(398ae) Movement of Cylinder-Shaped Nano-Paticles in a Micro Channel By Individual Particle Tracking

The goal of this study is to determine the behavior of nanoparticles in fluid flow by calculating trajectories, orientation and hydrodynamic forces acting on the particles. Initially, a lattice Boltzmann simulation is used to determine the velocity profile in micro-flows with no slip boundary condition at low Reynolds numbers. Flow in microchannels and in microslits with width of 5 microns is considered. Then, cylinder-shaped particles are released at different locations into the flow, representing carbon nanotubes that are moving within the flow field. It is assumed that the presence of the particles does not influence the fluid velocity. The carbon nanotubes experience hydrodynamic forces that include gravity, drag, buoyancy, lift and pressure-gradient forces [1]. Besides, Brownian force is important, because of the nanoscale dimensions of the nanotubes. Additionally, the interaction between the particles and the wall can be accounted by defining a Morse-like potential in regions very close to the wall [2]. The velocity and position of each particle is computed numerically at each time step. Based on hydrodynamic forces, a system of rotation equations is utilized to calculate the angular velocity and orientation of each particle.

The paper will discuss the effect of the aspect ratio of particles on hydrodynamic forces and on the rotation of particles, as well as the relative effect of each force on the particle trajectories and on the collision of the particles with the micro-channel wall.  The distribution of the orientation angle of the nanotubes relative to the direction of the flow will also be discussed. Finally, the lattice Boltzman/particle tracking results will be compared to results obtained by dissipative particle dynamics at smaller scales. 

This work can find applications in the determination of the trajectories of carbon nanotubes as they are released in the subsurface, where they can find their way to the water table, or in cases where nanoparticles are used to enhance oil recovery [3] or as tracers in haydraulic fracturing fluids. 

ACKNOWLEDGEMENTS

The financial support of the Advanced Energy Consortium (AEC BEG08-022) and the computational support of XSEDE (CTS090017) are acknowledged.

REFERENCES

1. Maxey, M.R., and J.J. Riley, “Equation of motion for a small rigid sphere in a non-uniform flow”, Phys. Fluids, 26, 883-889, 1983
2. Kolmakov G., Ravanur, R., Tangirala, R., Emrick, T., Russell, T.R., Crossby A.J., and A.C. Balazs, “Using nanoparticle-filled capsules for site-specific healing of damaged substrates: Creating a repair and go system”, ACS Nano, 4(2), 1115-1122, 2010.
3. Kong, X. , and M. M. Ohadi, “Applications of Micro and Nano Technologies in the Oil and Gas Industry - Overview of the Recent Progress”, Society of Petroleum Engineers, paper # 138241, 2010.