter, and Brownian motion parameter (slightly); however, it decreases with an increase in the porosity parameter and viscosity power index. In addition, the temperature and the nanoparticles concentration reduce with the strengthen of the Brownian motion parameter, while they increase by increasing the thermophoresis parameter. Furthermore, the numerical solution and the physical interpretation in the literature for the same problem have been validated with the current exact analysis, where many remarkable differences and errors have been concluded. Therefore, the suggested analysis may be recommended with high trust for similar problems.
Matthys, E. F.
The convective heat transfer, friction, and rheological properties of various types of nonNewtonian fluid in circular tube flows were investigated. If an apparent Reynolds number is used and if the temperature and degradation effects are properly taken into account, the reduced turbulent friction and heat transfer results, respectively, are then shown to be well correlated by the same expressions for different fluids, regardless of the nature of the fluids and whether they are shear-thinning or shear-thickening. This representation can also separate the reductions in turbulent heat transfer and friction that are induced by viscoelasticity from those induced by pseudoplasticity. Polyacrylamide solutions inducing asymptotic and intermediate drag reduction regimes were investigated over a broad range of Reynolds numbers. A kerosene-based antimisting polymer solution was also studied. Suspensions of bentonite of various concentrations were investigated in laminar and turbulent regimes, and the results for fully developed and entrance flows were well correlated by Newtonian relationships when an adequate wall viscosity concept was used.
Directory of Open Access Journals (Sweden)
Rahman Abdel-Gamal M.
2013-01-01
Full Text Available The unsteady flow and heat transfer in an incompressible laminar, electrically conducting and non-Newtonian fluid over a non-isothermal stretching sheet with the variation in the viscosity and thermal conductivity in a porous medium by the influence of an external transverse magnetic field have been obtained and studied numerically. By using similarity analysis the governing differential equations are transformed into a set of non-linear coupled ordinary differential equations which are solved numerically. Numerical results were presented for velocity and temperature profiles for different parameters of the problem as power law parameter, unsteadiness parameter, radiation parameter, magnetic field parameter, porous medium parameter, temperature buoyancy parameter, Prandtl parameter, modified Eckert parameter, Joule heating parameter , heat source/sink parameter and others. A comparison with previously published work has been carried out and the results are found to be in good agreement. Also the effects of the pertinent parameters on the skin friction and the rate of heat transfer are obtained and discussed numerically and illustrated graphically.
Shintaku, Hirofumi; Yonemura, Tsubasa; Tsuru, Kazuaki; Isoyama, Takashi; Yambe, Tomoyuki; Kawano, Satoyuki
In this study, we construct an experimental apparatus for a prototype artificial heart and lung (AHL) by installing hollow fibers into the cylindrical tube of the vibrating flow pump (VFP). The oxygenation characteristics are investigated both by experiments using bovine blood and by numerical analyses based on the computational fluid dynamics. The analyses are carried out at the Reynolds numbers Re ranged from O(1) to O(103), which are determined based on the experimental conditions. The blood flow and the diffusion of oxygen gas are analyzed based on the Newtonian/non-Newtonian, unsteady, incompressible and axisymmetric Navier-Stokes equations, and the advection-diffusion equation. The results show that the oxygenation rate increases in proportion to Re1/3, where the phenomenon corresponds to the decreasing thickness of the concentration boundary layer with Re. Although the effects of the vibrating flow and the rheology of the blood are clearly appeared on the velocity field, their effects on the gas exchange are relatively small at the ranges of prescribed Reynolds numbers. Furthermore, the numerical results in terms of the oxygenation rate are compared with the experimental ones. The basic design data of VFP were accumulated for the development of AHL in the clinical applications.
Patel, D.; Ein-Mozaffari, F.; Mehrvar, M.
2013-05-01
The identification of non-ideal flows in a continuous-flow mixing of non-Newtonian fluids is a challenging task for various chemical industries: plastic manufacturing, water and wastewater treatment, and pulp and paper manufacturing. Non-ideal flows such as channelling, recirculation, and dead zones significantly affect the performance of continuous-flow mixing systems. Therefore, the main objective of this paper was to develop an identification protocol to measure non-ideal flows in the continuous-flow mixing system. The extent of non-ideal flows was quantified using a dynamic model that incorporated channelling, recirculation, and dead volume in the mixing vessel. To estimate the dynamic model parameters, the system was excited using a frequency-modulated random binary input by injecting the saline solution (as a tracer) into the fresh feed stream prior to being pumped into the mixing vessel. The injection of the tracer was controlled by a computer-controlled on-off solenoid valve. Using the trace technique, the extent of channelling and the effective mixed volume were successfully determined and used as mixing quality criteria. Such identification procedures can be applied at various areas of chemical engineering in order to improve the mixing quality.
Investigating viscous damping using a webcam
Shamim, Sohaib; Anwar, Muhammad Sabieh
2011-01-01
We describe an experiment involving a mass oscillating in a viscous fluid and analyze viscous damping of harmonic motion. The mechanical oscillator is tracked using a simple webcam and an image processing algorithm records the position of the geometrical center as a function of time. Interesting information can be extracted from the displacement-time graphs, in particular for the underdamped case. For example, we use these oscillations to determine the viscosity of the fluid. Our mean value of 1.08 \\pm 0.07 mPa s for distilled water is in good agreement with the accepted value at 20\\circC. This experiment has been successfully employed in the freshman lab setting.
Directory of Open Access Journals (Sweden)
T. M. Ajayi
2017-01-01
Full Text Available The problem of a non-Newtonian fluid flow past an upper surface of an object that is neither a perfect horizontal/vertical nor inclined/cone in which dissipation of energy is associated with temperature-dependent plastic dynamic viscosity is considered. An attempt has been made to focus on the case of two-dimensional Casson fluid flow over a horizontal melting surface embedded in a thermally stratified medium. Since the viscosity of the non-Newtonian fluid tends to take energy from the motion (kinetic energy and transform it into internal energy, the viscous dissipation term is accommodated in the energy equation. Due to the existence of internal space-dependent heat source; plastic dynamic viscosity and thermal conductivity of the non-Newtonian fluid are assumed to vary linearly with temperature. Based on the boundary layer assumptions, suitable similarity variables are applied to nondimensionalized, parameterized and reduce the governing partial differential equations into a coupled ordinary differential equations. These equations along with the boundary conditions are solved numerically using the shooting method together with the Runge-Kutta technique. The effects of pertinent parameters are established. A significant increases in Rex1/2Cfx is guaranteed with St when magnitude of β is large. Rex1/2Cfx decreases with Ec and m.
Analytical solution for the lubrication force between two spheres in a bi-viscous fluid
Vázquez-Quesada, A.; Ellero, M.
2016-07-01
An analytical solution for the calculation of the normal lubrication force acting between two moving spheres embedded in a shear-thinning fluid represented by a bi-viscous model is provided. The resulting force between the suspended spheres exhibits a consistent transition between the Newtonian constant-viscosity limits and it reduces to the well-known standard Newtonian lubrication theory for viscosity-ratio approaching one. Effects of several physical parameters of the theory are analyzed under relevant physical conditions, i.e., for a prototypical case of two non-colloidal spheres immersed in a non-Newtonian fluid with rheology parameterized by a bi-viscosity model. Topological results for high/low-viscosity regions in the gap between spheres are also analyzed in detail showing a rich phenomenology. The presented model enables the extension of lubrication dynamics for suspensions interacting with non-Newtonian matrices and provides a clean theoretical framework for new numerical computations of flow of dense complex particulate systems.
Foam rheology: A model of viscous effects in shear flow
Kraynik, Andrew M.; Reinelt, Douglas A.
Foams consisting of gas bubbles dispersed in a continuous network of thin liquid films display a remarkable range of rheological characteristics that include a finite shear modulus, yield stress, non-Newtonian viscosity, and slip at the wall. Progress in developing micromechanical theories to describe foam rheology has depended upon two-dimensional models, which in most cases are assumed to have perfectly ordered structure. Princen accounted for surface tension and geometrical effects, and analyzed the nonlinear elastic response of a spatially periodic foam in simple shear. His analysis has been extended to account for more general deformations. Khan and Armstrong and Kraynik and Hansen have proposed ad hoc models for viscous effects in foam rheology. Their models capture numerous qualitative phenomena but incorporate relaxation mechanisms based upon overly simplified assumptions of liquid flow in the thin films. Mysels, Shinoda, and Frankel considered soap films with interfaces that are inextensible due to the presence of surfactants. They analyzed the primary flow that occurs when such films are slowly withdrawn from or recede into essentially static junction regions such as the Plateau borders in a foam. Adopting this mechanism, Schwartz and Princen considered small periodic deformations of a foam and calculated the energy dissipation due to viscous flow in the thin films. In the following, we also adopt the basic interfacial and viscous mechanisms introduced by Mysels et al. and analyze simple shearing deformations of finite amplitude. The configuration and effective stress of the foam are determined. Under these deformation conditions, the foam is a nonlinear viscoelastic material. Results for the uniform expansion of a foam are also presented.
Lubricated viscous gravity currents
Kowal, Katarzyna N.; Worster, M. Grae
2015-01-01
This is the author accepted manuscript. The final version is available via CUP at http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9553100&fileId=S0022112015000300. We present a theoretical and experimental study of viscous gravity currents lubricated by another viscous fluid from below. We use lubrication theory to model both layers as Newtonian fluids spreading under their own weight in two-dimensional and axisymmetric settings over a smooth rigid horizontal surfa...
Energy and Transmissibility in Nonlinear Viscous Base Isolators
Markou, Athanasios A.; Manolis, George D.
2016-09-01
High damping rubber bearings (HDRB) are the most commonly used base isolators in buildings and are often combined with other systems, such as sliding bearings. Their mechanical behaviour is highly nonlinear and dependent on a number of factors. At first, a physical process is suggested here to explain the empirical formula introduced by J.M. Kelly in 1991, where the dissipated energy of a HDRB under cyclic testing, at constant frequency, is proportional to the amplitude of the shear strain, raised to a power of approximately 1.50. This physical process is best described by non-Newtonian fluid behaviour, originally developed by F.H. Norton in 1929 to describe creep in steel at high-temperatures. The constitutive model used includes a viscous term, that depends on the absolute value of the velocity, raised to a non-integer power. The identification of a three parameter Kelvin model, the simplest possible system with nonlinear viscosity, is also suggested here. Furthermore, a more advanced model with variable damping coefficient is implemented to better model in this complex mechanical process. Next, the assumption of strain-rate dependence in their rubber layers under cyclic loading is examined in order to best interpret experimental results on the transmission of motion between the upper and lower surfaces of HDRB. More specifically, the stress-relaxation phenomenon observed with time in HRDB can be reproduced numerically, only if the constitutive model includes a viscous term, that depends on the absolute value of the velocity raised to a non-integer power, i. e., the Norton fluid previously mentioned. Thus, it becomes possible to compute the displacement transmissibility function between the top and bottom surfaces of HDRB base isolator systems and to draw engineering-type conclusions, relevant to their design under time-harmonic loads.
Viscous, Resistive Magnetorotational Modes
Pessah, Martin E
2008-01-01
We carry out a comprehensive analysis of the behavior of the magnetorotational instability (MRI) in viscous, resistive plasmas. We find exact, non-linear solutions of the non-ideal magnetohydrodynamic (MHD) equations describing the local dynamics of an incompressible, differentially rotating background threaded by a vertical magnetic field when disturbances with wavenumbers perpendicular to the shear are considered. We provide a geometrical description of these viscous, resistive MRI modes and show how their physical structure is modified as a function of the Reynolds and magnetic Reynolds numbers. We demonstrate that when finite dissipative effects are considered, velocity and magnetic field disturbances are no longer orthogonal (as it is the case in the ideal MHD limit) unless the magnetic Prandtl number is unity. We generalize previous results found in the ideal limit and show that a series of key properties of the mean Reynolds and Maxwell stresses also hold for the viscous, resistive MRI. In particular, ...
Wormholes in viscous cosmology
Wang, Deng
2016-01-01
We study the wormhole spacetime configurations in bulk viscosity cosmology. Considering three classes of viscous models, i.e., bulk viscosity as a function of Hubble parameter $H$, temperature $T$ and dark energy density $\\rho$, respectively, we obtain nine wormhole solutions. Through the analysis for the anisotropic solutions, we conclude that, to some extent, these three classes of viscous models have very high degeneracy with each other. Subsequently, without the loss of generality, to investigate the traversabilities, energy conditions and stability for the wormhole solution, we study the wormhole solution of the constant redshift function of the viscous $\\omega$CDM model with a constant bulk viscosity coefficient. We obtain the following conclusions: the value of traversal velocity decreases for decreasing bulk viscosity, and the traversal velocity for a traveler depends on not only the wormhole geometry but also the effects of cosmological background evolution; the null energy condition will be violated...
Numerical Simulations of Viscous Accretion Flow around Black Holes
Lee, Seong-Jae; Chattopadhyay, Indranil; Kumar, Rajiv; Hyung, Siek; Ryu, Dongsu
2016-06-01
We present shocked viscous accretion flow onto a black hole in a two dimensional cylindrical geometry, where initial conditions were chosen from analytical solutions. The simulation code used the Lagrangian Total Variation Diminishing (LTVD) and remap routine, which enabled us to attain high accuracy in capturing shocks and to handle the angular momentum distribution correctly. The steady state shocked solution in the inviscid, as well as in the viscous regime, matched theoretical predictions well, but increasing viscosity renders the accretion shock unstable. Large amplitude shock oscillation is accompanied by intermittent, transient inner multiple shocks. Such oscillation of the inner part of disk is interpreted as the source of QPO in hard X-rays observed in microquasars; and strong shock oscillation induces strong episodic jet emission. The periodicity of jets and shock oscillation are similar. Our simulation shows that the jets for higher viscosity parameter are evidently stronger and faster than that for lower viscosity.
Viscous, Resistive Magnetorotational Modes
DEFF Research Database (Denmark)
Pessah, Martin Elias; Chan, Chi-kwan
2008-01-01
We carry out a comprehensive analysis of the behavior of the magnetorotational instability (MRI) in viscous, resistive plasmas. We find exact, non-linear solutions of the non-ideal magnetohydrodynamic (MHD) equations describing the local dynamics of an incompressible, differentially rotating...
Domínguez-García, P; Jeney, Sylvia
2016-01-01
We provide a detailed study of the interplay between the different interactions which appear in the Brownian motion of a micronsized sphere immersed in a viscoelastic fluid measured with optical trapping interferometry. To explore a wide range of viscous, elastic and optical forces, we analyze two different viscoelastic solutions at various concentrations, which provide a dynamic polymeric structure surrounding the Brownian sphere. Our experiments show that, depending of the fluid, optical forces, even if small, slightly modify the complex modulus at low frequencies. Based on our findings, we propose an alternative methodology to calibrate this kind of experimental set-up when non-Newtonian fluids are used. Understanding the influence of the optical potential is essential for a correct interpretation of the mechanical properties obtained by optically-trapped probe-based studies of biomaterials and living matter.
Domínguez-García, P.; Forró, László; Jeney, Sylvia
2016-10-01
We provide a detailed study of the interplay between the different interactions which appear in the Brownian motion of a micronsized sphere immersed in a viscoelastic fluid measured with optical trapping interferometry. To explore a wide range of viscous, elastic, and optical forces, we analyze two different viscoelastic solutions at various concentrations, which provide a dynamic polymeric structure surrounding the Brownian sphere. Our experiments show that, depending on the fluid, optical forces, even if small, slightly modify the complex modulus at low frequencies. Based on our findings, we propose an alternative methodology to calibrate this kind of experimental set-up when non-Newtonian fluids are used. Understanding the influence of the optical potential is essential for a correct interpretation of the mechanical properties obtained by optically-trapped probe-based studies of biomaterials and living matter.
Pinch and swell structures: evidence for brittle-viscous behaviour in the middle crust
Directory of Open Access Journals (Sweden)
R. Gardner
2015-04-01
Full Text Available The flow properties of middle to lower crustal rocks are commonly represented by viscous flow. However, examples of pinch and swell structures found in a mid-crustal high strain zone at St. Anne Point (Fiordland, New Zealand suggest pinch and swell structures are initiated by brittle failure of the more competent layer in conjunction with material softening. On this basis we develop a flexible numerical model using brittle-viscous flow where Mohr–Coulomb failure is utilised to initiate pinch and swell structure development. Results show that pinch and swell structures develop in a competent layer in both Newtonian and non-Newtonian flow provided the competent layer has enough viscosity contrast and initially fails brittlely. The degree of material softening after initial failure is shown to impact pinch and swell characteristics with high rates of material softening causing the formation of thick necks between swells by limiting the successful localisation of strain. The flow regime and yielding characteristics of the matrix do not impact pinch and swell structure formation itself, so long as the matrix is less competent. To aid analysis of the structures and help derive the flow properties of rocks in the field, we define three stages of pinch and swell development and offer suggestions for measurements to be made in the field. Our study suggests that Mohr–Coulomb behaviour combined with viscous flow is an appropriate way to represent the heterogeneous rocks of the middle to lower crust. This type of mid-crustal rheological behaviour has significant influence on the localization of strain at all scales. For example, inclusion of Mohr–Coulomb brittle failure with viscous flow in just some mid-crustal layers within a crustal scale model will result in strain localisation throughout the whole crustal section allowing the development of through-going high strain structures from the upper crust into the middle and lower crust. This
Phase Distribution of Nitrogen/Non-Newtonian Flow at Micro-T-Junction%T形微通道内氮气/非牛顿流体两相流相分配
Institute of Scientific and Technical Information of China (English)
周云龙; 刘博; 孙科
2013-01-01
以氮气作为气相工质,以纯水和浓度分别为0.10wt％、0.25wt％、0.50wt％的PAAm水溶液分别为液相工质,在当量直径为178μm的T形微通道内进行气液两相流相分配的实验.实验结果表明:非牛顿流体的性质对两相流相分配特性有着重要的影响.当液体的有效黏度增加时,弹状流和环状流的液相采出分率增加.通过对弹状流与环状流两种流型的对比,发现环状流的液相采出分率受非牛顿流体性质影响较大,而弹状流受其影响较小.%With air as the gas test fluid and both pure water and PAAm aqueous solution with 0.01wt％,0.25wt％ and 0.50wt％ as the test fluid,an experimental investigation into phase distribution of gas-liquid flow through a T-junction with 178μm hydraulic diameter was conducted.The experimental results show that the property of non-Newtonian fluid in micro-T-junction can influence the phase distribution,and the decrease in liquid effective viscosity makes liquid' s taking off of both slug and annular flow reduced.Comparing the flow pattern of slug and annular flow shows that the property of non-Newtonian fluid can influence liquid' s taking-off much of the annular flow and does little on that of slug flow.
Experimental study of highly viscous impinging jets
Energy Technology Data Exchange (ETDEWEB)
Gomon, M. [Univ. of Texas, Austin, TX (United States). Dept. of Mechanical Engineering
1998-12-01
The objective of this research is to study the behavior of highly viscous gravity-driven jets filling a container. Matters of interest are the formation of voids in the fluid pool during the filling process and the unstable behavior of the fluid in the landing region which manifests itself as an oscillating motion. The working fluids used in this research are intended to simulate the flow behavior of molten glass. Qualitative and quantitative results are obtained in a parametric study. The fraction of voids present in the fluid pool after the filling of the container is measured for different parameter values of viscosity and mass flow rate. Likewise, frequencies of the oscillating jet are measured. Results are inconclusive with regard to a correlation between parameter settings and void fractions. As for frequencies, power law correlations are established.
Marston, Jeremy
2010-05-21
Experiments were performed to observe the motion of a solid sphere approaching a solid wall through a thin layer of a viscous liquid. We focus mainly on cases where the ratio of the film thickness, ℘, to the sphere diameter, D, is in the range 0.03 ℘viscous forces, is below a critical level Stc so that the spheres do not rebound and escape from the liquid layer. This provides us with the scope to verify the force acting on the sphere, derived from lubrication theory. Using high-speed video imaging we show, for the first time, that the equations of motion based on the lubrication approximation correctly describe the deceleration of the sphere when St < Stc. Furthermore, we show that the penetration depth at which the sphere motion is first arrested by the viscous force, which decreases with increasing Stokes number, matches well with theoretical predictions. An example for a shear-thinning liquid is also presented, showing that this simple set-up may be used to deduce the short-time dynamical behaviour of non-Newtonian liquids. © 2010 Cambridge University Press.
Bouteraa, Mondher; Nouar, Chérif
2015-12-01
Finite-amplitude thermal convection in a shear-thinning fluid layer between two horizontal plates of finite thermal conductivity is considered. Weakly nonlinear analysis is adopted as a first approach to investigate nonlinear effects. The rheological behavior of the fluid is described by the Carreau model. As a first step, the critical conditions for the onset of convection are computed as a function of the ratio ξ of the thermal conductivity of the plates to the thermal conductivity of the fluid. In agreement with the literature, the critical Rayleigh number Ra(c) and the critical wave number k(c) decrease from 1708 to 720 and from 3.11 to 0, when ξ decreases from infinity to zero. In the second step, the critical value α(c) of the shear-thinning degree above which the bifurcation becomes subcritical is determined. It is shown that α(c) increases with decreasing ξ. The stability of rolls and squares is then investigated as a function of ξ and the rheological parameters. The limit value ξ(c), below which squares are stable, decreases with increasing shear-thinning effects. This is related to the fact that shear-thinning effects increase the nonlinear interactions between sets of rolls that constitute the square patterns [M. Bouteraa et al., J. Fluid Mech. 767, 696 (2015)]. For a significant deviation from the critical conditions, nonlinear convection terms and nonlinear viscous terms become stronger, leading to a further diminution of ξ(c). The dependency of the heat transfer on ξ and the rheological parameters is reported. It is consistent with the maximum heat transfer principle. Finally, the flow structure and the viscosity field are represented for weakly and highly conducting plates.
Acoustics waves and oscillations
Sen, S.N.
2013-01-01
Parameters of acoustics presented in a logical and lucid style Physical principles discussed with mathematical formulations Importance of ultrasonic waves highlighted Dispersion of ultrasonic waves in viscous liquids explained This book presents the theory of waves and oscillations and various applications of acoustics in a logical and simple form. The physical principles have been explained with necessary mathematical formulation and supported by experimental layout wherever possible. Incorporating the classical view point all aspects of acoustic waves and oscillations have been discussed together with detailed elaboration of modern technological applications of sound. A separate chapter on ultrasonics emphasizes the importance of this branch of science in fundamental and applied research. In this edition a new chapter ''Hypersonic Velocity in Viscous Liquids as revealed from Brillouin Spectra'' has been added. The book is expected to present to its readers a comprehensive presentation of the subject matter...
Mezzasalma, Stefano A.
2000-08-01
quite satisfactory in all cases here examined. It is then suggested that the viscous character of a liquid can be described in terms of a coupling between Brownian diffusion and phonon wave motion.
Langlois, William E
2014-01-01
Leonardo wrote, 'Mechanics is the paradise of the mathematical sciences, because by means of it one comes to the fruits of mathematics' ; replace 'Mechanics' by 'Fluid mechanics' and here we are." - from the Preface to the Second Edition Although the exponential growth of computer power has advanced the importance of simulations and visualization tools for elaborating new models, designs and technologies, the discipline of fluid mechanics is still large, and turbulence in flows remains a challenging problem in classical physics. Like its predecessor, the revised and expanded Second Edition of this book addresses the basic principles of fluid mechanics and solves fluid flow problems where viscous effects are the dominant physical phenomena. Much progress has occurred in the nearly half a century that has passed since the edition of 1964. As predicted, aspects of hydrodynamics once considered offbeat have risen to importance. For example, the authors have worked on problems where variations in viscosity a...
Chakrabarti, Brato
2015-01-01
This work explores a simple model of a slender, flexible structure in a uniform flow, providing analytical solutions for the translating, axially flowing equilibria of strings subjected to a uniform body force and drag forces linear in the velocities. The classical catenaries are extended to a five-parameter family of curves. A sixth parameter affects the tension in the curves. Generic configurations are planar, represented by a single first order equation for the tangential angle. The effects of varying parameters on representative shapes, orbits in angle-curvature space, and stress distributions are shown. As limiting cases, the solutions include configurations corresponding to "lariat chains" and the towing, reeling, and sedimentation of flexible cables in a highly viscous fluid. Regions of parameter space corresponding to infinitely long, semi-infinite, and finite length curves are delineated. Almost all curves subtend an angle less than $\\pi$ radians, but curious special cases with doubled or infinite ra...
低气速条件下CO2在牛顿及非牛顿流体中气含率%Gas holdup of CO2 in Newtonian and non-Newtonian fluid at low gas velocity
Institute of Scientific and Technical Information of China (English)
李少白; 马友光; 付涛涛; 朱春英
2012-01-01
实验测定了低气速下CO2气泡群在牛顿流体、剪切变稀流体及黏弹性流体中的气含率.讨论了流体的流变性、质量分数及表观气速对气含率的影响.结果表明:在3种不同性质的流体中,气含率均随表观气速的增大而增大.同时发现流体性质对气含率具有不同的影响:对于牛顿流体,表观气速较低时,质量分数对气含率影响可忽略；对于非牛顿流体,气含率随着流动指数n的减小而减小,即剪切变稀效应对气含率有负作用,而黏弹性对气含率的影响可忽略.气含率是气液传质过程设计中最重要的参数,因此研究结果为进一步研究CO2气泡群在非牛顿流体中的传质奠定了一定基础.%The gas holdups of CO2 bubble swarm at low superficial gas velocity in Newtonian fluid, shear thinned fluid and viscoelastic fl uid were measured. The influences of rheological property, mass fraction and superficial gas velocity on the gas holdup were investigated. The results show that the gas holdups in three fluids all increase with the increase of superficial gas velocity, and different fluid has different effects on the gas holdup. The effect of mass fraction on the gas holdup in Newtonian fluid at low superficial gas velocity is negligible. For non-Newtonian fluid, the gas holdup decreases with the decrease of flow index n, that is, shear thinning effect has negative impact on the gas holdup, and the influence of viscoelasticity on the gas holdup is negligible. The gas holdup is the most important parameter for the gas-liquid mass transfer process design, and it provides a solid foundation for the research on mass transfer of CO2 bubble swarm in non-Newtonian fluid.
Effect of Mantle Rheology on Viscous Heating induced during Ice Sheet Cycles
Huang, Pingping; Wu, Patrick; van der Wal, Wouter
2017-04-01
Hanyk et al. (2005) studied the viscous shear heating in the mantle induced by the surface loading and unloading of a parabolic-shaped Laurentide-size ice sheet. They found that for linear rheology, viscous heating is mainly concentrated below the ice sheet. The depth extent of the heating in the mantle is determined by the viscosity distribution. Also, the magnitude of viscous heating is significantly affected by the rate of ice thickness change. However, only one ice sheet has been considered in their work and the interactions between ice sheets and ocean loading have been neglected. Furthermore, only linear rheology has been considered, although they suggested that non-Newtonian rheology may have a stronger effect. Here we follow Hanyk et al. (2005) and computed the viscous dissipation for viscoelastic models using the finite element methodology of Wu (2004) and van der Wal et al. (2010). However, the global ICE6G model (Peltier et al. 2015) with realistic oceans is used here to provide the surface loading. In addition, viscous heating in non-linear rheology, composite rheology, in addition to linear rheology with uniform or VM5a profile are computed and compared. Our results for linear rheology mainly confirm the findings of Hanyk et al. (2005). For both non-linear and composite rheologies, viscous heating is also mainly distributed near and under the ice sheets, but, more concentrated; depending on the horizontal dimension of the ice sheet, it can extend into the lower mantle, but for some of the time, not as deep as that for linear rheology. For composite rheology, the viscous heating is dominated by the effect of non-linear relation between the stress and the strain. The ice history controls the time when the local maximum in viscous heating appears. However, the magnitude of the viscous heating is affected by mantle rheology as well as the ice loading. Due to viscosity stratification, the shape of the region with high viscous heating in model VM5a is a
Unsteady Axisymmetric Rotational Flow of Dusty Elastico Viscous Liquid
Directory of Open Access Journals (Sweden)
G. C. Mandal
1990-04-01
Full Text Available This paper reports the flow of elastico-viscous liquid embedded with particles in an oscillating cylinder. Explicit expressions are obtained for the velocities of liquid and dust particles by the technique of Laplace transforms. Numerical computations of the velocity fields are carried out for different values of mass concentration and relaxation time of the dust particles and varying elastic elements in the liquid.
Properties of Accretion Shocks in Viscous Flows with Cooling Effects
Das, S; Das, Santabrata; Chakrabarti, Sandip K.
2004-01-01
Low angular momentum accretion flows can have standing and oscillating shock waves. We study the region of the parameter space in which multiple sonic points occur in viscous flows in presence of various cooling effects such as bremsstrahlung and Comptonization. We also quantify the parameter space in which shocks are steady or oscillating. We find that cooling induces effects opposite to heating by viscosity even in modifying the topology of the solutions, though one can never be exactly balanced by the other due to their dissimilar dependence on dynamic and thermodynamic parameters. We show that beyond a critical value of cooling, the flow ceases to contain a shock wave.
Quasiadiabatic modes from viscous inhomogeneities
Giovannini, Massimo
2016-01-01
The viscous inhomogeneities of a relativistic plasma determine a further class of entropic modes whose amplitude must be sufficiently small since curvature perturbations are observed to be predominantly adiabatic and Gaussian over large scales. When the viscous coefficients only depend on the energy density of the fluid the corresponding curvature fluctuations are shown to be almost adiabatic. After addressing the problem in a gauge-invariant perturbative expansion, the same analysis is repea...
Electro-spray of high viscous liquids for producing mono-sized spherical alginate beads
Institute of Scientific and Technical Information of China (English)
Hamid Moghadam; Mohsen Samimi; Abdolreza Samimi; Mohamad Khorram
2008-01-01
Alginate beads, often used for controlled release of enzymes and drugs, are usually produced by spraying sodium alginate liquid into a gelling agent using mechanical vibration nozzle or air jet. In this work an alternative method of electro-spray was employed to form droplets with desired size from a highly viscous sodium alginate solution using constant DC voltage. The droplets were then cured in a calcium chloride solution. The main objective was to produce mono-sized beads from such a highly viscous and non-Newtonian liquid (1000-5000 mPa s). The effects of nozzle diameter, flow rate and concentration of liquid on the size of the beads were investigated. Among the parameters studied, voltage had a pronounced effect on the size of beads as compared to flow rate zzle diameter and concentration of alginate liquid. The size of beads was reduced to a minimum value with increasing the voltage in the range of 0-10 kV. At the early stages of voltage increase (I.e. Up to about 4 kV), the rate of size reduction was relatively low, while the dripping mode dominated. However, in the middle part of the range of applied voltage, where the rate of size reduction was high (I.e. About 4-7 kV), an unstable transition occurred between dripping and jetting. At the end part of the range (I.e. 7-10 kV) jet mode of spray was observed. Increasing the height of fall of the droplets was found to improve the sphericity of the beads, because of the increased time of flight for the droplets. This was especially identifiable at higher concentrations of the alginate liquid (I.e. 3 w/v%)
Cavitation structures formed during the collision of a sphere with an ultra-viscous wetted surface
Mansoor, Mohammad M.
2016-05-05
We investigate the inception of cavitation and resulting structures when a sphere collides with a solid surface covered with a layer of non-Newtonian liquid having a kinematic viscosity of up to (Formula presented.) cSt. We show the existence of shear-stress-induced cavitation during sphere approach towards the base wall (i.e. the pressurization stage) in ultra-viscous films using a synchronized dual-view high-speed imaging system. For the experimental parameters employed, liquids having viscoelastic properties of (Formula presented.) are shown to enable sphere rebound without any prior contact with the solid wall. Cavitation by depressurization (i.e. during rebound) in such non-contact cases is observed to onset after a noticeable delay from when the minimum gap distance is reached. Also, the cavities created originate from remnant bubbles, being the remains of the primary bubble entrapment formed by the lubrication pressure of the air during film entry. Cases where physical contact occurs (contact cases) in 10 000 cSt (Formula presented.) cSt films produce cavities attached to the base wall, which extend into an hourglass shape. In contrast, strikingly different structures occur in the most viscous liquids due to the disproportionality in radial expansion and longitudinal extension along the cavity length. Horizontal shear rates calculated using particle image velocimetry (PIV) measurements show the apparent fluid viscosity to vary substantially as the sphere approaches and rebounds away from the base wall. A theoretical model based on the lubrication assumption is solved for the squeeze flow in the regime identified for shear-induced cavity events, to investigate the criterion for cavity inception in further detail. © 2016 Cambridge University Press
Quasiadiabatic modes from viscous inhomogeneities
Giovannini, Massimo
2016-04-01
The viscous inhomogeneities of a relativistic plasma determine a further class of entropic modes whose amplitude must be sufficiently small since curvature perturbations are observed to be predominantly adiabatic and Gaussian over large scales. When the viscous coefficients only depend on the energy density of the fluid the corresponding curvature fluctuations are shown to be almost adiabatic. After addressing the problem in a gauge-invariant perturbative expansion, the same analysis is repeated at a nonperturbative level by investigating the nonlinear curvature inhomogeneities induced by the spatial variation of the viscous coefficients. It is demonstrated that the quasiadiabatic modes are suppressed in comparison with a bona fide adiabatic solution. Because of its anomalously large tensor to scalar ratio the quasiadiabatic mode cannot be a substitute for the conventional adiabatic paradigm so that, ultimately, the present findings seems to exclude the possibility of a successful accelerated dynamics solely based on relativistic viscous fluids. If the dominant adiabatic mode is not affected by the viscosity of the background a sufficiently small fraction of entropic fluctuations of viscous origin cannot be a priori ruled out.
Structural Optimization of non-Newtonian Microfluidics
DEFF Research Database (Denmark)
Jensen, Kristian Ejlebjærg; Okkels, Fridolin
2011-01-01
a filter on the design variables based on a Helmholtz-type differential equation and we try to vary the filter length throughout the optimization in order to ensure compatibility with a convex interpolation between the inverse permeability and the design variables, which is popular within topology...
Quasiadiabatic modes from viscous inhomogeneities
Giovannini, Massimo
2016-01-01
The viscous inhomogeneities of a relativistic plasma determine a further class of entropic modes whose amplitude must be sufficiently small since curvature perturbations are observed to be predominantly adiabatic and Gaussian over large scales. When the viscous coefficients only depend on the energy density of the fluid the corresponding curvature fluctuations are shown to be almost adiabatic. After addressing the problem in a gauge-invariant perturbative expansion, the same analysis is repeated at a non-perturbative level by investigating the nonlinear curvature inhomogeneities induced by the spatial variation of the viscous coefficients. It is demonstrated that the quasiadiabatic modes are suppressed in comparison with a bona fide adiabatic solution. Because of its anomalously large tensor to scalar ratio the quasiadiabatic mode cannot be a substitute for the conventional adiabatic paradigm so that, ultimately, the present findings seems to exclude the possibility of a successful accelerated dynamics solely...
Solidity of viscous liquids. II
DEFF Research Database (Denmark)
Dyre, Jeppe
1999-01-01
Recent findings on displacements in the surroundings of isotropic flow events in viscous liquids [Phys. Rev. E 59, 2458 (1999)] are generalized to the anisotropic case. Also, it is shown that a flow event is characterized by a dimensionless number reflecting the degree of anisotropy....
Solidity of viscous liquids. III
DEFF Research Database (Denmark)
Dyre, Jeppe
2005-01-01
It is suggested that the omega^{-1/2} high-frequency decay of the alpha loss in highly viscous liquids, which appears to be generic, is a manifestation of a negative long-time tail as typically encountered in stochastic dynamics. The proposed mechanism requires that the coherent diffusion constan...
Nonlinear wavetrains in viscous conduits
Maiden, Michelle; Hoefer, Mark
2016-11-01
Viscous fluid conduits provide an ideal system for the study of dissipationless, dispersive hydrodynamics. A dense, viscous fluid serves as the background medium through which a lighter, less viscous fluid buoyantly rises. If the interior fluid is continuously injected, a deformable pipe forms. The long wave interfacial dynamics are well-described by a dispersive nonlinear partial differential equation. In this talk, experiments, numerics, and asymptotics of the viscous fluid conduit system will be presented. Structures at multiple length scales are discussed, including solitons, dispersive shock waves, and periodic waves. Modulations of periodic waves will be explored in the weakly nonlinear regime with the Nonlinear Schrödinger (NLS) equation. Modulational instability (stability) is identified for sufficiently short (long) periodic waves due to a change in dispersion curvature. These asymptotic results are confirmed by numerical simulations of perturbed nonlinear periodic wave solutions. Also, numerically observed are envelope bright and dark solitons well approximated by NLS. This work was partially supported by NSF CAREER DMS-1255422 (M.A.H.) and NSF GRFP (M.D.M.).
Energy Technology Data Exchange (ETDEWEB)
Kauder, K.; Deipenwisch, R. [Dortmund Univ. (Germany). FG Fluidenergiemaschinen
1998-12-31
The model of the calculation of the friction losses caused by oil described in this report delivers a starting point for the integration of the design parameter `oil` for oil injected screw-type engines. The use of non newtonian oils with a shear thinning behaviour lead to a decrease of energy consumption over a broad speed range of screw-type compressors. The decrease is mainly caused by the shear indicated lower viscosity in the clearances of the compressor. A difficulty through the use of this oils is the estimation of the conditions in the clearances. The rate of shear in the single clearance is influenced by the relative speed of the boundaries and by the height of the clearance during operation. Up to now only cold heights were used in the model. To improve the quality of the model the clearances of a running screw compressor were measured. The losses which were determined at the screw compressor test plant are the summation of all losses including the losses caused by the power transmission and in the bearings. Experiments at a model rotor test stand make the determination of the friction losses and the losses by the acceleration of the oil in the clearances possible. A better calculation model shall deliver the conditions to describe the influence of the oil on the energy efficiency and to define the optimal oil for every screw compressor. (orig.) [Deutsch] Das beschriebene Modell zur Berechnung der hydraulischen Verluste in der nasslaufenden Schraubenmaschine liefert Ansaetze, um das Oel schon bei der Auslegung der Schraubenkompressoren als Konstruktionselement mit einzubeziehen. Sinnvoll ist die Nutzung eines nicht-newtonschen Oeles immer dann, wenn eine deutliche scherindizierte Viskositaetserniedrigung in dem Schergeschwindigkeitsbereich, der in den Spalten des Schraubenkompressors vorliegt, erreicht werden kann. Beim Einsatz dieser Oele besteht die Schwierigkeit darin, den Schergeschwindigkeitsbereich vorherzubestimmen, der waehrend des Betriebs in dem
Simulations of Viscous Accretion Flow around Black Holes in Two-Dimensional Cylindrical Geometry
Lee, Seong-Jae; Kumar, Rajiv; Hyung, Siek; Ryu, Dongsu
2016-01-01
We simulate shock-free and shocked viscous accretion flow onto a black hole in a two dimensional cylindrical geometry, where initial conditions were chosen from analytical solutions. The simulation code used the Lagrangian Total Variation Diminishing (LTVD) and remap routine, which enabled us to attain high accuracy in capturing shocks and to handle the angular momentum distribution correctly. Inviscid shock-free accretion disk solution produced a thick disk structure, while the viscous shock-free solution attained a Bondi-like structure, but in either case, no jet activity nor any QPO-like activity developed. The steady state shocked solution in the inviscid, as well as, in the viscous regime, matched theoretical predictions well. However, increasing viscosity renders the accretion shock unstable. Large amplitude shock oscillation is accompanied by intermittent, transient inner multiple shocks. Such oscillation of the inner part of disk is interpreted as the source of QPO in hard X-rays observed in micro-qua...
Photometric modeling of viscous overstability in Saturn's rings
Salo, H.; Schmidt, J.
2011-10-01
The viscous overstability of dense planetary rings offers a plausible mechanism for the generation of observed ~ 150 m radial density variations in the B and the inner A ring of Saturn [1, 12]. Viscous overstability, in the form of spontaneous growth of axisymmetric oscillations, arises naturally in N-body simulations, in the limit of high impact frequency and moderately weak selfgravity [4, 8, 9, 10]. For example, a selfgravitating system of identical particles with internal density ~ half of solid ice, becomes overstable for optical depths τ > 1, forming oscillations on about 100 meter scale. Like self-gravity wakes (with typical ~ 20° trailing pitch angle), overstable oscillations lead to alongitude-dependent brightness of the rings. Due to their axisymmetric nature, the expected longitude of minimum brightness is shifted closer to ring ansae (for small phase angles). Moreover, according to simulations, the axisymmetric oscillations may coexist with the inclined selfgravity wake structures, which can lead to complicated photometric behavior as a function of illumination and viewing geometries, depending on properties of the simulated system. For example, at low viewing elevations, the vertical thickenings associated with the density crests should cast shadows on the nearby ring particles (see Fig. 1 for an example; darker areas are due to shadows, not due to depletion of particles). Though these shadows would be unresolved, they might still affect the integrated brightness at certain geometries. The overstable systems may also exhibit amplitude variations (in km-scales), arising from the mutual beating patterns of the basic sub-km overstable oscillations [3]. Such modulations of oscillation amplitude may lead to associated brightness variations. New results of photometric modeling of viscously overstable dynamical simulations systems are reported, related to the above mentioned topics. The Monte Carlo method of [5] is used, previously applied to modeling of
Swarms of particles settling under gravity in a viscous fluid
Ekiel-Jezewska, Maria L
2012-01-01
We investigate swarms made of a small number of particles settling under gravity in a viscous fluid. The particles do not touch each other and can move relative to each other. The dynamics is analyzed in the point-particle approximation. A family of swarms is found with periodic oscillations of all the settling particles. In the presence of an additional particle above the swarm, the trajectories are horizontally repelled from the symmetry axis, and flattened vertically. The results are used to explain how a spherical cloud, made of a large number of particles distributed at random, evolves and destabilizes.
Computation of Viscous Incompressible Flows
Kwak, Dochan
2011-01-01
This monograph is intended as a concise and self-contained guide to practitioners and graduate students for applying approaches in computational fluid dynamics (CFD) to real-world problems that require a quantification of viscous incompressible flows. In various projects related to NASA missions, the authors have gained CFD expertise over many years by developing and utilizing tools especially related to viscous incompressible flows. They are looking at CFD from an engineering perspective, which is especially useful when working on real-world applications. From that point of view, CFD requires two major elements, namely methods/algorithm and engineering/physical modeling. As for the methods, CFD research has been performed with great successes. In terms of modeling/simulation, mission applications require a deeper understanding of CFD and flow physics, which has only been debated in technical conferences and to a limited scope. This monograph fills the gap by offering in-depth examples for students and engine...
Kelly; Humphrey
1998-03-01
Considerable debate has occurred over the use of hydrofoil impellers in large-scale fermentors to improve mixing and mass transfer in highly viscous non-Newtonian systems. Using a computational fluid dynamics software package (Fluent, version 4.30) extensive calculations were performed to study the effect of impeller speed (70-130 rpm), broth rheology (value of power law flow behavior index from 0.2 to 0.6), and distance between the cooling coil bank and the fermentor wall (6-18 in.) on flow near the perimeter of a large (75-m3) fermentor equipped with A315 impellers. A quadratic model utilizing the data was developed in an attempt to correlate the effect of A315 impeller speed, power law flow behavior index, and distance between the cooling coil bank and the fermentor wall on the average axial velocity in the coil bank-wall region. The results suggest that there is a potential for slow or stagnant flow in the coil bank-wall region which could result in poor oxygen and heat transfer for highly viscous fermentations. The results also indicate that there is the potential for slow or stagnant flow in the region between the top impeller and the gas headspace when flow through the coil bank-wall region is slow. Finally, a simple guideline was developed to allow fermentor design engineers to predict the degree of flow behind a bank of helical cooling coils in a large fermentor with hydrofoil flow impellers.
Directory of Open Access Journals (Sweden)
S. Saouli
2009-06-01
Full Text Available A second-law analysis of a gravity-driven film of non-Newtonian fluid along an inclined heated plate is investigated. The flow is assumed to be steady, laminar and fully-developed. The upper surface of the liquid film is considered to be free and adiabatic. The effect of heat generation by viscous dissipation is included. Velocity, temperature and entropy generation profiles are presented. The effects of the flow behaviour index, the Brinkman number and the group parameter on velocity, temperature and entropy generation number are discussed. The results show that velocity profile depends largely on the flow behaviour index. They are flat near the free surface for pseudoplastic fluids and linear for dilatant fluids. Temperature profiles are higher for higher flow behaviour index and Brinkman number. The entropy generation number increases with Brinkman number and the group parameter because of the heat generated by the viscous dissipation effect. For pseudoplastic fluids, the irreversibility is dominated by heat transfer, whereas, for dilatant fluids, irreversibility due to fluid friction is more dominant.
Rotationally symmetric viscous gas flows
Weigant, W.; Plotnikov, P. I.
2017-03-01
The Dirichlet boundary value problem for the Navier-Stokes equations of a barotropic viscous compressible fluid is considered. The flow region and the data of the problem are assumed to be invariant under rotations about a fixed axis. The existence of rotationally symmetric weak solutions for all adiabatic exponents from the interval (γ*,∞) with a critical exponent γ* < 4/3 is proved.
Viscous property of dried clay
Institute of Scientific and Technical Information of China (English)
XU Li-sheng; LI Jian-zhong
2006-01-01
One dimensional and triaxial compression tests of air-dried and oven-dried Fujinomori clay and Pisa clay were carried out. Water content is less than 4.5 % and 1.0% for air-dried and oven-dried clay specimens, respectively. In all tests, axial strain rate was changed stepwise many times and drained creep tests were performed several times during monotonic loading at a constant strain rate. Global unloading (and also reloading in some tests) was applied during which creep loading tests were performed several times. Cyclic loading with small stress amplitude and several cycles was also performed to calculate the modulus of elasticity of the clay in tests. Local displacement transducer was used in triaxial compression test to increase measuring accuracy of axial strain. The results show that air-dried and oven-dried clay have noticeable viscous properties; during global unloading, creep deformation changes from positive to negative, i.e. there exist neutral points (zero creep deformation or no creep deformation point) in global unloading part of strain-stress curve; viscous property of Fujinomori clay decreases when water content decreases, i.e. viscous property of air-dried Fujinomori clay is more significant than that of oven-dried Fujinomori clay.
Electromagnetic properties of viscous charged fluids
Forcella, Davide; Zaanen, Jan; Valentinis, Davide; van der Marel, Dirk
2014-07-01
We provide a general theoretical framework to describe the electromagnetic properties of viscous charged fluids, consisting, for example, of electrons in certain solids or plasmas. We confirm that finite viscosity leads to multiple modes of evanescent electromagnetic waves at a given frequency, one of which is characterized by a negative index of refraction, as previously discussed in a simplified model by one of the authors. In particular, we explain how optical spectroscopy can be used to probe the viscosity. We concentrate on the impact of this on the coefficients of refraction and reflection at the sample-vacuum interface. Analytical expressions are obtained relating the viscosity parameter to the reflection and transmission coefficients of light. We demonstrate that finite viscosity has the effect to decrease the reflectivity of a metallic surface, while the electromagnetic field penetrates more deeply. While on a phenomenological level there are similarities to the anomalous skin effect, the model presented here requires no particular assumptions regarding the corpuscular nature of the charge liquid. A striking consequence of the branching phenomenon into two degenerate modes is the occurrence in a half-infinite sample of oscillations of the electromagnetic field intensity as a function of distance from the interface.
Simulations of Viscous Accretion Flow around Black Holes in a Two-dimensional Cylindrical Geometry
Lee, Seong-Jae; Chattopadhyay, Indranil; Kumar, Rajiv; Hyung, Siek; Ryu, Dongsu
2016-11-01
We simulate shock-free and shocked viscous accretion flows onto a black hole in a two-dimensional cylindrical geometry, where initial conditions were chosen from analytical solutions. The simulation code used the Lagrangian total variation diminishing plus remap routine, which enabled us to attain high accuracy in capturing shocks and to handle the angular momentum distribution correctly. The inviscid shock-free accretion disk solution produced a thick disk structure, while the viscous shock-free solution attained a Bondi-like structure, but in either case, no jet activity nor any quasi-periodic oscillation (QPO)-like activity developed. The steady-state shocked solution in the inviscid as well as in the viscous regime matched theoretical predictions well. However, increasing viscosity renders the accretion shock unstable. Large-amplitude shock oscillation is accompanied by intermittent, transient inner multiple shocks. This oscillation of the inner part of the disk is interpreted as the source of QPO in hard X-rays observed in micro-quasars. Strong shock oscillation induces strong episodic jet emission. The jets also show the existence of shocks, which are produced as one shell hits the preceding one. The periodicities of the jets and shock oscillation are similar; the jets for the higher viscosity parameter appear to be stronger and faster.
Temperature Effect on Rheological Behavior of Silicone Oils. A Model for the Viscous Heating.
Romano, Mario R; Cuomo, Francesca; Massarotti, Nicola; Mauro, Alessandro; Salahudeen, Mohamed; Costagliola, Ciro; Ambrosone, Luigi
2017-07-27
The rheological behavior of silicone oils, (CH3)3SiO-[Si(CH3)2O]n-Si(CH3)3, and their mixtures is studied. Shear-stress measurements, in the temperature range of 293-313 K, reveal that this polymer family is a group of shear-thinning liquids with a yield stress below which no flow occurs. Experimental diagrams, i.e., shear stress versus shear rate, are satisfactorily described by the Casson fluid model over a wide range of shear rates. In order to monitor the effect of temperature on fluid properties, Casson's rheological model is reformulated using the fictitious shear rate, γ̇f, and the infinite-shear viscosity, η∞, as constitutive parameters. Due to low intermolecular forces and high chain flexibility, γ̇f varies very little when the temperature increases. For this reason, the apparent material viscosity depends on temperature only through η∞, which exponentially decreases until high shear rates are reached, and there is more alignment possible. Interestingly, the temperature sensitivity of this pseudoplastic behavior is the same for all of the silicone oils investigated; therefore, they can be classified according to their tendency to emulsify. Experimental results are then used to model the flow of silicone oils in a cylindrical pipe and estimate the temperature increase due to viscous heating. Numerical results show that the normalized temperature, i.e., ratio of fluid temperature to wall temperature, increases approximately 23%, and the apparent viscosity decreases drastically, going toward the center of the tube. The non-Newtonian nature of fluid is reflected in the presence of a critical region. In this region, the velocity and temperature gradients vanish. Since silicon oil is a surgical tool, we hope that the acquired physicochemical information can provide help to facilitate the removal of this material during surgical procedures.
Institute of Scientific and Technical Information of China (English)
闻建平; 贾晓强; 毛国柱
2004-01-01
A small scale isotropic mass transfer model was developed for the local liquid side mass transfer coefficients in gas-liquid-solid three-phase flow airlift loop reactor for Newtonian and non-Newtonian fluids.It is based on Higbie's penetration theory and Kolmogoroff's theory of isotropic turbulence with k1 = 3√2Dε1/3 1/π(η-1/3 1 -λ-1/3 f),where ε1 is local rate of energy dissipation,λf is the local microscale,η1 is the local Kolmogoroff scale and D is the diffusion coefficient.The capability of the proposed model is discussed in the light of experimental data obtained from 12 L gas-liquid-solid three-phase flow airlift loop reactor using Newtonian and non-Newtonian fluids.Good agreement with the experimental data was obtained over a wide range of conditions suggesting a general applicability of the proposed model.
Georgievskii, D. V.
2007-06-01
physical parameter α can be imposed. These variations imply perturbations of the tensor function itself. The components of such perturbations linear and quadratic in α are determined. In each of the approximations, we write out a closed system of equations consisting of the equations of motion (linear in the variables of the respective approximation) and the incompressibility condition. We analyze tensor-linear functions with arbitrary scalar rheology inmore detail. Materials with such constitutive relations include non-Newtonian viscous fluids and viscoplastic materials. Viscoplastic materials are characterized by the existence of rigidity zones, where the stress intensity is less than the yield strength. We derive equations for the boundaries of the rigidity zones in the perturbed motion, in particular, for the case in which the unperturbed medium is a viscous Newtonian fluid. Throughout the paper, index-free notation is used.
On the Impact of Spheres onto Liquid Pools and Ultra-viscous Films
Mansoor, Mohammad Mujtaba
2016-06-01
The free-surface impact of spheres is important to several applications in the military, industry and sports such as the water-entry of torpedoes, dip-coating procedures and slamming of boats. This two-part thesis attempts to explore this field by investigating cavity formation during the impact of spheres with deep liquid pools and cavitation in thin ultra-viscous films. Part I reports results from an experimental study on the formation of stable- streamlined and helical cavity wakes following the free-surface impact of heated Leidenfrost spheres. The Leidenfrost effect encapsulates the sphere by a vapor layer to prevent any physical contact with the surrounding liquid. This phenomenon is essential for the pacification of acoustic rippling along the cavity interface to result in a stable-streamlined cavity wake. Such a streamlined configuration experiences drag coefficients an order of magnitude lower than those acting on room temperature spheres. A striking observation is the formation of helical cavities which occur for impact Reynolds numbers 0 ≳ 1.4 × 105 and are characterized by multiple interfacial ridges, stemming from and rotating synchronously about an evident contact line around the sphere equator. This helical configuration has 40-55% smaller overall force coefficients than those obtained in the formation of stable cavity wakes. Part II of this thesis investigates the inception of cavitation and resulting structures when a sphere collides with a solid surface covered with a layer of non-Newtonian liquid having kinematic viscosities of up to 0 = 20,000,000 cSt. The existence of shear-stress- induced cavitation during sphere approach towards the base wall (i.e. the pressurization stage) in ultra-viscous films is shown using a synchronized dual-view high-speed imaging system. In addition, cavitation by depressurization is noted for a new class of non-contact cases whereby the sphere rebounds without any prior contact with the solid wall. Horizontal
Ten themes of viscous liquid dynamics
DEFF Research Database (Denmark)
Dyre, J. C.
2007-01-01
Ten ‘themes' of viscous liquid physics are discussed with a focus on how they point to a general description of equilibrium viscous liquid dynamics (i.e., fluctuations) at a given temperature. This description is based on standard time-dependent Ginzburg-Landau equations for the density fields...
Improving longitudinal motion prediction of hybrid monohulls with the viscous effect
Institute of Scientific and Technical Information of China (English)
ZHANG Heng; LI Ji-de
2007-01-01
A new method improves prediction of the motion of a hybrid monohull in regular waves. Stem section hydrodynamic coefficients of a hybrid monohull with harmonic oscillation were computed using the Reynolds Averaged Navier-Stokes Equations (RANSE). The governing equations were solved using the finite volume method. The VOF method was used for free surface treatment, and RNGK-ε turbulence model was employed in viscous flow calculation. The whole computational domain was divided into many blocks each with structured grids, and the dynamic process was treated with moving grids. Using a 2-D strip method and 2.5D theory with the correction hydrodynamic coefficients allows consideration of the viscous effect when predicting longitudinal motion of a hybrid monohull in regular waves. The method is effective at predicting motion of a hybrid monohull, showing that the viscous effect on a semi-submerged body cannot be ignored.
Time-varied magnetic field enhances transport of magnetic nanoparticles in viscous gel.
MacDonald, Cristin; Friedman, Gary; Alamia, John; Barbee, Kenneth; Polyak, Boris
2010-01-01
The potential of magnetic nanoparticles (MNPs) to deliver various forms of therapy has not been fully realized, in part due to difficulties in transporting the carriers through soft tissue to different target sites. The aim of this study was to demonstrate that transport of MNPs through a viscous gel can be controlled by a combined AC (time-varying) magnetic field and static field gradient. MNP velocity and transport efficiency were measured in a viscous gel at various settings of magnetic field and magnetite loadings. Combined application of an AC magnetic field with the static field gradient resulted in a nearly 30-fold increase in MNP transport efficiency in viscous gel for 30% (w/w) magnetite-loaded particles as compared with static field conditions. The 'oscillating' effect of an AC magnetic field greatly improves the ability to transport MNPs within soft media by decreasing the effective viscosity of the gel.
Espinosa, Ismael; Gonzalez, Hortensia; Quiza, Jorge; Gonazalez, J. Jesus; Arroyo, Ruben; Lara, Ritaluz
1995-01-01
Oscillation of electrical activity has been found in many nervous systems, from invertebrates to vertebrates including man. There exists experimental evidence of very simple circuits with the capability of oscillation. Neurons with intrinsic oscillation have been found and also neural circuits where oscillation is a property of the network. These two types of oscillations coexist in many instances. It is nowadays hypothesized that behind synchronization and oscillation there is a system of coupled oscillators responsible for activities that range from locomotion and feature binding in vision to control of sleep and circadian rhythms. The huge knowledge that has been acquired on oscillators from the times of Lord Rayleigh has made the simulation of neural oscillators a very active endeavor. This has been enhanced with more recent physiological findings about small neural circuits by means of intracellular and extracellular recordings as well as imaging methods. The future of this interdisciplinary field looks very promising; some researchers are going into quantum mechanics with the idea of trying to provide a quantum description of the brain. In this work we describe some simulations using neuron models by means of which we form simple neural networks that have the capability of oscillation. We analyze the oscillatory activity with root locus method, cross-correlation histograms, and phase planes. In the more complicated neural network models there is the possibility of chaotic oscillatory activity and we study that by means of Lyapunov exponents. The companion paper shows an example of that kind.
Interface Oscillation in the Side-by-Side (SBS) Tape Casting of Functionally Graded Ceramics (FGCs)
DEFF Research Database (Denmark)
Jabbari, Masoud; Bulatova, Regina; Hattel, Jesper Henri
2012-01-01
is a common process in producing multilayer ceramics, which now is used for producing side-by-side (SBS) functionally graded ceramics (FGCs). These FGCs are mostly used in the magnetic refrigeration sectors due to the varying composition of the magnetocaloric materials so that the magnetic transition...... temperature of the magnetic regenerator varies along the paths. The main goal of this research is to study the multiple material flow in SBS tape casting and analyze its influence on the interface between the stripes. The materials used for the experimental part are La0.85Sr0.15MnO3 and Ce0.9Gd0.1O2ceramic...... slurries. The rheological behavior of the slurries are extracted from experiments and used in the ANSYS FLUENT commercial code to develop a fluid flow model for the non-Newtonian ceramic slurries and evaluate the interface oscillation between the stripes in SBS tape casting. The Numerical results show...
Energy Technology Data Exchange (ETDEWEB)
Atakishiyev, N.M. [Instituto de Matematicas. Universidad Nacional Autonoma de Mexico. Cuernavaca, Morelos (Mexico); Jafarov, E.I.; Nagiyev, S.M. [Institute of Physics, Azerbaijan Academy of Sciences. Baku, Azerbaijan (Azerbaijan); Wolf, K.B. [Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas. Universidad Nacional Autonoma de Mexico. Cuernavaca, Morelos (Mexico)
1998-10-01
Meixner oscillators have a ground state and an energy spectrum that is equally spaced; they are a two-parameter family of models that satisfy a Hamiltonian equation with a difference operator. Meixner oscillators include as limits and particular cases the Charlier, Kravchuk and Hermite (common quantum-mechanical) harmonic oscillators. By the Sommerfeld-Watson transformation they are also related with a relativistic model of the linear harmonic oscillator, built in terms of the Meixner-Pollaczek polynomials, and their continuous weight function. We construct explicitly the corresponding coherent states with the dynamical symmetry group Sp(2,R). The reproducing kernel for the wavefunctions of these models is also found. (Author)
Institute of Scientific and Technical Information of China (English)
F·M·哈迪; F·S·艾伯拉赫门; S·M·阿卜杜勒·盖德; M·R·艾德; 吴承平; 张禄坤
2011-01-01
在层流条件下,对饱和多孔介质中的竖直板,研究幂指数型非Newton流的自由对流热交换.非Newton纳米流体服从幂指数型的数学模型,模型综合考虑了Brown运动和热泳的影响.通过相似变换,将问题的偏微分控制方程组,转化为常微分方程组,得到了常微分方程组的数值解.数值解依赖于幂指数n,Lewis数Le,浮力比Nr,Brown运动参数Nb,以及热泳参数Nt.在n和Le的不同取值下,研究并讨论了对相关流体性质参数的影响和简化的Nusselt数.%The free convective heat transfer to the power-law non-Newtonian from a vertical plate in a porous medium saturated with nanofluid under laminar conditions was investigated. It was considered that the non-Newtonian nanofluid obeys the mathematical model of power-law. The model used for the nanofluid incorporates the effects of Brownian motion and thermo-phoresis. The partial differential system governing the problem was transformed into an ordinary system via a usual similarity transformation. The numerical solutions of the resulting ordinary system were obtained. These solutions depend on the power-law index n, Lewis number Le, buoyancy-ratio number Nr, Brownian motion number Nb and thermophoresis number Nt. For various values of n and Le, the effect of the influence parameters on the fluid behavior as well as the reduced Nusselt number was presented and discussed.
Institute of Scientific and Technical Information of China (English)
S·M·阿布德尔-盖德; M·R·伊德
2011-01-01
在一个轴对称、外形任意的多孔介质二维体中,充满了有屈服应力的非Newton幂律流体时,数值分析其自由对流及其传热/传质问题,利用相似变换,将边界层控制方程及其边界条件变换为无量纲形式,然后用有限差分法求解该方程组.所研究的参数为流变常数、浮力比和Lewis数.给出并讨论了典型的速度、温度及浓度曲线,发现屈服应力参数值和非Newton流体的幂律指数对结果有着显著的影响.%Numerical analysis of free convection coupled heat and mass transfer was presented for non-Newtonian power-law fluids with yield stress flowing over two-dimensional or axisymmetric body of arbitrary shape in a fluid-saturated porous medium.The governing boundary layer equations and boundary conditions were cast into a dimensionless form by similarity transformation and the resulting system of equations was solved by a finite difference method.The parameters studied were the rheologicai constants, the buoyancy ratio, and the Lewis number.Representative velocity as well as temperature and concentration profiles were presented and discussed.It was found that the result depend strongly on the values of the yield stress parameter, and the power-law index of non-Newtonian fluid.
Viscous fingering of miscible slices
De Wit, A; Martin, M; Wit, Anne De; Bertho, Yann; Martin, Michel
2005-01-01
Viscous fingering of a miscible high viscosity slice of fluid displaced by a lower viscosity fluid is studied in porous media by direct numerical simulations of Darcy's law coupled to the evolution equation for the concentration of a solute controlling the viscosity of miscible solutions. In contrast with fingering between two semi-infinite regions, fingering of finite slices is a transient phenomenon due to the decrease in time of the viscosity ratio across the interface induced by fingering and dispersion processes. We show that fingering contributes transiently to the broadening of the peak in time by increasing its variance. A quantitative analysis of the asymptotic contribution of fingering to this variance is conducted as a function of the four relevant parameters of the problem i.e. the log-mobility ratio R, the length of the slice l, the Peclet number Pe and the ratio between transverse and axial dispersion coefficients $\\epsilon$. Relevance of the results is discussed in relation with transport of vi...
Causal viscous cosmology without singularities
Laciana, Carlos E
2016-01-01
An isotropic and homogeneous cosmological model with a source of dark energy is studied. That source is simulated with a viscous relativistic fluid with minimal causal correction. In this model the restrictions on the parameters coming from the following conditions are analized: a) energy density without singularities along time, b) scale factor increasing with time, c) universe accelerated at present time, d) state equation for dark energy with "w" bounded and close to -1. It is found that those conditions are satified for the following two cases. i) When the transport coefficient ({\\tau}_{{\\Pi}}), associated to the causal correction, is negative, with the aditional restriction {\\zeta}|{\\tau}_{{\\Pi}}|>2/3, where {\\zeta} is the relativistic bulk viscosity coefficient. The state equation is in the "phantom" energy sector. ii) For {\\tau}_{{\\Pi}} positive, in the "k-essence" sector. It is performed an exact calculation for the case where the equation of state is constant, finding that option (ii) is favored in r...
Numerical investigation of phase relationships in an oscillating sessile drop
Korenchenko, A. E.; Malkova, J. P.
2015-10-01
Forced linear oscillations of a viscous drop placed on a horizontal surface vibrating in perpendicular direction are investigated. The problem is solved for two cases: (1) constant contact angle, and (2) pinned contact line. Phase-frequency and amplitude-frequency characteristics of oscillations of the drop apex are found for the first axisymmetrical mode of oscillations. The independence of the difference of oscillation phases of the drop apex and the substrate on fluid density, viscosity, surface tension, and drop size as well as on presence or absence of the gravity force was demonstrated.
Li, Fenfang; Nguyen, Dang Minh; Ohl, Claus-Dieter
2016-01-01
We report about an intriguing boiling regime occurring for small heaters embedded on the boundary in subcooled water. The microheater is realized by focusing a continuous wave laser beam to about $10\\,\\mu$m in diameter onto a 165\\,nm-thick layer of gold, which is submerged in water. After an initial vaporous explosion a single bubble oscillates continuously and repeatably at several $100\\,$kHz. The microbubble's oscillations are accompanied with bubble pinch-off leading to a stream of gaseous bubbles into the subcooled water. The self-driven bubble oscillation is explained with a thermally kicked oscillator caused by the non-spherical collapses and by surface pinning. Additionally, Marangoni stresses induce a recirculating streaming flow which transports cold liquid towards the microheater reducing diffusion of heat along the substrate and therefore stabilizing the phenomenon to many million cycles. We speculate that this oscillate boiling regime may allow to overcome the heat transfer thresholds observed dur...
Institute of Scientific and Technical Information of China (English)
臧晓红; 王军; 刘延来; 沈自求
2006-01-01
在-气升式内环流反应器中试验考察了非牛顿流体羧甲基纤维素钠(CMC)中的气泡聚并现象以及表面活性物质对液相体积传质系数的影响.结果表明,非牛顿流体中气-液传质效率随黏度的增加而降低,其原因是黏度增加使Taylor泡的尾流趋于稳定,降低了液相扰动,气泡间易聚并,从而气-液传质效率低.向非牛顿流体中添加醇类物质会影响气-液传质行为,对于聚合物含量低的流体,添加微量醇可以促进气-液传质,聚合物含量高的非牛顿流体,微量醇的加入反而不利于气-液间传质过程.非牛顿流体在ILAR上升管中的气含率随着黏度的增加变化不大,而下降管中的气含率有所提高.
Low moduli elastomers with low viscous dissipation
DEFF Research Database (Denmark)
Bejenariu, Anca Gabriela; Yu, Liyun; Skov, Anne Ladegaard
2012-01-01
A controlled reaction schema for addition curing silicones leads to both significantly lower elastic modulus and lower viscous dissipation than for the chemically identical network prepared by the traditional reaction schema....
Directory of Open Access Journals (Sweden)
Kishan N.
2014-05-01
Full Text Available A fluid flow and heat transfer analysis of an electrically conducting non-Newtonian power law fluid flowing over a non-linear stretching surface in the presence of a transverse magnetic field taking into consideration viscous dissipation effects is investigated. The stretching velocity, the temperature and the transverse magnetic field are assumed to vary in a power-law with the distance from the origin. The flow is induced due to an infinite elastic sheet which is stretched in its own plane. The governing equations are reduced to non-linear ordinary differential equations by means of similarity transformations. By using quasi-linearization techniques first linearize the non linear momentum equation is linearized and then the coupled ordinary differential equations are solved numerically by an implicit finite difference scheme. The numerical solution is found to be dependent on several governing parameters, including the magnetic field parameter, power-law index, Eckert number, velocity exponent parameter, temperature exponent parameter, modified Prandtl number and heat source/sink parameter. A systematic study is carried out to illustrate the effects of these parameters on the fluid velocity and the temperature distribution in the boundary layer. The results for the local skin-friction coefficient and the local Nusselt number are tabulated and discussed.
Energy Technology Data Exchange (ETDEWEB)
Wuensch, O.; Boehme, G. [Universitaet der Bundeswehr, Hamburg (Germany). Inst. fuer Stroemungslehre und Stroemungsmaschinen
2001-05-01
Peoples running screw machines are strongly interested in a detailed theoretical analysis of the transport processes for real highly viscous liquids which are non-Newtonian in general. The paper deals with an unconventional strategy which enables to simulate the three-dimensional unsteady flow in the kneading zone of intermeshing twin-screw extruders numerically. The concept is pointed at a finite element approximation of the flow field at particular times well chosen after the computation domain has been minimized with the aid of periodicities and symmetries existing in space and time. The method has been realized numerically and proved by means of a typical kneading geometry. Selected results show that the flow and deformation processes in the kneading element differ substantially from those in a screwed segment. (orig.) [German] Es besteht ein erhebliches Interesse daran, die Transportprozesse in Schneckenmaschinen fuer reale hochviskose, nichtnewtonsche Fluessigkeiten im Detail theoretisch zu analysieren und berechenbar zu machen. In der Arbeit wird eine unkonventionelle Strategie beschrieben, nach der die dreidimensionale instationaere Stroemung im Knetbereich kaemmender Doppelschnecken numerisch simuliert werden kann. Das theoretisch fundierte Konzept zielt auf eine Finite-Elemente-Approximation des Stroemungsfelds zu gewissen Zeitpunkten, wobei das Berechnungsgebiet mit Hilfe raeumlicher und zeitlicher Periodizitaeten und Symmetrien minimiert wird. Das Konzept wurde numerisch realisiert und an einer typischen Knetgeometrie erprobt. Ausgewaehlte Ergebnisse machen deutlich, da paragraph sich die Stroemungs- und Deformationsprozesse in einem Knetelement wesentlich von denen in einem Schraubenelement gleicher Geometrie unterscheiden. (orig.)
Diffusion coefficients in viscous sodium alginate solutions
Aoki, K.; Wang, B; Chen, J.; Nishiumi, T.
2012-01-01
Sodium alginate solution, being viscous hydrocolloid, was examined voltammetricallyin the context of viscous effects by use of a ferrocenyl compound as a redox probe.Voltammograms were almost independent of concentrations of sodium alginate even ina solid-like state. Diffusion coefficients of the ferrocenyl compound did not vary withviscosity evaluated by a viscometer. Ionic conductivity of sodium alginate was alsoindependent of the viscosity. In contrast, diffusion coefficients of the latex ...
Star-shaped Oscillations of Leidenfrost Drops
Ma, Xiaolei; Burton, Justin C
2016-01-01
We experimentally investigate the self-organized, star-shaped oscillations of Leidenfrost drops. The drops levitate on a cushion of evaporated vapor over a heated, curved surface. We observe modes with $n = 2-13$ lobes around the drop periphery. We find that both the wavelength and frequency of the oscillations depend only on the capillary length of the liquid, and are independent of the drop radius and substrate temperature. However, the number of observed modes depend sensitively on the liquid viscosity. The dominant frequency of pressure variations under the drop is approximately twice that the drop oscillation frequency, consistent with a parametric forcing mechanism. Our results suggest that the star-shaped oscillations are hydrodynamic in origin, and are driven by capillary waves beneath the drop. The exact mechanism by which the vapor flow initiates the capillary waves is likely related to static "brim waves" in levitated, viscous drops.
Mean Velocity Estimation of Viscous Debris Flows
Institute of Scientific and Technical Information of China (English)
Hongjuan Yang; Fangqiang Wei; Kaiheng Hu
2014-01-01
The mean velocity estimation of debris flows, especially viscous debris flows, is an impor-tant part in the debris flow dynamics research and in the design of control structures. In this study, theoretical equations for computing debris flow velocity with the one-phase flow assumption were re-viewed and used to analyze field data of viscous debris flows. Results show that the viscous debris flow is difficult to be classified as a Newtonian laminar flow, a Newtonian turbulent flow, a Bingham fluid, or a dilatant fluid in the strict sense. However, we can establish empirical formulas to compute its mean velocity following equations for Newtonian turbulent flows, because most viscous debris flows are tur-bulent. Factors that potentially influence debris flow velocity were chosen according to two-phase flow theories. Through correlation analysis and data fitting, two empirical formulas were proposed. In the first one, velocity is expressed as a function of clay content, flow depth and channel slope. In the second one, a coefficient representing the grain size nonuniformity is used instead of clay content. Both formu-las can give reasonable estimate of the mean velocity of the viscous debris flow.
Bulk viscous cosmology: statefinder and entropy
He, X
2006-01-01
The statefinder diagnostic pair is adopted to differentiate viscous cosmology models and it is found that the trajectories of these viscous cosmology models on the statefinder pair $s-r$ plane are quite different from those of the corresponding non-viscous cases. Particularly for the quiessence model, the singular properties of state parameter $w=-1$ are obviously demonstrated on the statefinder diagnostic pair planes. We then discuss the entropy of the viscous / dissipative cosmology system which may be more practical to describe the present cosmic observations as the perfect fluid is just a global approximation to the complicated cosmic media in current universe evolution. When the bulk viscosity takes the form of $\\zeta=\\zeta_{1}\\dot{a}/a$($\\zeta_{1}$ is constant), the relationship between the entropy $S$ and the redshift $z$ is explicitly given out. We find that the entropy of the viscous cosmology is always increasing and consistent with the thermodynamics arrow of time for the universe evolution. With t...
Oscillation death in coupled oscillators
Institute of Scientific and Technical Information of China (English)
Wei ZOU; Xin-gang WANG; Qi ZHAO; Meng ZHAN
2009-01-01
We study dynamical behaviors in coupled nonlinear oscillators and find that under certain condi- tions, a whole coupled oscillator system can cease oscil- lation and transfer to a globally nonuniform stationary state [I.e., the so-called oscillation death (OD) state], and this phenomenon can be generally observed. This OD state depends on coupling strengths and is clearly differ- ent from previously studied amplitude death (AD) state, which refers to the phenomenon where the whole system is trapped into homogeneously steady state of a fixed point, which already exists but is unstable in the ab- sence of coupling. For larger systems, very rich pattern structures of global death states are observed. These Turing-like patterns may share some essential features with the classical Turing pattern.
Directory of Open Access Journals (Sweden)
Asma Khalid
2015-01-01
Full Text Available The unsteady free flow of a Casson fluid past an oscillating vertical plate with constant wall temperature has been studied. The Casson fluid model is used to distinguish the non-Newtonian fluid behaviour. The governing partial differential equations corresponding to the momentum and energy equations are transformed into linear ordinary differential equations by using nondimensional variables. Laplace transform method is used to find the exact solutions of these equations. Expressions for shear stress in terms of skin friction and the rate of heat transfer in terms of Nusselt number are also obtained. Numerical results of velocity and temperature profiles with various values of embedded flow parameters are shown graphically and their effects are discussed in detail.
One-dimensional reduction of viscous jets
Pitrou, Cyril
2015-01-01
We build a general formalism to describe thin viscous jets as one-dimensional objects with an internal structure. We present in full generality the steps needed to describe the viscous jets around their central line, and we argue that the Taylor expansion of all fields around that line is conveniently expressed in terms of symmetric trace-free tensors living in the two dimensions of the fiber sections. We recover the standard results of axisymmetric jets and we report the first and second corrections to the lowest order description, also allowing for a rotational component around the axis of symmetry. When applied to generally curved fibers, the lowest order description corresponds to a viscous string model whose sections are circular. However, when including the first corrections we find that curved jets generically develop elliptic sections. Several subtle effects imply that the first corrections cannot be described by a rod model, since it amounts to selectively discard some corrections. However, in a fast...
Dynamics of amorphous solids and viscous liquids
DEFF Research Database (Denmark)
Dyre, Jeppe
-dependence of the average relaxation time in viscous liquids is proposed. In the new model, the short-time (or high-frequency) elastic properties of the liquid determine the activation energy for the average relaxation time. It is shown that the new model agrees well with experiment on a number of organic molecular liquids...... the brief paper P3, that is included in the thesis mainly because its figures are more pedagogical than those of P4. By means of analytical approximations it is shown that at sufficiently low temperatures - corresponding to extreme disorder - all disordered solids with thermally activated conduction exhibit......-Arrhenius temperature-dependence of the average relaxation time in viscous liquids, an approach that is also followed in Chapter 2. However, in P8 itself the focus was on the prediction that there are two different types of glass transitions. In P9 from 1995, B„ssler's random walk model for viscous liquids is studied...
Directory of Open Access Journals (Sweden)
G. Bellini
2014-01-01
Full Text Available In the last decades, a very important breakthrough has been brought about in the elementary particle physics by the discovery of the phenomenon of the neutrino oscillations, which has shown neutrino properties beyond the Standard Model. But a full understanding of the various aspects of the neutrino oscillations is far to be achieved. In this paper the theoretical background of the neutrino oscillation phenomenon is described, referring in particular to the paradigmatic models. Then the various techniques and detectors which studied neutrinos from different sources are discussed, starting from the pioneering ones up to the detectors still in operation and to those in preparation. The physics results are finally presented adopting the same research path which has been crossed by this long saga. The problems not yet fixed in this field are discussed, together with the perspectives of their solutions in the near future.
Nayfeh, Ali Hasan
1995-01-01
Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim
Freire, Joana G.; Cabeza, Cecilia; Marti, Arturo; Pöschel, Thorsten; Gallas, Jason A. C.
2013-06-01
The investigation of regular and irregular patterns in nonlinear oscillators is an outstanding problem in physics and in all natural sciences. In general, regularity is understood as tantamount to periodicity. However, there is now a flurry of works proving the existence of ``antiperiodicity'', an unfamiliar type of regularity. Here we report the experimental observation and numerical corroboration of antiperiodic oscillations. In contrast to the isolated solutions presently known, we report infinite hierarchies of antiperiodic waveforms that can be tuned continuously and that form wide spiral-shaped stability phases in the control parameter plane. The waveform complexity increases towards the focal point common to all spirals, a key hub interconnecting them all.
Kato, Shoji; Honma, Fumio; Matsumoto, Ryoji
1988-01-01
Viscous instability of the transonic region of the conventional geometrically thin alpha-type accretion disks is examined analytically. For simplicity, isothermal disks and isothermal perturbations are assumed. It is found that when the value of alpha is larger than a critical value the disk is unstable against two types of perturbations. One is local propagating perturbations of inertial acoustic waves. Results suggest the possibility that unstable perturbations develop to overstable global oscillations which are restricted only in the innermost region of the disk. The other is standing growing perturbations localized just at the transonic point. The cause of these instabilities is that the azimuthal component of the Lagrangian velocity variation associated with the perturbations becomes in phase with the variation of the viscous stress force. Because of this phase matching work is done on perturbations, and they are amplified.
2-D viscous magnetohydrodynamics simulation of plasma armatures with the CE/SE method
Institute of Scientific and Technical Information of China (English)
LI Xin; WENG ChunSheng
2009-01-01
A possible two-dimensional viscous magnetohydrodynamics (MHD) model is applied to investigating the plasma armature in a railgun. The space-time conservation element and solution element (CE/SE) method for solving the coupled Navier-Stokes equations and Maxwell equations was devised. The dis-tributions of physical parameters of the plasma may thus be evaluated. The results show that extremely high pressure can always be observed ahead of the projectile, and the Lorentz force is the main pro-puIsion. The distribution of temperature is in a good agreement with the results predicted by the law of radiation at the boundaries. Due to convection, the circulation patterns of velocity are evident in both the cases considering inviscid and viscous effect. Furthermore, the velocity and acceleration oscillate over time until a new steady state is achieved. This model efficiently captures the salient features of the physical phenomena, and contributes to further studies of MHD problems in plasma armature.
Bloch oscillations in a one-dimensional spinor gas.
Gangardt, D M; Kamenev, A
2009-02-20
A force applied to a spin-flipped particle in a one-dimensional spinor gas may lead to Bloch oscillations of the particle's position and velocity. The existence of Bloch oscillations crucially depends on the viscous friction force exerted by the rest of the gas on the spin excitation. We evaluate the friction in terms of the quantum fluid parameters. In particular, we show that the friction is absent for integrable cases, such as an SU(2) symmetric gas of bosons or fermions. For small deviations from the exact integrability the friction is very weak, opening the possibility to observe Bloch oscillations.
Linear oscillations of a drop in uniform alternating electric fields
Energy Technology Data Exchange (ETDEWEB)
Yang, Wenrui; Carleson, T.E.
1990-10-01
Oscillations of a conducting drop immersed in a dielectric fluid in an alternating electric field has been modelled in order to understand the enhancement of the transport processes by the electric field. Numerical solutions for oscillation amplitude, velocity distribution, resonant frequency and streamlines were obtained. The effects of viscosity and density on the resonant frequency and the velocity distribution were investigated. It was found that the resonant frequency of viscous fluids was always smaller than the free oscillation frequency of the same droplet. The predicted scanning frequency response curve and the streamlines agree well with the experimental observations.
Viscous Stability of Relativistic Keplerian Accretion Disks
Ghosh, P
1998-01-01
We investigate the viscous stability of thin, Keplerian accretion disks in regions where general relativistic (GR) effects are essential. For gas pressure dominated (GPD) disks, we show that the Newtonian conclusion that such disks are viscously stable is reversed by GR modifications in the behaviors of viscous stress and surface density over a significantly large annular region not far from the innermost stable orbit at $r=\\rms$. For slowly-rotating central objects, this region spans a range of radii $14\\lo r\\lo 19$ in units of the central object's mass $M$. For radiation pressure dominated (RPD) disks, the Newtonian conclusion that they are viscously unstable remains valid after including the above GR modifications, except in a very small annulus around $r\\approx 14M$, which has a negligible influence. Inclusion of the stabilizing effect of the mass-inflow through the disk's inner edge via a GR analogue of Roche-lobe overflow adds a small, stable region around \\rms~for RPD disks, but leaves GPD disks unchan...
Viscous fingering with partial miscible fluids
Fu, Xiaojing; Cueto-Felgueroso, Luis; Juanes, Ruben
2015-11-01
When a less viscous fluid displaces a more viscous fluid, the contrast in viscosity destabilizes the interface between the two fluids, leading to the formation of fingers. Studies of viscous fingering have focused on fluids that are either fully miscible or perfectly immiscible. In practice, however, the miscibility of two fluids can change appreciably with temperature and pressure, and often falls into the case of partial miscibility, where two fluids have limited solubility in each other. Following our recent work for miscible (Jha et al., PRL 2011, 2013) and immiscible systems (Cueto-Felgueroso and Juanes, PRL 2012, JFM 2014), here we propose a phase-field model for fluid-fluid displacements in a Hele-Shaw cell, when the two fluids have limited (but nonzero) solubility in one another. Partial miscibility is characterized through the design of thermodynamic free energy of the two-fluid system. We elucidate the key dimensionless groups that control the behavior of the system. We present high-resolution numerical simulations of the model applied to the viscous fingering problem. On one hand, we demonstrate the effect of partial miscibility on the hydrodynamic instability. On the other, we elucidate the role of the degree of fingering on the rate of mutual fluid dissolution.
Viscous fingering with partially miscible fluids
Fu, X.; Cueto-Felgueroso, L.; Juanes, R.
2015-12-01
When a less viscous fluid displaces a more viscous fluid, the contrast in viscosity destabilizes the interface between the two fluids, leading to the formation of fingers. Experimental and numerical studies of viscous fingering have focused on fluids that are either fully miscible (e.g. water and glycerol) or perfectly immiscible (e.g. water and oil). In practice, however, the miscibility of two fluids can change appreciably with temperature and pressure, and often falls into the case of partial miscibility, where two fluids have limited solubility in each other (e.g. CO2 and water). Following our recent work for miscible systems (Jha et al., PRL 2011, 2013) and immiscible systems (Cueto-Felgueroso and Juanes, PRL 2012, JFM 2014), here we propose a phase-field model for fluid-fluid displacements in a porous medium, when the two fluids have limited (but nonzero) solubility in one another. In our model, partial miscibility is characterized through the design of the thermodynamic free energy of the two-fluid system. We express the model in dimensionless form and elucidate the key dimensionless groups that control the behavior of the system. We present high-resolution numerical simulations of the model applied to the viscous fingering problem. On one hand, we demonstrate the effect of partial miscibility on the hydrodynamic instability. On the other, we elucidate the role of the degree of fingering on the rate of mutual fluid dissolution. Figure caption: final snapshots in simulations of viscous fingering with a two-fluid system mimicking that of CO2 and water. The colormap corresponds to the concentration of CO2. A band of less viscous gas phase rich in CO2 (red) displaces through the more viscous liquid phase that is undersaturated with CO2 (blue). At the fluid interface, an exchange of CO2 occurs as a result of local chemical potentials that drives the system towards thermodynamic equilibrium. This results in a shrinkage of gas phase as well as a local increase in
Stokes’ and Lamb's viscous drag laws
Eames, I.; Klettner, C. A.
2017-03-01
Since Galileo used his pulse to measure the time period of a swinging chandelier in the 17th century, pendulums have fascinated scientists. It was not until Stokes' (1851 Camb. Phil. Soc. 9 8-106) (whose interest was spurred by the pendulur time pieces of the mid 19th century) treatise on viscous flow that a theoretical framework for the drag on a sphere at low Reynolds number was laid down. Stokes' famous drag law has been used to determine two fundamental physical constants—the charge on an electron and Avogadro's constant—and has been used in theories which have won three Nobel prizes. Considering its illustrious history it is then not surprising that the flow past a sphere and its two-dimensional analog, the flow past a cylinder, form the starting point of teaching flow past a rigid body in undergraduate level fluid mechanics courses. Usually starting with the two-dimensional potential flow past a cylinder, students progress to the three-dimensional potential flow past a sphere. However, when the viscous flow past rigid bodies is taught, the three-dimensional example of a sphere is first introduced, and followed by (but not often), the two-dimensional viscous flow past a cylinder. The reason why viscous flow past a cylinder is generally not taught is because it is usually explained from an asymptotic analysis perspective. In fact, this added mathematical complexity is why the drag on a cylinder was only solved in 1911, 60 years after the drag on a sphere. In this note, we show that the viscous flow past a cylinder can be explained without the need to introduce any asymptotic analysis while still capturing all the physical insight of this classic fluid mechanics problem.
Runge-Kutta methods and viscous wave equations
J.G. Verwer (Jan)
2008-01-01
htmlabstractWe study the numerical time integration of a class of viscous wave equations by means of Runge-Kutta methods. The viscous wave equation is an extension of the standard second-order wave equation including advection-diffusion terms differentiated in time. The viscous wave equation can be
Runge–Kutta methods and viscous wave equations
J.G. Verwer (Jan)
2009-01-01
htmlabstractWe study the numerical time integration of a class of viscous wave equations by means of Runge–Kutta methods. The viscous wave equation is an extension of the standard second-order wave equation including advection–diffusion terms differentiated in time. The viscous wave equation can be
Hall effects on hydromagnetic flow on an oscillating porous plate
Institute of Scientific and Technical Information of China (English)
S.L. Maji; A.K. Kanch; M. Guria; R.N. Jana
2009-01-01
In this paper, an analysis is made on the unsteady flow of an incompressible electrically conducting viscous fluid bounded by an infinite porous flat plate. The plate executes harmonic oscillations at a frequency n in its own plane. A uniform magnetic field H0 is imposed perpendicular to the direction of the flow. It is found that the solution also exists for blowing at the plate. The temperature distribution is also obtained by taking viscous and Joule dissipation into account. The mean wall temperature 00(0) decreases with the increase in the Hall parameter m. It is found that no temperature distribution exists for the blowing at the plate.
Cochlear perfusion with a viscous fluid.
Wang, Yi; Olson, Elizabeth S
2016-07-01
The flow of viscous fluid in the cochlea induces shear forces, which could provide benefit in clinical practice, for example to guide cochlear implant insertion or produce static pressure to the cochlear partition or wall. From a research standpoint, studying the effects of a viscous fluid in the cochlea provides data for better understanding cochlear fluid mechanics. However, cochlear perfusion with a viscous fluid may damage the cochlea. In this work we studied the physiological and anatomical effects of perfusing the cochlea with a viscous fluid. Gerbil cochleae were perfused at a rate of 2.4 μL/min with artificial perilymph (AP) and sodium hyaluronate (Healon, HA) in four different concentrations (0.0625%, 0.125%, 0.25%, 0.5%). The different HA concentrations were applied either sequentially in the same cochlea or individually in different cochleae. The perfusion fluid entered from the round window and was withdrawn from basal scala vestibuli, in order to perfuse the entire perilymphatic space. Compound action potentials (CAP) were measured after each perfusion. After perfusion with increasing concentrations of HA in the order of increasing viscosity, the CAP thresholds generally increased. The threshold elevation after AP and 0.0625% HA perfusion was small or almost zero, and the 0.125% HA was a borderline case, while the higher concentrations significantly elevated CAP thresholds. Histology of the cochleae perfused with the 0.0625% HA showed an intact Reissner's membrane (RM), while in cochleae perfused with 0.125% and 0.25% HA RM was torn. Thus, the CAP threshold elevation was likely due to the broken RM, likely caused by the shear stress produced by the flow of the viscous fluid. Our results and analysis indicate that the cochlea can sustain, without a significant CAP threshold shift, up to a 1.5 Pa shear stress. Beside these finding, in the 0.125% and 0.25% HA perfusion cases, a temporary CAP threshold shift was observed, perhaps due to the presence and
Cochlear perfusion with a viscous fluid
Wang, Yi; Olson, Elizabeth S.
2016-01-01
The flow of viscous fluid in the cochlea induces shear forces, which could provide benefit in clinical practice, for example to guide cochlear implant insertion or produce static pressure to the cochlear partition or wall. From a research standpoint, studying the effects of a viscous fluid in the cochlea provides data for better understanding cochlear fluid mechanics. However, cochlear perfusion with a viscous fluid may damage the cochlea. In this work we studied the physiological and anatomical effects of perfusing the cochlea with a viscous fluid. Gerbil cochleae were perfused at a rate of 2.4 μL/min with artificial perilymph (AP) and sodium hyaluronate (Healon, HA) in four different concentrations (0.0625%, 0.125%, 0.25%, 0.5%). The different HA concentrations were applied either sequentially in the same cochlea or individually in different cochleae. The perfusion fluid entered from the round window and was withdrawnfrom basal scala vestibuli, in order to perfuse the entire perilymphatic space. Compound action potentials (CAP) were measured after each perfusion. After perfusion with increasing concentrations of HA in the order of increasing viscosity, the CAP thresholds generally increased. The threshold elevation after AP and 0.0625% HA perfusion was small or almost zero, and the 0.125% HA was a borderline case, while the higher concentrations significantly elevated CAP thresholds. Histology of the cochleae perfused with the 0.0625% HA showed an intact Reissner’s membrane, while in cochleae perfused with 0.125% and 0.25% HA Reissner’s membrane (RM) was torn. Thus, the CAP threshold elevation was likely due to the broken of RM, which likely caused by the shear stress produced by the flow of the viscous fluid. Our results and analysis indicate that the cochlea can sustain, without a significant CAP threshold shift, up to a 1.5 Pa shear stress. Beside these finding, in the 0.125% and 0.25% HA perfusion cases, a temporary CAP threshold shift was observed
Dumbser, Michael; Peshkov, Ilya; Romenski, Evgeniy; Zanotti, Olindo
2016-06-01
This paper is concerned with the numerical solution of the unified first order hyperbolic formulation of continuum mechanics recently proposed by Peshkov and Romenski [110], further denoted as HPR model. In that framework, the viscous stresses are computed from the so-called distortion tensor A, which is one of the primary state variables in the proposed first order system. A very important key feature of the HPR model is its ability to describe at the same time the behavior of inviscid and viscous compressible Newtonian and non-Newtonian fluids with heat conduction, as well as the behavior of elastic and visco-plastic solids. Actually, the model treats viscous and inviscid fluids as generalized visco-plastic solids. This is achieved via a stiff source term that accounts for strain relaxation in the evolution equations of A. Also heat conduction is included via a first order hyperbolic system for the thermal impulse, from which the heat flux is computed. The governing PDE system is hyperbolic and fully consistent with the first and the second principle of thermodynamics. It is also fundamentally different from first order Maxwell-Cattaneo-type relaxation models based on extended irreversible thermodynamics. The HPR model represents therefore a novel and unified description of continuum mechanics, which applies at the same time to fluid mechanics and solid mechanics. In this paper, the direct connection between the HPR model and the classical hyperbolic-parabolic Navier-Stokes-Fourier theory is established for the first time via a formal asymptotic analysis in the stiff relaxation limit. From a numerical point of view, the governing partial differential equations are very challenging, since they form a large nonlinear hyperbolic PDE system that includes stiff source terms and non-conservative products. We apply the successful family of one-step ADER-WENO finite volume (FV) and ADER discontinuous Galerkin (DG) finite element schemes to the HPR model in the stiff
Viscous warm inflation: Hamilton-Jacobi formalism
Akhtari, L.; Mohammadi, A.; Sayar, K.; Saaidi, Kh.
2017-04-01
Using Hamilton-Jacobi formalism, the scenario of warm inflation with viscous pressure is considered. The formalism gives a way of computing the slow-rolling parameter without extra approximation, and it is well-known as a powerful method in cold inflation. The model is studied in detail for three different cases of the dissipation and bulk viscous pressure coefficients. In the first case where both coefficients are taken as constant, it is shown that the case could not portray warm inflationary scenario compatible with observational data even it is possible to restrict the model parameters. For other cases, the results shows that the model could properly predicts the perturbation parameters in which they stay in perfect agreement with Planck data. As a further argument, r -ns and αs -ns are drown that show the acquired result could stand in acceptable area expressing a compatibility with observational data.
Solidity of viscous liquids. IV. Density fluctuations
DEFF Research Database (Denmark)
Dyre, J. C.
2006-01-01
This paper is the fourth in a series exploring the physical consequences of the solidity of highly viscous liquids. It is argued that the two basic characteristics of a flow event (a jump between two energy minima in configuration space) are the local density change and the sum of all particle...... displacements. Based on this it is proposed that density fluctuations are described by a time-dependent Ginzburg-Landau equation with rates in k space of the form C+Dk^2 with D>>C a^2 where a is the average intermolecular distance. The inequality expresses a long-wavelength dominance of the dynamics which...... with Debye behavior at low frequencies and an omega^{−1/2} decay of the loss at high frequencies. Finally, a general formalism for the description of viscous liquid dynamics, which supplements the density dynamics by including stress fields, a potential energy field, and molecular orientational fields...
Viscous fluid dynamics in Au+Au collisions at RHIC
Chaudhuri, A K
2008-01-01
We have studied the space-time evolution of minimally viscous ($\\frac{\\eta}{s}$=0.08) QGP fluid, undergoing boost-invariant longitudinal motion and arbitrary transverse expansion. Relaxation equations for the shear stress tensor components, derived from the phenomenological Israel-Stewart's theory of dissipative relativistic fluid, are solved simultaneously with the energy-momentum conservation equations. Comparison of evolution of ideal and viscous fluid, both initialized under the similar conditions, e.g. same equilibration time, energy density and velocity profile, indicate that in viscous fluid, energy density or temperature of the fluid evolve slowly than in an ideal fluid. Transverse expansion is also more in viscous evolution. We have also studied particle production in viscous dynamics. Compared to ideal dynamics, in viscous dynamics, particle yield at high $p_T$ is increased. Elliptic flow on the other hand decreases. Minimally viscous QGP fluid, initialized at entropy density $s_{ini}$=110 $fm^{-3}$...
Viscous Glass Sealants for SOFC Applications
Energy Technology Data Exchange (ETDEWEB)
Scott Misture
2012-09-30
Two series of silicate glasses that contain gallium as the primary critical component have been identified and optimized for viscous sealing of solid oxide fuel cells operating from 650 to 850Â°C. Both series of glass sealants crystallize partially upon heat treatment and yield multiphase microstructures that allow viscous flow at temperatures as low as 650Â°C. A fully amorphous sealant was also developed by isolating, synthesizing and testing a silicate glass of the same composition as the remnant glassy phase in one of the two glass series. Of ~40 glasses tested for longer than 500 hours, a set of 5 glasses has been further tested for up to 1000h in air, wet hydrogen, and against both yttria-stabilized zirconia and aluminized stainless steel. In some cases the testing times reached 2000h. The reactivity testing has provided new insight into the effects of Y, Zr, and Al on bulk and surface crystallization in boro-gallio-silicate glasses, and demonstrated that at least 5 of the newly-developed glasses are viable viscous sealants.
Periodic massloss from viscous accretion flows around black holes
Das, Santabrata; Nandi, Anuj; Molteni, Diego
2014-01-01
We investigate the behaviour of low angular momentum viscous accretion flows around black holes using Smooth Particle Hydrodynamics (SPH) method. Earlier, it has been observed that in a significant part of the energy and angular momentum parameter space, rotating transonic accretion flow undergoes shock transition before entering in to the black hole and a part of the post-shock matter is ejected as bipolar outflows, which are supposed to be the precursor of relativistic jets. In this work, we simulate accretion flows having injection parameters from the inviscid shock parameter space, and study the response of viscosity on them. With the increase of viscosity, shock becomes time dependent and starts to oscillate when the viscosity parameter crosses its critical value. As a result, the in falling matter inside the post-shock region exhibits quasi-periodic variations and causes periodic ejection of matter from the inner disc as outflows. In addition, the same hot and dense post-shock matter emits high energy r...
Institute of Scientific and Technical Information of China (English)
丁立; 郑强
2015-01-01
在考虑半对数应力应变关系的基础上，引入非牛顿指数描述的非达西渗流模型，建立一维固结方程，采用有限差分法求其数值解，并与Terzaghi解答和Davis解答对比验证数值方法的有效性。据此，分析土体应力应变非线性和渗流的非达西特性对饱和粘土一维固结的影响。结果表明，非牛顿指数i0越大，土层厚度与地基平均竖向总应力的等效水头的比值越大，固结速率越低；地面荷载越大，孔压消散速率和地基沉降速率都越快，按沉降定义的固结度要略大于按孔压定义的固结度；压缩指数与渗透指数的比值越大，固结速率越慢；初始有效应力越大，固结速率越快。%Considering Davis’s semilog stress-strain relationship,we introducce non Newtonian index to describe non-darcy seepage flow model,and derive the one-dimensional consolidation equation. And its numerical solution analysis is performed by using the finite difference method. In order to verify the effectiveness of the numerical method,the calculating solution by the present method is compared with the analytical solution based on the nonlinear consolidation theory proposed by Davis and Raymond. Accordingly,the effect of stress and strain nonlinearity of soil and seepage non-Darcy characteristics on one-dimensional consolidation of saturated clay is analyzed. The results show that the greater the non-Newtonian index i0 is,the greater the equivalent head ration of soil layer thickness and the foundation of the total average vertical stress would be,and the consolidation rate is lower is. The greater the ground load is,the greater the pore pressure dissipation rate and ground subsidence rate would be. The definition of degree of consolidation by settlement is slightly greater than the definition of degree of consolidation by pore water pressure. The greater the ratio of compression and penetration index is ,the slower the consolidation
Drop Impact of Viscous Suspensions on Solid Surfaces
Bolleddula, Daniel; Aliseda, Alberto
2009-11-01
Droplet impact is a well studied subject with over a century of progress. Most studies are motivated by applications such as inkjet printing, agriculture spraying, or printed circuit boards. Pharmaceutically relevant fluids provide an experimental set that has received little attention. Medicinal tablets are coated by the impaction of micron sized droplets of aqueous suspensions and subsequently dried for various purposes such as brand recognition, mask unpleasant taste, or functionality. We will present a systematic study of micron sized drop impact of Newtonian and Non-Newtonian fluids used in pharmaceutical coating processes. In our experiments we extend the range of Ohnesorge numbers, O(1), of previous studies on surfaces of varying wettability and roughness.
Pirnia, Alireza; Hu, Jiacheng; Peterson, Sean; Erath, Byron
2016-11-01
Energy can be extracted from flow instabilities in the environment for powering low consumption devices. When vortices pass tangentially over a flexible beam the lower pressure in the vortex core causes the beam to deflect, and induces sustained oscillations which can be converted into energy via piezoelectric materials. The beam dynamics can be parameterized according to the beam properties (nondimensional mass and stiffness ratios) as well as the vortex properties (size, vortex circulation strength and advection velocity). Recently, inviscid models have been developed to solve this fluid-structure interaction problem but they do not capture viscous interactions; features that become more prominent when the beam is positioned close to the vortex core. In this study the interaction of a vortex ring passing tangentially over a flexible beam as a function of circulation strength, beam properties, and offset distance are investigated to identify how viscous interactions influence the energy exchange process. Particle image velocimetry is acquired in tandem with the beam dynamics. The velocity and pressure fields, and transient beam dynamics are compared and contrasted with an inviscid model to identify the role of viscous interactions. This work was supported by the National Science Foundation Grant CBET #1511761.
Numerical investigation of interaction between rising bubbles in a viscous liquid
Energy Technology Data Exchange (ETDEWEB)
Yoon, Ik Roh [Korea Institute of Marine Science and Technology Promotion, Seoul (Korea, Republic of); Shin Seung Won [Hongik University, Seoul (Korea, Republic of)
2016-07-15
The rising behavior of bubbles undergoing bubble-bubble interaction in a viscous liquid is studied using a two-dimensional direct numerical simulation. Level contour reconstruction method (LCRM), one of the connectivity-free front tracking methods, is applied to describe a moving interface accurately under highly deformable conditions. This work focuses on the effects of bubble size on the interaction of two bubbles rising side-by-side in a stagnant liquid. Several characteristics of bubble-bubble interaction are analyzed quantitatively as supported by energy analysis. The results showed clear differences between small and large bubbles with respect to their interaction behavior in terms of lateral movement, vortex intensity, suppression of surface deformation, and viscous dissipation rate. Distributions of vorticity and viscous dissipation rate near the bubble interfaces also differed depending on the size of the bubbles. Strong vortices from large bubbles triggered oscillation in bubble-bubble interaction and played a dominant role in the interaction process as the size of bubbles increases.
Dynamics of sessile drops. Part 3. Theory of forced oscillations
Bostwick, Joshua B
2016-01-01
A partially-wetting sessile drop is driven by a sinusoidal pressure field that produces capillary waves on the liquid/gas interface. The analysis presented in Part 1 of this series (Bostwick & Steen 2014) is extended by computing response diagrams and phase shifts for the viscous droplet, whose three phase contact-line moves with contact-angle that is a smooth function of the contact line speed. Viscous dissipation is incorporated through the viscous potential flow approximation and the critical Ohnesorge number bounding regions beyond which a given mode becomes over-damped is computed. Davis dissipation originating from the contact-line speed condition leads to damped oscillations for drops with finite contact-line mobility, even for inviscid fluids. The critical mobility and associated driving frequency to generate the largest Davis dissipation is computed. Lastly, regions of modal coexistence where two modes can be simultaneously excited by a single forcing frequency are identified. Predictions compare...