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

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

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

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

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

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

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

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

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

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

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

Off-Axis Collisions Weber Number vs. Reynolds Number 700 m (Oh=0.00443) 300 m (Oh=0.00676) 150 m (Oh=0.00956) 75 m (Oh=0.01351) 10 m (Oh=0.0370) 2 mm (Oh=0.00262) Separation Region Coalescence Region 10 m (Oh=0.0370) 75 m (Oh=0.01351) 150 m (Oh=0.00956) 300 m (Oh=0.00676) 700 m (Oh=0.00443) X=1 (Grazing) X=0.9