Nicolas Brodu, Patrick Richard, Renaud Delannay
Granular flows down inclined channels with smooth boundaries are common in nature and in the industry. Nevertheless, the common setup of flat boundaries has comparatively been much less investigated than the bumpy boundaries one, which is used by most experimental and numerical studies to avoid sliding effects. Using DEM numerical simulations we find that flat boundaries induce a rich behavior, including granular convection and inverted density profiles suggesting a Rayleigh-B\'enard type of instability. Our work demonstrates that this complexity occurs at lower inclination angles compared to setups using glued grains on the boundaries, making it not only relevant but more likely to occur in the common situation of a rectangular conduit with flat base and sidewalls. In many aspects flows on a flat base can be seen as flows over an effective bumpy base made of the basal rolling layer. We have tested a simple viscoplastic rheological model (Nature 2006, vol 441, pp727-730) in average form. The transition between the unidirectional and the convective flows is then clearly apparent as a discontinuity in the constitutive relation.
View original:
http://arxiv.org/abs/1112.5351
No comments:
Post a Comment