Unsteady structures of a separated three-dimensional turbulent boundary layer

A description is given of the unsteady flow behaviors at a plane of symmetry in a confined jet impinging on a back wall including separation of three-dimensional turbulent boundary layers. Flow direction intermittency by a thermal tuft and wall pressure fluctuations are obtained in the separated region. A combined simultaneous flow visualization with the thermal tuft is also made. Two kinds of vortices are found to occur. The primary separation vortex just ahead of the back wall has a low frequency in the wall pressure fluctuation and a long period of the flow intermittency. The secondary vortex near the separation point with smaller pressure fluctuations has more periodic feature than the primary one. Little propagation of the unsteady disturbance due to vortex motions towards the upstream direction is observed.