134 / 2023-04-14 16:24:17

On finger collision of light fluid layers in reshocked Richtmyer-Meshkov flows

Richtmyer-Meshkov instability; Shock waves

辐射和流体力学 > 辐射和流体力学-海报

The Richtmyer-Meshkov instability (RMI) occurs when a shock wave impacts a fluid interface with different densities ^[1,2]. Due to the induction of baroclinic vorticity, finger-like structures including bubbles (light fluid penetrating heavy fluid) and spikes (heavy fluid penetrating light fluid) occur in the nonlinear stage. RMI is regarded as one of the main reasons for the failure of inertial confinement fusion (ICF) due to its role in enhancing the mixing of ablator materials and fuels. Therefore, in ICF, how to inhibit the perturbation growth owing to RMI has been concerned. A light fluid layer is the fundamental component of the double-shell capsule ^[3]. The finger collision taking place in the light fluid layer is helpful in reducing the growth of spikes and/or bubbles. Additionally, the reflected shock (i.e., reshock) from the capsule center is inevitable, which determines the final type of finger collision. Consequently, it is of significance to study the finger collision of a light fluid layer under reshock conditions.

Shock-tube experiments are conducted to investigate the finger collision of light fluid layers under reshock conditions. The extended soap-film technique is adopted to generate the initial fluid-layer interfaces with in-phase and anti-phase conditions. A general one-dimensional theory is developed, which reasonably predicts the motions of interfaces and waves. After reshock, the bubble-spike and spike-spike collision are observed in in-phase and anti-phase cases, respectively. The spike-spike collision has a stronger inhibiting effect on the growth of mixing widths compared to the bubble-spike collision. The interface-coupling effects and wave effects are quantified, and the nonlinear model considering the two effects provides a good prediction of the fluid-layer perturbation growth.

 

[1] R. D. Richtmyer, “Taylor instability in shock acceleration of compressible fluids,” Commun. Pure Appl. Math. 13, 297–319 (1960).

[2] E. E. Meshkov, “Instability of the interface of two gases accelerated by a shock wave,” Fluid Dyn. 4, 101–104 (1969).

[3] Montgomery D S, Daughton W S, Albright B J, et al. “Design considerations for indirectly driven double shell capsules,” Phys. Plasmas 25, 092706 (2018).