Acoustic Interaction Forces and Torques Acting on Suspended Spheres in an Ideal Fluid

J. Henrique Lopes, Mahdi Azarpeyvand, Glauber T Silva

Research output: Contribution to journalArticle (Academic Journal)peer-review

36 Citations (Scopus)
358 Downloads (Pure)


In this paper, the acoustic interaction forces and torques exerted by an arbitrary time-harmonic wave on a set of N objects suspended in an inviscid fluid are theoretically analyzed. We utilize the partial-wave expansion method with translational addition theorem and reexpansion of multipole series to solve the related multiple scattering problem. We show that the acoustic interaction force and torque can be obtained using the farfield radiation force and torque formulas. To exemplify the method, we calculate the interaction forces exerted by an external traveling and standing plane wave on an arrangement of two and three olive-oil droplets in water. The droplets’ radii are comparable to the wavelength (i.e. Mie scattering regime). The results show that the acoustic interaction forces present an oscillatory spatial distribution which follows the pattern formed by interference between the external and re-scattered waves. In addition, acoustic interaction torques arise on the absorbing droplets whenever a nonsymmetric wavefront is formed by the external and re-scattered waves interference.
Original languageEnglish
Number of pages12
JournalIEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Issue number1
Early online date27 Oct 2015
Publication statusPublished - 1 Jan 2016


  • Acoustic radiation force
  • Acoustic radiation torque
  • Multiple scattering


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