The raindrop impact is very important in soil erosion problems on hill slopes, while the splash characteristics (especially the jet and mixing) are crucial in raindrop impact processes. Focusing on the jet and mixing features in this process, a series of numerical experiments and discussion are conducted in this study. The meshless Smoothed Particle Hydrodynamics (SPH) method is employed and validated with the theoretical solution and experimental data. Two groups of numerical experiments, focusing on the jet around the rigid surface and the mixing between the drop and different underlain water layers respectively, are carried out. In the first group of numerical experiments, the effect of incidence angle of the drop is discussed. A high speed jet strip is found near the rigid surface and varied with incidence angle of the raindrop. In the second group of numerical experiments, it is found that full mixing between drop and water layer only happened in a very close range around the impact zone while the outer zone is just simply driven away. Two kinds of mechanism on jet occurrence and mixing are proposed and explained based on the simulated results.

The raindrop impact is very important in soil erosion problems on hill slopes, while the splash characteristics (especially the jet and mixing) are crucial in raindrop impact processes. Focusing on the jet and mixing features in this process, a series of numerical experiments and discussion are conducted in this study. The meshless Smoothed Particle Hydrodynamics (SPH) method is employed and validated with the theoretical solution and experimental data. Two groups of numerical experiments, focusing on the jet around the rigid surface and the mixing between the drop and different underlain water layers respectively, are carried out. In the first group of numerical experiments, the effect of incidence angle of the drop is discussed. A high speed jet strip is found near the rigid surface and varied with incidence angle of the raindrop. In the second group of numerical experiments, it is found that full mixing between drop and water layer only happened in a very close range around the impact zone while the outer zone is just simply driven away. Two kinds of mechanism on jet occurrence and mixing are proposed and explained based on the simulated results.</span

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