Ferrohydrodynamic Capillary Convection

2018 ◽  
Vol 11 (2) ◽  
Author(s):  
Francisco J. Arias ◽  
Salvador A. De Las Heras
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Concentration Gradient ◽  
Deductive Reasoning ◽  
Marangoni Convection ◽  
Marangoni Effect ◽  
Magnetic Fluids ◽  
Homogeneous Magnetic Field ◽  
Gradient Field ◽  
Two Fluids

Abstract In this work, consideration is given to capillary convection on ferrofluids from the concentration gradient induced when a nonhomogeneous magnetic field is applied. It is known that mass transfer along an interface between two fluids can appear due to a gradient of the surface tension in the so-called Marangoni effect (or Gibbs–Marangoni effect). Because the surface tension is both thermal and concentration dependent, Marangoni convection can be induced by either a thermal or a concentration gradient, where in the former case, it is generally referred as thermocapillary convection. Now, it has been theoretically and experimentally demonstrated that a ferrofluid under the action of a non-homogeneous magnetic field can induce a concentration gradient of suspended magnetic nanoparticles, and also the effect of Fe3O4 nanoparticles on the surface tension has been measured. Therefore, by deductive reasoning and taking into account the above mentioned facts, it is permissible to infer ferrohydrodynamic capillary convection on magnetic fluids under the presence of a magnetic gradient field. Utilizing a simplified physical model, the phenomenon was investigated and it was found that ferrohydrodynamic-Marangoni convection could be induced with particle size in the range up to 10 nm, which is the range of magnetic fluids to escape magnetic agglomeration.

Structural Transformation of Bilayer Ferro-Foams Caused by Magnetic Field

2018 ◽  
Vol 933 ◽  
pp. 22-31
Author(s):  
Hua Qiao Dong ◽  
Jun Liang ◽  
Fu Yang Li ◽  
Cheng Chuan Zhang ◽  
Song Bao Wang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Organizational Behavior ◽  
Structural Transformation ◽  
Metal Foam ◽  
Liquid Fraction ◽  
Magnetic Interaction ◽  
Homogeneous Magnetic Field ◽  
Honeycomb Structure ◽  
Gradient Field ◽  
Minimization Principle

Previous researchers have proved that units constituting monodisperse bilayer foams can transform reversibly by changing foam liquid fraction. Structural transformation of bilayer ferro-foams caused by magnetic field is investigated in this paper. It is observed that bilayer ferro-foams transform from Tóth structure to honeycomb structure caused by liquid fraction change which attributes to foam imbibition under a uniform magnetic gradient field. In order to acquire critical structural transformation liquid fraction range, foam liquid fractions are calculated by image analysis. However, we also observed that, when applying a homogeneous magnetic field, bilayer ferro-foams can also perform this transformation at a constant liquid fraction. This phenomenon is related to energy absorption of foam system, which is induced by magnetic interaction of magnetic moments after applying a magnetic field. This self-organizational behavior of foam structure is believed to be based on energy minimization principle. This study opens possible applications in the field of metal foam preparation.

Rise of a bubble through a self-rewetting fluid under the combined influence of gravity-driven convection and Marangoni convection

2021 ◽  
pp. 095440892110487
Author(s):  
Abha Kumari ◽  
Rajat Tripathi
Keyword(s):  
Magnetic Field ◽  
Marangoni Convection ◽  
Relative Viscosity ◽  
Marangoni Effect ◽  
Gravitational Effect ◽  
Surface Tension Gradient ◽  
Polar Coordinate System ◽  
Temperature Dependent ◽  
Polar Coordinate ◽  
Gravity Driven

In this study, the influence of gravity-driven convection and Marangoni convection due to the temperature-dependent surface tension gradient on the rise of an axisymmetric bubble moving in another fluid in a self-rewetting system inside a rectangular tube is studied in the presence and absence of a magnetic field. The axisymmetric bubble (fluid 1) moving in another fluid (fluid 2) is considered immiscible. A two-dimensional cylindrical polar coordinate system has been chosen to present the sketch of the problem. Partial differential equations governing the mentioned flow situations are written and converted into non-dimensional forms and their analytical solutions have been obtained. The deformation in the bubble in the form of its radius and length is simulated. The motion of the droplet is also analysed in the microgravity region by graphing the position of the bubble. The graphical results show that there is a decrease in the contribution of the Marangoni effect and gravitational effect when the magnetic field is increased. In the absence of a magnetic field, the contribution of both the Marangoni effect and gravitational effect decrease on increasing the relative viscosity.

Investigation of the surface tension of water-based Fe3O4 magnetic fluids under magnetic field: The effect of surfactants

2021 ◽  
Vol 33 (12) ◽  
pp. 122013
Author(s):  
Qianqian Chen ◽  
Decai Li ◽  
Zhifan Yang ◽  
Zhengyan Xue ◽  
Jiangtao Hao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Magnetic Fluids ◽  
Water Based

scholarly journals On the Origin of the Magnetic Concentration Gradient Force and Its Interaction Mechanisms with Mass Transfer in Paramagnetic Electrolytes

Fluids ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 114
Author(s):  
Magne Waskaas
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Diffusion Layer ◽  
Concentration Gradient ◽  
Homogeneous Magnetic Field ◽  
Diffusion System ◽  
Gradient Force ◽  
Interaction Mechanisms ◽  
Magnetic Circuits ◽  
Magnetic Concentration

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.

Analysis of magneto rheological elastomers for energy harvesting systems

2020 ◽  
Vol 64 (1-4) ◽  
pp. 439-446
Author(s):  
Gildas Diguet ◽  
Gael Sebald ◽  
Masami Nakano ◽  
Mickaël Lallart ◽  
Jean-Yves Cavaillé
Keyword(s):  
Magnetic Field ◽  
Energy Harvesting ◽  
Shear Strain ◽  
Magnetic Induction ◽  
Magnetic Particles ◽  
Homogeneous Magnetic Field ◽  
Electrical Signal ◽  
Harvesting Systems ◽  
Dc Bias ◽  
Magneto Rheological

Magneto Rheological Elastomers (MREs) are composite materials based on an elastomer filled by magnetic particles. Anisotropic MRE can be easily manufactured by curing the material under homogeneous magnetic field which creates column of particles. The magnetic and elastic properties are actually coupled making these MREs suitable for energy conversion. From these remarkable properties, an energy harvesting device is considered through the application of a DC bias magnetic induction on two MREs as a metal piece is applying an AC shear strain on them. Such strain therefore changes the permeabilities of the elastomers, hence generating an AC magnetic induction which can be converted into AC electrical signal with the help of a coil. The device is simulated with a Finite Element Method software to examine the effect of the MRE parameters, the DC bias magnetic induction and applied shear strain (amplitude and frequency) on the resulting electrical signal.

On the Role of Marangoni Effects on the Critical Heat Flux for Pool Boiling of Binary Mixtures

1996 ◽  
Vol 118 (1) ◽  
pp. 103-109 ◽  
Author(s):  
W. R. McGillis ◽  
V. P. Carey
Keyword(s):  
Surface Tension ◽  
Heat Flux ◽  
Binary Mixtures ◽  
Critical Heat Flux ◽  
Full Range ◽  
Pool Boiling ◽  
Marangoni Effect ◽  
Restoring Force ◽  
Marangoni Effects

The Marangoni effect on the critical heat flux (CHF) condition in pool boiling of binary mixtures has been identified and its effect has been quantitatively estimated with a modified model derived from hydrodynamics. The physical process of CHF in binary mixtures, and models used to describe it, are examined in the light of recent experimental evidence, accurate mixture properties, and phase equilibrium revealing a correlation to surface tension gradients and volatility. A correlation is developed from a heuristic model including the additional liquid restoring force caused by surface tension gradients. The CHF condition was determined experimentally for saturated methanol/water, 2-propanol/water, and ethylene glycol/water mixtures, over the full range of concentrations, and compared to the model. The evidence in this study demonstrates that in a mixture with large differences in surface tension, there is an additional hydrodynamic restoring force affecting the CHF condition.

Notizen: Effect of Magnetic Field on Ascorbic Acid Oxidase Activity, I

1986 ◽  
Vol 41 (3) ◽  
pp. 355-358 ◽  
Author(s):  
V. S. Ghole ◽  
P. S. Damle ◽  
W. H.-P. Thiemann
Keyword(s):  
Magnetic Field ◽  
Ascorbic Acid ◽  
Homogeneous Magnetic Field ◽  
Acid Oxidase ◽  
High Substrate Concentration ◽  
Ascorbic Acid Oxidase ◽  
Rate Of Reaction ◽  
Substrate Concentrations ◽  
Burk Plot

A homogeneous magnetic field of 1.1 T strength exhibits a significant influence on the activity of the enzyme ascorbic acid oxidase in vitro. A Lineweaver-Burk plot of the reaction shows the typical pattern of a mixed-type inhibition, i.e. a larger rate of reaction at low substrate concentrations and a smaller rate of reaction at high substrate concentration than that of the control without magnetic field applied.

Strong Magnetic Field Effect on Surface Tension Associated with an Interfacial Magnetic Pressure

2012 ◽  
Vol 116 (33) ◽  
pp. 17676-17681 ◽  
Author(s):  
Z.H.I. Sun ◽  
X. Guo ◽  
M. Guo ◽  
C. Li ◽  
J. Vleugels ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Surface Tension ◽  
Strong Magnetic Field ◽  
Field Effect ◽  
Magnetic Field Effect ◽  
Magnetic Pressure
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