On the Role of High- and Low-speed Streaks in Turbulent Wedge Lateral Spreading

2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Large roughness elements placed in laminar flat plate boundary layer flows introduce instabilities which form a turbulent wedge. The wedge spreads laterally after the initial roughness induced breakdown. Understanding the fundamental mechanisms responsible for lateral growth would provide valuable insight in laminar to turbulent transition in general and possibly suggest means of controlling this phenomenon. High and low speed streaks have been observed on the edges of turbulent wedges and these "dog-teeth" structures are believed to play a role in destabilizing the flow surrounding turbulent wedges. This paper investigates the formation of these structures and evaluates their responsibility for the lateral spreading rate of turbulent wedges using combined naphthalene flow visualization and hotwire measurements. Dog-teeth are successfully identified through these methods as well as the frequencies most amplified in the related destabilization process.

On the Role of High- and Low-speed Streaks in Turbulent Wedge Lateral Spreading Conference Paper