2001 年 49 巻 572 号 p. 316-321
The unsteady flowfields of the sonic jet impinging on a flat plate are numerically investigated using the two-dimensional axisymmetric Euler equations. The characteristics of the jet oscillations qualitatively agree with the experimental results, and the mechanism of jet oscillation and the physical model of sound wave generation are discussed. The jet oscillations have the same period as the sound waves, because passing of sound waves around the nozzle exit causes oscillations of the jet itself. The mechanism of jet oscillations consists of sound waves passing and the vortex convection. In the mechanism, the time delay between the sound wave passing and the vortex occurrence at the nozzle lip is newly pointed out and corresponds to half wave length of the sound wave. A physical model including the time delay is newly suggested and well agrees with both computational and experimental results.