ANIMATIONS FROM "On the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid"

Authors: Manuel Moriche, Daniel Hettmann, Manuel García-Villalba and Markus Uhlmann.

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
Markus Uhlmann