Simulation of particulate fouling at a microchannel entrance region
A computational study is reported on the dynamics of particles near the entrance of a microchannel, as used in microfluidic flow systems. The collision of particles with fins separating the microchannels in these entrance regions makes them particularly susceptible to particle fouling.
The study employs a soft-sphere discrete-element method with van der Waals and electric double-layer forces between the particles and the wall. A multi-block-structured grid fit to the flow domain boundaries is used to compute the fluid velocity field using a finite-volume method.
The fluid flow is interpolated onto a Cartesian grid for efficient flow field interpolation at the particle locations, and a level-set method is used to represent the flow field boundaries in the particle computation. Particles adhering to the upstream face of the fin separating two microchannels are found to form clusters, which are pulled laterally by the stagnation-point flow near the fin.
Even under conditions where the adhesion is sufficiently strong that there is little or no particle rolling on the fin face, the particles are still removed from the fin due to collisions with other particles. Individual particles are removed quickly from the fin face due to collision with upstream particles, whereas particle clusters have sufficient adhesion force with the fin surface that they can withstand collision with other particles for longer periods of time before they are removed in a cascade-like process.
Keywords: microchannel fouling, particle adhesion, entrance region.