Boundary layers are everywhere. We live within the Earth's planetary boundary layer. Airplanes exploit boundary layers to fly. Golf balls have dimples that alter boundary layer characteristics to maximize their flight time. So what are boundary layers?

Dimensionless lift coefficient and drag coefficient values permit comparisons between similar shapes moving through a fluid. Such comparisons are only valid if the Reynolds numbers are also equivalent.

Airplanes defy gravity. Formula 1 racing cars corner at incredible speeds generating lateral forces up to 4.5 times that of gravity. Yachts can circumnavigate the globe by wind power alone. These incredible feats are all due to the lift force generated by airfoils moving through air. Of course nothing comes for free; for lift, the cost is drag.

Computational Fluid Dynamics (CFD) is the collective term used to describe analysis techniques that simulate gas and liquid (fluid) flows.