Significance of Cattaneo-Christov heat flux and bioconvection in magnetized Jeffrey nanofluid inside an extendable cylinder: Advanced in cooling system

Comparative experimental study of flame–wall interaction for hydrogen and methane

This study numerically investigates steady boundary-layer flow, melting heat transfer, and bioconvection in a thixotropic nanofluid over a porous stretching surface. The model incorporates a transverse magnetic field, Darcy porous resistance, thermal radiation, heat generation/absorption, and a first-order chemical reaction. Nanoparticle transport is described using Buongiorno's formulation through Brownian diffusion and thermophoresis, and cross-diffusion effects (Soret and Dufour) are included. Using similarity transformations, the governing partial differential equations are reduced to a coupled set of nonlinear ordinary differential equations, which are solved with MATLAB's bvp4c solver. The results show that magnetic and porous resistance suppresses the velocity field, while melting enhances near-wall motion. Thermophoresis increases the thermal boundary-layer thickness, whereas stronger melting reduces temperature. Higher Schmidt number and stronger chemical reaction decrease nanoparticle concentration and increasing the bioconvection Lewis number reduces microorganism density. The findings provide parametric guidance for controlling momentum, heat, mass, and microorganism transport in porous-surface coating and thermal processing applications.

The study presents a detailed numerical analysis which explores the characteristics of Williamson nanofluids together with Micropolar and Maxwell nanofluids transfer heat and magnetic energy across surfaces that stretched, while bioconvection and double diffusion and activation energy and multi-slip boundary conditions exist. The complex rheological behavior emerges between these systems which operate at advanced levels in thermal management systems and bio-convective reactors and magnetically controlled energy devices. The authors Ytransformed the nonlinear boundary-layer equations which describe motion, microrotation, heat, mass and microorganism transport into similarity variables before they solved the system through the numerical technique Runge–Kutta–Fehlberg (RKF-45) method which they mutual through a shooting technique. The research results conducted an extensive parameter analysis to determine the behaviour of magnetic field intensity and slip coefficients and Brownian motion and thermophoresis and Lewis numbers and Schmidt numbers affect the system's transport behavior. The quantitative findings demonstrate that micropolar nanofluids produce a 35% increase in Nusselt number and a 20–29% rise in wall shear stress when magnetic forces operate compared to situations without slip. The rate of heat transmission of Williamson nanofluids and Maxwell nanofluids show a 21–32% increase while their mass transfer rates rise by about 18%. The experimental data shows multi-non-Newtonian nanofluids perform better than other fluids in thermal and solutal properties which positions them as top candidates for heat exchangers and bio-reactors and magneto-thermal energy systems.

This study numerically investigates magnetohydrodynamic mixed convection of a micropolar nanoencapsulated phase change material (NEPCM) suspension in a channel–cavity system representative of compact latent heat thermal energy storage units. The configuration includes an embedded cylindrical obstruction to regulate flow structure and thermal transport characteristics. A steady-state finite element framework is employed to solve the coupled momentum, microrotation, energy, and concentration equations under the combined influence of buoyancy forces, magnetic field, and thermal radiation. The objective is to evaluate the interacting roles of internal particle rotation, latent heat storage, and Lorentz force on double-diffusive transport within a confined geometry. In contrast to conventional Newtonian nanofluid models, the present formulation simultaneously incorporates micropolar dynamics and phase change behavior, enabling a more realistic representation of advanced thermal storage suspensions. The results show that a balanced convection regime ( R i varied from 0 to 2) yields the most favorable thermo-hydrodynamic performance near R i ≈ 1 , where the average Nusselt number increases by 9.49% compared to R i = 0 due to constructive coupling between forced and natural convection, whereas further buoyancy enhancement to R i = 2 deteriorates transport efficiency. Thermal radiation, when increased from R d = 1 to R d = 5 , enhances the average Nusselt number by 76.52% while reducing the pressure difference by 6.86%, intensifying internal heat diffusion while moderating pressure penalties. Increasing the micropolar parameter from Γ = 0 . 1 to Γ = 2 enhances heat transfer by 14.33% but raises drag by 34.19%, indicating a heat transfer-hydrodynamic trade-off. Additionally, aiding solutal buoyancy strengthens mass transfer, particularly at higher Lewis numbers. The coordinated adjustment of micropolar coupling, buoyancy ratio, radiation parameter, and geometric configuration is shown to enhance the effectiveness of NEPCM-based thermal energy storage systems within the investigated parameter ranges. • Optimal thermal storage performance occurs at Richardson number Ri ≈ 1. • Radiation enhances heat transfer by 76.5% while reducing pressure drop by 6.9%. • Micropolar effects boost heat transfer 14.3% but increase drag by 34.2%. • Magnetic field suppresses convection by 30%, offering a flow control mechanism. • Aiding solutal buoyancy critically optimizes phase change in NEPCM suspensions.

Artificial neural network for bioconvective Williamson nanofluid flow through a horizontal microchannel with waste discharge concentration

Purpose This study aims to present a numerical analysis of thermal and entropy analysis of unsteady magnetohydrodynamic bioconvective flow of a Carreau fluid over an oscillating plate with combined sinusoidal and cosinusoidal motions. The main objectives of this research are capturing phase-dependent flow responses through combined oscillations; providing a unified analysis of Carreau fluid MHD flow with motile microorganisms; and examining the relative contributions of thermal, solutal and bioconvective buoyancy forces to flow behavior. Design/methodology/approach An implicit Crank–Nicolson scheme has been used to solve the governing equations. Findings The authors found that near the wall, phase-dependent cosine oscillations impact the momentum enhancement by nearly 70% as compared to sine oscillations. The reduction in species transport has been observed due to the increment in the Lewis number and chemical reaction parameters. On the other hand, the Peclet and bioconvection Lewis number enhance the microorganism cluster due to this sharp concentration gradients are generated. The elasticity parameter Weissenberg number We reduces the heat transfer rate by about 8% and flow resistance by 14% in shear-thinning fluids, on the other hand, in shear thickening fluids both heat transfer and skin friction is increased by 13% and 22%, respectively. Originality/value The authors believe that the present findings are beneficial in biomedical devices, drug delivery systems, microfluidic and lab-on-a-chip devices, bio-reactors, polymer processing, food and chemical industries and magnetic flow control systems.

Low thermal conductivity limits the effectiveness of conventional heat transfer fluids in industrial settings. Researchers have investigated modified fluid-based strategies to get around this. The mixed convection of a viscoelastic Brinkman nanofluid passing over a horizontal circular cylinder is examined in this work. The equations were simplified by using the Buongiorno nanofluid model and the necessary non-dimensional and similarity transformations. The Keller-Box Method (KBM), which is implemented in Matlab package, was then used to solve the equations numerically. In addition to the profiles of velocity, temperature, and nanoparticle volume fraction, numerical solutions are provided and analysed for the coefficient of skin friction, local Nusselt and Sherwood numbers, and the viscoelasticity, Lewis number, Brownian number, buoyancy ratio parameter, and thermophoresis parameter for each of the governing parameters. Numerical solutions are presented and analysed for the skin friction coefficient, local Nusselt number and Sherwood number alongside the profiles of velocity, temperature, and nanoparticle volume fraction for different governing parameters, specifically the viscoelasticity, Brownian number, buoyancy ratio parameter, and thermophoresis parameter. The numerical findings unequivocally indicate that an increase in the viscoelastic parameter results in a significant decrease in the skin friction coefficient, attributed to the inhibition of momentum diffusion near the cylinder surface caused by the elastic characteristic in the fluid.

ABSTRACT This study examines the combined effects of dual chemical reactions and thermal radiation on the magneto‐Sisko fluid flow along a stretching cylinder containing motile microorganisms. This mathematical modeling also considers the impact of the Buongiorno model to illustrate the effects of Brownian motion and thermophoresis diffusion. The dimensionless nonlinear ODEs are created by converting the governing boundary layer equations of fluid flow using the appropriate variables. The MATLAB software's Bvp4c (Lobatto‐IIIa) solver is used to numerically solve the transformed coupled nonlinear ODEs. The thermal distribution, velocity profiles, solutal profile, and microbe profiles are shown for the curvature parameter, Prandtl number (), Eckert number (), Lewis number (), Peclet number (), and the magnetic field parameter. Numerical variation in the friction drag, motile density of gyrotactic microorganisms, thermal and mass transport rates are investigated using graphs and tables to represent physical interpretation. The analysis reveals that the thermophoretic diffusion parameter enhances both the temperature field and the thickness of the thermal boundary layer, whereas an increase in the Peclet number leads to a reduction in the motile microorganism density. The current study has several real‐world applications, such as biomedical engineering for tissue modeling and polymer processing optimization, improved tissue integration, pollutant dispersion, building ventilation systems, medical imaging, and electronics heat management. The model has been verified by comparing the data from previous literature with the current study in a limiting case.

Enhancing convective heat transfer in enclosures is vital for advanced cooling and energy-efficient thermal systems. Hybrid nanofluids, combining multiple nanoparticles, offer enhanced thermal conductivity and flow control compared to conventional fluids. This study investigates natural convection of a ZrO 2 –ZnO/water hybrid nanofluid inside a flower-shaped cavity. The unique cavity geometry, featuring dual circular cores, induces secondary vortices and complex flow structures that strongly influence heat transfer. The governing nonlinear equations for mass, momentum, energy, and concentration were formulated and nondimensionalized. Numerical simulations were performed using the Finite Element Method (FEM) implemented in COMSOL Multiphysics, with grid dependency tests ensuring accuracy. Parametric studies explored the effects of Prandtl (Pr), Grashof (Gr), Rayleigh (Ra), Hartmann (Ha), Reynolds (Re), and Lewis (Le) numbers on velocity, temperature, and concentration fields. The hybrid nanofluid significantly enhanced thermal convection compared to the base fluid, with Nusselt number improvements up to 45%. Critical Ra marked the onset of strong cavity-induced vortices, while increasing Ha suppressed secondary flows due to Lorentz forces. Higher nanoparticle concentration improved thermal conductivity but altered diffusivity, reflected in variations of Pr and Le. Graphical and tabulated results show the interplay of geometry and hybrid nanofluid properties, offering quantitative design insights for cooling and heat exchange systems.

This theoretical study aims to investigate the heat and mass transference features in the magnetized flow of Ree–Eyring nanofluid comprising both nanoparticles and gyrotactic microorganisms with Joule heating over a curved stretchable surface. By employing the Buongiorno nanofluid model, we examine the influences of thermophoresis and Brownian diffusions which are essential to accurately capture the behavior of nanofluids under thermal and magnetic affects. The presence of nanoparticles and gyrotactic microorganisms enhances the thermal conductivity and stability of the fluid making it suitable for various industrial applications, such as cooling systems, biomedical devices, and enhanced oil recovery. The flow configuration in the form of a mathematical expression of the present boundary layer problem is obtained as a set of partial differential equations (PDEs) after utilizing the curvilinear coordinate systems. To simplify the complexity of these equations, we apply similarity transformations that reduce the PDEs to a system of nonlinear ordinary differential equations (ODEs). This transformed set of ODEs is then solved numerically by using the Keller-box method a robust technique for handling boundary layer problems in fluid dynamics. A detailed graphical and tabular analysis is performed to illustrate the influence of numerous variables on the concerned profiles. The graphical results reveal that the microorganism’s concentration profile reduces for the higher values of the bioconvective Lewis number, radius of curvature parameter, Peclet number, and microorganism difference constant. However, the profile of the Motile number shows a favorable response for upshot values of all the above-defined parameters.

The aim of current study is to examine the fluid flow by considering these two apparatuses combined in a single mathematical model. The effects of Brownian motion and thermophoresis also applied to the flow problem. The triple diffusive mixed convection Casson nanofluid flow has been considered through the space between cone and disk, using impacts of microorganisms and magnetic effects. This work is significant for enhancing heat and mass transfer control in rotating systems, with applications in bio-reactors, thermal engineering, polymer processing, and magnetically regulated non-Newtonian fluid technologies. The main equations have solved through Homotopy Analysis Method (HAM) in dimensionless form. In this study, fluid velocity augments with higher Grashof numbers but decreases with stronger magnetic and Casson effects. Temperature and concentration rise with thermophoresis, while Brownian motion enhances temperature but reduces mass diffusivity. Microorganism behavior weakens with higher bioconvection Lewis and Peclet numbers. The comparative analysis confirms agreement with existing literature. Moreover, as thermophoresis rises from 1.0 to 4.0, the heat transfer rate increases from 1.9057 to 2.3332, while Brownian motion causes a larger rise from 2.0057 to 3.4968. The percentage heat transfer rate varies from 2.30% to 12.27% for thermophoresis and from 3.20% to 14.46% for Brownian motion, indicating a stronger influence of Brownian motion.

This study presents an analysis of coupled thermal and concentration gradients in nanofluid boundary-layer flow over a stretching surface under the influence of magnetic, thermal, and mass transport effects. The governing nonlinear partial differential equations describing momentum, energy, and nanoparticle concentration are formulated for an electrically conducting nanofluid and solved numerically using the finite element method. Emphasis is placed on the roles of key dimensionless parameters including the magnetic field parameter, thermal and solutal Grashof numbers, Prandtl number, Brownian motion, thermophoresis, heat source, heat absorption, Lewis number, and chemical reaction rate on velocity, temperature, and concentration distributions within the boundary layer. The results indicate that the applied magnetic field retards the flow due to the Lorentz force, while buoyancy forces arising from thermal and concentration differences enhance fluid motion along the stretching surface. Thermal profiles are strongly influenced by internal heat generation, heat absorption, thermophoresis, and fluid thermal diffusivity, whereas nanoparticle concentration is governed by the combined effects of Brownian diffusion, thermophoretic transport, chemical reaction, and mass diffusivity. The analysis highlights the strong coupling between heat and mass transfer mechanisms in nanofluid boundary layers and demonstrates that controlling these parameters can effectively regulate transport processes in applications such as polymer extrusion, cooling of stretching sheets, coating processes, and advanced energy systems.

ABSTRACT Large Eddy Simulations with flamelet-based thermochemistry are used to investigate the behavior of a premixed hydrogen-air flame stabilized by a bluff-body. Validation against experimental data is carried out first to demonstrate the model’s ability to predict both velocity field and flame structure. The capability of the model in predicting differential diffusion effects is then assessed, in particular regarding the coupling between differential diffusion, tangential strain and curvature, and their effect on mixture fraction redistribution and reaction rate variation. Results indicate that unstretched flamelet thermochemistry is capable of capturing the increase in mixture fraction caused by positive resolved strain, as well as negative variations of mixture fraction due to negative curvature. Furthermore, the model is observed to mimic the effects of negative Markstein length to a certain extent, so that positive tangential strain causes reaction rate increase. The interplay between resolved stretch and preferential diffusion is also shown to lead to a shorter flame length which is in better agreement with experimental observations as compared to simulations under unity Lewis number assumption. These findings highlight that the macroscopic effects of differential diffusion and stretch on the premixed hydrogen flame, characterized by significant strain levels, can be predicted using a flamelet-based approach and without recurring to strained flamelets database, which implies important simplifications in the combustion modeling of turbulent hydrogen-premixed flames and offers valuable insights for the design of novel combustors.

The local thermal non-equilibrium (LTNE) effects are used for temperature variances between liquid and solid phases in porous media and heat transfer systems, such as nuclear waste disposal, geothermal reservoirs and packed bed reactors. This study provides a comprehensive modeling of hybrid nanofluid (HNF) flow along a Riga plate, combining impacts of LTNE between the solid and liquid stages. LTNE is used to determine the energy equations and distinct temperature profiles for the liquid and solid phases. The model considers a Riga plate fixed in a Darcy–Forchheimer porous medium to highlight the dominant electrohydrodynamic interactions. The effect of activation energy is also considered. The governing partial differential equations (PDEs) are changed into ordinary differential equations (ODEs) by the application of similarity transformations. The bvp-4c technique with a shooting methodology is used to describe the created system of ODEs. The impacts of important parameters on concerned profiles have been demonstrated in tabular and graphical forms. The outputs determine that LTNE significantly improves thermal performance, while the Riga plate efficiently moderates boundary layer dynamics. The temperature for solid phase decreases by raising the parameter of non-dimensional inter phase heat transfer. The concentration profile declines by growing the Lewis number. The Darcy–Forchheimer effects significantly influence flow and thermal transport. The study offers understanding of improving HNF applications for thermal management.

The combustion behaviour of single iron particles is experimentally investigated at a fixed oxygen concentration of 40%, diluted in 60% He, Ar, and Xe, using an electrostatic levitator with laser ignition. While the three gas mixtures have identical adiabatic flame temperature predictions using thermodynamic equilibrium calculations, the experiments reveal a noticeable difference in particle temperatures due to differences in Lewis number. This temperature variation is evident in particle luminosity and in nano-oxide formation, observed through the attenuation of white LED light. In the helium-diluted mixture, insignificant nano-oxide formation is observed due to lower particle temperatures, which subsequently reduces Fe evaporation and vapour-phase combustion. In contrast, xenon dilution enhances vapour-phase combustion, yielding pronounced nano-oxide formation, while argon shows intermediate behaviour. Despite large differences in oxygen mass diffusivity, measured combustion times, defined from melting onset to peak temperature, are comparable for helium- and argon-diluted mixtures, and only slightly longer for the xenon-diluted mixture. Using these combustion times, the discreteness parameter, χ , of iron flames is qualitatively compared: it is 1.71 times higher in 40% O 2 –60% Ar than in 40% O 2 –60% Xe, and 5.28 times higher in 40% O 2 –60% He than in 40% O 2 –60% Xe. The results indicate that discrete flame propagation is likely in argon-diluted mixtures but unlikely in helium-diluted mixtures. The present study highlights how the Lewis number influences the interplay of oxygen mass diffusivity and vapour-phase combustion in evaluating particle combustion time and flame discreteness, providing essential insights for designing future discrete flame microgravity experiments in different gas mixtures and advancing iron combustion models. • The Lewis number of the gas mixture influences the particle temperature. • Nano-oxide formation is denser in xenon dilution than in helium dilution. • Combustion time is not significantly affected by the monoatomic diluents used. • Discrete flame propagation can likely occur in a 40%O2–60%Ar gas mixture.

Hydrogen is a critical component of a carbon-free modern economy, offering clean and versatile applications across transportation, industry, and power generation. However, its high flammability and potential for explosions necessitate rigorous safety management, including predictive modelling, robust infrastructure design, and comprehensive safety protocols. One of the most challenging events is the catastrophic rupture of compressed gaseous hydrogen (CGH2) tanks, which can result in a combination of blast waves, fireballs, and flying debris. While blast waves and fireballs have been extensively studied with notable contributions from Ulster University in developing predictive correlations, experimental data for large hydrogen inventories remain limited, leading to significant uncertainties when extrapolating these correlations. The unique properties of hydrogen, such as high mass diffusivity, large variation in Lewis number, high laminar flame velocity, and small detonation cell size, require careful consideration when scaling up experiments. To address these gaps, SID-EPN and CEA have conducted large-scale experiments on the catastrophic rupture of Type IV CGH2 tanks, assessing the validity of existing correlations for extensive ranges of hydrogen quantities. This article reviews these correlations, compiles recent experimental results from open literature, and presents new experimental results to support the use of these correlations for larger hydrogen inventories.

This article examines the thermohaline stability of a power-law fluid saturating a porous layer in the presence of a magnetic field. The system stability is analyzed using both linear and weakly nonlinear instability theories. Within the linear framework, the Galerkin method is employed to derive analytical expressions for the Rayleigh number corresponding to steady and oscillatory modes of instability. Takens–Bogdanov and Hopf bifurcation points are identified, highlighting the transition mechanisms between different instability regimes. An increase in the Hartmann number delays the onset of convection. The critical Rayleigh number is a monotonic increasing function of the solute Rayleigh number, whereas it is a non-monotonic function of the Peclet number. To investigate heat and mass transport characteristics, an amplitude equation is derived in the weakly nonlinear regime. The results reveal that increasing the Hartmann, Lewis, and Peclet numbers enhances both heat and mass transport, whereas an opposite trend is observed with increasing the solute Rayleigh number.

The enquiry inspects the movement of bioconvection through a nanoliquid near the stagnant flow subject to a stretchable surface. The effects of convective flow condition, radiative flow with rate of heat generation/absorption and chemical reaction are considered in energy and concentration equations. A well-known Buongiorno’s the nanofluid model is applied to examine the effects of Brownian movement and thermophoresis characteristics. Irreversible analysis of the proposed system is also carried out. The modelled formulations having partial differential equations (PDEs) are transmuted through suitable transformations. Further, the set of transmuted ordinary differential equations (ODEs) can be employed by the analytical method recognised as the homotopic technique. The significance of numerous important variables in represented equations has been visually illustrated along with pertinent physical outcomes. The outcomes indicates that the rate of flow reduces due the rising values of Casson fluid variable (𝛾) while the Bejan profile is increasing with a bigger estimation of (𝛾). The augmentation in the thermal radiation (Rd) and Biot number (Bi) improved in the temperature field. However, reduction in motile density due to the larger magnitude of Bioconvection Lewis number (Lb). Comparison has been endeavored in the results of past publishing result.

This work examines the influence of Cattaneo–Christov heat flux on magneto hydrodynamic (MHD) flow of non-Newtonian fluids; Jeffrey, Maxwell and Oldroyd-Bover a stretching sheet, integrating activation energy and velocity slip effects. The governing partial differential equations are converted into similarity-based nonlinear ordinary differential equations and solved numerically utilizing MATLAB’s BVP5C solver. Results reveal that higher relaxation-to-retardation ratios, larger Deborah numbers and increased slip significantly reduce fluid velocity with Oldroyd-B fluid and Maxwell fluid exhibits the greatest decrease, while Jeffrey fluid is minimally affected. Thermal Deborah number enhances heat flux relaxation, leading to elevated temperature profiles and a thicker thermal boundary layer. Increased activation energy slows chemical reactions but raises nanoparticle concentration with Jeffrey fluid. Validation against previous studies confirms the accuracy and reliability of the solutions. Furthermore, skin friction decreases with magnetic parameters, relaxation ratio and slip, whereas the Nusselt number increases with heat flux relaxation and radiation but diminishes due to Brownian motion, thermophoresis and non-uniform heat. Sherwood number rises with Lewis number, reaction rate, Brownian motion and reaction strength but decreases with thermophoresis and activation energy. Maxwell fluid consistently exhibits the most favourable transport rates, Jeffrey fluid the least, with Oldroyd-B liquid intermediate due to rheological differences.