Non-dimensional numbers [Fluid Mechanics #5]

In this lecture we continue our consideration of dimensionality by studying Non-dimensional Numbers. These are widely used throughout Fluid Mechanics to define flow regime, let us know what we can exclude in analysis, and help us scale problems. The non-dimensional numbers today are all some Force compared to Inertia: (1) Euler number compares pressure and inertia, common for aerodynamics; (2) Reynolds number compares viscosity and inertia, commonly used for defining laminar and turbulence; (3) Froude number compares weight and inertia, which is most popular in large ship flows; (4) Weber number compares surface tension and inertia, for things like bubbles and droplets; and (5) the Mach number compares gas compression and inertia for supersonic high-speed aerodynamics.