Figure 5.

Interfacial waveforms with preferential directionality in a hexagonal lattice connected to a system of gyroscopic spinners. The lattice domain is divided into two regions: in the hexagonal region the spinners rotate (a,b) clockwise and (c,d) anticlockwise, while the ambient medium contains spinners which rotate in the opposite direction to those situated inside the hexagonal region. The absolute value of the spinner constant is |α| = 0.9 for all the gyroscopic spinners. At the interface, the spinners rotate in the same direction as in the exterior domain. A time-harmonic displacement, represented by the straight arrow, is applied to a node on the interface of these regions. The relative displacement amplitude fields are obtained for the applied displacement of frequency (a,c) ω = 3.8 and (b,d) ω = 4.0 (see also inset in figure 2f ). The figures illustrate that the preferential direction of the interfacial waveform can be influenced by interchanging the direction of rotation of the spinners or by changing the frequency of the external excitation. (Online version in colour.)