Thesis (MTech (Electrical Engineering))--Peninsula Technikon, 2002. / Word processed copy. Summary in English. Includes bibliographical references (leaves 148-149). Also available online.

A scroll vortex intake is a hydraulic structure that transfers water stably from one elevation to a lower one by generating a swirling vortex flow down a vertical drop- shaft. Scroll vortex intakes are applied widely in water supply, stormwater drainage and sewerage systems. For a good engineering design, a sufficiently large and stable air core needs to be maintained within the dropshaft. Although a number of the- oretical and experimental investigations have been conducted, the understanding and predictions of the vortex flow is still far from complete due to a lack of de- tailed velocity field and air core measurements. This study aims to achieve a better understanding of the scroll vortex intake flow. The hydraulic theory of scroll vortex intake is revisited and detailed measurements of air core and velocity field of the vortex flow is conducted. A 1:15 physical model of a scroll vortex intake has been designed according to dynamic Froude similitude and constructed. Experiments have been conducted to measure the head-discharge relation. Piezometric head and air core size are measured at the throat of the vortex flow. Velocity fields are measured using Laser Doppler Anemometry (LDA). The measurements show that the vortex flow in the chamber resembles a free vortex and the circulation is approximately equal to that at the inlet to chamber. The chamber flow is not affected by the bottom boundary effect at bottom above a depth of the order of the dropshaft diameter. The throat section of the vor- tex flow is located slightly below the chamber bottom and within the bellmouth at the entrance to dropshaft. For the vortex flow in and downstream of the bell- mouth, the tangential velocity distribution can be described by a Rankine vortex (combination of forced and free vortex); the transition from forced to free vortex occurs at around the middle of the vortex flow layer. The pressure is positive for all locations and all discharges. Due to viscous effect, the maximum circulation is found to be lower than the inlet circulation. Consistent with the free vortex theory, the vertical velocity in the dropshaft is approximately constant. By accounting for the loss of circulation between chamber inlet and the dropshaft, a new 1D theory is proposed. Unlike previous models, the new theory gives good predictions of head-discharge relation and minimum air core size without the need of physically unrealistic assumptions. This study has revealed the structure of a scroll vortex intake flow for the first time. Characteristic flow features of the scroll vortex intake have been elucidated. The findings have helped to explain and resolve the long-standing discrepancies between the theoretical predictions of three representative 1D hydraulic theories. The vortex flow measurements also provide a basis for the development of a new theory and the validation of 3D numerical models. / published_or_final_version / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil Engineering / Master / Master of Philosophy

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Cloud computing has grown in prevalence from recent years due to its concept of computing as a service, thereby, allowing users to offload the infrastructure management costs and tasks to a cloud provider. Cloud providers leverage server virtualization technology for efficient resource utilization, faster provisioning times, reduced energy consumption, etc. Cloud computing inherits a key feature of server virtualization which is the live migration of virtual machines (VMs). This technique allows transferring of a VM from one host to another with minimal service interruption. However, live migration is a complex process and with a cloud management software used by cloud providers for management, there could be a significant influence on the migration process. This thesis work aims to investigate the complex process of live migration performed by the hypervisor as well as the additional steps involved when a cloud management software or platform is present and form a timeline of these collection of steps or phases. The work also aims to investigate the performance of these phases, in terms of time, when migrating VMs with different sizes and workloads. For this thesis, the Kernel-based Virtual Machine (KVM) hypervisor and the OpenStack cloud software have been considered. The methodology employed is experimental and quantitative. The essence of this work is investigation by network passive measurements. To elaborate, this thesis work performs migrations on physical test-beds and uses measurements to investigate and evaluate the migration process performed by the KVM hypervisor as well as the OpenStack platform deployed on KVM hypervisors. Experiments are designed and conducted based on the objectives to be met. The results of the work primarily include the timeline of the migration phases of both the KVM hypervisor and the OpenStack platform. Results also include the time taken by each migration phase as well as the total migration time and the VM downtime. The results indicate that the total migration time, downtime and few of the phases increase with increase in CPU load and VM size. However, some of the phases do not portray any such trend. It has also been observed that the transfer stage alone does not contribute and influence the total time but every phase of the process has significant influence on the migration process. The conclusions from this work is that although a cloud management software aids in managing the infrastructure, it has notable impact on the migration process carried out by the hypervisor. Moreover, the migration phases and their proportions not only depend on the VM but on the physical environment as well. This thesis work focuses solely on the time factor of each phase. Further evaluation of each phase with respect to its resource utilization can provide better insight into probable optimization opportunities.

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