Journal of Non-Newtonian Fluid Mechanics最新文献

{"title":"Modelling viscoplastic interfacial flows inclusive of curvature effects","authors":"P.T. Griffiths ,&nbsp;D. Xu ,&nbsp;L. Davoust","doi":"10.1016/j.jnnfm.2025.105498","DOIUrl":"10.1016/j.jnnfm.2025.105498","url":null,"abstract":"<div><div>This study presents a theoretical and numerical investigation of interfacial flows of oxidised liquid metals in a shallow annular channel in the absence of inertial effects. For the first time, viscoplastic surface behaviour induced by oxidation is modelled using a bi-viscosity law within a framework that also accounts for interfacial curvature governed by the Young–Laplace equation. By solving a coupled bulk-surface flow system, the effects of surface rheology, contact angle, and dimensionless capillary length on surface velocity and surface shear rate profiles are quantified. Results highlight the competing influences of hydrophobicity and viscoplasticity on surface and bulk flow characteristics and demonstrate that accurate modelling of such systems necessitates inclusion of both curvature and non-Newtonian surface effects. In appropriate limits, our numerical results are validated against semi-analytical solutions. Our findings offer insights relevant to metal casting applications.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"346 ","pages":"Article 105498"},"PeriodicalIF":2.8,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222681","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":"Wrinkling of a viscoplastic plate on a viscous substrate","authors":"Thomasina V. Ball ,&nbsp;A.F. Bonfils ,&nbsp;Jerome A. Neufeld","doi":"10.1016/j.jnnfm.2025.105496","DOIUrl":"10.1016/j.jnnfm.2025.105496","url":null,"abstract":"<div><div>We study the formation of wrinkles in a clamped viscoplastic plate overlying a thin viscous substrate, which is compressed horizontally. When the plate is purely viscous, the compressive force in the plate is constant and is set by the velocity boundary conditions. The wavelength of the emergent wrinkles depends on the thicknesses of the two layers and the ratio of the viscosities. As the domain length is reduced relative to the characteristic wavelength, the spatial profile and growth rate start to depend heavily on the domain length and imposed clamped boundary conditions. Introducing a yield stress to the plate initially increases the compressive force, proportional to the Bingham number, due to the requirement for the plate to be yielded throughout the domain. As the bending moments increase in the plate, the compressive force is relieved and a transition occurs where the plate begins to yield through bending rather than compression. During this transition, the plate is dominated by plugged, unyielded regions leading to localisation and the formation of straight-sided wrinkles.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"346 ","pages":"Article 105496"},"PeriodicalIF":2.8,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222682","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":"Note on the theoretical analysis of the energy equation for viscoelastic flows under non-isothermal material properties","authors":"Carlos Veiga Rodrigues ,&nbsp;Francisco Vide ,&nbsp;Alexandre M. Afonso ,&nbsp;Fernando T. Pinho","doi":"10.1016/j.jnnfm.2025.105497","DOIUrl":"10.1016/j.jnnfm.2025.105497","url":null,"abstract":"<div><div>A theoretical analysis of the energy equation for viscoelastic flows is performed, following the work of Peters and Baaijens [Peters GWM, Baaijens FPT, 1997 J. Non-Newt. Fluid Mech., 68:205–224], and aimed at extending it to deal with fluids having temperature-dependent and time-dependent fluid properties, which give rise to new terms in the transport equation that are not present in the original Peters and Baaijens work. Lastly, an application of the extended energy equation is carried out using the PTT network model.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"346 ","pages":"Article 105497"},"PeriodicalIF":2.8,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145222683","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":"Turbulence characteristic evolution in jets interacting with viscoplastic fluids","authors":"H. Hassanzadeh ,&nbsp;M.H. Moosavi ,&nbsp;I.A. Frigaard ,&nbsp;S.M. Taghavi","doi":"10.1016/j.jnnfm.2025.105494","DOIUrl":"10.1016/j.jnnfm.2025.105494","url":null,"abstract":"<div><div>We experimentally study the dynamics of a horizontal jet of a Newtonian fluid injected into a viscoplastic ambient fluid (Carbopol gel) to simulate jet cleaning in plug and abandonment operations of oil and gas wells. The jet flow is analyzed using high-speed imaging, planar laser induced fluorescence, and time-resolved tomographic particle image velocimetry techniques to capture concentration and velocity fields with high spatial and temporal resolution. By varying the Reynolds and Bingham numbers, we analyze three recently identified flow regimes, i.e., mixing, mushroom, and fingering, focusing on their mixing index, velocity fields, fluctuation intensity, half-radius, vorticity, Reynolds stresses, probability density functions, and statistical moments (skewness and kurtosis). In the mixing regime, velocity and vorticity symmetry, axisymmetric mixing, and dominant axial Reynolds stresses align with Newtonian empirical correlations. The mushroom regime shows slight asymmetry, reduced mixing from turbulence suppression by yield stress, and moderate turbulence, while the fingering regime features pronounced asymmetry, erratic fluctuations, and suppressed velocity due to viscoplastic resistance. Self-similarity analysis of velocity, concentration, and Reynolds stress profiles confirms strong scaling in the mixing regime, partial scaling in the mushroom regime, and deviations in the fingering regime, where viscoplastic effects disrupt jet structure and turbulence.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"346 ","pages":"Article 105494"},"PeriodicalIF":2.8,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107993","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":"Erratum to “A theory of die-swell revisited”","authors":"Randy H. Ewoldt","doi":"10.1016/j.jnnfm.2025.105495","DOIUrl":"10.1016/j.jnnfm.2025.105495","url":null,"abstract":"","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"346 ","pages":"Article 105495"},"PeriodicalIF":2.8,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159832","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":"Pairwise interactions of active particles in a yield stress fluid","authors":"Yan Xia ,&nbsp;Zhaosheng Yu ,&nbsp;Xiao Hu ,&nbsp;Chenlin Zhu ,&nbsp;Zhaowu Lin","doi":"10.1016/j.jnnfm.2025.105486","DOIUrl":"10.1016/j.jnnfm.2025.105486","url":null,"abstract":"<div><div>In this work, we numerically investigate the hydrodynamic interactions between two active particles (modeled as squirmers) in a Bingham yield stress fluid, and quantify the influence of the Bingham number and squirmer type on reorientation and scattering in face-to-face and crossing configurations. In the face-to-face configuration, increased Bingham number leads to greater reorientation of neutral and puller-type squirmers. In crossing interactions, yield stress suppresses the strong deflection observed in Newtonian fluids at small incidence angles. In contrast, for larger initial angles, the final separation angle between the squirmers is significantly increased in a yield stress fluid compared to that in a Newtonian fluid. To elucidate the underlying mechanism, we compute hydrodynamic torques on particles by constraining their orientations while allowing translation. In the face-to-face configuration, we find that yield stress amplifies the near-field torques on each particle, driving them to rotate away from one another and thereby increasing scattering. In the side-by-side configuration, yield stress qualitatively alters the sign and magnitude of the hydrodynamic torque on neutral and puller-type squirmers, reducing their tendency to rotate away and thereby favoring sustained parallel swimming. These results provide insight into the rheological behavior and transport properties of active suspensions in complex fluids.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"345 ","pages":"Article 105486"},"PeriodicalIF":2.8,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145003979","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":"General evaluation of the pressure gradient for lubrication flows in varying channels with applications to linear and hyperbolic contractions","authors":"Panagiotis Sialmas,&nbsp;Kostas D. Housiadas","doi":"10.1016/j.jnnfm.2025.105487","DOIUrl":"10.1016/j.jnnfm.2025.105487","url":null,"abstract":"<div><div>Under the classic lubrication approximation, we develop a unified framework for evaluating the pressure gradient of an incompressible, isothermal viscoelastic fluid in a symmetric channel with slowly varying geometry, including inertia. Exploiting the independence of the pressure gradient from the wall-normal coordinate—a property absent in general 2D planar or 3D axisymmetric flows—we derive multiple integral expressions for the pressure gradient and the corresponding average pressure drop required to maintain a constant flow rate. The derivations use the momentum balance formulated via the extra-stress tensor, providing a flexible, formal, and rigorous procedure, and the physical significance of each expression is discussed.</div><div>To bypass choosing among these expressions, we introduce a new set of lubrication equations based on a streamfunction, mapped coordinates, and transformed polymer extra-stress components. This formulation automatically satisfies the continuity equation, the constraints due to fluid incompressibility, the boundary conditions, and the flow symmetries, allowing the pressure gradient to be determined <em>a posteriori</em> and providing a tool for consistency and accuracy checks.</div><div>The equivalence of the integral expressions is illustrated in two representative cases: (i) Newtonian inertial flow in a linearly contracting channel, and (ii) viscoelastic inertialess flow in a hyperbolic contraction. In both cases, the predicted average pressure drop agrees very well with high-order asymptotic solutions post-processed via Padé approximants, high-accuracy spectral simulations, and DNS results from the literature. The framework provides a rigorous, general, and computationally robust tool for analyzing lubrication flows of viscoelastic fluids and can be easily extended to other complex fluids and broader flow conditions.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"346 ","pages":"Article 105487"},"PeriodicalIF":2.8,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145061730","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":"Pore-network modeling of viscoplastic flows: Exploring the Hele-Shaw cell flow analogy","authors":"Hossein Rahmani ,&nbsp;Ian Frigaard","doi":"10.1016/j.jnnfm.2025.105485","DOIUrl":"10.1016/j.jnnfm.2025.105485","url":null,"abstract":"<div><div>We explore the relationship between a yield stress fluid flow in a Hele-Shaw cell with irregular walls, and a non-Darcy 2D porous medium flow with limiting pressure gradient. The continuum (Hele-Shaw) flow is a much-studied simplification of a cementing displacement flow model, solved via a variational formulation that leads to a convex streamfunction minimization problem. Our interest is with the analogy between the discretization used for the numerical solution and network flows that model the associated porous media flow, i.e. via the pore-throat approach. A staggered mesh, with pressure nodes at the cell corners and streamfunction nodes at the cell center is used for the continuum problem, which naturally separates into a network representation comprising primal and dual graphs, linking streamfunction and pressure nodes, respectively. We show explicitly how the continuum model defines a network model and vice versa. We develop the variational form of the network flow, including an appropriate (discrete) streamfunction minimization and a discrete version of the principle of virtual work.</div><div>Two network models are explored, based on different interpretations of the minimization problem. The network flow results are compared with analogous computed continuum flow results in 3 specific geometries. We find that our network model I, which is the most natural interpretation of the continuum model as a network flow using our discretization, generally under-predicts flow rates. This is problematic from the perspective of considering the network flow as an approximation to the porous media or Hele-Shaw flow. Network model II rectifies this situation, via a pressure interpolation method. In our examples we find that the network II flow converges to the continuum flow as the mesh and network are refined. This is not the usual comparison made, as in many pore-throat models the network is fixed according to the underlying pore-space geometry. Despite the differences, both network models have their own advantages and disadvantages. Network model I offers a more natural way of modeling the flow and is easier to apply, for example to complex meshes, e.g. unstructured triangular. Network model II gives the more accurate physical representation of the Hele-Shaw flow. Lastly, we have developed approximate algebraic relationships for the total flow rate as a function of the total applied pressure gradient, both close to the critical onset pressure and for large pressure gradients. These correlations align well with previous findings for Bingham fluid flows in porous media.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"345 ","pages":"Article 105485"},"PeriodicalIF":2.8,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144917815","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 investigation of viscoelastic flow characteristics: Giesekus fluid past a circular cylinder near a flat wall","authors":"Fanji Sun ,&nbsp;Bo Guo ,&nbsp;Luqi Cao ,&nbsp;Yuke Li ,&nbsp;Xinhui Si","doi":"10.1016/j.jnnfm.2025.105484","DOIUrl":"10.1016/j.jnnfm.2025.105484","url":null,"abstract":"<div><div>This study numerically investigates viscoelastic flow dynamics around a cylinder near a flat wall using the Giesekus model in OpenFOAM. For the boundary layer on the flat wall, both elastic and shear-thinning properties reduce boundary layer thickness. The coupled elastic and shear-thinning effects of the Giesekus fluid flow around the near-walled cylinders are analyzed through systematic parameters. At high mobility factor, increasing the Weissenberg number primarily enhances the shear-thinning effect, leading to intensified drag and lift fluctuations. However, at low mobility factor, it mainly strengthens the elastic effect, evidenced by the elongation of recirculation zone in the wake. The comparative simulations using the Carcarau model further reveal the competing flow mechanisms between flow stabilization due to elasticity and destabilization caused by shear thinning. In addition to the fluid property parameters, smaller gap ratios enhance flow stability by maintaining lower flow velocity in the gap. Conversely, larger gap ratios increase the velocity, causing high-momentum fluid flow through the gap to deflect and interact with the shear layer formed by the cylinder’s upper wake, thereby triggering vortex shedding. Similarly, a reduced flow development length accelerates the flow velocity in the gap and thins the boundary layer of the plat wall, which promotes flow instability. Both larger gap ratios and shorter development lengths increase the drag and alter the lift direction.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"345 ","pages":"Article 105484"},"PeriodicalIF":2.8,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144895884","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":"Penetration dynamics of non-Newtonian fluids into axially varying capillaries","authors":"A. Beitollahi ,&nbsp;H. Alamdari ,&nbsp;S.M. Taghavi","doi":"10.1016/j.jnnfm.2025.105483","DOIUrl":"10.1016/j.jnnfm.2025.105483","url":null,"abstract":"<div><div>The capillary-driven penetration of non-Newtonian fluids in capillaries with irregular walls is crucial in industrial applications, such as anode manufacturing for aluminum production, where a mixture of coal-tar pitch and fine petroleum coke particles (binder matrix) impregnates the open pores of coarse coke particles. Our study presents a semi-analytical model for capillary-driven flow of shear-thinning fluids in axially varying, wavy-walled microchannels, representative of coke open pore geometries. Incorporating weak inertia, viscous dissipation, and dynamic contact angle behavior (governed by a molecular kinetic theory), the model is systematically derived using lubrication theory and a power-law rheology, yielding a reduced-order equation for the advancing meniscus. The model is validated and calibrated via computational fluid dynamics simulations to extract the dynamic contact angle correction parameter. Our analysis quantifies three distinct penetration regimes and their transition dynamics: inertia-dominated, interfacial dissipation-dominated, and viscous dissipation-dominated. Analytical scaling laws and regime transition correlations are validated across varying power-law indices, Laplace numbers, contact angles, and geometrical features. The power-law index most strongly influences penetration, followed by static contact angle and geometric phase shift, while Laplace number affects early-time behavior. Dynamic contact angle analysis highlights the critical role of interfacial dissipation in irregular geometries. Applied to binder matrices with measured rheology, the model shows that increased fine coke content or channel irregularity significantly delays impregnation.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"345 ","pages":"Article 105483"},"PeriodicalIF":2.8,"publicationDate":"2025-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145018415","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}