Viscoelastic Polymer Fluid Research Articles

Propulsion efficiency of achiral microswimmers in viscoelastic polymer fluids

AbstractWe report the effects of polymer size, concentration, and polymer fluid viscoelasticity on the propulsion kinematics of achiral microswimmers. Magnetically driven swimmer's step‐out frequency, orientation angle, and propulsion efficiency are shown to be dependent on fluid microstructure, viscosity, and viscoelasticity. Additionally, by exploring the swimming dynamics of two geometrically distinct achiral structures, we observe differences in propulsion efficiencies of swimmers. Results indicate that larger four‐bead swimmers are more efficiently propelled in fluids with significant elasticity in contrast to smaller 3‐bead swimmers, which are able to use shear thinning behavior for efficient propulsion. Insights gained from these investigations will assist the development of future microswimmer designs and control strategies targeting applications in complex fluids.

Reduced surface accumulation of swimming bacteria in viscoelastic polymer fluids

Surface-associated bacterial communities flourish in nature and in the body of animal hosts with abundant macromolecular polymers. It is unclear how the endowed viscoelasticity of polymeric fluids influences bacterial motile behavior in such environments. Here, we combined experiment and theory to study near-surface swimming of flagellated bacteria in viscoelastic polymer fluids. In contrast to the swimming behavior in Newtonian fluids, we discovered that cells swim in less curved trajectories and display reduced near-surface accumulation. Using a theoretical analysis of the non-Newtonian hydrodynamic forces, we demonstrated the existence of a generic lift force acting on a rotating filament near a rigid surface, which arises from the elastic tension generated along curved flow streamlines. This viscoelastic lift force weakens the hydrodynamic interaction between flagellated swimmers and solid surfaces and contributes to a decrease in surface accumulation. Our findings reveal previously unrecognized facets of bacterial transport and surface exploration in polymer-rich environments that are pertinent to diverse microbial processes and may inform the design of artificial microswimmers capable of navigating through complex geometries.

Verified simulation of the stationary polymer fluid flows in the channel with elliptical cross-section

This work is aimed at the numerical analysis of the stationary non-isothermal flows of an incompressible viscoelastic polymer fluid in the channels with elliptical cross-sections. The description of such flows is done on the basis of the mesoscopic approach, and the resolving equations are derived. For solving them three algorithms, which use different techniques of constructing the approximate solutions, are designed: the least-squares collocation method based on the piecewise polynomial approximations, which lead to the overdetermined systems of linear algebraic equations; the finite element method, which uses weak formulations; and the non-local method without saturation, which operates with the global approximations in the elliptical coordinate system and with the matrix Sylvester equations. The proposed algorithms are verified by solving the test problem with the known analytical solution. Further we use them for the numerical analysis of the polymer fluid flows with its parameters varying in wide ranges. Comparison of the results obtained by the different algorithms shows their high performance and confirms that the solution of the considered non-linear problem exists and that it was computed accurately. The singularities of the obtained stationary solutions are analyzed. Taking them into account within the proposed algorithms enables us to increase the accuracy and the speed of simulations.

High Accuracy Numerical Simulation of Non-Isothermal Viscoelastic Polymer Fluid Past a Cylinder

The collocated grid finite volume CLEAR (coupled and linked equations algorithm revised) method is applied to solve the governing equations of viscous and XPP (eXtended Pom-Pom) viscoelastic fluids. The high accuracy AVLSMART schemes for the convection terms of momentum and constitutive equations are constructed based on the deferred correction method. Firstly, the incompressible viscous fluids past a cylinder at different Reynolds are simulated to verify the validity of the developed numerical method. Then, the isothermal and non-isothermal XPP viscoelastic fluid past a cylinder is studied numerically, giving the distribution patterns of velocity vectors, stress components, stretch and temperature. Especially, the effects of Weissenberg on the horizontal velocity, normal stresses and stretch are analyzed. The results obtained in this research will provide the theoretical foundation for accurately predicting fiber reinforced viscoelastic polymer dynamic filling process in complex cavities.

Numerical simulation of a stabilizing Poiseuille-type polymer fluid flow in the channel with elliptical cross-section

This work is devoted to the numerical analysis of stabilization of the incompressible viscoelastic polymer fluid flow in the channel with elliptical cross-section. To describe the flow, mesoscopic rheological relations are used, and resolving non-stationary equations are derived. For solving them a special pseudo-spectral method is developed and implemented. As time increases, under certain conditions on the parameters of flow the solution to the non-stationary problem stabilizes and converges to the one of three branches of the solution to the corresponding stationary problem. It is shown that the variation of the parameters describing polymer microstructure leads to the switch of stabilized solution between these branches. The work provides the results of simulation of the flow stabilization and the analysis of the threshold values of parameters at which the switching occurs.

Derivation of linear and nonlinear acoustic systems for an incompressible viscoelastic polymer fluid

Derivation of linear and nonlinear acoustic systems for an incompressible viscoelastic polymer fluid

Derivation of Linear and Nonlinear Acoustic Systems for an Incompressible Viscoelastic Polymer Fluid

Under discussion is the the so-called acoustic systems (in linear and nonlinear cases) for the system of equations describing the movement of incompressible viscoelastic polymer fluid. We also consider some approximations of these systems.

Flow behaviors of a viscoelastic polymer solution at 3D micro pore-throat structure

Polymers are abundantly used in oil production industry, especially in enhanced oil recovery process. The underground oil reservoir is a kind of porous media where complex microscopic geometries lead to strong shearing and extensional components. This research focuses on a novel method used to investigate the flow behaviors of hydrolyzed polyacrylamide solution at a micro pore-throat structure with a comparison with Newtonian flow of water. For polymer solution, the flow velocimetry revealed the viscoelastic flow has two main characters compared with Newtonian fluid. First, the instability or non-linearity of polymer flows led to bending and distorted streamlines. The instability of the flow is mainly caused by the growth of high stress generated in the viscoelastic polymer fluid as it accelerates and decelerates into and out from the narrow throat, respectively speaking. The second character is the back-streams at the outlet of the throat.

Asymptotic Formula for the Spectrum of the Linear Problem Describing Periodic Polymer Flows in an Infinite Channel

In this paper, we study a new rheological model (a modification of the well-known Pokrovskii–Vinogradov model) which is shown by computational experiments to take into account the nonlinear effects occurring during melt flows and polymer solutions in regions with complex boundary geometry. For the case where the main solution is an analogue of the Poiseuille flow in an infinite flat channel (viscoelastic polymer fluid considered), an asymptotic formula is obtained for the distribution of points of the spectrum of the linear problem. It is shown that small perturbations have the additional property of periodicity in the variable that runs along the axis of the channel.

Estimation of Two Error Components in the Numerical Solution to the Problem of Nonisothermal Flow of Polymer Fluid between Two Coaxial Cylinders

An algorithm for solving a stationary nonlinear problem of a nonisothermal flow of an incompressible viscoelastic polymer fluid between two coaxial cylinders is developed on the basis of Chebyshev approximations and the collocation method. In test calculations, the absence of saturation of the algorithm is shown. A posteriori estimates of two error components in the numerical solution—the error of approximation method and the round-off error—are obtained. The behavior of these components as a function of the number of nodes in the spatial grid of the algorithm and the radius of the inner cylinder is analyzed. The calculations show exponential convergence, stability to rounding errors, and high time efficiency of the algorithm developed.

Steady-state flow of an incompressible viscoelastic polymer fluid between two coaxial cylinders

A boundary value problem for a quasi-linear equation determining the velocity profile of a flow of a polymer fluid in a pipe formed by two coaxial cylinders is considered. On the basis of methods of approximation without saturation, a computational algorithm of increased accuracy is developed, making it possible to solve the problem in a wide range of parameters, including record-low values of r 0, the radius of the inner cylinder.

On the IAA version of the Doi–Edwards model versus the K-BKZ rheological model for polymer fluids: A global existence result for shear flows with small initial data

This paper establishes the existence of smooth solutions for the Doi–Edwards rheological model of viscoelastic polymer fluids in shear flows. The problem turns out to be formally equivalent to a K-BKZ equation but with constitutive functions spanning beyond the usual mathematical framework. We prove, for small enough initial data, that the solution remains in the domain of hyperbolicity of the equation for all t≥0.

Linear instability of solutions in a mathematical model describing polymer flows in an infinite channel

A new rheological model describing flows of incompressible viscoelastic polymer fluid is studied. Lyapunov’s linear instability of the Poiseuille flow counterpart for the Navier-Stokes equations in a plane infinite channel is proven.

The Flow of Viscoelastic Polymer Solution in Porous Media

A novel flow model of viscoelastic polymer solution flowing in porous media is established and the degradation is also considered. The new model is more accurate to describe the rheological characteristics and flow characterization of viscoelastic polymer solution and should be useful for the analysis of mechanism associated with seepage of non-Newtonian fluids and gels. The results illustrate that it is the constitutive equation that makes the seepage law of viscoelastic polymer fluid different from that of viscous fluid. Tensile stress was added to the constitutive equation of viscoelastic polymer fluid while the rheology law of Newtonian fluid is mainly controlled by shearing stress. Polymer fluid properties, porous media structure and seepage velocity can all influence the viscoelastic effect of polymer fluid.

Nonlinear Evolution of the Travelling Waves in Roll Coating Flows of Thin Viscoelastic Polymer Falling Films

Roll coating is widely used to apply a thin liquid film to a continuous, flexible substrate. It is known that macroscopic instabilities of the film system can result in a non-homogenous film growth to fluid flow. The influence of the Rossby number, the viscoelastic parameter, and the roller radius on the nonlinear hydrodynamic stability of a thin viscoelastic polymer fluid film coating flow down a rotating vertical roller is investigated. In contrast to most previous studies, the solution scheme employed in this study is based on a numerical approximation approach rather than an analytical method. The size of the explosive supercritical instability region increases significantly as the roller rotates. It is shown that the stability of the liquid film is enhanced by reducing the viscoelastic effect or decreasing the speed of the rotating roller. At higher values of the Reynolds number, the tendency of the rotation effect to prompt thin-film instability increases with an increasing roller radius.

Visco-elastic flow past circular cylinders mounted in a channel: experimental measurements of velocity and drag

Experimental results are described of a flow in a rectangular channel with a width of 20 mm and a height of 0.16 m. In the symmetry plane of this channel we can mount one or two cylinders each with a diameter of 10 mm. In the case of the two cylinders they are displaced with respect to each other in the streamwise direction. In this set-up, the velocity field is measured by means of Laser Doppler Velocimetry (LDV) under various flow conditions and along various traverses. First, a reference experiment is carried out with a Newtonian fluid. For this Newtonian case we have also carried out a numerical computation which can be used to test the accuracy of our measuring system. The computational results agree excellently with the experimental data. The computations also show that the flow in the channel cannot be considered as 2D. After this a series of experiments are discussed which have been carried out with visco-elastic polymer fluids. Material parameters of the fluids, such as the shear viscosity and the first normal stress difference, are obtained with help of rheometric measurements. For the visco-elastic polymer fluids our observations indicate differences with the Newtonian case, especially, in the wake of the cylinders when the velocity is increased. Eventually, at some critical velocity elastic instabilities occur. Finally, we note that, while in a Newtonian fluid the drag varies linearly with the flow rate, this is no longer the case in a visco-elastic fluid, where we find that the drag increases with the square of the flow rate.

Weakly nonlinear subcritical instability of visco-elastic Poiseuille flow

It is well known that the Poiseuille flow of a visco-elastic polymer fluid between plates or through a tube is linearly stable in the zero Reynolds number limit, although the stability is weak for large Weissenberg numbers ( Wi ). In this paper, we argue that recent experimental and theoretical work on the instability of visco-elastic fluids in Taylor–Couette cells and numerical work on channel flows suggest a scenario in which Poiseuille flow of visco-elastic polymer fluids exhibits a nonlinear “subcritical” instability due to normal stress effects, with a threshold which decreases for increasing Weissenberg number. This proposal is confirmed by an explicit weakly nonlinear stability analysis for Poiseuille flow of an UCM fluid. Our analysis yields explicit predictions for the critical amplitude of velocity perturbations beyond which the flow is nonlinearly unstable, and for the wavelength of the mode whose critical amplitude is smallest. The nonlinear instability sets in quite abruptly at Weissenberg numbers around 4 in the planar case and about 5.2 in the cylindrical case, so that for Weissenberg numbers somewhat larger than these values perturbations of the order of a few percentage in the wall shear stress suffice to make the flow unstable. We have suggested elsewhere that this nonlinear instability could be an important intrinsic route to melt fracture and that preliminary experiments are both qualitatively and quantitatively in good agreement with these predictions.

Special Requirements of the Flow System and Equipment for Viscoelastic Polymer Fluids

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 77496, "Rheology and Special Requirements on the Flow System and Equipment for Large-Scale Injection, Production, and Gathering of Viscous-Elastic Polymer Fluids in Chemical Floods and Methods to Solve the Problems That Emerge," by Wang Demin, SPE, Jiang Youlin, Wang Yan, SPE, Gong Xiaohong, and SPE, Wang Gang, SPE, Daqing Oil Co. Ltd., originally presented at the 2002 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 29 September-2 October.

Nonlinear phenomena in flows of viscoelastic polymer fluids. A. I. Leonov and A. N. Prokunin. Chapman & Hall, London, 1994. pp. xvi + 475, price £89.00. ISBN-0-412-58200-7

Polymer InternationalVolume 40, Issue 2 p. 152-152 Book Review Nonlinear phenomena in flows of viscoelastic polymer fluids. A. I. Leonov and A. N. Prokunin. Chapman & Hall, London, 1994. pp. xvi + 475, price £89.00. ISBN-0-412-58200-7 T. D. Papathanasiou, T. D. PapathanasiouSearch for more papers by this author T. D. Papathanasiou, T. D. PapathanasiouSearch for more papers by this author First published: June 1996 https://doi.org/10.1002/pi.1996.210400212AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume40, Issue2June 1996Pages 152-152 RelatedInformation

Nonlinear phenomena in flows of viscoelastic polymer fluids

Highly ordered honeycomb films were produced from arborescent graft polystyrene (AGPS) solutions using breath figures (BF). The structure of the BF pattern (whether single layered or multilayered) of pores depended on several factors such as the type of solvent used (CS2 or CHCl3), the length of the side chains, the generation number and the concentration of the polymer. When solutions of AGPS with shorter side chains (Mw ∼ 5000 g/mol) were used for the BF process, arborescent polymers generated a multilayer pore structure. However, when polymers with longer side chains (Mw ∼ 30,000 g/mol) were used, monolayer pore structures were mostly generated. The regularity and surface quality of the honeycomb pattern became worsened as the multilayered structures formed. The polymer concentration (ϕ) also played a critical role in determining the morphology of the BF films. Higher ϕ led to a multilayer pore structure while lower ϕ resulted in a monolayer pore structure. In general, the regularity of top layer pores was found to decrease with increasing generation number. The introduction of multiwall carbon nanotubes (MWCNTs) into AGPS solutions and application of the BF process using the solution blends yielded patterned hybrid films. SEM images showed that some CNTs were loaded into the honeycomb pattern of AGPS, but that most MWCNTs precipitated to form the bottom layer. In this work, the influence of concentration and surface modification of MWCNTs on the BF patterns obtained is discussed.