Investigation of transitional structures in artificially excited boundary layer flows by means of stereo and multi-plane PIV

Abstract

Two different experiments have been carried out by means of multi-plane and stereo PIV in order to analyze the structures of late transitional boundary layer flows. To achieve a better understanding of the characteristics and structures of ''natural'' transition scenarios, measurements in different complex initiated transitional boundary layer flows on a wing glove of a 2-D airfoil have been performed. Additionally, artificially-generated turbulent spots in a laminar flat-plate boundary layer have been investigated in detail. Instantaneous velocity vector fields measured in different planes parallel to the wall and special statistical approaches applied to the vector fields of turbulent spots, yield valuable information about the structures leading to the breakdown process and governing the turbulent mixing of the boundary layer flow.