## 1 Introduction  
The gas-solid two-phase flow resulting from interactions between a shock wave and solid particles is highly complex and difficult to observe experimentally [1; 2]. However, workable knowledge regarding this process has numerous practical applications. For example, the fire-extinguishing bullet is filled with solid fire-extinguishing powder, and the dispersion uniformity of the solid powder directly affects the fire-fighting effect in practice [3]. In industrial explosion accidents, it can effectively abate the accident hazards and reduce the probability of secondary explosion by preventing the hoisting of combustible dust particles on the ground that is caused by the shock wave [4; 5]. The fuel air explosive (FAE) that appeared in the Vietnam War marked a notable advancement in conventional weapons. The fuel's dispersion range and particle concentration distribution during the explosion of solid FAE are the major factors influencing the explosive power [6; 7].  
Many previous researchers have investigated compressible gas-solid two-phase flows, and particularly the interactions between shock waves and particles. [PERSON] et al. [6] used shadow photography systems to observe the flow fields of particle swarms driven by shock waves under various Mach numbers. They conducted numerical simulations using the finite difference method;their results were repeated in a physical experiment. [PERSON] et al. [7] employed hybrid explosives to investigate the rapid dispersion of solid particles. They observed the interactions between shock waves and solid particles via high-speed camera. [PERSON] et al. and [PERSON] et al. [8; 9] studied the diffusion and attenuation of shock waves propagating amid solid particles, then analyzed the formation mechanism of reflected shock waves. In addition, the shock wave diffraction process may be numerically simulated to explore the interactions between shock waves and single particles [10; 11]. [PERSON] et al. [12; 13], [PERSON] et al. [14; 15; 16], and [PERSON] et al. [17] adopted body-fitted grids in their numerical analyses of fluid/single-particle interactions, providing workable insight into the unsteady force and heat transfer of shock interacting with deformable particles.  
In the previous studies [18; 19; 20; 21; 22; 23], plenty of meaningful research results have been acquired. However, there are still many aspects that can be further improved. For instance, a limited number of test parameters were usually captured experimentally, but it was difficult to obtain detailed flow field information, especially for the three-dimensional vortex structure generated by shock waves. Furthermore, many numerical investigations were conducted on a single particle, but there has been little study on the entire particle groups, which has not been conducive to further understanding the movement characteristics of the solid particles.  
Therefore, in this paper, theoretical analysis, shock tube experiments, and computational fluid dynamic (CFD) simulation were combined to study the interaction process between a shock wave and solid quartz sand particles of different sizes. The detailed information of particle motion and flow field evolution during the gas-solid two-phase flow was obtained, and the complex physical phenomenon and formation mechanism considered in depth. This work may facilitate a more comprehensive understanding of the interaction mechanism of gas-solid two-phase flow, which has practical significance in terms of dust explosion safety protection, FAE weaponry, and similar applications.