Traveling instabilities on a crossflow instability dominant boundary layer

Full turbulent transition is created in three-dimensional (3D) boundary layer on a swept back flat plate with a displacement body system in a wind tunnel. In the case of general crossflow dominant 3D boundary layer transitions, it is known that after crossflow vortices appeared, crossflow-traveling instability appears. However, it is not clear how the crossflow traveling instability starts to appear and what is the roll of it in the transition process. The flow field is measured in detail using hot-wire anemometry and the smoke visualization technique. Visualization of the crossflow traveling instability f₁ is succeeded using high-speed camera. Periodical rolling up vortex motion generated propagating wave with the frequency of f ₁. From the results, it can be concluded that crossflow traveling instability f₁ is the inflectional point instability existing in spanwise velocity profile. Such unstable condition is originally generated by the streamwise vortex motion.