Journal of Non-Newtonian Fluid Mechanics最新文献

{"title":"Thermo-hydraulic perspectives of non-Newtonian channel flow with active flow modulation: A CFD study","authors":"Fahim Tanfeez Mahmood ,&nbsp;Arpita Das ,&nbsp;Taspia Shawkat Chowdhury ,&nbsp;Mohammad Nasim Hasan","doi":"10.1016/j.jnnfm.2025.105416","DOIUrl":"10.1016/j.jnnfm.2025.105416","url":null,"abstract":"<div><div>This study aims to numerically explore the influence of active flow modulators on thermo-hydraulic characteristics of channel flow with non-Newtonian power-law fluid, also known as Generalized Newtonian Fluid (GNF). The upper and lower walls of the channel under consideration are heated isothermally, while at the inlet a channel flow with Poiseuille fluid flow profile is imposed, influenced by an active flow modulator, namely an oscillating blade positioned along the channel centreline. Within the Arbitrary Lagrangian-Eulerian framework, the associated flow and thermal fields are solved using the Galerkin finite element method. The channel's hydrodynamic state is assessed in relation to the Reynolds number variation (50 ≤ <em>Re</em> ≤ 150), for various non-Newtonian fluids as represented by the power-law index variation (0.6 ≤ <em>n</em> ≤ 1.2). Furthermore, the corresponding dimensionless oscillating frequency (<em>N*</em>) and channel blockage ratio (<em>B</em>) are changed in order to investigate the impact of the flow modulator. The evolution of temperature and flow fields as well as heat transfer performance metrics, such as local, spatially and time averaged Nusselt numbers, have all been taken into consideration while evaluating the characteristics of the system. The obtained results indicate that the Reynolds number and associated flow obstruction have a significant impact on the flow modulator's efficacy. For pseudoplastic fluids (<em>n</em> = 0.6), thermal oscillations can be observed, which are brought on by the oscillating modulator's periodic shedding of vortices. While pseudoplastic fluid might improve heat transfer, especially at greater blockage ratios, the situation is reversed when the associated pressure drop is taken into account.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"339 ","pages":"Article 105416"},"PeriodicalIF":2.7,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143799596","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":"Viscoelasticity-contrast driven electrohydrodynamic behaviour of a droplet-suspended-in-a-confined-liquid configuration","authors":"Pulak Gupta ,&nbsp;Purbarun Dhar ,&nbsp;Devranjan Samanta","doi":"10.1016/j.jnnfm.2025.105406","DOIUrl":"10.1016/j.jnnfm.2025.105406","url":null,"abstract":"<div><div>We present an approximate analytical model (without compromise on the physics) of the electrohydrodynamics (EHD) of a confined leaky dielectric, non-Newtonian viscoelastic droplet suspended in a surrounding medium of similar characteristics. The analysis considers the Stokes flow regime through a small deformation formulation. The viscoelastic behaviour is realized by coupling the Cauchy momentum equation with the upper convected Maxwell (UCM) model. Since the study is limited to low electric field intensities, the governing Weissenberg number (Wi) <span><math><mo>≤</mo></math></span> 1. We consider various combinations of the droplet and the surrounding, viz. NN-N, N-NN, and NN-NN cases. A thorough comparison with the N-N case is conducted. Here, ‘N’ represents Newtonian and ‘NN’ represents non-Newtonian. The solution put forward is validated with experimental observations in literature and works successfully in the regime of low electric field strength. We show that, for an unconfined domain, the deformation is maximum for the N-N case and least for the N-NN case, thus establishing the role of viscoelasticity-contrast. For the confined domain, we have also observed shape reversal in N-NN and NN-NN cases at higher confinement (<span><math><mi>α</mi></math></span>) and lower electro-rheological parameter (<span><math><mi>δ</mi></math></span>). For NN-N, the deformation is greater compared to the N-N case beyond a critical <span><math><mi>α</mi></math></span>. We also report the streamline patterns within the droplet and in the surrounding medium for various cases and for different confinement. The findings reveal shape reversal phenomena in confined viscoelastic cases, and provide insights into the EHD with fluidic confinement, offering potential avenues for the design and functionality of microfluidic devices.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"338 ","pages":"Article 105406"},"PeriodicalIF":2.7,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143680337","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":"Features and limitations of recent elastoviscoplastic constitutive models under Large Amplitude Oscillatory Shear (LAOS)","authors":"Rishav Agrawal ,&nbsp;Esther García-Tuñón ,&nbsp;Robert J. Poole ,&nbsp;Cláudio P. Fonte","doi":"10.1016/j.jnnfm.2025.105407","DOIUrl":"10.1016/j.jnnfm.2025.105407","url":null,"abstract":"<div><div>Elastoviscoplastic (EVP) models are becoming more widely adopted to investigate the deformation and flow of yield stress materials for various applications. In this work, we investigate EVP models, primarily the Saramito model but also the recently developed Kamani–Donley–Rogers (KDR) model, under Large Amplitude Oscillatory Shear (LAOS) tests using Fourier Transform (FT) rheology, dissipation ratio (<span><math><mi>ϕ</mi></math></span>) analysis and the Sequence of Physical Processes (SPP) framework. A detailed parametric study has been conducted for the Saramito model for a wide range of values of the relevant non-dimensional parameters – Bingham, Weissenberg and Deborah numbers. We also compare the Saramito and KDR models for a particular set of conditions and compare them with experimental data for Pluronic F127 hydrogel, a yield stress fluid commonly used in 3D printing. The parametric study of the Saramito model reveals a universal scaling for the onset of purely elastic behaviour, which shows dependence on <em>both</em> Bingham and Weissenberg numbers. Moreover, we demonstrate that although both EVP models can predict the ‘yielding’ process, the KDR model provides a better agreement with rheological data for Pluronic F127. The KDR also performs better in predicting associated EVP behaviour compared to the Saramito model, e.g. gradual change in the storage and loss moduli and the <span><math><mi>ϕ</mi></math></span> values near the onset of yielding. However, neither model could fully capture higher harmonics, shapes of the Lissajous-Bowditch curves and the intra-cycle rheological transitions when compared to experimental data. In addition to the LAOS measurements, further tests under different flow conditions of the recently-developed KDR model against experimental data for yield stress fluids are required to assess its capabilities in capturing the full spectrum of EVP behaviours.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"338 ","pages":"Article 105407"},"PeriodicalIF":2.7,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143680338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atomizing high-viscosity non-Newtonian fluids with the ACLR nozzle: Correlation between internal flow and external spray instabilities","authors":"Miguel Ángel Ballesteros Martínez,&nbsp;Prithika Roy,&nbsp;Juan Nicolás Solano Alarcón,&nbsp;Volker Gaukel","doi":"10.1016/j.jnnfm.2025.105405","DOIUrl":"10.1016/j.jnnfm.2025.105405","url":null,"abstract":"<div><div>Spray drying is a widely used method for producing food powders in large quantities, but it also has a high energy demand. To address this, one can increase the solid content of liquid feeds, although this, in turn, poses the challenge of atomizing high-viscosity liquids into fine droplets. The Air-Core-Liquid-Ring (ACLR) nozzle offers a potential solution for the atomization by inducing air and creating an annular flow inside the nozzle. Nevertheless, a challenge of this design is that it tends to present internal instabilities. This study investigates how feed viscosities up to 3 Pa·s, and feed dry-matter contents up to 57 % wt., influence the internal flow conditions and the resulting spray performance, i.e., the droplet size distribution and the spray angle. The results show that, while internal instabilities increment with increasing viscosities, the ACLR can seemingly achieve atomization with viscosities as high as 3 Pa·s, even at, compared to pressure swirl nozzles, low pressures (7 bar) and low air-to-liquid mass ratios (0.8). Nonetheless, a fraction of droplets over 500 µm remains, which needs to be addressed through higher ALRs or a geometrical optimization of the nozzle, before the nozzle can be considered for industrial applications. Additionally, we showed that the internal flow and the external spray instabilities can be correlated with each other. This confirms that any future studies attempting to increase the spray stability of the ACLR nozzle can focus on only one of these factors, and reasonably expect that the others will also improve.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"338 ","pages":"Article 105405"},"PeriodicalIF":2.7,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143580629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inertio-elastic parametric resonance between inertia-dominated and elasticity-dominated Taylor vortex flows in Boger fluids confined between two co-oscillating cylinders","authors":"Mohamed Hayani Choujaa ,&nbsp;Mehdi Riahi ,&nbsp;Saïd Aniss","doi":"10.1016/j.jnnfm.2025.105398","DOIUrl":"10.1016/j.jnnfm.2025.105398","url":null,"abstract":"<div><div>A Floquet analysis describing the influence of inertia and elasticity on the dynamics of the viscoelastic flow of a model Boger fluid between two co-oscillating cylinders is presented. This model is approximated by the Oldroyd-B constitutive equation which describes the rheological behavior of highly elastic polymer melts diluted with a Newtonian solvant. A linear stability analysis is developed to predict the effect of both the polymer/solvant viscosity ratio and the polymer elasticity on the critical vortex flow conditions at the onset of instability. Special attention is devoted to emphasize the flow reversal of the system, which is used as an indicator to distinguish between inertia-dominated and elasticity-dominated instability modes. It is shown that the occurrence of purely inertial reversing and non-reversing flows, setting in the Newtonian case, moves towards the high frequency limit only when dealing with weakly elastic and highly diluted viscoelastic solutions. These instability modes are considered inertia-dominated and are completely suppressed by moderate values of elasticity. However, the low and moderate frequency limits are characterized by the appearance of new elasticity-dominated instability modes that persist over the entire frequency range when highly elastic solutions are considered. In addition, it turns out that with slowly oscillating cylinders a purely elastic destabilizing mechanism is noticed and becomes inertio-elastic by increasing the oscillation frequency. These results provide comprehensive insights into the dynamics of oscillatory flows in pure and dilute polymeric substances.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"338 ","pages":"Article 105398"},"PeriodicalIF":2.7,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143619425","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":"Influence of viscoelastic properties on induced charge electro-osmosis of Phan–Thien–Tanner fluids around a metal cylinder","authors":"Jun Xu ,&nbsp;Weicheng Yu ,&nbsp;Chi Li ,&nbsp;Likai Hou ,&nbsp;Fubing Bao ,&nbsp;Jie Li","doi":"10.1016/j.jnnfm.2025.105397","DOIUrl":"10.1016/j.jnnfm.2025.105397","url":null,"abstract":"<div><div>Efficient mixing of chemicals is a key issue in microfluidics because of the limitations of low diffusivity in laminar flow. Induced charge electro-osmosis (ICEO), which generates quadrupole vortices, has been shown to be a simple and effective method for rapid mixing. The aim of this work is to improve the mixing of viscoelastic fluids using ICEO, thus extending the application of microfluidics in biomedical and chemical analysis. A simplified Phan–Thien–Tanner (sPTT) constitutive model was used to characterize the flow properties of the viscoelastic fluid, and the Navier-Stokes (NS) and Poisson-Nernst-Planck (PNP) equations were used to control the potential and ion concentration distributions, respectively. Numerical simulations of ICEO around a polarized cylinder in a two-dimensional cavity filled with an electrolyte solution have been carried out using the finite volume method. The effects of Weissenberg number (<em>Wi</em>), viscosity ratio (<em>β</em>), and extensibility parameter (<em>ε</em>) on the velocity and flow field were investigated. The results show that the larger <em>ε</em> and <em>Wi</em> are, the larger the maximum velocity is, and the peak velocity increases with increasing <em>ε</em> and <em>Wi</em>. When <em>ε</em> increases from 0.01 to 0.8, the peak velocity increases from 23.22 × 10⁻⁴ to 31.73 × 10⁻⁴. The maximum velocity at <em>Wi</em> = 10 is about twice that at <em>Wi</em> = 0.01.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"337 ","pages":"Article 105397"},"PeriodicalIF":2.7,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143473956","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":"Recovery dynamics and polymer scission in capillary breakup extensional rheometry","authors":"Joe B. Joseph,&nbsp;Jonathan P. Rothstein","doi":"10.1016/j.jnnfm.2025.105396","DOIUrl":"10.1016/j.jnnfm.2025.105396","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Capillary breakup extensional rheometry (CaBER) is a technique widely used to quantitatively measure the transient extensional rheology of a visco-elastic fluid. In this paper, we investigate some of the shortcomings of measuring the transient relaxation time through CaBER and Dripping onto Substrate (DoS)-CaBER experimentation and describe problematic conditions for which consistency of results is not achieved. Using a high molecular weight polyacrylamide polymer &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mi&gt;W&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;18&lt;/mn&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;/mrow&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/msup&gt;&lt;mrow&gt;&lt;mi&gt;g&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mtext&gt;mol&lt;/mtext&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; in a viscous water and glycerol solution, we investigated the effect that the choice of syringe size, tubing size, tubing length and flow rate used to generate the liquid bridge in DoS-CaBER can have on the decay evolution of the fluid filament. The resulting measurements showed a sharp decrease in extensional viscosity and relaxation time with increasing strength of the shear and extensional flows within the syringe and tubing used to generate the pendant drop. These measurements highlighted the importance of considering the flow and deformation history of the polymer prior to the DoS-CaBER and CaBER stretches. In order to understand whether these observed effects were due to recoverable pre-deformation of the polymer or permanent scission of the polymer, the DoS-CaBER syringe setup was used to deposit the polymer solution into a CaBER under different loading conditions. CaBER tests were then performed with various delay times to erase the deformation history of loading. For these samples, rest times of more than 100 extensional relaxation times were required to erase the deformation history caused by the loading of the sample. Even with the pre-conditioning erased, however, unrecoverable losses in relaxation time and extensional viscosity remained. These observations indicate that polymer scission occurred in all samples where loading resulted in an extensional Weissenberg number greater than &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;W&lt;/mi&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;8&lt;/mn&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. Next, the effect of successive CaBER stretches on a single sample and the time delay imposed between successive stretches on the fluid rheology was studied. Stretches performed immediately one after the other with no recovery time built in showed a steep decline in measured relaxation time and breakup time. However, even with post stretch delays of twenty minutes, full recovery of the initial fluid properties was not achieved suggesting that extensional flow induced scission of the polymer had occurred even in CaBER. Thus, it is clear that the effect of preconditioning a viscoelastic fluid is strong, and these factors need to be considered prior to conducting CaBER and DoS-CaBER experiments in the future.&lt;","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"337 ","pages":"Article 105396"},"PeriodicalIF":2.7,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143427714","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":"Potential applications of elastic instability and elastic turbulence: A comprehensive review, limitations, and future directions","authors":"C. Sasmal","doi":"10.1016/j.jnnfm.2025.105393","DOIUrl":"10.1016/j.jnnfm.2025.105393","url":null,"abstract":"<div><div>Viscoelastic fluids, a subclass of complex fluids, are employed across various applications, from biological processes to large-scale industrial operations. These fluids exhibit complex flow behaviors resulting from non-linear elastic stresses that arise from the stretching and relaxation of their microstructures, such as polymer molecules in viscoelastic polymer solutions, within a deformed flow field. One notable phenomenon associated with these fluids is purely “elastic instability” (EI), which occurs when elastic stresses interact with the streamline curvature in a flow system at low Reynolds numbers (the ratio of inertial to viscous forces). Specifically, EI manifests when the Weissenberg number (the ratio of the microstructure relaxation time to the rate of flow deformation) surpasses a critical threshold. As the Weissenberg number continues to increase, the unstable flow field resulting from EI further transits to a more chaotic and turbulent-like flow state known as “elastic turbulence” (ET). The fluctuating hydrodynamics characteristics of ET display statistical similarities to conventional Newtonian turbulence observed at high Reynolds numbers. Over the past two decades or so, extensive research has been conducted within the complex fluids research community to explore these two phenomena, resulting in several comprehensive articles that outline the development and understanding of ET. This article focuses on the potential application perspectives of these two phenomena. In particular, this article aims to provide a thorough review of the applications of EI and ET phenomena, particularly in three main areas: microfluidic mixing, microscale heat transfer, and chemically enhanced oil recovery (EOR) processes. Furthermore, this review will also provide a discussion on the limitations and future research directions associated with these two phenomena, highlighting their potential from an application standpoint.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"337 ","pages":"Article 105393"},"PeriodicalIF":2.7,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143419591","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":"Extrudate swell and defects under the effect of radial flow and die geometry","authors":"Hala Krir,&nbsp;Abdelhak Ayadi","doi":"10.1016/j.jnnfm.2024.105381","DOIUrl":"10.1016/j.jnnfm.2024.105381","url":null,"abstract":"<div><div>The present paper aims to investigate the phenomenon of extrudate swells of polydimethylsiloxane (PDMS) during extrusion. This study contributes to understanding how radial flow, and in particular gap width, influences the initiation and growth of linear PDMS extruded swelling. To accomplish this, we consider implementing a capillary rheometer that imposes a radial flow upstream of the extrusion die. Images from the experiment demonstrate that the die swell seems more pronounced for both long and short dies with a high radial flow gap than it does for small gaps. In addition, we notice that, for a given gap, an increase in the length-to-diameter ratio reduces the extrudate swell. The findings explore the interplay between the elasticity of PDMS, the energy stored during the flow, and the memory effect on the final diameter of the extruded material.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"336 ","pages":"Article 105381"},"PeriodicalIF":2.7,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153122","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":"Numerical simulation of Poiseuille flow for S-shaped rheology fluid: Streamwise banding and viscous sandglasses","authors":"L. Talon,&nbsp;D. Salin","doi":"10.1016/j.jnnfm.2024.105379","DOIUrl":"10.1016/j.jnnfm.2024.105379","url":null,"abstract":"<div><div>Recent experiments on pressure-driven Poiseuille flow of cornstarch in a cylindrical tube (Talon and Salin, 2024) show a surprising behavior. The measured flow curve, i.e. the flow rate versus the applied pressure drop, is indeed non-monotonic: the flow rate increases monotonically at low pressure drops up to a maximum, after which it decreases abruptly to an almost constant flow rate regardless of further increases in pressure drop. Cornstarch is known to exhibit discontinuous shear thickening (DST) behavior (Fall et al., 2012). In addition, recent experiments (Denn et al., 2018; Darbois Texier et al., 2020; Bougouin et al., 2024) suggest that the rheology may ultimately be S-shaped, where the shear rate is a nonmonotonic function of stress, similar to the model proposed by Wyart and Cates (Wyart and Cates, 2014). To account for the observed jump-plateau behavior of the flow rate, one possibility is that Poiseuille flow for S-shaped rheology exhibits some kind of phase segregation, where the pressure gradient becomes non-uniform. The pressure gradient segregate between two types of region, with either high pressure gradient or low one. This kind of “streamwise banding” were analyzed in Talon and Salin (2024) using the lubrication approximation and assuming simple dynamical stochastic version of the nonmonotonic S-shaped rheology Wyart–Cates model. The plateau behavior is then related to an increase of the high viscous region as the pressure is increased. The mere presence of a non-monotonic rheological curve could then be sufficient to predict the occurrence of banding in the streamwise direction, even if the suspension remains homogeneous.</div><div>In this paper, we aim to analyze this prediction by disregarding the lubrication approximation and directly solving the flow of a shear thickening fluid with S-shaped rheology. Using 2D TRT Lattice Boltzmann simulations, we observe that the plateau in flow rate is indeed associated with a streamwise segregation of the pressure gradient. In addition, we show that regions of high pressure gradients are due to the formation of a highly viscous structure similar to a “sandglass” shape. We then analyze the occurrence of these sandglass structures as a function of the system parameters.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"336 ","pages":"Article 105379"},"PeriodicalIF":2.7,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143154453","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}