  Transonic buffet refers to the self-sustained periodic motion of shock waves
observed in transonic flows over wings and limits the flight envelope of
aircraft. Based on the boundary layer characteristics at the shock foot, buffet
has been classified as laminar or turbulent and the mechanisms underlying the
two have been proposed to be different (Dandois et al., 2018, J. Fluid Mech.,
vol. 18, pp. 156-178). The effect of various flow parameters (freestream Mach
and Reynolds numbers and sweep and incidence angles) on laminar transonic
buffet on an infinite wing (Dassault Aviation's supercritical V2C aerofoil) is
reported here by performing Large-Eddy Simulations (LES) for a wide range of
parameters. A spectral proper orthogonal decomposition identified the presence
of a low-frequency mode associated with buffet and high-frequency wake modes
related to vortex shedding. A flow reconstruction based only on the former
shows periodic boundary-layer separation and reattachment accompanying shock
wave motion. A modal reconstruction based only on the wake mode suggests that
the separation bubble breathing phenomenon reported by Dandois et al. is due to
this mode. Together, these results indicate that the physical mechanisms
governing laminar and turbulent buffet are the same. Buffet was also simulated
at zero incidence. Shock waves appear on both aerofoil surfaces and oscillate
out of phase with each other indicating the occurrence of a Type I buffet
(Giannelis et al., 2018, Aerosp. Sci. Technol., vol. 18, pp. 89-101) on a
supercritical aerofoil. These results suggest that the mechanisms underlying
different buffet types are the same.
