Dynamics of axisymmetric core-annular flow in a straight tube. I. The more viscous fluid in the core, bamboo waves

2001 ◽  
Vol 13 (4) ◽  
pp. 841-858 ◽  
Author(s):  
Charalampos Kouris ◽  
John Tsamopoulos
Keyword(s):  
Viscous Fluid ◽  
Annular Flow ◽  
Straight Tube ◽  
The Core

Convective/absolute instability in miscible core-annular flow. Part 2. Numerical simulations and nonlinear global modes

2009 ◽  
Vol 618 ◽  
pp. 323-348 ◽  
Author(s):  
B. SELVAM ◽  
L. TALON ◽  
L. LESSHAFFT ◽  
E. MEIBURG
Keyword(s):  
Viscous Fluid ◽  
Numerical Simulations ◽  
Annular Flow ◽  
Nonlinear Oscillations ◽  
Variable Viscosity ◽  
Base Flow ◽  
Absolute Instability ◽  
Infinite Domain ◽  
Global Mode ◽  
The Core

The convective/absolute nature of the instability of miscible core-annular flow with variable viscosity is investigated via linear stability analysis and nonlinear simulations. From linear analysis, it is found that miscible core-annular flows with the more viscous fluid in the core are at most convectively unstable. On the other hand, flows with the less viscous fluid in the core exhibit absolute instability at high viscosity ratios, over a limited range of core radii. Nonlinear direct numerical simulations in a semi-infinite domain display self-excited intrinsic oscillations if and only if the underlying base flow exhibits absolute instability. This oscillator-type flow behaviour is demonstrated to be associated with the presence of a nonlinear global mode. Both the parameter range of global instability and the intrinsically selected frequency of nonlinear oscillations, as observed in the simulation, are accurately predicted from linear criteria. In convectively unstable situations, the flow is shown to respond to external forcing over an unstable range of frequencies, in quantitative agreement with linear theory. As discussed in part 1 of this study (d'Olce, Martin, Rakotomalala, Salin and Talon,J. Fluid Mech., vol. 618, 2008, pp. 305–322), self-excited synchronized oscillations were also observed experimentally. An interpretation of these experiments is attempted on the basis of the numerical results presented here.

Dynamics of the axisymmetric core-annular flow. II. The less viscous fluid in the core, saw tooth waves

2002 ◽  
Vol 14 (3) ◽  
pp. 1011-1029 ◽  
Author(s):  
Charalampos Kouris ◽  
John Tsamopoulos
Keyword(s):  
Viscous Fluid ◽  
Annular Flow ◽  
The Core

scholarly journals Studies on the Fluidized Bed Electrode

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Siva Kumar ◽  
Thilakavathi Ramamurthy ◽  
Bala Subramanian ◽  
Ahmed Basha
Keyword(s):  
Fluidized Bed ◽  
Annular Flow ◽  
Flow Model ◽  
Model Simulation ◽  
Flow Behavior ◽  
Hydrodynamic Characteristics ◽  
The Core ◽  
Particle Transfer ◽  
Fluidized Bed Electrode

The present investigation attempts to study the hydrodynamic characteristics of the fluidized bed electrode. A core-annular flow model with a transfer of particles between core-annular layers has been proposed to describe the flow behavior of conducting particles in the fluidized bed electrode. The effect of individual parameters on the rate of the particle transfer across the layer and thickness of the core-annular has been critically examined and the model simulation has been verified with the data reported in the literature.

scholarly journals Gravitational differentiation in the regimes from stokes settling to Rayleigh–Raylor flows

2019 ◽  
pp. 15-30
Author(s):  
V. P. Trubitsyn
Keyword(s):  
Viscous Fluid ◽  
Interacting Particles ◽  
Small Particles ◽  
Continuous Transition ◽  
New Approach ◽  
Earth's Core ◽  
The Core ◽  
The Earth ◽  
Large Particles ◽  
Two Component

The Earth’s core was formed under gravitational differentiation in the course of the separation of iron and silicates. Most of the iron has gone into the core as early as when the Earth was growing. However, iron continued to precipitate even during the subsequent partial solidification which developed from the bottom upwards. At the different stages and in the different layers of the mantle, iron was deposited in different regimes. In this paper, the mechanisms of the deposition of a cloud of heavy interacting particles (or drops) in a viscous fluid are considered. A new approach suitable for analytical and numerical tracing the changes in the structure of the flows in a two-component suspension under continuous transition from the Stokessettling (for the case of a cloud of large particles) to the Rayleigh–Taylor flows and heavy diapirs (for the case of a cloud of small particles) is suggested. It is numerically and analytically shown that the both regimes are the different limiting cases of the sedimentation convection in suspensions.

Water-assisted Flow of Heavy Oil in a Vertical Pipe: Pilot-scale Experiments

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Antonio C. Bannwart ◽  
Oscar M. H. Rodriguez ◽  
Jorge L. Biazussi ◽  
Fabio N. Martins ◽  
Marcelo F. Selli ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Annular Flow ◽  
Water Injection ◽  
Pilot Scale ◽  
Heavy Oils ◽  
Monitoring And Control ◽  
Two Phase ◽  
The Core ◽  
Artificial Lift ◽  
The Individual

The use of the core-annular flow pattern, where a thin fluid surrounds a very viscous one, has been suggested as an attractive artificial-lift method for heavy oils in the current Brazilian ultra-deepwater production scenario. This paper reports the pressure drop measurements and the core-annular flow observed in a 2 7/8-inch and 300 meter deep pilot-scale well conveying a mixture of heavy crude oil (2000 mPa.s and 950 kg/m3 at 35 C) and water at several combinations of the individual flow rates. The two-phase pressure drop data are compared with those of single-phase oil flow to assess the gains due to water injection. Another issue is the handling of the core-annular flow once it has been established. High-frequency pressure-gradient signals were collected and a treatment based on the Gabor transform together with neural networks is proposed as a promising solution for monitoring and control. The preliminary results are encouraging. The pilot-scale tests, including long-term experiments, were conducted in order to investigate the applicability of using water to transport heavy oils in actual wells. It represents an important step towards the full scale application of the proposed artificial-lift technology. The registered improvements in terms of oil production rate and pressure drop reductions are remarkable.

Comparison of spectral and finite element methods applied to the study of the core-annular flow in an undulating tube

2002 ◽  
Vol 39 (1) ◽  
pp. 41-73 ◽  
Author(s):  
Charalampos Kouris ◽  
Yannis Dimakopoulos ◽  
Georgios Georgiou ◽  
John Tsamopoulos
Keyword(s):  
Finite Element ◽  
Finite Element Methods ◽  
Annular Flow ◽  
The Core

Direct numerical simulation of a turbulent core-annular flow with water-lubricated high viscosity oil in a vertical pipe

2018 ◽  
Vol 849 ◽  
pp. 419-447 ◽  
Author(s):  
Kiyoung Kim ◽  
Haecheon Choi
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Pipe Flow ◽  
Annular Flow ◽  
Volume Fraction ◽  
Phase Interface ◽  
High Viscosity ◽  
Vertical Pipe ◽  
The Core ◽  
High Viscosity Oil

The characteristics of a turbulent core-annular flow with water-lubricated high viscosity oil in a vertical pipe are investigated using direct numerical simulation, in conjunction with a level-set method to track the phase interface between oil and water. At a given mean wall friction ($Re_{\unicode[STIX]{x1D70F}}=u_{\unicode[STIX]{x1D70F}}R/\unicode[STIX]{x1D708}_{w}=720$, where $u_{\unicode[STIX]{x1D70F}}$ is the friction velocity, $R$ is the pipe radius and $\unicode[STIX]{x1D708}_{w}$ is the kinematic viscosity of water), the total volume flow rate of a core-annular flow is similar to that of a turbulent single-phase pipe flow of water, indicating that water lubrication is an effective tool to transport high viscosity oil in a pipe. The high viscosity oil flow in the core region is almost a plug flow due to its high viscosity, and the water flow in the annular region is turbulent except for the case of large oil volume fraction (e.g. 0.91 in the present study). With decreasing oil volume fraction, the mean velocity profile in the annulus becomes more like that of turbulent pipe flow, but the streamwise evolution of vortical structures is obstructed by the phase interface wave. In a reference frame moving with the core velocity, water is observed to be trapped inside the wave valley in the annulus, and only a small amount of water runs through the wave crest. The phase interface of the core-annular flow consists of different streamwise and azimuthal wavenumber components for different oil holdups. The azimuthal wavenumber spectra of the phase interface amplitude have largest power at the smallest wavenumber whose corresponding wavelength is the pipe circumference, while the streamwise wavenumber having the largest power decreases with decreasing oil volume fraction. The overall convection velocity of the phase interface is slightly lower than the core velocity. Finally, we suggest a predictive oil holdup model by defining the displacement thickness in the annulus and considering the boundary layer characteristics of water flow. This model predicts the variation of the oil holdup with the superficial velocity ratio very well.

Core–annular flow in a periodically constricted circular tube. Part 1. Steady-state, linear stability and energy analysis

2001 ◽  
Vol 432 ◽  
pp. 31-68 ◽  
Author(s):  
CHARALAMPOS KOURIS ◽  
JOHN TSAMOPOULOS
Keyword(s):  
Weber Number ◽  
Annular Flow ◽  
Viscosity Ratio ◽  
Solid Wall ◽  
Immiscible Fluids ◽  
Straight Tube ◽  
Neutral Stability ◽  
Ohnesorge Number ◽  
Dimensionless Numbers ◽  
Two Phase

The concentric, two-phase flow of two immiscible fluids in a tube of sinusoidally varying cross-section is studied. This geometry is often used as a model to study the onset of different flow regimes in packed beds. Neglecting gravitational effects, the model equations depend on five dimensionless parameters: the Reynolds and Weber numbers, and the ratios of density, viscosity and volume of the two fluids. Two more dimensionless numbers describe the shape of the solid wall: the constriction ratio and the ratio of its maximum radius to its period. In addition to the effect of the Weber number, which depends on both the fluid and the flow, the effect of the Ohnesorge number J has been examined as it characterizes the fluid alone. The governing equations are approximated using the pseudo-spectral methodology while the Arnoldi algorithm has been implemented for computing the most critical eigenvalues that correspond to axisymmetric disturbances. Stationary solutions are obtained for a wide parameter range, which may exhibit flow recirculation at the expanding portion of the tube. Extensive calculations are made for the dependence of the neutral stability boundaries on the various parameters. In most cases where the steady solution becomes unstable it does so through a Hopf bifurcation. Exceptions to this are cases where the viscosity ratio is O(10−3) and, then, the most unstable eigenvalue remains real. Generally, steady core–annular flow in this geometry is more susceptible to instability than in a straight tube and, in similar ranges of the parameters, it may be generated by different mechanisms. Decreasing the thickness of the annular fluid, inverse Weber number or the Ohnesorge number or the density of the core fluid stabilizes the flow. For stability reasons, the viscosity ratio must remain strictly below unity and it has an optimum value that maximizes the range of allowed Reynolds numbers.

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