Acoustic trapping of particle in the near field of a resonant periodically structured stiff plate

We report the numerical analysis of the acoustic radiation forces exerted on a cylindrical brass particle near the surface of periodically structured brass plate. The radiation force is calculated by using the time-averaged momentum-flux tensor obtained with the finite-difference time-domain method. The result indicates that when the resonance of the structured plate occurs, this configuration has an interesting trapping effect, which essentially arises from the gradient force induced by vortex velocity field near the surface of structured plate. The radiation force is found to be larger than the corresponding gravity with source irradiance 22.4e4Pa at resonance frequency for the radius of brass cylinder around 0.1mm-1.6mm with a distance 0.11mm from the plate. This artificial structure may be of interest for acoustic manipulation and sorting in various complex mechanical systems.