Remi
A. Kippersunda,b,*, Per Lundeb,a and Kjell-Eivind
Frøysaa
a Christian Michelsen Research AS (CMR), P.O. Box 6031
Postterminalen, N-5892 Bergen, Norway
b University of Bergen, Department of Physics and Technology, P.O.
Box 7803, N-5020 Bergen, Norway
High-viscous fluid flow is becoming
increasingly important in petroleum industry, in connection with flow
measurement and flow assurance. Fluids undergoing rheological changes are
important for process control. Density,
adiabatic bulk modulus and viscosity constitute important liquid properties,
and quantification of such may provide important information about the status
and progress of the industrial process.
Non-invasive methods for fluid characterization are of interest in this
context, for operational and cost-saving reasons and to avoid interference with
the industrial process.
The velocity and attenuation of elastic
waves transmitted in fluid loaded solid waveguides are affected by the sound
velocity, density and viscosity of the surrounding fluid. An elastic wave travelling in a solid causes
deformation of the solid-fluid interface, inducing fluid motion. The coupling mechanism between the motion in
the solid and the fluid depends on the geometry of the waveguide and the type
of elastic wave employed. Torsional and longitudinal guided waves in pipes
provide different information about the interior fluid in this context.
In the present work, attenuation of
ultrasonic guided elastic waves in fluid-filled pipes is investigated
theoretically and experimentally.
Torsional waves in the pipe wall are excited and detected using
externally mounted circumferential piezoelectric transducer arrays. The attenuation of multi-modal waveguide
signals propagating in the pipe wall is used to extract the fluid density •
viscosity product, employing theoretical models for ultrasonic wave propagation
in plane and circumferentially layered elastic-fluid media. A multitude of
modes are excited simultaneously to employ a wide frequency band, and
time-reversal techniques are investigated to improve sensitivity. Measurements and simulation results are
presented for fluids of different fluid viscosities.