Initial Moving Mechanism of Densely-Packed Particles Driven by a Planar Shock Wave

Hua Lv,Yunming Zhang,Zhongqi Wang,Jianping Li,Furen Ming

doi:10.1155/2021/8867615

Abstract

The initial moving mechanism of densely packed particles driven by shock waves is unclear but vital for the next accurate calculation of the problem. Here, the initial motion details are investigated experimentally and numerically. We found that before particles show notable motion, shock waves complete reflection and transmission, and stress waves propagate downstream on particle skeleton. Due to the particle stress wave, particles successively accelerate and obtain an axial velocity of 6–8 m/s. Then, the blocked gas pushes the upstream particles integrally to move downstream, while the gas flow in the pores drags the downstream particles to separate dramatically and accelerate to the velocity of 60–70 m/s. This gas push-drag dual mechanism transforms densely packed particles into a dense gas-particle cloud, which behaves as the expansion phenomena of the dense particles.

Highlights

In compressible dilute gas-particle flows, collisions between particles can be ignored, and particles are mainly affected by the flow field
Igra and Takayama [3] laid some small spheres on the shock tube floor to be driven by planar shock waves and photographed to investigate the drag force on it
Stewart et al [26] used the discrete element method code LIGGGHTS to simulate the traversal of a planar shock into a granular bed sealed at the bottom of a tube and statistically investigated the traveling wave structure in the particle concentration downstream of the shock

Summary

Experiment of the Initial Movement of the Densely Packed Particles

E experiments were carried out in a horizontal multiphase shock tube cooperated with a highspeed schlieren imaging system and a synchronized pressure measurement system. E driver and driven sections of the shock tube, which are separated by the diaphragm, are filled with high-pressure air and atmospheric air, respectively. When the pressures of the driver air P1 are 3, 4, and 5 MPa, the Mach numbers of the incident shock measured by the crossing time Ms are 2.18, 2.31, and 2.38, respectively. E driven section made of C45E4 steel is totally 1640 mm long. It consists of four subsections, which are connected by flanges. A densely packed sand wall carried by a fixed thin-walled particle carrier and wrapped by papers is located in the middle of the test section. A densely packed sand wall carried by a fixed thin-walled particle carrier and wrapped by papers is located in the middle of the test section. e sands packed in the wall are quartz sands with the most frequent diameter Dm of 0.646 mm and a density of 2.64 g/cm3. e initial porosity of the densely packed particle wall is measured to be 0.561

Experiment Results

Reflected shock

Simulation of the Initial Movement of the Densely Packed Particles

Validation of the Euler–Lagrange Coupling in AUTODYN 3D

Discussions of the Initial Motion Mechanism