  Transonic buffet is an instability characterized by shock-oscillations and
separated boundary-layers. High-fidelity simulations have typically been
limited to narrow domains to be computationally feasible, overly constraining
the flow and introducing modelling errors. Depending on the boundary-layer
state upstream of the interaction, different buffet features are observed.
High-fidelity simulations were performed on the periodic NASA-CRM wing at
moderate Reynolds number to assess sensitivity of the two-dimensional transonic
buffet to boundary-layer state and domain width. Simulations were
cross-validated against RANS/URANS and global stability analysis and excellent
agreement was found near the onset. By varying the boundary-layer tripping
amplitude, laminar, transitional, and turbulent buffet interactions were
obtained. All cases consisted of a single shock and low-frequency oscillations
$(St \approx 0.07)$. The transitional interaction also exhibited reduced shock
movement, a $15\%$ increase in $\overline{C_L}$, and energy content at higher
frequencies $(St \approx 1.3)$. Span-wise domain studies showed sensitivity at
the shock location and near the trailing edge. We conclude that the span-width
must be greater than the trailing-edge boundary-layer thickness to obtain
span-independent solutions. For largely separated cases, the sensitivity to
span-width increased and variations across the span were observed. This was
found to be associated to a loss of two-dimensionality of the flow.
