Amplitude-modulated acoustic radiation force experienced by elastic and viscoelastic spherical shells in progressive waves

摘要

The dynamic acoustic radiation force resulting from a dual-frequency beam incident on spherical shells immersed in an inviscid fluid is examined theoretically in relation to their thickness and the contents of their interior hollow regions. The theory is modified to include a hysteresis type of absorption inside the shells' material. The results of numerical calculations are presented for stainless steel and absorbing lucite (PolyMethyMethacrylAte) shells with the hollow region filled with water or air. Significant differences occur when the interior fluid inside the hollow region is changed from water to air. It is shown that the dynamic radiation force function Y-d deviates from the static radiation force function Y-p when the modulation size parameter delta x = vertical bar x(2) - x(1)vertical bar (x(1) = k(1)a, x(2) = k(2)a, k(1) and k(2) are the wave vectors of the incident ultrasound waves, and a is the outer radius of the shell) starts to exceed the width of the resonance peaks in the Y-p curves. (c) 2006 Elsevier B.V. All rights reserved.