Vortex shedding von Karman effect flow measurement.
A vortex flowmeter makes use of the von Karman effect principle where vortices are created downstream from a bluff body or shedder bar. A sensor is mounted in an optimum position behind the bluff body obstruction where the vortices are created and measures the oscillation generated in the flow. The resulting frequency measured is directly proportional to the flow velocity.
Vortices are created when a fluid flows around an obstruction. As the fluid closest to the obstruction passes around the shedding obstruction it will speed up, and the pressure will drop. This effect diminishes as you move further away from the boundary layer where the fluid meets the obstruction.
As fluid flow increases the vortices grow in size and eventually will begin to detach from the boundary layer creating alternating whirlpools on either side of the shedder. The alternating whirlpools cause pressure fluctuations to develop, as low and high pressure pockets pass by the sensor.
Since the vortex shedding occurs at repeatable intervals, the sensor will convert the resulting increase and decrease in pressure to a frequency signal.
Glossary of Sensor Technology technical terms
- BFSG – Bonded Foil Strain Gauge
- Bourdon Tube
- Capacitive Fluid Level Measurement
- Ceramic Pressure Sensors
- Conductive Fluid Level Detection
- Doppler Effect Flow Measurement
- Float Fluid Level Detection
- LVDT – Linear Variable Differential Transformer
- Paddle Wheel Sensor
- Piezoresistive Strain Gauges
- Positive Displacement Flow Measurement
- Radar Distance Sensing
- SOI – Silicon on Insulator
- Strain Gauge
- Thin Film
- Transit Time Flow Measurement
- Turbine Rotor Sensor
- Ultrasonic Distance Sensing
- Ultrasonic Flow Velocity Sensors
- Vibrating Tuning Fork Fluid Level Detection
- Wheatstone Bridge Strain Gauge
