The impact phenomena of high velocity micron-size particles, although commonly considered and described as detrimental in numerous engineering applications, can be used in a beneficial way if properly understood and controlled. The Cold Gas Dynamic Spray (CGDS) process, known as a surface modification, repair and additive manufacturing process, relies on such high velocity impacts. In the process, solid particles are accelerated by a supersonic gas flow to velocities up to 1200 m/s and are simultaneously heated to temperatures lower than their melting point. When propelled under proper velocity and temperature, the particles can bond onto a target surface. This bonding is caused by the resulting interfacial deformation processes occurring at the contact interface. Hence, the process relies heavily on the gas/particle and particle/substrate interactions. Although numerous experimental and/or numerical studies have been performed to describe the phenomena occurring during particle flight and impact in the CGDS process, numerous phenomena remain poorly understood. First, the effect of substrate surface topographical condition on the particle deformation and ability to successfully adhere, i.e. atomically and/or mechanically, has not been thoroughly investigated such that its influence is not well understood. Another aspect of the process that is generating the largest gap between experimental and numerical studies in the field is the lack of particle in-flight temperature measurements. Obtaining such data has proven to be technically difficult. The challenges stem from the short particle flight time, low particle temperature and small particle size preventing the use of established thermal spray pyrometry equipment. Relatedly, lack of such measurements precludes a proper experimental study of the impact related phenomena at the particle/substrate interface. As a result, the effect of particle size dependent temperature on overall coating properties and atomic bonding relies currently on estimates. Finally, the effect of particle impact characteristics on interfacial phenomena, i.e. grain size and geometry, velocity/temperature, and oxide scale thickness, on adhesion and deformation upon single particle collision has also been scarcely studied for soft particle depositions on hard substrate. Hence, the current research work aims at studying fundamental aspects of particle/gas heat transfer and particle/substrate impact features in goals to improve the understanding of the CGDS process. Different surface preparation methods will be used to create various surface roughness and topographical features, to provide a clear understanding of the target surface state influence on coating formation and adhesion. Additionally, new equipment relying on novel technology, i.e. high-speed IR camera, will be utilized to obtain particle in-flight temperature readings with sequence recordings. Subsequently, the experimental particle in-flight temperature readings will be used to develop a computational fluid dynamics model in goals to validate currently used Nusselt number correlations and heat transfer equations. The particle size-dependent temperature effect on the particle’s elastic and plastic response to its impact with a targeted surface and its ability to successfully bond and form a coating will be studied experimentally. A thorough CFD numerical work, based on experimental findings, will be included to provide full impact characteristics (velocity, temperature, size and trajectory) of successfully deposited particles. Finally, the numerical results will be utilized in the ensuing study to correlate single particle deformation, adhesion and interfacial features to impact characteristics. A finite element model will be included to investigate the effect of particle size dependent temperature on single particle interfacial pressure, temperature and bonding ability.

No description available.

La déflection statique d'une structure flexible exposée à un écoulement transverse permet classiquement de réduire la traînée à laquelle elle est soumise. Dans le domaine de la biomécanique, la déformation induite par l'écoulement d'éléments végétaux flexibles conduisant à une réduction du chargement est désignée par le terme `reconfiguration' pour souligner le caractère avantageux de ce processus adaptatif. Dans cette thèse, nous examinons les mécanismes qui sous-tendent le processus de reconfiguration, dans des systèmes fluide-structure présentant une variabilité spatiale, ou de la dynamique provenant au choix de l'instationnarité de l'écoulement de base, d'un couplage fluide-structure conduisant à une instabilité, ou de vibrations induites par vortex. Nous montrons que l'aptitude des structures flexibles à réduire l'intensité du chargement imposé par l'écoulement est preservée en présence de non-uniformités ou de dynamique, à condition que le design de la structure soit tel que la traînée résistive domine les forces inertiels. Nous montrons de plus que la capacité à se déformer présente l'avantage supplémentaire de permettre la réduction des vibrations induites par vortex. Notre travail indique également que des structures légères et élancées sont les mieux adaptées pour supporter les chargements induits par l'écoulement en se reconfigurant, et que l'efficacité de la réduction du chargement par reconfiguration élastique dépend faiblement de la distribution spatiale des propriétés du système. Finalement, la réduction des chargements résulte toujours, indépendamment du régime de reconfiguration, de la concentration de la déformation sur une longueur caractéristique inférieure à la longueur réelle de la structure. / The static deflection of a flexible structure exposed to a transverse flow is classically known to reduce the drag it has to withstand. In the field of biomechanics, the flow-induced deformation of flexible plant elements leading to a reduction of the loads is referred to as `reconfiguration', in order to highlight the alleged benefits of such adaptive process. In this thesis, we investigate the mechanisms underpinning the reconfiguration in flow-structure systems featuring some spatial variability, or some dynamics arising either from the unsteadiness of the free-stream, from a flow-structure coupling leading to an instability, or from vortex-induced vibrations. We show that the ability of flexible structures to reduce the magnitude of the flow-induced loads is preserved in the presence of non-uniformities or dynamics, provided that the design of the structure is such that resistive drag dominates over inertial forces. We also show that the ability to deform has the added benefit of reducing the magnitude of the vortex-induced vibrations. Our work further indicates that light, slender structures are better suited to accommodate the flow-induced loads by reconfiguring, and that the efficiency of the process of load reduction by elastic reconfiguration is weakly sensitive to the spatial distribution of the system properties. Finally, regardless of the regime of reconfiguration, the reduction of the load always results from the concentration of the deformation on a characteristic bending length smaller than the actual length of the structure.

Indiana University-Purdue University Indianapolis (IUPUI) / Acquired Immunodeficiency Syndrome (AIDS), as it would later be known, began to appear in the United States in 1981. Medical professionals from around the country began to track a mysterious set of illnesses that were affecting previously healthy people, most of who were homosexual men. As the disease spread, it was clear that homosexual men were being most affected. There was no cure to this illness which was quickly killing those infected. In October 1981, the Indianapolis Bag Ladies, a group of gay men, began as a simple Halloween Bus Tour around the city. Coby Palmer, Gary Johnson, and Ed Walsh teamed up by renting three charter busses for their new “Bag Ladies Bus.” Their campy drag involved multiple costume changes that required them to tote bags around, thus earning their name. By 1982, the Bag Ladies knew they needed to do more than have a party. The second bus tour was all about collecting money and creating a “war chest” for the gay community of Indianapolis in case AIDS made its way to the city. In doing this, they became one of the first grassroots HIV/AIDS support groups in the United States. After over 38 years of continued efforts, the Indianapolis Bag Ladies have impacted the Indianapolis LGBTQ communities through a variety of programs that expanded beyond the original bus tour. This thesis explores and analyzes these efforts which include Nurse Safe Sexx, a safe sex campaign; the Damien Center, a HIV/AIDS health clinic; and the Buddy House and Buddy Support Program, two programs connecting people with AIDS to support programs. The final chapter of this thesis expands on the discussion through a public program hosted by the Indiana Historical Society and demonstrates how programs surrounding these topics can be successful for museums and participants.

No description available.

I denna uppsats undersöks vilka språkattityder som kan synliggöras i recensioner av de tre böckerna Till vår ära (2001), Ett öga rött (2003) och Yani (2022), som samtliga är skrivna helt eller delvis på multietniskt ungdomsspråk. Syftet är att analysera hur attityder till multietniskt ungdomsspråk har förändrats sedan början av 2000-talet fram till 2022. Arbetet vilar på centrala begrepp från sociolingvistiken och en kombination av verktyg för att analysera interpersonella drag i en text. Dessa analysverktyg är hämtade från den systemisk-funktionella grammatiken samt teori för metakommunikation och utgör tillsammans uppsatsens metod. De frågeställningar jag avser besvara är vilka attityder till multietniskt ungdomsspråk som kan blottläggas i bokrecensionerna, och hur dessa attityder har förändrats under tidsperioden 2001–2022. Resultaten visar att det har skett en förändring i attityder under den studerade tidsperioden. Det går från en uppfattning om att multietniskt ungdomsspråk visserligen är nyskapande och normbrytande men ändå inkorrekt, ofullständigt och svårläst, till övervägande positiva attityder där språket menas fylla en funktion i boken, och fokus förskjuts mer till läsaren än till språket i sig. Detta kan tänkas höra ihop med en större demografisk förändring i samhället där antalet utlandsfödda ökar, och det multietniska ungdomsspråket inte längre är lika ifrågasatt. Samtidigt framgår det att recensenterna sitter på en position där de kan förhandla om språkets plats i samhället utifrån sin roll som kulturella grindvaktare. Undersökningen visar även att en kombination av metoder från systemisk-funktionell grammatik och metakommunikation fungerar väl för att synliggöra attityder i ett material.

It is important to understand the aerodynamic properties of tensioned cables (e.g. used in suspension bridges and yacht riggings), both for drag reduction and vibrational suppression purposes. In this study, the cross-sectional shape and surface structure of solid cables were investigated in order to improve the performance of sailing racing yachts. The apparent wind angle range 15-60° was identified as the most important for drag reduction. Thereafter, the aerodynamic properties of different shapes and surfaces were investigated in the Reynolds number range 5 x 10^3 ≤ Re ≤ 4 x 10^4, by performing computational fluid dynamics simulations and wind tunnel tests (the aerodynamic forces were measured using load cells). No significant effect of changing the surface roughness could be found for the investigated Reynolds number range. The results were compared to literature values for validation. Elliptical shapes with a fineness ratio between 1:1-3:1, together with three complex shapes, were tested. It could be shown that the largest performance gain was obtained for cables with more sail-like aerodynamic properties (for apparent wind angles below 90° a large lift/drag ratio is sought). This study was performed in collaboration with Carbo-Link AG, as an outlook, the manufacturability of carbon fiber reinforced polymer cables in the most aerodynamically efficient shape was explored.

No description available.

<p> Integrating solar energy into the electric vehicle (EV) market alleviates the demand for</p> <p>fossil fuels used to generate the electricity used to power these vehicles. Integrated solar panels</p> <p>provide a new method of power generation for an electric vehicle, but researchers must consider</p> <p>new dependent variables such as drag in the figure of vehicle efficiency. For the solar array to be</p> <p>deemed a viable option for power generation, the solar array must generate enough energy to</p> <p>overcome the added weight and aerodynamic drag forces the solar system introduces. The thesis</p> <p>explores the application of photovoltaic modules for power generation in an EV system.</p> <p>Researchers installed an off-the-shelf solar module on the roof of an EV and investigated the</p> <p>system to explore the efficiency tradeoffs. The research sought to identify an optimized solar</p> <p>panel configuration for minimized drag based on maximized panel surface irradiance, cooling,</p> <p>and array output voltage parameters. The study utilized computational fluid dynamics modeling,</p> <p>wind tunnel testing, and full-scale track testing to analyze the system. The results of this study</p> <p>provide an optimized configuration for a Renogy RNG-100D atop a Chevrolet Bolt. The system</p> <p>was considered optimal at a tilt angle of zero degrees when in motion. The performance benefits</p> <p>due to the increased angle of the solar panel tilt were deemed insufficient in overcoming the</p> <p>aerodynamic drag forces introduced into the system while in motion.</p>

As the need for highly efficient transmission systems increase, it is imperative to have lower fuel consumption levels. Hence, it becomes crucial to investigate and understand reasons behind various losses occurring within the system. Clutches and gears contribute to the major losses within a transmission system. In this thesis project, the drag losses in disengaged wet clutch is studied and efforts have been made to come up with solutions to reduce these losses. Computational Fluid Dynamics (CFD) is used as tool to understand the oil flow in the clutch system. The thesis tasks focused on: - Better understanding of flow physics and oil inlet to the clutch pack - Design and analysis of groove patterns to reduce drag loss - Understand the effect of rotation of clutch discs on groove functionality - Development of a multiphase CFD model with realistic boundary conditions for clutch analysis Initially, the entire clutch pack is modelled to study the oil flow and estimate the amount of oil that is being pumped into the individual gaps between the steel plates and friction discs. To analyze different groove patterns, the clutch model was simplified and only the gap having higher mass flow rate has been considered for simulation. A background study has been done to understand the effect of different clutch parameters on drag losses. Based on the understanding from the literature study, two groove patterns- inclined grooves and waffle grooves have been designed and analyzed in this thesis work. A simplified model with periodic boundary condition and a complete single disc model have been set up and simulated to compare the two groove patterns. To reduce the computational time, at first, a periodic model is set up for groove study. Due to numerical instability observed in the results obtained by using model with periodic boundary condition, the complete single disc model is used for further groove study and comparison. To understand the effect of rotation on grooves, two models have been set up, one with stationary grooves and the other with rotating grooves. While performing the simulations, the temperature and the oil properties have been considered constant. As there were no test results available, the CFD results could not be validated. Convective heat transfer coefficient is estimated to compare the cooling effect of different grooves. An optimal groove pattern would be the one that dissipates oil faster and efficiently out of the clutch pack, and at the same time has better cooling effect. From the results obtained, the inclined grooves were more efficient than waffle grooves in dissipating oil and reducing drag losses. On the other hand, waffle grooves have higher convective heat transfer coefficient when compared to inclined grooves and are better for cooling. / På grund av de ökande kraven på transmissionssystemen är det av stort intresse att även öka deras verkningsgrad för att uppnå lägre bränsleförbrukning. Det blir då viktigt att förstå orsakerna bakom de förluster som uppstår inom systemet. Kopplingar och växlar bidrar till de största förlusterna inom ett transmissionssystem. I denna avhandling studeras strömningsförlusterna i en frånkopplad våtkoppling och försök görs att hitta lösningar för att minska dessa förluster. Computational Fluid Dynamics (numeriska flödesberäkningar) används som ett verktyg för att förstå oljeflödet i kopplingssystemet. Avhandlingens fokus ligger på följande områden: - Förbättra förståelsen för flödesfysik och oljetillförsel till kopplingspaketet - Design och analys av spårmönster för att minska strömningsförluster - Förstå effekten av kopplingsskivornas rotation på spårens funktion - Utveckling av en flerfas CFD-modell med realistiska randvillkor för kopplingsanalys Först modelleras hela kopplingspaketet för att studera oljeflödet och beräkna mängden olja som pumpas in i mellanrummen mellan stålplattorna och friktionsskivorna. För att analysera olika spårmönster förenklades kopplingsmodellen och endast det mellanrum med högst massflödeshastighet har beaktats för simulering. En bakgrundsstudie har gjorts för att förstå effekten av olika parametrar på strömningsförlusterna. Baserat på förståelsen från litteraturstudien har två spårmönster – lutande spår och våffelspår, utformats och analyserats i detta arbete. En nedskalad periodisk modell och en komplett enkelskivsmodell har skapats och simulerats för att jämföra de två spårmönstren. För att minska beräkningstiderna för simuleringarna, användes en periodisk modell för spårgeometristudien. På grund av numerisk instabilitet som observerades i resultaten från den periodiska modellen används den kompletta enkla skivmodellen för ytterligare analys och jämförelse. För att förstå rotationseffekten på spåren har två modeller upprättats, en med stationära spår och en med roterande spår. Under simuleringen har temperaturen och oljeegenskaperna antagits vara konstanta. Eftersom det inte fanns några testresultat tillgängliga kunde CFD-resultaten inte verifieras. Den konvektiva värmeöverföringskoefficienten uppskattades för att kunna jämföra hur kylförmågan påverkas av olika spårgeometrier.  Ett optimalt spårmönster bör utformas sådant att det minskar förlusterna genom att skingra oljan snabbt och effektivt i hela kopplingspaketet, och samtidigt ger en bättre kylningseffekt. Enligt de erhållna resultaten var de lutande spåren effektivare än våffelspår i att skingra olja och reducera strömningsförluster. Å andra sidan ger spår med våffelmönster en högre konvektiv värmeöverföringskoefficient jämfört med lutande spår och därmed förbättrad kylförmåga.