要約

The present work investigates spanwise periodic modes introduced at the inception point (trip) of a developing turbulent boundary layer. Empirical evidence suggests that these modes can be persistent, and the idea here is to exploit this apparent persistence/amplification of weak lateral variations in turbulent boundary layers, to explore whether the downstream evolution can be substantially modified. Preliminary results, where micro vortex generators are used to introduce the spanwise modes at the trip, indicate the presence of spanwise alternating modes. These modes appear to strengthen after some distance downstream of their introduction for certain configurations (this strengthening can occur almost 350 blade heights downstream of the trip). Further, the spanwise wavelength of the trip seems to play a critical role in determining the downstream development and subsequent evolution of the turbulent boundary layer towards a canonical state. Collectively, these findings suggest that three-dimensionality introduced at the trip may be a viable approach to perturb the evolution of developing turbulent boundary layers over a large streamwise development length.