Supplementary animations "On the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid"

ANIMATIONS FROM "On the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid" by Manuel Moriche, Daniel Hettmann, Manuel García-Villalba and Markus Uhlmann. J. Fluid Mech., 963:A1, 2023. DOI; 10.1017/jfm.2023.261

# Many-particle cases

## Flow configuration

The animations correspond to the cases G111 and G152 described in table 1 from the
original article. In these cases a set of many particles settle under gravity in a
triply periodic configuration. The particles considered are oblate spheroids of
aspect ratio 1.5 and the number of them is such that the solid volume fraction is 0.5%,
which corresponds to the dilute regime. The cases differ from each other in the Galileo
number: `G=sqrt((rhop/rhof-1)*g*D**3)/nu=110.56` and 152.02 for cases G111 and G152,
respectively. The size of computational domain is approximately `[55x55x220]D**3`,
where D is the diameter of a sphere with the same volume as the spheroids and the
resolution used (`D/dx`) is approximately 21.

The time is indicated in the videos is expressed in `D/Ug` units, where
`Ug=sqrt((rhop/rhof-1)*abs(g)*D)` is a gravitationally scaled velocity.

## Content

For each case there are different videos of the initial or converged state, or different
representations of the flow/particles.

The case, part of the video and representation is contained in the name of each video:
1. Case:
- `G111`: Galileo 110.56.
- `G152`: Galileo 152.02.
2. Time interval of the simulation:
- `INITIAL`: First simulated time, including the time before releasing the particles (t<0).
- `CONVERGED`: Statistically stationary part of the simulation.
3. Point of view: `bottom`, `iso`, `side` and `side_zoomed`.
4. Representation. In every video particles are always represented in pink and wakes with
transparency isocontours of Q criterion. Additionally, isocontours of filtered vertical
velocity are represented in two ways:
- `low_speed`: The value to define the isocontour is similar to that of the mixture. In this
representation the regions in which particles are located in clustering/non-clustering
regions are easily identified. Dark blue face points to non-clustering, slow regions and
light blue face points to clustering, fast regions.
- `high_speed`: The value to define isocontour is approximately 50% larger than the average
velocity of the mixture. Therefore, the isocontours (in yellow) indicate regions of
where the downward velocity is greatly enhanced.
- `only_wakes`: No flow velocity is represented. Only side zoomed view is available for
this representation.

# Drafting-kissing-tumbling

For illustration purposes one animation is included (`DKT_animation.mp4`) of the
drafting-kissing-tumbling simulations. The simulations have been performed
for Galileo 110.56 with density ratio 1.5. The size of the computational domain
measures `[10.66 x 10.66 x 21.33] D**3`. Four configurations are considered:

- Free-to-rotate spheres (angular motion enabled).
- Rotationally-locked spheres (angular motion suppressed).
- Free-to-rotate spheroids of aspect ratio 1.5 (angular motion enabled).
- Rotationally-locked spheroids of aspect ratio 1.5 (angular motion suppressed).

In the animation the four configurations are shown for a single initial condition, namely
the relative position of the trailing particle with respect to the leading particle is `[0.625, 7.5] D`.
The particles are represented in green with a mesh that helps to visualize the rotation and
contours of vertical velocity are shown in grey scale.

# References:

Manuel Moriche, Daniel Hettmann, Manuel García-Villalba and Markus Uhlmann,
_"On the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid"_,
accepted in J. Fluid Mech.

# History:

__04.10.2022__ Creation and data added
__06.02.2023__ DKT animation added
# Contact

[Manuel Moriche](mailto:[e-mail])
[Markus Uhlmann](mailto:[e-mail])