著者

佐藤 明 二村 宗男

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.84, no.858, pp.17-00558-17-00558, 2018 (Released:2018-02-25)

参考文献数

24

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In the present study we have performed lattice Boltzmann simulations of an electro-conjugate fluid in order to elucidate the mechanism for inducing a strong microjet between positive and negative electrodes in the situation of a high external electric field. It has been assumed that charges are injected from the surface of a positive electrode where electric fields are significantly concentrated. The mechanism due to these injected charges has mainly been assessed as an essential factor for the occurrence of a strong microjet. In the present numerical simulations, the lattice Boltzmann equations and the basic equation for charge densities have simultaneously been solved for obtaining the flow field and the charge density distribution, respectively. The main results obtained here are summarized as follows. A strong microjet is possibly generated between the positive and the ground electrodes in the situation where Coulomb forces are much more dominant than viscous forces. A microjet starts to occur at the position of the injected charges, grows along with the fluid flow, collides with the ground electrode, and flows away from the electrode in an oblique direction relative to the center line connected between the electrodes. The flow rate induced due to the occurrence of a strong microjet increases approximately in proportion to the increasing external electric field strength. From good agreement with the corresponding experimental result in regard to the velocity vectors of a microjet, we may conclude that the mechanism for inducing a strong microjet in an electro-conjugate fluid is the interaction between the injected charges from the positive electrode and a high external electric field.

著者

岡田 和也 佐藤 明 二村 宗男

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.856, pp.17-00378-17-00378, 2017 (Released:2017-12-25)

参考文献数

16

被引用文献数

1

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We have investigated a regime change in the aggregate structures of a suspension composed of magnetic cubic particles in thermodynamic equilibrium, by means of Monte Carlo simulations. In concrete, we have addressed the dependence of the regime change on a variety of factors such as the magnetic field strength and the magnetic particle-particle interaction strength. The orientational distribution function and order parameters have been focused on for quantitatively discussing these characteristics. The main results obtained here are summarized as follows. If the magnetic interaction strength is sufficiently large for cluster formation, closely-packed clusters are formed under the combination and expansion of a cluster unit composed of 8 particles. A regime change in the internal structure of aggregates appears in a narrow range of the magnetic interaction strength, which is clearly exhibited by the order parameter employed here. A closely-packed configuration can be clearly characterized by the orientational distribution function; 8 high peaks appear in the orientational space in the case of the closely-packed structure. As the magnetic field is increased, the closely-packed clusters are collapsed and transformed into wall-like clusters along the magnetic field direction. This is because the magnetic moment of each particle has a strong tendency to incline in the magnetic field direction in the situation of a strong magnetic field.