The document summarizes a study on granular buoyant force in a two-dimensional intruder-particle bed system using molecular dynamics simulation. The study models the forces between particles and the fluid using equations of motion. The simulation shows three stages: fluid condensation, an object intruding, and the system reaching equilibrium. Results for different object and fluid densities are presented and analyzed. The simulation found that the final state resembles a macroscopic system when the object density is larger than the fluid density. The study contributes to investigating density from a particle-level perspective.
Granular buoyant force in a two-dimensional intruder-particles bed system
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Granular buoyant force in a
two-dimensional intruder-
particles bed system
Dewi Muliyati1
, Nurhayati2
, Johri Sabaryati3
, Sparisoma Viridi4
1
FMIPA, Universitas Negeri Jakarta, Jakarta 13220, Indonesia
2
FST, Universitas Islam Negeri Ar-Raniry, Banda Aceh 23111, Indonesia
3
FKIP, Universitas Muhammadiyah Mataram, Mataram 83127, Indonesi
4
FMIPA, Institut Teknologi Bandung, Bandung 40132, Indonesia
1
dmuliyati@gmail.com, 2
firstnur1708@gmail.com, 3
joyafarashy@gmail.com, 4
dudung@gmail.com,
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Outline
• Introduction
• Theory
• Simulation
• Results and discussion
• Conclusion
4. Buoyancy
• It is an interesting phenomenon, especially if
not only involving fluid and object densities as
reported in 1873
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G. Sigerson, "On a Cause of the Buoyancy of Bodies of a Greater Density than Water", Proceedings of the Royal Irish
Academy. Science, vol. 2 (1875 - 1877), pp. 22-25, June 1873, url https://www.jstor.org/stable/20489980
5. Automatic observation
• Today buoyancy can be ob-
served using microcontroller
that au-
toma-
tically
mea-
sures
the data
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P. R. Espindola, C. R. Cena, D. C. B. Alves, D. F. Bozano, A. M. B. Goncalves, "Use of an Arduino to studybuoyancy
force", Physics Education, vol. 53, no. 3, p. 035010, May 2018, url https://doi.org/10.1088/1361-6552/aaa93a
6. Virtual laboratory
• The phenomenon is still interesting to investi-
gate through a virtual laboratory
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J. M. Vitale, M. C. Linn, "Designing Virtual Laboratories to Foster Knowledge Integration: Buoyancy and Density", in M.
E. Auer et al. (eds.), Cyber-Physical Laboratories in Engineeringand Science Education, chap. 7, pp. 163-189, 2018,
url https://doi.org/10.1007/978-3-319-76935-6_7
7. Graphical concept
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J. M. Vitale, L. Applebaum, M. C. Linn, "Coordinatingbetween Graphs and Science Concepts: Density and Buoyancy",
Cognition and Instruction, vol. 37, no. 1, pp. 38-72, Jan 2019, url https://doi.org/10.1080/07370008.2018.1539736
10. Buoyant force
• Object i with immersed volume Vi' in fluid
with density ρf in environment with gravity ,
will have buoyant force of
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.
gVB ifi
′−= ρ
g
11. Gravitational force
• Object i with volume Vi with density ρg in
environment with gravity , will have
gravitational force of
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.
g
gVG igi
ρ=
12. Newton’s 1st
law of motion
• In equilibrium for object i
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.
( )
ifig
ifig
ifig
ifig
ii
i
VV
VV
gVV
gVgV
BG
F
′=
=′−⇒
=′−
=′−
=+
=∑
ρρ
ρρ
ρρ
ρρ
0
0
0
0
0
′i
h ih
A
AhV =
gρfρ
iB
iG
14. Normal forces
• Spherical grains i will have normal force from
spherical grains j in the form of
with
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.
ijijNijijNij vrkN ˆˆ ξγξ −=
( )ijjiij rRR −+= ,0maxξ
15. The other forces
• Grains i will under influence of following
forces
– Buoyant force (slide 10)
– Gravitational force (slide 11)
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16. Molecular dynamics method
• Newton 2nd
law of motion
• Forward finite difference
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++=⇒= ∑∑ j
ijii
i
iii NGB
m
aamF
1
( ) ( ) tatvdttv ∆+=+
( ) ( ) ( ) ttvtrdttr ∆+=+
18. Stage 1: "Fluid" condensation
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.
19. Stage 2: Object intruding
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20. Stage 3: System equilibrium
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21. Some final states
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ρi / ρf = 2/2 ρi / ρf = 3/2 ρi / ρf = 4/2 ρi / ρf = 5/2
ρi / ρf = 6/2 ρi / ρf = 7/2 ρi / ρf = 8/2 ρi / ρf = 9/2
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0
0.04
0.08
0.12
0.16
0.2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
z
t
ziavg
zbmax
zbavg
ρi / ρf = 2/2
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0
0.04
0.08
0.12
0.16
0.2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
z
t
ziavg
zbmax
zbavg
ρi / ρf = 3/2
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0
0.04
0.08
0.12
0.16
0.2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
z
t
ziavg
zbmax
zbavg
ρi / ρf = 4/2
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0
0.04
0.08
0.12
0.16
0.2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
z
t
ziavg
zbmax
zbavg
ρi / ρf = 5/2
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0
0.04
0.08
0.12
0.16
0.2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
z
t
ziavg
zbmax
zbavg
ρi / ρf = 6/2
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0
0.04
0.08
0.12
0.16
0.2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
z
t
ziavg
zbmax
zbavg
ρi / ρf = 7/2
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0
0.04
0.08
0.12
0.16
0.2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
z
t
ziavg
zbmax
zbavg
ρi / ρf = 8/2
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0
0.04
0.08
0.12
0.16
0.2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
z
t
ziavg
zbmax
zbavg
ρi / ρf = 9/2
30. Code
• Part of butiran.js
https://github.com/dudung/butiran.js
• Application
https://rawcdn.githack.com/dudung/butiran.j
s/f85fd1334dfd4d95a28ea2b254134f7603c6b
7d8/app/igdensity/igdensity.html
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32. Conclusion
• Molecular dynamics-based simulation for
investigating density from particles point of
view has been built (based on butiran.js)
• Final state is similar to macroscopic system if
(individual particle) object density larger than
(individual particle) fluid density, ρi / ρf ≥ 4/2
• Compaction of all particles will prevent further
equilibrium
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33. Acknowledgments
• Author would like to thank to SNF Committee
and FMIPA UNJ for the honour as invited
speaker in parallel session
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