On The Richtmyer-Meshkov Instability Of Cylinders

Interface instability is a common phenomenon in fluid mechanics. When an initially perturbed interface is impinged by a shock wave, due to the misalignment of pressure gradient and density gradient, the perturbation on the interface will develop with time and finally induce turbulent mixing, which is called Richtmyer-Meshkov(RM) instability. Because of its academic significance in vortex dynamics and turbulent mixing as well as some applications, such as supersonic combustion, inertial confinement fusion and supernova explosions, much attention has been paid to the RM instability in recent decades. The interaction of a shock wave with a gaseous cylinder is a fundamental configuration for RM instability study and the interface is formed through nitrocellulosic membrane or continuous interface technique, while each method has some shortcomings. Furthermore, much attention has been paid to two-dimensional (2D) cylinders and little attention is paid to three-dimensional (3D) cylinders. In this work, a wire restriction method using soap technique is introduced to form the cylinder and the shortcomings of nitrocellulosic membrane and continuous interface could be largely avoided. Furthermore, we investigate the interaction of a shock wave with3D (concave and convex) gas cylinders and analyse the3D effect on RM instability.A wire-restriction method using soap film technique is proposed to form cylinders. Two wires are mounted on the wall to restrict soap film and the formed interface could be easily controlled. At the same time, the effects of gas diffusion and membrane fragment are largely avoided. Based on the2D cylinders,3D cylinders can be formed by controlling the pressures inside the cylinder and they lay the foundations for3D RM instability study.The high-speed schheren photography is employed to study the interaction of a mach1.2planar shock wave with an Air/SF6cylinder and an SF6/N2cylinder. The heavier N2is adopted in the light cylinder to reduce the effect of soap film. Little disturbance could be seen in the experiment and some new features occur in the flow field. Furthermore, the experimental result is compared with the computational result and good agreement could be found between them. The experimental result also agrees well with the one-dimensional (1D) gas dynamics prediction Finally, the wire-restriction method to form soap film interface is proved to be feasible and reliable.It is found that particular phenomena occur for three-dimensional case, such as the stratification of the upstream and downstream boundaries. Special attention is given to the3D effect on the interface evolution. Compared with the2D case, the growth rate is largely influenced due to the vorticity induced by the vertical curvature. The vorticity induced by the vertical curvature and the horizontal curvature leads to the change in interface morphology and growth rate.In this work, a wire-restriction method of using the soap film technique is proposed to generate a cylindrical interface, the formed interface is free of holder and the gas diffusion is largely reduced. The3D effect on shock-cylinder interaction is studied and the3D effect study lays the foundation for3D computation and theoretical model...