Vortex Flow Meters make use of a natural phenomenon that occurs when a Fluid flows around a bluff object. Eddies or Vortices are shed alternately downstream of the object. The frequency of the vortex shedding is directly proportional to the velocity of the liquid flowing through the meter.
The analogy of a golf ball moving through the air would be useful in describing vortex formation:
A slow moving putt barely displaces the molecules of air. The higher velocity of a chip shot causes irregular eddies to form behind the ball. The velocity associated with a drive is sufficient to cause a strong, regular vortex formation behind the ball
When a flowing medium strikes a non-streamlined bluff object, it separates, moves around the object and passes downstream.
At the point of contact with the object, vortex swirls separate from the body on alternating sides. This separation causes a local increase in pressure and a decrease in velocity on one side and a decrease in pressure and an increase in velocity on the opposite side. The alternating velocities generate alternating pressure forces on either side of the bluff body.
The frequency of these pressure changes is proportional to velocity.
The frequency of vortex shedding is directly proportional to the velocity of the flow in the pipe, which permits measurement of the flow rate by sensing the frequency of the vortex formation on the alternate sides of the bluff body.
Advantages:
1. Low wear
2. Low cost of installation
3. Sensitivity to variation is less in process condition
4. Applicable to wide range of temperature
Disadvantages:
1. Vibrations cause errors in measurement.
2. Not suitable for low flowrates
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