Measuring the velocity fields of granular flows – Employment of a multi-pass two-dimensional particle image velocimetry (2D-PIV) approach

• Published in: Advanced powder technology : the international journal of the Society of Powder Technology, Japan Japan, 2018-12, Vol.29 (12), p.3107-3123
• Main Authors: Sarno, L., Carravetta, A., Tai, Y.-C., Martino, R., Papa, M.N., Kuo, C.-Y.
• Format: Article
• Language: English
• Subjects: Correlated velocity; Granular flow; Granular temperature; Particle image velocimetry; PIVlab
• ISSN: 0921-8831; 1568-5527
• DOI: 10.1016/j.apt.2018.08.014

[Display omitted] •The multi-pass PIV approach to granular flows is systematically investigated.•Various granular media and flow geometries are studied by open-source code PIVlab.•The influence of the interrogation windows sizes on PIV estimations is investigated.•The accuracy of velocity and granular temperature estimations is assessed.•Homogeneous guidelines about the most reliable PIV settings emerge from experiments. Measuring velocity fields plays a crucial role in investigating the dynamics of granular flows, which can improve the modeling of hazardous geophysical flows (e.g. avalanches and debris flows) and the control of powder flows in industrial applications. Non-invasive optical methods are invaluable tools for estimating this physical quantity at the laboratory scale. Despite the recent improvements of particle image velocimetry (PIV) algorithms, the employment of PIV to granular flows is still a non-trivial application, where there are several specific aspects to be carefully addressed. Here, we address the main challenges of granular PIV applications and systematically test the open-source window deformation multi-pass code, PIVlab [Thielicke and Stamhuis, J. Open Res. Soft., 2014], for dry granular flows in rotating drum and chute flow experiments. Three granular media (glass spheres, Ottawa sand and acetalic resin beads) with different optical properties are used as a broad test bench for validating the PIV approach. As well, comparisons between the estimations by PIVlab and those obtained by the commercial code, IDT ProVision-XS, are reported, where the advantages of the multi-pass approach are highlighted. This extensive experimental investigation allowed the evaluation of the accuracy of PIVlab in granular flow applications and also helped to assess the reliability of measurements of second-order statistics, such as the granular temperature. Finally, a guideline for setting a reliable PIV arrangement is suggested.