Search Results (418)

The two-dimensional thermal liquid jet of a non-Newtonian power-law fluid is investigated under shear-rate-dependent thermal diffusivity, resulting in a one-way coupled nonlinear system governing momentum and thermal transport. Two physically distinct free-surface thermal boundary conditions are examined: adiabatic insulation and convective heat loss. Conservation laws and conserved quantities for the governing system are derived systematically using the multiplier method. By coupling an appropriate conserved vector with an admitted Lie point symmetry, the governing partial differential equations are reduced to a coupled system of ordinary differential equations. Closed-form parametric families of solutions are then obtained for the thermal field. The analysis reveals fundamentally different thermal transport mechanisms across rheological regimes: shear-thinning fluids enhance thermal redistribution and become increasingly sensitive to convective cooling as the Biot number increases, whereas shear-thickening fluids suppress internal thermal transport, promoting greater thermal retention within the jet core and reducing the influence of free-surface cooling. These findings clarify the interplay between rheology, nonlinear thermal diffusion and free-surface cooling and provide new analytical insight into downstream thermal transport in non-Newtonian liquid jets. Full article

This study presents an integrated Computational Fluid Dynamics (CFD) and machine learning framework for analyzing and optimizing classical wire coating processes involving non-Newtonian power-law fluids. A two-dimensional axisymmetric CFD model was developed in ANSYS Fluent 2024R1 to investigate the effects of the power-law index (n = 0.3–1.0) on flow, pressure, temperature, and density fields under non-isothermal conditions. A Latin Hypercube Sampling-based Design of Experiments was coupled with surrogate modelling and Sobol sensitivity analysis to evaluate process performance and identify optimal operating conditions. The results showed that velocity distributions were highly dependent on fluid rheology, with shear-thinning fluids producing broader plug-like flow regions and more uniform velocity profiles. In contrast, pressure, temperature, and density fields exhibited limited sensitivity to variations in the power-law index. Optimization indicated that low power-law indices, moderate pressure gradients, and low-to-moderate wire speeds maximize coating thickness while minimizing material loss. Ridge Polynomial Regression achieved excellent predictive accuracy for all response variables (R² > 0.995). Sensitivity analysis revealed that the initial die gap is the dominant factor governing coating thickness, whereas material loss is influenced by combined effects of die geometry, fluid rheology, and wire speed. The proposed framework provides an efficient tool for process optimization and material conservation in industrial wire coating applications. Full article

Background: The present study aimed to develop and characterize three honey- and essential oil-based structured systems intended for topical skin application. Materials and Methods: The semisolid systems were prepared as oil-in-water structured emulsions containing four types of honey (Manuka, Tualang, chestnut, and manna), three essential oils (palmarosa, cistus, and lavender), and five vegetable oils (pomegranate seed, aloe, centella, hemp seed, and calendula). Each formulation consisted of two honey types, one essential oil, and two vegetable oils, with final concentrations of 5% honey and 0.1–0.2% essential oil. The formulations were investigated through physicochemical, rheological, and in vivo skin evaluations. Results: Rheological analysis demonstrated non-Newtonian pseudoplastic behavior with shear-thinning and thixotropic characteristics, indicating that the systems are structured, semisolid, and suitable for topical application. Differences in spreadability and consistency suggested variations in the internal organization of the emulsion matrices. In vivo skin assessments were performed over four weeks using non-invasive instrumental methods. The obtained results demonstrated improvements in skin hydration, elasticity, firmness, and skin barrier function, together with reductions in transepidermal water loss and erythema. The evaluation of skin textural parameters revealed improvements in skin uniformity and a reduction in the appearance of wrinkles. Among the tested structured systems, F3 formulation exhibited the most pronounced moisturizing effect, while F1 formulation showed notable improvements in parameters associated with skin texture and wrinkle-related features. Conclusions: Overall, the results indicate that honey-based topical systems enriched with essential and vegetable oils represent promising multifunctional semisolid formulations for topical skin-conditioning and barrier-supportive applications. Their favorable rheological behavior, combined with beneficial effects on skin hydration, barrier function, and skin surface properties, supports their potential use in skin-conditioning and anti-aging-related formulations. Full article

Air-assist atomization exploits high-velocity gas streams to shear liquid phases, achieving fine droplets at supply pressures significantly lower than those required by conventional pressure atomization. This technology is extensively deployed across diverse sectors, including pesticide spraying, food spray drying, sanitization/disinfection, and combustion atomization. Although specific operational fields dictate vastly contrasting droplet size distributions, velocities, and deposition uniformities—with target diameters spanning from <50 μm to >200 μm—their foundational atomization mechanisms remain inherently unified, governed primarily by toroidal vortex-induced primary breakup and Kelvin–Helmholtz/Rayleigh–Taylor (KH–RT) or Taylor Analogy Breakup (TAB) secondary breakup. This review systematically parses the atomization mechanisms, critical performance metrics, numerical simulation frameworks, and experimental characterization methodologies of air-assist nozzles. Crucially, from a novel “cross-disciplinary custom design” perspective, we contrast the optimal droplet parameter windows across the agricultural, food, sanitization, and combustion sectors (e.g., electrostatic plant protection yields a 203–1350% increase in abaxial leaf deposition; mine wind-assisted misting achieves a >90% collection efficiency for PM₁₀ dust; and SCR air-assisted injectors reduce the Sauter Mean Diameter (SMD) to 25 μm). Synthesized insights reveal that segmented VOF-to-DPM transition frameworks, corner-vortex-induced breakup theories, and closed-loop adaptive control architectures possess substantial cross-domain migration value. Current bottleneck challenges are highlighted, including the mesh dependency of droplet collision–coalescence models in dense spray regimes, the absence of robust atomization constitutive formulations for non-Newtonian fluids, and the ongoing paradigm shift from open-loop presetting to intelligent closed-loop regulation. This work establishes a comprehensive theoretical foundation and technical roadmap for cross-disciplinary integration and next-generation smart nozzle design in air-assist atomization. Full article

This study investigates the nonlinear rheological effects on debris flow dynamics within multi-stage energy dissipation systems. Addressing the limitations of the constant-viscosity Bingham model under high-shear conditions, we developed a 2D multiphysics model combining stepped spillways and a regulation basin using the Phase-Field method. We systematically compared the Bingham model against the Herschel–Bulkley–Papanastasiou (HBP) model across various flow behavior indices. Results reveal three key mechanisms: (1) In rapid stepped-drop zones, the HBP model captures shear-thinning behaviors, correcting Bingham’s velocity prediction biases. (2) In bottom gentle zones, deceleration in moderate-to-strong pseudoplastic fluids triggers a “low-shear to high-viscosity” positive feedback, spontaneously forming a high-stiffness unyielded cushion that enhances energy dissipation. (3) Shear-thinning behavior significantly reduces the macroscopic viscosity of the fluid near structural boundaries. This apparent viscosity reduction causes the debris flow to generate dense and high-frequency transient impacts upon initial contact with the retaining wall. The traditional Bingham model often severely underestimates this critical initial destructive force. This research elucidates non-Newtonian phase-transition laws under cascading topographies, providing a robust theoretical basis for designing impact-resistant disaster mitigation structures. Full article

To investigate the rheological properties of geopolymer grouting materials, a systematic study was conducted on a slag–red mud–fly ash ternary solid waste geopolymer grouting material (TSWGGM). The effects of liquid-to-solid ratio (0.5–1.5), slurry temperature (10–50 °C), and alkali activator concentration (1.0–1.8 mol/L) on the rheological model, yield stress, time-dependent viscosity behavior, and thixotropy were examined. The results show that the liquid-to-solid ratio is the dominant factor determining the rheological model. With increasing liquid-to-solid ratio, the slurry exhibits Herschel–Bulkley (shear thinning), Bingham, and Newtonian fluid behaviors in sequence. The yield stress decreases significantly with increasing liquid-to-solid ratio and approaches zero at high liquid-to-solid ratios (≥1.0), while it increases with rising temperature. In the temperature range of 20–30 °C, the time-dependent viscosity curves follow an exponential growth law, whereas at 40–50 °C, competition between early reaction and shear destruction leads to an initial decrease followed by an increase in viscosity. At low alkali activator concentrations (≤1.4 mol/L), the time-dependent viscosity curves still obey the exponential model, but at excessively high concentrations (≥1.6 mol/L) a non-monotonic change (an initial increase followed by a decrease, and final steady growth) occurs. The thixotropic loop area decreases with increasing liquid-to-solid ratio, first decreases and then increases with rising temperature, and exhibits a critical phenomenon of first increasing and then decreasing with increasing alkali activator concentration. Full article

This study investigated the rheological, structural, barrier, mechanical, optical, and thermal properties of composite edible films based on citrus pectin and vegetable purées derived from broccoli, cauliflower, pumpkin, carrot, and their blends. Film-forming formulations were characterized in terms of rheological behavior, thickness, microstructure, gas and water vapor permeability, optical and mechanical properties, water contact angle, and thermal stability. The incorporation of vegetable purées significantly modified the properties of the pectin-based matrices. All film-forming solutions exhibited non-Newtonian shear-thinning behavior, with flow behavior index values below unity. The addition of vegetable purées markedly increased viscosity and flow resistance, indicating the formation of more structured systems with stronger intermolecular interactions. Apparent viscosity increased from 0.19 Pa·s in the control sample to 1.41 Pa·s and 1.19 Pa·s in the broccoli (B) and broccoli–cauliflower (B-CF) formulations, respectively, while the consistency coefficient increased from 0.29 to 51.38 Pa·sⁿ. Composite films exhibited lower water contents (0.090–0.114 gH₂O·g_d.m.⁻¹) than the control film (0.179 gH₂O·g_d.m.⁻¹) and were thicker (170–282 μm) than the pure pectin film (125 μm). Barrier analysis revealed a reduction in water vapor permeability from 18.99·10⁻¹⁰ to 10.74–14.69·10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹ and a decrease in carbon dioxide permeability from 21.95 to 10.47–17.91 GRT. The carrot-containing film exhibited the highest tensile strength (62.17 MPa), whereas the pumpkin–carrot film demonstrated the most favorable combination of barrier and mechanical properties, including the lowest oxygen permeability (6.95 GRT), low water vapor permeability (10.74·10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹), and high tensile strength (51.02 MPa). Thermogravimetric analysis revealed similar three-stage degradation profiles for all samples, while vegetable incorporation modified moisture release and increased residual mass. The obtained results confirmed the research hypothesis that vegetable-processing by-products can serve as valuable structure-forming components of pectin-based composite films and that interactions between vegetable-derived biopolymers and citrus pectin improve the mechanical, barrier, and functional properties of the resulting materials. Among the tested formulations, the pumpkin–carrot film demonstrated the greatest potential for further development as a biodegradable packaging material. The utilization of vegetable by-products in pectin-based films represents a sustainable approach supporting circular economy principles and the development of environmentally friendly packaging systems. Full article

Background: Iodine-based antimicrobial systems remain highly attractive due to their broad-spectrum activity; however, the clinical application of free iodine is limited by its instability and cytotoxicity. This study aimed to develop polyethylene glycol (PEG)-based hydrophilic ointment formulations containing a dextrin/polyvinyl alcohol/iodine complex (D/PVA/I) and to evaluate their physicochemical properties, antimicrobial activity, and cytotoxicity. Methods: Hydrophilic ointment formulations containing 2.5%, 5.0%, and 10.0% D/PVA/I were prepared using a PEG-based matrix composed of PEG 4000, PEG 400, and glycerol. Physicochemical characterization included organoleptic evaluation, pH measurement, rheological analysis, and UV–visible (Ultraviolet–visible) spectroscopy. Antimicrobial activity was assessed using agar diffusion and minimum bactericidal concentration (MBC) assays against Staphylococcus aureus, Escherichia coli, Enterococcus hirae, and Pseudomonas aeruginosa. Cytotoxicity was evaluated in Madin–Darby Canine Kidney (MDCK) cells using the MTT assay. Results: All formulations exhibited homogeneous semisolid structure and physiologically acceptable pH values (4.94–5.45). Rheological analysis demonstrated non-Newtonian pseudoplastic (shear-thinning) behavior. The flow behavior index (n) ranged from 0.03 to 0.33 according to the Ostwald–de Waele model, confirming shear-thinning characteristics, while viscosity increased with increasing D/PVA/I concentration. UV–visible spectroscopy confirmed the presence of triiodide ions (I_3⁻), characterized by absorption maxima at approximately 287 and 350 nm, indicating preservation of active iodine species within the PEG matrix, while placebo (blank) formulation analysis confirmed the absence of corresponding absorption bands, demonstrating that the PEG-based matrix does not contribute to the characteristic spectral features. The formulations demonstrated broad-spectrum antimicrobial activity, with MBC values ranging from 0.01 to 0.02 µg/mL. Cytotoxicity studies revealed moderate toxicity of the D/PVA/I complex (CC₅₀ = 0.82%) (50% cytotoxic concentration (CC₅₀) and significantly lower toxicity of the PEG-based ointment base (CC₅₀ = 18.38%). Conclusions: The developed PEG-based hydrophilic ointment formulations containing the D/PVA/I complex demonstrated favorable physicochemical characteristics, stability of iodine species, pronounced antimicrobial activity, and acceptable cytotoxicity profiles. These findings highlight the potential for the developed systems to be promising topical antimicrobial formulations. Full article

Sixteen functional vegetable oils were incorporated at a 20% substitution level into a standard mayonnaise formulation to assess the impact of fatty acid composition on physicochemical, textural, rheological, and microstructural properties. Color analysis revealed substantial variation in yellowness (b* = 11.37–30.08) and lightness (L* = 74.39–82.31), while pH remained unaffected across all formulations (3.3–3.6). Texture analysis demonstrated that PUFA-rich oils, particularly linseed, thistle, and corn, produced markedly lower consistency values (17.02–18.68 N·s) compared to MUFA-rich counterparts (up to 69.95 N·s), indicating weaker interfacial network organization. All formulations exhibited non-Newtonian shear-thinning behavior described by the power law model (K = 90.12–130.63 Pa·sⁿ; n = 0.162–0.249). Low-field NMR relaxometry identified three distinct proton populations reflecting differences in proton mobility, while diffusometry revealed mean droplet radii ranging from 2.653 µm (pomegranate oil) to 3.203 µm (linseed oil). Pearson correlation and principal component analysis (PCA) confirmed fatty acid unsaturation as the primary driver of droplet size distribution and textural differentiation among formulations. The study was designed as an exploratory screening of single-batch formulations, and the results are presented descriptively to identify comparative trends among the different oils. Linseed, walnut, and pomegranate oils showed favorable compositional profiles for mayonnaise reformulation, combining favorable PUFA-to-SFA ratios with acceptable emulsion stability and rheological performance. Full article

Effective hand washing takes time and hand sanitizers that contain alcohol have a number of drawbacks, and frequent use of alcohol may cause skin damage. The objective of this study is to formulate nanostructured lipid carrier systems containing chlorhexidine digluconate to be applied topically for hand hygiene, especially for people sensitive to alcohol. A cytotoxicity experiment was conducted to ascertain the safe dosage for each of the three nano-cream formulas (F1, F2 and F3). Following each treatment, the viral titer was assessed using tissue culture infectious dose₅₀ and standard plaque assays. The selected formulation was characterized rheologically. Furthermore, fifteen volunteers of various ages and genders participated in the vivo antimicrobial test of the selected formulation as a hand sanitizer. All of the formulas were found to be safe. Using the disc diffusion method, the three formulations exhibited in vitro antimicrobial effects against different microbes. F1 showed biphasic release, reasonable skin deposition and spherical droplets under a microscope. F1 exhibited a non-Newtonian shear thinning flow behavior. After 30 min, the reduction values for rotavirus and Phix-174 were 21 and 4%, respectively. Additionally, the impact of F1 was assessed on the infectivity of simian rotavirus sa-11 (ds RNA) and Phix-174 (ss DNA) bacteriophage. According to the findings of the in vivo study, the percentage of total bacterial counts that were removed varied from 91 to 100%. Moreover, the range of the removal percentage of total fungi was 95.38 to 100%. In summary, F1 can be used as an economic, safe, and effective hand antiseptic. It can also completely replace alcohol in the market. Full article

Nanomaterials such as cellulose nanocrystals and fumed silica are emerging as excellent thickeners for liquids in a variety of practical applications. Surfactants are often incorporated into the thickening fluids to provide stabilizing components and to control the surface activity of fluids. To develop new thickening materials with desired surface-active properties, it is important to understand the interactions between surfactants and nanoparticles in suspensions. In this work, the interactions between surfactants and nanocrystals/nanoparticles were investigated. Two surfactants, anionic sodium lauryl sulfate-based surfactant (referred to as Stepanol) and cationic hexadecyltrimethylammonium bromide (referred to as HTAB), were studied. Cellulose nanocrystals (referred to as NCC) and fumed-silica nanoparticles (referred to as N20) were used as nanomaterials. The unique feature of this study is that it simultaneously measures rheology, surface activity, and electrical conductivity to determine the influence of ionic surfactants on the behavior and properties of cellulose nanocrystal and fumed silica nanoparticle suspensions. Furthermore, the interactions are observed in the low surfactant concentration range of 0 to 500 ppm. The NCC concentration of NCC–surfactant mixtures was fixed at 1 wt%. Two concentrations of N20 (2 and 5 wt%) were used for N20–surfactant mixtures. The influence of Stepanol was found to be weak whereas HTAB had a strong influence on the rheology of NCC and N20 suspensions. The NCC suspension and surfactant–NCC suspensions were highly non-Newtonian shear-thinning. The N20 suspensions and N20-Stepanol mixtures were nearly Newtonian. The N20-HTAB mixtures were shear-thinning at high HTAB concentrations. The power law model described the rheological behavior of non-Newtonian systems adequately. The consistency and flow behavior indices varied only marginally with the addition of the anionic surfactant Stepanol to NCC and N20 suspensions. With the addition of cationic surfactant HTAB to NCC and N20 suspensions, however, a large increase (20- to 70-fold) in consistency index was observed at high surfactant concentrations. The critical surfactant concentrations where sharp transitions in the rheological properties took place were identified using break points in surface tension and electrical conductivity plots. This study offers valuable insights into tailoring surfactant–nanoparticle systems for practical applications, where precise control of rheological and interfacial properties may be required. Full article

Twin-blade planetary mixers are widely employed in the mixing of particle-laden non-Newtonian fluids. Their unique blade configuration makes accurate blade load distribution determination crucial for structural integrity and mixing efficiency. However, computational fluid dynamics (CFD) simulations are often prohibitively expensive, limiting their practical application. To address this, this study develops a reduced-order model (ROM) from CFD data to rapidly predict the blade load distribution of a 1 L twin-blade planetary mixer at key operational points. Flow field analysis shows blade pressure extremes arise from blade-to-blade and blade-to-wall interactions, with magnitudes determined by rotational and gyrational speeds; local shear extremes mainly stem from blade–wall interactions. Validation demonstrates the ROM achieves over 93% prediction accuracy in key regions covering over 30% of the dataset, cutting computational time from days (full CFD) to seconds. This model enables fast, accurate blade load prediction across varying speeds, providing a practical tool for blade design and real-time monitoring. Full article

This study investigates the influence of key operating parameters of fill factor, rotor speed, and rotor wear on the power consumption of an isothermal intermeshing internal mixer. A three-dimensional computational fluid dynamics (CFD) model incorporating dynamic remeshing was developed using the finite volume method to solve the continuity and momentum equations for non-Newtonian rubber flow. The dynamic remeshing approach enabled accurate tracking of the moving rotor geometry and maintained mesh quality under varying operating conditions. The model integrates the actual mixer geometry and rheological properties of the rubber, and was validated against plant-scale power consumption data, showing good agreement. Simulations were performed across a range of operating conditions to quantify the effects of each parameter. Results indicate that increasing the fill factor from 50% to 82% raises normalized power from 14–19 kW/% to 17–22 kW/%, with higher levels producing extensive shear stress coverage to the rotor barrels but at the cost of potential clogging and reduced energy efficiency. Increasing rotor speed from 35 to 60 rpm increases normalized power from 20–22 kW/rpm to 22–23 kW/rpm, as higher rotor speeds intensify the local shear stress and strain rate fields near the rotor tips, thereby increasing power consumption. Rotor wear was found to significantly influence power consumption, with increasing wear leading to a progressive reduction in energy demand. The results indicate that worn rotor conditions reduce mechanical energy transfer due to diminished rotor–material interaction and increased clearances, resulting in lower shear stress generation within the mixing chamber. These findings identify operational windows that minimize energy costs while maintaining effective wall shear stress, offering practical guidance for optimizing mixer performance. Full article

The rheology of dilute emulsions is reviewed comprehensively. The fundamental equations governing the flow fields inside and outside the droplets are discussed, along with the boundary conditions. The rheological constitutive law for dilute emulsions with pure interfaces characterized by interfacial tension is developed using the flow field external to the droplets. Both zero-order and first-order deformations of droplets are considered. Dilute emulsions exhibit non-Newtonian behavior. The influences of surface charge and surfactants on the emulsion rheology are covered in detail. The rheology of emulsions of double droplets and droplets covered with elastic membranes is covered as well. Finally, a significant section of the review is focused on the dynamic rheology of dilute emulsions. Emulsions with pure interfaces and additive-laden interfaces are considered. The theories developed for the dynamic rheology of emulsions consisting of different types of interfaces are reviewed, including purely viscous interfaces, purely elastic interfaces, viscoelastic interfaces, and interfaces possessing bending rigidity. In general, the theory for dilute emulsion rheology is well developed. Our current understanding of dilute emulsion rheology is good from a theoretical point of view. A priori predictions of dilute emulsion rheology are possible using the existing theories. However, serious gaps in the existing knowledge on dilute emulsion rheology remain. This review identifies the gaps in existing knowledge and points out future directions in research related to dilute emulsion rheology. Full article

This study investigates the factors influencing the performance characteristics of annular jet pumps (AJPs) conveying non-Newtonian fluids, to enhance their suction capability for marine organisms such as jellyfish, which exhibit properties close to non-Newtonian fluids. Based on the power-law fluid model, realizable k-ε model, and volume of fluid (VOF) model, shear-thinning carboxymethyl cellulose (CMC) was selected to simulate marine organisms like jellyfish. Fluent software was employed to numerically simulate the performance characteristics and internal flow field of the annular jet pumps. The results demonstrate that the shear-thinning effect of non-Newtonian fluids reduces the maximum efficiency point of annular jet pumps and decreases the flow rate ratio corresponding to this efficiency point. As the concentration of CMC solution increased to 0.5%, the maximum efficiency point decreased by 5.5%, and the flow rate ratio corresponding to this efficiency point dropped from 1 to 0.8. These findings provide reference and insights for analyzing the full flow field of annular jet pumps pumping shear-thinning non-Newtonian fluids and for structural design of such pumps. Full article