# Experimental Study of Explosion Mitigation by Deployed Metal Combined with Water Curtain
## 3 Results  
### Explosive Driven Shock Tube  
Figure 9 shows the shock wave propagating at the outlet of the EDST when there was no perforated plate. The photographs were taken with high-speed imaging. Thanks to the mirror, set at 45\({}^{\circ}\) in front of the camera, imagery could be obtained from the axial direction simultaneously with the direct view. Consequently, events happening axially to the EDST outlet could be observed. The shock wave was not totally planar at the outlet of the tube; indeed, the two metallic plates, fixed parallel to the EDST at the end and which were used to clamp the perforated plates, reflected the shock wave (t = 1440 \(\upmu\)s). These two plates had a shoulder at their ends which provided additional thrust for the fixation of the perforated plates. These shoulders can be seen in Figure 4 and the shock wave visibly interacts with them (t = 1520 \(\upmu\)s). The shock wave emerging laterally from the EDST was visible in the mirror. It should be noted that the shock wave exited the EDST outlet immediately, but in the beginning the optical setup did not allow the observation of this expansion. Figure 8: First grid equipped with a pool fountain. Figure 7: (**a**) Reflected pressure gauge located on the wall behind the grids; (**b**) pressure gauge located in front of the first grid position. Figure 10 shows shock wave propagation through one deployed metal plate. The plate was positioned at a distance of 130 mm from the tube outlet and at a distance of 50 mm in front of the wall. At t = 1470 us, the shock wave when passing through the plate apertures split into several shock waves, one for each aperture, and these shock waves recombined further down. At t = 1530 us, the shock wave behind the plate became almost planar again. A complex structure of turbulence appeared just behind the grid and it persisted for some time; at t = 1510 us turbulence began to form along the backside the grid, and at t = 1790 us it was still observable. The reconbinated shock wave behind the perforated plate hit the wall and was reflected at t = 1570 us. The remaining shock wave, which did not pass through the grid and was reflected by it, became almost planar at t = 1550 us. Figure 10: Photographic results of high-speed video recording, showing shock wave propagation through one plate of deployed metal (20 us between each photograph). Figure 9: Photographic results of high-speed video recording, showing shock wave propagation at the outlet of the EDST (20 μs between each photograph). Figure 11 shows shock wave propagation through two deployed metal plates. The first plate was positioned at a distance of 90 mm from the tube outlet and at a distance of 90 mm in front of the wall. Grids were paired 40 mm apart. When passing through the apertures of the first plate (t = 1450 \(\upmu\)s), the shock wave split into several shock waves, one for each aperture, and these shock waves recombined further down. The transmitted shock wave was similar to the incident shock wave at t = 1490 \(\upmu\)s. At the back of the shock wave, between the two plates, lasting turbulence could be observed, especially immediately behind the first plate. The remaining shock wave, which did not pass through the first plate, was reflected, leading to the pattern captured at the back of this plate. Thereafter, the shock wave transmitted by the first plate impacted the second plate (t = 1510 \(\upmu\)s) and, once again, a part of the shock wave was transmitted and part was reflected. The wave reflected by the second plate propagated toward the first plate and, as it arrived near the plate, the shock front and the turbulence became less obvious. We could also see turbulence behind the second plate. Five reference tests were conducted without any plates and seven experiments were conducted with either one or two grids positioned at the outlet of the EDST. The reflected overpressure versus time was collected by the sensor inserted in the wall behind the plate.