The Research Of Manipulating Th E Propagations Of Acoustic Waves By Rectangular Groove And Cross Structures

Acoustic metamaterials have attracted widespread attention in the field of acoustics over the past decades.Since the metamaterial has the property that the natural material does not have,the structure is realized by the man-made,and many special phenomena are realized.In this thesis,the regulation of sound waves is realized by two kinds of metamaterials,and the propagation of sound waves in the structure is discussed through theoretical derivation and numerical simulation.The first chapter reviews the research background and development history of acoustic metamaterial,some important results,and the content arrangement of this paper.In the second chapter,a new rectangular groove structure is proposed,we propose a structure where the groove period is different from the grating period,and collimates sound waves with very small side lobes.The relationship between the radiation direction of the surface acoustic wave and the frequency under different groove depths is studied,and the incident angle of the rectangular acoustic grating periodic control plane sound wave is also realized.The third chapter is a metasurface structure composed of four rectangular grooved structures and a rectangular channel.By adjusting the depth of the rectangular groove structure and arranging a plurality of the structural elements in the horizontal direction,the phase gradient regulation of the metasurface structure can be realized,thereby realizing the regulation of the wavefront of the transmitted acoustic wave.Based on generalized Snell’s law,this metasurface structure is used to realize anomalous refraction,acoustic focusing,non-diffractive Bessel beam,and wavefront modulation of cylindrical waves into plane waves.The fourth chapter is a metasurface structure composed of a periodic arrangement of cross structures.By adjusting the length of the cross structure and arranging a plurality of the structural units in the horizontal direction,the phase adjustment of the metasurface structure can be realized,and the phase regulation of the ultra-wideband cross structure is realized.In addition,after periodic arrays of cross structures arranged in a single layer period,it is found that focusing on the transmission phase distribution can realize the phase distribution of 0-2π.In the fifth chapter,we review the content of the full text and make an appropriate outlook for the follow-up work,hoping to achieve more in-depth research.