Influence of the Plastic Number on the Evolution of a Yield Stress Material Subjected to a Dam Break

Abstract

Dam break problems occur in a variety of applications. In the present paper we are especially concerned with the mining industry, where a dam break can be a catastrophic event with significant harm to the environment. In this case, the materials involved have a yield stress property, i.e., they flow only when a threshold is overcome by the stress that acts on the material. The plastic number, which measures the importance of the yield stress in the overall characteristic stress, is the main dimensionless number analyzed, and carbopol solutions are the kind of material employed. Since slip is common in motions of yield stress materials, the influence of this phenomenon is investigated by a comparison between the flow over a smooth and a rough surface. An image processing that captures the evolution of the shape of the interface as well as particle image velocimetry measurements were employed as tools to understand the role played by the plastic number in the problem. A number of cases presented a triangular depression that originated from a difference between the flow below the initial yield surface position and a rigid body motion above the initial surface position.

Review of Experimental Investigations of Dam-Break Flows over Fixed Bottom

“…As shown in Table 7, experiments were conducted in simple laboratory facilities (planforms or rectangular channels), sometimes with steep bottom slopes [302]. Typically, the liquids used were aqueous suspensions or mudflows with viscoplastic behavior, but also Bingham fluids are used [307]. Moreover, the test conditions usually considered are characterized by a total dam-break and dry downstream bottom, with few exceptions [64,303].…”

Viscoplastic dam-breaks

“…Here, some of these strategies are combined and applied to viscoplastic dam-breaks under gravity, an important flow case widely exploited in food, mineral and concrete industries to assess rheological signatures of complex fluids. In this free surface flow situation, a fluid column collapses under gravity and, at stoppage, its spreading level and/or final height are/is measured and linked, for instance, with the yield stress (Pashias et al, 1996;Schowalter and Christensen, 1998;Clayton et al, 2003;Saak et al, 2004;Roussel and Coussot, 2005;Staron et al, 2013;Pierre et al, 2013;Gao and Fourie, 2015;Liu et al, 2016Liu et al, , 2018Modolo et al, 2019). Practical variations of this fundamental free surface complex flow include for instance the L-box, a three-dimensional free surface flow of a non-Newtonian fluid between bars as obstacles attached to a L-shape channel used to evaluate the workability of concretes (Nguyen et al, 2006;Roussel, 2007;Chaparian and Nasouri, 2018), and the Bostwick Consistometer, a device widely used to easily recover food product rheological properties and based on a free surface non-Newtonian flow through a channel (Rao and Bourne, 1977;Balmforth et al, 2007).…”