Turbulent spot evolution in spatially invariant boundary layers

A demanding task, for successful fluid dynamic design in many industrial applications, is being able to predict the transition to turbulence location in boundary layer flows. The focus of the present experimental study is on the late stage of transition scenarios where turbulent spots are borne. We report on a natural stabilizing mechanism on the growth rate of turbulent spots, which takes place in a specific bypass transition scenario, and show that there is a palpable history effect of the origin of the turbulent spot on the streamwise evolution. Furthermore, experimental evidence on Reynolds number effects on the spot evolution in boundary layers is put forward. This has been made possible by setting up an idealized experiment, which usually only is considered as a schoolbook example.