  Recent research has shed light on the role of coherent structures in forming
layers when stably stratified turbulence is forced with horizontal shear
(Lucas, Caulfield & Kerswell, J. Fluid Mech., vol. 832, 2017, pp. 409-437).
Here we extend our previous work to investigate the effect of rigid boundaries
on the dynamics by studying stably-stratified plane Couette flow with gravity
oriented in the spanwise direction. We observe near-wall layering and
associated new mean flows in the form of large scale spanwise-flattened
streamwise rolls. The layers exhibit the expected buoyancy scaling $l_z\sim
U/N$ where $U$ is a typical horizontal velocity scale and $N$ the buoyancy
frequency. We associate the new coherent structures with a stratified
modification of the well-known large scale secondary flow in plane Couette and
find that the possibility of the transition to sustained turbulence is
controlled by the relative size of this buoyancy scale to the spanwise spacing
of the streaks. We also investigate the influence on the transition to
turbulence of the newly discovered linear instability in this system (Facchini
et. al. 2018 arXiv:1711.11312).
