Formation of chain clusters during bubble motion from a single capillary in an inclined pipe

The sizes and rise velocity of bubbles in a stationary liquid in an inclined channel with a circular cross-section at various gas flow rates through a capillary were determined (3.0 $\div$ 5.5 ml/min). The sizes and velocity of gas bubbles was studied by shadow photography. It is shown that in the range of channel inclination angles 40 $\div$ 60$^{\circ}$, the formation of stable bubble structures-clusters consisting of bubbles of the same size (1.5 $\div$ 1.8 mm) – can be formed. In modes without the formation of chain clusters, the average diameter of gas bubbles increased (2.0 $\div$ 2.2 mm) due to their coalescence.