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

MOTIVATION

Visualization of liquid jet break-up and droplet formation for co-flow

Glycerol jet in air

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 observationchannel size: 30 x 8 x 10 mm

needle diameter: 0.5 mm

Qe = 1 - 5cm3/s

Qj = 5 - 30mm3/s

EXPERIMENTAL SETUP

Used materials:

1. water-alcohol mixture (5:2) + S50 silicone oil + 1%wt SDS2. 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:

Oil Qe [cm3/s] V e [cm/s] Qj [mm3/s] V j [mm/s]

S50 (50mPas) 1.08 – 3.57 2.16 – 7.14 22 – 33 112.2 – 168.3

S50 (500mPas) 0.92 – 1.72 1.84 – 3.44 5.5 – 33 28.1 – 168.3

Ve and Vj – mean flow velocities based on the channel cross-section and inner nozzle diameter, respectively

Liquid jet break-up visualization

Qj = 22 mm3/sQe = 1.08 cm3/s

Break-up period: 60 ms

Qj = 33 mm3/sQe = 1.08 cm3/s

Silicone oil jet S50Image width corresponds to 3.6mm

Liquid jet break-up visualization

S50 oil + water-alkohol + SDS500 fps

Qj = 22 mm3/s; Qe = 1.1 cm3/s

3.6 mm

Liquid jet break-up visualization

S50 oil + water-alkohol + SDS500 fps

Qj = 33 mm3/s; Qe = 1.1 cm3/s

3.6 mm

Liquid jet break-up visualization

S500 oil + water-alkohol + SDS500 fps

Qj = 28 mm3/s; Qe = 1.3 cm3/s

3.6 mm

Liquid jet break-up visualization

Long, cylindrical jet

Silicone oil jet S50Qj = 22 mm3/sQe = 2.7 cm3/s

Image width corresponds to 3.6mm

Disturbed jet

Liquid jet break-up visualization

Qj = 33 mm3/sQe = 1.3 cm3/s

Period of the capillary wave: 60 ms

Filament shortly before droplet separation

Qj = 14 mm3/sQe = 1.47 cm3/s

Break-up period: 240 ms

Silicone oil jet S500Image width corresponds to 3.6mm

Liquid jet break-up visualization

S50 oil + water-alcohol + 1%wt SDS500 fps

Qj = 33 mm3/s; Qe = 2.7 cm3/s

3.6 mm

Liquid jet break-up visualization

S50 oil + water-alcohol + 1%wt SDS500 fps

Qj = 33 mm3/s; Qe = 5 cm3/s

3.6 mm

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.