Control of Vortex Shedding From a Bluff Body Using Imposed Magnetic Field

2006 ◽  
Vol 129 (5) ◽  
pp. 517-523 ◽  
Author(s):  
Sintu Singha ◽  
K. P. Sinhamahapatra ◽  
S. K. Mukherjea
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Steady Flow ◽  
Transverse Magnetic Field ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Reynolds Numbers ◽  
Transverse Magnetic ◽  
Staggered Grid ◽  
The Magnetic Field

The two-dimensional incompressible laminar viscous flow of a conducting fluid past a square cylinder placed centrally in a channel subjected to an imposed transverse magnetic field has been simulated to study the effect of a magnetic field on vortex shedding from a bluff body at different Reynolds numbers varying from 50 to 250. The present staggered grid finite difference simulation shows that for a steady flow the separated zone behind the cylinder is reduced as the magnetic field strength is increased. For flows in the periodic vortex shedding and unsteady wake regime an imposed transverse magnetic field is found to have a considerable effect on the flow characteristics with marginal increase in Strouhal number and a marked drop in the unsteady lift amplitude indicating a reduction in the strength of the shed vortices. It has further been observed, that it is possible to completely eliminate the periodic vortex shedding at the higher Reynolds numbers and to establish a steady flow if a sufficiently strong magnetic field is imposed. The necessary strength of the magnetic field, however, depends on the flow Reynolds number and increases with the increase in Reynolds number. This paper describes the algorithm in detail and presents important results that show the effect of the magnetic field on the separated wake and on the periodic vortex shedding process.

Measurements of helical flow of a strong electrolyte with and without a transverse magnetic field

1963 ◽  
Vol 16 (2) ◽  
pp. 197-208
Author(s):  
Laurence R. Boedeker ◽  
Eugene E. Covert
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Hydrochloric Acid ◽  
Secondary Flow ◽  
Transverse Magnetic Field ◽  
Reynolds Numbers ◽  
Transverse Magnetic ◽  
Helical Flow ◽  
Experimental Results ◽  
Strong Electrolyte

This note describes the slow magneto-hydrodynamic flow of hydrochloric acid in a helix. At very low Reynolds number a transverse magnetic field is found to retard the flow in agreement with existing theory and with existing experimental results obtained using mercury. At higher Reynolds numbers where secondary flow in a helix becomes important the transverse magnetic field is found to reduce this secondary flow.

The annihilation of a two-dimensional jet by a transverse magnetic field

1967 ◽  
Vol 30 (1) ◽  
pp. 65-82 ◽  
Author(s):  
H. K. Moffatt ◽  
J. Toomre
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Transverse Magnetic Field ◽  
Magnetic Interaction ◽  
Transverse Magnetic ◽  
Magnetic Reynolds Number ◽  
Two Dimensional ◽  
Dimensionless Numbers ◽  
Order Unity ◽  
The Magnetic Field

The effect of an applied transverse magnetic field on the development of a two-dimensional jet of incompressible fluid is examined. The jet is prescribed in terms of its mass flux ρQ0 and its lateral scale d at an initial section x = 0. The three dimensionless numbers characterizing the problem are a Reynolds number R = Q0/ν, a magnetic Reynolds number Rm = μσQ0, and a magnetic interaction parameter N = σB20d2/ρQ0, where ρ represents density, σ conductivity, μ permeability and B0 applied field strength, and it is assumed that \[ R_m \ll 1,\quad R\gg 1,\quad N\ll 1. \] It is shown that when M2 = RN [Gt ] 1, an inviscid treatment is appropriate, and that the effect of the magnetic field is then to destroy the jet momentum within a distance of order N−1 in the downstream direction. A general solution for inviscid development is obtained, and it is shown that a large class of velocity profiles (though not all of them) are self-preserving.When M2 [Lt ] 1, it is shown that the viscous similarity solution obtained by Moreau (1963a, b) is relevant. This solution is re-derived and re-interpreted; it implies that the jet momentum is destroyed within a distance of order $R^{\frac{1}{4}}N^{-\frac{3}{4}}$ in the downstream direction.Some further aspects of the jet annihilation problem are qualitatively discussed in § 4, viz. the nature of the overall flow field, the effect of the presence of distant boundaries, the effect of increasing Rm to order unity and greater, and the effect of oblique injection. Finally the development of a jet of conducting fluid into a nonconducting environment is considered; in this case the jet is not stopped by the magnetic field unless a return path outside the fluid for the induced current is available.

scholarly journals Теплообмен при смешанной конвекции расплава соли в присутствии магнитных полей

2019 ◽  
Vol 45 (10) ◽  
pp. 27
Author(s):  
И.А. Беляев ◽  
Д.А. Бирюков ◽  
А.В. Котляр ◽  
Е.А. Белавина ◽  
П.А. Сардов ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Temperature Fluctuations ◽  
Reynolds Numbers ◽  
Transverse Magnetic ◽  
Statistical Characteristics ◽  
Transfer Coefficients ◽  
Gravitational Flow ◽  
Heat Transfer Coefficients ◽  
The Magnetic Field

The results of an experimental study of the salt melt downflow in a uniformly heated pipe under the influence of a strong transverse magnetic field are presented. The changes of heat transfer coefficients and statistical characteristics of temperature fluctuations under the influence of the magnetic field are investigated. The peculiarities of the transition of the viscous-gravitational flow in the viscous-inertial-gravitational flow at Reynolds numbers (Re=3000-5000) under the influence of the magnetic field (Ha=17) were studied.

Vortex Shedding From a Bluff Body Adjacent to a Plane Sliding Wall

1991 ◽  
Vol 113 (3) ◽  
pp. 384-398 ◽  
Author(s):  
M. P. Arnal ◽  
D. J. Goering ◽  
J. A. C. Humphrey
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Solid Wall ◽  
Reynolds Numbers ◽  
Careful Examination ◽  
Recirculation Region ◽  
Stream Velocity ◽  
Flow Past ◽  
Lower Reynolds Number

The characteristics of the flow around a bluff body of square cross-section in contact with a solid-wall boundary are investigated numerically using a finite difference procedure. Previous studies (Taneda, 1965; Kamemoto et al., 1984) have shown qualitatively the strong influence of solid-wall boundaries on the vortex-shedding process and the formation of the vortex street downstream. In the present study three cases are investigated which correspond to flow past a square rib in a freestream, flow past a rib on a fixed wall and flow past a rib on a sliding wall. Values of the Reynolds number studied ranged from 100 to 2000, where the Reynolds number is based on the rib height, H, and bulk stream velocity, Ub. Comparisons between the sliding-wall and fixed-wall cases show that the sliding wall has a significant destabilizing effect on the recirculation region behind the rib. Results show the onset of unsteadiness at a lower Reynolds number for the sliding-wall case (50 ≤ Recrit ≤100) than for the fixed-wall case (Recrit≥100). A careful examination of the vortex-shedding process reveals similarities between the sliding-wall case and both the freestream and fixed-wall cases. At moderate Reynolds numbers (Re≥250) the sliding-wall results show that the rib periodically sheds vortices of alternating circulation in much the same manner as the rib in a freestream; as in, for example, Davis and Moore [1982]. The vortices are distributed asymmetrically downstream of the rib and are not of equal strength as in the freestream case. However, the sliding-wall case shows no tendency to develop cycle-to-cycle variations at higher Reynolds numbers, as observed in the freestream and fixed-wall cases. Thus, while the moving wall causes the flow past the rib to become unsteady at a lower Reynolds number than in the fixed-wall case, it also acts to stabilize or “lock-in” the vortex-shedding frequency. This is attributed to the additional source of positive vorticity immediately downstream of the rib on the sliding wall.

Magnetohydrodynamic Viscous Flow Separation in a Channel With Constrictions

2003 ◽  
Vol 125 (6) ◽  
pp. 952-962 ◽  
Author(s):  
C. Midya ◽  
G. C. Layek ◽  
A. S. Gupta ◽  
T. Ray Mahapatra
Keyword(s):  
Magnetic Field ◽  
Flow Separation ◽  
Separation Zone ◽  
Transverse Magnetic ◽  
Mhd Equations ◽  
Staggered Grid ◽  
Solution Technique ◽  
Computational Domain ◽  
Pressure Poisson Equation ◽  
The Magnetic Field

An analysis is made of the flow of an electrically conducting fluid in a channel with constrictions in the presence of a uniform transverse magnetic field. A solution technique for governing magnetohydrodynamic (MHD) equations in primitive variable formulation is developed. A coordinate stretching is used to map the long irregular geometry into a finite computational domain. The governing equations are discretized using finite difference approximations and the well-known staggered grid of Harlow and Welch is used. Pressure Poisson equation and pressure-velocity correction formulas are derived and solved numerically. It is found that the flow separates downstream of the constriction. With increase in the magnetic field, the flow separation zone diminishes in size and for large magnetic field, the separation zone disappears completely. Wall shear stress increases with increase in the magnetic field strength. It is also found that for symmetrically situated constrictions on the channel walls, the critical Reynolds number for the flow bifurcation (i.e., flow asymmetry) increases with increase in the magnetic field.

Comparison of the Effects of Bias Voltage and Transverse Magnetic Field on the Macro-Particles Distribution on the Surface of TiN Films Prepared by Arc Ion Plating

2011 ◽  
Vol 337 ◽  
pp. 300-306
Author(s):  
Wen Chang Lang
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Field Intensity ◽  
Magnetic Field Intensity ◽  
Transverse Magnetic ◽  
Key Factor ◽  
Influence Parameter ◽  
Two Parameters ◽  
Influence Degree ◽  
The Magnetic Field

The object of this article is to make research on the influence of transverse magnetic field and pulse bias on macro-particles on the surface of film, find the systematic law and analyze the influence law and reasons of the two parameters (transverse magnetic field and pulse bias), according to the mechanism of arc spot movement and the interaction between macro-particles and plasma. Moreover, this article aims at seeking the most important influence parameter and comparing the effect of the two parameters. Research in this paper indicates that: the key factor is the magnetic field controlled arc spot movement, because the influence of magnetic field on reducing macro-particles is much larger than bias, and the influence degree of bias on macro-particles varies with the magnetic field intensity; action of bias is obvious under the condition of low magnetic field intensity, but as the magnetic field intensity increases, its action becomes weaker and weaker; besides, purification effect of bias on particles in larger size is better than on particles in smaller size.

Analytical Analysis of Magneto-hydrodynamic (MHD) Transient Flow Past a Suddenly Started Infinite Vertical Plate With Thermal Radiation and Ramped Wall Temperature

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
N. Ahmed ◽  
M. Dutta
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Reynolds Number ◽  
Transverse Magnetic Field ◽  
Wall Temperature ◽  
Vertical Plate ◽  
Transverse Magnetic ◽  
Viscous Drag ◽  
Fluid Temperature ◽  
Infinite Vertical Plate

An exact solution to the problem of a magnetohydrodynamic viscous, incompressible free convective flow of an electrically conducting, Newtonian non-Gray fluid past a suddenly started infinite vertical plate with ramped wall temperature in presence of appreciable radiation heat transfer and uniform transverse magnetic field is presented. The fluid is assumed to be optically thin and the magnetic Reynolds number is considered small enough to neglect the induced hydromagnetic effects. The resulting system of the equations governing the flow is solved by adopting Laplace Transform technique in closed form. Detailed computations of the influence of Hartmann number, radiation conduction parameter Q, Reynolds number Re and time t on the variations in the fluid velocity, fluid temperature, and skin friction and Nusselt number at the plate are demonstrated graphically. The results show that the imposition of the transverse magnetic field retards the fluid motion and causes the viscous drag at the plate to fall. The investigation simulates that the fluid temperature drops and the rate of heat transfer from the plate to the fluid gets increased for increasing Reynolds number.

Article

1998 ◽  
Vol 76 (7) ◽  
pp. 507-513
Author(s):  
O Bolina ◽  
J R Parreira
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Ground State ◽  
Linear Chain ◽  
Critical Value ◽  
Transverse Magnetic ◽  
The State ◽  
Xy Model ◽  
The Magnetic Field

We show that the ground state of the xy model (ferromagnetic orantiferromagnetic) in a transverse magnetic field h --- for any spin value, in any dimension --- is the state with all spins aligned antiparallel to the field when h is greater than some critical value hc. In particular, for the spin-1/2 linear chain, we study the behavior of correlations as functions of the magnetic field. PACS Nos.: 75.10Jm and 64.60.Cm

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