Measuring air flow in an HVAC duct can be a tricky business. Paddle wheel and turbine flow meters introduce not only resistance but maintenance issue due to accumulated dust and debris.

Some vehicles use a mass air flow sensor instead of a MAP sensor to measure the amount of air going to the intake manifold.

The study of Ricci flow and the stability of Einstein manifolds is a significant area in differential geometry, focusing on the behavior of geometric structures under certain transformations.