Linear stability theory predicts that the most unstable disturbance of crossflow instability in three-dimensional boundary layers is a time dependent mode rather than a stationary mode. Stationary rather than traveling mode has been predominantly observed in natural disk flow, spinning in still air, which is known to be a typical example of three-dimensional boundary layers. The present paper discusses this mode selection mechanism of crossflow instability on the basis of reviewing both experimental and theoretical research and making linear stability calculations inclusive of a wall-curvature term as well as streamline-curvature and non-parallel terms. This reveals that the wall curvature plays a key role in the mode selection mechanism of three-dimensional boundary layers and that initial amplitudes of unstable disturbances are of principal importance.
The mode-selection mechanism of cross-flow instability in three-dimensional boundary layers
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