Bubble rising dynamics in a transverse ultrasonic standing wave field: Role of acoustic-induced viscous dissipation.

This study provides a comprehensive comparative analysis of hybrid nanofluid flow and heat–mass transfer in a rotating rectangular system by incorporating velocity, thermal, and concentration slip conditions together with viscous dissipation and activation energy effects. The physical configuration consists of a fixed upper plate and a permeable, stretchable lower plate subjected to a uniform magnetic field and thermal radiation. Two hybrid nanofluid formulations, Cu/Ag –water and CuO/TiO 2 –water, are employed to examine the influence of distinct thermophysical properties on transport phenomena. The governing nonlinear partial differential equations are transformed into a system of ordinary differential equations via similarity transformations and numerically solved using MATLAB’s boundary value problem solver with a specified accuracy of 10 -6 . A detailed parametric study is carried out to assess the influence of Reynolds number, thermophoresis, Brownian motion, radiation, Eckert number, activation energy, Schmidt number, and slip parameters on the velocity, temperature, and concentration distributions. The results reveal that thermophoresis enhances mass diffusion while reducing the temperature gradient, whereas viscous dissipation notably elevates the thermal field. Activation energy significantly strengthens concentration boundary layers, and slip conditions reduce wall resistance, thereby modifying both heat and mass transfer rates. Thermal radiation increases the Nusselt number but decreases the Sherwood number for both hybrid nanofluids. Overall, the CuO/TiO 2 –water hybrid nanofluid exhibits superior thermal performance, whereas Cu/Ag –water shows enhanced mass transfer characteristics. • Comparative study of hybrid nanofluids in a rotating rectangular system. • Slip effects, viscous dissipation, and activation energy are incorporated. • Cu/Ag–water and CuO/TiO 2 –water hybrid nanofluid formulations are examined. • Magnetic field and thermal radiation are applied to permeable stretchable plate. • ODE system are solved numerically via similarity transforms using MATLAB BVP solver.

The coffee-ring effect (CRE) remains a major obstacle to achieving uniform functional deposits in high-resolution printed electronics, particularly for picoliter-scale droplets where evaporation dynamics are complex and poorly understood. This study demonstrates that precise control of substrate temperature is a highly effective strategy for suppressing the CRE in inkjet-printed picoliter droplets of a commercial silver nanoparticle ink. We identify a distinct morphological transition: uniform deposits form at low temperatures (20-40°C), pronounced coffee-rings develop at intermediate temperatures (50-70°C), and central accumulation emerges at high temperatures (>90°C). Through a combination of experimental analysis, scaling arguments, and numerical simulations, we systematically rule out Marangoni flows and viscous dissipation as the primary suppression mechanisms at low temperatures. Instead, we show that the extended drying time at low substrate temperatures drastically reduces the Péclet number, shifting the dominant transport mechanism from outward capillary advection to inward particle diffusion. This diffusion-driven homogenization ensures uniform particle redistribution prior to immobilization. Our findings provide a robust, practical, and readily applicable thermal strategy for eliminating capillary-driven inhomogeneities, paving the way toward the reliable fabrication of high-resolution printed electronic devices with superior morphological and functional uniformity.

Viscous energy dissipation on hemolysis across various flow regimes using a high-shear device

This paper presents a comprehensive analysis of magnetohydrodynamic (MHD) flow, radiative heat transfer, and mass transport in nanofluids interacting with an incompressible, electrically conducting fluid. The study accounts for the combined effects of Joule heating, viscous dissipation, and a first-order chemical reaction over a porous plate embedded in a porous medium subjected to a prescribed heat flux. A numerical investigation is performed on the boundary-layer flow model involving three distinct nanoparticle types Cu , A l 2 O 3 and Ag . The governing equations for momentum, energy, and species concentration are formulated under the boundary-layer approximation. By employing similarity transformations, the coupled nonlinear partial differential equations with associated boundary conditions are reduced to a system of ordinary differential equations (ODEs) defined over a semi-infinite domain. This system is solved numerically using a hybrid scheme that integrates the Shooting technique with the fourth-order Adams–Moulton method. The accuracy of the results is confirmed through comparison with previously published data, demonstrating excellent agreement. The effects of key physical parameters on the velocity, temperature, and concentration fields are examined and illustrated through graphical and tabular analyses. Furthermore, thermophysical property correlations are provided. The findings indicate that an increase in nanoparticle volume fraction leads to elevated temperature profiles, thereby enhancing the Schmidt number. Thus, the results provide a clear understanding of fluid flow behaviour in applications such as nuclear reactor cooling systems, polymer extrusion processes, and electromagnetic magnetohydrodynamic generators.

Supercritical CO 2 (SCO 2 ) centrifugal compressors are pivotal components in next-generation high-efficiency power cycles (e.g., Brayton cycles), enabling greater than 50% thermal efficiency and compact power block designs essential for sustainable energy systems. This study addresses a critical reliability challenge by optimizing dry gas seal (DGS) groove designs for these compressors. Using validated 3D CFD simulations, incorporating k-ω SST turbulence model and Redlich-Kwong real gas equation of state, the performance of four industrial groove geometries (spiral, oval, fish-tail, and tree-type) are evaluated. Results demonstrate that the tree groove minimizes leakage (29.7% reduction vs. spiral) through tortuous flow paths, directly supporting emissions control and operational economy in power cycles. Conversely, spiral grooves maximize opening force and gas film stiffness (6.2% higher stiffness vs. tree), ensuring stable non-contact operation crucial for compressor reliability at extreme pressures. Oval and fish-tail grooves offer intermediate trade-offs. Thermal analysis reveals considerable localized high temperature zones due to viscous dissipation and adiabatic compression, a key consideration for material longevity. This work establishes that groove selection fundamentally balances leakage rate (optimized by tree grooves) against hydrodynamic stability (maximized by spiral grooves). These findings provide practical guidelines for enhancing DGS performance in SCO 2 compressors, directly contributing to the viability of high-efficiency, low-emission power generation.

ABSTRACT The scale‐up of twin‐screw extrusion for energetic materials is challenging due to their sensitivity to heat and shear. Conventional methods often fail to simultaneously ensure process safety and mixing uniformity. This study proposes a novel Volume–Geometry–Shear rate (VGS) coordinated similarity scale‐up method to achieve equivalent safety and mixing performance. Based on a validated φ20 mm benchmark extruder (5 kg/h), safety boundaries were defined via coupled 3D Polyflow and 1D Ludovic simulations. The VGS framework integrates volumetric similarity for throughput, geometric similarity for flow structure, and constant average shear rate for material integrity. When used to design a φ50 mm industrial extruder (30 kg/h), the method greatly improved safety by lowering the maximum pressure, shear stress, and viscous dissipation by 18.9%, 58.2%, and 95.93%, respectively. Meanwhile, mixing performance was preserved with a negligible deviation of < 0.6% in the overall mixing coefficient. The VGS methodology provides a robust, generalizable framework for the safe and efficient industrial scale up of energetic material extrusion.

Enhancing the heat and mass transfer performance of working fluids remains a critical challenge to pursue sustainable and energy-efficient technologies. Although regular working fluids have superior thermo-physical properties to pure base fluids, they often face limitations that hinder their adoption in multifunctional applications. To overcome these challenges, this study develops a novel, comprehensive and physically consistent mathematical model for an unsteady, electrically conducting ternary hybrid nanofluid composed of graphene oxide (GO), cerium oxide (CeO[Formula: see text], and hexagonal boron nitride ([Formula: see text]-BN) suspended in an environmentally friendly ionic liquid (Ethyl-3-methylimidazolium tetrafluoroborate) [EMIM][BF 4 ]. The model integrates magnetic effects, radiation heat transfer, viscous dissipation, Joule heating, and coupled thermo-diffusion effects. A fractal–fractional derivative operator is employed to generalize the governing equations, while the local radial basis functions (RBF) scheme is used to solve them numerically. Computational and graphical results reveal that CeO 2 suppresses the fluid velocity due to increased inertial resistance, while the dispersion of [Formula: see text]-BN significantly enhanced the thermal profile, resulting in a higher Nusselt number. Furthermore, higher values of Dufour and Soret numbers enhance the coupled heat and mass transfer rates, indicating the model’s potential to design advanced heat exchangers and smart cooling devices. These findings provide valuable guidelines for designing compact heat exchangers and thermal energy storage systems for applications in renewable energy and microelectronics cooling.

This study undertakes a detailed examination of steady, two-dimensional boundary layer flow of a tangent hyperbolic nanofluid past a stretching sheet embedded within a porous medium, subjected to the action of a transverse magnetic field. The mathematical formulation accounts for the effects of velocity slip, viscous dissipation, Joule (Ohmic) heating, first-order homogeneous chemical reactions and wall heat transfer governed by Newtonian convective cooling. Furthermore, the thermodynamic irreversibilities resulting from fluid friction, heat transport and magnetic field effects are evaluated by entropy production and Bejan number analyses. While previous studies have examined Newtonian and conventional non-Newtonian nanofluid flows, the combined influence of electromagnetic forces, non-Newtonian rheology, slip mechanisms, reactive transport, convective thermal conditions and thermodynamic irreversibility for tangent hyperbolic nanofluids remains largely unexplored—a gap addressed in this work. The governing partial differential equations are reduced to a system of ordinary differential equations through similarity transformations and solved numerically using both the three-stage Lobatto IIIa collocation scheme ( bvp4c in MATLAB) and the shooting method with a classical fourth-order Runge–Kutta algorithm. The findings reveal that higher Eckert number ( Ec ) values lead to a substantial reduction in the Nusselt number by 18.3%–53% due to intensified viscous dissipation, but cause a moderate increase in the Sherwood number by 0.5%–1.5%. From the thermodynamic perspective, entropy generation increases with increasing Eckert number and Joule heating parameter and rises with higher chemical reaction parameter and Biot number as well. These patterns offer helpful recommendations for reducing losses and improving thermal efficiency in procedures including biofluid transport and polymer extrusion.

Airframe noise generated at wing trailing edges and high-lift devices, such as flaps, remains a major challenge during landing, with significant contributions in the low-frequency band of 500-1500 Hz. While solid surfaces reflect this acoustic energy, metallic porous materials can effectively absorb it through viscous and thermal dissipation within their internal pore structure. To address this, the present study examines the acoustic absorption characteristics of open-cell AlSi porous cylinders featuring controlled pore diameters between 0.3 mm and 2.25 mm. Measurements were conducted in an acoustic impedance tube according to the ISO 10534-2:2023 standard, using six cylindrical samples (28 mm diameter, 70 mm length). Two sets of measurements were performed for each sample (front and rear faces), and the average values were used. The findings indicate that the normal-incidence sound absorption coefficient α rises as pore size increases, reaching 0.93-0.97 at low frequencies of 500-700 Hz for the samples with the largest pores (1.8-2.25 mm). These results indicate that open-cell AlSi alloys offer strong low-frequencies sound absorption, positioning them as promising options for aeroacoustic noise mitigation, including applications such as porous trailing edge and hybrid flap designs.

Abstract Hybrid nanoparticle additives have been widely recognized for enhancing the thermal transport capability of low-conductivity fuels; however, their interaction with particle-laden microstructure fluids under electromagnetic effects remains insufficiently understood. In this study, an unsteady, immiscible flow of a $$CuO - TiO_{2}$$ C u O - T i O 2 /Diesel B0 hybrid nanofluid and a micropolar dusty fluid are investigated within a horizontal channel subjected to a transverse magnetic field. The hybrid nanofluid layer enhances effective thermal conductivity, while the micropolar dusty fluid accounts for micro-rotational motion and particle fluid interactions commonly encountered in practical multiphase environments. The model incorporates Hall and ion-slip currents, viscous dissipation, Joule heating, and interfacial continuity of momentum and heat flux. The resulting nonlinear governing equations are solved numerically using the Modified Cubic B-Spline Differential Quadrature Method, which ensures high accuracy and smooth resolution of the coupled interfacial dynamics. The results reveal that magnetic damping significantly suppresses velocity, whereas Hall and ion-slip effects effectively weaken Lorentz resistance and enhance flow and heat transfer. The unsteady formulation further highlights the temporal development of velocity, temperature, and microrotation fields, offering insight into transient MHD control of layered multiphase systems. The findings are relevant to magnetically assisted thermal management and fuel-based energy transport applications involving hybrid nanofluids and particulate-laden media.

Dynamics of unsteady MHD pressure-driven non-isothermal radiative flow of Maxwell fluid with joule heating and viscous dissipation

Instability of Convective Jeffrey Fluid in a Porous Medium with Vertical Throughflow and Viscous Dissipation

With the rapid development of emerging nanoscale technologies, such as nanoprinting, the impact dynamics of nanodroplets have drawn increasing attention. Although impacts on curved surfaces frequently take place, the effect of curvature remains far from being understood. In this work, nanodroplet impacts on solid spheres are compressively investigated by molecular dynamics simulation, and two key feature parameters, including the maximum spreading factor and restitution coefficient, are focused on. For the maximum spreading factor, due to the dominant bulk viscous dissipation and interfacial slip, classical macroscale models no longer hold at the nanoscale. Nonetheless, it is intriguingly found that, even with curvature, the nanoscale flat-surface model can still predict to impacts on solid spheres, because curvature preserves the Hertz-like (low Weber number) and film-like (high Weber number) energy conversion mechanisms observed on flat surfaces. For the restitution coefficient ε (the ratio of bouncing velocity to initial velocity), the dissipation is identified as associated with redirecting horizontal motion into vertical motion during bouncing. With increasing curvature, the vertical kinetic energy gained during retraction increases while the horizontal component that requires redirected decreases, leading to reduced viscous dissipation. On this basis, a curvature-dependent scaling law for ε is derived, which can naturally reduce to a flat-surface model when the ratio of sphere to droplet diameter approaches infinity. The scaling law shows good agreement with not only data on spheres from both present and previous studies, but also points on flat surfaces in the literature, which provides insight into energy conversion mechanisms.

Deep learning framework for casson fluid flow: A PINN approach to heat and mass transfer with chemical reaction and viscous dissipation

Self-assembly of cellulose nanocrystals for splash suppression and enhanced pesticide delivery on hydrophobic surfaces.

This study develops a general three-dimensional homotopy boundary element method (HBEM) model for analyzing wave-induced hydrodynamic problems of marine structures. Artificial dissipative surfaces are introduced into fluid domains where wave energy dissipation is non-negligible. The mass flux across these surfaces remains continuous, while local head loss is assumed to occur on both sides of these surfaces. Quadratic (nonlinear) pressure loss conditions are imposed on these dissipative surfaces to equivalently represent the viscous dissipation effect. In solving the boundary value problem, the conventional boundary integral equation derived from the second Green's theorem is applied to the structure surfaces, whereas a hypersingular boundary integral equation is deduced for the dissipative surfaces. After discretizing all boundaries into a series of constant panels, an algebraic system is obtained from the two types of boundary integral equations. The application of quadratic pressure loss conditions renders this system nonlinear, which is solved using the homotopy analysis method. The proposed HBEM model is validated by considering the problems of fluid resonance in narrow gaps and wave resonance in moonpools. The calculated results are in excellent agreement with both analytical results in the literature and numerical results based on a direct iteration method. Moreover, with an appropriately calibrated dissipation coefficient, the calculated results of the free surface amplitude inside narrow gaps and moonpools agree well with published experimental measurements. The present HBEM model can offer a reliable and efficient computational tool for the hydrodynamic analysis of wave–structure interaction.

Construction of polymer micro-scale rheological model considering viscous dissipation heat based on online testing method

Response surface–based sensitivity optimization of heat transfer in magnetohydrodynamic bioconvective Casson nanofluid flow past a rotating disk with joule heating and viscous dissipation effects

This study aims to examine the behaviour of Williamson hybrid magneto-ferrofluid containing Fe 2 O 3 and Cu nanoparticles with blood as the base fluid. The flow passes over a stretchable sheet and includes the impacts of thermal radiation, Arrhenius activation energy, Soret, viscous dissipation and Joule heating. Using similarity transformations, the governing equations representing flow, heat and mass transfer phenomena are converted to a set of ordinary differential equations. These transformed equations are solved numerically using ‘bvp4c’ technique. The velocity profile is found to increase with a higher stretching parameter and also it interestingly increases with the introduction of magnetic field parameter. The temperature graph increases with an increase in nanoparticle percentage, stretching parameter, Williamson parameter and Eckert number. Further, addition of 1% Fe 2 O 3 and Cu nanoparticles enhanced the skin friction coefficient, Nusselt and Sherwood number by 8.20%, 4.60% and 0.26%, respectively. The numerical results demonstrate strong agreement with previously published work in limiting cases, confirming the reliability of the current model. The outcomes provide valuable insights into the behaviour of Williamson hybrid ferrofluid in engineering and thermal management applications.