Dynamic Acoustic Radiation Force on a Viscoelastic Spherical Shell near an Impedance Boundary
When the incident acoustic wave contains many different frequency components,the acoustic radiation force on the objects will have a dynamic component that changes with time,which is called the dynamic acoustic radiation force.Dynamic acoustic radiation has been widely used in medical imaging,parameter inversion and other relevant fields.Based on the image theory,the expression of the dynamic acoustic radiation force acting on a viscoelastic spherical shell near an impedance boundary for a dual-frequency wave is theoretically deduced.Numerical calculations for a viscoelastic lucite shell are provided as an example.The results show the splitting of the resonant peaks for the dynamic acoustic force,which produces two peaks that are separated by a dimensionless frequency shift equal to the modulation dimensionless frequency.Therefore,when the two frequencies are very close,the dynamic radiation force can be approximated as the steady radiation force.The increase of the boundary reflecting coefficient leads to the enhancement of the peak value of the dynamic acoustic radiation force.Moreover,the dynamic acoustic radiation force changes periodically along the variation of shell-boundary distance.When the spherical shell is relatively thin,the dynamic acoustic radiation force for the air-filled spherical shell is much stronger than that for the water-filled one bacause air has a much lower impedance than water.These results are expected to provide a theoretical basis for the acoustic manipulation near the boundary using the dynamic acoustic radiation force.
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