Visualization of shock wave in hypersonic flow using electric discharge

Based on the relationship of the electric discharge radiation intensity and gas density, the electric discharge visualization system was set up in hypersonic impulse wind tunnel FD-20. Three different test models are employed to explore the practicability of electric discharge for visualization of hypersonic flow structures under the flow condition of mach number Ma=12.16 and static pressure p≈106Pa. The experimental models include a plate, a combination of a cube and a plate (labeled as plate-cube), and a simplified inlet. In the plate experiment, the shock wave between electrodes was accurately observed by the electric discharge and the shlieren respectively, and the two methods gave a merely 0.21° difference in the shock wave angle. In the plate-cube experiment, flow structures on two different slices were obtained by the electric discharge. Shock structures on the central plane slice are basically the same as those obtained by the schlieren and CFD, and shock structures on the slice far away from the central plane are also confirmed by CFD. In the simplified inlet experiment, a diamond shock cell was observed by the electric discharge in the internal flow region of the inlet. The measured size of the diamond shock cell is slightly different from the numerical result with a deviation of 7.9%. These results demonstrate that electric discharge can be used to visualize shock structures on different flow slices and the internal flow region in the hypersonic impulse wind tunnel, and is especially suitable for the observation of local complex flow structures.