<p>  </p> <p>Metal 3D printing is the industry standard for manufacturing experimental suppressors due to the limitations of conventional, subtractive machining methods. Long print times, difficulty sintering, and cleaning of metal 3D printed suppressor components limit the development time. Plastic printed components are able to be produced quicker, safer, and at a lower cost than their metal 3D printed counterparts. Reducing the time and cost of manufacturing will allow for an increased pace of innovations in suppressor design.</p> <p><br></p> <p>Utilizing Finite Element Analysis (FEA) in combination with Computational Fluid Dynamics (CFD) will expedite the process of designing 3D printed plastic suppressors. Solidworks FEA determined the maximum stress applied to the blast chamber of the plastic suppressor. ANSYS Fluent CFD simulations were used to qualitatively compare the sound pressure levels of an unsuppressed and suppressed 22LR pistol. Comparing the results of the CFD simulations gave insight into the effectiveness of the selected baffle structure.</p> <p><br></p> <p>A prototype 3D printed suppressor was optimized for strength according to manufacturing practices for printed plastic small arms. Testing occurred at an indoor range where peak impulse noise was measured for an unsuppressed 22LR pistol and a plastic printed suppressor. The printed suppressor reduced the small arms impulse noise from 150.5 dB(spl) to 132.4 dB(spl). Impulse noises below the pain threshold of 140 dB(spl) do not require hearing protection for operation. Utilizing FEA, CFD, and FDM prototyping methods in this work has laid the foundation for future works in the rapid prototyping and optimizations of suppressors for small arms.</p>

A frequency response tracer technique was used to study the hydraulic properties of a laboratory flow through reactor with variations in reactor size, flow rate and applied mixing. At any one set of conditions the reactor was studied over a range of input sine wave frequencies. Theoretical models consisting of in-series networks of completely mixed segments, plug flow segments, and dead space allowances were developed to approximate the experimental findings. / Thesis / Master of Engineering (ME)

<p dir="ltr">Precise measurement of the flowrate is crucial for both process control and energy consumption evaluation. The main aim of this work is to develop a methodology to calibrate mechanical flowmeters, designed to measure high viscosity fluids, in water. In order to accomplish this, a series of computational fluid dynamics (CFD) analysis are carried out to determine how the motion of the mechanical component varies with different flow rates of water and high viscosity fluids. This data is recorded and analyzed to develop calibration curves that relate the motion of the mechanical component the flow rates. From the calibration curves, it can be determined the required water flow rate to achieve the equivalent motion of the mechanical component in a specified viscosity. This method provides an efficient and cost-effective calibration process because it eliminates the need for calibrating using heated engine oil to achieve the fluid viscosity of the flow meter is designed. Flowmeter sensitivity analysis was also performed and it was observed that the motion of the mechanical component curves converges as the size of the flowmeter increases suggesting that the effect of viscosity on flowmeter sensitivity decreases as the size of the flowmeter is increased, likely due to reduced resistance to flow and smaller pressure drops. </p><p dir="ltr">The Kanbara Reactor ladle is a commonly used method in the steelmaking industry for hot-metal desulfurization pre-treatment. The impeller's configuration is pivotal to the reactor's performance, yet its precise function remains partially understood. This study introduces a 3-dimensional Volume-of-Fluid (VOF) model integrated with the sliding mesh technique, investigating the influence of five different impeller speeds. After Validating the model through experimental data, this numerical model is applied to investigate the typical developmental phenomena and the consequences of impeller speed variations on fluid flow characteristics, interface profile, and vortex core depth. The findings reveal that the rotational impeller induces a double-recirculation flow pattern in the axial direction due to the centrifugal discharging flow. With increasing impeller rotation speed, the vortex core depth also rises, emphasizing the substantial impact of impeller speed on vortex core depth.</p>

High interstitial fluid pressure (IFP) in tumours is recognized as a barrier to drug delivery resulting in reduced efficacy. High IFP impedes the normal process of convective fluid flow (CFF) from blood vessels into the interstitium. The aim of this study was to develop an in vitro model that could be used to measure CFF and to study its effects on drug delivery. The model consists of a transwell cell culture insert which supports the growth of multicell layers (MCL) on collagen coated membranes. A graduated tube is inserted into the transwell and a pressure gradient is applied across the membrane by raising the volume of medium in the tube above that of the bottom chamber. CFF is determined by measuring the weight of medium in the bottom chamber as a function of time. CFF was inversely proportional to MCL thickness and 41.1±3.6µm thick MCL has completely stopped CFF. Using a physiologically relevant hydrostatic pressure of 28mmHg, a CFF of 21µL/min was recorded using a DLD-1 MCL that was 12.21±3.2µm thick. Under these conditions, the rates of penetration of doxorubicin, imatinib and gefitinib were respectively 42, 26 and 13 folds greater than when no CFF exists. Reversing the CFF so that it opposed the drug diffusion gradient significantly impairs drug penetration. In conclusion, a novel in vitro model for assessing the impact of CFF on drug delivery has been developed. This model could be used to evaluate strategies designed to increase drug delivery to solid tumours by modifying the CFF.

Knochen ist ein lebendes Material, das seine Struktur an die mechanische Umgebung anpasst. Zur strukturellen Anpassung muss der Knochen die mechanische Belastung erfassen. Allerdings sind Knochen mechanisch so steif, dass die lokalen Verformungen zu klein sind um von den Knochenzellen direkt detektiert zu werden. Osteozyten sind Knochenzellen, die ein Zellnetzwerk in der mineralisierten Matrix bilden. Ihre Zellkörper sind in Lakunen untergebracht und ihre Zellprozesse in engen Kanälchen, den Canaliculi. Die Hypothese des Flüssigkeitsflusses besagt, dass der lastinduzierte Flüssigkeitsfluss durch dieses Lakunen-Canaliculi-Netzwerk (LCN) einen Verstärkungsmechanismus bereitstellt, der es den Osteozyten ermöglicht, die dynamische Belastung des Knochens zu erfassen. Wir stellen die Hypothese auf, dass die Architektur des LCN eine wesentliche Rolle in Bezug auf die Mechanosensitivität spielt, da sie den Flüssigkeitsfluss beeinflusst. Das zentrale Ziel dieser Arbeit ist es, diese Hypothese an realen LCN-Architekturen mit einem Modell des lastinduzierten Flüssigkeitsflusses zu testen und den resultierenden Fluss mit der Mechanoreaktion des Knochens zu vergleichen. Wir haben das LCN mithilfe konfokaler Laser-Scanning-Mikroskopie untersucht. Wir haben dann die auf den Kirchhoffschen Gesetzen basierende Schaltungstheorie verwendet, um die Geschwindigkeiten der Flüssigkeit in allen abgebildeten Canaliculi zu modellieren und darzustellen wie sich die verdrängte Flüssigkeit über das LCN verteilen würde. Basierend auf diesen Geschwindigkeiten wurde die Mechanoreaktion des Knochens vorhergesagt. In meiner Studie wurden die Knochen von Mäusen verwendet, wodurch kontrollierte in vivo Belastungsexperimente und die Messung der Mechanoreaktion in Bezug auf gebildeten bzw. resorbierten Knochen unter Verwendung von in vivo µCT möglich waren. Die Flüssigkeitsströmungsmuster durch das LCN korrelierten mit der gemessenen Mechanoreaktion. Das heißt, Knochenbildung wurde in Bereichen nahe höherem Fluss beobachtet, während Knochenabbau in Bereichen nahe geringem Fluss beobachtet wurde. Die Vorhersage der Mechanoreaktion unter Berücksichtigung der Architektur des LCN war quantitativ besser als eine Vorhersage, die nur auf mechanischer Belastung basiert. Qualitativ haben wir festgestellt, dass Gefäßkanäle im Kortex als lokale Senken des Flüssigkeitsflusses fungieren und daher den Fluss an der nahegelegenen Knochenoberfläche reduzieren. Im Gegensatz dazu nahmen die Strömungsgeschwindigkeiten für konvergente Netzwerkstrukturen zu, bei denen die Zahl der Kanäle zur Knochenoberfläche hin abnimmt. In einem zweiten Projekt konzentrierten wir uns auf gesunden, menschlichen osteonalen Knochen. Osteone sind zylindrische Strukturen um Gefäßkanäle, die praktisch vom umgebenden Knochen abgeschottet sind. Wir analysierten acht gewöhnliche Osteone mit einem nahezu homogenen LCN und neun Osteon-in-Osteonen, die durch eine ringartige Zone mit geringer Netzwerkkonnektivität zwischen dem inneren und dem äußeren Teil dieser Osteone gekennzeichnet sind. In Canaliculi, die die beiden Teile des Osteons in Osteonen überbrücken, wurde ein wesentlich höherer lastinduzierter Flüssigkeitsfluss beobachtet als in anderen Canaliculi. Dies führte dazu, dass der durchschnittliche Fluss 2,3-mal höher war als bei normalen Osteonen. Es ist daher wahrscheinlich, dass Osteon-in-Osteon-Konstruktionen besonders zur Mechanosensitivität des kortikalen Knochens beitragen. Die Untersuchungen in dieser Doktorarbeit legen nahe, dass die LCN-Architektur neben der mechanischen Belastung als Schlüsselfaktor für die Knochenanpassung dient. / Bone is a living material, which adapts its structure in response to the mechanical environment. For structural adaptation bone need to sense the mechanical loading. However, bone is so stiff that the local strains are too small to be directly sensed by bone cells. Osteocytes are bone cells that form a cell network located within the mineralized matrix. Their cell bodies are housed in lacunae and their cell processes in narrow canals, the canaliculi. According to the fluid flow hypothesis, load induced fluid flow through this lacunocanalicular network (LCN) provides an amplification mechanism which allows osteocytes to sense dynamic loading of the bone. We hypothesize that the network architecture of the LCN plays an essential role in bone’s mechanosensitivity, as it influences the fluid flow. We aimed to test these hypotheses by using real LCN architectures in a model of load induced fluid flow, and compare the resulting flow with the mechanoresponse of bone. We imaged the LCN using confocal laser scanning microscopy (CLSM). Image processing was then used to describe the LCN as a mathematical network consisting of edges and nodes, representing the canaliculi and their connections respectively. We then employed circuit theory, based on Kirchhoff’s laws, to model the velocities of the fluid in all the imaged canaliculi. Based on these velocities, the mechanoresponse of bone was predicted. Mice were used in my study, as this allowed a controlled in vivo loading and a measurement of the mechanoresponse in terms of formed/resorbed bone using in vivo µCT. Fluid flow patterns through the LCN of mice correlated with the measured mechanoresponse, i.e., bone formation was observed near surfaces of higher flow, while resorption was observed near surfaces with low flow. The prediction of the mechanoresponse considering the architecture of the LCN was quantitatively better than a prediction based on strains only. Qualitatively, we identified that vascular canals in the cortex act as local sinks of fluid flow and, therefore, reduce the flow at the nearby bone surface. In contrast, flow velocities increased in convergent network structures, where the flow is channeled into fewer canaliculi nearby the surface. In a second project we focused on healthy human osteonal bone. Osteons are cylindrical structures around vascular canals, which are practically sealed off from the surrounding bone. We analyzed 8 ordinary osteons with a rather homogeneous LCN, and 9 osteon-in-osteons, which are characterized by a ring-like zone of low network connectivity between the inner and the outer parts of these osteons. A substantially higher load-induced fluid flow was observed in canaliculi that bridge the two parts of the osteon-in-osteons. This resulted in an average flow, which was 2.3 times higher compared to ordinary osteons. It is therefore likely that osteon-in-osteons particularly contribute to the mechanosensitivity of cortical bone. Based on both studies in this PhD thesis we conclude that LCN architecture should be considered as a key determinant of bone adaptation besides mechanical loading.

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Thesis Ph.D. ((Applied Mathematics)) -- University of Limpopo, 2022 / The world is under threat from the devastating effects of the continued depletion of the Ozone layer. Increased global warming is causing catastrophic ecological damage and imbalance due to accelerated melting of glaciers, rampant runaway veld res, widespread floods and other extreme events. The delegates to the Cop26 Climate Change Summit were reminded that the continued burning of fossil fuels is releasing carbon into the atmosphere at an unprecedented pace and scale and that the world is already in trouble. Complete substitution of fossil fuels with clean energy sources is the only solution through which the world can be saved from the deleterious effects of global warming. However, total dependence on renewable energy sources can only be possible through novel technology that enables efficient energy utilization and conservation. For instance, the evolution of advanced techniques in manufacturing processes has led to the reduction in the size of various industrial and engineering designs that consume reduced amounts of energy. Efficient energy utilization in thermo-fluid flow systems can be achieved through entropy generation minimization. Entropy is a thermodynamic quantity that represents the unavailability of a system's thermal energy for conversion into mechanical work. In this study, thermodynamic analysis of reactive variable properties third-grade fluid flow in channels with varied geometries and subjected to different physical effects was investigated with the second law of thermodynamics as the area of focus. Entropy generation and inherent irreversibility analysis were the main focus of the study where the sensitivities of these quantities to the embedded parameters were numerically and graphically described and analysed. The semi-analytic Adomian decomposition method, the semi-implicit fi nite difference scheme and the spectral quasilinearisation method were employed to solve the nonlinear differential equations modelling the flow systems. The results reveal that the effects of the parameters on flow velocity, fluid temperature, entropy generation and inherent irreversibility cannot be neglected. In particular, conditions for entropy generation minimization were successfully established and documented. / University of Limpopo

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A high temperature reactor (HTR) generates heat inside of the reactor core through nuclear fission, from where the heat is transferred through the core and heats up the reactor pressure vessel (RPV). The heat from the RPV is transported passively through the reactor cavity, where it is cooled by the reactor cavity cooling system (RCCS), through the concrete confinement structure and ultimately into the environment. The concrete confinement structure can withstand temperatures of up to 65°C for normal operating conditions and temperatures of up to 125°C during an emergency. This project endeavours to research the heat transfer between an HTR’s RPV and the outside of the concrete confinement structure by utilising three investigative approaches: experimental, computational fluid dynamics (CFD) and analytical. The first approach, an experimental analysis, required the development of an experi- mental model. The model was used to perform experiments and gather temperature data that could be used to verify the accuracy of the CFD simulations. The second approach was a CFD analysis of the experimental model, and the external concrete temperatures from the simulation were compared with the temperatures measured with the experimen- tal model. Finally, an analytical analysis was performed in order to better understand CFD and how CFD solves natural convection-type problems. The experiments were performed successfully and the measurements taken were com- pared with the CFD results. The CFD results are in good agreement with the Dry experiments, but not with the Charged experiments. It was identified that the inaccurate results for the CFD simulations of the Charged experiments arose due to convective heat leakage through gaps in the heat shield and between the heat shield and the sides of the experimental model. A computer program was developed for the analytical analysis and it was established that the program could successfully solve the natural convection in a square cavity - as required. / AFRIKAANSE OPSOMMING: ’n Hoë temperatuur reaktor (HTR) genereer hitte binne die reaktor kern deur kernsplyting en die hitte word dan deur die kern versprei en verhit die reaktor se drukvat. Die hitte van die reaktor drukvat word dan passief deur die reaktorholte versprei, waar dit deur die reaktorholte se verkoelingstelsel afgekoel word, en deur die beton beskermingstruktuur gelei word en uiteindelik die omgewing bereik. Die beton beskermingstruktuur kan temperature van tot 65°C onder normale operasietoestande van die reaktor weerstaan, en temperature van tot 125°C tydens ’n noodgeval. Hierdie projek poog om die hitte-oordrag tussen ’n HTR-reaktor drukvat en die buitekant van die beton beskermingstruktuur te on- dersoek deur gebruik te maak van drie ondersoekbenaderings: eksperimenteel, numeriese vloei dinamika (NVD) en analities. Die eerste benadering, ’n eksperimentele analise, het die ontwikkeling van ’n eksper- imentele model vereis. Die model is gebruik om eksperimente uit te voer en temperatu- urmetings te neem wat gebruik kon word om die akkuraatheid van die NVD simulasies te bevestig. Die tweede benadering was ’n NVD-analise van die eksperimentele model, en die eksterne betontemperature verkry van die simulasies is vergelyk met die gemete temperature van die eksperimente. Uiteindelik is ’n analitiese analise uitgevoer ten einde NVD beter te verstaan en hoe NVD natuurlike konveksie-tipe probleme sal oplos. Die eksperimente is suksesvol uitgevoer en die metings is gebruik om die NVD resultate mee te vergelyk. Die NVD resultate van die Droë eksperimente het goeie akkuraatheid getoon. Dit was nie die geval vir die Gelaaide eksperimente nie. Daar is geïdentifiseer dat die verskille in resultate tussen die NVD en die eksperimente aan natuurlike konveksie hitte verliese deur gapings in die hitteskuld en tussen die hitteskuld en die kante van die eksperimentele model toegeskryf kan word. ’n Rekenaarprogram is geskryf vir die analitiese ontleding en die program kon suksesvol die natuurlike konveksie in ’n vierkantige ruimte oplos.

Three dimensional flow regimes are encountered in many types of industrial flow processes such as filtration, mixing, reaction engineering, polymerization and polymer forming as well as environmental systems. Thus, the analyses of phenomena involved fluid flow are of great importance and have been subject of numerous ongoing research projects. The analysis of these important phenomena can be conducted in laboratory through experiments or simply by using the emerging computational fluid dynamics (CFD) techniques. But when dealing with three dimensional fluid flow problems, the complexities encountered make the analysis via the traditional experimental techniques a daunting task. For this reason, researchers often prefer to use the CFD techniques which with some care taken, often produce accurate and stable results while maintaining cost as low as possible. Many CFD codes have been developed and tested in the past decades and the results have been successful and thus encouraging researchers to develop new codes and/or improve existing codes for the solutions of real world problems. In this present project, CFD techniques are used to simulate the fluid flow phenomena of interest by solving the flow governing equations numerically through the use of a personal computer. The aim of this present research is to develop a robust and reliable technique which includes a novel aspect for the solution of three dimensional generalized Newtonian fluids in domains including obstructions, and this must be done bearing in mind that both accuracy and cost efficiency have to be achieved. To this end, the finite element method (FEM) is chosen as the CFD computational method. There are many existing FEM techniques namely the streamline upwind Petrov-Galerkin methods, the streamline diffusion methods, the Taylor-Galerkin methods, among others. But after a thorough analysis of the physical conditions (geometries, governing equations, boundary conditions, assumptions …) of the fluid flow problems to be solve in this project, the appropriate scheme chosen is the UVWP family of the mixed finite element methods. It is scheme originally developed to solve two dimensional fluid flow problems but since the scheme produced accurate and stable results for two dimensional problems, then attempt is made in this present study to develop a new version of the UVWP scheme for the numerical analysis of three dimensional fluid flow problems. But, after some initial results obtained using the developed three dimensional scheme, investigations were made during the course of this study on how to speed up solutions' convergence without affecting the cost efficiency of the scheme. The outcomes of these investigations yield to the development of a novel scheme named the modified three dimensional UVWP scheme. Thus a computer model based on these two numerical schemes (UVWP and the Modified UVWP) is developed, tested, and validated through some benchmark problems, and then the model is used to solve some complicated tests problems in this study. Results obtained are accurate, and stable, moreover, the cost efficiency of the computer model must be mentioned because all the simulations carried out are done using a simple personal computer.