Abstract

My talk will consider the propagation of ultrasound in nano/microparticle suspensions consisting of randomly distributed solid particles in a viscous liquid which is a system relevant to industrial process monitoring and to the characterisation of soft materials e.g. biological media. The embedding medium supports multiple wave modes: elastic waves (longitudinal), thermal waves (longitudinal) and shear waves (transverse); at MHz frequencies in typical liquids the wavelengths of both thermal and shear modes are much smaller than the elastic (compressional) wavelength and are both dissipative. I consider systems in which the compressional wavelength is large compared with the particle size, but with arbitrary shear wavelength. The multiple scattering effects include mode conversions for which the leading terms appear at second order in concentration. I explore the dominant contributions from multi-mode multiple scattering in such systems, based on ensemble averaged multiple scattering formulations based on multipole expansions and the T-matrix for individual scatterers.