# Focusing of active particles in a converging flow

## Abstract

We consider active particles swimming in a convergent fluid flow in a trapezoid nozzle with no-slip walls. We use mathematical modeling to analyze trajectories of these particles inside the nozzle. By extensive Monte Carlo simulations, we show that trajectories are strongly affected by the background fluid flow and geometry of the nozzle leading to wall accumulation and upstream motion (rheotaxis). In particular, we describe the non-trivial focusing of active rods depending on physical and geometrical parameters. It is also established that the convergent component of the background flow leads to stability of both downstream and upstream swimming at the centerline. The stability of downstream swimming enhances focusing, and the stability of upstream swimming enables rheotaxis in the bulk.

- Authors:

- Pennsylvania State Univ., University Park, PA (United States). Department of Mathematics
- Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
- Pennsylvania State Univ., University Park, PA (United States). Department of Mathematics and Department of Biomedical Engineering

- Publication Date:

- Research Org.:
- Argonne National Lab. (ANL), Argonne, IL (United States)

- Sponsoring Org.:
- USDOE; National Science Foundation (NSF); German Research Foundation (DFG)

- OSTI Identifier:
- 1419938

- Grant/Contract Number:
- [AC02-06CH11357]

- Resource Type:
- Accepted Manuscript

- Journal Name:
- New Journal of Physics

- Additional Journal Information:
- [ Journal Volume: 19; Journal Issue: 11]; Journal ID: ISSN 1367-2630

- Publisher:
- IOP Publishing

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 97 MATHEMATICS AND COMPUTING; 42 ENGINEERING; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS

### Citation Formats

```
Potomkin, Mykhailo, Kaiser, Andreas, Berlyand, Leonid, and Aranson, Igor. Focusing of active particles in a converging flow. United States: N. p., 2017.
Web. doi:10.1088/1367-2630/aa94fd.
```

```
Potomkin, Mykhailo, Kaiser, Andreas, Berlyand, Leonid, & Aranson, Igor. Focusing of active particles in a converging flow. United States. doi:10.1088/1367-2630/aa94fd.
```

```
Potomkin, Mykhailo, Kaiser, Andreas, Berlyand, Leonid, and Aranson, Igor. Fri .
"Focusing of active particles in a converging flow". United States. doi:10.1088/1367-2630/aa94fd. https://www.osti.gov/servlets/purl/1419938.
```

```
@article{osti_1419938,
```

title = {Focusing of active particles in a converging flow},

author = {Potomkin, Mykhailo and Kaiser, Andreas and Berlyand, Leonid and Aranson, Igor},

abstractNote = {We consider active particles swimming in a convergent fluid flow in a trapezoid nozzle with no-slip walls. We use mathematical modeling to analyze trajectories of these particles inside the nozzle. By extensive Monte Carlo simulations, we show that trajectories are strongly affected by the background fluid flow and geometry of the nozzle leading to wall accumulation and upstream motion (rheotaxis). In particular, we describe the non-trivial focusing of active rods depending on physical and geometrical parameters. It is also established that the convergent component of the background flow leads to stability of both downstream and upstream swimming at the centerline. The stability of downstream swimming enhances focusing, and the stability of upstream swimming enables rheotaxis in the bulk.},

doi = {10.1088/1367-2630/aa94fd},

journal = {New Journal of Physics},

number = [11],

volume = [19],

place = {United States},

year = {2017},

month = {10}

}

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