Simulation study of the colliding bulge and surface micro-jet of metal flyers driven by detonation

In the cylindrical implosion problem, the phenomenon of colliding bulge and surface micro-jet formation of two-layer metal flyers, which are driven by two slip detonations in opposite direction of the pole, is studied by simulation using Euler's program. Simulation results of the inner surface travel times of the lead flyer coincide well with the experimental results. In the polar position, there is a fracture cavity in the lead flyer, and a blunt bulge is formed on the inner surface. At the equator, large-scale fracture particles are generated as the inner surface of the lead flyer is growing. It is considered that the colliding bulge at the equator which seem to be continuous in the X-ray images is actually discontinuous, and it is composed of large-scale fracture particles and small-scale micro-jet particles. By analysis of the inner surface position on the optical images at different times, the maximum velocity of the lead micro-jet particles is obtained. It is found that the maximum velocity of the micro-jet particles is declined in the pole region, but at the equator its maximum velocity is increased with time. It is considered that the subsequent loading waves on the colliding bulge area may cause higher speed of micro-jet particles than the first loading wave. And then, the groove micro-jet model of the lead, which is loaded by impact, is used to be equivalent to the uniform disfigurement surface micro-jet. It is proved that both the micro-jet maximum velocity in the pole region and the velocity at the equator can be formed by the same uniform disfigurement surface, and the correctness of the experimental optical image is also verified. Finally, the restrained method of the colliding bulge and surface micro-jet in this problem is studied by simulation. The micro-jet maximum velocity of the lead flyer can be declined by changing the two opposite initiation points to the points close to the metal flyers in the pole region, and the main cause of collision bulge at the equator is that the Mach reflection is formed in the collision area because of the low sound velocity of lead.