Control of the vortical structure in the early stages of transition in boundary layers

The effect of suction and pressure gradient on controlling the production of the three-dimensional vortical structure due to secondary instability is investigated for a boundary layer in the presence of small but finite amplitude Tollmien-Schlichting wave. The subharmonic instability is the focus of the study due to its realistic application in low disturbance flight environment. The spanwise wavelength of the most unstable secondary subharmonic disturbance increases with the increase of control indicating possible alteration of the flow structure from H-type to C-type.