Simulation and Visualization of Flows Laden with Cylindrical Nanoparticles in a Mixing Layer

Wenqian Lin,Peijie Zhang

doi:10.1155/2018/6548689

Abstract

The motion of cylindrical particles in a mixing layer is studied using the pseudospectral method and discrete particle model. The effect of the Stokes number and particle aspect ratio on the mixing and orientation distribution of cylindrical particles is analyzed. The results show that the rollup of mixing layer drives the particles to the edge of the vortex by centrifugal force. The cylindrical particles with the small Stokes number almost follow fluid streamlines and are mixed thoroughly, while those with the large Stokes number, centrifugalized and accumulated at the edge of the vortex, are poorly mixed. The mixing degree of particles becomes worse as the particle aspect ratio increases. The cylindrical particles would change their orientation under two torques and rotate around their axis of revolution aligned to the vorticity direction when the shear rate is low, while aligning on the flow-gradient plane beyond a critical shear rate value. More particles are oriented with the flow direction, and this phenomenon becomes more obvious with the decrease of the Stokes number and particle aspect ratio.

Highlights

Mixing of nanoparticles in a flow was found in many applications and has been a subject of interest during the recent twenty years. e mixing of nanoparticles affects the property of the flow and the behaviors of the final production. erefore, understanding deeply such a flow is important to design a novel technology for nanoparticle manipulation.Some efforts have been put into the numerical simulation and visualization of nanoparticles
As far as we know, the motion and mixing behaviors of cylindrical nanoparticles in the mixing layer have not been reported in the literatures yet. erefore, the objective of the present paper is to explore the impact of the Stokes number and particle aspect ratio on the mixing property and orientation distributions of cylindrical particles in a mixing layer
E rollup of the mixing layer drives the particles to the edge of the vortex by the inertial centrifugal force, and at the same time it brings about an asymmetric shear rate distribution around the particle and generates a normal stress imbalance on the particle surface. e cylindrical particle migration and mixing are dependent on the above two factors

Summary

Introduction

Mixing of nanoparticles in a flow was found in many applications and has been a subject of interest during the recent twenty years. e mixing of nanoparticles affects the property of the flow and the behaviors of the final production. erefore, understanding deeply such a flow is important to design a novel technology for nanoparticle manipulation.Some efforts have been put into the numerical simulation and visualization of nanoparticles. Hsiao et al [3] used mixed PSS-DTMA Langmuir layers to incorporate with silver precursors from the subphase and transferred them onto mica substrates; they showed that enhancing the DTMA (+) in the mixed PSS-DTMA system would increase the hydrophobic property of the complexes. They inferred that the polyelectrolyte-surfactant template can offer a potential of designing structures of polyelectrolyte-nanoparticle materials. Xie et al [5] simulated numerically the impact coherent structure on the Brownian coagulation of particles in a mixing layer, and it is found that the number density of nanoparticles decreases gradually as the flow evolves, while the particle average volume increases. Kerli and Alver [13] investigated the mixture of ZnO and NiO e ect on the solar cell and observed that the solar cells made with ZnO have the highest performance with the e ciency of 0.542%

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Results

Conclusion