PIV EXPERIMENT STUDY ON INTERACTION BETWEEN PULSED LASER PLASMA AND NORMAL SHOCK

The interaction between pulsed laser plasma and supersonic flow field has important application value on aircraft drag reduction and heat insulation, ignition and combustion assistance. In order to quantitatively study the velocity field and vortex structure, particle image velocimetry (PIV) experiments were carried out on laser plasma and its interaction with normal shock wave. The nanosecond pulse laser energy deposition system and PIV measurement system were established on the shock tube experimental platform. By quantitatively measuring, the flow characteristics of laser air bubbles and hot core induced by laser plasma are explored. The flow characteristics and evolution of laser plasma under the impact of normal shock waves are revealed, and the influence of laser energy magnitude and deposition position on the interaction process is given. The results show that the velocity distribution in the laser air bubble is not symmetrical about the breakdown point in the laser incidence direction, but the flow velocity near the laser incidence direction is slightly larger than that far from the laser incidence direction. The baroclinic pressure leads to the generation of vortex rings in the early stage of hot core evolution, and the later stage is dominated by shearing force. When the normal shock interacts with the laser air bubble interface and the hot core interface, the baroclinic vorticity is generated. When the laser energy is 87.8 mJ and the normal shock Mach number is 1.41, the vorticity generated at the hot core interface is one order of magnitude larger than that in the static air. The key process of the interaction between the laser and the normal shock wave is that the hot core evolves into a vortex ring under the impact of the normal shock wave. The deposition of laser energy in front of the shock wave can obtain a more significant vortex ring.