《InTech-Propagation_of_ultrasonic_waves_in_viscous_fluids》.pdf

15 Propagation of Ultrasonic Waves in Viscous Fluids Oudina Assia and Djelouah Hakim Facutly of Physics, University of Sciences and Technology Houari Boumedienne, P.O. 32, El Alia, Bab Ezzouar, Algiers, Algeria 1. Introduction Viscosity is a property of fluids which can have a great importance in many fields of science and industry. It can be measured by conventional viscometers or by ultrasonic methods (Hertz Al, 1991). Ultrasonic methods are based either on the determination of the characteristics of propagation (velocity or attenuation) or by the measurement of reflection coefficient (Hertz Al, 1991) (Malcom J.W Povey, 1997). In the ultrasound based experimental devices, the measurements of the propagation velocity and the attenuation during the propagation allow to determine the physical properties of the medium (He Zheng, 2001). When an ultrasonic pulse is propagating into a viscous fluid, the pulse waveforms change because of the attenuation and the dispersion of the propagation medium. After its travelling through a medium, the transmitted is not a simply delayed and attenuated waveform copy of the pulse injected at the input. A modelling of the phenomenon of propagation is necessary for an adequate interpretation of the pulse waveforms. During the 20 to 30 last years, a special attention has been devoted t