The present article analyses the turbulent flow around a supercritical airfoil at high Reynolds number and in the transonic regime, involving shock-wave/boundary-layer interaction (SWBLI) and buffet, by means of numerical simulation and turbulence modelling. Emphasis is put on the transition position influence on the SWBLI and optimisation of this position in order to provide a maximum lift/drag ratio. A non-classical optimisation approach based on Kriging method, coupled with the URANS modelling, has been applied on steady and unsteady flow regimes. Therefore, the present study contributes to the so-called 'laminar-wing design' with the aim of reducing the drag coefficient by providing an optimum laminar region upstream of the SWBLI.