1. Sunny Ri Li, Nasser Ashgriz
Breakup Mechanisms, Fluid Velocity and Dimension Characteristics in Impinging Liquid Jets
Sunny Ri Li, Nasser Ashgriz
Department of Mechanical and Industrial Engineering
University of Toronto

2. Multiphase Flows and Spray Systems Laboratory
Introduction
When two cylindrical jets of equal diameters collide they form an expanding sheet in the plane at a right angle to the plane containing the axes of the two jets.
Multiphase Flows and Spray Systems Laboratory
November 18, 2018

3. Experimental Method and Apparatus
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November 18, 2018

4. Multiphase Flows and Spray Systems Laboratory
Breakup Regimes
Pre-sheet formation
Regime I:
Capillary Instability
(Closed-rim sheet)
Smooth sheet
Ruffled sheet
Open-rim sheet
Regime II:
Kelvin-Helmholtz
instability
Turbulent sheet
Regime III:
Impact-wave
1. High-frequency circumferential waves
2. Very high Reynolds number
3. High impinging angle
Multiphase Flows and Spray Systems Laboratory
November 18, 2018

5. Breakup Regimes - Critical Single-Jet & Impingement Reynolds Numbers
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November 18, 2018

6. Breakup Regimes - Critical Sheet Reynolds Numbers
…..Thickness of the impact region
….Edge thickness of the sheet
120 deg.
90 deg.
Impinging angle: 60 deg.
Multiphase Flows and Spray Systems Laboratory
November 18, 2018

7. Surface Velocity - Experimental Method
The surface velocity, which is defined here as the stream velocity on the sheet, was determined by measuring the wave motion on the surface.
Measurement was made on two angular positions on the sheet: 0 and 25 degree.
Multiphase Flows and Spray Systems Laboratory
November 18, 2018

8. Surface Velocity - Distribution of Surface velocity
(Impinging angle 90 deg.)
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November 18, 2018

9. Dimensional Characteristics - Equations
The following equations are based on the work of Taylor [1959] and Ibrahim [1991], which assumed the fluid velocity throughout the sheet is equal to the mean jet velocity.
….Maximum length
….Maximum width
Where β can be obtained by solving
Multiphase Flows and Spray Systems Laboratory
November 18, 2018

10. Dimensional Characteristics - Total Length
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November 18, 2018

11. Dimensional Characteristics - Maximum Width
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November 18, 2018

12. Dimensional Characteristics - Review of Early Theory
Taylor [1959] assuming the fluid velocity on the sheet equal to jet velocity
To retain its validity for non-uniform fluid velocity on the sheet,
: Fluid velocity on the sheet
: Edge thickness of the sheet with non-uniform velocity distribution
: Edge thickness of the sheet with uniform velocity distribution
When ,
When ,
Multiphase Flows and Spray Systems Laboratory
November 18, 2018

13. Dimensional Characteristics – Edge Thickness
Ibrahim [1991]:
0.837 mm
0.084 mm
1) The edge thickness of the sheet thickness cannot be predicted by assuming uniform velocity on the sheet.
2) The real edge thickness is has higher order of magnitude than the ideal thickness.
3) eliminates the drawback, hereby making the subsequently derived equations still valid.
Multiphase Flows and Spray Systems Laboratory
November 18, 2018

14. Multiphase Flows and Spray Systems Laboratory
Conclusions
Three major breakup regimes of the liquid sheet were identified in this work, namely capillary instability regime, Kelvin-Helmholtz instability regime and impact wave regime.
The distribution of fluid velocity on the sheet was examined and found not uniform throughout the sheet.
The dimensional characteristics of the spray sheet were investigated by reviewing early theories. It was found that the theories can predict the shape of the sheet but not the sheet thickness.
Multiphase Flows and Spray Systems Laboratory
November 18, 2018