Since the flow over the thick airfoil is characterized by the rapid velocity decrease toward the tailing edge, flow separates inevitably from the rear surface of the wing. To prevent or reduce the extent of flow separation, vortex generators are attached. The main function of the vortex generators is the production of vortices trailing downstream, enhancing mixing between the external flow and internal flow of the boundary layer. Alleviation of flow separation is characterized by varying the location and the scale of the vortex generators. It is shown qualitatively that there is a remarkable effects of the vortex generators through the numerical calculation of separation line, which is affected by them. That is, when the vortex generators are installed, the flow over the airfoil is fully three-dimensional and thus the separation line is changed from straight line to two-dimensional curve on the airfoil surface. This two-dimensional separation line is changed according to the location and scale of the vortex generators.
