Development of secondary crossflow instability near breakdown into turbulence

Throughout the years the transition process from laminar to turbulent flow has been studied in numerous experimental and numerical studies. Since for laminar flow the skin friction is lower compared to turbulent flow, the subject currently receives increased attention in the quest to design a laminar flow aeroplane. In the current study the transition process on a swept surface is studied with high resolution hot-wire scans. Up to now most studies focused on the development of the primary instability and the first growth stages of the secondary instability. Here the focus is on the structure of the secondary crossflow instability from its origin to breakdown. It has been found that, in the early growth stages, the characteristics of the structure agree well with previous studies. Close to breakdown of the flow the main structure divides up into smaller structures which are thought to be due to a developing turbulent wedge.