investigated interactions between multiple bands in a large computational domain ($500h\times 2h\times 250h$ in the streamwise, wall normal and spanwise directions, respectively). The large domain with periodic boundary conditions allowed them to observe the development of and the interactions between multiple bands for very long times, which were $\mathcal{O}(10^5)$ convective time units and very much out of reach of current laboratory experiments. They concluded that at $Re\gtrsim 976$ (higher than 830 as proposed by @Sano2016), directed percolation (DP) model can be used to model the interactions between bands and the resulting flow pattern. Before the onset of DP, turbulent bands can still be sustained. [[They observed longitudinal interaction between parallel bands and collision between bands with opposite orientations, and that turbulent bands can only form parallel pattern instead of two-sided pattern as they do at higher Reynolds numbers. However, more quantitative studies on the interactions between turbulent bands in this flow regime are needed to elucidate the transition scenario at low Reynolds numbers.]{}]{}

Considering the fact that turbulent bands can take opposite orientations (angles about the streamwise direction), it is necessary to generate bands with desired positions and orientations in order to study all possible types of interactions between bands. 