E124 後退円柱三次元境界層上に発達する流線曲率不安定の挙動(E-12 遷移と不安定性(2),一般講演)

概要

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Instability of the three-dimensional boundary layer on a yawed circular cylinder is investigated experimentally by introducing acoustic disturbances from a point near the attachment line. It is aimed here to exemplify the flow dominated by streamline-curvature instability rather than cross-flow instability, which has been often observed in many swept-wing flows. In upstream regions of the disturbance wedge originating from the point source, both streamline-curvature and cross-flow disturbances are superposed on each other and yield complicated amplitude distributions. A newly proposed method enables to decompose the distorted amplitude distribution into contributions from the two instability modes. Detailed observations, however, show that the cross-flow mode decays with the distance from the source much faster than the streamline-curvature mode and allows the latter to be dominant in further downstream region. Fundamental characteristic of the streamline-curvature instability wave is confirmed by examining its phase distribution in the spanwise and normal directions. Wave numbers and spatial growth rates are in good agreement with theoretical predictions.
2004-08-09