scholarly journals On unsteady hydromagnetic flows of a dusty viscous fluid between two oscillating plates

1989 ◽  
Vol 2 (1) ◽  
pp. 13-31 ◽  
Author(s):  
Lokenath Debnath ◽  
A. K. Ghosh
Keyword(s):  
Magnetic Field ◽  
Early Stage ◽  
Fluid Velocity ◽  
Fluid Motion ◽  
Unsteady Motion ◽  
Spherical Particles ◽  
Lower Plate ◽  
Time Period ◽  
Time Periods ◽  
The Magnetic Field

A study is made of the unsteady motion of an incompressible viscous conducting fluid with embedded small spherical particles bounded by two infinite rigid non-conducting plates. The operational method derives exact solutions for the fluid and the particle velocities and the wall shear stress. The quantitative evaluation of these results is considered when the two plates oscillate in phase but with different frequencies. The results are shown graphically for different values of the time period of oscillations of the plates which represent the cases: (i) the lower plate oscillates with time period less than the upper, (ii) both the plates oscillate with the same time period, (iii) the lower plate oscillates with time period greater than the upper. The magnetic field damps the fluid motion for all values of the time period of oscillations of the plates. When the time periods are small, i.e., when the plates oscillate with high frequency, the fluid motion is retarded by the particles. However, when the plates oscillate with larger time periods (smaller frequencies), the fluid velocity is increased by the presence of the particles at the early stage of the motion, and this effect persists until the equilibrium is reached when the particles exert their influence to resist the flow. The drag on the plate, which is evaluated numerically for the lower plate oscillating with large time period, depends on the ratio of the time periods of the oscillating plates. If the ratio of the time periods is not equal to unity, the drag on the plate, irrespective of the values of the magnetic field, oscillates with larger amplitude compared to its value when the ratio of the time periods is equal to unity. Further, for the ratio of the time periods less than or equal to unity and for any fixed values of the magnetic field, the drag increases by the presence of the particles after a time t≈1.2 which is the upper time limit for the non-equilibrium stress-value to exist. In a similar situation, a reverse effect, i.e., the decrease of the drag with increasing particle concentration, is found for the ratio of the time periods being greater than unity.

scholarly journals Heat Induction by Viscous Dissipation Subjected to Symmetric and Asymmetric Boundary Conditions on a Small Oscillating Flow in a Microchannel

Symmetry ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 499 ◽  
Author(s):  
Chih Tso ◽  
Chee Hor ◽  
Gooi Chen ◽  
Chee Kok
Keyword(s):  
Temperature Field ◽  
Prandtl Number ◽  
Boundary Conditions ◽  
Viscous Dissipation ◽  
Fluid Velocity ◽  
Fluid Motion ◽  
Lower Plate ◽  
Brinkman Number ◽  
Energy Equations ◽  
Oscillation Rate

The heat induced by viscous dissipation in a microchannel fluid, due to a small oscillating motion of the lower plate, is investigated for the first time. The methodology is by applying the momentum and energy equations and solving them for three cases of standard thermal boundary conditions. The first two cases involve symmetric boundary conditions of constant surface temperature on both plates and both plates insulated, respectively. The third case has the asymmetric conditions that the lower plate is insulated while the upper plate is maintained at constant temperature. Results reveal that, although the fluid velocity is only depending on the oscillation rate of the plate, the temperature field for all three cases show that the induced heating is dependent on the oscillation rate of the plate, but strongly dependent on the parameters Brinkman number and Prandtl number. All three cases prove that the increasing oscillation rate or Brinkman number and decreasing Prandtl number, when it is less than unity, will significantly increase the temperature field. The present model is applied to the synovial fluid motion in artificial hip implant and results in heat induced by viscous dissipation for the second case shows remarkably close agreement with the experimental literature.

scholarly journals Numerical Study of Paramagnetic Elliptical Microparticles in Curved Channels and Uniform Magnetic Fields

Micromachines ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 37 ◽  
Author(s):  
Christopher Sobecki ◽  
Jie Zhang ◽  
Cheng Wang
Keyword(s):  
Magnetic Field ◽  
Numerical Study ◽  
Spherical Particles ◽  
Biological Applications ◽  
Arbitrary Lagrangian Eulerian ◽  
Curved Channel ◽  
Radial Migration ◽  
Wall Distance ◽  
Curved Channels ◽  
The Magnetic Field

We numerically investigated the dynamics of a paramagnetic elliptical particle immersed in a low Reynolds number Poiseuille flow in a curved channel and under a uniform magnetic field by direct numerical simulation. A finite element method, based on an arbitrary Lagrangian-Eulerian approach, analyzed how the channel geometry, the strength and direction of the magnetic field, and the particle shape affected the rotation and radial migration of the particle. The net radial migration of the particle was analyzed after executing a π rotation and at the exit of the curved channel with and without a magnetic field. In the absence of a magnetic field, the rotation is symmetric, but the particle-wall distance remains the same. When a magnetic field is applied, the rotation of symmetry is broken, and the particle-wall distance increases as the magnetic field strength increases. The causation of the radial migration is due to the magnetic angular velocity caused by the magnetic torque that constantly changes directions during particle transportation. This research provides a method of magnetically manipulating non-spherical particles on lab-on-a-chip devices for industrial and biological applications.

Evolution of the Earth’s polar wind escape from mid-Archean to present

2020 ◽  
Author(s):  
Kristina Kislyakova ◽  
Colin Johnstone ◽  
Manuel Scherf ◽  
Helmut Lammer ◽  
Mats Holmström ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Direct Simulation Monte Carlo ◽  
Opening Angle ◽  
Polar Wind ◽  
Oxygen Ions ◽  
Atmospheric Escape ◽  
The Earth ◽  
Time Period ◽  
Upper Limits ◽  
The Magnetic Field

<p>The evolution of habitable conditions on Earth is tightly connected to the evolution of its atmosphere which, in turn, is strongly influenced by atmospheric escape. We investigate the evolution of the the polar wind outflow from the magnetic cusps which is the dominant escape mechanism on the Earth. We perform Direct Simulation Monte Carlo (DSMC) simulations and estimate the upper limits on escape rates from the Earth's cusps starting from three gigayears ago (Ga) to present assuming the present-day composition of the atmosphere. We perform one additional simulation with a lower mixing ratio of oxygen of 1% to account for the conditions shortly after the Great Oxydation Event (GOE). We account for the evolution of the magnetic field of the Earth by adjusting the polar opening angle and the location of the magnetosphere's substellar point.</p><p>Our results present an upper limit on the escape rates, but they indicate that polar wind escape rates for nitrogen and oxygen ions were likely much higher in the past.  We estimate the maximum total loss rates due to polar wind of 2.0x10<sup>18</sup> kg and 5.2x10<sup>17</sup> kg for oxygen and nitrogen, respectively. According to our results, the main factors that governed the polar wind outflow in the considered time period are the evolution of the XUV radiation of the Sun and the atmosphere's composition. The evolution of the Earth's magnetic field plays a less important role. We conclude that although the atmosphere with the present-day composition can survive the escape due to polar wind outflow, a higher level of CO<sub>2</sub> between 3.0 and 2.0 Ga is likely necessary to reduce the escape.</p>

Numerical Analysis of Electromagnetic Levitation Employing Meshless Method Based on Weighted Least Square Method

2015 ◽  
Vol 15 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Shuhei Matsuzawa ◽  
Kenta Mitsufuji ◽  
Yurika Miyake ◽  
Katsuhiro Hirata ◽  
Fumikazu Miyasaka
Keyword(s):  
Magnetic Field ◽  
Meshless Method ◽  
Fluid Motion ◽  
Electromagnetic Levitation ◽  
Least Square Method ◽  
Least Square ◽  
Weighted Least Square ◽  
Frequency Magnetic Field ◽  
Thermo Physical Properties ◽  
The Magnetic Field

AbstractElectromagnetic levitation is a kind of magnetohydrodynamic phenomena which is useful to measure the thermo-physical properties of pure metals under high temperature. However, this phenomenon is complicated and detailed mechanisms of this phenomenon have not been clarified yet. This study proposes the meshless method based on weighted least square method for the analysis of electromagnetic levitation. In this study, the fluid motion equation and the magnetic field equation are coupled by this method. The behavior of a molten metal under high-frequency magnetic field is calculated by this method.

scholarly journals Numerical Analysis of Heat Transfer of Eyring Powell Fluid Using Double Stratification of Magneto-Hydrodynamic Boundary Layer Flow

2020 ◽  
pp. 91-108
Author(s):  
Wekesa Waswa Simon ◽  
Winifred Nduku Mutuku
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Thermal Stratification ◽  
Fluid Velocity ◽  
Double Stratification ◽  
Hydrodynamic Boundary Layer ◽  
Layer Flow ◽  
The Magnetic Field

Heat transfer fluids play a vital role in many engineering and industrial sectors such as power generation, chemical production, air-conditioning, transportation and microelectronics. Aim: To numerically investigate the effect of double stratification on magneto-hydrodynamic boundary layer flow and heat transfer of an Eyring-Powell fluid. Study Design: Eyring-Powell fluid is one of the non-Newtonian fluid that possess different characteristics thus different mathematical models have been formulated to describe such fluids by appropriate substitution into Navier-Stoke’s equations. The challenging complexity and the nature of the resultant equations are of great interest hence attract many investigations. Place and Duration of Study: Department of Mathematics and Actuarial Science, Kenyatta University, Nairobi, Kenya between December 2019 and October 2020. Methodology: The resultant nonlinear equations are transformed to linear differential equations by introducing appropriate similarity transformations. The resulting equations are solved numerically by simulating the predictor-corrector (P-C) method in matlab ode113. The results are graphically depicted and analysed to illustrate the effects of magnetic field, thermophoresis, thermal stratification, solutal stratification, material fluid parameters and Grashoff number on the fluid velocity, temperature, concentration, local Sherwood number and local Nusselt number. Results: The results show that increasing the magnetic field strength, thermophoresis, thermal stratification and solutal stratification lead to a decrease in the fluid velocity, temperature, Sherwood number, Nusselt number and skin friction while an increase in the magnetic field strength, thermal stratification, solutal stratification, and thermophoresis increases the fluid concentration. Conclusion: The parameters in this study can be varied to enhance heat ejection of Eyring-Powell fluid and applied in industries as a coolant or heat transfer fluid.

scholarly journals Computation of the magnetic potential induced by a collection of spherical particles using series expansions

2020 ◽  
Vol 54 (4) ◽  
pp. 1073-1109
Author(s):  
Stéphane Balac ◽  
Laurent Chupin ◽  
Sébastien Martin
Keyword(s):  
Magnetic Field ◽  
Magnetic Potential ◽  
Point Of View ◽  
Spherical Particles ◽  
Main Magnetic Field ◽  
Minimal Distance ◽  
Metallic Particles ◽  
Scalar Magnetic Potential ◽  
The Magnetic Field ◽  
Made In

In Magnetic Resonance Imaging there are several situations where, for simulation purposes, one wants to compute the magnetic field induced by a cluster of small metallic particles. Given the difficulty of the problem from a numerical point of view, the simplifying assumption that the field due to each particle interacts only with the main magnetic field but does not interact with the fields due to the other particles is usually made. In this paper we investigate from a mathematical point of view the relevancy of this assumption and provide error estimates for the scalar magnetic potential in terms of the key parameter that is the minimal distance between the particles. A special attention is paid to obtain explicit and relevant constants in the estimates. When the “non-interacting assumption” is deficient, we propose to compute a better approximation of the magnetic potential by taking into account pairwise magnetic field interactions between particles that enters in a general framework for computing the scalar magnetic potential as a series expansion.

scholarly journals An electromagnetic arrayed pump to create arbitrary velocity profiles in fluid

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Seyed Peyman Hashemi ◽  
Mohammad Reza Karafi ◽  
Mohammad Hossein Sadeghi ◽  
Vahid Rezaei Esfedan
Keyword(s):  
Magnetic Field ◽  
Fluid Velocity ◽  
Rectangular Channel ◽  
Velocity Profiles ◽  
List Type ◽  
Finite Element Software ◽  
Electromagnetic Pump ◽  
Naoh Solution ◽  
Arbitrary Velocity ◽  
The Magnetic Field

AbstractThe present paper is conducted to develop a new structure of an electromagnetic pump capable of controlling the magnetic field in a rectangular channel. Common electromagnetic pumps do not create uniform velocity profiles in the cross-section of the channel. In these pumps, an M-shape profile is created since the fluid velocity in the vicinity of the walls is higher than that in its center. Herein, the arbitrary velocity profiles in the electromagnetic pump are generated by introducing an arrayed structure of the coils in the electromagnetic pump and implementing 3D numerical simulation in the finite element software COMSOL. The dimensions of the rectangular channel are 5.5 × 150 mm2. Moreover, the magnetic field is provided using a core with an arrayed structure made of low-carbon iron, as well as five couples of coils. 20% NaoH solution is utilized as the fluid (conductivity: 40 S/m). The arrayed pump is fabricated and experimentally created an arbitrary velocity profile. The pressure of the pump in every single array is 12 Pa and the flow rate is equal to 3375 mm3/s. According to the results, there is a good agreement between the experimental test carried out herein and the simulated models.Article highlights This is the first time that the idea of arrayed electromagnetic pump is presented. This pump uses a special arrayed core with coils; by controlling the current of each coil and the direction of the currents, the magnetic field under the core could be adjusted. By changing the magnetic field at any position in the width of the channel, the Lorentz force alters, which leads to different velocity and pressure profiles. Using COMSOL multiphysics software, the electromagnetic pump was simulated in real size compared to the experimental model. Subsequently, the simulation model was verified and different velocity profiles were generated by activation and deactivation of different coils. The pressure and velocity curves and contours were extracted. The experimental setup was manufactured and assembled. NaOH solution was utilized as the fluid. Afterwards, different modes of coil activations were investigated and the pressure and velocity profiles of the pump were calculated.

scholarly journals A MAGNETOHYDRODYNAMIC STUDY OF BEHAVIOR IN AN ELECTROLYTE FLUID USING NUMERICAL AND EXPERIMENTAL SOLUTIONS

2012 ◽  
Vol 11 (1-2) ◽  
pp. 53
Author(s):  
L. P. Aoki ◽  
M. G. Maunsell ◽  
H. E. Schulz
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Fluid Velocity ◽  
Flow Analysis ◽  
Test Chamber ◽  
Cross Product ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Vector Density ◽  
The Magnetic Field

This article examines a rectangular closed circuit filled with an electrolyte fluid, known as macro pumps, where a permanent magnet generates a magnetic field and electrodes generate the electric field in the flow. The fluid conductor moves inside the circuit under magnetohydrodynamic effect (MHD). The MHD model has been derived from the Navier Stokes equation and coupled with the Maxwell equations for Newtonian incompressible fluid. Electric and magnetic components engaged in the test chamber assist in creating the propulsion of the electrolyte fluid. The electromagnetic forces that arise are due to the cross product between the vector density of induced current and the vector density of magnetic field applied. This is the Lorentz force. Results are present of 3D numerical MHD simulation for newtonian fluid as well as experimental data. The goal is to relate the magnetic field with the electric field and the amounts of movement produced, and calculate de current density and fluid velocity. An u-shaped and m-shaped velocity profile is expected in the flows. The flow analysis is performed with the magnetic field fixed, while the electric field is changed. Observing the interaction between the fields strengths, and density of the electrolyte fluid, an optimal configuration for the flow velocity isdetermined and compared with others publications.

On the theory of magneto-sound double simple waves

2008 ◽  
Vol 74 (4) ◽  
pp. 455-471 ◽  
Author(s):  
DAVY D. TSKHAKAYA ◽  
HOMAYOON ESHRAGHI
Keyword(s):  
Magnetic Field ◽  
Wave Solution ◽  
Blow Up ◽  
Initial Conditions ◽  
Fluid Velocity ◽  
Simple Wave ◽  
Initial Distribution ◽  
Relativistic Plasmas ◽  
The One ◽  
The Magnetic Field

AbstractA two-dimensional double simple wave solution is given for both weakly and highly magnetized non-relativistic plasmas moving across the magnetic field. The dependence of the density and the magnetic field on the two independent phases, namely, components of the fluid velocity, is derived. It is shown that initial spatial distributions must satisfy a definite equation whose solution determines a special category for initial conditions. The time of blow up for any fixed value of the pair phase is found. A large general class of solutions for initial distributions is obtained. For any chosen initial distribution, the physical plane of flow at any instant of time splits into two regions, one forbidden and the other permitted. These regions are obtained numerically at a typical time for a special initial distribution. For this double wave solution, differential equations for streamlines and fluid trajectories are derived. Only for the simplest cases can the corresponding curves be completely integrated and these are given in this paper. The results are qualitatively similar to the one-dimensional case derived by Stenflo and Shukla.

scholarly journals Convective mechanism of amplification and structuring of magnetic fields

2012 ◽  
Vol 8 (S294) ◽  
pp. 137-142
Author(s):  
A. V. Getling ◽  
V. V. Kolmychkov ◽  
O. S. Mazhorova
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Incompressible Fluid ◽  
Spatial Scales ◽  
Fluid Motion ◽  
Horizontal Layer ◽  
Field Lines ◽  
The Magnetic Field ◽  
Initial Magnetic Field ◽  
Peripheral Regions

AbstractMagnetoconvection in a horizontal layer of incompressible fluid is simulated numerically. The initial magnetic field is assumed to be uniform and horizontal. The interaction of quasi-ordered cellular convection with the magnetic field is shown to be able to produce bipolar (and also diverse more complex) configurations of a substantially amplified magnetic field. The operation of this mechanism, which can be regarded as a modification of the mechanism suggested by Tverskoi (1966), is controlled by the very topology of the cellular flow, should be manifest on various spatial scales, and does not require strong initial fields. Magnetic configurations develop both in the central parts of convection cells, where circulatory fluid motion “winds” magnetic field lines, and in the network formed by their peripheral regions due to the “sweeping” of magnetic field lines.

Sign in / Sign up

Export Citation Format

Share Document