Acoustic solutions to the particle mixing problem in aqueous dispersions

Colloidal dispersions are found in many modern product formulation processes, and one of the problems commonly occurring in these processes is characterising the particles within these systems. The existing theories for predicting acoustic scattering in these systems do not fully account for the interactions between neighbouring particles. Most importantly they do not account for the thermal interactions in thermoacoustic scattering. In this thesis I develop an asymptotic solution in the small wave number limit to the multiple scattering problem. This is done by considering the thermoacoustic field interaction between two different sized particles close together, and applying this to a pair distribution probability function, giving an extra term in the far field scattering calculations. This provides a method of predicting attenuation in mono- and bi-disperse colloids, especially for those of higher concentrations. This theory is compared to attenuation experimental data for a number of different colloidal systems, mono- and bi-disperse of increasing concentrations, where the thermal field overlap between particles is more prominent. Comparing these experiments with the new two particle thermoacoustic scattering theory give more consistent results than previous theories for volume concentrations up to 30%. Further work, as part of a CASE studentship, on sedimentation detection in pipe flow using by monitoring the behaviour of pulses of ultrasound is also presented in this thesis.