Vortex flowmeters make use of a principle called the von Kármán effect. According to this principle, flow will alternately generate vortices when passing by a bluff body. A bluff body has a broad, flat front. In a vortex meter, the bluff body is a piece of material with a broad, flat front that extends vertically into the flowstream. Flow velocity is proportional to the frequency of the vortices. Flowrate is calculated by multiplying the area of the pipe times the velocity of the flow
Vortex flowmeters are well suited for measuring steam flow, and they are widely used for this purpose. Steam is, arguably, the most difficult fluid to measure. This is due to the high pressure and high temperature of steam, and because the measurement parameters vary with the type of steam. Main types of steam include wet steam, saturated steam, and superheated steam.