Visualization of the Three-Dimensional Flow Structure in a Transonic Diffuser by the Laser-Induced Fluorescence Method

The three-dimensional flow structure induced by normal shock wave/turbulent boundary-layer interaction in a transonic diffuser is investigated by a laser-induced fluorescence method. This diagnostic system uses an argon-ion laser as a light source, and the target gas is dry nitrogen with iodine seeded as a fluorescence material. The three-dimensional Mach number distributions are obtained by the system. Numerical flow simulation is also performed to check the reliability of the measurement and consider the flow field in detail. As a result, the numerical result represents good agreement with the measured flow field, and reveals that two vortices having the direction opposite to each other are generated in the vicinity of the rear leg of the bifurcated shock wave.