Oscillatory regimes of capillary imbibition of viscoelastic fluids through concentric annulus

RSC Advances ◽  
2016 ◽  
Vol 6 (65) ◽  
pp. 60117-60125 ◽  
Author(s):  
Jayabrata Dhar ◽  
Parth Jaggi ◽  
Suman Chakraborty
Keyword(s):  
Viscoelastic Fluid ◽  
Viscoelastic Fluids ◽  
Capillary Imbibition ◽  
Cylindrical Capillary ◽  
Dynamical Characteristics ◽  
Concentric Annulus ◽  
Capillary Filling

Here we report the capillary filling dynamics of a viscoelastic fluid through a concentric annulus, which offers a distinct disparity in the dynamical characteristics as compared to the classical cylindrical capillary based paradigm.

Extended Self-Similarity in Drag-Reduced Turbulent Flow of Viscoelastic Fluid

2010 ◽  
Author(s):  
Feng-Chen Li ◽  
Hong-Na Zhang ◽  
Wei-Hua Cai ◽  
Juan-Cheng Yang
Keyword(s):  
Channel Flow ◽  
Viscoelastic Fluid ◽  
Isotropic Turbulence ◽  
Scaling Law ◽  
Viscoelastic Fluids ◽  
Turbulent Channel Flow ◽  
Elastic Model ◽  
Homogeneous Isotropic Turbulence ◽  
Self Similarity ◽  
Extended Self

Direct numerical simulations (DNS) have been performed for drag-reduced turbulent channel flow with surfactant additives and forced homogeneous isotropic turbulence with polymer additives. Giesekus constitutive equation and finite extensible nonlinear elastic model with Peterlin closure were used to describe the elastic stress tensor for both cases, respectively. For comparison, DNS of water flows for both cases were also performed. Based on the DNS data, the extended self-similarity (ESS) of turbulence scaling law is investigated for water and viscoelastic fluids in turbulent channel flow and forced homogeneous isotropic turbulence. It is obtained that ESS still holds for drag-reduced turbulent flows of viscoelastic fluids. In viscoelastic fluid flows, the regions at which δu(r)∝r and Sp(r)∝S3(r)ζ(p) with ζ(p) = p/3, where r is the scale length, δu(r) is the longitudinal velocity difference along r and Sp(r) is the pth-order moment of velocity increments, in the K41 (Kolmogorov theory)-fashioned plots and ESS-fashioned plots, respectively, are all broadened to larger scale for all the investigated cases.

Potential flows of viscous and viscoelastic fluids

1994 ◽  
Vol 265 ◽  
pp. 1-23 ◽  
Author(s):  
D. D. Joseph ◽  
T. Y. Liao
Keyword(s):  
Kinetic Energy ◽  
Steady Flow ◽  
Viscoelastic Fluid ◽  
Potential Flow ◽  
Viscoelastic Fluids ◽  
Second Order ◽  
Potential Flows ◽  
Linear Viscoelastic ◽  
Interior Flow ◽  
T Tau

Potential flows of incompressible fluids admit a pressure (Bernoulli) equation when the divergence of the stress is a gradient as in inviscid fluids, viscous fluids, linear viscoelastic fluids and second-order fluids. We show that in potential flow without boundary layers the equation balancing drag and acceleration is the same for all these fluids, independent of the viscosity or any viscoelastic parameter, and that the drag is zero when the flow is steady. But, if the potential flow is viewed as an approximation to the actual flow field, the unsteady drag on bubbles in a viscous (and possibly in a viscoelastic) fluid may be approximated by evaluating the dissipation integral of the approximating potential flow because the neglected dissipation in the vorticity layer at the traction-free boundary of the bubble gets smaller as the Reynolds number is increased. Using the potential flow approximation, the actual drag D on a spherical gas bubble of radius a rising with velocity U(t) in a linear viscoelastic liquid of density ρ and shear modules G(s) is estimated to be \[D = \frac{2}{3}\pi a^3 \rho {\dot U} + 12\pi a \int_{-\infty}^t G(t - \tau)U(\tau){\rm d}\tau\] and, in a second-order fluid, \[D = \pi a\left(\frac{2}{3}a^2 \rho + 12\alpha _1\right ) {\dot U} + 12\pi a\mu U,\] where α1, < 0 is the coefficient of the first normal stress and μ is the viscosity of the fluid. Because α1 is negative, we see from this formula that the unsteady normal stresses oppose inertia; that is, oppose the acceleration reaction. When U(t) is slowly varying, the two formulae coincide. For steady flow, we obtain the approximate drag D = 12πaμU for both viscous and viscoelastic fluids. In the case where the dynamic contribution of the interior flow of the bubble cannot be ignored as in the case of liquid bubbles, the dissipation method gives an estimation of the rate of total kinetic energy of the flows instead of the drag. When the dynamic effect of the interior flow is negligible but the density is important, this formula for the rate of total kinetic energy leads to D = (ρa – ρ) VBg · ex – ρaVB U where ρa is the density of the fluid (or air) inside the bubble and VB is the volume of the bubble.Classical theorems of vorticity for potential flow of ideal fluids hold equally for second-order fluid. The drag and lift on two-dimensional bodies of arbitrary cross-section in a potential flow of second-order and linear viscoelastic fluids are the same as in potential flow of an inviscid fluid but the moment M in a linear viscoelastic fluid is given by \[M = M_I + 2 \int_{-\infty}^t [G(t - \tau)\Gamma (\tau)]{\rm d}\tau,\] where MI is the inviscid moment and Γ(t) is the circulation, and \[M = M_I + 2 \mu \Gamma + 2\alpha _1 \partial \Gamma /\partial t\] in a second-order fluid. When Γ(t) is slowly varying, the two formulae for M coincide. For steady flow, they reduce to \[M = M_I + 2 \mu \Gamma ,\] which is also the expression for M in both steady and unsteady potential flow of a viscous fluid. Moreover, when there is no stream, this moment reduces to the actual moment M = 2μΓ on a rotating rod.Potential flows of models of a viscoelastic fluid like Maxwell's are studied. These models do not admit potential flows unless the curl of the divergence of the extra stress vanishes. This leads to an over-determined system of equations for the components of the stress. Special potential flow solutions like uniform flow and simple extension satisfy these extra conditions automatically but other special solutions like the potential vortex can satisfy the equations for some models and not for others.

Purely tangential flow of a PTT-viscoelastic fluid within a concentric annulus

2005 ◽  
Vol 129 (2) ◽  
pp. 88-97 ◽  
Author(s):  
M. Mirzazadeh ◽  
M.P. Escudier ◽  
F Rashidi ◽  
S.H. Hashemabadi
Keyword(s):  
Viscoelastic Fluid ◽  
Concentric Annulus ◽  
Tangential Flow

scholarly journals Effects of Ionic Strength on Lateral Particle Migration in Shear-Thinning Xanthan Gum Solutions

Micromachines ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 535 ◽  
Author(s):  
Mira Cho ◽  
Sun Ok Hong ◽  
Seung Hak Lee ◽  
Kyu Hyun ◽  
Ju Min Kim
Keyword(s):  
Ionic Strength ◽  
Rheological Properties ◽  
Viscoelastic Fluid ◽  
Xanthan Gum ◽  
Viscoelastic Fluids ◽  
Shear Thinning ◽  
Particle Migration ◽  
Cell Counting ◽  
Contour Length ◽  
Wide Range

Viscoelastic fluids, including particulate systems, are found in various biological and industrial systems including blood flow, food, cosmetics, and electronic materials. Particles suspended in viscoelastic fluids such as polymer solutions migrate laterally, forming spatially segregated streams in pressure-driven flow. Viscoelastic particle migration was recently applied to microfluidic technologies including particle counting and sorting and the micromechanical measurement of living cells. Understanding the effects on equilibrium particle positions of rheological properties of suspending viscoelastic fluid is essential for designing microfluidic applications. It has been considered that the shear-thinning behavior of viscoelastic fluid is a critical factor in determining the equilibrium particle positions. This work presents the lateral particle migration in two different xanthan gum-based viscoelastic fluids with similar shear-thinning viscosities and the linear viscoelastic properties. The flexibility and contour length of the xanthan gum molecules were tuned by varying the ionic strength of the solvent. Particles suspended in flexible and short xanthan gum solution, dissolved at high ionic strength, migrated toward the corners in a square channel, whereas particles in the rigid and long xanthan gum solutions in deionized water migrated toward the centerline. This work suggests that the structural properties of polymer molecules play significant roles in determining the equilibrium positions in shear-thinning fluids, despite similar bulk rheological properties. The current results are expected to be used in a wide range of applications such as cell counting and sorting.

scholarly journals Three-Dimensional Numerical Simulation of Particle Focusing and Separation in Viscoelastic Fluids

Micromachines ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 908
Author(s):  
Chen Ni ◽  
Di Jiang
Keyword(s):  
Viscoelastic Fluid ◽  
Rectangular Channel ◽  
Particle Interaction ◽  
Three Dimensional ◽  
Viscoelastic Fluids ◽  
Lateral Migration ◽  
Square Channel ◽  
Particle Focusing ◽  
Aspect Ratios ◽  
Large Particles

Particle focusing and separation using viscoelastic microfluidic technology have attracted lots of attention in many applications. In this paper, a three-dimensional lattice Boltzmann method (LBM) coupled with the immersed boundary method (IBM) is employed to study the focusing and separation of particles in viscoelastic fluid. In this method, the viscoelastic fluid is simulated by the LBM with two sets of distribution functions and the fluid–particle interaction is calculated by the IBM. The performance of particle focusing under different microchannel aspect ratios (AR) is explored and the focusing equilibrium positions of the particles with various elasticity numbers and particle diameters are compared to illustrate the mechanism of particle focusing and separation in viscoelastic fluids. The results indicate that, for particle focusing in the square channel (AR = 1), the centerline single focusing becomes a bistable focusing at the centerline and corners as El increases. In the rectangular channels (AR < 1), particles with different diameters have different equilibrium positions. The equilibrium position of large particles is closer to the wall, and large particles have a faster lateral migration speed and few large particles migrate towards the channel center. Compared with the square channel, the rectangular channel is a better design for particle separation.

Control of Mass Flow-Rate of Viscoelastic Fluids Through Time-Periodic Electro-Osmotic Flows in a Microchannel

2021 ◽  
Author(s):  
Sayantan Dawn ◽  
Sandip Sarkar
Keyword(s):  
Electric Field ◽  
Mass Flow Rate ◽  
Double Layer ◽  
Viscoelastic Fluid ◽  
Mass Flow ◽  
Flow Rate ◽  
Electric Double Layer ◽  
Viscoelastic Fluids ◽  
Shear Thinning ◽  
Time Periodic

Abstract In the present research, we address the implications of the pulsating electric field on controlling mass flow-rate characteristics for the time-periodic electro-osmotic flow of a viscoelastic fluid through a microchannel. Going beyond the Debye-Hückel linearization for the potential distribution inside the Electric Double Layer, the Phan-Thien-Tanner constitutive model is employed to describe the viscoelastic behaviour of the fluid. The analytical/semi-analytical expressions for the velocity distribution corresponding to a steady basic part, and a transient perturbed part are obtained by considering periodic pulsations in the applied electrical field. Our results based on sinusoidal pulsations reveal that enhanced shear thinning characteristics of the viscoelastic fluids show higher amplitude of pulsations with the oscillations in the velocity gradients primarily contrived within the Electric Double Layer region. The amplitude of mass flow rates increases with increasing the viscoelastic parameter , whereas, the phase lag displays a reverse trend. The analysis for an inverse problem is extended where the required magnitude of electric field pulsations for a target mass flow rate in the form of sinusoidal pulsations. It is found that with increasing shear-thinning characteristics of the viscoelastic fluid, there is a progressive reduction in the required electric field strength to maintain an aimed mass flow rate. Besides, required electric fields for controlled mass flow with triangular and trapezoidal pulsations are also determined.

Visualizations of Viscoelastic Fluid Flow in Microchannels

2008 ◽  
Author(s):  
F.-C. Li ◽  
H. Kinoshita ◽  
M. Oishi ◽  
T. Fujii ◽  
M. Oshima
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Newtonian Fluid ◽  
Viscoelastic Fluid ◽  
Flow Instability ◽  
Viscoelastic Fluids ◽  
Special Kind ◽  
Reynolds Numbers ◽  
Vortical Flow ◽  
Flow Phenomena

Solutions of flexible high-molecular-weight polymers or some kinds of surfactant can be viscoelastic fluids. The elastic stress is induced in such viscoelastic fluids and grow nonlinearly with the flow rate and results in many special flow phenomena, including purely elastic instability in the viscoelastic fluid flow. The elastic flow instability can even result in a special kind of turbulent motion, the so-called elastic turbulence, which is a newly discovered flow phenomenon and arises at arbitrary small Reynolds number. In this study, we experimentally investigated the peculiar flow phenomena of viscoelastic fluids in several different microchannels with curvilinear geometry by visualization technique. The viscoelastic working fluids were aqueous solutions of surfactant, CTAC/NaSal (cetyltrimethyl ammonium chloride/Sodium Salysilate). CTAC solutions with weight concentration of 200 ppm (part per million) and 1000 ppm, respectively, at room temperature were tested. For comparison, water flow in the same microchannels was also visualized. The Reynolds numbers for all the microchannel flows were quite small (for solution flows, the Reynolds numbers were smaller than 1) and the flow should be definitely laminar for Newtonian fluid. It was found that the regular laminar flow patterns for low-Reynolds number Newtonian fluid flow in different microchannels were strongly deformed in solution flows: either asymmetrical flow structures or time-dependent vortical flow motions appeared. These phenomena were considered to be induced by the viscoelasticity of the CTAC solutions.

Numerical Simulation of Heat Transfer Process of Viscoelastic Fluid Flow at High Weissenberg Number by Log-Conformation Reformulation

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Hong-Na Zhang ◽  
Dong-Yang Li ◽  
Xiao-Bin Li ◽  
Wei-Hua Cai ◽  
Feng-Chen Li
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Transfer Enhancement ◽  
Viscoelastic Fluid ◽  
Transfer Process ◽  
Viscoelastic Fluids ◽  
Heat Transfer Process ◽  
Weissenberg Number ◽  
Transfer Enhancement ◽  
Working Medium

Viscoelastic fluids are now becoming promising candidates of microheat exchangers’ working medium due to the occurrence of elastic instability and turbulence at microscale. This paper developed a sound solver for the heat transfer process of viscoelastic fluid flow at high Wi, and this solver can be used to design the multiple heat exchangers with viscoelastic fluids as working medium. The solver validation was conducted by simulating four fundamental benchmarks to assure the reliability of the established solver. After that, the solver was adopted to study the heat transfer process of viscoelastic fluid flow in a curvilinear channel, where apparent heat transfer enhancement (HTE) by viscoelastic fluid was achieved. The observed heat transfer enhancement was attributed to the occurrence of elastic turbulence which continuously mix the hot and cold fluids by the twisting and wiggling flow motions.

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