Pressure and shear stress caused by raindrop impact at the soil surface: Scaling laws depending on the water depth
2016
Nouhou Bako, Amina | Darboux, Frédéric | James, Francois | Josserand, Christophe | Lucas, Carine | Unité de Science du Sol (Orléans) (URSols) ; Institut National de la Recherche Agronomique (INRA) | Mathématiques - Analyse, Probabilités, Modélisation - Orléans (MAPMO) ; Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS) | Laboratoire Sols et Environnement (LSE) ; Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL) | Institut Jean Le Rond d'Alembert (DALEMBERT) ; Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS) | grant ANR ‘TRAM’ 13-BS09-0011-01
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Show more [+] Less [-]English. Raindrop impact is an important process in soil erosion. Through its pressure and shear stress, raindrop impact causes a significant detachment of the soil material, making this material available for transport by sheet flow. Thanks to the accurate Navier-Stokes equations solver Gerris, we simulate the impact of a single raindrop of diameter D, at terminal velocity, on water layers of different thickness h: D 10 , D 5 , D 3 , D 2 , D, 2D, in order to study pressures and shear stresses involved in raindrop erosion. These complex numerical simulations help to understand precisely the dynamics of the raindrop impact, quantifying in particular the pressure and the shear stress fields. A detailed analysis of these fields is performed and self-similar structures are identified for the pressure and the shear stress on the soil surface. The evolution of these self-similar structures are investigated as the aspect ratio h/D varies. We find that the pressure and the shear stress have a specific dependence on the ratio between the drop diameter and the water layer thickness and that the scaling laws recently proposed in fluid mechanics are also applicable to raindrops, paving the road to obtain effective models of soil erosion by raindrops. In particular , we obtain a scaling law formula for the dependance of the maximum shear stress on the soil on the water depth, quantity that is crucial for quantifying erosion materials.
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