Effect of Cylindrical Turbulators on the Swept-Wing Boundary Layer: 1. Scenarios and Efficiency of Turbulization

The main objective of the present study is to apply spanwise periodic rows of cylindrical turbulators to investigate the mechanism of forced turbulization of a swept-wing boundary layer with predominant cross-flow instability. The experiments are carried out using hot-wire anemometry in a low-turbulence wind tunnel at the Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, at low subsonic freestream velocities on a 25-degree swept-wing model. The results of detailed precision measurements of the mean and fluctuating flow structure are obtained in a wide spatial region in 12 different measurement regimes for five types of turbulators (and without them) at two flow velocities. The studied range of Reynolds numbers based on the cylinder height lies between 565 and 3613. This is the first part of this study, and it describes the main scenarios of turbulator-induced transition to turbulence. The high efficiency of turbulators is demonstrated. This study continues in part 2 [1].