Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (MS)--University of Montana, 2007. / "Major Subject: Geology" Title from author supplied metadata. Contents viewed on November 11, 2009. Includes bibliographical references.

Thesis (M.S.E.)--University of Delaware, 2008. / Principal faculty advisor: James T. Kirby, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2017. / Space limitation in ships and the complex pipe layouts in chemical, mineral and food processing plants lead to the employment of closely spaced bends. The limited information regarding the head loss coefficient of pipe bends orientated as bend-spacer-bend has led pipeline designers to treat them as isolated bends with the same loss coefficient. Thus, to calculate the head loss in the piping system would simply involve summing the head loss coefficient of bends and neglecting their configuration. This practice causes inaccurate computation of head losses in the system. In this study a computational model is developed for the head loss coefficient of closely spaced pipe bends. This is then supported by experimental verification. A more accurate but still simple and easy to use empirical correlation is derived. The empirical correlation is established and the data presented under isothermal conditions for turbulent flows in a range 7.3x104 ≤ Re ≤ 5.8x105 and a spacing ratio of 1D ≤ L/d ≤ 10Dand curvature ratio of 3 ≤ rc/d ≤ 5. Using ANSYS® CFX® 11, a commercial computational fluid dynamics (CFD) package, the fluid domain representing two 900 smooth pipe bends separated by a short pipe was solved and the mechanisms causing the head loss coefficient were explored by using the CFD results to visualise the fluid flow structure/pattern. The computational model was validated by comparing the head loss coefficient of a single bend and the model was found to be sound. The experiments conducted in the built test facility using smooth pipes showed similarities in the trends between the CFD work and the published data and they were to be found have a similar trend. The experiment had shown results that agree to the findings from literature.

No description available.

M.Ing. / It is well known that all flow meters in common use are sensitive to the structure of the flow as it approaches the meter. A flow conditioner is a device installed upstream of for instance a flow meter to remove swirl and correct a distorted flow profile. Many flow conditioners are used in aviation, and in the mining and chemical industry and in the environment every year all over the world. Considerable research has been done on different flow conditioners. In the design and analysis of a flow conditioner, it is vital to have a proper understanding of its fluid mechanical properties. Recent work with computational fluid dynamics (CFD) method has shown that this technique can help to improve flow conditioner technology. The aim of this dissertation is to determine how the different parameters effect the flow performance of the perforated plate and attempt to modify the design. Nine different designs have been simulated by the CFD methodology and have been studied experimentally as well at a specific Reynolds number of 16000. The results obtained show that a different overall porosity can effect the performance of the plate when the other factors are kept constant; the thickness of plate is also a considerable factor for a perforated plate; and the difference in geometry is an important factor for the perforated plate conditioner.

Gas turbine combustion chambers were traditionally designed through trial and error which was unfortunately a time-consuming and expensive process. The development of computers, however, contributed a great deal to the development of combustion chambers, enabling one to model such systems more accurately in less time. Traditionally, preliminary combustor designs were conducted with the use of one-dimensional codes to assist in the prediction of flow distributions and pressure losses across the combustion chamber mainly due to their rapid execution times and ease of use. The results are generally used as boundary conditions in three- dimensional models to predict the internal flow field of the combustor. More recent studies solve the entire flow field from prediffuser to combustor exit. This approach is, however, a computationally expensive procedure and can only be used if adequate computer resources are available. The purpose of this study is two-fold; (1) to develop a one-dimensional incompressible code, incorporating an empirical-based combustion model, to assist a one-dimensional network solver in predicting flow- and temperature distributions, as well as pressure losses. This is done due to the lack of a combustion model in the network solver that was used. An incompressible solution of flow splits, pressure losses, and temperature distributions is also obtained and compared with the compressible solution obtained by the network solver; (2) to utilise the data, obtained from the network solver, as boundary conditions to a three-dimensional numerical model to investigate possible modifications to the dome wall of a standard T56 combustion chamber. A numerical base case model is validated against experimental exit temperature data, and based upon that comparison, the remaining numerical models are compared with the numerical base case. The effect of the modification on the dome wall temperature is therefore apparent when the modified numerical model is compared with the numerical base case. A second empirical code was developed to design the geometry of axial straight vane swirlers with different swirl angles. To maintain overall engine efficiency, the pressure loss that was determined from the network analysis, of the base case model, is used during the design of the different swirlers. The pressure loss across the modified combustion chamber will therefore remain similar to that of the original design. Hence, to maintain a constant pressure loss across the modified combustion chambers, the network solver is used to determine how many existing hole features should be closed for the pressure loss to remain similar. The hole features are closed, virtually, in such a manner as not to influence the equivalence ratio in each zone significantly, therefore maintaining combustion performance similar to that of the original design. Although the equivalence ratios in each combustion zone will be more or less unaffected, the addition of a swirler will influence the emission levels obtained from the system due to enhanced air-fuel mixing. A purely numerical parametric analysis was conducted to investigate the influence of different swirler geometries on the dome wall temperature while maintaining an acceptable exit temperature distribution. The data is compared against the data obtained from an experimentally validated base case model. The investigation concerns the replacement of the existing splash-cooling devices on the dome wall with that of a single swirler. A number of swirler parameters such as blade angle, mass flow rate, and number of blades were varied during the study, investigating its influence on the dome wall temperature distribution. Results showed that the swirlers with approximately the same mass flow as the existing splash-cooling devices had almost no impact on the dome wall temperatures but maintained the exit temperature profile. An investigation of swirlers with an increased mass flow rate was also done and results showed that these swirlers had a better impact on the dome wall temperatures. However, due to the increased mass flow rate, stable combustion is not guaranteed since the air/fuel ratio in the primary combustion zone was altered. The conclusion that was drawn from the study, was that by simply adding an axial air swirler might reduce high-temperature gradients on the dome but will not guarantee stable combustion during off-design operating conditions. Therefore, a complete new hole layout design might be necessary to ensure good combustion performance across a wide operating range. / Dissertation (MEng (Mechanical))--University of Pretoria, 2008. / Mechanical and Aeronautical Engineering / MEng / unrestricted

Airborne dust and methane are common problems in the underground coalmines. They pose health and safety risk to mining personnel, and a safety risk to mining equipment as well. In order to prevent these risks air borne dust and methane concentrations must be reduced to within the acceptable levels. In South Africa, the dust and methane concentration in coalmines should not exceed 2.0 mg/m³ and 0.5% per volume, respectively. Mine ventilation is one of the popular ways of controlling both dust and methane. Different ventilation systems have been designed since the history of underground coal mining. Unfortunately, none provides ultimate solution to the dust and methane problem, especially in the most critical areas of the underground coalmine, like blind-end of the heading and last through road. By changing airflow patterns and air velocity, it is possible to obtain an optimum ventilation design that can keep dust and methane within the acceptable levels. Since it is very difficult to conduct experiments in the underground coalmine due to harsh environmental conditions and tight production schedules, the designer made use of the Computational Fluid Dynamics (CFD) modelling technique. The models were then experimentally verified and validated using a scaled down model at University of Pretoria. After verification further numerical analysis was done to in order to device a method for determining optimum fan positions for different heading dimensions. This study proves that CFD can be used to model ventilation system of a scaled down coalmine model. Therefore chances that this might be true for the actual mine are very high but it needs to be investigated. If this is found to be true then CFD modelling will be a very useful tool in coalmine ventilation system research and development. / Dissertation (MSc)--University of Pretoria, 2011. / Mechanical and Aeronautical Engineering / unrestricted

Computational Fluid Dynamics (CFD) are used to investigate two speech phenomena. The first phenomenon is the English bilabial plosive /pa/. Simulations are compared with microphone recordings and high speed video recordings to study the penetration rate and strength of the jet associated with the plosive /pa/. It is found that the dynamics in the first 10ms of the plosive are critical to penetration rate, and the static simulation was not able to capture this effect. However, the simulation is able to replicate the penetration rate after the initial 10ms. The second speech phenomenon is the English fricative /sh/. Here, the goal is to simulate the sound created during /sh/ to understand the flow mechanisms involved with the creation of this sound and to investigate the simulation design required to predict the sound adequately. A variety of simulation methods are tested, and the results are compared with previously published experimental results. It is found that all Reynolds-Averaged Navier-Stokes (RANS) simulations give bad results, and 2D Large Eddy Simulations (LES) also have poor results. The 3D LES simulations show the most promise, but still do not produce a closely matching spectra. It is found that the acoustic analogy matches the direct measurements fairly well in 3D simulations. The studies of /pa/ and /sh/ are compared and contrasted with each other. From the findings of the studies, and using theoretical considerations, arguments are made concerning which CFD methods are appropriate for speech research. The two studies are also considered for their direct applications to the field and future research directions which might be followed. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

No description available.