1. Polish Academy of Sciences Institute of Fundamental Technological Research http://fluid.ippt.gov.pl/conex Break-up of liquid jet in co-flow experimental study S. Błoński, P.Korczyk, T.A. Kowalewski

2. MOTIVATION Visualization of liquid jet break-up and droplet formation for co-flow Glycerol jet in air

3. EXPERIMENTAL SETUP Epifluorescent microscope – Nikon ECLIPSE E-50i High Speed CMOS Camera – PCO 1200.hs (up to 40720 fps; 636fps in full resolution 1280x1024) Pressure system (gas cylinder with argon, pressure regulator and conduits, pressure sensor Two precision syringe pumps Geometry for jet breakup observation channel size: 30 x 8 x 10 mm needle diameter: 0.5 mm Qe = 1 - 5cm 3 /s Qj = 5 - 30mm 3 /s

4. EXPERIMENTAL SETUP

5. Used materials: 1.water-alcohol mixture (5:2) + S50 silicone oil + 1%wt SDS 2.water-alcohol mixture (5:2) + S500 silicone oil + 1%wt SDS Used microscope lens: 4x/NA0.13/WD17.1mm Liquid jet break-up visualization Used geometry: OilQe [cm3/s]V e [cm/s]Q j [mm3/s]V j [mm/s] S50 (50mPas)1.08 – 3.572.16 – 7.1422 – 33112.2 – 168.3 S50 (500mPas)0.92 – 1.721.84 – 3.445.5 – 3328.1 – 168.3 V e and V j – mean flow velocities based on the channel cross-section and inner nozzle diameter, respectively

6. Liquid jet break-up visualization Q j = 22 mm 3 /s Q e = 1.08 cm 3 /s Break-up period: 60 ms Q j = 33 mm 3 /s Q e = 1.08 cm 3 /s Silicone oil jet S50 Image width corresponds to 3.6mm

7. Liquid jet break-up visualization S50 oil + water-alkohol + SDS 500 fps Q j = 22 mm 3 /s; Q e = 1.1 cm 3 /s 3.6 mm

8. Liquid jet break-up visualization S50 oil + water-alkohol + SDS 500 fps Q j = 33 mm 3 /s; Q e = 1.1 cm 3 /s 3.6 mm

9. Liquid jet break-up visualization S500 oil + water-alkohol + SDS 500 fps Q j = 28 mm 3 /s; Q e = 1.3 cm 3 /s 3.6 mm

10. Liquid jet break-up visualization Long, cylindrical jet Silicone oil jet S50 Q j = 22 mm 3 /s Q e = 2.7 cm 3 /s Image width corresponds to 3.6mm Disturbed jet

11. Liquid jet break-up visualization Q j = 33 mm 3 /s Q e = 1.3 cm 3 /s Period of the capillary wave: 60 ms Filament shortly before droplet separation Q j = 14 mm 3 /s Q e = 1.47 cm 3 /s Break-up period: 240 ms Silicone oil jet S500 Image width corresponds to 3.6mm

12. Liquid jet break-up visualization S50 oil + water-alcohol + 1%wt SDS 500 fps Q j = 33 mm 3 /s; Q e = 2.7 cm 3 /s 3.6 mm

13. Liquid jet break-up visualization S50 oil + water-alcohol + 1%wt SDS 500 fps Q j = 33 mm 3 /s; Q e = 5 cm 3 /s 3.6 mm

14. CONCLUSIONS The capillary break-up of the liquid jet in co-flow is used to produce single droplets. Well controlled production of single micro-droplets is necessary for studying accumulation of nano- particles at the interface, the main target of the project. The experiments performed indicated that small droplets (1um) are created as satellites during fluid-threads break-up. The process of a micro-thread formation was previously observed and investigated [Kowalewski, Fluid Dyn. Res. 1996] for break-up of viscous jets in air. Similar process is found in the present study for two-liquids system. A hydrodynamic separation of small satellites created after the thread break-up is perhaps the simplest method of utilizing jet break-up for micro-droplets production.