Real-Time Optical Measurement of Time-Dependent Shock Position

An optical system for the investigation of unsteady flows with oscillating shocks is described. The system consists of a line-scan TV camera incorporated with a conventional shadowgraph system along with simple image-processing electronics. A real-time analog signal representing the streamwise position of the shock is obtained. This paper presents a layout of the shadowgraph system and schematic of electronics for line-scan data processing along with a diagram of the PWM decoding circuit. System accuracy considerations are discussed.