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. It is obvious enough that, to obtain meaningful results from model tests, the model must be geometrically similar to the full-scale version. Much less obvious are the similarity conditions which must be satisfied within the flowing fluid to ensure that the model tests replicate what happens at full-scale. Such considerations are addressed in this chapter. Physical similarity in fluid mechanics is discussed, important dimensionless groups are introduced, the methods of dimensional analysis are considered and the chapter concludes with some applications of similarity principles to model testing.
