Vortex shedder sing-around flow meter

Abstract: The need to measure flow rates in fluids is large in the world today. Many
are the applications where a more or less accurate measurement is needed,
e.g. gasoline pipe, district heating, medical flows and flows in the
manufacturing industry. One way to measure flow velocities that is commonly
used is with vortex shedding flow meters. These flow meters detect the
vortices behind a bluff body in a flow in different ways, one way is by
transit time ultrasonics. Since, normally, the sing around-ultrasonic is a
more accurate way to measure flow velocity the theory behind this thesis is
that a vortex shedder flow meter with sing-around ultrasonics should be more
accurate than the ones with transit-time. A vortex flow meter is modeled with
FEMLAB to give simulated data for the signal processing, and then the data is
processed in MATLAB. The zero-crossing algorithm and the fast Fourier
transform are applied to find the vortex frequency. In this stage it seems
as if the sampling frequency is too small to detect the vortex frequencies.
The final step is to make a vortex flow meter to confirm the theoretical
model. The bluff body is built around ultrasonic transducers from
D-flow technology AB. The flow meter is inserted to the water laboratory at
Luleå University of Technology and measurements are done that is later
evaluated and compared to the simulation results.
In the real model the vortex frequency is discovered for the lower
velocities, but the signal processing used in this thesis is not sufficient
to give accurate frequencies for the higher velocities. Two big conclusions
are made, that the theoretical model is not good enough and that the vortex
frequency is present in the measured signal but could not be found with the
algorithms at hand.