Journal of Non-Newtonian Fluid Mechanics最新文献

{"title":"Effect of flow-inducing devices on the generation of viscoelastic fluid droplets","authors":"Runze Duan ,&nbsp;Qiannan Huang ,&nbsp;Chenyang Wei ,&nbsp;Liansheng Liu ,&nbsp;Yuanhe Yue ,&nbsp;Qingfei Fu","doi":"10.1016/j.jnnfm.2026.105571","DOIUrl":"10.1016/j.jnnfm.2026.105571","url":null,"abstract":"<div><div>Droplet generation is a fundamental fluid dynamic process critical to numerous applications in biomedicine, inkjet printing, food processing, and microfluidic systems. Achieving precious control over this process is important for improving the performance and efficiency of such systems. Compared to Newtonian fluids, viscoelastic fluids exhibit complex rheological behaviors arising from polymer chain entanglement and relaxation effects, which profoundly alter the droplet generation and breakup dynamics. In this study, we introduce a passive control strategy by incorporating a drainage device inside the nozzle to construct a drainage-assisted dripping system. The results show that, within the investigated polymer system, increasing molecular weight is associated with longer filament lengths, larger primary droplet volumes, and extended droplet generation periods. The introduction of the drainage device effectively mitigates these elastic effects by modifying the flow redistribution and upstream boundary conditions prior to breakup, rather than through direct control of elongational stresses. As a result, the filament breakup length is reduced and the generation of satellite droplets is suppressed under the present experimental conditions. Furthermore, the dimensionless length (<em>L</em>_s/<em>L</em>₀) and diameter (<em>D</em>_s/<em>D</em>₀) of the drainage device are key governing parameters within the investigated parameter range. An increase in <em>L</em>_s/<em>L</em>₀ leads to a reduction in the primary droplet volume, filament breakup length, and droplet generation period. In contrast, an increase in <em>D</em>_s/<em>D</em>₀ yields a slight decrease in droplet volume and filament length but prolongs the generation period. Notably, polymer solutions with higher elasticity exhibit stronger sensitivity to the geometric parameters of the drainage device under the present conditions. These findings demonstrate that by optimizing the drainage device geometry, elastic control over droplet size and generation frequency can be achieved without altering the fluid viscosity within the investigated system. This work provides new insights into the passive regulation of viscoelastic droplet generation and may offer useful guidance for the design and optimization of microfluidic, inkjet printing, and multiphase flow systems.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"348 ","pages":"Article 105571"},"PeriodicalIF":2.8,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147395609","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":"Swimming dynamics of microorganisms near a wall in viscoelastic fluids","authors":"Runyang Qiu,&nbsp;Fangyuan Peng,&nbsp;Minkang Zhang,&nbsp;Dingyi Pan,&nbsp;Zhaosheng Yu,&nbsp;Zhaowu Lin","doi":"10.1016/j.jnnfm.2026.105565","DOIUrl":"10.1016/j.jnnfm.2026.105565","url":null,"abstract":"<div><div>Microorganisms in natural environments often navigate through non-Newtonian fluids under confinement that critically influences their locomotion dynamics. A direct-forcing fictitious domain method, coupled with the squirmer model, is employed to systematically investigate the swimming behaviors of microswimmers near a wall in Giesekus viscoelastic fluids. Four distinct behavioral modes are identified: <em>scattering</em>, <em>oscillating</em>, <em>crawling</em>, and <em>hovering</em>. Near planar walls, squirmers with strong stresslets demonstrate wall-trapped tendencies, with pullers predominantly exhibiting <em>crawling</em> behaviors while pushers display sustained oscillatory motions. Notably, the polymeric viscoelastic stress generates a torque opposite to that in the Newtonian case, which hinders the microswimmer’s escape from the wall. Furthermore, concave wall geometries substantially modify these behaviors through curvature-dependent hydrodynamic interactions, revealing a critical relationship between behavioral modes and geometric topology.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"348 ","pages":"Article 105565"},"PeriodicalIF":2.8,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147395718","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":"U = 0?","authors":"Ian Frigaard","doi":"10.1016/j.jnnfm.2025.105530","DOIUrl":"10.1016/j.jnnfm.2025.105530","url":null,"abstract":"<div><div>Yield stress fluids have the ability to withstand a shear stress while at rest, i.e. below the yield stress. Consequently, the zero solution has a wider range of application than in Newtonian hydrostatics. Alternatively, one could say that with yield stress fluids a new branch of hydrostatics is possible. This paper shows how in general zero flows are intuitively described using the <em>yield</em> number. It gives the general definition of a critical yield number, above which flows are static. The critical yield number also frequently defines a parametric domain in which the flow is nonlinearly stable, as is demonstrated. The mathematical concepts are introduced from the perspective of a reader who wishes to use a new toolbox and the main ideas are illustrated with a wide range of application flows and examples.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"347 ","pages":"Article 105530"},"PeriodicalIF":2.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145693987","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":"Vortex dynamics in converging-diverging pipes for weakly and moderately elastic polymer solutions","authors":"Aidar I. Kadyirov","doi":"10.1016/j.jnnfm.2025.105529","DOIUrl":"10.1016/j.jnnfm.2025.105529","url":null,"abstract":"<div><div>The importance of extensional rheology to the flow structure in single and double converging-diverging (Cnv-Dvr) pipes has been observed experimentally. The aqueous solutions of 0.1 % polyacrylamide and 0.155 % Xanthan gum with the same shear viscosity but different extensional behavior were chosen as moderately and weakly elastic polymer solutions. For single Cnv-Dvr pipes with conical restriction rate of 2:1:2 it was observed that in a wide range of Weissenberg, Deborah and Reynolds numbers a vortex is generated in converging or diverging sections only, which depends on the type of a polymer solution. Similar tendency was found for double Cnv-Dvr pipes, except that both fluids generate a smaller vortex in the middle section (diverging-converging section). For all runs related to the polymer solution flows and conducted in the present study, the elastic forces predominate over inertial ones. The vortex formation for moderately elastic polymer solutions observed in double Cnv-Dvr pipes like in a single one leads to the axial velocity oscillations with an increase in amplitude with the flow rate up until the critical value. The emerging smaller vortex in the middle section does not change this behavior and oscillates with the same frequency. The location of vortex formation for weakly elastic polymer solution in both pipes is similar to Newtonian fluid.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"347 ","pages":"Article 105529"},"PeriodicalIF":2.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145529009","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":"Modeling Rayleigh–Taylor instability in viscoelastic liquid film flow","authors":"Minzun He,&nbsp;Weiyang Jiang,&nbsp;Zijing Ding","doi":"10.1016/j.jnnfm.2025.105531","DOIUrl":"10.1016/j.jnnfm.2025.105531","url":null,"abstract":"<div><div>This study presents a first-order weighted-residual model for viscoelastic thin-film flow on inverted substrates, incorporating van der Waals interactions. The model is derived via systematic scaling analysis, boundary-layer approximations, and a Galerkin weighted-residual method based on the Oldroyd-B constitutive framework. It achieves a balance between computational efficiency and accurate representation of viscoelastic effects. A notable feature is the ability to independently adjust the Deborah number (<span><math><mrow><mi>D</mi><mi>e</mi></mrow></math></span>) and the retardation ratio (<span><math><mi>r</mi></math></span>), addressing the limitation of Benney-type models that depend only on the combined parameter <span><math><mrow><mi>M</mi><mo>=</mo><mrow><mo>(</mo><mn>1</mn><mo>−</mo><mi>r</mi><mo>)</mo></mrow><mi>D</mi><mi>e</mi></mrow></math></span>. The model remains accurate for large <span><math><mrow><mi>D</mi><mi>e</mi></mrow></math></span>. Analysis of the principal dimensionless parameters (<span><math><mrow><mi>D</mi><mi>e</mi></mrow></math></span>, <span><math><mi>S</mi></math></span>, <span><math><mi>r</mi></math></span>, <span><math><mi>A</mi></math></span>, <span><math><mrow><mi>G</mi><mi>a</mi></mrow></math></span>) clarifies the stability behavior: increasing <span><math><mrow><mi>D</mi><mi>e</mi></mrow></math></span> enhances elastic instability, whereas a larger <span><math><mi>r</mi></math></span> weakens viscoelastic effects. The cutoff wavenumber <span><math><msub><mrow><mi>k</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span> depends on gravity (<span><math><mrow><mi>G</mi><mi>a</mi></mrow></math></span>), surface tension (<span><math><mi>S</mi></math></span>), and van der Waals forces (<span><math><mi>A</mi></math></span>), but not on <span><math><mrow><mi>D</mi><mi>e</mi></mrow></math></span> or <span><math><mi>r</mi></math></span>. Validation against linearized Navier–Stokes (LNS) solutions and direct numerical simulations (DNS) shows closer agreement than the Benney-type model, particularly at high <span><math><mrow><mi>D</mi><mi>e</mi></mrow></math></span>. The model also reproduces ultrathin-film rupture via cusp formation induced by van der Waals forces and predicts the scaling law <span><math><mrow><msub><mrow><mi>h</mi></mrow><mrow><mo>min</mo></mrow></msub><mo>∝</mo><msup><mrow><mrow><mo>(</mo><msub><mrow><mi>t</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>−</mo><mi>t</mi><mo>)</mo></mrow></mrow><mrow><mn>1</mn><mo>/</mo><mn>5</mn></mrow></msup></mrow></math></span> near rupture.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"347 ","pages":"Article 105531"},"PeriodicalIF":2.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145623770","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":"Corrigendum to “Natural convection within a non-uniformly heated cavity partly filled with a shear-thinning nanofluid and partly with air” [Journal of Non-Newtonian Fluid Mechanics 289 (2021) 104490]","authors":"Asma Ouahouah ,&nbsp;Nabila Labsi ,&nbsp;Xavier Chesneau ,&nbsp;Youb Khaled Benkahla","doi":"10.1016/j.jnnfm.2025.105516","DOIUrl":"10.1016/j.jnnfm.2025.105516","url":null,"abstract":"","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"347 ","pages":"Article 105516"},"PeriodicalIF":2.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145747479","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":"Approach to a similarity solution of the lubrication flow of an Oldroyd-B fluid through a hyperbolic pipe","authors":"John Hinch","doi":"10.1016/j.jnnfm.2025.105519","DOIUrl":"10.1016/j.jnnfm.2025.105519","url":null,"abstract":"<div><div>Sialmas &amp; Housiadas (2025), found a similarity solution of the Oldroyd-B equations for viscoelastic flow through a slowly varying axisymmetric contraction with a hyperbolic shape. We study whether inlet stresses decay onto this similarity solution before the end of the pipe, finding they do so only when a strain-rate based Deborah number is sufficiently small, <span><math><mrow><mi>D</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>e</mi></mrow></msub><mo>≲</mo><mn>1</mn></mrow></math></span>.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"347 ","pages":"Article 105519"},"PeriodicalIF":2.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145468551","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":"Friction factor for pulsatile flow of viscoelastic fluids in circular tubes and concentric annuli using a dynamic slip model at the walls","authors":"G. Barrera ,&nbsp;J. Arcos ,&nbsp;F. Méndez ,&nbsp;O. Bautista","doi":"10.1016/j.jnnfm.2025.105515","DOIUrl":"10.1016/j.jnnfm.2025.105515","url":null,"abstract":"<div><div>This work theoretically analyzes the influence of the slippage condition on the pulsatile flow of a viscoelastic fluid, whose rheological behavior follows the Jeffreys model, through circular and concentric annular tubes. A pulsatile pressure gradient causes the flow and a dynamic slip model is assumed on the walls of the tube <em>to depend on the past states of the local wall shear stress, similar to the concept of the viscoelastic fluid memory, where the local state of the stress depends on the past deformation history to which the fluid particles are subject</em> Hatzikiriakos (2012). As part of the assumptions, a periodic flow condition is considered, which is defined as the stage when the transient stage has finished. The hydrodynamics is obtained by solving the momentum equation, which is derived from a suitable combination of the Cauchy and Jeffreys constitutive equations, subject to the slip boundary condition that depends on the Jeffreys rheological model. The mathematical model is nondimensionalized, arising parameters that characterize the flow: the Womersley number <span><math><mi>Wo</mi></math></span>, the Deborah numbers <span><math><mi>De</mi></math></span> of the fluid, the slip relaxation number De_s associated to the dynamic slip boundary condition; the parameter <span><math><mi>Λ</mi></math></span> that represents the ratio between the relaxation and retardation times of the fluid; a parameter <span><math><mi>κ</mi></math></span> representing the ratio between the inner and outer radii of the annular tube; the slip parameters <span><math><msub><mrow><mi>β</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>β</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> related to the slippage at the walls. We illustrate the influence of the dimensionless parameters involved in the analysis through phase portrait diagrams that depict the dynamics of the flow. Based on the hydrodynamic field, we determine the instantaneous volumetric flow rate and evaluate the Poiseuille number as a function of the slip relaxation number. Additionally, we develop an asymptotic solution for the hydrodynamic field in the limit where <span><math><mrow><mi>Wo</mi><mo>≪</mo><mn>1</mn></mrow></math></span>, which aids in understanding the flow dynamics.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"347 ","pages":"Article 105515"},"PeriodicalIF":2.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145468550","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":"Single bubble dynamics in temperature-sensitive gelled propellants flowing through corrugated channels","authors":"Shuen He ,&nbsp;Qiang Li ,&nbsp;Hao Zhou ,&nbsp;Meng-Ge Li ,&nbsp;Yubai Li ,&nbsp;Yong He ,&nbsp;Wei-Tao Wu ,&nbsp;Yue Hua","doi":"10.1016/j.jnnfm.2025.105513","DOIUrl":"10.1016/j.jnnfm.2025.105513","url":null,"abstract":"<div><div>Bubble retention caused by the high viscosity of gelled propellants poses a significant challenge to combustion stability and performance in propulsion systems. To address this, the present study investigates the dynamic behavior of a single bubble in shear-thinning gelled propellants flowing through corrugated channels. Numerical simulations are conducted employing the Volume of Fluid (VOF) approach, with a modified Carreau–Yasuda model applied to represent the non-Newtonian viscosity characteristics. The effects of channel geometry, temperature, and inlet velocity on bubble dynamics and apparent viscosity are analyzed. The results indicate that bubble velocity is highest in trapezoidal channels, followed by sinusoidal and smooth channels. Increasing the corrugation amplitude enhances bubble speed, while higher temperatures reduce it. At low inlet velocities, the bubble maintains its shape; at moderate velocities, it deforms and recovers; and at high velocities, it splits. These findings provide valuable insights into bubble behavior in gelled propellants and contribute to the optimization of propulsion system design.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"347 ","pages":"Article 105513"},"PeriodicalIF":2.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145419947","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":"Transitional shear flow of elastic chains: A theoretical study based on molecular rheology","authors":"Abbas Sheikh","doi":"10.1016/j.jnnfm.2025.105511","DOIUrl":"10.1016/j.jnnfm.2025.105511","url":null,"abstract":"<div><div>This study investigates the time-dependent performance of the FENE-P and Rouse models as representative coarse-grained elastic chains. The analysis is conducted within two conventional rheometric shear flows: drag Couette flow, considered during both the “inception” and “start-up” phases, and pressure-driven Poiseuille flow. The primary objective of this research is to examine the rheological behavior with respect to the growth of shear stress, first normal stress difference, velocity development, and structural evolution, which includes the mean-square end-to-end distance, radius of gyration, and orientation functions of the elastic chains. To implement these molecular models, a CONNFFESSIT-like methodology was employed. Initially, the procedure was validated through a thorough comparison of the results with existing data, and subsequently applied under diverse conditions, including varying shear rates, chain segment numbers, and degrees of chain extensibility. The study revealed a fundamental distinction in the rheological behavior of the FENE-P chain, which has limited extensibility under flow, and the Rouse chain, which can extend indefinitely. Although start-up flow in a circular tube may appear straightforward, the application of these models through the micro–macro framework makes it possible to obtain new results, thereby demonstrating the versatility of the methodology.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"347 ","pages":"Article 105511"},"PeriodicalIF":2.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145366212","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}