Separation ahead of steps on swept wings

The paper is concerned with the problem of predicting the flow separation line on a swept wing ahead of a forward facing step under boundary layer transition conditions. Two-dimensional strip-type analysis predicts a curved separation locus halfway between the leading edge and the step for laminar separation, and a straight separation line close to the step for turbulent separation. If there are substantial regions of both laminar and turbulent flow on the wing surface, and the proposed strip analysis is correct, then on the inboard portion of the wing separation will occur along the curved turbulent line, and on the outboard portion separation will occur along the straight laminar line. In-between, the separation line will follow an 's'-shaped curve. This qualitative result has been confirmed in oil flow and schlieren tests on half-wings with mounted steps.