Experimental study of the stabilization of Tollmien-Schlichting waves by finite amplitude streaksReport as inadecuate

Experimental study of the stabilization of Tollmien-Schlichting waves by finite amplitude streaks - Download this document for free, or read online. Document in PDF available to download.

* Corresponding author 1 KTH Mechanics, SE-100 44 Stockholm, Sweden 2 II Facoltà di Ingegneria, Università di Bologna, 47100 Forlì, Italy 3 LadHyX - Laboratoire d-hydrodynamique

Abstract : It has recently been found by using temporal and spatial numerical simulations that steady optimal streaks of moderate amplitude, i.e., sufficiently large but not exceeding the critical amplitude for the inflectional instability, are able to reduce the growth of Tollmien-Schlichting TS waves up to their complete suppression. This investigation aims at experimentally verifying this stabilizing effect by generating stable and symmetric, close to sinusoidal, streaks of moderate amplitudes ~12% of the free-stream velocity by means of a spanwise array of cylindrical roughness elements. The three-dimensional 3D streaky base flow is then subjected to a secondary instability generated through a spanwise slot in the plate by means of regulated blowing and suction. In this study the stabilizing role of the streaks on TS waves is unambiguously confirmed and by increasing the height of the roughness elements, thus inducing larger amplitude streaks, we are also able to show that the stabilizing action on the TS waves increases with the streak amplitude. These results are the first to confirm the numerical predictions reported in earlier works. The full cross-stream plane has been measured at different downstream positions allowing a complete evaluation and comparison of the different amplitude measures used in previous experimental works. Furthermore, theoretical impulse response analysis and stability calculations are applied to the present experimental streaky base flow enabling a qualitative comparison of the 3D modulated TS wave distribution. © 2005 American Institute of Physics.

Author: J.H.M. Fransson - L. Brandt - A. Talamelli - Carlo Cossu -

Source: https://hal.archives-ouvertes.fr/


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