Development of finite-amplitude disturbances in Poiseuille flow

The process of three-dimensional distortion of previously two-dimensional disturbances was investigated in a rectangular channel. For the first time the three-dimensional structures at the breakdown station of the two-dimensional wave were studied by flow visualization. It was shown that the structures have forms identical with Λ-shaped vortices in a boundary layer of the flat plate. The spanwise spacing of the Λ-shaped vortices is quite independent of the mean-flow velocity and of the frequency of artificial disturbances.