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Vortex Flow Meters

Water (1)

Yokogawa released the world's first vortex flowmeter in 1968. Thanks to its long-term stability and high accuracy, our customers have achieved significant improvements in productivity over the past forty years. In response to ever changing market needs, Yokogawa has gone on to release high temperature, cryogenic, dual-sensor, reduced bore, and FOUNDATION Fieldbus communication versions of this product.

Vortex Timeline (2)

      Yokogawa's forty+ years of Vortex Flowmeter innovation.

Vortex Flow Meters - Principle of Operation

Vortex Flow Meters use the Von Karman Effect to measure the rate of flow of a fluid or gas.

What is the Von Karman Effect?

Early in the 20th century, a Hungarian-American mathematician and physicist, Theodore von Karman, discovered that a fluid or gas flowing perpendicularly pass a bluff body would generate alternating vortices on both sides of the body.  The path of these vortices is called the Von Karman Street.

Von Karman (3)

Von Karman found that if the frequency of these vortices was measured, that the frequency is proportional to the flow velocity that is generating the vortices. This frequency is called the Karmen Vortex Frequency. The relationship of the fequency and the flow velocity can be mathematically expressed with the following formula:

Vortex Formula (3)

From the equation, we can see that the frequency is proportional to the velocity. If we can measure the frequency (f), know the Strouhal number (St), know the shedder bar width (d); we can solve for v (velocity).

Vortex Formula 2 (1)

How do we measure the frequency of the vortices?

As vortices form and pass the shedder bar (the bluff body), they create a low pressure as compared to the rest of the fluid. This low pressure produces a differential pressure (dp) across the shedder bar. The high pressure side of the dp exerts stress on the shedder bar in the direction of the low pressure. As the location of the low pressure side alternates due to the vortices switching from side-to-side, the change in direction of the exerted force causes the shedder bar to oscillate. This oscillation is equal to the Karmen Vortex Frequency

Vortices 2 (4)

There are several methods in the marketplace to measure the oscillation. Diaphragms or capacitance sensors are two of the more common; but, the best method is the use of Piezo-electric crystal sensors. These sensors, when compressed, produce an electric signal that can be sent to the Flow meter's electronics. Now that the Karmen Vortex Frequency is measured (and we know the St and d), the flow meter electronics can do simple calculations to determine volumetric flow through the pipe.

What are the advantages of using Vortex Flow Meters?

  • High Accuracy

The accuracy of the vortex flow meter is ±1% (pulse output) of the indicated value for both liquids and gases and is higher compared to orifice flow meters. For liquids, an accuracy of ±0.75% is available depending on the fluid type and their conditions.

  • Wide Rangeability

Rangeability is defined as the ratio of maximum value to minimum value of the measureable range. It is braod rangeability the allows vortex flow meters to operate in processes where the measuring point may fluctuate greatly.

  • Output is Proportional to Flow Rate

Since the output is directly proportional to the flow rate (flow velocity), no square root calculation is needed, while orifice flow meters require square root calculations.

  • No Zero-point Fluctuation

Since frequency is poutput from the sensor, zero-point shift does not occur.

  • Minimal Pressure Loss

Since only the vortex shedder is placed in the pipe of the vortex flow meter, the fluid pressure loss due to the small restriction in the flow piping is small compared with flow meter a having an orifice plate.



  • Fieldbus technology introduced to realize predictive and preventive maintenance.
  • ISAE to improve the reliability of diagnosis and parameter setting, utilizing data collected by PRM.
  • Yokogawa's integrated solution contributed to reliable and efficient operation.
  • All the instrument information is fully integrated with the instrument management system.

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Sensors and controllers for the efficiency and environmental performance


Measuring energy consumption is an important factor in the quest to improve energy efficiency. Efficient and accurate metering is paramount to determining excess use, along with an accurate picture of where the steam is being used. The more accurate and reliable measurements that are made, the more informed decisions can be taken that affect costs and product quality. Traditionally the most common method of steam metering is the orifice plate and differential pressure transmitter technique. General areas of concern with this type of measurement are the orifice plate's susceptibility to wear introducing immediate inaccuracies, the relatively high permanent pressure losses introduced into the system by the orifice place and the small measuring range, typically 3:1.

Yokogawa's digitalYEWFLO Reduced Bore Type Vortex Flow meter features a cast stainless steel body and a concentric reducer and expander that enable stable flow rate measurements in low-flow conditions. This expands the range of measurements that can be performed, from the higher flow rates down to the lower end of the flow span, which is normally difficult for Vortex Flow meters, and ensures stable and accurate flow rate output.


Steam is still one of the most popular methods of providing an energy source to a process and its associated operations. The more accurate and reliable measurements that are made, the more informed decisions can be taken that affect costs and product quality.


The oil refining industry today faces increasingly strict regulations that dictate both the quality of its products and the diligence of its production processes. As the pioneer of the vortex flow meter technology, Yokogawa's challenge in bringing innovative flow measurement solutions to users in various process industries continues to this day.


The major methods of improved oil recovery are water flooding and steam injection. "These technologies make a tremendous contribution to recovering additional oil from old wells as well as improve primary recovery of operating oil fields."


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