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J M Miranda - One of the best experts on this subject based on the ideXlab platform.

  • rising of a single taylor drop in a Stagnant Liquid 2d laminar flow and axisymmetry limits
    Physics of Fluids, 2016
    Co-Authors: F J N Direito, J B L M Campos, J M Miranda
    Abstract:

    A numerical (computational fluid dynamics (CFD)) study concerning the rise of individual Liquid Taylor drops through vertical columns of Stagnant heavier Liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier Liquid was within the range 0.01–40 and Eotvos number was between 8 and 30. Morton number was within the interval of 2.32 × 10−6–100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase Liquid film). The influence of changing one dimen...

  • rising of a single taylor drop in a Stagnant Liquid 2d laminar flow and axisymmetry limits
    Physics of Fluids, 2016
    Co-Authors: F J N Direito, J B L M Campos, J M Miranda
    Abstract:

    A numerical (computational fluid dynamics(CFD)) study concerning the rise of individual Liquid Taylor drops through vertical columns of Stagnant heavier Liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier Liquid was within the range 0.01–40 and Eotvos number was between 8 and 30. Morton number was within the interval of 2.32 × 10−6–100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase Liquid film). The influence of changing one dimensionless parameter alone was assessed. For small and large viscosity ratios, axisymmetric behavior is not a valid assumption.

  • Rising of a single Taylor drop in a Stagnant Liquid—2D laminar flow and axisymmetry limits
    Physics of Fluids, 2016
    Co-Authors: F J N Direito, J B L M Campos, J M Miranda
    Abstract:

    A numerical (computational fluid dynamics(CFD)) study concerning the rise of individual Liquid Taylor drops through vertical columns of Stagnant heavier Liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier Liquid was within the range 0.01–40 and Eotvos number was between 8 and 30. Morton number was within the interval of 2.32 × 10−6–100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase Liquid film). The influence of changing one dimensionless parameter alone was assessed. For small and large viscosity ratios, axisymmetric behavior is not a valid assumption.

Akio Tomiyama - One of the best experts on this subject based on the ideXlab platform.

  • Numerical simulation of slugging of Stagnant Liquid at a V-shaped elbow in a pipeline☆
    Applied Mathematical Modelling, 2014
    Co-Authors: Motoki Irikura, Munenori Maekawa, Shigeo Hosokawa, Akio Tomiyama
    Abstract:

    Abstract Numerical simulation of slugging of a Stagnant Liquid at a V-shaped elbow in a hilly-terrain pipeline is carried out using a three-dimensional two-fluid model. The free surface treatment for the interfacial area density is employed to describe the interaction between the phases. Comparisons with experimental data show that this numerical model is able to simulate slug development from static puddle. The onset of slugging is also predictable with reasonable accuracy. The mechanism of the onset of slugging is discussed based on the numerical predictions. The predictions make it clear that the pressure drop of gas flow at the V-shaped elbow induces the difference in the Liquid level between upstream and downstream regions of the V-shaped elbow, which is the major trigger of the onset of slugging of Stagnant Liquid at the V-shaped elbow.

  • application of chahn hilliard equation to the evaluation of surface tension force
    Japanese Journal of Multiphase Flow, 2006
    Co-Authors: Kosuke Hayashi, Naoki Takada, Akio Tomiyama
    Abstract:

    An accurate method for evaluating surface tension force was proposed. The method utilizes a solution of the Cahn-Hilliard equation for the color function of the Continuum Surface Force model. Curvature vectors on three surfaces of revolution, i.e., sphere, distorted spheroid and spherical-cap were accurately evaluated by the method. Interface tracking simulations of a flow around a neutrally buoyant fluid sphere and of a drop rising through a Stagnant Liquid demonstrated that the proposed method could significantly reduce pseudo parasitic currents caused by numerical errors in surface tension force.

  • Drag Coefficients of Single Bubbles under Normal and Micro Gravity Conditions
    Jsme International Journal Series B-fluids and Thermal Engineering, 1998
    Co-Authors: Akio Tomiyama, Iztok Zun, Isao Kataoka, Tadashi Sakaguchi
    Abstract:

    Simple but reliable correlations for a drag coefficient, CD, of single bubbles under a wide range of fluid properties, bubble diameter and acceleration of gravity were developed based on a balance of forces acting on a bubble in a Stagnant Liquid and available empirical correlations of terminal rising velocities of single bubbles. The proposed CD consists of three equations, each of which corresponds to pure, slightly contaminated and contaminated systems. The effect of a frictional pressure gradient due to a Liquid flow is also taken into account by introducing a concept of an effective body acceleration. Terminal rising velocities of single bubbles were calculated using the proposed CD, and compared with measured data under the condition of 10-2

  • Numerical Simulation of a Taylor Bubble in a Stagnant Liquid inside a Vertical Pipe
    JSME International Journal Series B, 1996
    Co-Authors: Akio Tomiyama, Akira Sou, Tadashi Sakaguchi
    Abstract:

    The feasibility of a detailed numerical simulation of a Taylor bubble in a Stagnant Liquid filling a vertical pipe was examined in the present study. The simulation was carried out using the volume of fluid method. Since there have been few quantitative experiments on Taylor bubble shape, physical experiments under a wide range of Eotvos and Morton numbers were also conducted using sucrose solution and air at room temperature and atmospheric pressure. It was confirmed by experiments that the bluntness of the nose of the bubble, the flatness of the tail and the Liquid film thickness around the bubble are strongly affected by the two dimensionless numbers. Calculated terminal rising velocities and bubble shapes agreed fairly well with all the measured ones, which indicates that the effects of drag force, buoyancy and surface tension force on the bubble were well predicted by the simulation.

  • numerical simulation of a taylor bubble in a Stagnant Liquid inside a vertical pipe
    Transactions of the Japan Society of Mechanical Engineers. B, 1994
    Co-Authors: Akio Tomiyama, Akira Sou, Tadashi Sakaguchi
    Abstract:

    The feasibility of a detailed numerical simulation of a Taylor bubble in a Stagnant Liquid filling in a vertical pipe was examined in the present study. The simulation was carried out using the volume of fluid method. Since there have been few quantitative experiments on Taylor bubble shape, physical experiments under a wide range of the Eotvos number (Eo) and Morton number (M) were also conducted using sucrose solution and air at room temperature and atmospheric pressure. It was confirmed by the experiments that the bluntness of the nose of the bubble, the flatness of the tail, and the Liquid film thickness around the bubble are strongly affected by the two dimensionless numbers, Eo and M. Calculated terminal rising velocities and bubble shapes agreed fairly well with the measured ones, which indicates that the effects of drag force, buoyancy and surface tension force on the bubble were well predicted in the simulation.

Anand Sundarajan - One of the best experts on this subject based on the ideXlab platform.

  • Model analysis of biological oxygen transfer enhancement in surface‐aerated bioreactors
    Biotechnology and bioengineering, 1992
    Co-Authors: Anand Sundarajan
    Abstract:

    A model was developed to evaluate the effects of cells and surfactants on oxygen transfer in surface-aerated bioreactors. The model assumed the presence of serial layers of adsorbed surfactants and microorganisms directly adjacent to the gas-Liquid interface due to their surface activities, followed by a Stagnant Liquid layer to account for the oxygen transfer resistance in the Liquid phase. The interfacial surfactant film, although posing as an additional resistance, was found to have negligible effect on the oxygen transfer rate because of its extremely small thickness as compared to the cell monolayer and the Stagnant Liquid layer. On the other hand, cells affect oxygen transfer by two mechanisms: the biological enhancement due to the respiration of interfacial cells and the physical blocking resulting from the semipermeable nature of cell bodies. Due to the low specific oxygen uptake rates of the sludges, the two mechanisms were found to be of comparable importance in activated-sludge systems; the oxygen transfer enhancement factor, E, varied from about 0.97 to 1.10 depending on the operating conditions. The biological enhancement effect, however, predominated in fermentations of actively growing bacteria. At relatively low agitation speed (e. g., 300 rpm), the value of E could reach about 3 to 5 in fermentations with high cell concentrations. Effects of other operating variables, such as the agitation intensity, the oxygen content in the mixed liquor, and the bulk cell concentration, on biological oxygen transfer enhancement were also studied.

  • Model analysis of biological oxygen transfer enhancement in surface‐aerated bioreactors
    Biotechnology and bioengineering, 1992
    Co-Authors: Anand Sundarajan
    Abstract:

    A model was developed to evaluate the effects of cells and surfactants on oxygen transfer in surface-aerated bioreactors. The model assumed the presence of serial layers of adsorbed surfactants and microorganisms directly adjacent to the gas–Liquid interface due to their surface activities, followed by a Stagnant Liquid layer to account for the oxygen transfer resistance in the Liquid phase. The interfacial surfactant film, although posing as an additional resistance, was found to have negligible effect on the oxygen transfer rate because of its extremely small thickness as compared to the cell monolayer and the Stagnant Liquid layer. On the other hand, cells affect oxygen transfer by two mechanisms: the biological enhancement due to the respiration of interfacial cells and the physical blocking resulting from the semipermeable nature of cell bodies. Due to the low specific oxygen uptake rates of the sludges, the two mechanisms were found to be of comparable importance in activated-sludge systems; the oxygen transfer enhancement factor, E, varied from about 0.97 to 1.10 depending on the operating conditions. The biological enhancement effect, however, predominated in fermentations of actively growing bacteria. At relatively low agitation speed (e. g., 300 rpm), the value of E could reach about 3 to 5 in fermentations with high cell concentrations. Effects of other operating variables, such as the agitation intensity, the oxygen content in the mixed liquor, and the bulk cell concentration, on biological oxygen transfer enhancement were also studied. © 1992 John Wiley & Sons, Inc.

F J N Direito - One of the best experts on this subject based on the ideXlab platform.

  • rising of a single taylor drop in a Stagnant Liquid 2d laminar flow and axisymmetry limits
    Physics of Fluids, 2016
    Co-Authors: F J N Direito, J B L M Campos, J M Miranda
    Abstract:

    A numerical (computational fluid dynamics (CFD)) study concerning the rise of individual Liquid Taylor drops through vertical columns of Stagnant heavier Liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier Liquid was within the range 0.01–40 and Eotvos number was between 8 and 30. Morton number was within the interval of 2.32 × 10−6–100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase Liquid film). The influence of changing one dimen...

  • rising of a single taylor drop in a Stagnant Liquid 2d laminar flow and axisymmetry limits
    Physics of Fluids, 2016
    Co-Authors: F J N Direito, J B L M Campos, J M Miranda
    Abstract:

    A numerical (computational fluid dynamics(CFD)) study concerning the rise of individual Liquid Taylor drops through vertical columns of Stagnant heavier Liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier Liquid was within the range 0.01–40 and Eotvos number was between 8 and 30. Morton number was within the interval of 2.32 × 10−6–100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase Liquid film). The influence of changing one dimensionless parameter alone was assessed. For small and large viscosity ratios, axisymmetric behavior is not a valid assumption.

  • Rising of a single Taylor drop in a Stagnant Liquid—2D laminar flow and axisymmetry limits
    Physics of Fluids, 2016
    Co-Authors: F J N Direito, J B L M Campos, J M Miranda
    Abstract:

    A numerical (computational fluid dynamics(CFD)) study concerning the rise of individual Liquid Taylor drops through vertical columns of Stagnant heavier Liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier Liquid was within the range 0.01–40 and Eotvos number was between 8 and 30. Morton number was within the interval of 2.32 × 10−6–100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase Liquid film). The influence of changing one dimensionless parameter alone was assessed. For small and large viscosity ratios, axisymmetric behavior is not a valid assumption.

J B L M Campos - One of the best experts on this subject based on the ideXlab platform.

  • rising of a single taylor drop in a Stagnant Liquid 2d laminar flow and axisymmetry limits
    Physics of Fluids, 2016
    Co-Authors: F J N Direito, J B L M Campos, J M Miranda
    Abstract:

    A numerical (computational fluid dynamics (CFD)) study concerning the rise of individual Liquid Taylor drops through vertical columns of Stagnant heavier Liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier Liquid was within the range 0.01–40 and Eotvos number was between 8 and 30. Morton number was within the interval of 2.32 × 10−6–100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase Liquid film). The influence of changing one dimen...

  • rising of a single taylor drop in a Stagnant Liquid 2d laminar flow and axisymmetry limits
    Physics of Fluids, 2016
    Co-Authors: F J N Direito, J B L M Campos, J M Miranda
    Abstract:

    A numerical (computational fluid dynamics(CFD)) study concerning the rise of individual Liquid Taylor drops through vertical columns of Stagnant heavier Liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier Liquid was within the range 0.01–40 and Eotvos number was between 8 and 30. Morton number was within the interval of 2.32 × 10−6–100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase Liquid film). The influence of changing one dimensionless parameter alone was assessed. For small and large viscosity ratios, axisymmetric behavior is not a valid assumption.

  • Rising of a single Taylor drop in a Stagnant Liquid—2D laminar flow and axisymmetry limits
    Physics of Fluids, 2016
    Co-Authors: F J N Direito, J B L M Campos, J M Miranda
    Abstract:

    A numerical (computational fluid dynamics(CFD)) study concerning the rise of individual Liquid Taylor drops through vertical columns of Stagnant heavier Liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier Liquid was within the range 0.01–40 and Eotvos number was between 8 and 30. Morton number was within the interval of 2.32 × 10−6–100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase Liquid film). The influence of changing one dimensionless parameter alone was assessed. For small and large viscosity ratios, axisymmetric behavior is not a valid assumption.