non-Newtonian Fluids (non-newtonian + fluid)

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Distribution within Chemistry

Terms modified by non-Newtonian Fluids

  • non-newtonian fluid flow

  • Selected Abstracts


    Flow and mass transfer of fully resolved bubbles in non-Newtonian fluids

    AICHE JOURNAL, Issue 7 2007
    Stefan Radl
    Abstract In this work, high-resolution 2-D numerical simulations were performed on the motion of deformable bubbles in non-Newtonian fluids and the associated mass transfer. For that purpose, we have implemented a semi-Lagrangian advection scheme and improved the fluid dynamic calculation by the usage of implicit algorithms. Non-Newtonian fluids are described by generalized Newtonian as well as viscoelastic model fluids. As shear-thinning model we use a Power-Law and a Carreau-Yasuda model, the viscoelastic fluid simulations are based on an Upper-Convected Maxwell model combined with a recently introduced model for the evolution of the effective shear rate. The mathematical challenges arising from the hyperbolic nature of the resulting set of equations are addressed by inclusion of artificial diffusion in the stress equation. In our work, it was found that shear thinning effects have impact on collision rates, and therefore, may influence coalescence of bubbles in non-Newtonian liquids. Furthermore, for the first time, concentration fields of dissolved gas in viscoelastic fluids are presented. The study shows that the fluid elasticity plays a major role for bubble rise velocity, and therefore, mass transfer. As the wake dynamics differ significantly from that in Newtonian liquids, abnormal mixing characteristics can be expected in the bubbly flow of viscoelastic fluids. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source]


    Numerical simulation of two-dimensional transient water driven non-Newtonian fluid flow in porous media

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2002
    Zuojin Zhu
    Abstract Numerical simulation of two-dimensional transient water driven non-Newtonian fluid flow in porous media has been performed. The hyperbolic non-Newtonian fluid model was used to describe the characteristics of non-Newtonian fluid flow. Governing equations were first approximated by implicit finite difference, and then solved by a stabilized bi-conjugate gradient (Bi-CGSTAB) approach. A comparison of the numerical results for the case of water driven Newtonian fluid was made to validate the numerical method. For water driven Newtonian fluid flow, it was found that the numerical results are satisfactorily consistent with those obtained by commercial software VIP which is the abbreviation of vector implicit procedure for numerical simulation of Newtonian fluid flow in porous media. The maximum deviation for average pressure is less than 1.5 per cent; the distribution of water saturation is almost the same as that obtained by VIP. For water driven non-Newtonian fluid flow in porous media, it was found that the factor of pressure gradient of the non-Newtonian fluid has significant effects on the process of oil recovery. The correction of numerical simulation based on the global mass balance plays an important role in oil reservoir simulation. Copyright © 2002 John Wiley & Sons, Ltd. [source]


    Artificial boundary conditions for viscoelastic flows

    MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 8 2008
    Sergueï A. Nazarov
    Abstract The steady three-dimensional exterior flow of a viscoelastic non-Newtonian fluid is approximated by reducing the corresponding nonlinear elliptic,hyperbolic system to a bounded domain. On the truncation surface with a large radius R, nonlinear, local second-order artificial boundary conditions are constructed and a new concept of an artificial transport equation is introduced. Although the asymptotic structure of solutions at infinity is known, certain attributes cannot be found explicitly so that the artificial boundary conditions must be constructed with incomplete information on asymptotics. To show the existence of a solution to the approximation problem and to estimate the asymptotic precision, a general abstract scheme, adapted to the analysis of coupled systems of elliptic,hyperbolic type, is proposed. The error estimates, obtained in weighted Sobolev norms with arbitrarily large smoothness indices, prove an approximation of order O(R,2+,), with any ,>0. Our approach, in contrast to other papers on artificial boundary conditions, does not use the standard assumptions on compactly supported right-hand side f, leads, in particular, to pointwise estimates and provides error bounds with constants independent of both R and f. Copyright © 2007 John Wiley & Sons, Ltd. [source]


    Mixed convection flow of non-Newtonian fluid from a slotted vertical surface with uniform surface heat flux

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009
    Rama Subba Reddy Gorla
    Abstract In the present paper, the combined convection flow of an Ostwald,de Waele type power-law non-Newtonian fluid past a vertical slotted surface has been investigated numerically. The boundary condition of uniform surface heat flux is considered. The equations governing the flow and the heat transfer are reduced to local non-similarity form. The transformed boundary layer equations are solved numerically using implicit finite difference method. Solutions for the heat transfer rate obtained for the rigid surface compare well with those documented in the published literature. From the present analysis, it is observed that, an increase in , leads to increase in skin friction as well as reduction in heat transfer at the surface. As the power-law index n increases, the friction factor as well as heat transfer increase. Dans cet article, on a étudié numériquement l'écoulement de convection combinée d'un fluide non-newtonien de loi de puissance de type Ostwald-de Waele en aval d'une surface perforée verticale. La condition limite d'un flux de chaleur de surface uniforme est considérée. Les équations gouvernant l'écoulement et le transfert de chaleur sont réduites à la forme de non-similarité locale. Les équations de couche limite transformées sont résolues numériquement par la méthode des différences finies implicites. Les solutions pour la vitesse de transfert de chaleur obtenues pour la surface rigide se comparent bien à celles qui sont décrites dans la littérature scientifique publiée. À partir de la présente analyse, on observe qu'une augmentation de , mène à une augmentation du frottement superficiel ainsi qu'à une réduction du transfert de chaleur à la surface. Lorsque l'indice de loi de puissance n augmente, le facteur de friction et le transfert de chaleur augmentent également. [source]


    CFD simulation of non-Newtonian fluid flow in anaerobic digesters

    BIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008
    Binxin Wu
    Abstract 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-, 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. Biotechnol. Bioeng. 2008;99: 700,711. © 2007 Wiley Periodicals, Inc. [source]


    NEURAL NETWORK MODELING OF END-OVER-END THERMAL PROCESSING OF PARTICULATES IN VISCOUS FLUIDS

    JOURNAL OF FOOD PROCESS ENGINEERING, Issue 2010
    YANG MENG
    ABSTRACT Modeling of the heat transfer process in thermal processing is important for the process design and control. Artificial neural networks (ANNs) have been used in recent years in heat transfer modeling as a potential alternative to conventional dimensionless correlation approach and shown to be even better performers. In this study, ANN models were developed for apparent heat transfer coefficients associated with canned particulates in high viscous Newtonian and non-Newtonian fluids during end-over-end thermal processing in a pilot-scale rotary retort. A portion of experimental data obtained for the associated heat transfer coefficients were used for training while the rest were used for testing. The principal configuration parameters were the combination of learning rules and transfer functions, number of hidden layers, number of neurons in each hidden layer and number of learning runs. For the Newtonian fluids, the optimal conditions were two hidden layers, five neurons in each hidden layer, the delta learning rule, a sine transfer function and 40,000 learning runs, while for the non-Newtonian fluids, the optimal conditions were one hidden layer, six neurons in each hidden layer, the delta learning rule, a hyperbolic tangent transfer function and 50,000 learning runs. The prediction accuracies for the ANN models were much better compared with those from the dimensionless correlations. The trained network was found to predict responses with a mean relative error of 2.9,3.9% for the Newtonian fluids and 4.7,5.9% for the non-Newtonian fluids, which were 27,62% lower than those associated with the dimensionless correlations. Algebraic solutions were included, which could be used to predict the heat transfer coefficients without requiring an ANN. PRACTICAL APPLICATIONS The artificial neural network (ANN) model is a network of computational elements that was originally developed to mimic the function of the human brain. ANN models do not require the prior knowledge of the relationship between the input and output variables because they can discover the relationship through successive training. Moreover, ANN models can predict several output variables at the same time, which is difficult in general regression methods. ANN concepts have been successfully used in food processing for prediction, quality control and pattern recognition. ANN models have been used in recent years for heat transfer modeling as a potential alternative to conventional dimensionless correlation approach and shown to be even better performers. In this study, ANN models were successfully developed for the heat transfer parameters associated with canned particulate high viscous Newtonian and non-Newtonian fluids during an end-over-end rotation thermal processing. Optimized configuration parameters were obtained by choosing appropriate combinations of learning rule, transfer function, learning runs, hidden layers and number of neurons. The trained network was found to predict parameter responses with mean relative errors considerably lower than from dimensionless correlations. [source]


    IN-LINE CONSISTENCY MONITORING OF TOMATO BASED PRODUCTS USING VIBRATIONAL PROCESS VISCOMETRY

    JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2001
    P. J. CULLEN
    A vibrational process viscometer was evaluated as an in-line consistency monitoring technique for tomato based products. This sensor was installed in both pilot and industry scale production processes. Accuracy of the sensor and its ability to distinguish between varying concentrations of non-Newtonian fluids was evaluated with flowrate and temperature closely controlled. The sensor was shown to have the least inherent variability when compared to off-line techniques. However it was found to be flowrate dependent for the tomato based products. Good correlations between the sensor and off-line techniques were developed for the pilot scale trials. Plant trials revealed a number of problems in developing such correlations under industrial process conditions, however the instrument proved capable of tracking out of specification sauce as determined by the off-line Brookfield viscometer. It was concluded that use of the sensor would result in increased measurement precision over the off-line instruments coupled with the benefits of in-line monitoring. [source]


    Flow and mass transfer of fully resolved bubbles in non-Newtonian fluids

    AICHE JOURNAL, Issue 7 2007
    Stefan Radl
    Abstract In this work, high-resolution 2-D numerical simulations were performed on the motion of deformable bubbles in non-Newtonian fluids and the associated mass transfer. For that purpose, we have implemented a semi-Lagrangian advection scheme and improved the fluid dynamic calculation by the usage of implicit algorithms. Non-Newtonian fluids are described by generalized Newtonian as well as viscoelastic model fluids. As shear-thinning model we use a Power-Law and a Carreau-Yasuda model, the viscoelastic fluid simulations are based on an Upper-Convected Maxwell model combined with a recently introduced model for the evolution of the effective shear rate. The mathematical challenges arising from the hyperbolic nature of the resulting set of equations are addressed by inclusion of artificial diffusion in the stress equation. In our work, it was found that shear thinning effects have impact on collision rates, and therefore, may influence coalescence of bubbles in non-Newtonian liquids. Furthermore, for the first time, concentration fields of dissolved gas in viscoelastic fluids are presented. The study shows that the fluid elasticity plays a major role for bubble rise velocity, and therefore, mass transfer. As the wake dynamics differ significantly from that in Newtonian liquids, abnormal mixing characteristics can be expected in the bubbly flow of viscoelastic fluids. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source]


    THE USE OF TOMATO PULP POWDER AS A THICKENING AGENT IN THE FORMULATION OF TOMATO KETCHUP

    JOURNAL OF TEXTURE STUDIES, Issue 2 2008
    A. FARAHNAKY
    ABSTRACT In this current study, tomato pulp powder, the main waste of the tomato processing industry, was used as a thickening agent in the formulation of a commercial tomato ketchup at different levels (1, 2, 5, 7 and 10% w/w). Color parameters (L and a/b) and rheologic properties of the formulated ketchups with and without added tomato pulp powder were determined and compared. The addition of the pulp powder caused a significant increase in the L value of the samples, while a/b ratio decreased notably. The rheologic data obtained were fitted using a power law equation. The analysis of the data obtained revealed that low levels of tomato pulp powder can compete with other hydrocolloids in improving the consistency of tomato ketchup. All ketchup samples in this study were non-Newtonian fluids and the apparent viscosity of the ketchups increased significantly with increasing concentration of tomato pulp powder and decreased with temperature increase. Chemical composition (protein, total fat, reducing and total sugars, fiber, ascorbic acid and ash contents) and some physicochemical properties of the tomato pulp powder, including water absorption and solubility, were determined and the data were used for the interpretation of the rheologic and color changes as a result of the inclusion of the pulp powder in the formulation. PRACTICAL APPLICATIONS The direct use of food industry wastes in food formulations can help in reducing the production costs by decreasing raw material and disposal costs. The classic design of the tomato processing plants results in generating a large amount of tomato pulp. The results of this research confirmed that tomato pulp powder can be used instead of other hydrocolloids in tomato-based products. The reuse of tomato pulp powder in foods can be beneficial to producers and the environment. [source]


    Dynamic and capillary rheology of LDPE-EVA,based thermoplastic elastomer: Effect of silica nanofiller

    POLYMER COMPOSITES, Issue 3 2010
    Shalmali Hui
    The effect of pristine silica nanoparticles on the dynamic and capillary rheology of a model LDPE-EVA thermoplastic elastomeric system is explored in this paper. The pristine silica nanoparticles were melt-blended with the LDPE-EVA system at 1.5, 3, and 5 wt% loadings, respectively, by varying the sequence of addition. In one of the compositions, coupling agent bis-[3-(triethoxysilyl)propyl] tetrasulphide (Si-69) was used to improve the interaction of hydrophilic silica particles with polymer matrix. Results obtained reveal that the viscoelastic behavior of such composites is influenced remarkably by loadings of silica, variation of sequence, and addition of Si-69. Upon addition of coupling agent, G, value increases especially at higher strain levels due to increased polymer-filler interactions. All systems with various loading of nanosilica represent an increase in elastic response with increasing frequency. Both the unfilled and filled blends exhibit rheological behavior of non-Newtonian fluids. But interestingly, the viscoelastic response varies markedly with the temperature. The dynamic and steady shear rheological properties register a good correlation in regard to the viscous vs. elastic response of such systems. Finally, the rheological behavior is correlated with morphology of the present system processed at various shear rates. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source]


    Flow of Newtonian and power law liquids in tube bundles

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009
    U. K. Singh
    Abstract In this work, the annular (tangential) flow of Newtonian and non-Newtonian fluids in tube bundles has been studied experimentally. Extensive pressure drop data has been obtained embracing wide ranges of the Reynolds number (13,6600) and for two test modules of different geometrical arrangements, but of similar overall void fraction. Preliminary experiments suggest that the pressure drop is mainly determined by the overall void fraction of the bundle and is relatively insensitive to the detailed geometrical configuration of the bundle. A simple predictive correlation has been developed which reconciles the present results for Newtonian and power law fluids with acceptable levels of reliability. Dans le cadre de ces travaux, on a examiné de façon expérimentale l'écoulement annulaire (tangentiel) des fluides newtoniens et non newtoniens dans des faisceaux tubulaires. On a obtenu de nombreuses données de chute de pression englobant de vastes plages du nombre de Reynolds (13-6600), et pour deux modules d'essai de différentes dispositions géométriques, mais à taux de vide global similaire. Les expériences préliminaires suggèrent que la chute de pression est déterminée principalement par le taux de vide global du faisceau et est relativement insensible à la configuration géométrique détaillée du faisceau. La création d'une simple corrélation prédictive a permis de rapprocher les présents résultats pour les fluides newtoniens et des fluides en loi de puissance avec des niveaux acceptables de fiabilité. [source]


    Centrifugal pump performance calculation for homogeneous suspensions

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009
    L. J. W. Graham
    Abstract Centrifugal pumps are widely used for transporting suspensions, but their head performance is derated when non-Newtonian fluids and/or coarse solids are present. Some head deration methods are available for high viscosity Newtonian fluids, Bingham plastic fluids and for coarse solids in water. This paper presents a modification of the Hydraulic Institute head deration method that is suitable for any homogeneous non-Newtonian rheology. A modification of the Walker and Goulas method is also considered. Possible anomalous behaviour of kaolin slurries in centrifugal pumps is discussed. On utilise couramment des pompes centrifuges pour le transport de suspensions, mais le rendement de leur hauteur de charge est réduit en présence de fluides non newtoniens et/ou de solides grossiers. Certaines méthodes de réduction de la hauteur de charge sont disponibles pour les fluides newtoniens à viscosité élevée, les fluides plastiques de Bingham et les solides grossiers que l'on retrouve dans l'eau. Cet article présente une modification de la méthode de réduction de la hauteur de charge de l'Hydraulic Institute qui convient à n'importe quelle rhéologie non newtonienne homogène. Une modification de la méthode de Walker et Goulas est également envisagée. L'article traite également du comportement anomal possible des bouillies de kaolin dans les pompes centrifuges. [source]


    LDA Velocity Measurements of High-Viscosity Fluids in Mixing Vessel with Vane Geometry Impeller

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2007
    Lidija Slemenik Perse
    Abstract The object of this work was to measure the velocity field in non-Newtonian fluids inside mixing vessel. The six-bladed vane rotor used for mixing was designed from rotating vane geometry of a sensor system, commonly used for rheometrical measurements of complex fluids (Barnes and Nguyen, J. Non-Newtonian Fluid Mech. 98, 1-14 (2001); Schramm, 1994). During mixing, the viscosity was determined by measuring the torque at different impeller speeds, and compared to rheologically obtained shear dependent viscosity. The velocity field was determined by LDA measurements at twelve places inside mixing vessel. It was observed that axial and radial component of the velocity were insignificant at all measurement points. On the other hand, the results showed the periodic nature of tangential component of the velocity, which was confirmed with computer-aided visualization method. Ce travail avait pour objectif de mesurer le champ de vitesse dans des fluides non newtoniens dans un réservoir de mélange. Le rotor à six pales utilisé pour le mélange a été conçu d'après la géométrie des ailettes rotatives d'un système de senseurs, communément utilisés dans les mesures rhéométriques de fluides complexes (Barnes and Nguyen, J. Non-Newtonian Fluid Mech. 98, 1-14 (2001); Schramm, 1994). Lors du mélange, on a déterminé la viscosité en mesurant le couple à différentes vitesses de turbine, puis on l'a comparée à la viscosité de cisaillement obtenue rhéologiquement. Le champ de vitesse a été déterminé par des mesures LDA à douze positions dans le réservoir de mélange. On a observé que la composante axiale et radiale de la vitesse était négligeable pour tous les points de mesure. Par ailleurs, les résultats montrent la nature périodique de la composante tangentielle de la vitesse, ce qui est confirmé par une méthode de visualisation assistée par ordinateur. [source]


    Gas,liquid mass transfer in three-phase inverse fluidized bed reactor with Newtonian and non-Newtonian fluids

    ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010
    V. Sivasubramanian
    Abstract Liquid-phase volumetric mass transfer coefficients, kLa were determined in three-phase inverse fluidized beds of low-density polyethylene (LDPE) and polypropylene (PP) spheres fluidized by a countercurrent flow of air and Newtonian (water and glycerol solutions) or non-Newtonian liquids [carboxy methyl cellulose (CMC) solutions]. The effects of liquid and gas velocities, particle size, solid loading and addition of organic additives (glycerol and CMC) on the volumetric mass transfer coefficient, kLa were determined. The superficial liquid velocity had a weak effect on the mass transfer whereas the gas flow rate affected the mass transfer positively. kLa increased with increase in particle diameter and decreased with increase in initial bed height (solid loading). kLa decreased as the concentration of glycerol (viscosity) and CMC increased. Empirical correlations are presented to predict the gas,liquid volumetric mass transfer coefficient in terms of operating variables. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]


    Explicit Calculation of the Friction Factor for Non-Newtonian Fluids Using Artificial Neural Networks

    ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2005
    W. H. Shayya
    An explicit procedure based on artificial neural networks (ANN) was developed for calculating the friction factor (f) for Herschel-Bulkley fluids under laminar and turbulent flow conditions in closed pipes. The Regula-Falsi method was used as an iterative procedure to estimate the f values for a range of flow behavior indexes (n), Reynolds numbers (Re), and Hedstrom numbers (He). In developing the ANN model, the input parameters Re and He and the output parameter f were transformed using a logarithmic scale to the base 10, while the input parameter n was taken on a linear scale. An ANN configuration with 16 neurons in each of two hidden layers was found to be optimal. However, a simpler ANN model with eight neurons in one hidden layer also produced reasonably good predictions. These values were in close agreement with those obtained using the numerical technique. The developed ANN model may offer significant advantages when dealing with flow problems that involve repetitive calculations of the friction factor such as those encountered in the hydraulic analysis of viscous non-Newtonian fluids in pipe networks. [source]


    CFD simulation of non-Newtonian fluid flow in anaerobic digesters

    BIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008
    Binxin Wu
    Abstract 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-, 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. Biotechnol. Bioeng. 2008;99: 700,711. © 2007 Wiley Periodicals, Inc. [source]


    Bubbles, drops and particles in non-newtonian fluids.

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2007

    No abstract is available for this article. [source]