Bubble velocity lump discontinuity in polyacrylamide solutions: a photographic study

It has been established that in the presence of elastic as well as surface tension forces, a jump can occur in the bubble velocity-bubble volume plot. It was proposed that this phenomenon was the result of an elastic instabil ity at the bubble interface, which drastically changes the local boundary c onditions. The origin of this change was mainly attributed to the magnitude of the elastic forces, which can extract surface active impurities at the gas-liquid interface. The purpose of this paper is to present photographic evidence of this hypothesis and to confirm past results.