Journal of Non-Newtonian Fluid Mechanics最新文献

{"title":"Investigating hemodynamic effects of consecutive arterial stenoses using an Eulerian granular two-phase model","authors":"Siddhartha Sankar Das,&nbsp;Dasari Abhiram,&nbsp;Swarup Kumar Mahapatra","doi":"10.1016/j.jnnfm.2025.105508","DOIUrl":"10.1016/j.jnnfm.2025.105508","url":null,"abstract":"<div><div>Understanding the influence of inter-stenosis length (or spacing) on hemodynamics in dually stenosed blood vessels is critical for advancing our knowledge of cardiovascular diseases and their treatment. This study employs a two-phase Eulerian-granular model, incorporating kinetic theory to capture red blood cell (RBC) particle mechanics, to investigate hemodynamics in a dual-stenosed arterial vessel with a 75% degree of stenosis (DOS). To validate our approach, we benchmarked it against in vitro experimental velocity profiles reported by Yeleswarapu et al. (1998). With a maximum deviation of 7.24%, the current model shows improved agreement compared to other tested approaches, including both single-phase (Newtonian) and two-phase (Euler–Euler two-fluid) models. Our findings reveal that shorter inter-stenotic spacings lead to elevated velocity gradients, intensifying local inertial effects. Conversely, a longer spacing allows the flow more distance to recover and re-laminarize, stabilizing the velocity profile. The presence of stenosis significantly disrupts the typical central RBC core surrounded by plasma. Specifically, at short inter-stenotic lengths, the disturbed flow from the first stenosis lacks sufficient distance to re-establish shear gradient-driven RBC migration. This inhibits the formation of a well-defined core hematocrit, resulting in a more dispersed or skewed RBC distribution. Furthermore, short inter-stenotic lengths promote stronger flow interaction and the generation of persistent helical vortices in the downstream region. A greater inter-stenotic length facilitates partial re-laminarization and vortex dissipation, leading to a reduction in downstream helicity and a transition toward more organized flow. Area-averaged wall shear stress (AWSS) increases with decreasing inter-stenotic length, particularly at the stenosis throat. Notably, this study also demonstrates that the single-phase Newtonian model over predicts flow separation and recirculation compared to our two-phase approach. Overall, this study highlights the capabilities of the two-phase Euler–granular model in accurately simulating complex blood flow dynamics within stenosed arteries, offering potential extensions for investigating the hemodynamics of other complex biological systems.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"346 ","pages":"Article 105508"},"PeriodicalIF":2.8,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145321353","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":"Inferring viscoplastic models from velocity fields: A physics-informed neural network approach","authors":"Martin Lardy ,&nbsp;Sham Tlili ,&nbsp;Simon Gsell","doi":"10.1016/j.jnnfm.2025.105512","DOIUrl":"10.1016/j.jnnfm.2025.105512","url":null,"abstract":"<div><div>Fluid-like materials are ubiquitous, spanning from living biological tissues to geological formations, and across scales ranging from micrometers to kilometers. Inferring their rheological properties remains a major challenge, particularly when traditional rheometry fails to capture their complex, three-dimensional, and often heterogeneous behavior. This difficulty is exacerbated by system size, boundary conditions, and other material-specific physical, chemical, or thermal constraints. In this work, we explore whether rheological laws can be inferred directly from flow observations. We propose a physics-informed neural network (PINN) framework designed to learn constitutive viscoplastic laws from velocity field data alone. Our method uses a neural network to interpolate the velocity field, enabling the computation of velocity gradients via automatic differentiation. These gradients are used to estimate the residuals of the governing conservation laws, which implicitly depend on the unknown rheology. We jointly optimize both the constitutive model and the velocity field representation by minimizing the physical residuals and discrepancies from observed data. We validate our approach on synthetic velocity fields generated from numerical simulations using Herschel–Bulkley, Carreau and Papanastasiou models under various flow conditions. The algorithm reliably infers rheological parameters, even in the presence of significant noise. We analyze the dependence of inference performance on flow geometry and sampling, highlighting the importance of shear rate distribution in the dataset. Finally, we explore preliminary strategies for model-agnostic inference via embedded model selection, demonstrating the potential of PINNs for identifying the most suitable rheological law from candidate models. This study illustrates how machine learning, and PINNs in particular, can enhance our ability to probe the rheology of complex fluids using velocity field data alone—paving the way for new approaches in computational rheology and material characterization.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"346 ","pages":"Article 105512"},"PeriodicalIF":2.8,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145363533","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":"2025-12-01","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":"Mitigating degradation-induced artifacts in rheological modeling of biopolymers using time-resolved rheology","authors":"Hadis Torabi ,&nbsp;Hadis Zarrin ,&nbsp;Ehsan Behzadfar","doi":"10.1016/j.jnnfm.2025.105509","DOIUrl":"10.1016/j.jnnfm.2025.105509","url":null,"abstract":"<div><div>Rheological analysis of biodegradable polymers is often complicated by structural mutations and thermal degradation during testing, leading to inaccurate data and unreliable modeling. These effects are particularly pronounced in conventional small-amplitude oscillatory shear (SAOS) experiments, which require extended exposure to elevated temperatures. In this study, an alternative approach is introduced based on time-resolved rheometry (TRR) to minimize the impact of degradation and isolate intrinsic rheological behavior. By capturing data across different timescales, this method decouples degradation kinetics from rheological responses, enabling the construction of more accurate flow curves and material functions. The effectiveness of this approach was validated by comparing it to conventional SAOS protocols across several polyhydroxyalkanoates. Our results show that TRR-based measurements yield more reliable predictions of viscoelastic properties, including relaxation moduli and startup shear viscosities. The improved data quality leads to superior fits in constitutive equation modeling. This methodology offers a more efficient and degradation-resistant strategy for rheological testing, with significant implications for optimizing the processing and performance of biodegradable polymers.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"346 ","pages":"Article 105509"},"PeriodicalIF":2.8,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145321354","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":"Rising and migration dynamics of an air bubble close to a wall in an elastoviscoplastic fluid","authors":"G. Esposito,&nbsp;Y. Dimakopoulos,&nbsp;J. Tsamopoulos","doi":"10.1016/j.jnnfm.2025.105482","DOIUrl":"10.1016/j.jnnfm.2025.105482","url":null,"abstract":"<div><div>We investigate the buoyancy-driven motion of an air bubble rising near a vertical solid wall in an elastoviscoplastic (EVP) fluid using three-dimensional direct numerical simulations. The EVP rheology is modelled via the Saramito-Herschel-Bulkley equation, capturing viscous, elastic, and plastic behaviour. Validation against prior experimental and numerical results for unbounded domains shows excellent agreement. The nearby wall induces a lateral migration to the bubble, with the velocity depending on wall distance, bubble volume, and fluid rheology. For larger bubbles, where inertia dominates, the lateral velocity is consistently positive, indicating persistent wall repulsion, and decreases with increasing wall distance. At long times, both lateral and vertical velocities collapse onto a master curve, depending only on the instantaneous wall distance. In contrast, smaller bubbles, dominated by elastic effects, exhibit a non-monotonic lateral velocity: positive near the wall but negative at larger distances, indicating the existence of an equilibrium lateral position. A parametric study highlights the role of deformability in modulating migration dynamics. More deformable bubbles show enhanced repulsion and rising velocities that depend on terminal shape: large, oblate bubbles rise more slowly due to increased cross section in the direction of flow, while smaller teardrop-shaped bubbles rise more efficiently. Increasing the yield stress strengthens the elastic response, shifting the lateral equilibrium distance closer to the wall. Conversely, decreasing the elastic modulus (softening the medium) increases the terminal velocity and enhances wall repulsion. Finally, variations in initial bubble shape and orientation affect transient deformation but have negligible influence on long-term migration or terminal state.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"345 ","pages":"Article 105482"},"PeriodicalIF":2.8,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144886963","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":"2025-11-01","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":"Evaluating viscoplastic properties with rheometry and PIV measurements in pipeline flows","authors":"Gláucio Kenji Matoba ,&nbsp;Daiane Mieko Iceri ,&nbsp;Helder Lima de Moura ,&nbsp;Roney Leon Thompson ,&nbsp;Annie Fidel-Dufour ,&nbsp;Thierry Palermo ,&nbsp;Marcelo Souza de Castro","doi":"10.1016/j.jnnfm.2025.105481","DOIUrl":"10.1016/j.jnnfm.2025.105481","url":null,"abstract":"<div><div>Non-Newtonian fluids, widely utilized in industries such as cosmetics, food processing, and petroleum, exhibit shear-dependent viscosity, necessitating precise rheological characterization for effective pipeline and equipment design. In the petroleum industry, for instance, oils can transition from Newtonian to non-Newtonian behavior under specific conditions, such as long-distance horizontal flow at high pressures and low temperatures (near crystallization). In these cases, oils often behave as viscoplastic fluids, requiring a minimum shear stress, known as yield stress, to initiate flow. The Herschel–Bulkley model is a well-established equation for describing the viscous behavior of such fluids through three rheological parameters: yield stress, power-law index, and consistency coefficient. The determination of these parameters is essential for computing flow characteristics, friction factors, and pressure drops—crucial for designing efficient transport systems. This study aims to characterize a viscoplastic fluid by determining its rheological properties from rheometric and in-situ measurements. To accomplish this, an experimental setup was developed using a model fluid prepared from an aqueous Carbopol and triethanolamine (neutralizing agent) solution. In addition to traditional rheometry, an in-situ approach was evaluated, integrating Particle Image Velocimetry (PIV) with differential pressure sensor data. The velocity profiles obtained enabled the reconstruction of shear rate profiles, while pressure drop data facilitated shear stress profile determination, allowing a flow curve reconstruction. Furthermore, the modified SoFA model (Suspension of Fractal Aggregates) was applied, utilizing Carbopol and Triethanolamine concentrations to estimate the rheological parameters and obtain the corresponding flow curve. A comparative analysis was conducted between serrated parallel-plate rheometry and the PIV–pressure drop method in a commercial 2<!--> <!-->inch (0.053<!--> <!-->m) pipeline under laminar flow of the aqueous Carbopol solution. The results confirmed that the Herschel–Bulkley model effectively fit the flow curves across all methodologies, with yield stress values deviating by less than 15%. However, consistency indices (<span><math><mi>K</mi></math></span>) obtained from PIV data were overestimated, likely due to the limited shear rate range at the low mean velocities tested. This study highlights the importance of integrating traditional rheometry with in-situ techniques for a comprehensive rheological characterization.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"345 ","pages":"Article 105481"},"PeriodicalIF":2.8,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144878664","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":"Linear instability in planar viscoelastic Taylor–Couette flow with and without explicit polymer diffusion","authors":"Miguel Beneitez ,&nbsp;Soufiane Mrini ,&nbsp;Rich R. Kerswell","doi":"10.1016/j.jnnfm.2025.105459","DOIUrl":"10.1016/j.jnnfm.2025.105459","url":null,"abstract":"<div><div>Elastic turbulence has been found in computations of planar viscoelastic Taylor–Couette flow using the Oldroyd-B model, apparently generated by a linear instability van Buel et al. (2018). We demonstrate that no such linear instability exists in the governing equations used unless some diffusion is added to the polymer conformation tensor equation, as might occur through a diffusive numerical scheme. With this addition, the polymer diffusive instability (PDI) Beneitez et al. (2023) exists and leads to chaotic flows resembling those found by van Buel et al. (2018). We show how finite volume or finite-difference discretisations of the governing equations can naturally introduce diffusive errors near boundaries which are sufficient to trigger PDI. This suggests that PDI could well be important in numerical solutions of wall-bounded viscoelastic flows modelled using Oldroyd-B and FENE-P even with no polymer stress diffusion explicitly included.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"345 ","pages":"Article 105459"},"PeriodicalIF":2.8,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144748967","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":"2025-11-01","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}

{"title":"The role of viscoelastic stress in an abruptly converging/diverging channel under the thin film approximation","authors":"M.H. Sari ,&nbsp;H. Ahmed ,&nbsp;C. Putignano ,&nbsp;G. Carbone ,&nbsp;L. Biancofiore","doi":"10.1016/j.jnnfm.2025.105469","DOIUrl":"10.1016/j.jnnfm.2025.105469","url":null,"abstract":"<div><div>We analyze a viscoelastic fluid, modeled by the Oldroyd-B constitutive equation, flowing in a sliding abruptly converging/diverging channel. We have chosen this geometry since it has connections to the typical elastohydrodynamic lubricated (EHL), for which recently (Sarı et al., 2024) have illustrated how a viscoelastic lubricant has a positive effect on the tribological performance by raising load and decreasing friction coefficient. We assume that the channel is thin and the magnitude of the “jump” is small enough allowing to take advantage of the thin film approximation. We observe that the step location is a critical factor for generating viscoelastic pressure due to the positive and constant increase in the volumetric flow rate. Presence of viscoelasticity quantified by the ratio between fluid relaxation time and residence time, called Deborah number. A high Deborah number leads to a significant increment in pressure if the step is close to the inlet, while, if it is close to an outlet, the pressure decreases compared to Newtonian flows. While in most of the work, the pressure at the boundaries (inlet and outlet) is set to zero, we also tested more realistic boundary conditions in which the pressure is equal to the average elastic stress, showing that the two kinds of boundary conditions have a similar qualitative behavior. Lastly, a texture geometry, composed by one converging followed by one diverging steps, is inspected to mimic an EHL profile. We find what is the optimal distance between the steps to maximize the load. The role of the elastic stress in this texture profile is finally discussed.</div></div>","PeriodicalId":54782,"journal":{"name":"Journal of Non-Newtonian Fluid Mechanics","volume":"345 ","pages":"Article 105469"},"PeriodicalIF":2.8,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144828746","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}