Experimental analysis of the evolution of steady disturbances in a flat plate boundary layer

Authors: Talamelli, A., Fransson, J. H. M., Brandt, L.B., Cossu, C.
Document Type: Conference
Pubstate: Published
Journal: Proc. 17th AIDAA 2003
Year: 2003


By using temporal and spatial numerical simulations, it has recently been found that the presence in the Blasius boundary layer of steady optimal streaks of moderate amplitude are able to reduce the growth of Tollmien-Schlichting waves up to their complete stabilization. This paper presents the first part of an investigation aimed at experimentally verifying the theory above. In particular, results from experiments, performed in the MTL wind tunnel in KTH, are presented in which low and medium amplitude stable streaks are generated using a spanwise array of roughness elements of circular section. These streaks are still boundary layer solutions and are self similar for the considered amplitudes. The experimental results are compared to the optimal streaks and the dominant factors explaining the discrepancy among the experimental streaks and the optimal streaks are depicted. Simple sub-optimal upstream conditions mimiking the effect of the roughness elements are found, which lead to streaks behaving as the experimental ones.