Unsteady aerodynamics using high-order methods

Unsteady flows occur in many applications of engineering interest. One category of unsteady flows occur as self-sustaining oscillatory fluid motion, such as the flow over rectangular cavities. There has been a significant amount of research performed on this topic over the years, both experimentally and numerically. The unsteady flow over rectangular cavities is the case study in this research. In this work, a generic numerical solver is developed and written to predict the near-field aerodynamics of unsteady fluid motions at low Mach numbers. High order numerical schemes are employed to this effect. The Detached Eddy Simulation (DES) method is considered for the turbulence modelling part. At the start of this project, the combination of high order Computational Aeroacoustics (CAA) numerical schemes, non-reflecting boundary conditions and DES constituted a state of the art approach to the simulation of unsteady compressible flow phenomena at low Mach numbers. In the numerical study of 2D cavities, a number of cases with different length-to depth (L/D) ratios were considered. Under the same flow conditions, the relation of the L/D to the radiated sound in the farfield is sought. It is found that the nature of the flow interaction with the downstream corner, which changes with L/D, dictates the directivity and amplitude of the sound field observed at a far distance from the source. To gain more insight into the topology of 3D cavity flows, an experimental study using non-intrusive measurement techniques is outlined. This explains the work performed on 3D cavities with different spanwise dimensions. A detailed flow visualisation of the meanflow patterns in various measurements planes describes the presence of strong 3D features. In particular, the symmetrical flow behaviours at relatively large width-to-depth (W/D) ratios of 3 and 2 are highlighted. This provides the justification to employ a symmetry condition in the 3D DES study. Therefore, the final case study is based on the numerical simulation of a 3D cavity geometry where only half of the cavity is simulated. The observations from the 2D simulations and the experimental work provided a basis of the expectations of this test case. Again, a correlation between the near-field aerodynamics and the farfield sound is sought. The 3D cavity showed (as in the 2D cases) a preferred directivity in the farfield

Pyrolysis yields from refinery residue using a batch process

Batch pyrolysis has proved to be a valuable process of assessing the potential of recovering and characterizing valuable products from various materials. Furthermore, the off-gases produced are easily handled by conventional gas clean-up processes in order to achieve environmental emission compliance. This research explores the pyrolysis of hydrocarbon rich refinery residues, left over from crude oil and other crude fraction conversion processes, in a 1200 liter electrically-heated batch retort. It also provides the novel offering of a cost effective and environmentally compliant method of assessing the recovery potential of valuable products. The process design has been formulated by careful consideration of key aspects of previous work cited in literature. The pyrolysis of the residue has shown significant oil (70%), char (14%) and non-condensable gas (6% by difference) yields. The oil yield obtained shows a remarkably high calorific value (~40MJ/kg), comparable to that of standard liquid fuels. The char obtained, with high carbon content (~80%), could be a candidate for a solid fuel source. The non-condensable gas stream possesses significant calorific value (240KJ/mol, estimated) implying the potential generation of an additional heating source. The non-condensable gas stream was subjected to an oxidative process prior to gas clean-up, and continuous on-line monitoring of the vented gas demonstrated compliance with South African emission guidelines. The gas treatment is economically optimal as only a smaller portion of the original residue is subjected to emission-controlling steps. The current work is aimed at a semi-commercial batch pyrolysis plant which generates substantial quantities of material for the purposes of proving compliance with emission standard regulations

Multispecies colonisation and surface erosion on A106 GB industry-finished steel used in heat exchangers

DATA AVAILABILITY STATEMENT : Data will be made available upon request through the corresponding author and/or the director of the project, Prof. Evans Chirwa (Email: [email protected]).Multispecies bacterial attachment to carbon steel surfaces is not fully understood; for example, as to why the attachment of certain bacteria influences corrosion. In this study, finished steel, A 106 GB was exposed to a mixed bacterial culture in a batch reactor system at a constant temperature of 35 °C to evaluate the corrosion rate with and without bacterial influence. Cultures collected from the cooling tower site were exposed to coupons and were grown in a batch reactor. Atomic force microscopy (AFM) was used to obtain roughness parameters. Surface morphology and colonisation patterns were observed by scanning electron microscopy (SEM). 16S rDNA sequencing indicated predominance of Pseudomonas sp. and Clostridium sp. on the rough surfaces. Cell colonisation of surfaces showed no time-related differences, with differences observed on surface roughness parameters. Intergranular and uniform corrosion was observed. The smooth finished steel surface performed best in resisting corrosion.Te National Research Fund (NRF) of South Africa.http://www.tandfonline.com/loi/tbeq20hj2024Chemical EngineeringPhysicsSDG-09: Industry, innovation and infrastructur

The interaction of organisational trust on the relationship between entrepreneurial leadership and developing a corporate entrepreneurial environment.

Organisational trust has shown to have a net positive effect on innovation however limited research exists on the interaction effect of organisational trust between entrepreneurial leadership and developing a corporate entrepreneurial environment. The quantitative cross-sectional research study was conducted on sample population (N=393) within the technical and engineering operational business unit of a large petrochemical organisation. Statistical analysis was conducted on the N=71 responses to confirm reliability, validity, ability to be factorised and thereafter regression analysis to test the hypotheses. The results of the statistical analysis confirm a positive relationship between organisational trust and entrepreneurial leadership, organisational trust and a corporate entrepreneurial environment, and, entrepreneurial leadership and a corporate entrepreneurial environment. The interaction variable did not prove statistically significant and a corporate entrepreneurial environment could not be proved to predict entrepreneurial leadership. The research findings confirm the positive meta-cognitive effect of organisational trust on entrepreneurial leadership and a corporate entrepreneurial environment. Due to the low response rate the research cannot be regarded as generalisable.Mini Dissertation (MBA)--University of Pretoria, 2021.zl22Gordon Institute of Business Science (GIBS)MBAUnrestricte

Yields from pyrolysis of refinery residue using a batch process

Batch pyrolysis was a valuable process of assessing the potential of recovering and characterising products from hazardous waste materials. This research explored the pyrolysis of hydrocarbon-rich refinery residue, from crude oil processes, in a 1200 L electrically-heated batch retort. Furthermore, the off-gases produced were easily processed in compliance with existing regulatory emission standards. The methodology offers a novel, cost-effective and environmentally compliant method of assessing recovery potential of valuable products. The pyrolysis experiments yielded significant oil (70%) with high calorific value (40 MJ/kg), char (14%) with carbon content over 80% and non-condensable gas (6%) with significant calorific value (240 kJ/mol). The final gas stream was subjected to an oxidative clean-up process with continuous on-line monitoring demonstrating compliance with South African emission standards. The gas treatment was overall economically optimal as only a smaller portion of the original residue was subjected to emission-controlling steps. Keywords: Batch pyrolysis, Volatiles, Oil yields, Char, Emissions, Oil recover

Multispecies colonisation and surface erosion on A106 GB industry-finished steel used in heat exchangers

Multispecies bacterial attachment to carbon steel surfaces is not fully understood; for example, as to why the attachment of certain bacteria influences corrosion. In this study, finished steel, A 106 GB was exposed to a mixed bacterial culture in a batch reactor system at a constant temperature of 35 °C to evaluate the corrosion rate with and without bacterial influence. Cultures collected from the cooling tower site were exposed to coupons and were grown in a batch reactor. Atomic force microscopy (AFM) was used to obtain roughness parameters. Surface morphology and colonisation patterns were observed by scanning electron microscopy (SEM). 16S rDNA sequencing indicated predominance of Pseudomonas sp. and Clostridium sp. on the rough surfaces. Cell colonisation of surfaces showed no time-related differences, with differences observed on surface roughness parameters. Intergranular and uniform corrosion was observed. The smooth finished steel surface performed best in resisting corrosion.</p