scholarly journals Magneto-thermocapillary-buoyancy convection in a square cavity with partially active vertical walls

2019 ◽  
Vol 23 (6 Part A) ◽  
pp. 3433-3442
Author(s):  
Emtinene Lajnef ◽  
Walid Hassen ◽  
Lioua Kolsi ◽  
Abdullah Al-Rashed ◽  
Rajab Al-Sayegh ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Side Wall ◽  
Active Part ◽  
Buoyancy Convection ◽  
Side Walls ◽  
Vertical Walls ◽  
Higher Temperature ◽  
The Right ◽  
Volume Method

Effect of magnetic field on combined surface tension and buoyancy convection in an enclosure with partially active vertical walls is investigated numerically. The active part of the left side wall is at a higher temperature than the active part of the right side wall. The bottom and the inactive parts of the side walls are adiabatic and capillary forces occur at the top free surface. The governing equations are discretized by the finite volume method. The results are obtained for Pr = 0.054, 0 ? Ha ? 100, 0 ? Ma ? 10000, and 2.104 ? Gr ? 2.106. The flow structure and temperature field were presented by streamlines and isotherms respectively. The surface tension effect of is manifested by increasing Marangoni number. The application of magnetic field was found to control the flow and to oppose the capillary effects.

Magnetic Field Effect on Mixed Convection in Lid-Driven Trapezoidal Cavities Filled With a Cu–Water Nanofluid With an Aiding or Opposing Side Wall

2016 ◽  
Vol 8 (3) ◽  
Author(s):  
Ali J. Chamkha ◽  
Muneer A. Ismael
Keyword(s):  
Magnetic Field ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Magnetic Field Effect ◽  
Side Wall ◽  
Cu Nanoparticles ◽  
Suppression Effect ◽  
Side Walls ◽  
The Right ◽  
The Magnetic Field

The present study investigates mixed convection inside a Cu–water nanofluid filled trapezoidal cavity under the effect of a constant magnetic field. The mixed convection is achieved by the action of lid-driving of the right hot inclined side wall in the aiding or the opposing direction. The left inclined side wall is fixed and kept isothermal at a cold temperature. The horizontal top and bottom walls are fixed and thermally insulated. The magnetic field is imposed horizontally. The problem is formulated using the stream function-vorticity procedure and solved numerically using an efficient upwind finite-difference method. The studied parameters are: the Richardson number Ri = (0.01–10), the Hartman number Ha = (0–100), the volume fraction of Cu nanoparticles φ = (0–0.05), and the inclination angle of side walls Φ = (66 deg, 70 deg, 80 deg). The results have shown that the suppression effect of the magnetic field for the aiding case is greater than that for the opposing case. Meanwhile, the enhancement of the Nusselt number due to the presence of the Cu nanoparticles is greater for opposing lid-driven case.

Particle Transport in a Turbulent Square Duct Flow With an Imposed Magnetic Field

2013 ◽  
Author(s):  
Rui Liu ◽  
Surya P. Vanka ◽  
Brian G. Thomas
Keyword(s):  
Magnetic Field ◽  
Particle Transport ◽  
Continuous Flow ◽  
Duct Flow ◽  
Deposition Rates ◽  
Square Duct ◽  
Side Walls ◽  
Volume Method ◽  
The Magnetic Field ◽  
A Current

In this paper we study the particle transport and deposition in a turbulent square duct flow with an imposed magnetic field using Direct Numerical Simulations (DNS) of the continuous flow. A magnetic field induces a current and the interaction of this current with the magnetic field generates a Lorentz force which brakes the flow and modifies the flow structure. A second-order accurate finite volume method in time and space is used and implemented on a GPU. Particles are injected at the entrance to the duct continuously and their rates of deposition on the duct walls are computed for different magnetic field strengths. Because of the changes to the flow due to the magnetic field, the deposition rates are different on the top and bottom walls compared to the side walls. This is different than in a non-MHD square duct flow, where quadrant (and octant) symmetry is obtained.

Three-dimensional MHD duct flows with strong transverse magnetic fields. Part 2. Variable-area rectangular ducts with conducting sides

1971 ◽  
Vol 46 (4) ◽  
pp. 657-684 ◽  
Author(s):  
J. S. Walker ◽  
G. S. S. Ludford ◽  
J. C. R. Hunt
Keyword(s):  
Magnetic Field ◽  
Boundary Layers ◽  
Three Dimensional ◽  
Side Wall ◽  
Transverse Magnetic ◽  
Reverse Direction ◽  
Wall Boundary ◽  
Strong Transverse ◽  
Side Walls ◽  
The Magnetic Field

In this paper the general analysis, developed in part 1, of three-dimensional duct flows subject to a strong transverse magnetic field is used to examine the flow in diverging ducts of rectangular cross-section. It is found that, with the magnetic field parallel to one pair of the sides, the essential problem is the analysis of the boundary layers on these (side) walls. Assuming that they are highly conducting and that those perpendicular to the magnetic field are non-conducting, the flow is found to have some interesting properties: if the top and bottom walls diverge, the side walls remaining parallel, then an O(1) velocity overshoot occurs in the side-wall boundary layers; but if the top and bottom walls remain parallel, the side walls diverging, these boundary layers have conventional velocity profiles. The most interesting flows occur when both pairs of walls diverge, when it is found that large, 0(M½), velocities occur in the side-wall boundary layers, either in the direction of the mean flow or in the reverse direction, depending on the geometry of the duct and the external electric circuit!The mathematical analysis involves the solution of a formidable integral equation which, however, does have analytic solutions for some special types of duct.

scholarly journals Effect of Magnetic Field on Mixed Convection Heat Transfer in a Lid-Driven Square Cavity

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
N. A. Bakar ◽  
A. Karimipour ◽  
R. Roslan
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Convection Heat Transfer ◽  
Simple Algorithm ◽  
Square Cavity ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Vertical Walls ◽  
Cold Walls ◽  
Volume Method

The effect of magnetic field on fluid flow and heat transfer in two-dimensional square cavity is analyzed numerically. The vertical walls are insulated; the top wall is maintained at cold temperature, Tc while the bottom wall is maintained at hot temperature, Th where Th>Tc. The dimensionless governing equations are solved using finite volume method and SIMPLE algorithm. The streamlines and isotherm plots and the variation of Nusselt numbers on hot and cold walls are presented.

scholarly journals Free convection in wavy porous enclosures with non-uniform temperature boundary conditions filled with a nanofluid: Buongiorno’s mathematical model

2017 ◽  
Vol 21 (3) ◽  
pp. 1183-1193 ◽  
Author(s):  
Mikhail Sheremet ◽  
Ioan Pop
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Amplitude Ratio ◽  
Side Wall ◽  
Transfer Rates ◽  
Temperature Boundary ◽  
Phase Deviation ◽  
Flow Heat ◽  
Vertical Walls ◽  
The Right

In the present work, the influence of the amplitude ratio, phase deviation, and undulation number on natural convection in a wavy-walled enclosures differentially heated and filled with a water based nanofluid is studied. The upper and bottom walls are wavy with several undulations. The sinusoidal distribution of temperature is imposed at the vertical walls. The flow, heat, and mass transfer are calculated by solving governing equations for embody the conservation of total mass, momentum, thermal energy, and nanoparticles, taking into account the Darcy-Boussinesq-Buongiorno approximation with second order finite difference method in ?stream function-temperature-concentration? formulation. Results are presented in the form of streamlines, isotherm, and isoconcentration contours, and distributions of the average Nusselt number for the different values of the amplitude ratio of the sinusoidal temperature on the right side wall to that on the left side wall (? = 0-1), phase deviation (? = 0-?), and undulation number (? = 1-4). It has been found that variations of the undulation number allow to control the heat and mass transfer rates. Moreover, an increase in the undulation number leads to an extension of the non-homogeneous zones.

scholarly journals Natural convection in a square cavity with partially active vertical walls: Time-periodic boundary condition

2006 ◽  
Vol 2006 ◽  
pp. 1-16 ◽  
Author(s):  
N. Nithyadevi ◽  
P. Kandaswamy ◽  
S. Sivasankaran
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Control Volume ◽  
Active Regions ◽  
Governing Equations ◽  
Square Cavity ◽  
Side Walls ◽  
Vertical Walls ◽  
Volume Method ◽  
Time Periodic

A numerical study of transient natural convection in a square cavity with partly thermally active side walls is introduced. The thermally active regions of the side walls are periodic in time. Top and bottom of the cavity are adiabatic. Nine different positions of the thermally active zones are considered. The governing equations are solved using control volume method with power-law scheme. The results are obtained for various values of amplitude, period, and Grashof numbers ranging from104–106and different thermally active situations. It is found that the average heat transfer increases by increasing amplitude forP=1,5, and decreasing forP=3. The average Nusselt number behaves nonlinearly as a function of period.

The effect of an external magnetic field on natural convection in an inclined rectangular enclosure

2007 ◽  
Vol 221 (12) ◽  
pp. 1609-1622 ◽  
Author(s):  
M C Ece ◽  
E Büyük
Keyword(s):  
Magnetic Field ◽  
Natural Convection ◽  
Differential Quadrature Method ◽  
Convection Flow ◽  
Rectangular Enclosure ◽  
Aspect Ratios ◽  
Inclination Angles ◽  
Side Walls ◽  
Vertical Walls ◽  
The Magnetic Field

Steady, laminar, natural-convection flow in the presence of a magnetic field of an arbitrary direction in an inclined rectangular enclosure with isothermal vertical walls and adiabatic horizontal walls was considered. The governing equations were solved numerically for the stream function, vorticity, and temperature ratio using the differential quadrature method for various Grashof and Hartman numbers and three different magnetic field directions, aspect ratios, and inclination angles. Counter-clockwise inclination of the enclosure enhances the convection whereas the clockwise inclination retards it. The magnetic field applied normal to the side walls are more effective for square and tall enclosures whereas the magnetic field applied parallel to the side walls is more effective for shallow enclosures.

scholarly journals Influence of the Longitudinal Magnetic Field on the Formation of the Bead in Narrow Gap Gas Tungsten Arc Welding

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1351 ◽  
Author(s):  
Xiaoxia Jian ◽  
Hebao Wu
Keyword(s):  
Magnetic Field ◽  
Arc Welding ◽  
Molten Pool ◽  
Longitudinal Magnetic Field ◽  
Side Wall ◽  
Experimental Results ◽  
Narrow Gap ◽  
Welding Arc ◽  
Maximum Value ◽  
Side Walls

The oscillation arc assisted by an extra alternating longitudinal magnetic field (LMF) in narrow gap tungsten arc welding is proved to be effective in avoiding welding defects due to insufficient fusion at the side walls in joining thick wall plates. The behavior of the welding arc and molten pool under the LMF is simulated to reveal the influence of the LMF on the formation of a uniform penetration weld bead. A unified mathematical model was developed for the narrow gap tungsten arc welding including the plasma arc, molten pool, electrode, and their interactions. Under the LMF, the whole welding arc is deflected and oscillates between the two side walls. When the magnetic-field strength is larger than 6 mT, the axis of the arc deflects to the side wall; the maximum value of heat flux at the bottom decreases by one-half, and the maximum value at the side wall is increased by a factor of ten. On the other hand, under the LMF, the forces acting on the molten pool are changed; the fluid flow pattern is helpful to increase the heat transferred to the side walls. The model is validated by experimental results. Both the percentage deviations of the simulation weld penetration at the side wall and at the bottom from the experimental results are lower than 10%.

Numerical analysis of effect of magnetic field on combined surface tension and buoyancy driven convection in partially heated open enclosure

2015 ◽  
Vol 25 (8) ◽  
pp. 1793-1817 ◽  
Author(s):  
N. Nagarajan ◽  
Hakan F. Öztop ◽  
A. Shamadhani Begum ◽  
Khaled Al-Salem
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Control Volume ◽  
Simple Algorithm ◽  
Thermocapillary Flow ◽  
Content Type ◽  
Buoyancy Driven Convection ◽  
External Forces ◽  
Volume Method ◽  
Effect Of Surface

Purpose – The purpose of the paper is to investigate the effects of magnetic field on the flow driven by the combined mechanism of buoyancy and thermocapillary flow in an open enclosure with localized heating from below and symmetrical cooling from the sides. Design/methodology/approach – The governing equations are discretized by the control volume method with power-law scheme and solved numerically by SIMPLE algorithm for the pressure-velocity coupling together with under-relaxation technique. Findings – In this work, it is observed that, the average Nusselt number, decreases with an increase of Hartmann number Ha, and increases with increase of Prandtl and Grashof number. At large Marangoni number Ma, a prominent secondary eddies are observed at the top of the enclosure due to the effect of surface tension. Originality/value – The study combines many external forces on thermocapillary flow.

Electromagnetic Pump With Thin Metal Walls

1994 ◽  
Vol 116 (2) ◽  
pp. 298-302
Author(s):  
N. Ma ◽  
T. J. Moon ◽  
J. S. Walker
Keyword(s):  
Magnetic Field ◽  
Boundary Layers ◽  
Metal Flow ◽  
Side Wall ◽  
Transverse Magnetic ◽  
Thin Metal ◽  
Total Flow ◽  
Electromagnetic Pump ◽  
Liquid Metal Flow ◽  
Side Walls

This paper treats a liquid-metal flow in a rectangular duct with a strong, uniform, transverse magnetic field and with thin metal walls, except for two finite-length, perfectly conducting electrodes in the side walls, which are parallel to the magnetic field. There are large velocities inside the boundary layers adjacent to the thin metal side walls, but not inside the layers adjacent to the electrodes. Upstream and downstream of the electrodes, a significant fraction of the total flow leaves and enters the side-wall boundary layers, respectively. For the particular duct treated here, the fully developed side layers, which carry 38.8 percent of the total flow, are realized at a distance of three characteristic lengths from the ends of the electrodes.

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