Comprehensive Tutorial of Level Set Method

Transcript

1. Comprehensive Guide of Level Set Method with Fluid Mechanics Jongsu Kim Department of Computational Science and Engineering Yonsei University 1
2. Yonsei University 2/00 Contents • Motivation • Level Set Method • Level Set Reinitialization • Numerical Schemes • Conclusion
3. Yonsei University 3/00 Multiphase Phase Flow •
4. Yonsei University 4/00 • • • • • • • • Multiphase Phase Flow
5. Yonsei University 5/00 Contents • Motivation • Level Set Method • Numerical Schemes • Conclusion • Level Set Reinitialization
6. Yonsei University 6/00 Modification of Navier-Stokes Equation • = − + 2 + = − + 2 + ⋅ = 0 Ω What equation at the interface?
7. Yonsei University 7/00
8. Yonsei University 8/00 CSF Model • • 1 − 2 + = 1 − 2 + 1 − 2 + = 21 1 − 22 2 2 + 2 − 1 + 1 = •
9. Yonsei University 9/00 CSF Model • = () • () () = [] () = 1 ( 1) 2 ( 2) < > = 1 + 2 /2 ( ℎ ) = 2 − 1
10. Yonsei University 10/00 What We Have Done • = − + 2 + , = 0 = − + 2 + , = 0 ⋅ = 0 Ω 2 − = − + ul = ug , x ∈ Γ Three equations.. Should we solve these equation separately? And how we know the interface?
11. Yonsei University 11/00 VOF Method • • • • = 1 ( 2) (0 < < 1) + ⋅ = 0
12. Yonsei University 12/00 VOF Method • • • • •
13. Yonsei University 13/00 Level Set Method = =0 = ⋅ =0 , = < 0, ( ) > 0, ( ) = 0 ( ℎ )
14. Yonsei University 14/00 = , > 0 , ≤ 0 + ⋅ = 0 , = < 0, ( ) > 0, ( ) = 0 ( ℎ ) Level Set Method
15. Yonsei University 15/00 + ⋅ = 0 Γ , , (, ) , = , , , , , = ( , , , ) ( , , , , ) (, ) Γ , , , , ≡ + + = + + Level Set Method
16. Yonsei University 16/00 , = < 0, ( ) > 0, ( ) = 0 ( ℎ ) () = , ( ) , ( ) + /2, () () = , ( ) , ( ) + /2, () Level Set Method
17. Yonsei University 17/00 = − + ⋅ 2 − + Level Set Method () () = + − , = + − () What We Have Done () = 0, < 0 1 2 , = 0 1, > 0 However, we still have a discontinuity … + ⋅ = 0
18. Yonsei University 18/00 Contents • Motivation • Level Set Method • Numerical Schemes • Conclusion • Level Set Reinitialization
19. Yonsei University 19/00 → () Heaviside Function () = 0, < − 1 2 1 + + 1 sin / , || ≤ 1, > +
20. Yonsei University 20/00 Distance Function • • 2 |∇| () = 0, < − 1 2 1 + + 1 sin / , || ≤ 1, > + • ∇ = 1 ≤ • ∇ = 1 ∈ Ω = 0 ∈ Γ The distance function = The level set function?
21. Yonsei University 21/00 Level Set Reinitialization = (1 − ∇ ) , 0 = () sign = −1, < 0 0, = 0 1, > 0 ∇ = 1 ∈ Ω = 0 ∈ Γ |∇| = 1 |∇| = 1 ≤ Do we solve this equation each iteration?
22. Yonsei University 22/00 Level Set Reinitialization = (1 − ∇ ) + ⋅ ∇ = = ∇ |∇| •
23. Yonsei University 23/00 Level Set Reinitialization •
24. Yonsei University 24/00 Level Set Reinitialization What We Have Done = − + ⋅ 2 − + + ⋅ = 0 () = 0, < − 1 2 1 + + 1 sin / , || ≤ 1, > + + ⋅ ∇ = Are we done?
25. Yonsei University 25/00 Contents • Motivation • Level Set Method • Numerical Schemes • Conclusion • Level Set Reinitialization
26. Yonsei University 26/00 Back to Equation = − + ⋅ 2 − + + ⋅ = 0
27. Yonsei University 27/00 Back to Equation = Σ | +1 − | +1 ≤ ≤
28. Yonsei University 28/00 Contents • Motivation • Level Set Method • Numerical Schemes • Conclusion • Level Set Reinitialization
29. Yonsei University 29/00 Advantange/Disadvantage • • • Γ , = 0 • •
30. Yonsei University 30/00 Summary of Algorithm (, 0) ( + ⋅ ∇ = 0) ( ⋅ ∇) = +1 (1 − ∇ )
31. Yonsei University 31/00 Reference • • • • •
32. Yonsei University 32/00 Reference (Image) • • • • • • • • • •
33. Yonsei University 33/00 Reference (Image) • •