509 / 2019-03-19 11:05:30

Evolution of Shocked Finite-thickness Fluid Layer

Fluid layer; Shock impact; Richtmyer-Meshkov instability

全体主题 > Interface Instabilities at Extremes

When an interface separating two fluids of different properties is impulsively impacted by a shock wave, the perturbations initially present at the interface will grow with time, which is referred to as Richtmyer-Meshkov (RM) instability. Over the past decades, the RM instability has attracted increasing attention due to its significance in a wealth of academic research and engineering applications, such as in inertial confinement fusion (ICF) and supernova collapse.

Previous studies mainly concerned the RM instability on the classical case of two semi-infinite fluids. However, ICF capsules and supernovae both consist of concentric layers of different materials in a spherical geometry. As a result of high-energy lasers or star collapse, shock waves are generated and interact with these multiple layers. However, little attention has been given to shock waves interacting with multiple interfaces, a set-up relevant to ICF and supernova collapse.

In the present work, an air/SF6/air finite-thickness fluid layer impacted by a shock wave is experimentally investigated in a shock tube. The middle SF6 layer is created by the extended soap film technique and has perturbations either on its upstream or downstream side, or on both sides, in which case the perturbations may be in-phase or anti-phase, as shown in Figure 1 (left). A high-speed schlieren photography is employed to monitor the flow field, and complete evolutions of the fluid layer and the wave patterns are well captured. The motion of an air/SF6/air fluid layer with no perturbations on two sides is first analyzed to evaluate the effect of reflected waves inside the layer on the dynamics of gas interfaces. Then, the effects of initial amplitudes and phase difference of perturbations on two sides on the time-variant amplitude growth are investigated, as shown in Figure 1 (right). Finally, predictions of three linear models are compared with the amplitudes of perturbations on two sides of the air/SF6/air finite-thickness fluid layer in the present work.