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Fluids in Magnetic/Electric Fields
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Fluids in Magnetic/Electric Fields

A special issue of Fluids (ISSN 2311-5521).

Deadline for manuscript submissions: closed (15 February 2021) | Viewed by 43229

Special Issue Editor

Prof. Dr. Ioannis Sarris

E-Mail Website
Guest Editor
Department of Mechanical Engineering, University of West Attica, Thivon 250, 12241 Aigaleo, Greece
Interests: magnetohydrodynamics; turbulence; nanofluids; convective heat transfer; biological flows; liquid metals
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fluid motion is usually affected by externally imposed electric and magnetic fields, for example, liquid metals in fusion blankets, electrolytes in batteries, biological fluids under MRI medical exams, etc. This Special Issue of Fluids is dedicated to recent advances of experimental and numerical modeling of electrically conductive fluid flows under the action of electromagnetic forces. Emphasis will be given to Newtonian and non-Newtonian fluid flows, low temperature plasmas, laminar, transitional and turbulent fluid flow, electromagnetic instabilities, electro- or magneto-rheological models, granular materials and suspensions, nanofluids and magnetic nanoparticles, crystal growth and polymers, blood and other biofluids, mixtures of fluids and particles, etc.

Prof. Dr. Ioannis Sarris
Guest Editor

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Keywords

  • Liquid metals
  • Electrolytes
  • Biological fluids
  • Electrically conductive fluid flows
  • Electromagnetic forces
  • Electromagnetic instabilities
  • Electro- or magneto-rheological models
  • Granular materials and suspensions
  • Nanofluids and magnetic nanoparticles

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Published Papers (19 papers)

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22 pages, 1076 KiB  
Article
Irreversibility Analysis for Eyring–Powell Nanoliquid Flow Past Magnetized Riga Device with Nonlinear Thermal Radiation
by Ephesus Olusoji Fatunmbi, Adeshina Taofeeq Adeosun and Sulyman Olakunle Salawu
Fluids 2021, 6(11), 416; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6110416 - 16 Nov 2021
Cited by 12 | Viewed by 1615
Abstract
The report contained in this article is based on entropy generation for a reactive Eyring–Powell nanoliquid transfer past a porous vertical Riga device. In the developed model, the impacts of viscous dissipation, thermophoresis alongside nonlinear heat radiation and varying heat conductivity are modelled [...] Read more.
The report contained in this article is based on entropy generation for a reactive Eyring–Powell nanoliquid transfer past a porous vertical Riga device. In the developed model, the impacts of viscous dissipation, thermophoresis alongside nonlinear heat radiation and varying heat conductivity are modelled into the heat equation. The dimensionless transport equations are analytically tackled via Homotopy analysis method while the computational values of chosen parameters are compared with the Galerkin weighted residual method. Graphical information of the various parameters that emerged from the model are obtained and deliberated effectively. The consequences of this study are that the temperature field expands with thermophoresis, Brownian motion and temperature ratio parameters as the modified Hartmann number compels a rise in the velocity profile. The entropy generation rises with an uplift in fluid material term as well as Biot and Eckert numbers whereas Bejan number lessens with Darcy and Eckert parameters. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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36 pages, 25698 KiB  
Article
Analysis of a Symmetrical Ferrofluid Sloshing Vibration Energy Harvester
by Nadish Anand and Richard Gould
Fluids 2021, 6(8), 295; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6080295 - 22 Aug 2021
Cited by 2 | Viewed by 2375
Abstract
Ferrofluid sloshing vibration energy harvesters use ferrofluid sloshing movement as a moving magnet between a fixed coil to induce current and, in turn, harvest energy from external excitations. A symmetric ferrofluid sloshing vibration energy harvester configuration is introduced in this study which utilizes [...] Read more.
Ferrofluid sloshing vibration energy harvesters use ferrofluid sloshing movement as a moving magnet between a fixed coil to induce current and, in turn, harvest energy from external excitations. A symmetric ferrofluid sloshing vibration energy harvester configuration is introduced in this study which utilizes four external, symmetrically placed, permanent magnets to magnetize a ferrofluid inside a tank. An external sinusoidal excitation of amplitude 1 m/s2 is imparted, and the whole system is studied numerically using a level-set method to track the sharp interface between ferrofluid and air. The system is studied for two significant length scales of 0.1 m and 0.05 m while varying the four external magnets’ polarity arrangements. All of the system configuration dimensions are parametrized with the length scale to keep the system configuration invariant with the length scale. Finally, a frequency sweep is performed, encompassing the structure’s first modal frequency and impedance matching to obtain the system’s energy harvesting characteristics. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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14 pages, 1019 KiB  
Article
Variable Energy Fluxes and Exact Relations in Magnetohydrodynamics Turbulence
by Mahendra Verma, Manohar Sharma, Soumyadeep Chatterjee and Shadab Alam
Fluids 2021, 6(6), 225; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6060225 - 15 Jun 2021
Cited by 5 | Viewed by 1982
Abstract
In magnetohydrodynamics (MHD), there is a transfer of energy from the velocity field to the magnetic field in the inertial range itself. As a result, the inertial-range energy fluxes of velocity and magnetic fields exhibit significant variations. Still, these variable energy fluxes satisfy [...] Read more.
In magnetohydrodynamics (MHD), there is a transfer of energy from the velocity field to the magnetic field in the inertial range itself. As a result, the inertial-range energy fluxes of velocity and magnetic fields exhibit significant variations. Still, these variable energy fluxes satisfy several exact relations due to conservation of energy. In this paper, using numerical simulations, we quantify the variable energy fluxes of MHD turbulence, as well as verify several exact relations. We also study the energy fluxes of Elsässer variables that are constant in the inertial range. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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16 pages, 33199 KiB  
Article
Isolation Properties of Low-Profile Magnetorheological Fluid Mounts
by Mehdi Ahmadian and Brian M. Southern
Fluids 2021, 6(4), 164; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6040164 - 19 Apr 2021
Cited by 1 | Viewed by 1588
Abstract
This study evaluates the stiffness and damping characteristics of low-profile magnetorheological (MR) fluid mounts (MRFM) to provide a better understanding of the vibration improvements offered by such mounts, as compared with conventional elastomeric mounts. It also aims at assessing how much of the [...] Read more.
This study evaluates the stiffness and damping characteristics of low-profile magnetorheological (MR) fluid mounts (MRFM) to provide a better understanding of the vibration improvements offered by such mounts, as compared with conventional elastomeric mounts. It also aims at assessing how much of the mount’s performance is due to the MR fluid and how much is due to the elastomer and steel insert that is used in MRFM. The study includes the design, analysis, fabrication, and testing of a unique class of MRFM that is suitable for the isolation of sensitive machinery and sensors. The MR fluid is compressed (squeezed) in response to dynamic force applied to the mount. The test results are compared with conventional elastomeric (rubber) mounts of the same configuration as MRFM, to highlight the changes in stiffness and damping characteristics for frequencies ranging from 1 to 35 Hz. With no current supplied, the MRFM has a slightly higher stiffness and nearly the same damping as a conventional rubber mount. The slight increase in MRFM stiffness is attributed to the MR fluid’s compressive stiffness, which is higher than the rubber. When current is supplied to the MRFM, the stiffness and damping increase significantly at lower frequencies and taper off to nearly the same level as the rubber mount at higher frequencies. Both the stiffness and damping are directly proportional to the supplied current. At the maximum current of 2 A, the MRFM has 200% higher stiffness and 700% higher damping than the rubber mount. The significantly higher damping and stiffness and the tapering off to nearly the same level as the rubber mount is quite interesting and intriguing. It indicates that MRFM delivers high damping and stiffness when needed, while significantly tapering them off when high damping and stiffness are not desirable. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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13 pages, 3624 KiB  
Article
Frequency Power Spectra of Global Quantities in Unsteady Magnetoconvection
by Sandip Das and Krishna Kumar
Fluids 2021, 6(4), 163; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6040163 - 19 Apr 2021
Viewed by 1435
Abstract
We present the results of direct numerical simulations of power spectral densities for kinetic energy, convective entropy, and heat flux for unsteady Rayleigh–Bénard magnetoconvection in the frequency space. For larger values of frequency, the power spectral densities for all the global quantities vary [...] Read more.
We present the results of direct numerical simulations of power spectral densities for kinetic energy, convective entropy, and heat flux for unsteady Rayleigh–Bénard magnetoconvection in the frequency space. For larger values of frequency, the power spectral densities for all the global quantities vary with frequency (f) as f−2. The scaling exponent is independent of Rayleigh number, Chandrasekhar’s number, and thermal Prandtl number. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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17 pages, 8875 KiB  
Article
Oscillating Magnetohydrodynamic Stokes Flow between Porous Plates with Spatiotemporally Periodic Reabsorption
by Anastasios Raptis, Christos Manopoulos, Michalis Xenos and Sokrates Tsangaris
Fluids 2021, 6(4), 156; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6040156 - 14 Apr 2021
Cited by 1 | Viewed by 1521
Abstract
The study addresses the oscillating magnetohydrodynamic (MHD) Stokes flow between two parallel plates with periodic reabsorption both spatially and temporally. Two cases are distinguished by applying either (1) transverse or (2) parallel external magnetic field. Analytical solutions of velocity and pressure are derived [...] Read more.
The study addresses the oscillating magnetohydrodynamic (MHD) Stokes flow between two parallel plates with periodic reabsorption both spatially and temporally. Two cases are distinguished by applying either (1) transverse or (2) parallel external magnetic field. Analytical solutions of velocity and pressure are derived for both cases and the effect of Womersley and Hartmann number, and the absorption coefficient is examined. The study generalizes existing literature on analytic MHD Stokes flow solutions accounting for periodic boundary conditions both in time and space. The non-oscillating non-MHD Stokes flow in a porous channel (available in the literature) is proven to be a limit of the analytic solution introduced here. The MHD effects are noticeable in flows oscillating with low or moderate frequency but are barely detectable in high-frequency flows even in the presence of strong magnetic fields. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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26 pages, 816 KiB  
Article
Magnetohydrodynamic Flow of a Bingham Fluid in a Vertical Channel: Mixed Convection
by Alessandra Borrelli, Giulia Giantesio and Maria Cristina Patria
Fluids 2021, 6(4), 154; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6040154 - 09 Apr 2021
Cited by 6 | Viewed by 2514
Abstract
In this paper, we describe our study of the mixed convection of a Boussinesquian Bingham fluid in a vertical channel in the absence and presence of an external uniform magnetic field normal to the walls. The velocity, the induced magnetic field, and the [...] Read more.
In this paper, we describe our study of the mixed convection of a Boussinesquian Bingham fluid in a vertical channel in the absence and presence of an external uniform magnetic field normal to the walls. The velocity, the induced magnetic field, and the temperature are analytically obtained. A detailed analysis is conducted to determine the plug regions in relation to the values of the Bingham number, the buoyancy parameter, and the Hartmann number. In particular, the velocity decreases as the Bingham number increases. Detailed considerations are drawn for the occurrence of the reverse flow phenomenon. Moreover, a selected set of diagrams illustrating the influence of various parameters involved in the problem is presented and discussed. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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17 pages, 57616 KiB  
Article
Micropolar Blood Flow in a Magnetic Field
by George C. Bourantas
Fluids 2021, 6(3), 133; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6030133 - 23 Mar 2021
Cited by 1 | Viewed by 2034
Abstract
In this paper we numerically solve a flow model for the micropolar biomagnetic flow (blood flow) in a magnetic field. In the proposed model we account for both electrical and magnetic properties of the biofluid and we investigate the role of microrotation on [...] Read more.
In this paper we numerically solve a flow model for the micropolar biomagnetic flow (blood flow) in a magnetic field. In the proposed model we account for both electrical and magnetic properties of the biofluid and we investigate the role of microrotation on the flow regime. The flow domain is in a channel with an unsymmetrical single stenosis, and in a channel with irregular multi-stenoses. The mathematical flow model consists of the Navier–Stokes (N–S) equations expressed in their velocity–vorticity (u–ω) variables including the energy and microrotation transport equation. The governing equations are solved by using the strong form meshless point collocation method. We compute the spatial derivatives of the unknown field functions using the discretization correction particle strength exchange (DC PSE) method. We demonstrate the accuracy of the proposed scheme by comparing the numerical results obtained with those computed using the finite element method. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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11 pages, 2593 KiB  
Article
Aspects Concerning the Fabrication of Magnetorheological Fluids Containing High Magnetization FeCo Nanoparticles
by Jon Gutiérrez, Virginia Vadillo, Ainara Gómez, Joanes Berasategi, Maite Insausti, Izaskun Gil de Muro and M. Mounir Bou-Ali
Fluids 2021, 6(3), 132; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6030132 - 23 Mar 2021
Cited by 6 | Viewed by 1671
Abstract
Recently, our collaborative work in the fabrication of a magnetorheological fluid (MRF) containing high magnetization FeCo nanoparticles (NPs, fabricated in our laboratories using the chemical reduction technique; MS = 212 Am2/kg) as magnetic fillers have resulted in a new MRF [...] Read more.
Recently, our collaborative work in the fabrication of a magnetorheological fluid (MRF) containing high magnetization FeCo nanoparticles (NPs, fabricated in our laboratories using the chemical reduction technique; MS = 212 Am2/kg) as magnetic fillers have resulted in a new MRF with superior performance up to 616.7 kA/m. The MRF had a yield stress value of 2729 Pa and good reversibility after a demagnetization process. This value competes with the best ones reported in the most recent literature. Nevertheless, the fabrication process of this type of fluid is not an easy task since there is a strong trend to the aggregation of the FeCo NPs due to the strong magnetic dipolar interaction among them. Thus, now we present the analysis of some aspects concerning the fabrication process of our FeCo NPs containing MRF, mainly the type of surfactant used to cover those NPs (oleic acid or aluminium stearate) and its concentration, and the procedure followed (mechanical and/or ultrasound stirring) to achieve a good dispersion of those magnetic fillers within the fluid. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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22 pages, 27222 KiB  
Article
Heat and Mass Transfer Analysis on Magneto Micropolar Fluid Flow with Heat Absorption in Induced Magnetic Field
by Md. Mohidul Haque
Fluids 2021, 6(3), 126; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6030126 - 19 Mar 2021
Cited by 5 | Viewed by 2168
Abstract
Heat and mass transfer due to a magneto micropolar fluid flow along a semi-infinite vertical plate bounded by a porous medium are investigated in presence of induced magnetic field. In case of cooling flow, heat and mass fluxes from the plate are subjected [...] Read more.
Heat and mass transfer due to a magneto micropolar fluid flow along a semi-infinite vertical plate bounded by a porous medium are investigated in presence of induced magnetic field. In case of cooling flow, heat and mass fluxes from the plate are subjected to be constant under the action of a constant heat sink. Mathematical model related to the problem is developed from the basis of studying magnetohydrodynamics (MHD) for both lighter and heavier particles. Dimensionless model of momentum, microrotation, induction, energy and concentration equations are solved simultaneously by the explicit scheme of finite difference technique. According to the obtained stability and convergence criteria of this transient flow, very negligible time step (Δt = 0.002) compared to the existing works has been taken to perform the numerical computation. Quantities of chief physical interest of the flow as shear stress, couple stress, current density, Nusselt number and Sherwood number are also studied here. The numerically computed results are compared with published results of available research works. Interestingly an excellent agreement is found with finite difference solutions in both explicit and implicit schemes. In order to discuss the physical aspects of the problem, the flow variables for different values of associated parameters are illustrated in graphs. Finally, important findings of the study are listed as concluding remarks. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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11 pages, 10026 KiB  
Article
Heat Transfer Study of the Ferrofluid Flow in a Vertical Annular Cylindrical Duct under the Influence of a Transverse Magnetic Field
by Panteleimon A. Bakalis, Polycarpos K. Papadopoulos and Panayiotis Vafeas
Fluids 2021, 6(3), 120; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6030120 - 15 Mar 2021
Cited by 3 | Viewed by 2129
Abstract
We studied the laminar fully developed ferrofluid flow and heat transfer phenomena of an otherwise magnetic fluid into a vertical annular duct of circular cross-section and uniform temperatures on walls which were subjected to a transverse external magnetic field. A computational algorithm was [...] Read more.
We studied the laminar fully developed ferrofluid flow and heat transfer phenomena of an otherwise magnetic fluid into a vertical annular duct of circular cross-section and uniform temperatures on walls which were subjected to a transverse external magnetic field. A computational algorithm was used, which coupled the continuity, momentum, energy, magnetization and Maxwell’s equations, accompanied by the appropriate conditions, using the continuity–vorticity–pressure (C.V.P.) method and a non-uniform grid. The results were obtained for different values of field strength and particles’ volumetric concentration, wherein the effects of the magnetic field on the ferrofluid flow and the temperature are revealed. It is shown that the axial velocity distribution is highly affected by the field strength and the volumetric concentration, the axial pressure gradient depends almost linearly on the field strength, while the heat transfer significantly increases due to the generated secondary flow. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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15 pages, 8937 KiB  
Article
On the Origin of the Magnetic Concentration Gradient Force and Its Interaction Mechanisms with Mass Transfer in Paramagnetic Electrolytes
by Magne Waskaas
Fluids 2021, 6(3), 114; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6030114 - 11 Mar 2021
Cited by 4 | Viewed by 2272
Abstract
The objective of this work is to analyze the origin of the magnetic concentration gradient force. The force will be studied in a diffusion system where a paramagnetic electrolyte diffuses through a thin, inert membrane under the influence of a homogeneous magnetic field. [...] Read more.
The objective of this work is to analyze the origin of the magnetic concentration gradient force. The force will be studied in a diffusion system where a paramagnetic electrolyte diffuses through a thin, inert membrane under the influence of a homogeneous magnetic field. The force will be analyzed using the theory of magnetic circuits, i.e., by the concept of minimum reluctance principles. In addition, based on some previous studies, it will be discussed whether the minimum reluctance principle can be applied to mass transfer into and out of the diffusion layer at electrode/electrolyte interfaces. The results show that the magnetic concentration gradient force arises as a consequence of the minimum reluctance principle. Applied to the diffusion system, the magnetic concentration gradient force arises in the membrane as a consequence of the concentration gradient and hence, the reluctance gradient. The force acts on the flow in such a way that the reluctance in the membrane is minimized. The force implies two interaction mechanisms: attraction of the paramagnetic electrolyte flowing into the membrane in order to decrease the reluctance, and hindrance of the paramagnetic electrolyte flowing out of the membrane in order to hinder an increase in the reluctance. Based on previous studies, it is shown that the minimum reluctance principle can be applied to mass transfer into or out of the diffusion layer at electrode/electrolyte interfaces as well. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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19 pages, 7215 KiB  
Article
Biomagnetic Fluid Flow and Heat Transfer Study of Blood with Gold Nanoparticles over a Stretching Sheet in the Presence of Magnetic Dipole
by Jahangir Alam, Ghulam Murtaza, Efstratios Tzirtzilakis and Mohammad Ferdows
Fluids 2021, 6(3), 113; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6030113 - 10 Mar 2021
Cited by 21 | Viewed by 2620
Abstract
In this study, we examined the biomagnetic flow and heat transfer of an incompressible electrically conductive fluid (blood) containing gold nanoparticles over a stretching sheet in the presence of a magnetic dipole. In this problem, both principles of magnetohydrodynamics (MHD) and ferrohydrodynamics (FHD) [...] Read more.
In this study, we examined the biomagnetic flow and heat transfer of an incompressible electrically conductive fluid (blood) containing gold nanoparticles over a stretching sheet in the presence of a magnetic dipole. In this problem, both principles of magnetohydrodynamics (MHD) and ferrohydrodynamics (FHD) were adopted. Biot number and slip and suction parameters were taken into consideration. The nonlinear partial differential equations were transformed into ordinary differential equations by implementing similarity transformations. The numerical solution was attained by utilizing the bvp4c function technique in MATLAB R2018b software. The influence of pertinent parameters involved in this model, such as ferromagnetic parameter, magnetic field parameter, Grashof number, Eckert number, suction parameter, Biot number, slip parameter and Prandtl number, on the dimensionless velocity, temperature, skin friction and heat transfer rate were analyzed numerically and are represented graphically. Among the numerous results, it was observed that increment in ferromagnetic parameter and Prandtl number results in decrement of the velocity and temperature, respectively. For some values of the parameters, a comparison with the results of other documents in the literature is also made. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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25 pages, 1112 KiB  
Article
Magnetic Helicity and the Geodynamo
by John V. Shebalin
Fluids 2021, 6(3), 99; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6030099 - 02 Mar 2021
Cited by 7 | Viewed by 1512
Abstract
We present theoretical and computational results in magnetohydrodynamic turbulence that we feel are essential to understanding the geodynamo. These results are based on a mathematical model that focuses on magnetohydrodynamic (MHD) turbulence, but ignores compressibility and thermal effects, as well as imposing model-dependent [...] Read more.
We present theoretical and computational results in magnetohydrodynamic turbulence that we feel are essential to understanding the geodynamo. These results are based on a mathematical model that focuses on magnetohydrodynamic (MHD) turbulence, but ignores compressibility and thermal effects, as well as imposing model-dependent boundary conditions. A principal finding is that when a turbulent magnetofluid is in quasi-equilibrium, the magnetic energy in the internal dipole component is equal to the magnetic helicity multiplied by the dipole wavenumber. In the case of the Earth, measurement of the exterior magnetic field gives us, through boundary conditions, the internal poloidal magnetic field. The connection between magnetic helicity and dipole field in the liquid core then gives us the toroidal part of the internal dipole field and a model value of 3 mT for the average core dipole magnetic field. Here, we present the theoretical analysis and numerical simulations that lead to these conclusions. We also test an earlier assertion that differential oblateness may be related to dipole alignment, and while there is an effect, rotation appears to be far more important. In addition, the relationship between dipole quasi-stationarity, broken ergodicity and broken symmetry is clarified. Lastly, we discuss how inertial waves in a rotating magnetofluid can affect dipole alignment. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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19 pages, 1807 KiB  
Article
An Optimized Method for 3D Magnetic Navigation of Nanoparticles inside Human Arteries
by Evangelos Karvelas, Christos Liosis, Andreas Theodorakakos, Ioannis Sarris and Theodoros Karakasidis
Fluids 2021, 6(3), 97; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6030097 - 01 Mar 2021
Cited by 8 | Viewed by 1802
Abstract
A computational method for optimum magnetic navigation of nanoparticles that are coated with anticancer drug inside the human vascular system is presented in this study. For this reason a 3D carotid model is employed. The present model use Computational Fluid Dynamics [...] Read more.
A computational method for optimum magnetic navigation of nanoparticles that are coated with anticancer drug inside the human vascular system is presented in this study. For this reason a 3D carotid model is employed. The present model use Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) techniques along with Covariance Matrix Adaptation (CMA) evolution strategy for the evaluation of the optimal values of the gradient magnetic field. Under the influence of the blood flow the model evaluates the effect of different values of the gradient magnetic field in order to minimize the distance of particles from a pre-described desired trajectory. Results indicate that the diameter of particles is a crucial parameter for an effective magnetic navigation. The present numerical model can navigate nanoparticles with diameter above 500 nm with an efficiency of approximately 99%. It is found that the velocity of the blood seems to play insignificant role in the navigation process. A reduction of 25% in the inlet velocity leads the particles only 3% closer to the desired trajectory. Finally, the computational method is more efficient as the diameter of the vascular system is minimized because of the weak convective flow. Under a reduction of 50% in the diameter of the carotid artery the computational method navigate the particles approximately 75% closer to the desired trajectory. The present numerical model can be used as a tool for the determination of the parameters that mostly affect the magnetic navigation method. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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18 pages, 1390 KiB  
Article
Use of Nanoparticle Enhanced Phase Change Material for Cooling of Surface Acoustic Wave Sensor
by Mohammad Yaghoub Abdollahzadeh Jamalabadi
Fluids 2021, 6(1), 31; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6010031 - 08 Jan 2021
Cited by 8 | Viewed by 2414
Abstract
The use of resonators, filters, interdigital transducers (IDT) and stable sources in electronic industry is widespread today. One of the most used filters are the surface acoustic wave (SAW) type, which is mostly based on Rayleigh waves propagation on the surface. On the [...] Read more.
The use of resonators, filters, interdigital transducers (IDT) and stable sources in electronic industry is widespread today. One of the most used filters are the surface acoustic wave (SAW) type, which is mostly based on Rayleigh waves propagation on the surface. On the other hand, the use of Phase change materials (PCMs) is considered as a heat sink method in the field of thermal cooling of electronic circuits. Recent development in heat transfer is obtained by nanoparticle-enhanced PCM (NEPCM), which is a result of combining nanoparticles with PCMs. Increase of thermal conductivity of NEPCM in comparison with common PCM enhances the heat transfer rate. The aim of the current study is thermal management of SAW for the application of high frequency heating by phase change material. Melting of NEPCMs inside a rectangular cavity next to the SAW cell is used for the cooling purpose. Free convection heat transfer of a NEPCMs in an square cavity is modeled throughout the mass and momentum. Energy governing equations are solved by using the finite element method. Electrohydrodynamic (EHD) forces exist in natural convection heat transfer within the fluid part of the enclosure. The results also show that the NEPCM causes heat transfer improvement up to 10%. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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19 pages, 5713 KiB  
Article
Asymmetrical Thermal Boundary Condition Influence on the Flow Structure and Heat Transfer Performance of Paramagnetic Fluid-Forced Convection in the Strong Magnetic Field
by Lukasz Pleskacz, Elzbieta Fornalik-Wajs and Sebastian Gurgul
Fluids 2020, 5(4), 246; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids5040246 - 16 Dec 2020
Viewed by 2099
Abstract
Continuous interest in space journeys opens the research fields, which might be useful in non-terrestrial conditions. Due to the lack of the gravitational force, there will be a need to force the flow for mixing or heat transfer. Strong magnetic field offers the [...] Read more.
Continuous interest in space journeys opens the research fields, which might be useful in non-terrestrial conditions. Due to the lack of the gravitational force, there will be a need to force the flow for mixing or heat transfer. Strong magnetic field offers the conditions, which can help to obtain the flow. In light of this origin, presented paper discusses the dually modified Graetz-Brinkman problem. The modifications were related to the presence of the magnetic field influencing the flow and asymmetrical thermal boundary condition. Dimensionless numerical analysis was performed, and two dimensionless numbers (magnetic Grashof number and magnetic Richardson number) were defined for paramagnetic fluid flow. The results revealed the heat transfer enhancement due to the strong magnetic field influence accompanied by possible but not essential flow structure modifications. On the other hand, the flow structure changes can be utilized to prevent the solid particles’ sedimentation. The explanation of the heat transfer enhancement including energy budget and vorticity distribution was presented. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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12 pages, 5461 KiB  
Article
Experimental Study on Water Electrolysis Using Cellulose Nanofluid
by Dongnyeok Choi and Kwon-Yeong Lee
Fluids 2020, 5(4), 166; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids5040166 - 28 Sep 2020
Cited by 2 | Viewed by 3448
Abstract
Hydrogen energy is considered to be a future energy source due to its higher energy density as compared to renewable energy and ease of storage and transport. Water electrolysis is one of the most basic methods for producing hydrogen. KOH and NaOH, which [...] Read more.
Hydrogen energy is considered to be a future energy source due to its higher energy density as compared to renewable energy and ease of storage and transport. Water electrolysis is one of the most basic methods for producing hydrogen. KOH and NaOH, which are currently used as electrolytes for water electrolysis, have strong alkalinity. So, it cause metal corrosion and can be serious damage when it is exposed to human body. Hence, experiments using cellulose nanofluid (CNF, C6H10O5) as an electrolyte were carried out to overcome the disadvantages of existing electrolytes and increase the efficiency of hydrogen production. The variables of the experiment were CNF concentration, anode material, voltage applied to the electrode, and initial temperature of the electrolyte. The conditions showing the optimal hydrogen production efficiency (99.4%) within the set variables range were found. CNF, which is not corrosive and has high safety, can be used for electrolysis for a long period of time because it does not coagulate and settle over a long period of time unlike other inorganic nanofluids. In addition, it shows high hydrogen production efficiency. So, it is expected to be used as a next-generation water electrolysis electrolyte. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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Review

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44 pages, 8408 KiB  
Review
Physical Background, Computations and Practical Issues of the Magnetohydrodynamic Pressure Drop in a Fusion Liquid Metal Blanket
by Sergey Smolentsev
Fluids 2021, 6(3), 110; https://0-doi-org.brum.beds.ac.uk/10.3390/fluids6030110 - 08 Mar 2021
Cited by 31 | Viewed by 3661
Abstract
In blankets of a fusion power reactor, liquid metal (LM) breeders, such as pure lithium or lead-lithium alloy, circulate in complex shape blanket conduits for power conversion and tritium breeding in the presence of a strong plasma-confining magnetic field. The interaction of the [...] Read more.
In blankets of a fusion power reactor, liquid metal (LM) breeders, such as pure lithium or lead-lithium alloy, circulate in complex shape blanket conduits for power conversion and tritium breeding in the presence of a strong plasma-confining magnetic field. The interaction of the magnetic field with induced electric currents in the breeder results in various magnetohydrodynamic (MHD) effects on the flow. Of them, high MHD pressure losses in the LM breeder flows is one of the most important feasibility issues. To design new feasible LM breeding blankets or to improve the existing blanket concepts and designs, one needs to identify and characterize sources of high MHD pressure drop, to understand the underlying physics of MHD flows and to eventually define ways of mitigating high MHD pressure drop in the entire blanket and its sub-components. This article is a comprehensive review of earlier and recent studies of MHD pressure drop in LM blankets with a special focus on: (1) physics of LM MHD flows in typical blanket configurations, (2) development and testing of computational tools for LM MHD flows, (3) practical aspects associated with pumping of a conducting liquid breeder through a strong magnetic field, and (4) approaches to mitigation of the MHD pressure drop in a LM blanket. Full article
(This article belongs to the Special Issue Fluids in Magnetic/Electric Fields)
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