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Dense colloidal suspensions in microchannel flow
| Content Provider | Semantic Scholar |
|---|---|
| Author | Kanehl, Philipp |
| Copyright Year | 2017 |
| Abstract | Colloids in suspensions exhibit shear-induced migration towards regions of low viscous shear. In bidisperse suspensions under pressure driven flow large particles can segregate in the center of a microchannel and the suspension partially demixes. In channels containing very dense suspensions, colloids may jam and produce regular flow speed oscillations generated by density rarefaction waves. Increasing the density even further the oscillations become irregular. To develop a theoretical understanding of these effects, we simulate spheres under pressure-driven channel flow in two and three dimensions using the mesoscale simulation technique of multi-particle collision dynamics. To model hydrodynamic segregation, we formulate a phenomenological model for the particle currents based on the work of R. J. Phillips et al. [Phys. Fluids 4, 30 (1992)]. Using a single fit parameter for the intrinsic diffusivity, our theory accurately reproduces the simulated density profiles across the channel. We present a detailed parameter study on how a monodisperse suspension is enriched in the channel center and quantitatively confirm the experimental observation that a binary mixture partially segregates into its two species. In particular, we always find a strong accumulation of large particles in the center. For our simulations on jamming, the colloids are modeled as elastic and frictional disks. The model reproduces periodic velocity and density pulse trains, traveling upstream in the microchannel, which are found in experiments conducted by L. Isa et al. [Phys. Rev. Lett. 102, 058302 (2009)]. We show that colloid-wall friction and the resultant force chains are crucial for the formation of these pulses. With increasing colloid density solitary jams occur, which become periodic pulse trains at intermediate densities and unstable solitary pulses at high densities. We formulate a phenomenological continuum model and show how these spatio-temporal flow and density profiles can be understood as homoclinic and periodic orbits in traveling-wave equations. |
| File Format | PDF HTM / HTML |
| DOI | 10.14279/depositonce-5804 |
| Alternate Webpage(s) | https://depositonce.tu-berlin.de/bitstream/11303/6245/5/kanehl_philipp.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
