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Fluids 2018, 3(3), 52; https://doi.org/10.3390/fluids3030052

Direct Numerical Simulation of Particles in Spatially Varying Electric Fields

1
Department of Mechanical Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA
2
Department of Mechatronics and Mechanical Engineering, Higher Colleges of Technology, P. O. Box 15825, Dubai, UAE
This paper is a modified version of our paper “Direct Numerical Simulations (DNS) of Particles in Spatially Varying Electric Fields” published at the ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014, Chicago, IL, USA, 3–7 August 2014.
*
Author to whom correspondence should be addressed.
Received: 15 June 2018 / Revised: 12 July 2018 / Accepted: 17 July 2018 / Published: 24 July 2018
(This article belongs to the Special Issue Drop, Bubble and Particle Dynamics in Complex Fluids)
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Abstract

A numerical scheme is developed to simulate the motion of dielectric particles in the uniform and nonuniform electric fields of microfluidic devices. The motion of particles is simulated using a distributed Lagrange multiplier method (DLM) and the electric force acting on the particles is calculated by integrating the Maxwell stress tensor (MST) over the particle surfaces. One of the key features of the DLM method used is that the fluid-particle system is treated implicitly by using a combined weak formulation, where the forces and moments between the particles and fluid cancel, as they are internal to the combined system. The MST is obtained from the electric potential, which, in turn, is obtained by solving the electrostatic problem. In our numerical scheme, the domain is discretized using a finite element scheme and the Marchuk-Yanenko operator-splitting technique is used to decouple the difficulties associated with the incompressibility constraint, the nonlinear convection term, the rigid-body motion constraint and the electric force term. The numerical code is used to study the motion of particles in a dielectrophoretic cage which can be used to trap and hold particles at its center. If the particles moves away from the center of the cage, a resorting force acts on them towards the center. The MST results show that the ratio of the particle-particle interaction and dielectrophoretic forces decreases with increasing particle size. Therefore, larger particles move primarily under the action of the dielectrophoretic (DEP) force, especially in the high electric field gradient regions. Consequently, when the spacing between the electrodes is comparable to the particle size, instead of collecting on the same electrode by forming chains, they collect at different electrodes. View Full-Text
Keywords: dielectrophoresis; direct numerical simulations; Maxwell stress tensor method; point-dipole method; distributed Lagrange multiplier method dielectrophoresis; direct numerical simulations; Maxwell stress tensor method; point-dipole method; distributed Lagrange multiplier method
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Amah, E.; Janjua, M.; Singh, P. Direct Numerical Simulation of Particles in Spatially Varying Electric Fields . Fluids 2018, 3, 52.

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