Search Results (816)

This study aims to develop a high-precision and efficient body-fitted mesh framework for fluid topology optimization, focusing on minimizing flow resistance in incompressible steady Newtonian fluid systems. Different from traditional fixed-mesh methods that suffer from blurred fluid–solid interfaces and numerical dispersion, the proposed work integrates adjoint-based sensitivity analysis, level-set interface evolution, and adaptive body-fitted mesh updating to realize an accurate boundary description and a balanced precision–efficiency performance. The key technologies of body-fitted meshes (initialization, adaptive updating, quality control, and numerical discretization) are elaborated on to form a complete optimization framework. Numerical verification using two classic benchmark problems shows that, compared to traditional non-body-fitted meshes, the proposed method accurately captures the fluid–solid interface, reduces the number of mesh elements by 40–60%, improves computational efficiency by over 30%, and balances numerical precision with cost. These results demonstrate that body-fitted meshing is a promising strategy for high-fidelity and efficient fluid topology optimization. Full article

The management of fine bauxite tailings, rich in clay minerals, represents an environmental and operational challenge for the aluminum industry. This study (Part 1) presents a pilot-scale investigation into the dewatering of these ultrafine tailings using a decanter centrifuge, 0.62 m in diameter, as an alternative to conventional wet storage. Tests were conducted at three bowl speeds, 1600 rpm, 1700 rpm, and 1800 rpm, corresponding to G-forces of 888, 1003, and 1124 G. The feed slurry behaved as a non-Newtonian, yield-pseudoplastic fluid, as confirmed by rheology tests. A comprehensive mass balance and performance analysis were conducted. The results demonstrated a monotonic improvement in key performance metrics with increasing bowl speed. Accordingly, increasing the G-force from 888 G to 1124 G improved the final cake solid content from 66.3% to 71.5% (by weight), together with an increase in the average solid recovery from 40.0% to 56.2%. Partition curve analysis revealed the primary limitation: while recovery of particles coarser than 20 µm was very high (>98%), recovery of particles finer than 20 µm remained low, ranging from 22.0% to 35.1%. Partition curve analysis using the Whiten model identified a mechanical cut size (d_50c) ranging from 9.72 µm to 12.0 µm. Hydraulic bypass increased from 8.35% to 14.9% with increasing bowl speed, indicating a significant non-size-selective component of separation. Rheological analysis further showed that the apparent viscosity at 100 s⁻¹ decreased from 0.332 to 0.111 Pa·s across the tested conditions, confirming enhanced slurry mobility and its contribution to increased ultrafine bypass. While overall solid recovery reached 56.2% at 1124 G, the mechanical capture of the ultrafine fraction (<5 µm) remains the primary bottleneck for industrial viability. It is concluded that while the decanter centrifuge is mechanically viable for producing a high-solid cake, the limited recovery of fines would create an unsustainable circulating load in an industrial plant. These results demonstrate that G-force alone, within the tested range, is insufficient to manage these tailings and provide the basis for the mathematical modeling required to design the process, as described in Part 2 of this investigation. 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 paper introduces a topology optimization framework for steady incompressible Stokes flow based on the non-conforming Virtual Element Method, VEM. The proposed framework combines the geometric flexibility of VEM with an optimality criteria update scheme to minimize viscous and Darcy dissipation under a prescribed volume constraint. The method is applied to the Stokes-flow pipe bend benchmark with parabolic inlet velocity, no-slip wall, and prescribed outlet velocity boundary conditions. By allowing general polygonal elements, including concave and semi-structured polygonal meshes, the method alleviates mesh-related restrictions commonly encountered in conventional finite element discretizations. The methodology is demonstrated through Stokes-flow benchmark problems on different polygonal meshes. The numerical results show that the proposed VEM-based formulation can obtain stable and mesh-insensitive optimized flow channels for Stokes-flow topology optimization. This work offers a systematic approach to obtaining accurate, efficient, and mesh-independent optimal designs for complex fluid systems, providing a stable numerical tool for low-energy-consumption flow channel design in microfluidics, heat exchangers, and biomedical engineering. Extensions to Navier–Stokes and non-Newtonian flow models are left for future work. It should be clarified that the proposed method is only validated for steady Stokes flow and has not been validated for complex fluid models including unsteady Navier–Stokes and non-Newtonian flow models; extensions to these complex models are left for future work. Full article

Real-Time In-Line Monitoring (RTIM) of rheological properties such as slurry yield stress is important in different industries for its various benefits such as significant time savings and increased safety/efficiency of processes while reducing secondary waste due to sampling or inaccurate procedures. This paper discusses two methods for characterizing yield stress in real time: the Pressure Loss method and the Liquid Rise method. The Liquid Rise method uses the height of the slurry in a vertical column and the pressure difference to quantify the yield stress. The Pressure Loss method uses the drop of pressure in a laminar flow of slurry to determine the yield stress. Kaolin–water slurry is used as a simulant of the non-Newtonian fluid. An experimental setup is built to demonstrate the methods, and data obtained from the experimental setup is compared with the yield stress obtained from a conventional table-top rheometer (baseline rheology). The results show a good agreement between the experimental yield stress and baseline rheology. Full article

The present study provides a comprehensive investigation into the hydrodynamic performance of grooved rubber journal bearings (GRJBs) employed as shaft supports in various rotating systems, with particular emphasis on marine applications. These bearings are lubricated with non-Newtonian fluids such as modern oil containing additives and viscoelastic water-based lubricant, which—owing to its complex composition including hydrocarbon chains, metal oxides, and impurity particles and contaminants such as salts, organic substances, microalgae, biopolymers, and microorganisms—deviates from the ideal Newtonian fluid model and demonstrates non-Newtonian rheological behavior. By examining various theories used in the analysis of non-Newtonian fluid behavior, the power-law model, which has a high degree of generality, has been employed in the present study. Also, to improve modeling accuracy, the elastic deformation of the rubber bush in this study is characterized using the Winkler foundation approach and analyzed via the finite element method (FEM). This advanced mechanical formulation, integrated with non-Newtonian lubrication modeling of lubricant using the power-law fluid model, and the parametric assessment of groove number and dimensions on steady-state bearing performance parameters, constitutes the core of this research. The investigation focuses on groove configurations of 4, 6, 8, and 10 channels. The findings indicate that increasing the groove count partitions the convergent pressure film zone into discrete segments, thereby reducing the maximum hydrodynamic pressure while intensifying the overall energy dissipation within the bearing. Additionally, the influences of rheological properties of the fluid—namely the power-law index (n) and the consistency index (m)—on key performance characteristics are thoroughly examined. An increase in both parameters enhances the effective viscosity and load carrying capacity; however, the exponential amplification due to the power-law index exhibits a more pronounced effect on load capacity and peak pressure compared to the consistency index. Full article

Bubble bursting at liquid surfaces was investigated experimentally using high-speed imaging at 25,000 fps and micro-particle image velocimetry (µ-PIV) at up to 4000 flow fields per second. Three fluids with distinct rheological properties were studied: a viscous Newtonian fluid (Emkarox, η₀ = 0.072 Pa·s) and two non-Newtonian fluids (highly viscous Carboxymethyl Cellulose, HV CMC, η₀ = 0.53 Pa·s, and viscoelastic Polyacrylamide, PAAm, η₀ = 57.17 Pa·s). Bubble radii ranged from 1.2 to 4.0 mm, with corresponding lifetimes spanning from O(10⁻²) to O(10¹) s depending on fluid properties. The relationship between bubble size and lifetime at the air–liquid interface was quantified for the non-Newtonian fluids, using the Newtonian fluid as a reference. µ-PIV measurements further captured the rapid dynamics of bubble bursting beneath the interface in the liquids. These findings provide new insight into the complex interfacial mechanisms governing bubble rupture and fluid motion. 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

In this study, we introduce a novel method for microscale viscosity measurement that eliminates the need for direct contact angle determination. By utilizing a capillary with a sufficiently small radius (R < 0.2 mm), the sharp outlet edge pins the three-phase contact line, stabilizing the apparent contact angle near 90° and nullifying the capillary pressure term. The rheological parameters (K and n) of power-law fluids are then calculated directly by analyzing image sequences of a growing pendant droplet to obtain its volume flow rate Q. Experiments verify through inversion calculation that the apparent contact angle indeed converges to 90° at a small capillary radius. The proposed method is employed to measure 20 wt% and 40 wt% glycerol aqueous solutions (Newtonian fluids) as well as 0.01 wt% and 0.02 wt% xanthan gum aqueous solutions (non-Newtonian fluids). The obtained rheological parameters agree well with reference values within this range, confirming the method’s reliability for these low-viscosity and moderately non-Newtonian fluids. However, measurements on higher concentration fluids (e.g., 0.1 wt% and 0.2 wt% xanthan gum solutions) reveal increased errors, indicating a current limitation in accurately characterizing fluids with high viscosity or pronounced non-Newtonian behavior under gravity-driven flow. This simple technique provides a reliable and low-cost approach for measuring the viscosity of microliter-volume fluids within its characterized operational range. 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

Superhydrophobic fiber films, as a typical superhydrophobic material, have advantages such as self-cleaning, non-wettability, and pollution resistance. They can be widely used in oil-water separation, antibacterial, anti-pollution, anti-icing, and self-cleaning fields. Traditional electrospun superhydrophobic fiber films face difficulties in fabricating fibers with large contact angles due to the non-Newtonian fluid flow and Taylor cone jet trajectory limitations. To address this challenge, this study develops a novel ultrasonic-magnetic field coupling electrospinning strategy for fabricating poly(methyl methacrylate)-polystyrene (PMMA-PS) fibrous films with enhanced superhydrophobicity. Physical, chemical, and contact angle measurements were used to analyze the morphology, composition, and hydrophobic properties of the fabricated films. The results showed that by controlling the blend ratio of PMMA and PS and optimizing the electrospinning process with ultrasonic vibration and magnetic field coupling, PMMA-PS fibers with better fiber refinement, closer spindle-shaped arrangements, and significantly increased roughness were successfully fabricated. When using 15% PMMA and 15% PS solutions, the static contact angle of the resulting fiber films reached 173.1°, demonstrating the best superhydrophobicity. The study suggests that optimizing the surface morphology of the nanofibers is an effective method to improve hydrophobicity and provides a new approach for fabricating superhydrophobic fiber films. Full article

High-value metabolites, such as antibiotics and enzymes, are primarily produced using filamentous fungi. However, their morphological complexity increases broth viscosity during biomass growth, hindering industrial scale-up by impairing both power input and mass transfer. The interaction between biomass growth, rheology, power input, and oxygen transfer is first addressed here by evaluating mycelial rheology and determining the volumetric mass transfer coefficient (k_La) (dynamic method) and oxygen uptake rate (respirometry) across different operating conditions. These confirmed that the mycelial broth’s pseudoplastic behavior significantly influences volumetric power input and k_La correlations. However, specific power input analysis revealed that operating at higher stirring rates (800 rpm) at higher cell-density cultures is 28.17% more energetically efficient than at low speeds (500 rpm). Furthermore, the oxygen supply-to-demand ratio, calculated via Excel model-fitting, allowed for the estimation of “metabolic power input” which represents the required energy to fit oxygen demand. Results also reveal that at 3.67 ± 0.34 g L⁻¹ of biomass effectively channel up to 51% of total energy toward aerobic metabolism, compared to only 17–30% for 0.73 ± 0.01 g L⁻¹ of biomass. These findings show that volumetric power inputs around 4 kW m⁻³ improve oxygen transfer efficiency, even at relatively high biomass concentrations. Full article

The quasi-steady low-Reynolds-number flow induced by a linear chain of multiple slip spheres translating along their common axis in a Newtonian fluid is investigated. The particles are allowed to differ in radius, Navier slip coefficient, migration velocity, and interparticle spacing. A semi-analytical solution of the governing Stokes equation is obtained using a boundary collocation method. Hydrodynamic interactions among the particles are shown to be significant under appropriate geometric and surface conditions. For the two-sphere configuration, the computed hydrodynamic forces agree closely with previously published asymptotic solutions derived via the twin multipole expansion method. In the three-sphere case, the presence of a third particle substantially modifies the forces acting on the other two, demonstrating non-negligible many-body interaction effects. The interaction strength is found to be more pronounced for smaller particles or those with lower slip coefficients. Calculations for longer particle chains further reveal a clear hydrodynamic shielding effect within the assembly. Full article

The physical characteristics of a heated non-Newtonian Eyring–Powell fluid in a conduit with sinusoidally moving ciliated walls are highlighted in this analytical study. The impact of mass transmission is considered in this model. The dimensional form of the governing equations is simplified using the long-wavelength estimation and suitable transformations to produce a set of dimensionless partial differential equations with pertinent boundary conditions. To solve it, the perturbation technique is utilized applying polynomial solutions. The solutions of temperature, concentrations, and velocity profiles are obtained, and then are further analyzed through graphical results. An accurate mathematical solution for the pressure gradient is achieved by integrating the velocity profile over the elliptic cross-section. The non-Newtonian Eyring–Powell fluid flows quicker through this vertical ciliated elliptic duct than the Newtonian fluid. Moreover, the cilia elliptic movement eccentricity and the wave number for metachronal wave have a dual effect on the velocity profile. Increasing the dimensionless flow rate and occlusion leads to an increase in closed contour size, as seen in the streamline description. Full article

Non-Newtonian weighted fracturing fluids are used to carry out hydraulic fracturing operations into the deep and ultra-deep earth for oil and gas extraction, though their flow and friction drag characteristics are largely unknown. This study aims to understand the abovementioned characteristics. An engineering-oriented cost-effective numerical scheme is deployed, incorporating LES with a generalized Newtonian fluid constitutive equation, for predicting the non-Newtonian pipe flow and friction drag coefficient C_f. The weighted fracturing fluid is described as a power-law fluid, i.e., viscosity $\mu \left(\dot{\gamma }\right)=K{\dot{\gamma }}^{n-1}$, where both K and n are coefficients related to fluid rheology, and $\dot{\gamma }$ is the shear rate. The influences of fluid density ρ, mean velocity U and pipe diameter D, as well as K and n on C_f were documented and compared with a water pipe flow. It was found that C_f = f₁ (K, n, ρ, U, D) may be reduced to C_f = f₂ (Re_g), where the scaling factor Re_g = ρU²⁻ⁿDⁿ/(K8ⁿ⁻¹) is the generalized Reynolds number. This scaling law can reasonably well predict the friction drag variation in the pipe flow of non-Newtonian weighted fracturing fluids throughout a range of interests and engineering applications. Full article