Experimental Investigation On The Gaseous Interfacial Instability Induced By Moving Shock

Richtmyer-Meshkov (RM) instability is a common phenomenon in the fluid me-chanics, which generally means the small initial perturbation on the interface separat-ing two fluids with different densities will grow with time after shock acceleration due to the misalignment of pressure and density gradients, resulting in turbulent mixing eventually. RM instability occurs in the context of both academic research and appli-cations ranging from Inertial Confinement Fusion (ICF) to supernova explosions and other fields. Especially in past decades, driven by ICF, the RM instability research gains more attention by researchers all over the world. Prominent work is obtained, no matter in experiments, theories or computations. Corresponding research on RM instability is also carried out by domestic researchers. However, the experimental results are lim-ited since much attention has been paid to the numerical simulations and experimental work is needed to be carried out in order to understand the mechanism in this process and diminish the gaps with the advanced countries. Based on these, some experimental studies are conducted in this paper, including:1. Under the condition of planar shock Mach number1.2, high-speed schlieren tech-nique is adopted to visualize the interaction of a shock wave with air/helium and air/SF6interfaces and fruitful results are obtained. Detailed analyses and dis-cussions are performed and compared with the numerical and theoretical results, which also validate the views of research abroad. In addition, the higher time resolution used ensures the repeatability of the experiment and provides us an opportunity to find some phenomena.2. Under the condition of initial planar shock Mach number1.2, the experimental investigations of helium and SF6bubbles under re-shock conditions are carried out using high-speed schlieren technique. Re-shock with different times is re-alized through a moving reflected endwall, and a large amount of experimental results are obtained. The wave patterns and evolution of interface are analysed in detail. The velocities of shocks and interfaces are measured and compared with one dimensional model and agreement is reached.3. In the horizontal shock tube, a planar incident shock is successfully converted into a cylindrical converging one by designing the specific curved wall profile based on shock dynamics theory. The novel method of generating cylindrical converg-ing shock wave is simple and feasible compared with other methods. Meanwhile, a parametric study on the cylindrical converging shock wave is carried out which will helpful for further understanding the shock focusing phenomenon and pro-vide the theoretical guide for test section manufacture.4. The technique of high-speed laser sheet combined with the membrane-less gas cylinder is used to investigate the evolution of a SF6gas cylinder impacted by the cylindrical converging shock wave with different strengthes which are realized by placing the gas cylinder at different positions in the converging part. The in-fluence of the converging shock strength on the interfacial instability is observed and discussed. Moreover, the disparities with the results under the planar shock condition are also highlighted.