1. Collision & Separation of Liquid Drops: Modeling Off-axis Collisions
Saroka and Ashgriz

2. Observed Outcomes Head-on Off-axis Permanent Coalescence
Reflexive Separation
Off-axis
Stretching Separation then
Stretching Separation
Tearing or or

3. Mathematical Description
Fluid is laminar, incompressible with constant properties
No External Forces acting on Drops
Governing Equations (inside Drops)

4. Off-axis Collisions Coalescence (Water, We=25, Re=740, X=0.7)1 2 3 4 5 6 7 8 9 10 14 15 11 12 13 17 18 16 19 20

5. Off-axis Collisions Separation (Water, We=60, Re=1751, X=0.7)1 2 3 4 5 8 9 10 6 7 14 15 16 17 18 19 20 21 22 24 23 11 12 13
24.5

6. Off-Axis Collisions Internal Flow Patterns (We=60, Re=1751, X=0.7)
Y-Z Plane 1 3 4 5 2 6 7 8 9 10 11

7. Off-Axis Collisions Tearing (Water, We=56, Re=2392, X=0.73 and =0.5)1 2 3 4 5 8 9 10 6 7

8. Off-Axis Collisions Coalescence-Fragmentation Curves
Water: 300 m
Water: 700 m

9. Minor Axis Deformation Impact Number Variation
We=30 and Re=810
(Water, 300 m)
Red Curves: High Impact Number
(0.7  X  0.9)
Stretching-Separation
Green Curves: Moderate Impact Number
(0.3  X  0.6)
Stretching-Coalesence
Blue Curves: Low Impact Number
(0  X  0.2)
Coalesence
X=0
X=0.9
X=0.2
X=0.6
X=0.4
X=0.7

10. Major Axis Deformation Impact Number Variation
We=30 and Re=810
(Water, 300 m)
X=0.9
X=0.8
X=0.6
Red Curves: High Impact Number
(0.7  X  0.9)
Stretching-Separation
X=0
Green Curves: Moderate Impact Number
(0.3  X  0.6)
Stretching-Coalesence
X=0.7
Blue Curves: Low Impact Number
(0  X  0.2)
Coalesence
X=0.3

11. Major Axis Deformation Off-Axis Collisions
Sep.
Coal.
Sep.
Coal.
X=0.4
Water: 300 m
Water: 700 m

12. Off-Axis Collisions Weber Number vs. Reynolds Number
700 m (Oh= )
300 m (Oh= )
150 m (Oh= )
75 m (Oh= )
10 m (Oh=0.0370)
2 mm
(Oh= )
Separation Region
Coalescence Region
10 m (Oh=0.0370)
75 m (Oh= )
150 m (Oh= )
300 m (Oh= )
700 m
(Oh= )
X=1 (Grazing)
X=0.9