This document summarizes a presentation given at the International Symposium on Space Science in 2019. The presentation discussed a simulation of how composite spherical particles compact under self-gravitation. The simulation considered different families of composite particles, including S-family and H-family particles. The results showed that while S-family particles could influence their neighbors' configuration, the presence of H-family particles overrode this effect, leading to different compacted structures. Going forward, the presenters planned to generate more configurations, include M-family particles, and explore different members of the composite particle families.

1. 25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
1
Compaction of two-dimensional system of
composite spherical particles under influence of
self-gravitation: Between lock-and-key model
and tetris-structure
Sparisoma Viridi1, Budi Dermawan2
1Department of Physics, Institut Teknologi Bandung, Bandung 40132, Indonesia
2Department of Astronomy, Institut Teknologi Bandung, Bandung 40132, Indonesia
1dudung@fi.itb.ac.id, 2budider@as.itb.ac.id
20190925_4

2. 25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
2
Outline
• Previous study
• Question
• Simulation
• Results and discussion
• Summaries

3. 25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
3
Previous study

4. Hexagonal close packed structure
• Simulation of floating spheres forming two-
dimensional hexagonal close packed (HCP)
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
4
S. Viridi, V. Suendo, "Molecular Dynamics Simulation of Floating Sphere Forming Two-Dimensional Hexagonal Close
Packed Structure", the 5th International Symposium on Current Progress in Mathematics and Sciences (ISCPMS
2019), 9-10 July 2019, Depok, Indonesia, (presented, reviewed, revised), url https://doi.org/10.17605/osf.io/a3gjv.

5. t = 0 s
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
5
0.5σ 1.5σ

6. t = 1 s
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
6
0.5σ 1.5σ

7. t = 3 s
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
7
0.5σ 1.5σ

8. t = 4 s
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
8
0.5σ 1.5σ

9. t = 6 s
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
9
0.5σ 1.5σ

10. t = 10 s
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
10
0.5σ 1.5σ

11. 96 million 'shade balls' at LA
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
11
Mashable, "LA throws 96 million 'shade balls' at its water shortage — and it's mesmerizing | Mashable", YouTube,
13.08.2015, url https://www.youtube.com/watch?v=mEmwJzQjwyw [20190710].

12. 25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
12
Question

13. Question
• How can non-HCP structure be made?
• What if there are composite particles?
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
13

14. Families of composite particles
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
14

15. Normal length types
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
15

16. 25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
16
Simulation

17. System
• There are several spherical particles and also
composite particles
• They interact through repulsion force Nij and
attractive force Gij
• There is also binding force Bij in a composite
particle
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
17

18. Considered forces
• Binding force
where holds only internally inside a composite
particles (S-, H-, or M-families)
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
18
  ijBijijijBij vrlrkB

 ˆ

19. Considered forces (cont.)
• Attractive force: gravitation force
• Repulsion force (limited range): normal force
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
19
ij
ij
ji
Gij r
r
mm
kG ˆ
2


ijijNijijNij vrkN ˆˆ  


20. Newton’s 2nd law
• Acceleration of particle i
index j only inside a composite particle
index k only between composite particle
index l for all particles
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
20
  







  l
il
k
ik
j
ij
i
i GNB
m
ta
 1

21. Numerical solution
• Using Euler algorithm
integrated from tbeg to tend with rather small
time step Δt
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
21
      ttatvttv iii 

      ttvtrttr iii 


22. 25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
22
Results and discussion

23. Only spherical particles
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
23

24. S-family composite particle
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
24

25. H-family composite particle
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
25

26. S- & H-families composite particle
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
26

27. 25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
27
Summaries

28. Conclusion
• Simulation of compaction of two-dimensional
system of composite spherical particles under
influence of self-gravitation has been per-
formed
• S-family composite particles can affect their
neighbor configuration
• But if there are H-family composite particles,
their influence will override S-family influence
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
28

29. Next plan
• Generate more configurations to get better
statistical results
• Use also M-familiy composite particles
• Use another member of S-, H-, and M-families
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
29

30. Acknowledgements
• ISSS 2019 Committee and LAPAN for the
opportunity in presenting this work
25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
30

31. 25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
31
https://osf.io/8f479/

32. 25 September 2019
Bandung, Indonesia
International Symposium on Space Science
(ISSS 2019)
32
Thank you