Computational Fluid Dynamics (CFD) Based Investigations on the Flow of Capsules in Vertical Hydraulic Pipelines

The rapid depletion of power sources has remarkably impacted the transport sector, where the costs of the freight transportation are rising dramatically every year. Significant endeavours have been made to develop innovative means of transport that can be adopted for economic and environmental friendly operating systems. Transport pipelines consider one such alternative mode that can be used to transfer goods. Although the flow behaviour of a solidliquid mixture in hydraulic capsule pipeline is quite complicated, due to its dependence on a large number of geometrical and dynamic parameters, it is still a subject of active research. In addition, published literature is extremely limited in terms of identifying the impacts of the capsules shape on the flow characteristics of pipelines. The shape of these capsules has a significant effect on the hydrodynamic behaviour within such pipelines.

This thesis presents a computational investigation employing advanced Computational Fluid Dynamics (CFD) based tool to simulate the capsules flow of varied shapes quantified in form of a novel shape factor in a vertical hydraulic capsule pipeline. The 3-D Dynamic Meshing technique with Six Degrees of Freedom approach is applied for numerical simulation of unsteady flow fields in vertical capsule pipelines. Variations in flow related parameters within the pipeline have been discussed in detail for geometrical parameters associated with the capsules and flow conditions within Hydraulic Capsule Pipelines (HCPs).

Detailed quantitative and qualitative analyse has been conducted in the current research. The qualitative analysis of the field of the flow comprises descriptions of the pressure and velocity distribution within the pipeline. The investigations have been conducted on the flow of spherical, cylindrical and rectangular shaped capsules each one separately for offshore applications. As it can be notice that the flow behaviour inside HCP relies on the flow conditions and geometric parameters. The development of novel predictive models for pressure drop and capsule velocity is considered as one of the goals that have been achieved in this research. Moreover, the flow of a variety of different shaped capsules, in combination, has also been investigated based on the impact of the order of the capsule shape within the vertical pipeline. It has been found that the motion of mixed capsules along the pipeline shows a significant variation comparing to the basic capsules shapes for the same shape being transported across the pipelines.

Capsule pipeline designers need accurate data regarding the pressure drop, holdup and the shape of the capsules etc., at early design phases. The methodology of optimisation is developed based on the least cost principle for vertical HCPs. The inputs to the predictive models are the shape factor of the capsule and solid throughput demanded of the system, while the outcomes represent the pumping power demanded for the capsule transportation process and the optimal diameter of the HCP.

In the present study, a complete visualisation of capsules flow and design of vertical hydraulic capsule pipelines has been reported. Sophisticated computational tools have allowed the possibility to analyse and map the flow structure in an HCP, which resulted to a deeper comprehension of the flow behaviour and trajectory of the capsules in vertical pipes