Acoustofluidic devices use Surface Acoustic Waves (SAWs) to handle small fluid volumes and manipulate nanoparticles and biological cells with high precision. However, SAWs can cause significant heat generation and temperature rises in acoustofluidic systems, posing a critical challenge for biological and other applications. In this work, we studied temperature distribution in a Standing Surface Acoustic Wave (SSAW)-based PDMS microfluidic device both experimentally and numerically. We investigated the relative contribution of Joule and acoustic dissipation heat sources. We investigated the acoustofluidic device in two heat dissipation configurations-with and without the heat sink-and demonstrated that, without the heat sink the temperatures inside the microchannel increased by 43 °C at 15 V. Adding the metallic heat sink significantly reduced the temperature rise to only 3 °C or less at lower voltages. This approach enabled the effective manipulation and alignment of nanoparticles at applied voltages up to 15 V while maintaining low temperatures, which is crucial for temperature-sensitive biological applications. Our findings provide new insights for understanding the heat generation mechanisms and temperature distribution in acoustofluidic devices and offer a straightforward strategy for the thermal management of devices.

The advanced thermal management, a growing demand in micro-scale devices, and biomedical technologies present extensive studies into enhanced heat transfer mechanisms. Among the various fluids, tri-hybrid nanofluids within the base liquid water show a promising fluid because of their superior thermal conductivity. The ongoing analysis deliberates the flowing of micropolar tri-hybrid nanofluid composed of single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and copper (Cu) nanoparticles dispersed in water over an expanding surface under the interpretation of multiple slip conditions. In general, the present configuration is motivated by real-world applications, likely nano-coating technology, cooling of electronic equipment, etc. The current analysis integrates the velocity and thermal slip with the dissipative heat, such as viscous Joule and Darcy dissipation has a more realistic behaviour on the flow phenomena. The mathematical model proposed for the said assumptions is transformed into dimensionless form and then handled numerically utilizing a spectral weighted residual scheme for the combined effect of various factors. The validation of the existing outcomes compared with the earlier investigation found them to be in good correlation.

This research will focus on the entropy Generation of a magnetohydrodynamic (MHD) flow using Casson Willams hybrid nanofluid under flowing rotating disk with consideration of thermal radiation. It is a combination of three items of interest (i) von Kampankan swirling flow made possible by the rotation of the disk, (ii) hybrid nanofluid suspensions, more conductive of heat and better behaved in heat transfers than classical coolants, and (iii) converged non-Newtonian Casson (yield stress) and Williamson (viscoelastic relaxation). There is a generalization of the analysis of entropy-generation into heat-transfer, fluid-friction and Joule heating through the second law of thermodynamics. The Bejan number is used to a certain degree of distributing something irreversible. The mathematical model includes Rosseland approximation of thermal diffusion and Lorentz approximation that represents the MHD. Open slows of partial differential equations are simplified using transformations of a like manner into nonlinear ordinary differential equations, which are solved numerically. A parameter study is directional in such a way as to select the influence of the magnetic interaction parameter, the radiation parameter, the Casson parameter and the Williamson parameter. It is found that thermal radiation amplifies the wall heat flux with the reduction of temperature gradients far far disk and changes the distribution of entropy. Stronger MHD effects inhibit radial velocity and enhance Joule dissipation, meaning that the Bejan number is wastier. Reduced Casson parameter decreases shear stresses, decreases viscous entropy, and Williamson viscoelasticity redistribes entropy outside of the wall region. The paper builds on the current literature on non-Newtonian nanofluids, however, extending the area with a hybrid model, the CassonWilliamson in rotating disk geometry with MHD and radiation. The results give an understanding on minimization of irreversibility in rotating machines, biomedical devices, and power systems in advanced working fluids and electro-magnetic control measures are critical.

This study examines hybrid nanofluid flow through variable porous medium between two spinning disks. Both the disks rotate with varied angular velocities. The nanoparticles of Ag and TiO2 are mixed in H2O to fabricate a hybrid nanofluid. A magnetic field of intensity B0 is used in the normal direction of motion, with effects of Joule heating and viscous dissipation. The main equation of problem has been evaluated through homotopy analysis method. An increase in TiO2 and Ag + TiO2 nanoparticle concentrations, variable porous factor, and Reynolds number enhances axial momentum transfer, increasing radial and axial skin friction in both disks. When the volumetric fraction varies from 0.01 to 0.04, the heat transfer rate increases from 0% to 11.27% at the upper disk and from 0% to 15.46% at the lower disk, indicating the maximum percentage increase at the lower disk. The work has been validated through a comparative study of the current results with published work by ensuring a strong promise among all the results. The findings of this study offer valuable insights for optimizing cooling and thermal management in rotating machinery, turbine rotors, disk brakes, and energy devices, where hybrid nanofluids and porous media improve heat transfer and overall efficiency under Joule heating conditions.

Three-dimensional radiative magnetized copper nanofluid flow through angular rotating stretchable disks subject to Joule dissipation and chemical reaction

ABSTRACTThe growing need for enhanced thermal regulation is vital in recent advancements such as biomedical engineering, polymer processing, etc. In particular, the non‐Newtonian fluid likely Casson fluid with yield stress is used in these areas because of its ability to prepare biofluids and industrial suspensions effectively. The proposed analysis explores the magnetohydrodynamic (MHD) stagnation point flow of Casson fluid via an expanding surface for the impact of dissipative heat and chemical reaction. The heat transport phenomenon is enhanced for the combined impact of Joule dissipation and thermal radiation for the assumption of the Rosseland approximation. The analysis presents its vital role for the introduction of velocity slip and convective heating boundary conditions. Moreover, the modeled problem for the integration of above‐mentioned forces is characterized by the use of the similarity rule, which develops the role of diversified factors on the flow phenomena. To execute the physical behavior of the factors involved in the model, first of all, a standard numerical method, i.e., shooting associated with Runge–Kutta fourth‐order, is employed utilizing a built‐in bvp4c function in MATLAB. In connection with the study reported earlier, the present result is compared and validated with the numerical result in particular cases. Further, the important outcomes of the study are the enhanced non‐Newtonian Casson parameter that retards the velocity profile, and the heat transfer rate is also controlled by the increasing thermal radiation, whereas the Eckert number favors a significant enhancement in the heat transfer rate.

In this research article we investigate rate of heat transfer of magneto hydrodynamic MHD flow of casson hybrid nanofluid silicon oil through porous convergent/divergent ( α < 0, α > 0) and stretching/shrinking channels. The combination of base fluid Silicon oil, and nanoparticles Mn–ZnFe 2 O 4 and CoFe 2 O 4 are suspended in casson hybrid nanofluid. The Mathematical problem is explored in the form of partial differential equations PDEs by considering Joule heating radiation, heat source and dissipation effects. The ordinary differential equations (ODEs) are obtained by employing the similarity transformations. The influence of various significant parameters on different distributions are displayed via numerical data. The physical quantities are calculated for the nanofluid, hybrid nanofluid and for α > 0 and α < 0 cases. The NDSolve approach is used to find the solution of the model. The key finding is that, the drag friction increases against porosity parameter and inertia parameter for nano and hybrid nanofluid. Furthermore, nusselt number increase in convergent channel and decrease in divergent channel for Eckert number EC and heat source Q . Additionally, it is concluded that hybrid nanofluid has more reactive performance than nanofluid.

A flow of an electrically conducting fluid in the form of a round jet entering a square duct subjected to a transverse magnetic field is studied using direct numerical simulations. The complex dynamics of the jet, determined by the effects of Joule dissipation, the flow's transformation into anisotropic states, the Kelvin–Helmholtz instability leading to the development of large-scale fluctuations, and the constraints imposed by the duct's walls, is revealed through analysis of the fields of velocity, pressure, and electric currents. The results show a good qualitative agreement with earlier experiments and provide an explanation for the experimental findings. In particular, the simulations confirm the hypothesized existence of two distinct regimes of the flow: an unstable central jet at low-to-moderate Stuart numbers N and a macrovortex shedding large-scale quasi-two-dimensional eddies at large N. The system is also used as a benchmark for the exploration of possible sources of uncertainty in experimental and numerical analysis of liquid-metal magnetohydrodynamics (MHD). A detailed comparison between the results of the simulations and the experimental data, as well as a parametric study of the effects of the model assumptions, allows us to identify and quantitatively assess the main such sources: the accuracy of velocity measurement by the electric potential sensors, the uncertain electric conductivity of the walls, the velocity profile and perturbations at the inlet, and the time of averaging required for accurate evaluation of mean flow properties in the presence of large-scale eddies typical for MHD flows.

Heat transfer in magneto-hybrid nanofluids with viscous and joule dissipation: a successive over relaxation analysis

This study numerically examines the optimization of entropy in uranium dioxide (UO2)/polyethylene glycol–water (PEG–H2O) 50%–50% mixture of nanofluid flowing between a cone and a disk with porous media. The cone rotates over the expanding disk, and the nanofluid flows between the gap of the cone and the disk with the rule of the Darcy–Brinkmann model. This analysis is performed under stable flow conditions and incorporates a uniform magnetized field and trio dissipation, i.e., Darcy, viscous, and Joule dissipation. The model further conducted exothermic/endothermic reactions with waste discharge conditions to accumulate knowledge of the mass transmission process throughout the system. The bvp4c code is utilized for the graphical outcomes and, subsequently, employs the Runge–Kutta fourth-order to get the solutions. To enhance the computational efficiency of the heat transfer rate coefficient, a supervised model of an artificial neural network is employed. Comprehensive simulations yielded extremely low error (mean square error ≤ 1.9467 × 10−9) and an almost ideal regression coefficient (R ≈ 1). The study concludes that the high Reynolds number and Eckert number lead to better entropy generation of the nanofluid model.

This research investigates the transient hydromagnetic behavior and heat transfer attributes of a non-Newtonian Casson nanoliquid embedded with microorganisms, flowing past a stretched surface in a Darcy-Forchheimer medium. The effect of a magnetic field, oriented at an angle $\alpha$ with the boundary surface, Joule dissipation, and convective boundary conditions are considered to determine the flow behavior, heat transfer, nanoparticle concentration, and microorganism density. To solve the non-dimensionalized system of coupled and nonlinear partial differential equations, the bivariate spectral quasi-linearization method (BSQLM) is employed. This numerical scheme has proven to be both convergent and accurate. Outcomes are compared with the results available in the literature and found good agreement. Variations in flow, heat transfer, distribution of nanoparticles, and microorganisms are illustrated by reproducing the numerical results in graphical form, whereas Nusselt and Sherwood numbers are displayed in tables. The Casson parameter uniformly diminishes the velocity and temperature inside the boundary layer region. Angle of inclination ($\alpha$) boosts the temperature profile near the boundary and decreases the fluid velocity and nanoparticle concentration. The Prandtl number gives a rise in temperature near the wall and reveals an opposite effect away from the thermal boundary layer region. The Lewis number exerts a diminishing impact on the nanoparticle concentration field. Eckert number thickens the thermal boundary layer region. The microbe density field is a decreasing function of Peclet number. Solutal, thermal, and microorganism biot number exert, respectively, an enhancing effect on nanoparticle concentration, a diminishing influence on temperature profile, and a microbe density. This model is valuable for understanding the applications of solar energy in thermal engineering processes and has direct implications for industries such as glass and polymer manufacturing, thermal exchangers, homogenization, biomedical engineering, nuclear reactors, and metallic plate cooling.

Transient plasma events, such as plasma disruptions, are anticipated in the future magnetic-confinement nuclear fusion reactors. The events are accompanied by a rapid change in the magnetic field generated by the plasma current and, accordingly, induction of strong eddy currents and Lorentz forces within the reactor structure. This work targets processes within liquid-metal components of the reactor's breeding blankets. Order-of-magnitude analysis and exploratory numerical simulations are performed to understand the response of liquid metal to a rapidly changing magnetic field and to evaluate the accuracy of commonly used simplifying model assumptions. The response is found to consist of two stages: an initial brief stage (∼1 ms) characterized by a rapid increase in the induced currents, forces, and fluid velocity; and a subsequent stage, which is triggered by the growing velocity of the metal and marked by reversals of Lorentz force, and oscillations and decreases in the amplitude of the induced fields. The transition to the second stage sets the upper limit of the velocity (∼0.5 m/s in our tests), to which an initially quiescent metal can be accelerated during the event. The simulations indicate that many widely used model assumptions, such as the negligible role of Joule dissipation in the heat balance and the constancy of physical property coefficients, remain valid during the response. However, the assumption of liquid metal incompressibility is found to be questionable due to the potential significant effects of pressure waves.

Large-eddy simulations have been conducted to investigate the decay law of homogeneous turbulence influenced by a magnetic field within a cubic domain, employing periodic boundary conditions. The initial integral Reynolds number is approximately 1000, while the initial interaction number $N$ ranges from 0.1–100. The results reveal that the Joule cone angle $\theta$ , half of the Joule cone, decays as $\cos \theta \sim t^{-1/2}$ when $N \gg 1$ . In the nonlinear stage, small-scale vortices gradually recover and restore three-dimensionality. Moreover, the corresponding critical state at small scales, marking the transition from quasi-two-dimensional structure to the onset of three-dimensionality, has been quantitatively defined. During the linear stage, based on the true magnetic damping number ( $\tau _t = \rho / (\sigma {\boldsymbol{B}}^2 \cos ^2 \psi )$ , where $\sigma$ , $\boldsymbol{B}$ and $\psi$ denote the electrical conductivity, magnetic field and the angle between the wavevector and $\boldsymbol{B}$ in Fourier space, respectively), Moffatt’s decay law, $K \sim t^{-1/2}$ , manifests at distinct times and zones in the Fourier space, with $K$ signifying turbulent kinetic energy. In the nonlinear stage, for $N \gg 1$ , a $-3$ slope in the energy power spectrum is prominently observed over an extended period. The near-equivalence of the characteristic time scales of inertial and Lorentz forces in the inertial subrange suggests a quasiequilibrium state between energy transfer and Joule dissipation in Fourier space, thereby corroborating the hypothesis proposed by Alemany et al. 1979 Journal de Mecanique18(2): 277–313. Additionally, it is observed that pressure mediates energy transfer from horizontal kinetic energy ( $K_{\parallel }$ ) to vertical kinetic energy ( $K_{\bot }$ ), accelerating the decay of $K_{\parallel }$ . Notably, concurrent inverse and direct energy transfers emerge during the decay process. Our analysis reveals that the ratio $R$ of the maximum inverse to maximum direct energy flux correlates with the dimensionality of the turbulence, following the scaling law $R\sim (\cos \theta )^{-2.2}$ .

Effect of inclined magnetic field, non-uniform heat source on hybrid EG-MoS2-SiO2 radiative nanofluid flow with viscous and Joule dissipation over convectively heated elongating surface

We investigate the statistical properties of kinetic and thermal dissipation rates in two-dimensional/three-dimensional vertical convection of liquid metal ( $Pr = 0.032$ ) within a square cavity. Two situations are specifically discussed: (i) classical vertical convection with no external forces and (ii) vertical magnetoconvection with a horizontal magnetic field. Through an analysis of dissipation fields and a reasonable approximation of buoyancy potential energy sourced from vertical heat flux, the issue of the ‘non-closure of the dissipation balance relation’, which has hindered the application of the GL theory in vertical convection, is partially resolved. The resulting asymptotic power laws are consistent with existing laminar scaling theories and even show certain advantages in validating simulations with large Prandtl number ( $Pr$ ). Additionally, a full-parameter model and prefactors applicable to low- $Pr$ fluids are provided. The extension to magnetoconvection naturally introduces the approximate expression for total buoyancy potential energy and necessitates adjustments to the contributions of kinetic dissipation in both the bulk and boundary layer. The flow dimensionality and boundary layer thickness are key considerations in this analysis. The comprehension of Joule dissipation has been updated: the Lorentz force generates positive dissipation in the bulk by suppressing convection, while in the Hartmann layer, shaping the exponential boundary layer requires the fluid to perform positive work to accelerate, leading to negative dissipation. Finally, the proposed transport equations for magnetoconvection are supported by current direct numerical simulation (DNS) and literature data, and the applicability of the model is discussed.

Walters B’ hybrid nanofluid flow with Marangoni convection

This study aims to scrutinize the numerical exploration of the unsteady axisymmetric flow of hybrid nanofluid (Ag-Gr\H2O) across a radial surface. This research addresses the need for enhanced heat transfer mechanisms in industrial applications by incorporating the effects of convective thermal transfer, suction\injection, Joule heating, and viscous dissipation. The collection of flow-controlling Partial Differential Equations (PDEs) has been simplified to Ordinary Differential Equations (ODEs) by the appropriate similarity transformations. Further, the finite difference method (Keller Box technique) is incorporated to determine the numerical solutions with the assistance of MATLAB software. The fluid flow and thermal distributions are examined to understand the impact of different factors such as magnetic strength, unsteadiness, Eckert number, Biot number, suction\injection, porosity, and nanoparticle volume fraction. The results demonstrate significant enhancements in thermal distribution for the enhanced Eckert number and Biot number. As magnetic and porosity parameters increase, the flow distribution declines. Moreover, the tabular form depicts local changes in Nusselt number and skin friction coefficient for a certain range of embedded parameters. The present study was compared to prior studies and showed remarkable concurrence with previous findings. This consistency underscores the robustness of our methodology and the reliability of the results.

Heat generation and Joule dissipation influence on Magnetohydrodynamic Cu- H2O and Al2O3-H2O nanofluid convection with nanoparticle volume fraction and ramped and isothermal wall temperature: A finite element approach

Naval magnetohydrodynamic (MHD) propulsion is faced with the high level of Joule dissipation associated with the low electrical conductivity of seawater, reducing the efficiency of the pump at the heart of an MHD thruster. An MHD pump experiment is discussed in this paper, together with its CFD modelling. A simple analytical model is also written for conduction MHD pumps, then for a boat equipped with such a pump working as an MHD thruster. The numerical and analytical results are compared to our pump experiment and to a small-scale boat model. By upscaling, we show how strong should be the magnetic field, and how large the MHD channel to obtain a given efficiency for the pump or a given cruise speed for the boat. Tables 2, Figs 8, Refs 7.

The aim of the study is to analyse the impact of Joule dissipation and thermal radiation on the magnetic-hydrodynamics squeezed flow among Riga plates in the Cattano-Christov heat flux model. The Riga plate, called the electromagnetic actuator, is composed of permanent magnets and changing electrodes based on plane surfaces. This non-Fourier (Cattano-Christov) heat flux form because of thermal relaxation time into the Fourier's law was equipped for analyses of characteristics on heat transport. This ensuing structure in the nonlinear ordinary differential equations, including its boundary conditions, was determined mathematically by the finite element method. The impact on varied parameters in the energy, concentration and flow was analysed and shown graphically. Furthermore, the effect on preferred parameters in decreased Sherwood number, skin friction and Nusselt number, was more graphically depicted. There was a major rise in the temperature of the fluid along with increasing thermal radiation. Furthermore, the rising magnetic field parameter and squeezed parameter solutions result in a stable reduction of the skin friction over the above Riga plate. The regular development of the Nusselt number was noted in increasing thermal relaxation time and radiation parameters.