Rheologica Acta最新文献

{"title":"Analytical solutions for coupled orientation–stress Poiseuille flow of short fiber suspensions with wall slip","authors":"Kostas D. Housiadas,&nbsp;Antony N. Beris,&nbsp;Suresh G. Advani","doi":"10.1007/s00397-026-01586-3","DOIUrl":"10.1007/s00397-026-01586-3","url":null,"abstract":"<div><p>We derive analytical solutions for the fully coupled, incompressible, steady, fully developed Poiseuille flow of a suspension of non-Brownian, short, rigid fibers in the presence of wall slip. The flow geometry considered is either a two-dimensional planar channel (slit) or an axisymmetric circular pipe (nozzle). The rheology of the matrix is modeled as a power-law generalized Newtonian fluid. The two-way coupling between the velocity field and the fiber-induced extra stress is incorporated explicitly into the momentum balance. Fiber orientation is described using a second-order orientation tensor formulation that accounts for finite-aspect-ratio fibers and fiber–fiber interactions, together with a hybrid closure approximation for the fourth-order orientation tensor. Closed-form analytical expressions for the velocity and pressure fields are derived for both geometries, while the orientation tensor associated with the hybrid closure is obtained numerically. The analysis shows that wall slip is necessary for the two-way coupling to produce non-trivial modifications to the pressure drop and velocity profiles. Under these conditions, the fiber-induced extra stress leads to a significant increase in the pressure drop required to sustain a prescribed volumetric flow rate, while the velocity profile is only weakly affected. The resulting solutions are also used to investigate parametrically the effects of the material parameters on the pressure and velocity profiles.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"65 9","pages":"763 - 772"},"PeriodicalIF":2.7,"publicationDate":"2026-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00397-026-01586-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148807268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"An experimental method for evaluating fiber-fiber interactions in fiber suspensions using shear reversal","authors":"Koki Maeda,&nbsp;Tsutomu Takahashi","doi":"10.1007/s00397-026-01587-2","DOIUrl":"10.1007/s00397-026-01587-2","url":null,"abstract":"<div><p>Inter-fiber interactions in concentrated fiber suspensions give rise to complex rheological behavior. In this study, we investigated how hydrodynamic and contact interactions contribute to the transient and oscillatory responses of a concentrated fiber suspension by using shear-reversal-based experimental protocols. The pseudo-steady-state viscosity immediately after shear reversal exhibited a concentration dependence consistent with the scaling predicted by a theory of long-range hydrodynamic interactions over the concentration range examined, supporting the interpretation that fiber-fiber contact contributions were substantially suppressed after reversal. The stress overshoot characteristic of fiber suspensions was also observed under large-amplitude oscillatory shear (LAOS), producing a pronounced deviation from the correspondence based on the Cox-Merz rule at intermediate strain amplitudes. In the LAOS-SR experiments, when the reverse strain accumulated after the preceding flow reversal within the LAOS cycle was smaller than the characteristic overshoot strain, the subsequent SR response exhibited a sigmoidal transition rather than an overshoot. At low strain amplitudes, hydrodynamic interactions provided the dominant contribution, revealing the strain-dependent nature of inter-fiber interactions. Based on these findings, parallel superposition, in which a small-amplitude oscillation was superposed on steady shear, was used as a probe to extract hydrodynamic and contact contributions. Under high-frequency small-amplitude oscillation, shear reversal occurred within each cycle, and a low-viscosity regime associated with the suppression of contact interactions was observed together with cycle-by-cycle transient changes. These results show that the rheology of concentrated fiber suspensions is governed by both fiber orientation and inter-fiber interactions, and provide new insight into how orientation and contact formation are coupled in such systems.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"65 9","pages":"745 - 762"},"PeriodicalIF":2.7,"publicationDate":"2026-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148807495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An explanation for negative parallel superposition moduli","authors":"Eric M. Burgeson,&nbsp;Simon A. Rogers","doi":"10.1007/s00397-026-01588-1","DOIUrl":"10.1007/s00397-026-01588-1","url":null,"abstract":"<div><p>Parallel superposition flows have been examined in the rheology literature since 1965; they consist of simultaneously applied steady shear and oscillatory flows. One interesting result found from the study of parallel superposition flows has been reportedly negative values of the dynamic moduli. This apparently unphysical result has led to some speculation regarding its origin. In this work, we provide mathematical and experimental evidence showing that negative moduli are potentially due to the oscillatory signal being distorted by inclusion of the steady shear component in the Fourier analysis. However, the moduli can be easily corrected to restore physical meaning.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"65 9","pages":"773 - 783"},"PeriodicalIF":2.7,"publicationDate":"2026-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00397-026-01588-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148807582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"A probabilistic data-driven constitutive modeling framework for complex fluids","authors":"Nayeon Park,&nbsp;Sangwoong Yoon,&nbsp;Howon Jin,&nbsp;Jun Dong Park,&nbsp;Jin Suk Myung","doi":"10.1007/s00397-026-01585-4","DOIUrl":"10.1007/s00397-026-01585-4","url":null,"abstract":"<div><p>Conventional constitutive modeling of complex fluids typically relies on deterministic parameter fitting or discrete mode selection, which limits flexibility in representing diverse rheological responses. We propose the Rheological Probabilistic (RheoPro) framework, a data-driven constitutive modeling approach that extends physics-based kinetic models into stochastic ensembles and infers parameter-generating distributions from differentiable, closed-form evaluations of small-amplitude oscillatory shear moduli and steady-shear viscosity. As a representative implementation, we formulate a Generalized Dumbbell Soft Glassy Rheology (GDSGR) model that couples activated yielding dynamics with bead-spring kinematics. A reparameterization trick enables stable gradient-based optimization without repeated time stepping during training. When trained on single- and multi-mode Giesekus and thixotropic elasto-viscoplastic benchmarks, the optimized GDSGR model reproduces linear moduli and nonlinear flow curves with log-space coefficients of determination near unity. For the multi-mode benchmark, the inferred distribution represents the relaxation spectrum as a continuous lifetime distribution without a prescribed mode count. In the thixotropic benchmark, it captures the yield-dominated low-shear response and viscoelastic–plastic coupling, while showing that moduli and steady-shear viscosity alone may not uniquely constrain transient kinetics. This constitutive modeling framework remains robust under moderate synthetic measurement noise and provides an interpretable, extensible foundation for distribution inference across linear viscoelastic and nonlinear steady-shear regimes.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"65 9","pages":"785 - 804"},"PeriodicalIF":2.7,"publicationDate":"2026-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148807578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Visualizing shear-induced structures in carbon black gels by tomo-rheoscopy","authors":"Julien Bauland,&nbsp;Stéphane G. Roux,&nbsp;Stefan Gstöhl,&nbsp;Christian M. Schlepütz,&nbsp;Michael Haist,&nbsp;Thibaut Divoux","doi":"10.1007/s00397-026-01583-6","DOIUrl":"10.1007/s00397-026-01583-6","url":null,"abstract":"<div><p>Suspensions of attractive particles form space-spanning networks that endow the suspension with solid-like behavior at rest. The microstructure of these colloidal gels depends sensitively on the shear history and on the path followed across the sol-gel transition, resulting in viscoelastic properties that can be tuned by shear. Here, we report <i>in situ</i> X-ray tomo-rheoscopy experiments on carbon black gels whose elastic properties exhibit a non-monotonic dependence on the shear intensity applied prior to flow cessation. By directly imaging the gel microstructure under a well-controlled rheological protocol, we reveal the emergence of pronounced structural heterogeneities extending from tens to hundreds of microns – length scales far larger than those accessible by conventional scattering techniques such as ultra-small angle X-ray scattering. In particular, we show that only the low-shear reinforcement of elasticity correlates with a growing mesoscale correlation length, while high-shear strengthening occurs without detectable mesoscale reorganization. These observations demonstrate that flow memory in colloidal gels is not solely governed by local particle rearrangements, but is also encoded in a mesoscale structural organization extending up to 100 times the particle size. More broadly, this work highlights the power of X-ray tomo-rheoscopy to uncover large-scale structural signatures of flow history in soft materials, opening new perspectives to tailor their mechanical properties.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"65 9","pages":"805 - 818"},"PeriodicalIF":2.7,"publicationDate":"2026-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148807432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rheometer methods for characterising and comparing foams: an example using household detergents","authors":"Ceri Allgood,&nbsp;Thomas J. Jones,&nbsp;Stephen C. Boothroyd","doi":"10.1007/s00397-026-01584-5","DOIUrl":"10.1007/s00397-026-01584-5","url":null,"abstract":"<div><p>Consumer opinions of household detergents are influenced by the appearance, handling, and stability of the foams that they produce. Therefore, developing rheometer methods to characterise household detergent foams is of great importance for product development, so that successful product traits can be quantified and new formulations can be tested against known benchmarks. Here, we develop methods for measuring the rheological properties of foams created using common brands of washing-up liquids. We use a commercially available rheometer, the Anton Paar MCR702e, with the Powder Rheometry Flow Cell module acting as a wide-gap concentric cylinder geometry. Our results for complex shear modulus and yield stress show good agreement with previous studies of foams and emulsions, demonstrating that this system can reliably characterise foam rheology. We explore the physical mechanisms that might cause rheological differences between foams, with a view to informing product development and further research.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"65 9","pages":"819 - 834"},"PeriodicalIF":2.7,"publicationDate":"2026-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00397-026-01584-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148807183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Instrument phase errors and inertial leakage in optimally windowed chirp (OWCh) rheometry","authors":"Peter Angerman,&nbsp;Leonhard Faulhammer,&nbsp;Lars Bauer,&nbsp;Jan Haeberle,&nbsp;Daniel J. Curtis","doi":"10.1007/s00397-026-01580-9","DOIUrl":"10.1007/s00397-026-01580-9","url":null,"abstract":"<div><p>Optimally windowed chirp-based rheometry (OWCh) enables rapid acquisition of linear viscoelastic spectra and has become an increasingly popular alternative to conventional discrete frequency sweep measurements, particularly for time-evolving materials. However, the accuracy of chirp-based protocols is sensitive to instrumental and signal-processing artefacts that can distort the recovered complex modulus. In this work, we demonstrate that timestamp-induced phase offsets produce a frequency-dependent rotation of the complex modulus, causing crosstalk between the storage and loss moduli. Further, when OWCh measurements are undertaken using a combined motor transducer rheometer the phase offset and instrument inertia are intrinsically coupled such that the inertial effect, which is typically assumed to affect only the storage modulus, leaks into the loss modulus. Analytical modelling reveals a cubic frequency scaling of the resulting loss modulus error. Using numerical examples and experimental measurements obtained on multiple rheometers and materials, we show that conventional inertia correction is insufficient to recover the true material response when phase offsets are present. We further introduce a practical calibration procedure that enables phase correction to be performed prior to inertia correction, restoring quantitative agreement between chirp-based and frequency sweep measurements. These results establish a physically consistent correction sequence for chirp-based rheometry and provide a robust framework for chirp-only rheometry.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"65 8","pages":"735 - 744"},"PeriodicalIF":2.7,"publicationDate":"2026-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00397-026-01580-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148496661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Rheological aspects of the day-to-day variability of human saliva","authors":"Ioannis Velopoulos,&nbsp;Maria Dimopoulou,&nbsp;Jianshe Chen,&nbsp;Christos Ritzoulis","doi":"10.1007/s00397-026-01581-8","DOIUrl":"10.1007/s00397-026-01581-8","url":null,"abstract":"<div><p>Human saliva is a complex biological fluid whose rheological and interfacial characteristics are crucial for oral lubrication, bolus formation, swallowing, and sensory perception. Despite its importance, the degree of intra-individual variability in saliva structure and rheological behavior under controlled sampling conditions remains inadequately defined. In this study, unstimulated whole human saliva collected from a single donor over five consecutive days under standardized routine was examined in its uncentrifuged (UN – UWHS) and centrifuged state (C – UWHS). Particle size analysis revealed pronounced day-to-day variability, while centrifugation consistently reduced the contribution of larger populations. Extensional rheometry showed strong fluctuations in filament thinning dynamics, with relaxation times ranging from 0.2 to 6.2 s in native saliva and decreasing to 0.002–0.04 s after centrifugation. In contrast, shear viscosity exhibited lower variability, although native saliva consistently displayed higher viscosity and more pronounced shear-thinning behaviour. Size exclusion chromatography (SEC) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed multiple macromolecular populations, while confocal microscopy indicated that saliva foam is stabilized by a protein-rich interfacial layer. Overall, the results demonstrate that saliva is a dynamic viscoelastic colloid with substantial intra-individual variability even under controlled sampling conditions. These findings are relevant for improving experimental reproducibility in saliva rheology studies and for guiding the development of biomimetic saliva substitutes for xerostomia.</p><h3>Graphical Abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"65 8","pages":"719 - 734"},"PeriodicalIF":2.7,"publicationDate":"2026-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148496657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design, development, and performance assessment of a modified concentric cylindrical magnetorheometer for precise rheological characterisation of MR fluids","authors":"Bittu Kumar Singh,&nbsp;Chiranjit Sarkar","doi":"10.1007/s00397-026-01582-7","DOIUrl":"10.1007/s00397-026-01582-7","url":null,"abstract":"<div><p>Magnetorheological (MR) fluids exhibit field-dependent yield stress and viscosity, enabling their use in adaptive damping, braking, and clutch systems. However, precise rheological characterisation remains difficult due to issues such as fluid loss from centrifugal forces, non-uniform magnetic fields, and deformation of measurement gaps under magnetic loading. This work introduces the design, magnetic optimisation, and experimental validation of a new concentric cylindrical magnetorheometer that overcomes these challenges. The proposed device features an enclosed geometry to prevent fluid loss, a fixed-radius shear design to maintain consistent shear rates, and an optimised magnetic circuit to provide uniform flux distribution without creating normal magnetic forces. Magnetic circuit modelling, supported by finite element simulations, confirms enhanced field uniformity and efficiency. Rheological testing with custom-prepared MR fluids demonstrates the instrument’s capability to measure dynamic yield stress under varying magnetic field strengths, rotor–stator material combinations, particle concentrations, and gap sizes. Results show a strong link between magnetic material configuration and yield stress, significant increases in yield stress with higher carbonyl iron particle content, and performance reductions at larger gap sizes. The device’s accuracy and repeatability make it a reliable platform for advanced MR fluid research and application development at high shear rates.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"65 8","pages":"693 - 704"},"PeriodicalIF":2.7,"publicationDate":"2026-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148496658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Controlling fluid gel rheology through κ-carrageenan and locust bean gum interactions","authors":"Simona Russo Spena,&nbsp;Yanshen Zhu,&nbsp;Nino Grizzuti,&nbsp;Rossana Pasquino,&nbsp;Deniz Z. Gunes","doi":"10.1007/s00397-026-01578-3","DOIUrl":"10.1007/s00397-026-01578-3","url":null,"abstract":"<div><p>Fluid gels are suspensions of gelled particles dispersed within a continuous liquid phase, formed by applying shear during gelation. Although widely used to functionalise materials across industries, controlling and tuning their rheological properties through particle design remains a major challenge due to the significant coupling between formulation variables, gelation kinetics, and shear-induced micro structuring. In this work, we demonstrate that mixtures of κ-Carrageenan (κ-C) and Locust Bean Gum (LBG) enable precise and predictable tuning of fluid gel rheology by simply adjusting the LBG/κ-C ratio at a fixed total hydrocolloid concentration (1 wt%). This represents a simplified design strategy in which the compositional ratio acts as a direct control parameter over the final rheological response.</p><p>The rheology of the fluid gels arises from the interplay between the mechanical properties of the gel particles, inherited from the corresponding quiescent gel, and the interactions established between particles within the suspension. Importantly, this allows the rheological signature of the quiescent gel to be used as a practical descriptor of the resulting fluid gel behaviour, despite the structural rearrangements induced by shear. Remarkably, negligible or only very modest increases in elastic modulus were observed over aging times up to 2000 s following a rejuvenation step, i.e. within time scales relevant to consumption (e.g. beverage applications). This limited aging behaviour further highlights the high degree of control exerted by composition alone, in contrast to other systems (e.g. gellan/Ca²⁺) that exhibit significant post-processing structuring. Remarkably, no significant aging effects were found in relatively young fluid gels (15 min time scale). These findings offer an accessible approach for designing fluid gels with targeted textural and functional properties, enabling the rational formulation of food products structured with fluid gels, simply based on bulk gel properties.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"65 8","pages":"705 - 717"},"PeriodicalIF":2.7,"publicationDate":"2026-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148496662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}