3. Direct study

3.1 Compressible fluid turbomachinery family

Two turbomachines are geometrically similar when we can pass from one to the other by multiplying all linear dimensions by the same factor k, called the geometric similarity coefficient. The set of similar turbomachines forms a family characterized by constancy :

• ratios of all linear dimensions to a reference length which we choose to be equal to the rotor outer radius R ;

• homologous angles, in particular angles defining the position of both fixed and moving blades.

Consequently, a turbomachine of a given family is fully determined if only one linear dimension is known.