Computation of the acoustic radiation force using the finite-difference time-domain method

Area of Science:

• Acoustics
• Computational Physics
• Wave Phenomena

Background:

• Acoustic radiation force is crucial for manipulating micro- and nano-scale objects.
• Accurate computational methods are needed to predict these forces for various applications.
• Existing analytical methods may be limited in scope or computational efficiency.

Purpose of the Study:

• To present computational details of a 2-D grid finite-difference time-domain (FDTD) method for calculating acoustic radiation force.
• To validate the FDTD method against analytical scattering results.
• To explore the potential for acoustic trapping using optimized parameters.

Main Methods:

• Finite-difference time-domain (FDTD) simulation on a 2-D grid.
• Propagation of stress and velocity fields.
• Determination of energy flow with and without the object.
• Comparison with analytical scattering solutions.

Main Results:

• FDTD predictions for axial and radial acoustic radiation forces show excellent agreement with analytical results.
• Demonstrated possibility of radially trapping a steel cylinder by optimizing Gaussian source width and operation frequency.
• The method is suitable for objects with sizes comparable to or smaller than the acoustic wavelength.

Conclusions:

• The presented 2-D FDTD method is a reliable tool for calculating acoustic radiation forces.
• The findings suggest practical applications in acoustic trapping and manipulation.
• The algorithm's extensibility to 3-D and inclusion of torque computation offer a flexible computational engine for diverse acoustic problems.