Pulse transmission and acoustic non-reciprocity in a granular channel with symmetry-breaking clearances
Pulse transmission and acoustic non-reciprocity in a granular channel with symmetry-breaking clearances
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DOI：
10.1007/s10035-019-0982-7
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发表时间：
2019-12
期刊：
影响因子：
2.4
通讯作者：
Qifan Zhang;Wei Li;J. Lambros;L. Bergman;A. Vakakis
中科院分区：
文献类型：
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作者：
Qifan Zhang;Wei Li;J. Lambros;L. Bergman;A. Vakakis
由离散球形颗粒的有序阵列组成的颗粒介质由于其高度非线性和不连续的动力学和声学特性而引起了相当大的关注。在这项工作中，我们数值研究了非线性脉冲在二维（2D）颗粒通道中的传播，该通道由一个主均匀晶格和几对侧颗粒组成。根据脉冲在主晶格中的传输方向，一系列周期性的对称性破坏间隙改变了这个二维颗粒网络的拓扑结构。单个颗粒的旋转动力学，以及由于颗粒之间（及其边界）和固有材料阻尼之间的摩擦而产生的耗散效应，被证明在颗粒通道的声学中起着重要作用。这是通过比较这项工作的理论预测和先前报道的同一系统的实验测量来证明的。此外，该系统的强非线性与间隙引入的拓扑不对称性协同作用被动地破坏了声学互易性。为此，对二维颗粒通道中的脉冲传输进行了详细的研究，结果表明，通过简单地改变脉冲传输方向，可以将非线性声学从涅斯捷连科孤立脉冲切换到强衰减传播脉冲。在后一种情况下，能量从主传播脉冲连续不可逆地传递到侧颗粒，而侧颗粒本质上起着非线性能量吸收器的作用。这项工作强调了（即使是很小的）几何缺陷（不对称）可能对二维颗粒介质的声学起重要作用。
Granular media composed of ordered arrays of discrete spherical granules have attracted considerable attention due to their highly nonlinear and discontinuous dynamics and acoustics that enable passively adaptive and tailorable properties. In this work we numerically study nonlinear pulse propagation in a two-dimensional (2D) granular channel composed of a main homogeneous lattice with several pairs of side granules. Depending on the direction of pulse transmission in the main lattice, a periodic series of symmetry-breaking clearances alter the topology of this 2D granular network. The rotational dynamics of the individual granules, as well as dissipative effects due to friction between granules (and their boundaries) and inherent material damping, are proven to play a significant role in the acoustics of the granular channel. This is demonstrated by comparing the theoretical predictions of this work to experimental measurements of the same system reported earlier. Moreover, the strong nonlinearity of this system in synergy with the topological asymmetry introduced by the clearances passively breaks acoustic reciprocity. To this end, a detailed study of pulse transmission in the 2D granular channel is performed, and it is shown that by simply changing the direction of pulse transmission it is possible to switch the nonlinear acoustics from Nesterenko solitary pulses to strongly decaying propagating pulses. In the latter case there is continuous and irreversible transfer of energy from the main propagating pulse to the side granules, which act, in essence, as nonlinear energy absorbers. This work highlights the important role that (even small) geometric imperfections (asymmetries) may play on the acoustics of 2D granular media.