Generation of acoustical Bessel-like collimated beams using ring-excited flat plate structure transducers

This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate, which is excited by a longitudinally vibrating transducer in a ring excitation manner. The factors affecting the generation of Bessel-like collimated beams are investigated by theoretical analysis, numerical simulation and experimental methods. The results indicate that Bessel-like wave can be generated by a thin circular plate with fixed boundaries. The third-order mode of the circular plate can be modified to generate a collimated beam with suppressing side lobes when it is excited in a ring excitation manner and the excitation position lies between the first two nodal circles of the plate. As the excitation radius increases, the main lobe width of the resulting Bessel-like collimated beam decreases, the extent of the focusing region increases, and the amplitude of the side lobes initially increases and then decreases. Based on the simulation results, a prototype Bessel-like collimated beam generation system is made and measured experimentally. The experimental results are in good agreement with the numerical results. The Bessel-like collimated beam can be generated by the proposed system, which has potential application in the fields of long-range detection, imaging of highly attenuated materials, and airflow acceleration.