# Bidisperse and polydisperse suspension rheology at large solid fraction

## Abstract

At the same solid volume fraction, bidisperse and polydisperse suspensions display lower viscosities, and weaker normal stress response, compared to monodisperse suspensions. The reduction of viscosity associated with size distribution can be explained by an increase of the maximum flowable, or jamming, solid fraction. In this work, concentrated or "dense" suspensions are simulated under strong shearing, where thermal motion and repulsive forces are negligible, but we allow for particle contact with a mild frictional interaction with interparticle friction coefficient of 0.2. Aspects of bidisperse suspension rheology are first revisited to establish that the approach reproduces established trends; the study of bidisperse suspensions at size ratios of large to small particle radii (2 to 4) shows that a minimum in the viscosity occurs for zeta slightly above 0.5, where zeta=phi_{large}/phi is the fraction of the total solid volume occupied by the large particles. The simple shear flows of polydisperse suspensions with truncated normal and log normal size distributions, and bidisperse suspensions which are statistically equivalent with these polydisperse cases up to third moment of the size distribution, are simulated and the rheologies are extracted. Prior work shows that such distributions with equivalent low-order moments have similar phi_{m}, and the rheological behaviorsmore »

- Authors:

- Benjamin Levich Institute and Department of Chemical Engineering, The City College of New York, New York, New York 10031
- Pacific Northwest National Laboratory, Richland, Washington 99352

- Publication Date:

- Research Org.:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 1421338

- Report Number(s):
- PNNL-SA-130632

Journal ID: ISSN 0148-6055; KC0307010

- DOE Contract Number:
- AC05-76RL01830

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Rheology; Journal Volume: 62; Journal Issue: 2

- Country of Publication:
- United States

- Language:
- English

### Citation Formats

```
Pednekar, Sidhant, Chun, Jaehun, and Morris, Jeffrey F.
```*Bidisperse and polydisperse suspension rheology at large solid fraction*. United States: N. p., 2018.
Web. doi:10.1122/1.5011353.

```
Pednekar, Sidhant, Chun, Jaehun, & Morris, Jeffrey F.
```*Bidisperse and polydisperse suspension rheology at large solid fraction*. United States. doi:10.1122/1.5011353.

```
Pednekar, Sidhant, Chun, Jaehun, and Morris, Jeffrey F. Thu .
"Bidisperse and polydisperse suspension rheology at large solid fraction". United States.
doi:10.1122/1.5011353.
```

```
@article{osti_1421338,
```

title = {Bidisperse and polydisperse suspension rheology at large solid fraction},

author = {Pednekar, Sidhant and Chun, Jaehun and Morris, Jeffrey F.},

abstractNote = {At the same solid volume fraction, bidisperse and polydisperse suspensions display lower viscosities, and weaker normal stress response, compared to monodisperse suspensions. The reduction of viscosity associated with size distribution can be explained by an increase of the maximum flowable, or jamming, solid fraction. In this work, concentrated or "dense" suspensions are simulated under strong shearing, where thermal motion and repulsive forces are negligible, but we allow for particle contact with a mild frictional interaction with interparticle friction coefficient of 0.2. Aspects of bidisperse suspension rheology are first revisited to establish that the approach reproduces established trends; the study of bidisperse suspensions at size ratios of large to small particle radii (2 to 4) shows that a minimum in the viscosity occurs for zeta slightly above 0.5, where zeta=phi_{large}/phi is the fraction of the total solid volume occupied by the large particles. The simple shear flows of polydisperse suspensions with truncated normal and log normal size distributions, and bidisperse suspensions which are statistically equivalent with these polydisperse cases up to third moment of the size distribution, are simulated and the rheologies are extracted. Prior work shows that such distributions with equivalent low-order moments have similar phi_{m}, and the rheological behaviors of normal, log normal and bidisperse cases are shown to be in close agreement for a wide range of standard deviation in particle size, with standard correlations which are functionally dependent on phi/phi_{m} providing excellent agreement with the rheology found in simulation. The close agreement of both viscosity and normal stress response between bi- and polydisperse suspensions demonstrates the controlling in influence of the maximum packing fraction in noncolloidal suspensions. Microstructural investigations and the stress distribution according to particle size are also presented.},

doi = {10.1122/1.5011353},

journal = {Journal of Rheology},

number = 2,

volume = 62,

place = {United States},

year = {Thu Mar 01 00:00:00 EST 2018},

month = {Thu Mar 01 00:00:00 EST 2018}

}