Direct numerical simulations (DNS) have been performed in order to investigate the interaction of freestream turbulence and crossflow generated instability on a swept wing. The experiments by [3] and [1] are selected as the reference cases. In those experiments the authors explore the interaction between different freestream turbulence characteristics and different roughness element characteristics. In the current study, isotropic homogenous freestream turbulence are generated following experimental parameters and then fed as the inflow boundary condition for DNS of flow over the wing. A spanwise array of roughness elements corresponding to the most unstable stationary modes are used to generate the crossflow vortices. The effects of the freestream turbulence on the crossflow instability and transition to turbulence are later studied.