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