Locations and Oscillation Phenomena of Pseudo-Shock Waves in a Straight Rectangular Duct : 1st Report, High-Speed Children Observation

Abstract

The effect of the locations of pseudo-shock waves on the oscillations of pseudo-shock waves in a straight rectangular duct when the flows are choked at the duct exits has been experimentally investigated using high-speed schlieren films. The results show ; (1) the λ-type pseudo-shock wave which is produced at the upstream side of the duct oscillates with a small amplitude of 0.2D and low frequency (below 40 Hz), where D=50 mm is the width of the duct. (2) the X-type pseudo-shock wave which is produced at the downstream side oscillates with an amplitude of 0.3D and with frequencies below about 70HZ and high frequencies of 150 to 250 Hz. (3) The cause of the λ-type pseudo-shock wave oscillation is the boundary layer thickness oscillation in the pseudo-shock wave.