Departure of microscopic friction from macroscopic drag in molecular fluid dynamics

Hanasaki, Itsuo; Fujiwara, Daiki

doi:10.1063/1.4943045

Cited by 6 publications

(4 citation statements)

References 40 publications

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“…In other words, the time span to use eqn (1) is easily satised for a shortest frame interval of the camera when the system of interest is particles in a liquid. 54,55 When the particle has spherical shape and the system is sufficiently dilute, the Stokes-Einstein relation predicts the diffusion coefficient D SE in bulk as follows:…”

Section: Generalized Diffusion Coefficient and Nite Datamentioning

confidence: 99%

Characterization of aqueous cellulose nanofiber dispersions from microscopy movie data of Brownian particles by trajectory analysis

Motohashi

Hanasaki

2019

Nanoscale Adv.

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Section: Generalized Diffusion Coefficient and Nite Datamentioning

confidence: 99%

Characterization of aqueous cellulose nanofiber dispersions from microscopy movie data of Brownian particles by trajectory analysis

Motohashi

Hanasaki

2019

Nanoscale Adv.

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“…m P = m for type (i) and m P = N C m for type (ii)) is sufficiently larger than the mass of the solvent molecule m [33]. Note that if the size and the mass of the nanoparticle are comparable to those of fluid molecules, the mass may play important role in the dynamics of the nanoparticle [41,42].…”

Section: Nanoparticle Type (Ii): Clustermentioning

confidence: 98%

Negative thermophoresis of nanoparticles interacting with fluids through a purely-repulsive potential

Tsuji

Iseki

Hanasaki

2017

J. Phys.: Condens. Matter

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Thermophoretic forces acting on nanoparticles are investigated using molecular dynamics simulation. We assume the Lennard-Jones (LJ) potential for the interaction between fluid molecules. On the other hand, the interaction between the nanoparticle and the surrounding fluid molecules are assumed to be either LJ or Weeks-Chandler-Andersen (WCA) potential, where the latter is purely-repulsive. The effect of the interaction potential on the thermophoretic force is investigated for various situations. It is found that the thermophoretic force basically acts in the direction from the hotter side to the colder side of the nanoparticle. However, when the surrounding fluid is in the liquid phase, the force acts in the reversed direction for the case of the WCA potential. It is clarified that the sign reversal is caused by the different structures observed in the distribution of repulsive forces acting on the nanoparticle.

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“…Galliero和Volz [30] 的研究表明, 当m P /m > 10时, 颗粒的热泳特性将不再受到颗粒质量的影响. 相比于气体分子, 纳米颗粒的质量与尺寸已足够大, 因此可忽略颗粒质量对热泳的影响 [36,37] .…”

Section: 对于实际纳米颗粒而言其形状多为非球形unclassified

Thermophoretic force on nanoparticles in free molecule regime

Cui¹,

Su²,

Wang³

et al. 2021

Acta Phys. Sin.

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Thermophoresis refers to the motion of small particles suspending in a fluid with non-uniform temperature distribution due to the temperature gradient around the particle. Usually, the fluid molecules coming from the hot side carry more kinetic energy than those from the cold side, which results in a net thermophoretic force in the direction opposite to the temperature gradient. Since it was discovered more than 100 years ago, thermophoresis has been of major importance in a variety of applications, where it can play either beneficial role or adverse role, including material synthesis, micro- and nano-fabrication, and environmental science. Therefore, it is necessary to accurately evaluate the thermophoretic force. In the present work, the thermophoretic force on nanoparticles is examined in the free molecule regime by using non-equilibrium molecule dynamics (MD) simulation. It has been widely accepted that the thermophoretic force conforms with the Waldmann equation for large Knudsen numbers. However, due to the effect of the nonrigid-body interactions between the particle and gas molecules, the thermophoretic force on nanoparticles might deviate greatly from the classical theory. In our MD model, a single nanoparticle with a diameter of several nanometers suspends in a diluted gas. The Lennard-Jones (L-J) potential is employed to simulate the intermolecular interactions. To avoid deforming the nanoparticle, the solid molecules within the nanoparticles are linked to their nearest neighbors through a finite extensible nonlinear elastic bonding potential. The thermophoretic force on a nanoparticle is calculated by imposing a harmonic potential on the nanoparticle, which eliminates the effect of the Brownian motion of the nanoparticle on the thermophoresis. The effective thermal conductivity of the ambient gas is employed in Waldmann equation for the thermophoretic force due to the finite volume effect. It is found that the Waldmann theory for thermophoresis is still valid for nanoparticles in the case of weak gas-particle interaction or high gas temperature. With the increase of the gas-particle interaction strength or the decrease of the gas temperature, the Waldmann theory is invalid due to the effect of gas-particle nonrigid-body collisions and the adsorption of gas molecules on the particle surface. By considering the gas-particle nonrigid-body interaction and the modified particle size, the theoretical results for thermophoretic force accord with the MD simulations quite well.

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Departure of microscopic friction from macroscopic drag in molecular fluid dynamics

Abstract: Coarse-grained picture of Brownian motion in water: Role of size and interaction distance range on the nature of randomness

Cited by 6 publications

References 40 publications

Characterization of aqueous cellulose nanofiber dispersions from microscopy movie data of Brownian particles by trajectory analysis

Characterization of aqueous cellulose nanofiber dispersions from microscopy movie data of Brownian particles by trajectory analysis

Negative thermophoresis of nanoparticles interacting with fluids through a purely-repulsive potential

Thermophoretic force on nanoparticles in free molecule regime

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