Vahid Farhangmehr

In this experimental investigation, the spark-generated bubble dynamics inside a vertical rigid tube (cylinder) filled with water is studied using high-speed photography. It is observed that, for all cases, the bubble behavior is influenced to some extent by the proximity of the tube walls. The presence of the tube greatly increases the bubble lifetime and the buoyancy plays an important role. The bubble center moves upwards at the first stage of the growth phase due to the buoyancy. The buoyancy also leads to the formation of an initially upward (first) jet originating from the bottom part of the bubble. The first stage of bubble contraction or collapse phase depicts the flattening of the top part of the bubble. A (second) jet is then initiated and it develops downwards; the bubble becomes toroidal and impacts on the bubble’s bottom surface. As the two jets develop respectively in the growing and collapsing phases of the bubble evolution, the absolute velocity of the rising jet is higher than that of the downward jet. We also consider the change in the bubble dynamics when it is placed off the center of the tube (with eccentricity)