Data Acquisition Web

A major milestone in the understanding of flow was reached in 1783 when the Swiss physicist Daniel Bernoulli published his Hydrodynamica. In it, he introduced the concept of the conservation of energy for fluid flows. Bernoulli determined that an increase in the velocity of a flowing fluid increases its kinetic energy while decreasing its static energy. It is for this reason that a flow restriction causes an increase in the flowing velocity and causes a drop in the static pressure of the flowing fluid.

Another, apparently not related milestone, Faraday's law of electromagnetic induction is the basis for the operation of the magnetic flowmeter. Over the past several years, the performance of magnetic flowmeters has improved significantly.

In 1883, the British mechanical engineer Osborne Reynolds proposed a single, dimensionless ratio to describe the velocity profile of flowing fluids.

In 1842, the Austrian physicist Christian Doppler discovered that, if a sound source is approaching a receiver, the frequency of the sound will appear higher. If the source and the recipient are moving away from each other, the pitch will drop. The ultrasonic Doppler flowmeter project a sound beam into a flowing stream containing reflectors such as bubbles or particles. The shift in the reflected frequency is a function of the average traveling velocity of the reflectors. This speed, in turn, could be used to calculate a flowrate.

The French civil engineer Gaspard Coriolis discovered in 1843 that the wind, the ocean currents, and even airborne artillery shells will all drift sideways because of the earth's rotation. The slow evolution of sensors and electronics delayed the creation of the first commercial Coriolis mass flowmeter until the 1970's.

Hungarian-American engineer Theodore von Karman noticed that rocks caused vortices in flowing water, and that the distances between these traveling vortices are constant, no matter how fast or slow the water runs. This is the theory behind the vortex flowmeter, which determines flow velocity by counting the number of vortices passing a sensor. Von Karman published his findings in 1954, and because by that time the sensors and electronics required to count vortices were already in existence, in 1968 the first swirlmeter was already available.