For a properly specified fluid flow problem or situation, the differential equations of fluid motion, the fluid’s constitutive and thermodynamic properties, and the boundary conditions may be used to determine the dimensionless parameters that govern the situation of interest even before a solution of the equations is attempted

Dimensional Analysis — Using physical quantities / units to learn about its relationship with other physical quantities

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└─ applicable for developing scaling laws, interpreting experiments, simplification, ...

→ Nature is independent of our system of units

└─ All correct physical relations can be stated in dimensionless form → dimensional analysis

└─ In any comparison, the units of items must be the same → principle of dimensional homogeneity