ABSTRACT
In fluid mechanics the concept of physical similarity and the process of dimensional analysis are closely intertwined. A large part of the progress made in the study of fluid mechanics and its engineering applications has come from experiments conducted on scale models. Physical similarity is a general term covering several different kinds of similarity. Geometric similarity is perhaps the most obvious requirement in a model system designed to correspond to a given prototype system. Since the boundaries consist of streamlines, kinematically similar flows are possible only past geometrically similar boundaries. Dynamic similarity produces geometric similarity of the flow patterns. There are many instances of flow that is affected only by viscous, pressure and inertia forces. The chapter considers flow in which the significant forces are gravity forces, pressure forces and inertia forces. It deals with a small but important collection of independent dimensionless groups, including the Reynolds number, Mach number, Froude number and Weber number.
