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Dynamics of a viscoelastic droplet migrating in a ratchet microchannel under AC electric field J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-04-17 Anant Kumar Nema, Manoj Kumar Tripathi
Droplet-based microfluidic devices can be powered or manipulated by applying an external electric field, and the ability to precisely control the flow in such devices is essential for various engineering and biomedical applications. In this numerical study, we investigate the deformation dynamics of a viscoelastic droplet in a ratchet microchannel under the influence of an AC electric field. We employ
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Slot coating of viscoplastic materials: A computational study of the effects of viscoplasticity on the flow dynamics and low-flow limit J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-03-23 I.R. Siqueira, R.L. Thompson, M.S. Carvalho, P.R. de Souza Mendes
Yield-stress materials such as structurally complex formulations of paints, slurries, and waxes have been long ubiquitous in the coating industry, though the practice of coating engineering remains largely empirical as the fundamental role of viscoplasticity due to the yield stress of the coating material in most coating applications is still unclear. Here, we couple a recent harmonic mean viscosity
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Impact of drops of a nanoparticle dispersion in a viscoelastic liquid J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-03-22 Takshak Shende, Ian Eames, Mohammad Hadi Esteki, Yousef Javanmardi, Emad Moeendarbary
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Modeling Elongational Rheology of Model Poly((±)-lactide) Graft Copolymer Bottlebrushes J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-03-20 Manfred H. Wagner, Aristotelis Zografos, Valerian Hirschberg
The shear and elongational rheology of graft polymers with poly(norbornene) backbone and one poly(()-lactide) side chain of length N = 72 per two backbone repeat units (grafting density ) was investigated recently by Zografos et al. [Macromolecules 56, 2406–2417 (2023)]. Above the star-to-bottlebrush transition at backbone degrees of polymerization of N>70, increasing strain hardening was observed
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Elasto-visco-plastic flows in benchmark geometries: I. 4 to 1 planar contraction J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-03-19 Milad Mousavi, Yannis Dimakopoulos, John Tsamopoulos
We present predictions for the flow of elastoviscoplastic (EVP) fluids in the 4 to 1 planar contraction geometry. The Saramito-Herschel-Bulkley fluid model is solved via the finite-volume method with the OpenFOAM software. Both the constitutive model and the solution method require using transient simulations. In this benchmark geometry, whereas viscoelastic fluids may exhibit two vortices, referred
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Numerical investigation of turbulent flow of Herschel–Bulkley fluids in a concentric annulus with inner cylinder rotation J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-03-19 Felipe O. Basso, Admilson T. Franco
In the present work, under-resolved direct numerical simulation (UDNS) is used to study the turbulent flow of Herschel–Bulkley fluids in a concentric annular region with the rotation effect of the inner cylinder. The current numerical method is verified against the first- and second-order statistics of the velocity field with the large-eddy simulation (LES) data available in the literature for the
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Growth and static stability of bubble clouds in yield stress fluids J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-03-19 Masoud Daneshi, Ian A. Frigaard
This study explores the growth and static stability of bubble clouds in yield-stress fluids using an experimental approach. Carbopol gels with varying concentrations and initial gas contents as well as Laponite gels are used as model yield stress fluids in our experiments. A vacuum system is exploited to generate the bubbles and control their growth in the gels. The focus of this study is on determining
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The Gordon–Schowalter/Johnson–Segalman model in parallel and orthogonal superposition rheometry and its application in the study of worm-like micellular systems J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-03-14 A. Ogunkeye, R. Hudson-Kershaw, A.R. Davies, D.J. Curtis
Parallel and Orthogonal Superposition experiments may be employed to probe a material’s non-linear rheological properties through the rate-dependent parallel and orthogonal superposition moduli, and , respectively. In a recent series of publications, we have considered the problem of interconversion between parallel and orthogonal superposition moduli as a means of probing flow induced anisotropy.
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The effects of suspending fluid viscoelasticity on the mechanical properties of capsules and red blood cells in flow J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-28 Boon Siong Neo, Eric S.G. Shaqfeh
The mechanical behavior of spherical capsules and red blood cells in shear and confined pressure-driven flow of polymeric fluids was studied computationally. In particular, we study the effect of suspending fluid elasticity on the steady mechanical behavior of spherical capsules and red blood cells suspended in an Oldroyd-B fluid, in dilute shear and confined pressure-driven flow, as a model system
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The polymer diffusive instability in highly concentrated polymeric fluids J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-27 Theo Lewy, Rich Kerswell
The extrusion of polymer melts is known to be susceptible to ‘melt fracture’ instabilities, which can deform the extrudate, or cause it to break entirely. Motivated by this, we consider the impact that the recently discovered polymer diffusive instability (PDI) can have on polymer melts and other concentrated polymeric fluids using the Oldroyd-B model with the effects of polymer stress diffusion included
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Semi-analytical solutions of Newtonian fluid-FENE-P fluid core annular flow J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-22 Yuying Guo, Jiaqiang Jing, Jie Sun
Water-lubricated transportation of viscous oil is an important application of core annular flow (CAF), which significantly reduces friction pressure drop and saves pump power. However, the core oil floats up due to the density difference of oil and water, causing instability and even destruction of CAF, which restricts the application and development of the drag reduction technology. The viscoelastic
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Numerical simulations of the Oldroyd-B fluid flow around triangular cylinders with different orientations J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-22 Fanji Sun, Xiaoyu Wen, Xinhui Si, Chiyu Xie, Botong Li, Limei Cao, Jing Zhu
This study numerically simulates the two-dimensional flow of Oldroyd-B fluid around an isosceles right-angled triangular cylinder with five orientations. The log-conformation reformulation is employed to stabilize the numerical simulations. By adjusting the triangular orientation angle (), three types of fluids development process can be observed: from steady to vortex shedding at and , keeping the
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Viscoplastic flows in superhydrophobic channels with oriented grooves: From anisotropic slip to secondary flow J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-15 H. Rahmani, S.M. Taghavi
In this work, Poiseuille flows of viscoplastic fluids in typically thin channels equipped with a superhydrophobic groovy wall are numerically studied. The orientation of the groove relative to the applied pressure gradient can vary, and this orientation is measured via the groove orientation angle (). In particular, longitudinal (), oblique (), and transverse () flow configurations are considered.
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Mist-control of polyalphaolefin (PAO) lubricants using long pairwise end-associative polymers J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-12 Red C. Lhota, Robert W. Learsch, Jacob Temme, Vincent Coburn, Julia A. Kornfield
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A finite-volume framework to solve the Fokker–Planck equation for fiber orientation kinetics J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-12 Dogukan T. Karahan, Devesh Ranjan, Cyrus K. Aidun
In this work, a new solver, FPSolve, is developed to study fiber orientation kinetics using the Fokker–Planck (FP) equation. The solver employs the finite-volume method. The FP equation is discretized on unstructured cubed-sphere grids using the centered differencing scheme (CDS) or a blend of the CDS and the upwind differencing scheme. Time integration is performed using a second-order two-stage explicit
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Tricritical state and quasi-periodicity triggered by the non-linear elasticity in an Upper Convected Maxwell fluid confined between two co-oscillating cylinders about zero-mean J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-12 Mohamed Hayani Choujaa, Mehdi Riahi, Saïd Aniss
The effects of harmonically co-oscillating the inner and outer cylinders about zero mean rotation in a Taylor–Couette flow are examined numerically using Floquet theory, for the case where the fluid confined between the cylinders obeys the upper convected Maxwell model. Although stability diagrams and mode competition involved in the system were clearly elucidated recently by Hayani Choujaa et al.
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The elastic perfectly plastic constitutive equation for yield stress fluids J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-10 Kamil Fedorowicz, Robert Prosser
We explore the use of an (EPP) constitutive equation for the modelling of yield stress fluids. Contrary to many other models, stresses in the EPP model arise from elastic deformation rather than as a viscous effect. In this paper, the EPP model is coupled to a standard viscous treatment of the post-yield flow stresses to produce Bingham-like behaviour, and the timescale associated with the yielding
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Mixing in heterogeneous fluids: An examination of fluid property variations J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-09 Mohammad Reza Daneshvar Garmroodi, Ida Karimfazli
In the context of stirred tanks, “mixing” refers to the purposeful and controlled flow designed to minimize heterogeneity, such as variations in solute or additive concentration. Industries like food and polymer processing often encounter situations where fluid properties are closely tied to additive concentration. However, conventional engineering models of mixing, herein referred to as “homogeneous
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A multiscale framework for polymer modeling applied in a complex fluid flow J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-08 Kosar Khajeh, Deboprasad Talukdar, Gentaro Sawai, Hitoshi Washizu
Understanding polymer dynamics under shear flow is crucial for studying their rheological behavior in diverse applications. However, conventional micro analyses provide limited insights into polymer elongation and conformation. To address this, we propose a hybrid model combining the Lattice Boltzmann method and Langevin Dynamics technique, which captures the multiscale nature of polymer dynamics.
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The steady and unsteady regimes in a cubic lid-driven cavity with viscoplastic fluid solved with the lattice Boltzmann method J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-02-02 Marco A. Ferrari, Admilson T. Franco
This work builds upon the previously published analysis of a lid-driven cavity filled with viscoplastic fluid. We extend the study from a two-dimensional case to a three-dimensional one, employing the moment representation of the lattice Boltzmann method to obtain numerical results. The findings expand the existing dataset, which can potentially serve as benchmark results for inertial regimes of viscoplastic
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Multiscale simulations for polymer melt spinning process using Kremer–Grest CG model and continuous fluid mechanics model J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-01-30 Yan Xu, Yuji Hamada, Takashi Taniguchi
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Elastoviscoplasticity intensifies the unstable flows through a micro-contraction geometry J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-01-20 A. Chauhan, C. Sasmal
This study focuses on the two-dimensional numerical investigation of complex fluid flows through a micro-contraction geometry in the creeping flow regime, specifically examining elastoviscoplastic (EVP) fluids. These fluids exhibit a combination of viscous, elastic, and plastic behaviors. The governing equations, including mass and momentum, are solved using a finite volume method-based discretization
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Quantitative description of polymer drag reduction: Effect of polyacrylamide molecular weight distributions J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-01-17 Lukas Brandfellner, Emina Muratspahić, Alexander Bismarck, Hans Werner Müller
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On the use of time-dependent fluids for delaying onset of transition to turbulence in the flat plate boundary-layer flow: A passive control of flow J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2024-01-04 Danial Rezaee
Inelastic time-dependent fluids display continuous and reversible changes in viscosity when subjected to a constant shear-rate. These alterations arise from the gradual modification of the material’s microstructure due to shear-induced effects, known as shear rejuvenation. When this process generates smaller structural units, it is termed thixotropy; conversely, if it produces larger units, it is labeled
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Flow instabilities in circular Couette flow of wormlike micelle solutions with a reentrant flow curve J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-12-27 Richard J. Hommel, Michael D. Graham
In this work, we numerically investigate flow instabilities of inertialess circular Couette flow of dilute wormlike micelle solutions. Using the reformulated reactive rod model (RRM-R) (Hommel and Graham, 2021), which treats micelles as rigid Brownian rods undergoing reversible scission and fusion in flow, we study the development and behavior of both vorticity banding and finger-like instabilities
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Effect of die exit flow conditions on air-gap film dynamics in two-dimensional film casting processes: Short Communication J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-12-22 Geunyeop Park, Ho Suk Ji, Joo Sung Lee, Hyun Wook Jung, Jae Chun Hyun
The impact of the inlet velocity profile at the die exit on the film dynamics within the air-gap region was investigated using numerical simulations for both Newtonian and viscoelastic Phan-Thien and Tanner (PTT) fluids in isothermal two-dimensional (2-D) film casting processes. In an industrial context, intentional adjustments were made to reduce the inlet velocities at the edge of the casting die
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Maximum drag enhancement asymptote in turbulent Taylor–Couette flow of dilute polymeric solutions J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-12-14 Fenghui Lin, Jiaxing Song, Nansheng Liu, Zhenhua Wan, Xi-Yun Lu, Bamin Khomami
Direct numerical simulations in a wide-gap turbulent viscoelastic Taylor–Couette flow in the Reynolds number (Re) range of 1500 to 8000 reveals the existence of a maximum drag enhancement (MDE) asymptote. The statistical properties associated with the turbulent and polymer dynamics demonstrate that the turbulent drag enhances with the increase of the Weissenberg number (Wi) and eventually saturates
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Global stability of Oldroyd-B fluids in plane Couette flow J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-12-16 Joshua Binns, Andrew Wynn
We prove conditions for global nonlinear stability of Oldroyd-B viscoelastic fluid flows in the Couette shear flow geometry. Global stability is inferred by analysing a new functional, called a perturbation entropy, to quantify the magnitude of the polymer perturbations from their steady-state values. The conditions for global stability extend, in a physically natural manner, classical results on global
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Suppression of vortex-induced vibrations of a cylinder in inertial-elastic flow J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-12-12 Pieter R. Boersma, Jonathan P. Rothstein, Yahya Modarres-Sadeghi
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Creeping thermocapillary motion of a Newtonian droplet suspended in a viscoelastic fluid J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-12-09 Paolo Capobianchi, Mahdi Davoodi, Robert J. Poole, Marcello Lappa, Alexander Morozov, Mónica S.N. Oliveira
In this work we consider theoretically the problem of a Newtonian droplet moving in an otherwise quiescent infinite viscoelastic fluid under the influence of an externally applied temperature gradient. The outer fluid is modelled by the Oldroyd-B equation, and the problem is solved for small Weissenberg and Capillary numbers in terms of a double perturbation expansion. We assume microgravity conditions
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Exploring multi-stability in three-dimensional viscoelastic flow around a free stagnation point J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-12-09 Daniel W. Carlson, Amy Q. Shen, Simon J. Haward
Fluid elements passing near a stagnation point experience finite strain rates over long persistence times, and thus accumulate large strains. By the numerical optimization of a microfluidic 6-arm cross-slot geometry, recent works have harnessed this flow type as a tool for performing uniaxial and biaxial extensional rheometry (Haward et al., 2023 [5,6]). Here we use the microfluidic ‘Optimized-shape
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A universal rescaling law for the maximum spreading factor of non-Newtonian droplets with power-law fluids J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-25 Hailong Liu, Jiaqi Chen, Junfeng Wang
The maximum spreading diameter of non-Newtonian fluid droplets impacting on the solid surface is a key concern in a variety of industrial and medical applications. In this work, we focus on the effect of the shear-thinning, one of the most important non-Newtonian properties, on the spreading dynamics of impacting droplets. A finite element scheme combined with a phase field method and dynamic contact
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Simulation of blood flow in a stenosed and bifurcating artery using Finite Volume Methods and OpenFOAM J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-23 Sunitha Nagarathnam, Tiri Chinyoka
The article focuses on the shear-thinning and viscoelastic constitutive modelling and numerical simulation of blood flow in a stenosed and bifurcating artery. Specifically, the shear-thinning and viscoelastic behaviour of blood are modelled and implemented via the Oldroyd-B and Generalized Oldroyd-B constitutive models. A robust and efficient general purpose numerical (and computational) methodology
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Viscoelastic flow asymmetries in a helical static mixer and their impact on mixing performance J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-23 T.P. John, R.J. Poole, A. Kowalski, C.P. Fonte
Helical static mixers are often used during the processing of formulated products with complex rheological properties, such as viscoelasticity. Previous experimental studies have highlighted that increasing the viscoelasticity of the flow hinders the mixing performance in the laminar flow regime. In this study, we use computational fluid dynamics to investigate the flow of a FENE-CR model fluid in
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A network model for gas invasion into porous media filled with yield-stress fluid J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-20 A. Pourzahedi, I.A. Frigaard
This study investigates the gas invasion into a porous medium filled with a yield-stress fluid. A pore–throat network model is employed to represent the porous media, and a semi-analytical approach is used for simulating the gas propagation. The effect of throat radii, fluid yield stress and network size on the exit time and gas volume fraction retained inside the porous medium are explored. The stability
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A robust numerical strategy for finding surface waves in flows of non-Newtonian liquids J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-13 Bruno P. Chimetta, Erick M. Franklin
Gravity-driven flows of liquid films are frequent in nature and industry, such as in landslides, lava flow, cooling of nuclear reactors, and coating processes. In many of these cases, the liquid is non-Newtonian and has particular characteristics. In this paper, we analyze numerically the temporal stability of films of non-Newtonian liquids falling by gravity, on the onset of instability. The liquid
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Uncertainty quantification for the squeeze flow of generalized Newtonian fluids J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-14 Aricia Rinkens, Clemens V. Verhoosel, Nick O. Jaensson
The calibration of rheological parameters in the modeling of complex flows of non-Newtonian fluids can be a daunting task. In this paper we demonstrate how the framework of uncertainty quantification (UQ) can be used to improve the predictive capabilities of rheological models in such flow scenarios. For this demonstration, we consider the squeeze flow of generalized Newtonian fluids. To systematically
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Wormlike Micelles revisited: A comparison of models for linear rheology J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-14 Joseph D. Peterson, Weizhong Zou, Ronald G. Larson, Michael E. Cates
We review a selection of models for wormlike micelles undergoing reptation and chain sequence rearrangement (e.g. reversible scission) and show that many different assumptions and approximations all produce similar predictions for linear rheology. Therefore, the inverse problem of extracting quantitative microscopic information from linear rheology data alone may be ill-posed without additional supporting
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Designing a swimming rheometer to measure the linear and non-linear properties of a viscoelastic fluid J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-13 Boon Siong Neo, Eric S.G. Shaqfeh
At low Reynolds numbers, “swirlers” – swimmers with an axisymmetric “head” and “tail” counterrotating about the axis of symmetry – generate no net propulsion in a Newtonian fluid as a consequence of the “scallop theorem”. Viscoelasticity in the suspending fluid breaks the time-reversibility and allows swirlers to propel themselves, with the swim speed being a function of swimmer geometry, fluid elasticity
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Analytical solution for channel flow of a Giesekus fluid with non-zero solvent viscosity J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-13 Irene Daprà, Giambattista Scarpi
A semi analytical solution is obtained here for the fully developed plane Poiseuille flow of a Giesekus fluid with a Newtonian solvent. The fluid behaviour is described using the Deborah number, the mobility factor and an appropriate ratio of fluid viscosity to total viscosity as parameters. The given solution shows that the velocity increases significantly with rising the polymer concentration, confirming
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Pore-scale hydrodynamics of non-Newtonian power-law fluids across a partially blocked porous medium in a confined channel J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-08 Subhasisa Rath, Alexandros Terzis
Transport of non-Newtonian fluids in porous media is pervasive in many natural and industrial applications. However, capturing the rheological behaviors of fluids by direct experimental techniques is challenging at the pore-scale. This paper outlines the pore-scale hydrodynamic interactions of non-Newtonian power-law fluids across a partially blocked porous medium in the laminar flow regime by computational
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The similarity theory of free turbulent shear flows of viscoelastic fluids J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-08 Mateus C. Guimarães, Fernando T. Pinho, Carlos B. da Silva
A new theory is formulated for the description of the conformation state of the polymer chains in free turbulent shear flows of viscoelastic fluids. Using self-similarity arguments and new scaling relations for the turbulent flux of conformation tensor we show the existence of minimum and maximum solvent dissipation reduction asymptotes, and four different polymer deformation regimes. The similarities
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Elastic stability of viscoelastic liquid films flowing on a porous substrate J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-10-30 Zhiwei Song, Zijing Ding
This paper investigates the linear stability of viscoelastic liquid films flowing down an inclined porous substrate analytically and numerically. It focuses on the Stokes flow of viscoelastic films and uncovers two unstable modes triggered by elasticity. The elastic surface mode with a long wave number is solved analytically and numerically. Our results also indicate elasticity can trigger an elasto-porous
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Predictions of the Behavior of a Single Droplet and Blends Composed of Newtonian/Viscoelastic Minor Phase and Viscous Major Phase Subjected to Oscillatory Shear Flow J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-11-03 Abdulwahab S. Almusallam, T.B. Bini
The oscillatory behavior of Newtonian and viscoelastic droplets in a Newtonian phase and blends composed of viscoelastic minor phase in a Newtonian major phase are theoretically investigated in this work. The non-Newtonian constrained volume model predictions are compared to experimental oscillatory shearing flow data of droplet and blends that are available in the literature. For a Newtonian droplet
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Application of Cross model for granular flow and impact analysis using three-dimensional B-spline material point method J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-10-19 Xiaomin Zhou, Yunjun Hua, Zheng Sun
Granular flow and impact, such as landslides and debris flows, are typical problems involving large deformations of non-Newtonian free surfaces, which are of great interest in geological engineering and also pose challenges for traditional mesh-based numerical methods. As an enhancement of the traditional Material Point Method (MPM), the B-Spline Material Point Method (BSMPM) can not only effectively
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Fine characterization of the capillary instability of free viscoelastic jets J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-10-17 Christophe Dumouchel, Louise Cottier, Marie-Charlotte Renoult
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Wall-modeled large-eddy simulation of turbulent non-Newtonian power-law fluid flows J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-10-17 Mohammad Taghvaei, Ehsan Amani
For high-fidelity predictions of turbulent flows in complex practical engineering problems, the Wall-Modeled (WM) Large-Eddy Simulation (LES) has aroused great interest. In the present study, we prove that the conventional Wall-Stress Models (WSMs) developed for WMLES of Newtonian fluids fail to predict the shear-thinning-induced drag reduction in power-law fluids. Therefore, we propose novel algebraic
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Incorporating the complex rheological behavior of blood in microvascular network simulations: Two-phase modeling and a model reduction approach J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-10-13 Christos Psevdos, Konstantinos Giannokostas, Pantelis Moschopoulos, Yannis Dimakopoulos, John Tsamopoulos
Vessel flow resistance in microvascular network simulations is often computed using the single-phase approximation, where the no-slip boundary condition is imposed on the microvessel wall, and the "in vitro viscosity law" or "the relative hematocrit" relationships proposed by Pries et al. (1992) are utilized. However, these models have limitations due to their reliance on experimental data, which inherently
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An eigenvalue-free implementation of the log-conformation formulation J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-10-12 Florian Becker, Katharina Rauthmann, Lutz Pauli, Philipp Knechtges
The log-conformation formulation, although highly successful, was from the beginning formulated as a partial differential equation that contains an, for PDEs unusual, eigenvalue decomposition of the unknown field. To this day, most numerical implementations have been based on this or a similar eigenvalue decomposition, with Knechtges et al. (2014) being the only notable exception for two-dimensional
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Steady-state simulation of the film-casting process for Newtonian and viscoelastic fluids J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-10-11 F. Pimenta, M.A. Alves
Thin polymeric films are usually produced in an extensional flow between an extrusion head and a chill roll. The final product is prone to several defects, such as reduced width and non-uniform thickness, and a better understanding of the whole process can improve the final product quality and reduce wastes. This work revisits the film-casting process by exploring the scaling relation between different
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Predicting yielding in the pressure-driven flow of a Bingham fluid in a serpentine channel J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-10-10 T.G. Roberts, S.J. Cox
The use of foams in applications such as enhanced oil recovery and varicose vein sclerotherapy has led to renewed interest in their flow as yield stress fluids. In each application one seeks to determine the ability of a foam to displace another fluid from a tortuous channel. We simulate the pressure-driven flow of a Bingham fluid through a serpentine two-dimensional channel to predict the effects
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Experimental validation of the hierarchical multi-mode molecular stress function model in elongational flow of long-chain branched polymer melts J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-10-04 Manfred H. Wagner, Valerian Hirschberg
The Hierarchical Multi-mode Molecular Stress Function (HMMSF) model predicts the elongational start-up viscosity of long-chain branched (LCB) polymer melts quantitatively up to the point of fracture or up to the steady-state elongational viscosity. It is based on the linear-viscoelastic relaxation modulus and only one nonlinear material parameter in extensional flows, the so-called dilution modulus
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Polymer drag reduction regeneration J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-09-21 Jordan D. Cussuol, Edson J. Soares, Renato N. Siqueira, Kelly C.C.S.R. Moreira, Cleocir J. Dalmaschio
Polymers are largely used as drag reducers in turbulent flows. One of the main problems is the fall in efficiency over time. Such a fall in efficiency is commonly attributed to mechanical degradation. We show here that another mechanism is quite essential: polymer de-aggregation. We present that de-aggregation is not permanent; molecules re-aggregate over time, partially regenerating the drag reduction
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A robust finite difference method for confined and free surface flows with slip at the wall J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-09-23 G.S. Paulo, C. Viezel, L.L. Ferrás
This paper describes the implementation of slip boundary conditions in an in-house finite difference code used to numerically solve the governing equations of complex transient free surface flows. A projection method is used to couple pressure and velocity, and an iterative procedure is used to couple stress to the pressure–velocity variables. The slip boundary conditions are explicitly computed (considering
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Effect of polymer additives on dynamics of water level in an open channel J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-09-22 Manish Kumar, Michael D. Graham
The presence of a tiny amount of polymers (a few parts per million) in a fluid dramatically reduces turbulent drag. For this reason, polymer additives have been proposed to be used in flood remediation: in an open channel at a fixed flow rate, the decrease in friction due to polymer addition is expected to lead to a decrease in water height in the channel. However, in a recent field experiment, a counterintuitive
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Numerical simulations of thixotropic semi-solid aluminium alloys in open-rotor and rotor–stator mixers J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-09-21 Imanol Garcia-Beristain, Michelle Figueroa-Landeta, J. Esteban López-Aguilar, Maider Garcia de Cortazar, Franck Girot, Marco Ellero
This research uses the Bautista–Manero–Puig (BMP) model to examine flow patterns of semi-solid aluminium alloys (Al) in open-rotor and stator–rotor mixers via numerical solutions. The model captures the distinct thixo-viscoelastic behaviour of the Al-alloys at low temperatures, near melting point. The analysis involves using 2D structured-meshes for open-rotor and rotor–stator geometries. Solutions
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Oscillatory boundary layer flow of a Maxwell fluid over a wavy wall J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-09-20 Sergio Cuevas, J. Carlos Domínguez-Lozoya, Leonardo Córdova-Castillo
We analyse the oscillatory flow with a zero-mean of a viscoelastic incompressible fluid over a wavy wall. Using the Maxwell model of viscoelasticity, the problem is transformed into a boundary layer flow by assuming that the amplitude of fluid oscillation as well as the Stokes layer thickness are very small compared with the wavelength of the wall. Analytical solutions are obtained with a perturbation
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The determination of the true equilibrium flow curve for fluid mud in a wide-gap Couette rheometer J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-09-16 D.S.Ch. Praveen, Erik A. Toorman
The rheological properties of fluid mud, a gelling suspension of predominantly colloidal clay particles in water, are usually obtained with a vane spindle for its presumed advantage of avoiding slip with the smooth surface of a standard cylindrical spindle. The vane configuration is presumed to be equivalent to a cylinder configuration by entrapping mud between its blades when it rotates. However,
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Modeling polymeric lubricants with non-linear stress constitutive relations J. Non-Newtonian Fluid Mech. (IF 3.1) Pub Date : 2023-09-16 Humayun Ahmed, Luca Biancofiore
Lubricating oils are used to minimize the friction and wear of mechanical components by virtue of a thin lubricant film separating the sliding surfaces. The film’s characteristics, under high pressure, can exhibit non-Newtonian effects, such as viscoelasticity and shear thinning. The strength of these effects are measured using the Weissenberg (Deborah) number Wi (De), i.e., the ratio of the polymer