Effects of surface corrugation on the stability of a zero-pressure-gradient boundary layer. (25th February 2014)

• Record Type: Journal Article
• Authors: Ma'mun, Mochamad Dady; Asai, Masahito; Inasawa, Ayumu
• Is Part Of: Journal of fluid mechanics. Volume 741(2014:Feb.)
• Page Start: 228
• Page End: 251
• Publication Date: 2014-02-25
• Subjects: boundary layer stability, -- instability, -- transition to turbulence; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2013.653
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract: The effects of surface corrugation with small amplitude on the growth of Tollmien–Schlichting (T–S) waves were examined experimentally in a zero-pressure-gradient boundary layer. Two- and three-dimensional corrugations of sinusoidal geometry with wavelengths of the same order as that of the two-dimensional T–S wave were considered. The corrugation amplitudes were one order of magnitude smaller than the boundary-layer displacement thickness. Streamwise growth of T–S waves on the corrugated walls was compared with that in the boundary layer on the smooth surface. A distinct difference was found in the destabilizing effect between the two- and three-dimensional corrugations. The two-dimensional corrugation significantly enhanced the growth of two-dimensional T–S waves even when the corrugation amplitude was only ${\sim }$ 10% of the displacement thickness. On decreasing the corrugation amplitude, the growth rate of two-dimensional T–S waves asymptotically approached that in the smooth-wall case. On the other hand, the three-dimensional corrugation had only a small influence on the growth of two-dimensional T–S waves even when the corrugation amplitude was as large as 20% of the displacement thickness. For three-dimensional corrugations, however, a pair of oblique waves was generated and developed by an interaction between the two-dimensional T–S wave and the corrugation-induced mean-flow distortion for the corrugation wavelength considered. On increasing the corrugation amplitude, the oblique waves generated were increased in amplitude and thus significantly influenced the secondary instability process.