Historically, chutes were designed based on experience and trial-and-error methods. These designs were checked, with no guarantee to work, by building scaled-down models that are not only time and cost prohibitive but also difficult to scale. The major difficulty arises due to the fact that unlike fluid flows, there are no scaling laws for bulk solids. In particular, cohesion and frictional forces in a large-scale operations are different in comparison with a small-scale model. Using a dimensionless quantity such as a Froude number alone (ratio of inertia to gravity force) is flawed due to the mere fact that cohesion and friction forces are not included in this number. As such, this methodology does not include comprehensive dynamic scaling and most importantly, is highly risky for the time and cost put into it. More often, these approaches have a strong element of trial and error, and benefit from a great deal of on the job experience, but are limited in their application and usefulness.
DEM technology has been used as a research tool for many applications. However, just recently it is gaining popularity as a major virtual design tool for large chutes due to its ease of use and cost efficiency in comparison with classical approaches, including the scaled-down model. Although a very useful and powerful tool it has challenges and limitations. In particular, just as other computational predictive tools such as CFD or FEA, it needs to be calibrated; and garbage in to the model is garbage out of it. It is not a plug and play tool and the input and selected models need to be well thought through, and its impact on the bulk behavior needs to be understood. The contact and cohesion force laws used will vary the inputs significantly. Having experience with different bulk solids behavior and an understanding of the various contact laws and associated inputs is imperative for the DEM model to predict the flow in the chute.