Transition initiated by a wave packet in a cone boundary layer at Mach 3.5 has been investigated using linear stability theory and direct numerical simulations. Disturbances have been introduced into the boundary layer by pulsing the wall-normal velocity through a hole on the cone surface. The present study can be divided into three parts. In the first part, the linear development of a wave packet is studied in detail. The second part focuses on the identification of possible, asymmetric resonance triads for the most dominant oblique instability waves of the wave packet. New triads have been found that have not yet been reported for a supersonic boundary layer. These triads might explain some major findings in the third part of the present work, which focuses on the weakly nonlinear development of a wave packet that was generated by a large-amplitude pulse. The initial disturbance development of this wave packet remains still linear, while farther downstream nonlinear wave interactions alter the shape and the disturbance spectrum of the packet. The results of the third part suggest that oblique breakdown might be the strongest nonlinear transition mechanism for a supersonic boundary layer.
ASJC Scopus subject areas
- Aerospace Engineering