ABSTRACT
This chapter provides the description of the fundamental mechanisms which lead to the initial bubble formation. The formation of foams takes place when closely packed gas bubbles are generated within a foaming solution. Moreover, the foaming agents provide viscoelastic properties to the bubble surfaces, adding important interfacial stresses to the bubble formation process. The process of bubble formation involves the creation and deformation of a gas/liquid interface. The general physical mechanism behind the types of bubble generation processes is to locally drive the liquid into a supercritical state so that nucleation leads to the creation of small bubbles which then grow. The slow bubbling into a stationary liquid can be described rather easily, while the dynamic case is a highly complex problem due to the intricate coupling between the dynamic stresses and the bubble shape. The chapter discusses bubble blowing in confined "co-flow" and "cross-flow", bubble break up under shear, and bubble formation by gas entrainment.
