Experimental study on the formation of multi-phase powder jets driven by explosive loadings

In order to investigate the onset and development of the granular jetting in the near field, the dynamics of the fragmentation in both dry and wet sand shells subject to the explosive loadings via high-speed photography was recorded, and further the critical conditions of the fragmentation onset, the number and average mass of jets formed from wet shells with different saturation, and the cumulative mass distribution of the jets were derived. The results shows that a small amount of interstitial fluid, only accounting for 3.22% by mass, is conducive to the significant postpone of the shell fragmentation, leading to a pronounced denser jetting structure. This trend persists with increasing saturation until the saturation degree of the wet sand reaches 64.8%. Meanwhile the mass distribution of wet jets gets narrower and shifts towards the characteristic mass. The structure of jetting is dependent on the explosives as well, because the jets driven by the explosive 8701, which has higher detonation speed than TNT, become finer and more even than those formed by the explosion of TNT.