Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session X34: Non-Newtonian Flows: General |
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Chair: Antony Beris, University of Delaware Room: 201 |
Tuesday, November 21, 2023 8:00AM - 8:13AM |
X34.00001: Exploring the Influence of Wall Slip on Viscoplastic Saffman–Taylor Fingers Thomasina V Ball, Neil J Balmforth Viscoplastic Saffman-Taylor fingering in a Hele-Shaw cell is present when a Newtonian fluid displaces a viscoplastic fluid. Experimentally, the viscoplastic fluids typically used, such as Carbopol, suffer effective slip along the plate walls. This can dramatically alter the instability observed but is often ignored. |
Tuesday, November 21, 2023 8:13AM - 8:26AM |
X34.00002: Modeling and Simulation of Inhomogeneous Time-Dependent Poiseuille Pipe Flow of Aggregating Concentrated Suspensions Antony N Beris, Soham Jariwala, Norman J Wagner The development of appropriate models and an efficient methodology for the effective numerical simulation of transient pipe flows of aggregating suspensions fluids, exhibiting thixotropic and viscoelastic effects, is discussed. A pseudo-spectral method based on Chebyshev orthogonal polynomial spatial approximations is used. This numerical method has been validated against the analytical solution of Newtonian and upper-convected Maxwell fluids in oscillatory Poiseuille flows. |
Tuesday, November 21, 2023 8:26AM - 8:39AM |
X34.00003: Microstructural origins of shear thickening in dense suspensions William C Buchholtz, Vinutha H. A., Jeffrey S Urbach, Daniel L Blair, Emanuela Del Gado We investigate the possible microstructural underpinnings of shear thickening in dense suspensions through the behavior of both local and extended particle structures. As a model, we consider a simulated 2D suspension of soft disks at densities slightly below shear jamming in which the particles experience only frictional contact forces and Stokes drag. In this model the thickening flow exhibits several instances of distinct microstructure when compared with the thinning. In particular, the peaks of the pair correlation function reveal the emergence of straight, connected triplets of disks during the thickening which then buckle during the thinning. Equilateral triangles and symmetric quadrilaterals also show significant compression during the thinning when compared with the thickening. The emergence and ultimate deformation of these local structures suggests that during the thickening there is the growth of stress bearing particle networks. We confirm this by tracking the size and percolation of over-constrained strong force networks. This analysis shows that a percolation transition of these networks occurs during the thickening regime and disappears with the onset of the thinning. |
Tuesday, November 21, 2023 8:39AM - 8:52AM |
X34.00004: Lorentz force induced shear waves in a layer of a Maxwell fluid Sergio Cuevas, José Olvera-Orozco, Aldo Figueroa We numerically analyze the generation of shear waves in a two-dimensional region where an electrically conducting viscoelastic fluid is confined. By imposing a Lorentz force caused by the interaction of a unidirectional alternating electric current with a steady magnetic field produced by one or several magnetic dipoles, superimposed shear waves are created in an oscillating vortex pattern. The viscoelastic behavior of the fluid layer is modeled using the linearized Maxwell model, while it is assumed that the fluid has a low electrical conductivity, so that the induced electromagnetic effects are negligible. A vorticity – stream function formulation is used to solve the governing equations, assuming a low Reynolds number flow. The Womersley and Deborah numbers, along with the Lorentz force parameter, characterize the dynamics of the flow. According to the magnetic field configurations and the value of the dimensionless parameters, different vorticity maps are obtained which resemble electromagnetic radiation patterns. It is found that shear waves can cross the whole system and cause interference leading to constructive resonances that substantially increase the amplitude of the velocity profiles. The use of this system for mixing enhancement purposes is explored. |
Tuesday, November 21, 2023 8:52AM - 9:05AM |
X34.00005: Measurement of viscoelastic properties of a liquid using a rotating body of a general shape subjected to oscillatory shear Wook Ryol Hwang, Hye Jin Ahn We propose a systematic approach for measuring linear and non-linear viscoelastic properties of a liquid by the oscillatory motion of an immersed rotating body in a vessel. The shape of a rotating object is general and we tested four different types of impellers in the present work: a disk, an anchor, and two different flat bladed turbines. The effective shear stress was properly scaled with a torque through the expression of complex viscosity and the strain magnitude was scaled by the deflection angle with an effective shear rate coefficient (the Metzner-Otto constant). Three different concentrations of aqueous polyethylene oxide (PEO) solutions were tested and linear viscoelastic responses of storage and loss moduli were measured as a function of the oscillation frequency. In spite of the presence of non-rheometric and highly non-uniform flow field, comparison with the data from the conventional cone-and-plate and parallel-plate fixtures of a rheometer shows remarkably accurate measurement with at most 7% deviation within the frequency range from 0.01 [rad/s] to 100 [rad/s] for all the impeller geometries, except for the pitched bladed turbine. In addition, we show that this method can be applied to large amplitude oscillatory shear experiments for non-linear viscoelastic properties. The proposed method provides a versatile measurement for viscoelasticity, eliminating complicated issues in the conventional rheometry such as the wall slip, free surface evaporation/solidification and the edge fracture without a significant loss of accuracy. Furthermore, the method may facilitate the in-situ measurement of viscoelastic properties of a fluid within an industrial reactor/agitator as a tool for in-situ/on-line monitoring of microstructures. |
Tuesday, November 21, 2023 9:05AM - 9:18AM |
X34.00006: Capillary imbibition of shear-thinning fluids: from Lucas-Washburn to oscillatory regimes Pietro Poesio, Camille Steinik, Davide Picchi, Gianluca Lavalle The study of capillary imbibition has ramifications in many fields, such as energy, biology, process industry, and subsurface flows. Although the capillary rise of Newtonian liquids has been the subject of several studies since the seminal works of Lucas (1918) and Washburn (1921), its generalization to the case of non-Newtonian fluids is still an open question. To fill this gap, starting from first principles, we derive a transient one-dimensional model describing the rising dynamics of shear-thinning fluid, whose viscosity is described by the Ellis viscosity model. Our model identifies the scaling for the different imbibition regimes accounting for the interplay of inertial, gravity, and viscous non-Newtonian effects (i.e., the zero-shear-rate and the shear-thinning behaviour). Specifically, the rising dynamics is described by the interplay of three dimensionless parameters: the Richardson number, the Ellis number, and the shear-thinning index. At early times the system follows a universal inertial regime, followed by two possible limiting regimes, i.e., the classical Lucas-Washburn and the oscillatory regimes. The competition between the governing dimensionless numbers dictates the transition between the two. We show that when the viscous effect dominates over inertia, the identification of a (time-dependent) scaling law for the effective viscosity leads to a generalization of the Lucas-Washburn theory and the rescaled trajectories toward equilibrium collapse over the classical 1/2 scaling law. On the contrary, when inertia dominates the later stage of the imbibition, the filling length oscillates around the equilibrium. By means of linear control theory, we discuss the physical mechanisms that lead to such oscillating behaviour and map the different regimes in terms of the governing dimensionless parameters. |
Tuesday, November 21, 2023 9:18AM - 9:31AM |
X34.00007: Suppression of vortex-induced vibrations of a cylinder in inertial-viscoelastic flow Pieter R Boersma, Jonathan P Rothstein, Yahya Modarres-Sadeghi The study of vortex -induced vibrations (VIV) has been primarily focused on Newtonian fluids. Recently, there has been an interest in the VIV response of a cylinder in non-Newtonian flows. Previous work has examined the VIV response of a cylinder in an in-elastic, shear thinning fluid. Now we experimentally examine the response of a flexibly mounted rigid cylinder in a viscoelastic flow where fluid inertia and elasticity are important. The vortices in the wake of the cylinder become elongated and the amplitude response is suppressed. The traditional bell-dome amplitude response is altered to a triangular response and the lock-in range is reduced. The subcritical response is suppressed and the critical Reynolds number at which vortices shed in the fixed and flexibly mounted case become similar. The existence of a critical elastic number is discussed that captures the transition from a stable cylinder to an oscillating cylinder. |
Tuesday, November 21, 2023 9:31AM - 9:44AM |
X34.00008: Network modelling of yield-stress fluid flow in disordered porous media Elliott Sutton, Kohei Ohei, Maziyar Jalaal, Yuji Tasaka, Claudio P Fonte, Anne Juel Yield-stress fluid flow occurs in many industrial applications, including in porous systems during enhanced oil recovery and membrane emulsification. However, the high computational cost of computational fluid dynamics (CFD) simulations for yield-stress fluids hinders the study of these large-scale systems. In this work, we develop a fully-predictive network model for flow through 2D disordered porous media that obtains a solution in minutes on a single CPU core, considerably faster than the days or weeks required by CFD with multiple CPU cores. Our model generates network nodes using a Voronoi tessellation, extracts geometric parameters accounting for the topology of the domain, and numerically solves mass and momentum conservation equations with a Newton-Raphson solver. We accurately predict the pressure drop and velocity field of flows with and without wall slip, validating our results against CFD simulations produced in-house and from the literature. Wall slip is ubiquitous in real-world flows of these materials, dramatically decreasing friction at solid-fluid interfaces and changing the overall resistance in porous networks. Thus, it was imperative that we accounted for this phenomenon in our model. |
Tuesday, November 21, 2023 9:44AM - 9:57AM |
X34.00009: Computational modelling of the rheological response of wormlike micellar solutions in simple and complex deformations: flow past a sphere and contraction-expansion flow J. Esteban Lopez-Aguilar, Hamid R Tamaddon-Jahromi, Octavio Manero In this work, novel numerical solutions are provided on the flow of wormlike micellar solutions in both banding and non-banding regimes, in complex benchmark flows, such as flow past a sphere and a modified Couette contraction-expansion flow. The model used here is the latest model-variant of the Bautista-Manero-Puig family of constitutive equations, i.e. the BMP+_τp model [1-3]. The properties of this micellar rheological equation-of-state are exposed in simple ideal deformations, such as steady simple shear and uniaxial extension. Solutions in complex flow, in benchmark flow past-a-sphere and a modified contraction-expansion geometries, are obtained with our hybrid finite volume/element algorithm and expose the influence of the thixotropic and viscoelastic features of these models in flow-structure and yield-front representations. In flow past a sphere [2], in the mode of particle settling in wormlike micelles, location of a negative-wake instability is predicted, whilst for extremely concentrated wormlike micellar solutions, fore-aft asymmetries are observed, much resembling experimental finding for the settling of particles in viscoelastic Carbopol gels. In the modified Couette contraction-expansion flow cell [1], the influence of a complex-flow deformation in a shear-banded flow is studied, for which simple shear-banding features, i.e. flow segregation, are lost in the mixed inhomogeneous shear-to-extensional deformation found in the constriction zone, and are recovered in the fully-developed flow region downstream from the constriction. |
Tuesday, November 21, 2023 9:57AM - 10:10AM |
X34.00010: Anomalous crystalline ordering of particles in a viscoelastic fluid under high shear Sijie Sun, Nan Xue, Stefano Aime, Hyoungsoo Kim, Jizhou Tang, Gareth H McKinley, Howard A Stone, David A Weitz
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Tuesday, November 21, 2023 10:10AM - 10:23AM |
X34.00011: Elastic particle model for coil-stretch transition of dilute polymers in elongational flows Tong Gao The phenomenon of the "coil-stretch'" transition, wherein a long-chain polymer initially in a coiled state undergoes a sudden configuration change to become fully stretched under steady elongational flows, has been widely recognized. This transition can display intricate hysteresis behaviors under specific critical conditions, giving rise to unique rheological characteristics in dilute polymer solutions. Historically, microscopic stochastic models and Brownian dynamics simulations have shed light on the underlying mechanisms of the transition by uncovering bistable configurations of polymer chains. Following the initial work by Cerf(1952), we introduce a continuum model in this study to investigate the coil-stretch transition in a constant uniaxial elongational flow. Our approach involves approximating the unfolding process of the polymer chain as an axisymmetric deformation of an elastic particle. We make the assumption that the particle possesses uniform material properties, which can be represented by a nonlinear, strain-hardening constitutive equation to replicate the finite extensibility of the polymer chain. Subsequently, we analytically solve for the steady-state deformation using a polarization method. By employing this reduced model, we effectively capture the coil-stretch transition and establish its specific correlations with material and geometric properties. The hysteresis phenomena can be comprehended through a force-balance analysis, which involves comparing the externally applied viscous forces with the intrinsic elastic responsive forces. While simple, we demonstrate that our model provides a comprehensive understanding of the elastohydrodynamic nature of the coil-stretch transition, which is independent of any stochastic properties of polymers considered in microscopic models. |
Tuesday, November 21, 2023 10:23AM - 10:36AM |
X34.00012: Modeling polymeric lubricants with non-linear stress constitutive relations Luca Biancofiore, Humayun Ahmed Polymers are added to enhance the tribological performance of lubricating oils so that they can withstand the applied load and resist degradation due to thermal effects and high shear stress. However, their addition can lead to the onset of non-Newtonian effects, in particular viscoelasticity, measured via the Weissenberg number (Wi), i.e. the ratio between the polymer relaxation time and the shear time scale. In this work, we examine the effect of non-linear polymer traits, specifically (i) shear thinning and (ii) the finite polymer extensibility, on the load carrying capacity of the thin lubricating film via the viscoelastic Reynolds approach [Ahmed & Biancofiore, Journal of non-Newtonian Fluid Mechanics, 292, 104524] using constitutive relationships non linear in the stress, such as FENE-CR and FENE-P. We validate our approach by comparisons with direct numerical simulations of viscoelastic films in a parabolic slider bearing. Thereafter, we focus on a journal bearing whose geometry depends on its eccentricity ratio. Our results show that viscoelasticity has a strong impact on the load. Load is (i) enhanced initially for small values of Wi but decreases later at large Wi due to shear thinning), (ii) exhibits a non-linear dependence on the finite extensibility of the polymers, and finally (iii) is strenghtened (weakened) at low (high) eccentricity ratio. |
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