Journal of Non-Newtonian Fluid Mechanics最新文献

{"title":"The transport characteristics of a shear-thinning fluid driven by metachronal magnetic artificial cilia","authors":"Tongsheng Wang ,&nbsp;Erik Steur ,&nbsp;Tess Homan ,&nbsp;Patrick R. Onck ,&nbsp;Jaap M.J. den Toonder ,&nbsp;Ye Wang","doi":"10.1016/j.jnnfm.2025.105441","DOIUrl":"10.1016/j.jnnfm.2025.105441","url":null,"abstract":"<div><div>Precise and localized fluid control at small scales is essential for advancing lab-on-a-chip and organ-on-a-chip technologies in fields like biomedicine, drug discovery, and chemical analysis. Traditional pumps are often inadequate for efficient small-volume transport in microfluidic environments, making artificial cilia an appealing solution for integrated, localized fluid management. While magnetically driven cilia offer a biocompatible, non-invasive approach, existing research has primarily focused on Newtonian fluids, leaving the behaviour of shear-thinning fluids largely unexplored. This study investigates the transport characteristics of shear-thinning fluids using a magnetic cilia array under a rotating magnetic field, generating metachronal motion that modulates local viscosity. Results show that the dynamic coupling between cilia beating and the shear‑thinning fluid produces transport behaviour different from that in a Newtonian fluid, particularly at high driving frequencies, offering insights that can inform future design and optimization of magnetic cilia systems for precise fluid control in microfluidic applications, as well as highlighting the importance in studying cilia driven flow in non-Newtonian fluids.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"342 ","pages":"Article 105441"},"PeriodicalIF":2.7,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144170146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transient swimming of an undulating sheet in a second-order fluid","authors":"N. Ali ,&nbsp;A.M. Ardekani","doi":"10.1016/j.jnnfm.2025.105435","DOIUrl":"10.1016/j.jnnfm.2025.105435","url":null,"abstract":"<div><div>The motion of a wavy sheet with time-dependent frequency is discussed in an unbounded non-Newtonian fluid. The rheological behavior of non-Newtonian fluid is captured through the constitutive equation of a second-order fluid. The waves start propagating down the sheet surface with a frequency that achieves a steady-state as an arbitrary function of time. The equation governing the flow is derived under the low Reynolds number approximation. Regular perturbation expansion is employed to develop equations and boundary conditions for stream function at leading and second-order in sheet amplitude. These equations are then solved in Laplace domain to yield expressions of stream functions as arbitrary functions of the frequency of the sheet. Further analysis is carried out for two scenarios. In the first scenario, the sheet is not moving and its undulations produces a net flow. The average velocity of this flow in the horizontal direction is obtained in the Laplace domain. In the second scenario, the sheet is free to move. By employing a force balance at the sheet in the horizontal direction, the swimming velocity of the sheet is also obtained in the Laplace domain. Numerical inversion for some specific choices of sheet frequency is carried out in both scenarios and obtained results are discussed in detail. It is shown that well-behaved pumping and swimming velocities (which are free of jump discontinuity at the initial starting time) for the case in which sheet frequency evolves like a unit-step function are possible in a second-order fluid provided that the amplitudes of longitudinal and transverse waves propagating down the sheet surface satisfy a specific equation.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"342 ","pages":"Article 105435"},"PeriodicalIF":2.7,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144185713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The viscoelastic dynamic model for profile evolution of photoresist formed during thermal reflow","authors":"Xi Lin ,&nbsp;Qi Li ,&nbsp;Yufan Yang ,&nbsp;Yan Xing ,&nbsp;XiaoHui Lin ,&nbsp;Chibin Zhang ,&nbsp;Qing Chai","doi":"10.1016/j.jnnfm.2025.105439","DOIUrl":"10.1016/j.jnnfm.2025.105439","url":null,"abstract":"<div><div>In order to study the profile formation of photoresist microstructure (such as microlens) by the thermal reflow method, the viscoelastic dynamic model is developed based on motion equation, continuity equation, and thin film assumptions. The influence of viscoelastic properties, surface tension, as well as crosslinking effect on polymer melt profile evolution, are considered in this model, and the Oldroyd-B model is used to describe the viscoelastic constitutive relation of polymer melt. Since the viscoelastic dynamic model developed in this paper is a differential equation with regard to the height function of the polymer melt profile, the free surface profile of polymer melts can be obtained naturally during shape evolution by numerically coupling the solution of the film thickness equation and the Oldroyd-B constitutive equation. The computational efficiency of numerical simulation of the free-surface profile would be improved by using this equation as compared to solving the highly non-linear equations of viscoelastic hydrodynamics. The influence of key parameters such as baking time, baking temperature, and crosslinking effect on profile shape evolution is analyzed by this model, and the materials are compared by assigning them different Weissenberg number. In addition, the maximum relative error of verification experiments between the final profile predicted by the simulation and the experimental results is less than 10 %.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"342 ","pages":"Article 105439"},"PeriodicalIF":2.7,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144124837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large amplitude oscillatory extension (LAOE) of dilute polymer solutions","authors":"Steffen M. Recktenwald ,&nbsp;Thomas P. John ,&nbsp;Amy Q. Shen ,&nbsp;Robert J. Poole ,&nbsp;Cláudio P. Fonte ,&nbsp;Simon J. Haward","doi":"10.1016/j.jnnfm.2025.105421","DOIUrl":"10.1016/j.jnnfm.2025.105421","url":null,"abstract":"<div><div>This study presents an experimental framework for large amplitude oscillatory extension (LAOE) to investigate nonlinear material properties of complex fluids. Using a microfluidic optimized shape cross-slot extensional rheometer, we generate approximately homogeneous planar extensional flows driven by programmable syringe pumps operating in oscillatory or pulsatile sinusoidal modes. Micro-particle image velocimetry and simultaneous pressure drop measurements are employed to analyze the time-dependent flow field and elastic stress response. For Newtonian fluids, a linear relationship between the applied strain rate and pressure drop is observed across a wide range of oscillation amplitudes and frequencies. In contrast, dilute polymer solutions exhibit significant deviations, with excess pressure drops and divergence between average strain rates along extension and compression axes during the LAOE cycle. By spanning a broad range of Weissenberg and Deborah numbers, we identify unique Lissajous curves and critical conditions for the onset of nonlinearities under oscillatory extension. Numerical simulations, assuming homogeneous flow, underpin the experimental findings, validating the robustness of our microfluidic approach. This study demonstrates the utility of oscillatory extensional flows for probing the nonlinear rheological behavior of soft materials, offering quantitative insights into their extensional properties under nonlinear flow conditions.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"342 ","pages":"Article 105421"},"PeriodicalIF":2.7,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144114847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extensional properties of dilute polymer solutions with different molecular weights measured using piezo-driven extensional rheometry","authors":"T. Matsuda ,&nbsp;M. Muto ,&nbsp;S. Tamano","doi":"10.1016/j.jnnfm.2025.105422","DOIUrl":"10.1016/j.jnnfm.2025.105422","url":null,"abstract":"<div><div>Filaments ejected from a drop-on-demand (DOD) head filled with a dilute polymer solution (PEO, polyethylene oxide) were photographed and analyzed using a high-speed camera. The filament decay was faster at lower PEO concentrations and became nearly identical at extremely low concentrations. The extensional relaxation time decreased with as the PEO concentration decreased following the power law, and approached an almost constant value near the critical concentration <span><math><msub><mrow><mi>c</mi></mrow><mrow><mi>min</mi></mrow></msub></math></span>, which is close to the theoretical limit. The relationship between the PEO concentration normalized by the overlapping concentration and the relaxation time normalized by the Zimm relaxation time was linear in both logarithmic graphs and independent of molecular weight. The power-law exponent in piezo-driven extensional rheometry is similar to that reported in previous studies, such as those using the liquid dripping (LD) method, capillary breakup extensional rheometry (CaBER), and Rayleigh–Ohnesorge jetting extensional rheometry (ROJER).</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"341 ","pages":"Article 105422"},"PeriodicalIF":2.7,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Equilibrium position and rotational behaviours of spheroid in an inertial rectangular microchannel flow of Oldroyd-B viscoelastic fluid","authors":"Xiao Hu ,&nbsp;Jianzhong Lin ,&nbsp;Zhaosheng Yu ,&nbsp;Zhaowu Lin ,&nbsp;Jingyu Cui ,&nbsp;Yan Xia","doi":"10.1016/j.jnnfm.2025.105431","DOIUrl":"10.1016/j.jnnfm.2025.105431","url":null,"abstract":"<div><div>Equilibrium position and rotational behaviours of spheroid in an inertial rectangular microchannel flow of Oldroyd-B viscoelastic fluid is studied by the direct forcing/fictitious domain method. The results show that there are five kinds of equilibrium positions and four (three) kinds of rotational behaviours for the elasto-inertial migration of prolate (oblate) spheroids in an inertial rectangular channel flow. The spheroids gradually change to the corner (CO), channel centreline (CC), near corner (NCO), near channel centre (NCC) and bisector of the long wall (BLW) equilibrium positions as the elastic number decreases, the NCO and NCC equilibrium positions are newly found in the present works. When the fluid elasticity is large, only the large sphere displays the anomalous off-centreline NCC equilibrium position. With increasing the fluid inertia, the induced lateral migration velocity near the particle is enhanced, and the induced streamlines push all particles away from the CC equilibrium position. Spherical particles exhibit the highest induced velocity, then followed by the oblate spheroids, while prolate spheroids induce the lowest lateral migration velocity and consistently exhibit the closest distance to the channel centre. The particles are closer to the channel centre with decreasing the particle size, and with increasing the fluid elasticity. Those results are useful for designing a microfluidic chip with high separation efficiency.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"341 ","pages":"Article 105431"},"PeriodicalIF":2.7,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143923750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental investigation on drag reduction in turbulent pipe flow with polymer injection","authors":"Pengfei Shi ,&nbsp;Haibao Hu ,&nbsp;Jun Wen ,&nbsp;Hailang Sun ,&nbsp;Luo Xie","doi":"10.1016/j.jnnfm.2025.105434","DOIUrl":"10.1016/j.jnnfm.2025.105434","url":null,"abstract":"<div><div>An experimental investigation is conducted to characterize the drag reduction of Polyethylene Oxide solutions and its influencing on turbulent pipe flow with polymer injection. The study systematically examines the effects of Reynolds number, injection angle (seven angles), molecular weight (seven molecular weights), and streamwise direction development on drag reduction. Similar to the dimensionless polymer flux <em>K</em> in the flat plate boundary layer flow with polymer injection, the normalized polymer flux <em>K</em>_<em>p</em> applicable to the pipe (i.e., the relative mass ratio between the injecting polymer and the main flow) is defined to further collapse experimental data. The <em>K</em>_<em>p</em>-scaling laws indicate that DR firstly grows linearly, and then saturates or even declines with increasing log₁₀ <em>K</em>_<em>p</em>, similar to the observed DR variation of the plate boundary layer flow with polymer injection. The DR vs <em>K</em>_<em>p</em> relationship could provide guidance to optimize the use of polymer injection for the pipeline flow. Notably, the variation law of drag reduction with molecular weight conforms to S-shaped curve, which can provide guidance to optimize the use of molecular weight in polymers drag reduction. The change in drag reduction with Reynolds number varying from 15,952 to 79,761 initially increases and then decreases; there exists a critical Reynolds number for achieving optimal drag reduction effect. The variation of drag reduction rate with injection angle and streamwise direction distance is influenced by both effective concentration and advection of the injected solution. Smaller injection angle does not bring more significant drag reduction effect. Meanwhile, the counter-stream injection exhibits a superior drag reduction effect compared to streamwise injection under certain conditions, primarily due to the influence of more suitable mixing rate.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"341 ","pages":"Article 105434"},"PeriodicalIF":2.7,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144072381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Control of viscoplastic fluid dynamics in superhydrophobic channels with asymmetric groove configurations","authors":"A. Joulaei ,&nbsp;H. Rahmani ,&nbsp;S.M. Taghavi","doi":"10.1016/j.jnnfm.2025.105420","DOIUrl":"10.1016/j.jnnfm.2025.105420","url":null,"abstract":"<div><div>We study the plane Poiseuille flow of viscoplastic fluids in channels with asymmetric superhydrophobic (SH) walls featuring transverse groove configurations in the thin channel limit. We use OpenFOAM simulations and the Papanastasiou regularization method to approximate the Bingham model. Focusing on variations in the upper SH wall’s characteristics, we explore the effects of slip number (<span><math><msub><mrow><mi>b</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>), groove periodicity length (<span><math><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>), slip area fraction (<span><math><msub><mrow><mi>φ</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>), and Bingham number (<span><math><mi>B</mi></math></span>) on flow dynamics, flow metrics and unyielded center plug morphology. We find that increasing <span><math><msub><mrow><mi>b</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, <span><math><msub><mrow><mi>φ</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, and <span><math><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> enhances slip velocity on the upper SH wall and reduces the normalized plug area (<span><math><mrow><mi>A</mi><mo>/</mo><msub><mrow><mi>A</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></math></span>) up to <span><math><mrow><msub><mrow><mi>φ</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>=</mo><mn>0</mn><mo>.</mo><mn>5</mn></mrow></math></span>, while higher <span><math><mi>B</mi></math></span> amplifies flow asymmetry, shifting and breaking center plugs. By introducing the concept of <em>slippery equivalent systems</em>, we demonstrate that varying groove configurations can yield identical effective slip lengths (<span><math><msub><mrow><mi>χ</mi></mrow><mrow><mi>T</mi></mrow></msub></math></span>) with distinct plug morphologies, enabling precise control of viscoplastic fluid dynamics. We derive a simplified model to predict <span><math><msub><mrow><mi>χ</mi></mrow><mrow><mi>T</mi></mrow></msub></math></span> and <span><math><mrow><mi>A</mi><mo>/</mo><msub><mrow><mi>A</mi></mrow><mrow><mn>0</mn></mrow></msub></mrow></math></span>, identifying a critical threshold at <span><math><mrow><mi>A</mi><mo>/</mo><msub><mrow><mi>A</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>≈</mo><mn>0</mn><mo>.</mo><mn>68</mn></mrow></math></span> for regime transitions between unbroken (Regime I) and broken (Regime II) center plugs, leading to a six-dimensional manifold equation for classifying these regimes across parameter space.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"341 ","pages":"Article 105420"},"PeriodicalIF":2.7,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143869095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelling of the pressure-driven tube flow of the shear-thinning fluids with solid particles","authors":"A.A. Gavrilov ,&nbsp;A.V. Shebelev ,&nbsp;A.V. Minakov","doi":"10.1016/j.jnnfm.2025.105430","DOIUrl":"10.1016/j.jnnfm.2025.105430","url":null,"abstract":"<div><div>A continuum model of shear-thinning fluid suspension flow based on suspension balance model is developed. The generalization of the suspension model to the shear-thinning yield stress fluids, obeying the Herschel-Bulkley law, requires taking into account the shear rate amplification effect and modification of the particle drag force. Additionally, the model includes inertial and unsteady particle effects by using the transport equation for relative velocity. To validate the proposed model, pressure-driven laminar flows of suspensions with neutrally buoyant and heavy particles in circular pipes are numerically simulated. The results show that, at certain conditions, the developed model can adequately describe various flow regimes of shear-thinning yield stress fluids with solid particles, from heterogeneous flows with a stationary sediment layer to flows with suspended particles. An important issue for suspension flows with heavy particles is considered - assessment of the particle transport efficiency. Dependencies of some integral characteristics of the flow are considered.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"341 ","pages":"Article 105430"},"PeriodicalIF":2.7,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bingham flow development in annular tubes in the presence of wall slip","authors":"Evgenios Gryparis ,&nbsp;Alexandros Syrakos ,&nbsp;Georgios C. Georgiou","doi":"10.1016/j.jnnfm.2025.105418","DOIUrl":"10.1016/j.jnnfm.2025.105418","url":null,"abstract":"<div><div>The development of Bingham flow in concentric annular tubes in the presence of wall slip is investigated. It is assumed that slip occurs along both cylinders, following Navier's law, which states that the slip velocity is proportional to the wall shear stress. The open-source finite element software FEniCS is used for the numerical simulations along with the Papanastasiou regularization for the constitutive equation. To correctly determine the entrance region, various definitions of the development length are considered. In addition to the standard definition, which is based on the maximum velocity development, and the global development length, alternative definitions based on the development of the wall shear stresses and of the velocity at the two yield radii are considered. The combined effects of slip, yield stress and inertia on the different development lengths are systematically investigated. The yielded and unyielded zones are also determined using the von Mises criterion. The numerical results show that the standard development length fails to accurately capture the entrance region, even in the case of Newtonian flow with no-slip, and that the inner wall shear stress and yield lengths are also inadequate. The global and the outer wall shear stress and yield development lengths, which can be up to four times bigger than the standard development length, are more reliable. In agreement with previous studies, the development lengths are monotonically increasing with the Reynolds and Bingham numbers. As wall slip becomes stronger these reliable development lengths increase only initially reaching a maximum and then they are abruptly reduced to zero as the slip number approaches the critical value corresponding to sliding (unyielded) motion.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"339 ","pages":"Article 105418"},"PeriodicalIF":2.7,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143760470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}