Abstract
A detailed knowledge of the influence of a particle’s shape on its settling behavior is useful for the prediction and design of separation processes. Models in the available literature usually fit a given function to experimental data. In this work, a constructive and data-driven approach is presented to obtain new drag correlations. To date, the only considered shape parameters are derivatives of the axis lengths and the sphericity. This does not cover all relevant effects, since the process of settling for arbitrarily shaped particles is highly complex. This work extends the list of considered parameters by, e.g., convexity and roundness and evaluates the relevance of each. The aim is to find models describing the drag coefficient and settling velocity, based on this extended set of shape parameters. The data for the investigations are obtained by surface resolved simulations of superellipsoids, applying the homogenized lattice Boltzmann method. To closely study the influence of shape, the particles considered are equal in volume, and therefore cover a range of Reynolds numbers, limited to [9.64, 22.86]. Logistic and polynomial regressions are performed and the quality of the models is investigated with further statistical methods. In addition to the usually studied relation between drag coefficient and Reynolds number, the dependency of the terminal settling velocity on the shape parameters is also investigated. The found models are, with an adjusted coefficient of determination of 0.96 and 0.86, in good agreement with the data, yielding a mean deviation below 5.5% on the training and test dataset.
Highlights
Describing the settling of particles of various shapes is relevant for a wide range of applications
The data for the investigations are obtained by surface resolved simulations of superellipsoids, applying the homogenized lattice Boltzmann method
It can be applied to an enlarged data basis, extending the considered Reynolds numbers
Summary
Describing the settling of particles of various shapes is relevant for a wide range of applications. The particle shape is related to the efficiency of classification processes in hydro cyclones [2]. It is relevant for medical applications: Champion et al [3] identified the shape as being critical to the performance of drug carriers. Waldschläger and Schüttrumpf [4] investigated the velocities of micro-plastic settling and rising—among other things—for different shapes, such as fragments, pellets, and fibers. They found that shapes make a big difference
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