45
4.1 Introduction
When crude oil enters into seawater from a pipeline or a well, drop formation will
occur in different ways based on the characteristics of the discharge. In general, oil
drop formation is governed by the relation of stabilizing forces (interfacial tension,
viscosity) versus destabilizing forces such as turbulence within the oil and the water
phase, friction and cavitation (Lefebvre and McDonell 2017). There are several
studies distinguishing a number of different flow regimes, ranging from the formation of single drops at the exit geometry to full atomization of a jet (Masutani and
Adams 2001; Boxall et al. 2012; Ohnesorge 1936; Lefebvre and McDonell 2017).
Originally, Ohnesorge (1936) identified four different regimes (see Fig. 4.1):
0. Formation of individual drops at the nozzle without jet formation.
I. Breakup of a cylindrical jet caused by Rayleigh instability.
II. Breakup caused by sinuous waves along the jet.
III. Atomization of the jet due to turbulent breakup.
The different regimes are distinguished using the relation between the dimensionless Reynolds number (Re)
Re
D
u
=
⋅ ⋅
ρ
η
l
l
l
(4.1)
Fig. 4.1 Different breakup/flow regimes of Louisiana sweet crude oil discharged into artificial
seawater at 150 bar, 20 °C from a 1.5 mm nozzle. Volume flow increases from left to right. Far left:
regime (0), individual drop formation. Mid left: regime (I), Rayleigh instability. Mid right: regime
(II), sinuous wave breakup. Far right: regime (III), atomization, turbulent breakup
4 Jet Formation at the Spill Site and Resulting Droplet Size Distributions
4.1 Introduction
When crude oil enters into seawater from a pipeline or a well, drop formation will
occur in different ways based on the characteristics of the discharge. In general, oil
drop formation is governed by the relation of stabilizing forces (interfacial tension,
viscosity) versus destabilizing forces such as turbulence within the oil and the water
phase, friction and cavitation (Lefebvre and McDonell 2017). There are several
studies distinguishing a number of different flow regimes, ranging from the formation of single drops at the exit geometry to full atomization of a jet (Masutani and
Adams 2001; Boxall et al. 2012; Ohnesorge 1936; Lefebvre and McDonell 2017).
Originally, Ohnesorge (1936) identified four different regimes (see Fig. 4.1):
0. Formation of individual drops at the nozzle without jet formation.
I. Breakup of a cylindrical jet caused by Rayleigh instability.
II. Breakup caused by sinuous waves along the jet.
III. Atomization of the jet due to turbulent breakup.
The different regimes are distinguished using the relation between the dimensionless Reynolds number (Re)
Re
D
u
=
⋅ ⋅
ρ
η
l
l
l
(4.1)
Fig. 4.1 Different breakup/flow regimes of Louisiana sweet crude oil discharged into artificial
seawater at 150 bar, 20 °C from a 1.5 mm nozzle. Volume flow increases from left to right. Far left:
regime (0), individual drop formation. Mid left: regime (I), Rayleigh instability. Mid right: regime
(II), sinuous wave breakup. Far right: regime (III), atomization, turbulent breakup
4 Jet Formation at the Spill Site and Resulting Droplet Size Distributions