58
mode is formed by those drops where no or very few gas bubbles nucleated. The
smaller mode consists of drops that were split up when the gas bubbles nucleated,
expanded and exited the oil drop. That gas bubbles did in fact form and expand prior
to the measurement point is evident from the footage of the surveillance camera
(Fig. 4.3), though those bubbles were not captured by the measurement system in
sufficient numbers to allow for quantification. This interpretation of the bimodality
is supported when plotting the median volume diameter of both modes over the
modified Weber number (Fig. 4.4). While the d v50 of the larger mode lies in approximately the same range as the quasi-isobaric live oil from Malone et al. (2018) and is
significantly enhanced compared to the “dead” oil and the model prediction by
Johansen et al. (2013), the d v50 of the smaller mode is significantly smaller than
either the “live” or the “dead oil”. In terms of the TKE, the pressure drop from the
oil reservoir and subsequent outgassing of methane from the oil provide an additional energy source in the jet leading to further breakup of the oil droplet and consequently a smaller median drop diameter.
Plotting the volume median diameters from both the quasi-isobaric and the
“pressure drop” experiments at Hamburg University of Technology over the maximum TKE according to Zhao et al. (2014)
ε u
u D
=
⋅
0 003
3
.
/
l
(4.11)
reveals the good correlation of the different data sets to the assumptions on the
effects of gas dissolution and pressure drop/outgassing (Fig. 4.5).
SUHVVXUH
GLVWDQFH WUDYHOOHG
JDVYRLG IUDFWLRQ
RXWJDVVLQJRI & &
EXEEOH IRUPDWLRQ ZLWKLQ GURS
ODUJHLQVWDEOH GURSV
SDUWLFOH EUHDNXS
JDVEXEEOHV OHDYH
RLO GURS DW VXUIDFH
FRUH GURS PLFUR GURSOHWV
DQG JDVEXEEOHV
HPXOVLRQ IRUPDWLRQ
Fig. 4.2 Possible effects of oversaturation and outgassing on the drop formation and drop size
distribution after a rapid pressure drop (not to scale)
K. Malone et al.
mode is formed by those drops where no or very few gas bubbles nucleated. The
smaller mode consists of drops that were split up when the gas bubbles nucleated,
expanded and exited the oil drop. That gas bubbles did in fact form and expand prior
to the measurement point is evident from the footage of the surveillance camera
(Fig. 4.3), though those bubbles were not captured by the measurement system in
sufficient numbers to allow for quantification. This interpretation of the bimodality
is supported when plotting the median volume diameter of both modes over the
modified Weber number (Fig. 4.4). While the d v50 of the larger mode lies in approximately the same range as the quasi-isobaric live oil from Malone et al. (2018) and is
significantly enhanced compared to the “dead” oil and the model prediction by
Johansen et al. (2013), the d v50 of the smaller mode is significantly smaller than
either the “live” or the “dead oil”. In terms of the TKE, the pressure drop from the
oil reservoir and subsequent outgassing of methane from the oil provide an additional energy source in the jet leading to further breakup of the oil droplet and consequently a smaller median drop diameter.
Plotting the volume median diameters from both the quasi-isobaric and the
“pressure drop” experiments at Hamburg University of Technology over the maximum TKE according to Zhao et al. (2014)
ε u
u D
=
⋅
0 003
3
.
/
l
(4.11)
reveals the good correlation of the different data sets to the assumptions on the
effects of gas dissolution and pressure drop/outgassing (Fig. 4.5).
SUHVVXUH
GLVWDQFH WUDYHOOHG
JDVYRLG IUDFWLRQ
RXWJDVVLQJRI & &
EXEEOH IRUPDWLRQ ZLWKLQ GURS
ODUJHLQVWDEOH GURSV
SDUWLFOH EUHDNXS
JDVEXEEOHV OHDYH
RLO GURS DW VXUIDFH
FRUH GURS PLFUR GURSOHWV
DQG JDVEXEEOHV
HPXOVLRQ IRUPDWLRQ
Fig. 4.2 Possible effects of oversaturation and outgassing on the drop formation and drop size
distribution after a rapid pressure drop (not to scale)
K. Malone et al.