A Priori Modeling of the Acoustic Boundary Layer Effect on the Heat Source in Ultrasound

Abstract

A reduced-order model is proposed to provide effective boundary conditions accounting for a vortical fluid velocity confined in an Acoustic Boundary Layer (ABL) around a linear elastic solid object subjected to an ultrasound wave. It is validated by a priori tests of two-dimensional acoustic scatterings by a cylinder with material properties of water and bone. The viscous dissipation resulting in a heating predicted by the proposed model is in excellent agreement with that of the full model, in which the P- and S-waves in fluid are faithfully captured. The frictional heat source per area in the ABL is confirmed to be O(104) higher than that in the bulk, suggesting the significance of the ABL effect in estimating overheating risks in HIFU (High Intensity Focused Ultrasound) therapy.

Keywords

• heat source
• acoustic boundary layer
• ultrasound wave