scholarly journals Structure formation in suspensions under uniform electric or magnetic field

2021 ◽  
Author(s):  
Konstantinos Manikas ◽  
Georgios G. Vogiatzis ◽  
Markus Hütter ◽  
Patrick D. Anderson
Keyword(s):  
Magnetic Field ◽  
External Field ◽  
Structure Formation ◽  
Brownian Dynamics ◽  
Volume Fraction ◽  
Structural Evolution ◽  
Thermal Fluctuations ◽  
Branch Points ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

AbstractThe structure formation of particles with induced dipoles dispersed in a viscous fluid, under a spatially and temporarily uniform external electric or magnetic field, is investigated by means of Brownian Dynamics simulations. Dipole–dipole interactions forces, excluded volume forces and thermal fluctuations are accounted for. The resulting structures are characterized in terms of average orientation of their inter-particle vectors (second Legendre polynomial), network structure, size of particle clusters, anisotropy of the gyration tensor of every cluster and existence of (cluster) percolation. The magnitude of the strength of the external field and the volume fraction of particles are varied and the structural evolution of the system is followed in time. The results show that the characteristic timescale calculated from the interaction of only two dipoles is also valid for the collective dynamics of many-particle simulations. In addition, the magnitude of the strength of the external field in the range of values we investigate influences only the magnitude of the deviations around the average behavior. The main characteristics (number density of branch-points and thickness of branches) of the structure are mainly affected by the volume fraction. The possibility of 3D printing these systems is explored. While the paper provides the details about the case of an electric field, all results presented here can be translated directly into the case of a magnetic field and paramagnetic particles.

scholarly journals Structure evolution of suspensions under time-dependent electric or magnetic field

2021 ◽  
Author(s):  
Konstantinos Manikas ◽  
Markus Hütter ◽  
Patrick D. Anderson
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Brownian Dynamics ◽  
Thermal Fluctuations ◽  
Time Dependent ◽  
Structure Evolution ◽  
Strength Increase ◽  
Large Rotation ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

AbstractThe effect of time-dependent external fields on the structures formed by particles with induced dipoles dispersed in a viscous fluid is investigated by means of Brownian Dynamics simulations. The physical effects accounted for are thermal fluctuations, dipole-dipole and excluded volume interactions. The emerging structures are characterised in terms of particle clusters (orientation, size, anisotropy and percolation) and network structure. The strength of the external field is increased in one direction and then kept constant for a certain amount of time, with the structure formation being influenced by the slope of the field-strength increase. This effect can be partially rationalized by inhomogeneous time re-scaling with respect to the field strength, however, the presence of thermal fluctuations makes the scaling at low field strength inappropriate. After the re-scaling, one can observe that the lower the slope of the field increase, the more network-like and the thicker the structure is. In the second part of the study the field is also rotated instantaneously by a certain angle, and the effect of this transition on the structure is studied. For small rotation angles ($$\theta \le 20^{{\circ }}$$ θ ≤ 20 ∘ ) the clusters rotate but stay largely intact, while for large rotation angles ($$\theta \ge 80^{{\circ }}$$ θ ≥ 80 ∘ ) the structure disintegrates and then reforms, due to the nature of the interactions (parallel dipoles with perpendicular inter-particle vector repel each other). For intermediate angles ($$20<\theta <80^{{\circ }}$$ 20 < θ < 80 ∘ ), it seems that, during rotation, the structure is altered towards a more network-like state, as a result of cluster fusion (larger clusters). The details provided in this paper concern an electric field, however, all results can be projected into the case of a magnetic field and paramagnetic particles.

scholarly journals Influence of size polydispersity on magnetic field tunable structures in magnetic nanofluids containing superparamagnetic nanoparticles.

2021 ◽  
Author(s):  
Dillip Kumar Mohapatra ◽  
Philip James Camp ◽  
John Philip
Keyword(s):  
Magnetic Field ◽  
Particle Size ◽  
Light Scattering ◽  
Optical Microscopy ◽  
Brownian Dynamics ◽  
Phase Contrast ◽  
Superparamagnetic Nanoparticles ◽  
Magnetic Nanofluids ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

We probe the influence of particle size polydispersity on field-induced structures and structural transitions in magnetic fluids (ferrofluids) using phase contrast optical microscopy, light scattering and Brownian dynamics simulations. Three...

Brownian Dynamics Simulations of Magnetic Nanoparticles Captured in Strong Magnetic Field Gradients

2016 ◽  
Vol 121 (1) ◽  
pp. 801-810 ◽  
Author(s):  
Zhiyuan Zhao ◽  
Isaac Torres-Díaz ◽  
Camilo Vélez ◽  
David Arnold ◽  
Carlos Rinaldi
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Strong Magnetic Field ◽  
Brownian Dynamics ◽  
Field Gradients ◽  
Magnetic Field Gradients ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

Brownian Dynamics Simulations of Aggregation Phenomena in a Magnetic Particle Suspension With an Alternating Magnetic Field (Relationship Between the Aggregate Structure and the Heat Production)

2018 ◽  
Author(s):  
Seiya Suzuki ◽  
Akira Satoh ◽  
Muneo Futamura
Keyword(s):  
Magnetic Field ◽  
Heat Production ◽  
Brownian Dynamics ◽  
Magnetic Particle ◽  
Particle Interaction ◽  
Alternating Magnetic Field ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations ◽  
The Magnetic Field ◽  
Aggregation Phenomena

The present study addresses physical phenomena of a suspension composed of magnetic spherical particles in an alternating magnetic field in order to elucidate particle aggregation phenomena and their influence on heat production. For this objective, we have performed Brownian dynamics simulations in a variety of circumstances of the magnetic field strength and frequency of an alternating magnetic field, and the magnetic dipole-dipole interaction strength. As in a time-independent uniform external magnetic field, large aggregates are formed in the case of strong magnetic particle-particle interactions. However, these clusters exhibit completely different behaviors that are dependent on the frequency of an alternating magnetic field. If the frequency is significantly high, then the viscous torque is the dominant factor, so that the formation of the clusters is not significantly influenced by the time-dependent magnetic field. If the frequency is significantly low, the magnetic field have a significant effect on the rotational motion of the particles, so that the formation of the cluster is dependent on which factor dominates the particle motion between the applied magnetic field and the magnetic particle-particle interaction. If the magnetic interaction is more dominant than the external field, stable chain-like clusters are formed in the field direction, and the magnetic particle-particle interaction induces a significant delay for the moments inclining in the alternating magnetic field direction. This behavior gives rise to a hysteresis loop with a larger area and therefore a large heating effect is obtained.

Brownian Dynamics Simulations of Colloidal Dispersion Composed of Ferromagnetic Spherocylinder Particles in a Simple Shear Flow (For the Case of an Applied Magnetic Field Normal to the Shear Plane)

2009 ◽  
Author(s):  
Ryo Hayasaka ◽  
Yasuhiro Sakuda ◽  
Akira Satoh
Keyword(s):  
Magnetic Field ◽  
Brownian Dynamics ◽  
Magnetic Particle ◽  
Colloidal Dispersion ◽  
Magnetic Interactions ◽  
Simple Shear Flow ◽  
Particle Interactions ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations ◽  
The Magnetic Field

We have investigated aggregate structures and rheological properties of a colloidal dispersion composed of ferromagnetic spherocylinder particles with a magnetic moment along the particle axis direction, by means of Brownian dynamics simulations. In concrete, we have attempted to clarify the influences of the flow field, magnetic field strength, magnetic interactions between particles and volumetric fraction of particles. In order to discuss quantitatively the internal structures of clusters, we have concentrated our attention on the radial distribution and orientational distribution functions. The present results are compared with those of the theoretical analysis for dilute dispersions and also non-dilute dispersions; the results for the latter were obtained by means of the mean-field approximation, which magnetic particle-particle interactions can be taken into account. Some important results are summarized as follows. For the case of the magnetic field strength and magnetic interactions between particles are more dominant than the viscous forces due to a simple shear flow, chain-like like clusters are formed along the magnetic field direction, although they are slightly tilted to the flow direction. When magnetic particle-particle interactions become over a certain value, such cluster formation leads to a significant increase in the viscosity of the dispersion.

scholarly journals Characterization of structures of particles

2020 ◽  
Vol 126 (7) ◽  
Author(s):  
Konstantinos Manikas ◽  
Georgios G. Vogiatzis ◽  
Patrick D. Anderson ◽  
Markus Hütter
Keyword(s):  
Brownian Dynamics ◽  
Initial Structure ◽  
Branch Points ◽  
The One ◽  
Dynamics Simulations ◽  
The Individual ◽  
Brownian Dynamics Simulations ◽  
Individual Particles ◽  
Image Analysis Techniques

Abstract A methodology for the characterization of particle structures, especially networks, is developed. This scheme combines 3D image analysis techniques with graph theory tools for the simplification of a structure of thick agglomerates to its skeleton. The connectivity graph of the initial structure is compared with the one of the corresponding skeleton, as a measure of simplification. Examples are used to illustrate the effectiveness of our scheme. Particle structures obtained by Brownian Dynamics simulations are characterized qualitatively and quantitatively. Instead of looking at the characteristics of the structure at the level of the individual particles or neighborhoods of particles, our scheme results in quantitative measures of the network, e.g. the number density of branch-points, the degree of branch-points, and the thickness and the orientation of the branches.

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