KROHNE OPTISWIRL 4070 EN - Manual (Page 69)

TECHNICAL DATA
8
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OPTISWIRL 4070
www.krohne.com 02/2013 - 4000150606 MA OPTISWIRL4070C R07 en
Technical data
8.1 Functional principle
Vortex flowmeters are used to measure the volumetric flow of gases, vapours and liquids at
completly filled pipes.
The measuring principle is based on the Karman vortex street. The measuring tube contains a
bluff body, behind which vortex shedding occurs. The frequency ffff of the vortex shedding is
proportional to the flow rate vvvv. The nondimensional Strouhal number S
S S S describes the
relationship between vortex frequency ffff, width b bb b of bluff body and the mean flow velocity vvvv:
The vortex frequency is recorded at the sensor and evaluated at the converter.
Figure 8-1: Functional principle
= f
S . v
b
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