Influence of lateral confinement on granular flows: comparison between shear-driven and gravity-driven flows
- PDF / 1,883,954 Bytes
- 13 Pages / 595.276 x 790.866 pts Page_size
- 94 Downloads / 275 Views
ORIGINAL PAPER
Influence of lateral confinement on granular flows: comparison between shear‑driven and gravity‑driven flows Patrick Richard1 · Riccardo Artoni1 · Alexandre Valance2 · Renaud Delannay2 Received: 2 April 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The properties of confined granular flows are studied through discrete numerical simulations. Two types of flows with different boundaries are compared: (i) gravity-driven flows topped with a free surface and over a base where erosion balances accretion (ii) shear-driven flows with a constant pressure applied at their top and a bumpy bottom moving at constant velocity. In both cases we observe shear localization over or/and under a creep zone. We show that, although the different boundaries induce different flow properties (e.g. shear localization of transverse velocity profiles), the two types of flow share common properties like (i) a power law relation between the granular temperature and the shear rate (whose exponent varies from 1 for dense flows to 2 for dilute flows) and (ii) a weakening of friction at the sidewalls which gradually decreases with the depth within the flow. Keywords Granular flows · Confinement · Shear localization
1 Introduction A lot of examples of confined granular flows can be found both in nature and in industry, from geophysical flows confined by a canyon to grain transport in channels. Such types of flows are complex systems because confinement (e.g. top, bottom or sidewalls) may induce correlations as well as non-local effects that possibly have an influence over long distances [1]. Also, confined granular flows are likely to develop zones without shear and, consequently, they can experience erosion and accretion [2], which are still the subject of active research [3–6]. Therefore they are good systems to test theories dealing with both a solid and a fluid granular phases and how to handle the corresponding phase transition [7, 8]. Also, if one of the ultimate goal This article is part of the Topical Collection: Flow regimes and phase transitions in granular matter: multiscale modeling from micromechanics to continuum. * Patrick Richard patrick.richard@univ‑eiffel.fr 1
MAST‑GPEM, Univ Gustave Eiffel, IFSTTAR, 44344 Bouguenais, France
CNRS, IPR (Institut de Physique de Rennes)–UMR 6251, Univ Rennes, 35000 Rennes, France
2
of the physics of granular materials is to obtain a full 3D rheological model capturing the behaviour of granular flows, this model has to be fed by boundary conditions at sidewalls (velocity, granular temperature...). Studying confined flows, experimentally and/or numerically, can help to reach this goal by providing the aforementioned conditions. Recently, we have studied steady and fully developed (SFD) granular flows in two confined geometries: a laterally confined chute flow [2, 9–13] and a constant-pressure confined shear cell for which shear is imposed by a moving bumpy bottom [14, 15]. In the remainder of the paper we will refer to these two types of flows a
Data Loading...
