Drop impact on wet granular beds: water-content effects on the cratering

Drop impact events on wet granular bed show rich variety by changing the substrate composition. We observe the drop impact onto dry/wet granular substrates with different grain size (50-400 {μ}m) and water content (0-22 vol %). Although the impactor condition is fixed (impact velocity: 4.0 m/s, water drop radius: 1.8 mm), the experiment reveals that the post-impact behaviors of both impactor and target are strongly affected by the substrate composition. We sort these behaviors into several phases regarding liquid splashing and crater shapes left after the event. As these phases show relevance each other, we measure the mechanical characteristics of the substrates and find that the onset of splashing and particle ejection are explained by a fracture of the substrate. Furthermore, we discuss several timescales of the event to understand more detailed phase separations. Consequently, we find that the splashing phase and the crater shape are determined by a competition of the timescales of impact, penetration, and contact.