1. Progress in Computational Microfluidics Using the Code TransAT June 2013 ASCOMP www.ascomp.ch lakehal@ascomp.ch

3. IIIa-Applications: Microchannel heat sink →

4. Microchannel heat sink

5. a) D=2 mm b) D=1 mm Various flow regimes were found in lab, Chen & Karayiannis, I. J. M.F., 2006. (Courtesy, Uni. Brunel, UK)

6. ▫ Use the data of Brunel University (Chen & Karayiannis, 2006) ▫ Various two-phase flow regimes in D = 0.5, 1, 2mm pipes Table 1: Inflow velocity and void fraction conditions Case  U G (m/s) U L (m/s) Domain Water Bubbly Slug Bubbly/slug 0.0 0.205 0.376 0.480 0.0 0.66 1.57 1.1 1 X 70 1 X 40 1 X 60

7. Bubbly flow: jG = 0.66, jL = 1.11 m/s;  = 0.205 Slug flow: jG = 0.66, jL = 1.11 m/s;  = 0.376 Slug train flow: jG = 1.57, jL = 1.11 m/s;  = 0.498 Churn flow: jG = 4.42, jL = 1.11 m/s;  = TransAT simulations CLICK ON MOVIES TO PLAY

8. Fluent vs. TransAT Exp. Fluent TransAT

9. 5 times higher heat transfer for slugtrain Nusselt number Instantaneous NusseltMean Nusselt

10. Mechanistic Model: The model is inspired from the Higbie’s Surface Renewal theory, where eddies ‘wash’ the surface exchange at a specific frequency rate (1/  ). Here the bubbles/slugs plays the same role as the eddies in turbulent flows. If we scale the Higbie’s relationship introducing now the bubble/slug frequency and size as the characteristic time & length scales (  & L GB ), we find Nu to obey the turbulent correlation of Dittus-Boelter (Colburn), even for a laminar flow. Mechanistic modelling

11. IIIb-Applications: Ultra thin film dominated flows →

12. a-b) Lodging state c) bubble lodged in one of the branches (Calderon et al. 2004). Thin-film in bio-micro systems

13. Thin-film SGS Modelling (Taylor’s..) No thin-film model Thin-film SGS model CLICK ON MOVIES TO PLAY

14. RAINDANCE Inc., USA Droplet control in micromixer

15. RAINDANCE Inc., USA CLICK ON MOVIES TO PLAY

16. IIIc-Applications: Contact angle driven flows →

17. Droplet impact – 2D examples adherencebouncing splashing CLICK ON MOVIES TO PLAY

18. Droplet impact – 3D example CLICK ON MOVIES TO PLAY

19. Effect of contact angle: dynamic vs. static CA 2D: CA = 100, We = 52 and Re = 3245. 3D: CA = 100; We = 548 and Re = 11412. Caviezel et al., Microfluid & Nanofluid Journal, 2008.

20. Droplet rebounding on a hot surface (Leidenfrost phenomena; Imperial college) Exp: Wachters et al., Chem. Eng. Science, 1966 CFD: Chatzikyriakou et al., Appl. Therm Eng., 2009

21. Droplet returning to equlibrium by the action Of the contact angle (triple line) Narayanan & Lakehal, Proc. NSTI Boston, paper 770, 2006. CLICK ON MOVIE TO PLAY

22. Bubble growth dynamics from orifices S. Di-Bari and A. Robbins, Trinity College Dublin 2011. Bubble growth mechanism in (a) expansion and (b) detachment sequences (Buyevich, 1996)

23. Bubble growth dynamics from orifices S. Di-Bari and A. Robbins, Trinity College Dublin 2011. Photographic sequence of bubble growth in water from a 1 and 1.6 mm orifice diameter compared with TransAT (red line). Flow rate =10 mlph.

24. Bubble growth dynamics from orifices Comparison of dimensional and dimensionless volumetric growth rate (top); motion of the centre of gravity (bottom) at 10 mlph. Contact angle comparison

25. Exp: Cubaud, T., et al. Physical Review E -, 2005. Droplets in a Bubble Dispenser (Jie & Attinger, Columbia Uni, NY)

26. Droplets in a Bubble Dispenser (Jie & Attinger, Columbia Uni, NY) CLICK ON MOVIES TO PLAY

27. Fluent vs. TransAT

29. Droplet detachment and tear-off The Top-spot experiment Glatzel et al., Comp. Fluids, 2008 Pressure pulse at the inlet from experiments.

30. TransAT provides both droplet tear-off & miniscus formation Fluent, CFD-ACE, CFX vs. TransAT

31. Droplet detachment and tear-off (harmonic) CLICK ON MOVIES TO PLAY

32. Dripping CLICK ON MOVIES TO PLAY

33. IIId-Applications: Falling films and encapsulation →

34. Falling film (Base test case with analytical sol.)

35. Falling film (Gulati & Buongiorno, MIT) TransAT : Predicts roll & capillary waves correclty Nosoko et al., Chem. Eng. Science, 51, 1996

36. Falling film simulations Serial No. Re N f x 10 -12 N N hp from Nosoko et al. from TransAT with implicit surface tension formulation Deviation of TransAT from Nosoko et al. 12043.88626.28.3887.8216.76% 2400.1614689.49.3609.2471.21% 3500.2018742.610.7839.37113.09% 41030.0520994.915.87613.28416.32% 51030.4100994.917.38617.0132.15% CLICK ON MOVIE TO PLAY

37. Falling liquid film with heat transfer CLICK ON MOVIES TO PLAY

38. AMR: Pipetting

39. Frequency effectViscosity effect Shear thinning Jet diameter: 1mm Frequency: 200-300 Hz Viscosity: 85 mPa Micro-encapsulation of drug pills (INOTECH Switzerland) CLICK ON MOVIES Exp.

40. Micro-contact processing Courtesy IBM Zurich

41. IIIe-Applications: Phase field: for phase separation or microfluidics, high-density ratio flows ? →

42. Phase Separation: Viscoelastic Effects H model in TransAT

43. Droplet breakup in a T-Junction (phase field) CLICK ON MOVIES TO PLAY Exp: Julien, Ching, Cohen, Menetrier, Tabeling, Phys. Fluids, 2009 Regime C

44. Droplet breakup in a T-Junction (level set) CLICK ON MOVIES TO PLAY

45. Droplet breakup in a T-Junction (level set)

47. IIIf-Applications: Varia, possible & impossible now ! →

48. Marangoni forces Marangoni effects CLICK ON MOVIES TO PLAY

49. Electrowetting effects Berge or Lippman-Young relation CLICK ON MOVIES TO PLAY

50. Bubble oscillation under external forcing CLICK ON MOVIES TO PLAY

51. Die Coating

52. Grid & Results IST grid (immersed surfaces technique); 28’800 cells Shear thinning is observed in the liquid only