Velocimetry

[3] Methods similar to da Vinci's were carried out for close to four hundred years due to technological limitations.

One notable instance of this is Ludwig Mach using particles unresolvable by the naked eye to visualize streamlines.

[4] Another notable contribution occurred in the 20th century by Étienne-Jules Marey who used photographic techniques to introduce the concept of the smoke box.

[3] Today the basic ideas established by Leonardo are the same; the flow must be seeded with particles that can be observed by the method of choice.

The seeding particles depend on many factors including the fluid, the sensing method, the size of the measurement domain, and sometimes the expected accelerations in the flow.

This noise is created by the high speed mixing of hot jet exhaust with the ambient temperature of the environment.

[13] Additionally, Doppler velocimetry enables noninvasive techniques of determining whether fetuses are the proper size at a given term of pregnancy.

[14] Velocimetry has also been applied to medical images in order to obtain regional measurements of blood flow and tissue motion.