# A direct comparison of particle-resolved and point-particle methods in decaying turbulence

## Abstract

We use particle-resolved direct numerical simulation (PR-DNS) as a model-free physics-based numerical approach to validate particle acceleration modelling in gas-solid suspensions. To isolate the effect of the particle acceleration model, we focus on point-particle direct numerical simulation (PP-DNS) of a collision-free dilute suspension with solid-phase volume fraction$$\unicode[STIX]{x1D719}=0.001$$in a decaying isotropic turbulent particle-laden flow. The particle diameter$$d_{p}$$in the suspension is chosen to be the same as the initial Kolmogorov length scale$$\unicode[STIX]{x1D702}_{0}$$($$d_{p}/\unicode[STIX]{x1D702}_{0}=1$$) in order to overlap with the regime where PP-DNS is valid. We assess the point-particle acceleration model for two different particle Stokes numbers,$$St_{\unicode[STIX]{x1D702}}=1$$and 100. For the high Stokes number case, the Stokes drag model for particle acceleration under-predicts the true particle acceleration. In addition, second moment quantities which play key roles in the physical evolution of the gas–solid suspension are not correctly captured. Considering finite Reynolds number corrections to the acceleration model improves the prediction of the particle acceleration probability density function and second moment statistics of the point-particle model compared with the particle-resolved simulation. We also find that accounting for the undisturbed fluid velocity in the acceleration model can be of greater importance than using the most appropriate acceleration model for a given physical problem.

- Authors:

- Publication Date:

- Research Org.:
- Univ. of Colorado, Boulder, CO (United States); Stanford Univ., CA (United States)

- Sponsoring Org.:
- USDOE Office of Fossil Energy (FE)

- OSTI Identifier:
- 1538914

- DOE Contract Number:
- FC26-07NT43098; NA0002373

- Resource Type:
- Journal Article

- Journal Name:
- Journal of Fluid Mechanics

- Additional Journal Information:
- Journal Volume: 850; Journal ID: ISSN 0022-1120

- Publisher:
- Cambridge University Press

- Country of Publication:
- United States

- Language:
- English

- Subject:
- Mechanics; Physics

### Citation Formats

```
Mehrabadi, M., Horwitz, J. A. K., Subramaniam, S., and Mani, A.
```*A direct comparison of particle-resolved and point-particle methods in decaying turbulence*. United States: N. p., 2018.
Web. doi:10.1017/jfm.2018.442.

```
Mehrabadi, M., Horwitz, J. A. K., Subramaniam, S., & Mani, A.
```*A direct comparison of particle-resolved and point-particle methods in decaying turbulence*. United States. doi:10.1017/jfm.2018.442.

```
Mehrabadi, M., Horwitz, J. A. K., Subramaniam, S., and Mani, A. Wed .
"A direct comparison of particle-resolved and point-particle methods in decaying turbulence". United States. doi:10.1017/jfm.2018.442.
```

```
@article{osti_1538914,
```

title = {A direct comparison of particle-resolved and point-particle methods in decaying turbulence},

author = {Mehrabadi, M. and Horwitz, J. A. K. and Subramaniam, S. and Mani, A.},

abstractNote = {We use particle-resolved direct numerical simulation (PR-DNS) as a model-free physics-based numerical approach to validate particle acceleration modelling in gas-solid suspensions. To isolate the effect of the particle acceleration model, we focus on point-particle direct numerical simulation (PP-DNS) of a collision-free dilute suspension with solid-phase volume fraction$\unicode[STIX]{x1D719}=0.001$in a decaying isotropic turbulent particle-laden flow. The particle diameter$d_{p}$in the suspension is chosen to be the same as the initial Kolmogorov length scale$\unicode[STIX]{x1D702}_{0}$($d_{p}/\unicode[STIX]{x1D702}_{0}=1$) in order to overlap with the regime where PP-DNS is valid. We assess the point-particle acceleration model for two different particle Stokes numbers,$St_{\unicode[STIX]{x1D702}}=1$and 100. For the high Stokes number case, the Stokes drag model for particle acceleration under-predicts the true particle acceleration. In addition, second moment quantities which play key roles in the physical evolution of the gas–solid suspension are not correctly captured. Considering finite Reynolds number corrections to the acceleration model improves the prediction of the particle acceleration probability density function and second moment statistics of the point-particle model compared with the particle-resolved simulation. We also find that accounting for the undisturbed fluid velocity in the acceleration model can be of greater importance than using the most appropriate acceleration model for a given physical problem.},

doi = {10.1017/jfm.2018.442},

journal = {Journal of Fluid Mechanics},

issn = {0022-1120},

number = ,

volume = 850,

place = {United States},

year = {2018},

month = {7}

}