Design and optimization of a sub-wavelength unidirectional transmission structure for underwater acoustic waves with multiple incident directions
LU Wei1, ZHANG Sai1,2*, XU Baiqiang1, ZHANG Yu3, CAO Wenwu4
(1 Faculty of Civil Engineering and Mechanics, Jiangsu University, Zhenjiang 212013, Jiangsu, China;2 Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, Heilongjiang, China;3 Key Laboratory of Underwater Acoustic Communication and Marine Information Technologyof the Ministry of Education, Xiamen University, Xiamen 361005, Fujian, China;4 Materials Research Institute, Pennsylvania State University, Pennsylvania State 16802, United States of America)
Abstract:
Using the transfer matrix method, the band structure of the infinite solid-fluid superlattice and the transmission spectrum of the finite cascaded superlattice are calculated and analyzed based on the transfer matrix of the unit cell of superlattice. On this basis, the underwater sub-wavelength wide-angle acoustic unidirectional transmission structure is constructed by coupling 1D periodic rectangular acoustic gratings with the cascaded superlattice, and the mechanism of wide-angle unidirectional transmission is revealed. The finite element simulation results show that the structure can realize the unidirectional transmission effect for incident acoustic waves of about 20 degrees, and has the characteristics of broadband and high rectification ratio. Finally, by rotating the unit cell of acoustic gratings, the forward conductivity of the structure is effectively improved. This research breaks through the limitation of “wavelength-size” in the design of unidirectional acoustic transmission based on phononic crystals, and is helpful for the development of underwater acoustic rectifiers towards miniaturization and integration.
KeyWords:
wide-angle; acoustic unidirectional transmission; sub-wavelength; superlattice
