scholarly journals Numerical Study of Shear Banding in Flows of Fluids Governed by the Rolie-Poly Two-Fluid Model via Stabilized Finite Volume Methods

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 810
Author(s):  
Jade Gesare Abuga ◽  
Tiri Chinyoka
Keyword(s):  
Finite Volume ◽  
Numerical Algorithm ◽  
Numerical Study ◽  
Fluid Model ◽  
Shear Banding ◽  
Numerical Algorithms ◽  
Viscoelastic Fluids ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Good Agreement

The flow of viscoelastic fluids may, under certain conditions, exhibit shear-banding characteristics that result from their susceptibility to unusual flow instabilities. In this work, we explore both the existing shear banding mechanisms in the literature, namely; constitutive instabilities and flow-induced inhomogeneities. Shear banding due to constitutive instabilities is modelled via either the Johnson–Segalman or the Giesekus constitutive models. Shear banding due to flow-induced inhomogeneities is modelled via the Rolie–Poly constitutive model. The Rolie–Poly constitutive equation is especially chosen because it expresses, precisely, the shear rheometry of polymer solutions for a large number of strain rates. For the Rolie–Poly approach, we use the two-fluid model wherein the stress dynamics are coupled with concentration equations. We follow a computational analysis approach via an efficient and versatile numerical algorithm. The numerical algorithm is based on the Finite Volume Method (FVM) and it is implemented in the open-source software package, OpenFOAM. The efficiency of our numerical algorithms is enhanced via two possible stabilization techniques, namely; the Log-Conformation Reformulation (LCR) and the Discrete Elastic Viscous Stress Splitting (DEVSS) methodologies. We demonstrate that our stabilized numerical algorithms accurately simulate these complex (shear banded) flows of complex (viscoelastic) fluids. Verification of the shear-banding results via both the Giesekus and Johnson-Segalman models show good agreement with existing literature using the DEVSS technique. A comparison of the Rolie–Poly two-fluid model results with existing literature for the concentration and velocity profiles is also in good agreement.

A NUMERICAL STUDY OF TWO-PHASE FLOW USING A TWO-DIMENSIONAL TWO-FLUID MODEL

2004 ◽  
Vol 45 (10) ◽  
pp. 1049-1066 ◽  
Author(s):  
Moon-Sun Chung ◽  
Seung-Kyung Pak ◽  
Keun-Shik Chang
Keyword(s):  
Two Phase Flow ◽  
Numerical Study ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Dimensional ◽  
Two Phase ◽  
Two Fluid Model ◽  
Two Fluid

The thermal conductivity of tin at low temperatures

1955 ◽  
Vol 229 (1179) ◽  
pp. 473-492 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Low Temperatures ◽  
Fluid Model ◽  
Accurate Method ◽  
Resistance Thermometers ◽  
Lattice Waves ◽  
Normal States ◽  
Two Fluid Model ◽  
Two Fluid ◽  
Good Agreement

An account is given of an accurate method of measuring the thermal conductivity of metals between 0·2 and 4°K using carbon aquadag resistance thermometers. Experimental curves are shown for tin specimens of different crystal structure and of varying impurity contents in both superconducting and normal states, and they are analyzed on the basis of the two-fluid model of superconductivity. It appears that at low temperatures the conductivity is mainly due to the lattice, since the observed temperature variation for all specimens is consistent with a T 3 law at sufficiently low temperatures. Good agreement is obtained between the effective mean free paths of the lattice waves and the values expected from the rod dimensions and crystal sizes. The electronic contribution to the thermal conduction in the superconducting state falls very rapidly below T c , and, to a first approximation, the ratio of this contribution to that in the normal state is a function of temperature and not of impurity. The effects of magnetic fields on measurements of thermal conductivity are also briefly discussed and it is shown that the results may be complicated by frozen-in flux.

scholarly journals Effect of liquid phase compressibility on modeling of gas-liquid two-phase flows using two-fluid model

2019 ◽  
Vol 23 (5 Part B) ◽  
pp. 3003-3013
Author(s):  
Vahid Shokri ◽  
Kazem Esmaeili
Keyword(s):  
Liquid Phase ◽  
Relative Velocity ◽  
Numerical Study ◽  
Fluid Model ◽  
Shock Capturing ◽  
Two Phase ◽  
Solution Field ◽  
Two Fluid Model ◽  
Flow Variables ◽  
Two Fluid

In this paper, a numerical study is performed in order to investigate the effect of the liquid phase compressibility two-fluid model. The two-fluid model is solved by using conservative shock capturing method. At the first, the two-fluid model is applied by assuming that the liquid phase is incompressible, then it is assumed that in three cases called water faucet case, large relative velocity shock pipe case, and Toumi?s shock pipe case, the liquid phase is compressible. Numerical results indicate that, if an intense pressure gradient is governed on the fluid-flow, single-pressure two-fluid model by assuming liquid phase incompressibility predicts the flow variables in the solution field more accurate than single-pressure two-fluid model by assuming liquid phase compressibility.

scholarly journals Shear Banding in 4:1 Planar Contraction

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 417 ◽  
Author(s):  
Soroush Hooshyar ◽  
Natalie Germann
Keyword(s):  
Fluid Model ◽  
Shear Banding ◽  
Polymer Concentration ◽  
Shear Bands ◽  
Mass Conservation ◽  
Industrial Applications ◽  
Flow Recirculation ◽  
Two Fluid Model ◽  
Planar Contraction ◽  
Two Fluid

We study shear banding in a planar 4:1 contraction flow using our recently developed two-fluid model for semidilute entangled polymer solutions derived from the generalized bracket approach of nonequilibrium thermodynamics. In our model, the differential velocity between the constituents of the solution allows for coupling between the viscoelastic stress and the polymer concentration. Stress-induced migration is assumed to be the triggering mechanism of shear banding. To solve the benchmark problem, we used the OpenFOAM software package with the viscoelastic solver RheoTool v.2.0. The convection terms are discretized using the high-resolution scheme CUBISTA, and the governing equations are solved using the SIMPLEC algorithm. To enter into the shear banding regime, the uniform velocity at the inlet was gradually increased. The velocity increases after the contraction due to the mass conservation; therefore, shear banding is first observed at the downstream. While the velocity profile in the upstream channel is still parabolic, the corresponding profile changes to plug-like after the contraction. In agreement with experimental data, we found that shear banding competes with flow recirculation. Finally, the profile of the polymer concentration shows a peak in the shear banding regime, which is closer to the center of the channel for larger inlet velocities. Nevertheless, the increase in the polymer concentration in the region of flow recirculation was significantly larger for the inlet velocities studied in this work. With our two-fluid finite-volume solver, localized shear bands in industrial applications can be simulated.

NUMERICAL STUDY OF MAGNETIC PENETRATION DEPTH IN MgB2

2013 ◽  
Vol 27 (15) ◽  
pp. 1362027
Author(s):  
BO LI ◽  
DE-HUA LIN
Keyword(s):  
Penetration Depth ◽  
Energy Gap ◽  
Numerical Study ◽  
Fluid Model ◽  
Magnetic Penetration Depth ◽  
Fitting Method ◽  
Numerical Fitting ◽  
Two Fluid Model ◽  
Magnetic Penetration ◽  
Two Fluid

The magnetic penetration depth formula in MgB 2 is more complex than that in BCS superconductors due to the existence of exotic two energy gap in MgB 2. A new simplified relationship between the penetration depth and temperature is presented, which is derived from the two-fluid model by means of numerical fitting method, and the physical meaning is relatively clear.

Numerical study on the bubbly flow around a hydrofoil in pitching and heaving motions

2003 ◽  
Vol 217 (7) ◽  
pp. 811-820 ◽  
Author(s):  
T Uchiyama
Keyword(s):  
Horizontal Plane ◽  
Numerical Study ◽  
Fluid Model ◽  
Bubbly Flow ◽  
The Finite Element Method ◽  
Flow Properties ◽  
Volumetric Fraction ◽  
Propulsive Performance ◽  
Two Fluid Model ◽  
Two Fluid

The air-water bubbly flow around a hydrofoil of NACA65-010, undergoing the heaving and pitching motions in the uniform flow on a horizontal plane, is simulated by an incompressible two-fluid model. The finite element method proposed in a prior paper is applied to solve the model. The Reynolds number defined by the volumetric velocity of the water is 10000 and the volumetric fraction of the air upstream of the hydrofoil, αg0, ranges from 0 to 0.06. The simulation reveals the effects of the αg0 value, the phase difference between the heaving and pitching motions, and the oscillating frequency. The propulsive performance is also discussed in relation to the time variation of the flow properties around the hydrofoil.

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