It is unclear how the previously formed bubble influences the growth of the next bubble forming at the orifice and leads to different bubbling regimes.
Based on the visual observations, the regimes of bubble formation were qualitatively classified as period-1 (single) bubbling, period-2 bubbling, that is, bubbling with pairing (bubbles coalesce far above the orifice) and with coalescence (bubbles coalesce at the orifice itself before detachment), bubbling with triple or quadruple coalescence (period-3 or period-4 bubbling) and finally the chaotic bubbling (Leibson et al.
Most of the models developed to predict bubble formation are based on the assumption of single bubbling and do not consider different regimes of bubble formation (for example, see the review by Kumar and Kuloor (1970)).
Depending on the bubbling regime, the detachment times of successive bubbles were measured using the recorded frames with an accuracy of [+ or -] 1 ms.
At lower gas flow rates, bubbles were formed above the orifice at a regular interval of time and this regime of bubbling is known as the single bubbling regime (see Figure 4a).
The next bubble grows at the orifice without any influence of the wake behind the leading bubble and the period-2 bubbling repeats as shown in Figure 4b.
When a third bubble coalesces with the bubble that resulted from the period-2 bubbling with coalescence at the orifice as described above, it is known as triple coalescence (referred to as period-3 bubbling here).
In one of the literature reports (Tufaile and Sartorelli, 2000), a period-4 bubbling regime that occurs due to coalescence of the third and fourth bubbles with a bubble cluster resulting from period-2 bubbling with coalescence at the orifice was also reported.
After the period-3 or period-4 bubbling regime, the chaotic bubbling regime can be observed with further increase in the gas flow rate.
Concerned about athletes' safety, the Lancaster school board has voted unanimously to resurface the floor of the New Vista Middle School gym because of bubbling
in the polymer, officials said Wednesday.