An experimental setup to study the effects of jet separation and impact angles on the final jet structure have been designed.
Figure 1: Snapshot of colliding bubbly jets, with the definition of the separation s and the impact angle.
The bubble generation method is based on the creation of a regular slug-flow prior to injection. This method is insensitive to gravity level for low Bond numbers. Hence, it is an efficient method to generate and control bubbles both in normal gravity and in a microgravity environment.
Figure 2: Bubble generation method. Gas is injected from top, and liquid is injected from left.
Velocity profile:
The momentum flux J can be regarded as the main parameter that characterizes the jet structure,
which can be approximated, taking into account both gas and liquid phases, as
The velocity profile of the jets can be written as
Figure 3: Collapse of bubble velocity measurements. Circles and squares correspond to J=54 gcm/s2 and J=22 gcm/s2 respectively.
Bubble size distribution:
In order to predict the bubble size distribution, one could consider the population balance method, which writes
where n is the local number density, dB is the bubble diameter, vB is the bubble velocity and S is the source term, due to coalescence or breakup events.
Dividing the bubble sizes into N classes, the population balance equation for the i-th bubble class becomes
Neglecting the breakup events, the source term for the i-th bubble class becomes
Under these conditions, a log-normal distribution can describe the considered bubble size distribution
Figure 4: Probability distribution of normalized bubble diameters.
