Contribution of the Acoustic Wake Effect to the attenuation of sound in dilute suspensions of rigid particles

This work deals with the attenuation of sound in dilute suspensions of rigid particles when the hydrodynamic mechanism of the acoustic-wake effect is considered. The study extends a previous model by considering asymmetric flow-field conditions around the particles, caused by other neighbor particles along the direction of propagation of the acoustic field. The attenuation coefficient is derived from the force equation for a spherical particle in an incompressible fluid that is oscillating at low frequencies and amplitudes within the range of Reynolds numbers of 0.1 < Re < 1. It acquires higher values than those obtained for the Stokes regime (Re << 1), increasing up to about 8% at Reynolds numbers close to the unity. In the study we found the particle size as a significant parameter on the sound attenuation, together with concentration of particles.