The two-dimensional incompressible separated flow downstream of rearward-facing step is investigated analytically. An emphasis is given to the prediction of flow characteristics in the close region of reattachment and the redeveloping boundary layer downstream of reattachment. The streamwise static wall pressure distribution up- and downstream of reattachment point is predicted based upon distribution of potential velocity and displacement thickness confirming the similarity and verified by experimental data. The reattachment length is determined analytically assuming that the flow after reattachment is a kind of wake. And solving the stagnation point flow with the incidence angle to the wall, the dividing streamline reattachment angle of turbulent flow is determined amounting about 20 degree which is verified by measured data. The redeveloping velocity profile downstream of reattachment from its reattachment velocity profile which is similar to that of laminar separation, slowly approaches to the turbulent boundary layer at far downstream. Such redeveloping velocity profile is well presented by modifying Coles' wall and wake law. The confirmation of this modification is checked with experimental data of redeveloping boundary layer downstream of turbulent reattaching flow. The velocity profile close to reattachment is given by 2nd degree of polynomials for y but downstream of reattachment the velocity profile proposed by equation (11) and (12) appears to be proper. And the skin friction is predicted favorably downstream of reattachment. Numerical computation for the two-dimensional laminar channel flow with 1:2 expansion shows the general behaviors of the step-induced separation flow; streamlines, vorticity distribution, pressure distribution and velocity profiles.
