
CLA-VAL e-FlowMeter
Vortex Flow Meter
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Karman Vortex Street
The e-FlowMeter is a vortex shedding insertion flow
meter, based on the phenomenon of generating an
alternating series of vortices called «Karman vortex
street».
When the fluid encounters an obstacle placed in the
axis of fluid flow, it divides and creates small vortices
alternating on either side downstream of the obstacle.
The frequency of vortex shedding, or generation of
vortices is directly proportional to fluid velocity. These
detached vortices generate variable pressure zones
that are detected in the form of short bursts of
pressure, using a measuring sensor placed
downstream of the obstacle.
Frequency measurement
The frequency of pressure surges or generation of vortices is
counted using a piezoelectric crystal encapsulated in the
sensor head. The latter is connected by 2 wires to the circuit
board for signal processing.
Measurement cylinder orientation
Upon insertion of e-FlowMeter in the valve, the measurement
cylinder is oriented parallel to the direction of flow. After
inserting the CLA-VAL tool which allows 90 degree rotation of
the measurement cylinder, it is locked in position by the
piezoelectric sensor insert. This unique 90 degree swivel
mechanism makes it possible to increase the length of the
measurement cylinder up to 40 mm allowing stabilization of
the fluid. This unique design allows it to be inserted into a
valve body tapping of ½".
Signal processing and output information
Existing Vortex flow meters operate in turbulent steady
flow defined by a Reynolds number exceeding 5’000.
This flow regime establishes stable and easily
detectable «Karman vortex street» using
unsophisticated electronics. Velocities are detected, in
general, above 0.5 m/s.
Through the innovative electronic card developed by
CLA-VAL, e-FlowMeter can measure flow from a
velocity of 0.1 m/s to obtain an accurate signal. This is
then converted to 4-20 mA, pulse or digital pulse to suit
the desired application.
Bluff body Piezoelectric
sensor The path of the
Karman Vortex street
Printed Circuit Board
Piezoelectric
sensor
Measurement
cylinder
Insert
Bluff body
Flow direction