Visualization of supersonic flow using O-2-LIPF

As a method for analysis of supersonic flow, visualization of the flow field structure using LIF of tracers seeded in a carrier gas has been employed. In this study, the capability of imaging of supersonic flow using O-2-LIPF (laser-induced predissociative fluorescence) is examined. Since oxygen is one of the main constituents of air, O-2-LIPF may enable visualization of air flow in a high-speed wind tunnel without tracers. However, because the visualization of the flow field below room temperature using O2-LIPF is very difficult, it has been applied only to high enthalpy and combustion flow, not to high-speed flow at low temperature. In this study, the supersonic oxygen flow is visualized by O-2-LIPF using an ArF excimer laser and a high-sensitivity CCD camera. If the CCD camera is set at a long exposure time (1200 sec) and the scattered laser beam is suppressed sufficiently, the supersonic oxygen flow below room temperature can be imaged successfully using O-2-LIPF.