| Granular flows are important in a wide range of fields, ranging from planetary science to geophysics, and industries such as metallurgy, ceramics, chemicals, food, cosmetics, coal and pharmaceuticals. The manufacturing, processing, and control of granular products depend on a fundamental understanding of the granular flows. The quasi-static, dense (liquid) and fast (gaseous) flow regimes are general granular flow regimes. Of these, the dense granular flow regime is the most complicated, and the one with the least investigation.;The rotating drum is one of the standard experimental systems for studying the dense granular flow regime. In addition, rotating drums have many industrial applications, and are used in a great variety of processes (mixing, size reduction, sintering, coating, heating, cooling, drying, and reaction). To design and operate rotating drums optimally, it is essential to study the phenomena that occur inside such devices on a fundamental level. In industrial operations, rotating drums mainly use the rolling regime, which provides superior solid mixing and heat transfer. Many experimental studies have been conducted to obtain the flow behavior of particles inside a rotating drum, though a majority of them used spherical or nearly spherical particles. However, an investigation of non-spherical particles is very important because natural or crushed particles usually have an irregular shape, non-spherical particles with certain shapes have many usages, and more importantly, particle shape greatly affects the flow behaviour.;Therefore, this work aims to study of the effect of particle shape on flow dynamics. To do so, the cylinder was chosen as the particle shape for two main reasons. Firstly, there are lots of industrial applications for cylindrical particles, such as capsules, candies, biomass pellets, etc. Secondly, to be able to identify the effect of particle shape on flow behaviour, the shape should be readily identified, and distinct from a sphere. The cylinder is one the most basic curvilinear geometric shapes, and many other curvilinear shapes, especially those with a high aspect ratio, can be approximated as a cylinder.;Many nonintrusive techniques have been used to study granular flow in a rotating drum, including optical methods and radioactive techniques. Since particulate matter is principally opaque, optical methods are essentially limited to surface flow. Conversely, radioactive techniques are well suited for providing information about inside the bed in such systems, because gamma rays can penetrate relatively easily through materials. Radioactive particle tracking (RPT) is one suitable measurement techniques for this investigation. However, RPT is limited to tracking the position of a single tracer. As cylindrical particles are used for this study, it is essential to employ a measurement technique capable of simultaneously tracking the position and orientation of a cylindrical particle.;The first part of this thesis introduces a multiple radioactive particle tracking technique (MRPT) that can determine the trajectory of two free or restricted moving tracers in a system (attached to the same particle). The accuracy (<5 mm) and precision (<5 mm) of the proposed technique is evaluated by tracking two stationary tracers and two moving tracers. The results confirm the reliability and validity of the MRPT technique when the two tracers have the same isotope and the distance between them is not too small (>2 cm). The tracking of two sticking tracers at the two ends of a cylindrical particle in a rotating drum is also considered to illustrate the potential of this characterization method.;In the second part of this thesis, we compare the flow behavior of cylindrical (2 cm long and 6 mm in diameter) and spherical (6 mm in diameter) particles using the multiple radioactive particle tracking (MRPT) technique to capture the positions and orientations of cylindrical particles simultaneously. We analyzed two important components of the transverse flow dynamic, namely, the boundary between the active and passive layers and the velocity profile on the free surface, in the rolling regime (7.5-15 RPM for cylindrical particles under the conditions of this study). For the first time, we measured the orientation of cylindrical particles inside the bed. The results confirm the existence of a preferred spatial orientation (about a 25-degree deviation from the dynamic repose angle) for cylindrical particles in the active layer. The results show that the spatial orientation of cylindrical particles within the bed are insensitive to the rotational speed of the drum. Therefore, for cylindrical particles at all rotational speeds, bed dilation was constant (about 25%), while the bed dilation of spherical particles is about 1%. Velocity profiles on the free surface for cylindrical particles show an asymmetrical shape (the peak of velocity profile is located at 70% of the free surface length) while that of spherical particles is symmetrical; (the peak of velocity profile is located at 50% of the free surface length). For the first time, two general models are proposed to calculate the velocity profiles for cylindrical particles on the free surface and the effective particle sizes in the active and passive layers.;Finally, the third part of this thesis presents a further analysis of the data obtained by the MRPT and RPT techniques in the previous part. We obtain the equations of motion for cylindrical and spherical particles in the active and passive layers, as well as equations of the yield and turning point curve lines. Using numerical simulation, the effect of advection on the quality of mixing for both cylindrical and spherical particles is also considered to illustrate the potential use of these equations of motion. |
