ゲルトラー渦のスパン方向波長に対する初期撹乱依存性について(境界層・せん断流・遷移(1),一般講演)

概要

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Direct numerical simulation of the development of Gortler vortices in an asymptotic suction boundary layer over a concave wall has been executed. The simulation with a single mode initial disturbance shows formation and propagation of mushroom-shaped low velocity regions that are induced by upward advection from the wall due to the counter rotating Gortler vortices. In order to investigate the selection mechanism of their spanwise wavelengths, the initial disturbance composed of a fundamental mode and its first harmonic mode are introduced. In the case that the harmonic mode initially has half intensity of the fundamental mode, both modes grow exponentially and their amplitude reach equivalent amplitude resulting the spanwise wavelength of the Gortler vortices corresponding with the harmonic mode. For one-order lower initial disturbance of the harmonic mode, Gortler vortices develop with the the wavelength of the fundamental mode though both mode grow exponentially until non-linearity appears. These wave selections suggest that the energy ratio between the two modes at the end of their growth essentially affects the final wavelength of Gortler vortices.
2007-08-06