Optical Diagnostics of the Motion of Spherical, Cylindrical and Irregularly Shaped Particles within variable Flow Media
Creators: Kinsale, Lisa K
Publisher: name: University of Alberta Library
Year: 2023

<p>The shape of non-spherical or irregularly shaped particles have been a challenging factor to include in mathematical models that describe particle motion in a fluid. In many studies in the literature, irregularly shaped particles have been modelled essentially as spheres. This thesis is an experimental study that investigates the hypothesis that using the spherical assumption to model non-spherical or irregularly shaped particles is invalid. The optical diagnostic technique that was used to evaluate the particle motion is particle shadowgraph velocimetry (PSV). The objectives of this research was to: (1) determine an appropriate length scale to define the particle Reynolds number and coefficient of drag of long aspect ratio particles, (2) identify the important aspects of particle motion in an industrial application known as steam assisted gravity drainage (SAGD), (3) highlight the impact of particle shape and rotation on particle deposition and build-up in SAGD operations. <br>
A commonly used correlation in the literature to determine the coefficient of drag of non-spherical particles is the Haider and Levenspiel model. This is a generalized model that has been often used as a reference or starting point for other empirical correlations that have been developed in the literature. The Haider and Levenspiel model utilizes the equivalent diameter, which is a method of modelling non-spherical particles with respect to a perfect sphere. In this research, experiments were undertaken to investigate the suitability of using the equivalent diameter as a length scale for long aspect ratio particles. A guillotine chopper was used to manufacture cylindrical particles from opaque, black, constant diameter mono-filament. Spherical particles of various sizes and densities were also included in the analysis. The terminal settling velocity of particles used in the Haider and Levenspiel model were determined by estimating the ratio of the average distance travelled by the particle to the average time of travel. However, in this research, a custom image processing technique was used to track the particles and calculate the localized velocities in order to identify when the particles reached the terminal settling velocity. The results showed that the ratio of the volume to the surface area of the particle is a more suitable length scale to define the particle Reynolds number and coefficient of drag for long aspect ratio particles in comparison to using the equivalent diameter.<br>
One of the industrial applications in which particle motion is relevant is SAGD operations. SAGD is a method that is used to extract and produce oil sands. Particle deposition is one of the failure mechanisms of downhole equipment that is used in SAGD operations. The general approach in the literature to analyze particle transport during SAGD operations is a bulk type approach known as ‘core flooding’. In this process, particle transport is analyzed by injecting fluid into a rock sample known as a core and then evaluating the effluent. Therefore, the localized impact of particle motion is unknown. This study seeks to demonstrate the effect of the localized motion of the particles during SAGD by evaluating the motion of both spherical and irregularly shaped particles. The results showed that particle rotation of micro-sized particles can lead to particle deposition and build-up, affecting the flow field of the surrounding fluid. It was also observed that particle rotation depends on particle shape, the initial orientation and the relative location of the particles within the flow field. This study shows that the core flooding approach is inadequate to capture significant aspects of particle motion such as rotation and deposition in SAGD operations. <br>
The thesis shows that long aspect ratio cylindrical particles falling in the direction of gravity within a fluid media can be well modeled as spheres using the ratio of the volume to the surface area of the particles as a length scale. This was observed because a more complete non-dimensionalization of the particle Reynolds number and the coefficient of drag was achieved as the experimental spherical and non-spherical data overlapped well with the predictive model. However, in more complex flow geometries in which a co-flow is introduced, the spherical assumption neglects some important aspects of particle motion. As the results showed, particle shape and rotation can lead to deposition and build-up, which is one of the failure mechanisms in SAGD operations. </p>