Publications

Transducer finite aperture effects in sound transmission near leaky Lamb modes in elastic plates at normal incidence
; Lohne, Kjetil Daae; Lunde, Per; Vestrheim, Magne
The interaction of ultrasonic waves with fluidembedded viscoelastic plates, pipes, and shells, have been subject to extensive theoretical and experimental studies over several decades. In normalincidence throughtransmission measurements of a waterembedded solid plate using ultrasonic piezoelectric transducer sound fields, significant deviations from plane wave theory have recently been observed.

Beam transmission of waterembedded steel plate at normal incidence. Diffraction effects in the S1 to A3 region
; Lohne, Kjetil Daae; Lunde, Per; Vestrheim, Magne;
Measurement of the sound transmission through a fluid?embedded viscoelastic plate at normal incidence can show significant deviations to the plane?wave theory, experiencing both frequency shift and signal level variation in relation to the plane?wave theory.

Transducer beam diffraction effects in sound transmission near leaky Lamb modes in elastic plates at normal incidence
; Lohne, Kjetil Daae; Lunde, Per; Vestrheim, Magne;
The plane wave theory of fluidembedded viscoelastic plates is often used in waveguide applications, and to estimate wall thickness and sound velocities in plates and pipe walls. In normalincidence throughtransmission measurements, downward frequency shift, signal amplification, and distorted beam patterns, as compared to planewave theory, have been observed for resonant peaks in frequency bands near certain Lamb modes.

Normal incident ultrasonic beam transmission through a waterimmersed plate using a piezoelectric transducer. Finite element modelling, angular spectrum method and measurement
; Lohne, Kjetil Daae; Lunde, Per; Vestrheim, Magne;
Accurate time of flight (TOF) measurements in noninvasive ultrasonic applications for media contained by plane walls or pipes, demand a precise understanding and control of the generation, transmission and reception of sound beams through solid layers (plane walls or pipes) and the surrounding fluids.

Ultrasonic beam transmission through a waterimmersed plate at oblique incidence using a piezoelectric source transducer. Finite element  angular spectrum modeling and measurements
; Lohne, Kjetil Daae; Lunde, Per; Vestrheim, Magne;
A measurement system consisting of a piezoelectric transducer and a waterimmersed steel plate is studied.

Finite element analysis of acoustic beam interactions with plate at normal incidence. Comparison with a 3D angular spectrum method and measurements
; Lohne, Kjetil Daae; Lunde, Per; Vestrheim, Magne;
The use of the finite element method (FEM) for studying the interactions of an acoustic beam with an elastic steel plate is discussed, in comparison with a 3D angular spectrum method (ASM) and measurements.

Measurements and 3D simulation of ultrasonic directive beam transmission through a waterimmersed steel plate
Lohne, Kjetil Daae; Lunde, Per; Vestrheim, Magne;
A 3D fullwave angular spectrum simulation model for reflection and transmission of ultrasonic directive circular piston sound fields, from and through a fluidimmersed isotropic solid plate has been implemented.

Ultrasonic signal transmission in plates – Study of a steel plate immersed in water
Lohne, Kjetil Daae; Lunde, Per; Magne Vestrheim
In the present work, a theory for the description of the propagation of plane ultrasonic waves through a fluid loaded plate is described. The theory assumes different fluid loading at the two interfaces, but the special case with the same fluid loading is also treated.

HANDBOOK OF UNCERTAINTY CALCULATIONS  Fiscal Orifice Gas and Turbine Oil Metering Stations
Eivind Olav Dahl; Frøysa, KjellEivind; Lunde, Per;
Norwegian regulations relating to measurement of petroleum for fiscal purposes and for calculation of CO2 tax require that the overall measurement uncertainty be documented to be within defined limits. However, the different methods used gave different results. A consistent, standardised method of uncertainty estimation was required, so that different measurement systems could be directly compared.

HANDBOOK OF UNCERTAINTY CALCULATIONS  Ultrasonic fiscal gas metering stations
Lunde, Per; Frøysa, KjellEivind;
Norwegian regulations relating to fiscal measurement of oil and gas require that the overall measurement uncertainty is documented to be within defined limits. However, the different methods used have given different results. A consistent and standardised method of uncertainty evaluation has been required, so that different measurement systems could be directly and reliably compared.