Twisters In Motion

1
Twisters In Motion

• A Final Project for COMP 768 Physically-Based
  Model, Simulation, and Animation

By Michael Su
05/06/09
2
Outline

• Introduction
• Challenges
• Implementation Detail
• Reynolds Two-Fluid Model
• Boundary conditions
• Rigid body dynamics
• Simulation loop
• Demo
• Future Work
• Acknowledge
• References

3
Introduction

• Tornado
• High speed, vortex-like structure
• Chaotic appearance
• Destructive
• Applications
• Movies/Commercials
• Meteorology
• Games

4
Challenges

• Simulation
• High speed
• Large scale
• Chaotic
• Visualization
• Multilayer scattering
• Environmental reflections
• Implementation
• Inconsistent and poorly defined formulations

5
Reynolds-Average Two-Fluid Model (RATFM)

• RATFM
• Air flow Incompressible, viscous Reynold-average
  N-S equation
• Debris flow Incompressible, invicid N-S equation
• External forces
• Interaction force (for both)
• Vorticity confinement force (for air flow)
• Gravity (for debris flow)
• Reynolds shear stress
• Random turbulent fluctuations

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Reynolds-Average Two-Fluid Model (RATFM)

• Formulations

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Boundary Conditions

• The formation of the vortex
• Vertical variations
• Flux conservation Inflow outflow

y
y
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Boundary Conditions
Perspective View
Top View
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Rigid Body Dynamics

• Force
• Torque (not yet finished)

Air Flow Field
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Simulation Loop
Iteration Begins
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Demo

• The tornado structure
• Tornado interactions with rigid bodies

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More Implementation Detail

• Eulerian grid-based fluid simulator with the MAC
  grid cell structure
• Simplified rigid body solver (No collision)
• PCG (Preconditioned Conjugate Gradient) solver by
  Robert Bridson
• FLTK for the user interface

13
If I Have Nothing to Do but Work on this Project

• More accurate rigid body dynamics
• Objects with different complexities
• Deformable objects Fractures
• Physically plausible parameter sets
• GPU acceleration
• Volumetric rendering

14
Acknowledgements

• Special thanks

15
References

• Real time simulation of a tornado by Shiguang
  Liu, Zhangye Wang, Zheng Gong, Qunsheng Peng. J.
  of The Visual Computer (2007).
• Pyhsically based simulation of tornadoes by Ding.
  Thesis.
• Physically based modeling and animation of
  tornado by Liu, S., Wang, Z., Gong, Z., Chen, F.,
  Peng, Q. J. of Zhejiang University SCIENCE A
  (2006)
• Effects of Fine-Scale Debris on Near-Surface
  Tornado Dynamics by D. C. Lewelleny, Baiyun Gong,
  and W. S. Lewellen.
• Fluid Simulation by Bridson, R., Müller-Fischer,
  M. SIGGRAPH 2007 Course Notes
• Real-time Fluid Dynamics for Games by Stam, J.
  Game Developer Conference (2003)
• Fluid Simulation for Computer Graphics by
  Bridson, R. A K Peters (2008)
• Visual Simulation of Smoke by Fedkiw, R., Stam,
  J., Jensen, H. W.. SIGGRAPH 2001