Simulation-based response analysis of porous and non-porous infrasonic arrays

Abstract

A numerical simulation for porous and non-porous infrasonic arrays has been developed to aid in the analysis of the response of these systems. For design flexibility, the simulation makes use of differential T-elements, which may be used as building blocks to assemble pipes and junctions of various shapes and sizes. The simulation adds to the capabilities of a previously developed model [Alcoverro and Le Pichon, J. Acoust. Soc. Am. 117, 1717 (2005)], by including variable tube porosity, a calculation of wall-losses based on a thermo-viscous function, a calculation of the change in response as the azimuth and elevation of the incoming wave are varied, and a calculation of the wave shape as it propagates through the array in the time domain. [Research funded by the Applied Research Laboratory Educational and Foundational Fund.]

T -matrix evaluation of three-dimensional acoustic radiation forces on nonspherical objects in Bessel beams with arbitrary order and location

“…Acoustic tweezers, an appropriate counterpart to optical tweezers 1,2 , could be used for levitation 3,4 , pulling forces [5][6][7][8] , and lateral trapping 9,10 . Compared with optic tweezers, acoustic tweezers tend to exert a larger force over larger length scales with the same intensity since the radiation force is proportional to the ratio of the intensity to the velocity in the medium 11,12 .…”

“…Negative radiation force single-beam device could pull the target towards the source, which is of interest in both acoustical [5][6][7][8] and optical fields 16 . The physical mechanism is due to the asymmetric scattering of the incident fields on the target such that the scattering into the forward direction (red arrows in Fig.1 (a)) is relatively stronger than the scattering into the backward direction (blue arrows in Fig.1 (a)) [5][6][7]16,17 . This is understood by the conservation of momentum and the Newton's third law regarding reaction force.…”

“…This is understood by the conservation of momentum and the Newton's third law regarding reaction force. 17,18 Beams having the local properties of acoustic Bessel beams are candidates for single-beam tweezers which have been examined in theoretical [5][6][7]19 and experimental approaches 10,20 . The ordinary Bessel beam (OBB) possesses the axial maximum and azimuthal symmetry, while the helicoidal Bessel beams (HBB) have an axial null and 3 azimuthal phase gradient.…”

Analog model for thermoviscous propagation in a cylindrical tube

“…(10)] and the analog circuit approximation [Eq. (9)] divided by the exact value. With 24 branches, the approximation is accurate within 2% for frequencies below 10 kHz and to 0.1% below 2.5 kHz.…”

“…Acoustic propagation modeling in cylindrical tubes continues to be an active area of investigation, for example for the study of absorbing materials, 6 for propagation in small tubes such as in hearing aids, 7,8 for propagation at very low frequencies, 9,10 for thermoacoustics, 11 and for modeling of wind musical instruments. 5 In many of these applications, the systems are sufficiently linear that a frequency domain analysis provides the required accuracy.…”