Decomposition of two kinds of instability waves in three-dimensional boundary layer near yawed attachment line

Naoko Tokugawa*, Prijo Kusumo** ,  Akira Nishizawa* ,  Shohei Takagi*

*National Aerospace Laboratory
**Aoyama Gakuin University

Artificial disturbances from a point source near the swept attachment line was experimentally introduced to separate unsteady disturbances due to both cross-flow and streamline-curvature instabilities and eventually to determine these critical Reynolds numbers. Since two instability modes near the source were not sufficiently dispersed, modulation of amplitude and phase distributions was observed. Assuming that such a modulation is due to linear superimposition of two modes, a method to decompose measured distributions of amplitude and phase is proposed. Experimental result shows that this assumption is valid near the peak positions of two modes. It is also shown that after this decomposition method was applied at various downstream locations, the characteristics of instability mode such as phase velocity, wave-number vector and so on are clarified. The critical Reynolds number of each mode is confirmed to be determinable. 
Received 22 October 2002, accepted 4 November 2002

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