Ferrofluid Flow Research Articles

Increasing Flow Complexity in Time-Dependent Modulated Ferrofluidic Couette Flow

Increasing Flow Complexity in Time-Dependent Modulated Ferrofluidic Couette Flow

Variable thermal effects of viscosity and radiation of ferrofluid submerged in porous medium

Ferrofluid is a liquid that becomes magnetized in the presence of magnetic field. Applications involves in electronic devices, mechanical engineering, materials science research and loudspeakers. This study is achieved to explore the novel two-dimensional steady ferrofluid flow in a porous medium with the temperature dependent thermal conductivity and viscosity effect. ODE’s are obtained with the help of appropriate similarity transformation. Later the equations are work out by applying shooting scheme with RK-4 technique. To achieve the results of non-dimensional physical parameters the numerical computations are put into execution. The graphical consequences for fluids velocity and temperature for variable effects of viscosity and thermal conductivity are demonstrated. Velocity of fluid decays for viscosity parameter while the temperature uplifts in the presences of viscosity. Furthermore, comparison of the results with previous one shows that the applied method is efficient and useful for calculating the parameters of present problem and have acceptable accuracy.

Numerical Investigation of Ferrofluid Flow at Lower Stagnation Point over a Solid Sphere using Keller-Box Method

In this paper, ferrofluid flow at lower stagnation point on solid sphere is investigated theoretically by considering mixed convection boundary layer flow. The sphere surface is exposed to the magnetic field and thermal radiation by taking into account constant wall temperature boundary conditions. The discovery of the existing magnetic field near the surface while the ferrofluid flowing leads to the development of phenomenology called magnetohydrodynamic. The magnetite (Fe3O4) acts as nanoparticles dispersant and suspended in the water contained in ferrofluid are assumed as Newtonian fluid and behave as single-phase fluid flow is studied. These assumptions give physical insight into the behaviour of ferrofluid flow to be analysed and discussed. The Keller-box method is applied to solve the transformed partial differential equations numerically. The numerical results found the viscosity measured from magnetite (Fe3O4) volume fraction is the main element provided to the trend of the ferrofluid velocity flow. Besides, the ferrofluid temperature at lower stagnation point on sphere is proven influence the ferrofluid viscosity and change the velocity of ferrofluid flow.

Effects of Magnetic Fields, Coupled Stefan Blowing and Thermodiffusion on Ferrofluid Transport Phenomena

The paramagnetic feature of ferrofluid allows it to be utilised in electronic devices and improvise fluid circulation in transformer windings. Hence, the present article aims to conduct the numerical study of ferrofluid boundary layer flow along with the Stefan blowing, velocity and thermal slip, and Soret effects within the stagnation region over a stretching/shrinking surface. The governing equations were solved numerically using the bvp4c function in the MATLAB computing package. Based on the results, a stronger magnetic field of ferrofluid was needed to identify the numerical solutions past the shrinking surface, while the Stefan blowing diminished the solution’s availability. More than one solution is acquired for some specific values of the shrinking parameter, and the stability analysis validated that only one solution is reliable and stable.

Unsteady Magnetohydrodynamics (MHD) Flow of Hybrid Ferrofluid Due to a Rotating Disk

The flow of fluids over the boundaries of a rotating disc has many practical uses, including boundary-layer control and separation. Therefore, the aim of this study is to discuss the impact of unsteady magnetohydrodynamics (MHD) hybrid ferrofluid flow over a stretching/shrinking rotating disk. The time-dependent mathematical model is transformed into a set of ordinary differential equations (ODE’s) by using similarity variables. The bvp4c method in the MATLAB platform is utilised in order to solve the present model. Since the occurrence of more than one solution is presentable, an analysis of solution stabilities is conducted. Both solutions were surprisingly found to be stable. Meanwhile, the skin friction coefficient, heat transfer rate—in cooperation with velocity—and temperature profile distributions are examined for the progressing parameters. The findings reveal that the unsteadiness parameter causes the boundary layer thickness of the velocity and temperature distribution profile to decrease. A higher value of magnetic and mass flux parameter lowers the skin friction coefficient. In contrast, the addition of the unsteadiness parameter yields a supportive effect on the heat transfer rate. An increment of the magnetic parameter up to 30% reduces the skin friction coefficient by 15.98% and enhances the heat transfer rate approximately up to 1.88%, significantly. In contrast, the heat transfer is rapidly enhanced by improving the mass flux parameter by almost 20%.

Multiparticle collision dynamics for ferrofluids.

Detailed studies of the intriguing field-dependent dynamics and transport properties of confined flowing ferrofluids require efficient mesoscopic simulation methods that account for fluctuating ferrohydrodynamics. Here, we propose such a new mesoscopic model for the dynamics and flow of ferrofluids, where we couple the multi-particle collision dynamics method as a solver for the fluctuating hydrodynamics equations to the stochastic magnetization dynamics of suspended magnetic nanoparticles. This hybrid model is validated by reproducing the magnetoviscous effect in Poiseuille flow, obtaining the rotational viscosity in quantitative agreement with theoretical predictions. We also illustrate the new method for the benchmark problem of flow around a square cylinder. Interestingly, we observe that the length of the recirculation region is increased, whereas the drag coefficient is decreased in ferrofluids when an external magnetic field is applied compared with the field-free case at the same effective Reynolds number. The presence of thermal fluctuations and the flexibility of this particle-based mesoscopic method provide a promising tool to investigate a broad range of flow phenomena of magnetic fluids, and the method could also serve as an efficient way to simulate solvent effects when colloidal particles are immersed in ferrofluids.

Investigation of the entropy production rate of ferrosoferric oxide/water nanofluid in outward corrugated pipes using a two-phase mixture model

This study investigates the turbulent entropy production rate of ferrosoferric oxide/water (Fe3O4/H2O) nanofluid flowing through outward corrugated pipes of different profiles (circular, triangular, and trapezoidal). Both the multi-phase mixture model and the k−ω turbulent model were adopted for simulating the turbulent ferrofluid flow. The effects of Reynolds number (between 5.0 × 103 and 3.0 × 104) and nanoparticle concentration (0.0–3.0%) on viscous entropy production rates (due to mean and turbulent velocity gradients) and thermal entropy production rates (due to mean and turbulent temperature gradient) were examined parametrically. The results show that trapezoidally corrugated pipes tend to have the best heat transfer performance, but also the worst hydraulic performance, where they increase the pressure drop and the average Nusselt number by 2.92 and 1.66 folds, respectively, for a 2.0% nanoparticles’ concentration at Reynolds number of 3.0 × 104. Increasing the concentration of nanoparticles from 0.0 to 3.0% has the same effect, where the two quantities increase by 1.31 and 1.07, respectively, for a triangularly corrugated pipe at a Reynolds number of 1.5×104. The mean temperature gradient contributes most to the thermal entropy production rate, compared to the turbulent temperature gradient. However, the opposite is the case for the viscous entropy production rate. Furthermore, the presence of corrugation was found to increase the viscous entropy production rate but reduce the thermal entropy production rate. The normalized thermal and viscous entropy production rates (referencing a smooth pipe) in circularly, triangularly, and trapezoidally corrugated pipes are {0.81, 0.75}, {0.56,3.38}, and {3.29,3.45}, respectively. It is also noticed that the Bejan number decreases as the Reynolds number increases by 51.4, 81.4, 82.2, and 87.6% for smooth, circularly corrugated, triangularly corrugated, and trapezoidally corrugated pipes, respectively.

Influence of external magnetic manipulation on thermal transport characteristics of the bubble-slug flow of ferro-nanocolloids

Bubble-slug flows are an important two-phase flow pattern known for their superior transport characteristics, which predominantly depend on the phase distribution (bubble and slug lengths). In the present work, it is shown that the thermal transport characteristics of such flows can be substantially enhanced and tuned as per requirement by utilizing ferro-nanocolloids or ferrofluids as the primary liquid phase. The magnetic properties of ferrofluids provide an additional means to manipulate their flow characteristics externally. The flow morphology of the Taylor bubble flow of ferrofluid is altered through an externally applied magnetic field (MF). Smaller bubble-slug units are generated in the resulting flow through external magnetic manipulation while all other parameters are kept identical. The ensuing heat transfer of different flow morphologies generated through such manipulation is examined using micro-thermometry. It is shown that the smaller bubble-slug units can considerably augment thermal transport in such flows. The movement of smaller units creates a frequent disruption to the boundary and interfacial regions of the flow, and additional recirculation regions are formed, resulting in the augmentation of both local and overall convective transport. Augmentation in heat transfer of up to 80% is seen in the present case, which mainly depends on the homogeneous gas fraction of the flow. The present study demonstrates that for a given homogeneous gas fraction (> 0.50), smaller bubbles and unit-cells are superior for achieving a higher heat transfer coefficient. In addition, the utilization of ferrofluids provides an excellent alternative for heat transfer augmentation via external manipulation in non-boiling two-phase flows. With all other flow parameters kept identical, the results clearly show the role of smaller bubble-slug units in augmenting heat transfer.

FHD flow and heat transfer over a porous rotating disk accounting for Coriolis force along with viscous dissipation and thermal radiation

AbstractThe prime concern of the current findings includes the effect of viscous dissipation and nonlinear thermal radiation on the study of ferrofluid flow and heat transfer past a porous rotating disk. The time‐independent flow of incompressible ferrofluid is modeled for the considered geometry, and via similarity transformations, the given system is converted to a dimensionless system of the nonlinear ordinary differential equations. Here, the findings are explored computationally with help of Maple software. The study exhibits the effect of the involved emerging parameters: the interaction parameter , Prandtl number , rotation parameter , radiation parameter , Eckert number , and these are discussed graphically. Moreover, the numerical values of heat transfer rate and skin frictions are also presented in tabular form. From the perspective of numerical findings, it is perceived that the radial flow is dominant when we increase the rotation of the disk. Furthermore, the magnitude of magnetic‐fluid temperature is enhanced with the surge in the magnetic field, viscous dissipation, and thermal radiation mechanism. Finally, the current research can successfully fill a gap in the existing literature.

Influence of the diameter of the magnetic core and surfactant thickness on water carrying iron (iii) oxide ferrofluid flow over a rotating disk

Analysis of ferrofluid over a rotating plate is very important in the field of biomedical sciences, electronic devices, and aerodynamics. This work investigates the influence of the diameter of the magnetic core and thickness of the surfactant layer on water-carrying iron(iii) oxide ferrofluid flow and heat transfer over a rotating disk in the presence of a stationary magnetic field. The nonlinear differential equations for velocity and temperature are solved numerically using the finite element procedure. The validation of the present numerical solution is also demonstrated. The non-Newtonian results under the influence of stationary magnetic field for velocity and temperature profiles are compared with the Newtonian results of velocity and temperature profiles in the absence of the magnetic field. Increasing the diameter size of the iron(iii) oxide nanoparticles reduces the velocity and temperature in the flow. However, the thickness of the surfactant layer enhances the velocity and temperature. However, the magnetic field produces the shear thickening in the flow. Enhancement in the diameter of the iron (iii) oxide nanoparticles increases the stress on the disk and local heat transfer, and enhancement in the thickness of the surfactant layer of the nanoparticles reduces the stress and local heat transfer.

On-demand augmentation in heat transfer of Taylor bubble flows using ferrofluids

The thermo-fluidic transport characteristics of ferrofluids can be influenced by the application of a magnetic field. The magnetic manipulations of ferrofluids have been useful in augmenting heat transfer, as evident from recent investigations. In the present study, we examine a novel strategy for augmenting two-phase heat transfer and show that the magnetic manipulation of non-boiling Taylor bubble flow (TBF) of ferrofluids can provide on-demand augmentation. In an earlier investigation (DOI:10.1016/j.colsurfa.2020.124589), we had shown that the characteristics of the TBF of ferrofluids could be altered through external magnetic manipulations. As transport characteristics of TBFs primarily depend on their flow morphology, it was anticipated that such alteration would affect their thermal transport characteristics, which are examined in the present work. The generation of smaller bubbles and unit-cells through magnetic manipulations decreases the void fraction of the resulting TBF. In addition, a greater number of units participated in the heat exchange process compared to larger bubble-slug systems at any time instance. Such flow modifications cause considerable augmentation (which can go up to 100%) in two-phase heat transfer. The extent of augmentation depends on the applied magnetic field and induced magnetic force, homogeneous gas fraction, liquid film thickness/void fraction and flow morphology of the resulting TBF, which are examined in the present study. The application of ferrofluids in TBFs provides multiple benefits, such as suspension of nanoparticles with better thermal properties and additional functionality of the flow manipulations through external means. The proposed application with the suggested manipulation technique provides an effective alternative for an on-demand augmentation in two-phase heat transfer in low Reynolds number flows.

Contribution of the dipole–dipole interaction to targeting efficiency of magnetite nanoparticles inside the blood vessel: A computational modeling analysis with different magnet geometries

The widespread use of magnetite nanoparticles inside the bloodstream for diagnostic and therapeutic purposes has made the influence of the interaction forces between these nanoparticles an important issue for predicting their behavior for improving the effectiveness of the protocols. Magnets with various geometries have been used in different biomedical applications, such as targeted drug delivery, to guide drugs carrying magnetite nanoparticles to specific areas. In this regard, using computational modeling, we have employed a multiphysics modeling approach using the particle tracing module in the COMSOL software environment to investigate the behavior of magnetite nanoparticles considering not only the magnetophoretic force, but also the dipole–dipole interaction forces between the nanoparticles. The effects of different geometries of magnets on the induced magnetic flux density and the laminar flow velocity inside the bloodstream were studied as well. The results of our study show that each geometry of the magnet induces different magnetic flux density profile and laminar velocity inside the blood flow. The behavior of ferrofluid flow is dependent on the geometry of the magnet and its remanent flux density. By increasing the size of magnetic nanoparticles, the magnetophoretic force enhances the particle velocity in the direction perpendicular to the vessel's walls, which could result in pull out. The results also reveal that the magnetic dipole–dipole interactions between nanoparticles could lead to the induction of higher dipole–dipole interaction forces in regions close to the magnet, especially on the upper wall of the blood vessel.

Ferrofluidic Couette flow in time-varying magnetic field

Despite time-dependent boundary conditions being ubiquitous in natural and industrial flows, to date the influence of such temporal modulations (e.g. with driving frequency ΩH) has been given minor attention. The present problem addresses ferrofluidic Couette flow in between counter-rotating cylinders in a spatially homogeneous magnetic field subject to time-periodic modulation. Such a modulation can lead to a significant inner Reynolds number (Rei) enhancement for both, either helical and toroidal flow structures. Using a modified Niklas approximation, the effect of low- and high-frequency modulation onto the primary instabilities, stability boundaries as well as on the non-linear oscillations that may occur is investigated. Focusing on bi-stable co-existing solutions, around their stability thresholds quite complex non-linear system response and flow dynamics is detected. For the system remaining supercritical always a single solution is selected by ΩH, while crossing the bifurcation thresholds within a modulation period the triggered system response is more complex, reaching from alternation between different solutions towards the appearance of intermittent behavior.

Effect of variable viscosity and thermal conductivity on water-carrying iron (iii) oxide ferrofluid flow between two rotating disks

Effect of variable viscosity and thermal conductivity on water-carrying iron (iii) oxide ferrofluid flow between two rotating disks

Promotion of ferrofluid microchannel flows by gradient magnetic fields

• Ferrofluid Couette-Poiseuille flows subject to gradient magnetic field are analyzed. • Steady gradient magnetic fields promote the ferrofluid Couette-Poiseuille flows. • The backflow is completely suppressed and the flow separation disappears. • The gradient magnetic field enhances the effect of magnetization relaxation. • The gradient magnetic field increases magnetic stress and reduces shear stress. Inspired from the wide engineering applications of ferrofluids, we investigated the ferrofluid microchannel flows subject to a gradient magnetic field applied perpendicular to the channel walls. The ferrohydrodynamic problem encompassing the Fokker-Planck magnetization equation in a Couette-Poiseuille configuration is solved numerically. The velocity and spin profiles, vorticity, magnetization, flow rate, and stresses acting on the moving plate are examined for favorable and unfavorable field gradients, as well as the adding of different pressure gradients. We show that the steady gradient magnetic fields promote the flow of both pure Couette and Couette-Poiseuille flows in the microchannel geometry. The increment of the velocity attains 35% and the resulting volumetric flow rate increases by about 24% at the most. This phenomenon was only observed in ferrofluid flows subject to high frequency AC magnetic fields or temperature gradient field in the past. The backflow occurs in normal Couette-Poiseuille flows can be completely suppressed by the gradient fields and the flow separation disappears correspondingly. The gradient magnetic fields are able to enhance the effect of magnetization relaxation and dramatically increase the magnetic stress and reduce the shear stress by comparison with the cases subject to uniform magnetic fields, yet the tradeoff between them leads to a rise in the total tangential stress acting on the moving plate.

Heat transfer enhancement of ferrofluid flow in a solar absorber tube under non-uniform magnetic field created by a periodic current-carrying wire

A novel configuration for heat transfer enhancement in parabolic trough solar collector absorbers by the use of a ferrofluid and an external magnetic field generated by a current-carrying wire is analyzed using numerical simulation. This new configuration consists of a wire which varies its position periodically along the tube. The analysis is focused on the study of the thermal hydraulic characteristics, Nusselt number and friction factor, and the average flow patterns in the turbulent flow regime (15·103⩽Re⩽250·103). In addition, different parameters of the periodic wire are analyzed: wire pitch and position angle. Ferrofluid Fe3O4/Therminol 66 is considered for this application. Firstly, the effect of an increase on the magnetic field intensity is studied. The periodic wire configuration shows a higher increment of the Nusselt number in comparison to the straight wire for the same magnetic field increase. The results reveal that the presence of a non-uniform magnetic field generates a disturbed flow with a high velocity region near the current-carrying wire. The periodic wire configuration leads to a spatially-periodic behavior that increases the average Nusselt number and the friction factor, in comparison to a straight wire. Among the studied cases, the position angle θ=30° and the pitch length l=3D are found to provide the maximum Nusselt number (Nu = 244.25 for Re = 15000).

Analysis of Wu's slip and CNTs (single and multi-wall carbon nanotubes) in Darcy-Forchheimer mixed convective nanofluid flow with magnetic dipole: Intelligent nano-coating simulation

The analysis of viscous materials flow subject to diverse configurations with remarkable physical applications has many utilizations in the electrical, mechanical, industrial, applied physics and mathematics fields. Besides these, carbon nanotubes (CNTs) have numerous applications in energy storage, nanotechnology, chemical sensors, industry, optics, structural diverse materials and conductive plastics. Such consideration in mind, ferro-fluid flow of viscous liquid submerged in CNTs towards a stretchable surface affected by magnetic dipole interaction is addressed. Mixed convection and Darcy-Forchheimer effects are accounted. The energy relation is discussed in the presence of radiative heat flux and viscous dissipation. First and second order velocity slips are implemented at the boundary surface. The governing expressions specifying the flow are altered into ordinary ones with the assistance of appropriate similarity quantities. The obtained ordinary system is computationally tackled via Runge-Kutta 4th Order Method (RK4OM). Our obtained outcomes reveal that velocity of working fluid particles declines with an enhancement in ferromagnetic interaction parameter and Darcy-Forchheimer number. Also, behavior of temperature distribution increases more speedily for heightening of radiative parameter and Biot number. Coefficient of skin friction (surface drag force) and Nusselt number (heat transport rate) are calculated in view of important flow parameter numerically. The range of parameters are β=0.0,0.3,0.5,ε=0.1,0.5,1.0,Fr=0.1,0.5,1.0,γ1=0.0,0.5,1.0,γ2=0.0,0.1,0.2,δ=1.0,5.0,10.0,R=0.0,0.2,0.5,Bi=0.5,1.0,1.5 and.λ=0.0,1.0,3.0.

Influence of thermophysical properties on magnetite water-based ferrofluid heat transfer at sphere surface under magnetic field and thermal radiation

This theoretical study investigated the effect of thermophysical properties on Nusselt number when the magnetic field and thermal radiation are exposed to the ferrofluid flow at the lower stagnation point of a hot sphere surface. The thermo-physical properties are important mechanisms considered in the heat transfer process. Besides, the ferroparticles volume fraction is one of the variables that can enhance the thermophysical properties that are exclusively studied on thermal conductivity and thermal diffusivity of ferrofluid. Therefore, the correlation between the ferroparticles volume fraction and thermophysical properties is measured by the Pearson product-moment correlation coefficient method. The strength of association and the direction of the relationship between these pertinent variables are exhibited in ferrofluid flow composed of magnetite (Fe3O4) and water (H2O). Regression analysis is implemented to predict the effect of the ferroparticles volume fraction on the Nusselt number. The results show a positive correlation between ferroparticles volume fraction and thermal conductivity as well as between ferroparticles volume fraction and thermal diffusivity. Further-more, a simple linear regression model proposed to predict the Nusselt number when increasing the ferroparticles volume fraction resulted in statistically significant and given minuscule residuals value.

Magnetite Water Based Ferrofluid Flow and Convection Heat Transfer on a Vertical Flat Plate: Mathematical and Statistical Modelling

Magnetite Water Based Ferrofluid Flow and Convection Heat Transfer on a Vertical Flat Plate: Mathematical and Statistical Modelling

Flow and heat transfer of ferro nanofluid in a porous medium under the impact of a static magnetic field

In the present work, we turn our attention to ferrofluid flow over an expandable sheet in a porous medium. In this flow, the magnetic dipole is kept in axis at a fixed length from the center. Using similarity transformation, the governing equations of the model are transformed into a non-dimensional form. The non-dimensional coupled differential equations are solved numerically through the finite element procedure in COMSOL Multiphysics. Velocity, temperature, and concentration distributions are demonstrated for different values of non-dimensional parameters. In the presence of magnetic dipole, some of the non-dimensional parameters favor the velocity, temperature, and concentration distributions and some of them inhibit the velocity, temperature, and concentration distributions. Escalating the ratio of the stretching sheet enhances the velocity and heat transfer in the fluid and decreases the concentration in the fluid. The position of magnetic dipole from the sheet has an important role in the optimization of velocity distribution and heat transfer in the fluid.