552 / 2019-03-20 15:14:05

Smoothed particle hydrodynamics simulation on Richtmyer-Meshkov instability induced by strong cylindrical convergent shock

Smoothed Particle Hydrodynamics; Riemann solver; Richtmyer-Meshkov instability; Extreme conditions; Cylindrical convergent shock; Numerical simulation

全体主题 > Interface Instabilities at Extremes

The Richtmyer-Meshkov (RM) instability induced by converging shock waves at interfaces of different substances has an important academic significance and engineering background in the field of inertial confinement fusion. The macroscopic fluid dynamics method based on grid discretization requires high order precision algorithm to track the interface evolution accurately because of numerical diffusion problem, and it is extremely difficult to track the complex interface such as large deformation, fragmentation and merging. The Smoothed Particle Hydrodynamics (SPH) method can effectively overcome above difficulties by using the pure lagrangian algorithm. However, the classical SPH algorithm needs to add artificial viscosity to deal with strong discontinuities, and it is empirical in instability simulations involving strong impact. In this paper, the SPH algorithm based on HLL Riemann solvers is adopted and improved to achieve an effective resolution and tracking of discontinuities such as strong shock and high density ratio interface. One-dimensional numerical verification proves the reliability and robustness of the code, and further simulations the multimode RM instability induced by different cylindrical converging shock impacting the quadrilateral light/heavy gas interface. The comparison with the existing experimental results shows that the simulation results are consistent with the experimental results quantitatively. By analyzing the density and pressure changes in the process of interface evolution, it is found that the method adopted in this paper can accurately track the complex interface and wave evolutions during converging RMI process. Further FFT analysis in mode spatial frequency range shows that in converging process of multimode RMI induced by the strong shock waves, more the high frequency scales of instability amplitudes will be excited, which may further improve the turbulence mixing under strong compression conditions. The relevant results lay a preliminary foundation for further understanding and explanation of RMI convergence mechanism under extreme shock conditions with SPH simulations.