Unsteady Boundary Layers on a Flat Plate Disturbed by Periodic Wakes: Part II—Measurements of Unsteady Boundary Layers and Discussion

As the second part of the study, detailed hot-wire anemometry measurements of wake-affected boundary layers on the flat plate are made. These measurements are organized in order, first, to check the standpoint of the modeling of the wake-induced transition proposed in Part I, and second, to observe wake–boundary layer interaction in detail from a viewpoint of direct and indirect effect of the wake passage upon turbulent spot generation within the boundary layer, as described by Walker (1993). The validity of the presumed state of the wake-affected boundary layer in the distance–time domain, which constitutes the basis of the transition model, is confirmed to great extent. However, it is also found that the criterion for the onset of the wake-induced transition adopted in Part I should be reconsidered. Some successful attempts are therefore made to specify the transition onset.