Numerical analysis of the drag on a rigid body in an immersed granular flow

• Published in: Computational particle mechanics Vol. 9; no. 3; pp. 393 - 406
• Main Authors: Coppin, Nathan, Constant, Matthieu, Lambrechts, Jonathan, Dubois, Frédéric, Legat, Vincent
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.05.2022; Springer Nature B.V; Springer Verlag
• Subjects: Classical and Continuum Physics; Computational Science and Engineering; Cylinders; Dimensional analysis; Drag; Engineering; Engineering Sciences; Finite element method; Fluidizing; Fluids mechanics; Grains; Granular media; Mathematical analysis; Mechanics; Numerical analysis; Rigid structures; Shear thickening (liquids); Shear zone; Solid mechanics; Stress distribution; Theoretical and Applied Mechanics; Thickening; Velocity; MigFlow; Granular drag; Janssen effect; Nonsmooth contact dynamics; Unresolved model
• DOI: 10.1007/s40571-021-00418-w
• ISSN: 2196-4378

The drag exerted on an object moving in a granular medium is subject to many studies: in dry grains, it depends on the stress – often due to gravity – inside the grains. For Froude numbers less than 10, the drag is independent of the velocity. In immersed grains, it is proportional to the apparent weight of the grains and it depends on both velocity and fluid viscosity. In this paper, the drag on a cylinder in dry and immersed granular flow is simulated with a multi-scale FEM-DEM model. The Janssen stress saturation effect before the flow and velocity independence of the drag are both reproduced. The semi-circular orientation of the stress field supports the hypothesis of a spherical zone of influence of the cylinder. This orientation does not significantly change upon flowing. The results show the velocity independence of the drag is due to particle friction. In the immersed case, the fluid contribution is negligible on its own. A dimensional analysis suggests that shear thickening should be taken into account. The transition between the quasi-static and the fluidized regime is accompanied by a decrease of the stress field downstream of the cylinder and a change in the shape of the shear zone.