Figure 8.

Comparison of theoretical predictions and the FEM simulation with respect to different connection tube lengths L_d between the two periodic parts (solid lines represent the theoretical predictions, and dashed lines represent the FEM simulation results): (a) n = m = 5, $L_d=3\times 0.5{\lambda }_0$; (b) n = m = 5, $L_d=3.3\times 0.5{\lambda }_0$; (c) n = m = 5, $L_d=4\times 0.5{\lambda }_0$; (d) n = m = 5, $L_d=10\times 0.5{\lambda }_0$.