Nesta pesquisa é apresentado um estudo do escoamento turbulento formado pela interação de “bluff-body” com o fluxo principal (ar). Os “bluff-bodies” estudados possuem a forma de um disco, cone e cilindro. A zona de recirculação formada por esta interação possibilita a aplicação de “bluff-body” como estabilizador mecânico de chama. Aplicando vários modelos de turbulência foram feitas simulações computacionais para analisar a formação da zona de recirculação do fluxo de ar em relação à forma do estabilizador de chama (disco, cone e cilindro), sua dimensão (grau de bloqueamento do canal) e velocidade de escoamento. Para escolher o modelo de turbulência que descreve melhor o comportamento do fluxo em escoamento turbulento com “bluff-body” foi feita uma comparação entre os dados experimentais e os obtidos computacionalmente. O modelo de turbulência K-Epsilon mostrou maior conformidade com os dados experimentais em comparação com os outros modelos aplicados. / 92 f.

This thesis involves the experimental testing of a bluff body with a blunt base to evaluate the effectiveness of end-plate tabs in reducing drag. The bluff body is fitted with interchangeable end plates; one plate is flush with the rest of the exterior and the other plate has small tabs protruding perpendicularly into the flow. The body is tested in the Cal Poly 3ft x 4ft low speed wind tunnel. Testing is conducted in three phases. The first phase was the hot-wire measurement of streamwise velocity of the near wake behind the bluff body. An IFA300 thermal anemometry system with a hot-wire probe placed behind the model measures the wake velocity fluctuations. The power spectral density on the model without tabs shows large spikes at Strouhal numbers of 0.266, 0.300, and 0.287 at corresponding Re = 41,400, 82,800, 124,200 where vortex shedding occurs. The model with tabs shows no such peaks in power and therefore has attenuated vortex generation in the wake flow at that location. The second phase of testing was pressure testing the model through the use of pressure ports on the exterior of the bluff body. A Scanivalve pressure transducer measured multiple ports almost simultaneously through tubing that was connected to the model internally and routed through the model’s strut mount and outside of the wind tunnel. This pressure testing shows that the model with tabs is able to achieve up to 36% increase in Cp at Reh = 41,400 on the base region of the bluff body and no negative pressure spikes that occur as a result of vortex shedding. The last phase of testing is the measurement of total drag on the model through a sting balance mount. This testing shows that the drag on the model is reduced by 14% at Re = 41,400. However it also shows that as velocity increased, the drag reduction is reduced and ultimately negated at Re = 124,200 with no drag loss at all. The addition of tabs as a passive flow control device did eliminate vortex shedding and alter the base pressure of the bluff body. This particular model however showed no reduction in total drag on the model at high Reynolds numbers higher than 124,000. Further study is necessary to isolate the exact geometry and flow velocities that should be able to produce more favorable drag results for a bluff body with this type of passive flow control device.

Rivers create beautiful patterns and provide drinking water to millions. However an alarming number of rivers in the US and globally are threatened by excess sediment and nutrients. Agricultural rivers draining erodible soils are particularly vulnerable. Rivers of southern Minnesota provide a unique opportunity to study water and sediment dynamics in a naturally vulnerable system. Sediment reduction strategies are needed to ensure biological integrity and adequate water quality. Here, I address the questions: 1) have climate, land use practices, or both affected streamflows in Midwest agricultural rivers?, 2) which streamflows set the rate of river bluff erosion?, and 3) how do sediment supply and transport influence the form and behavior of the lower Minnesota River? Chapter 2 demonstrates, in three agricultural basins, that artificial drainage practices have decreased soil moisture, contributing to increases in streamflow. Chapter 3 quantifies river bluff erosion and identifies erosion by streamflows as the dominant erosion process. Erosion by common floods accomplishes the most cumulative bluff erosion. Bluff erosion contributes sediment to the Minnesota River. Chapter 4 shows how this coarse sediment influences the form and behavior of the Minnesota River. Therefore if flows were reduced, bluff erosion would slow, and the supply sediment to the Minnesota would slow, leading to less streambank erosion. Since streamflows have been increased by agricultural drainage practices, water retention solutions are needed to reduce high flows.

The relationship between distinctive characteristic fluid-flow regimes and the sound radiation generated by them has been investigated, over a range of Reynolds numbers, for various single plates and two-plate arrays in nominally two-dimensional flows. In preliminary experiments, the characteristics of flow over single plates with rectangular cross-section and faired leading edges and over tandem arrays of an upstream plate with rectangular cross-section and faired leading edges and a downstream plate of rectangular cross-section were investigated, together with the sound radiation produced. However, the main investigation has been concentrated on single plates of rectangular cross-section with various chord-to-thickness ratios C and on arrays of two plates of rectangular cross-section in tandem having various chord-to-thickness ratios C₁ and C₂ and a range of gaps (with gap-to-thickness ratios G) between them. The range of Reynolds number based on plate thickness t and free-stream velocity U, Re[subscript]t = Ut/ν (where ν is the kinematic viscosity of fluid) covered in the measurements is 3.2 x 10[superscript]3 ≤ Re[subscript]t 53 x 10[superscript]3. Spectra of velocity fluctuations in the flow and radiated sound have been measured and their characteristic frequencies related. An attempt has been made to measure force fluctuations on surfaces of the plates in order to relate them to flow characteristics and radiated sound power. Mean and fluctuating pressures associated with the force fluctuations on the plates have also been obtained. The lengths of separation bubbles on long rectangular plates have also been determined. In most cases, the measurements have been complemented by flow-visualisation in a water tunnel to provide additional detailed insight into the flow patterns. Three flow regimes have been identified for single plates of rectangular cross-section. In the first regime (1 ≤ C ≤ 3.13), shear layers separated from the leading edges form a vortex street downstream of the plate without reattachment to it. Associated force fluctuations on the plate are the main source of acoustic radiation. In the second regime (3.05 ≤ C ≤ 9.65), the separated shear layers reattach intermittently to the streamwise plate surfaces. Vortex formation in the shear layer is the dominant cause of sound radiation but the effect becomes weaker as C increases. In the third regime (6.52 ≤ C ≤ 68), the separated shear layers form closed leading-edge separation bubbles. Weak vortex shedding, with only a small contribution to the sound radiation, occurs only at the trailing edges of the plate. Bistable behaviour of the flow over a plate, with random switching between the regimes, occurs for C ≈ 3 and 6.52 ≤ C ≤ 9.65. A proposed classification of possible flow regimes for the flow around two plates of rectangular cross-section in tandem has been confirmed experimentally. For small G, the flow in the gap between the plates is isolated from the external flow. When the gap G between the plates is increased to or beyond a critical value (between 2 and 3.5), the shear layers separated from the upstream plate form a von Karman vortex street in the gap before interacting with the downstream plate. Flow and acoustic measurements indicate that this transition is associated with dramatic changes in the flow character. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1320474 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2008

Bakgrund: Kinesiska bolag på den amerikanska OTC-listan är idag ofta associerade med bluffar och dålig kommunikation gentemot aktieägarna. Detta gör att den amerikanska marknaden inte har ett förtroende för dessa bolag. Denna opålitlighet från marknadens sida har resulterat i att många av de kinesiska bolagen blivit felvärderade. För de legitima bolagen leder det till att de blir undervärderade. Frågan som uppstår här är: Kan ett bolag få en mer rättvis värdering genom att noteras på en marknadsplats utanför USA exempelvis i Sverige? Syfte: Denna studie har till syfte att undersöka hur en övergång för ett kinesiskt bolag från en OTC-lista i USA till en senior lista på den reglerade börsmarknaden i Sverige påverkar värderingen av bolaget. Genomförande: Studien är utformad till en kvantitativ undersökning. Uträkningar görs i Excel utifrån den insamlade datan. De uträkningarna som görs är främst matematiska och statistiska tester/metoder där de uträknade resultaten ska ligga till grund för analyserna som ska göras utifrån de finansiella teorierna; behavioural finance och effektiva marknadshypotesen. Slutsats: Studien visar att det finns fördelar för de kinesiska bolagen med att noteras på den svenska marknaden då den inte har samma erfarenheter som den amerikanska marknaden, dock kommer det att kräva en förbättrad kommunikation och en högre kontroll av de kinesiska bolagen. Denna anpassning kan bli ett problem för bolagen då det skulle kräva ett helt nytt arbetssätt som de inte är vana vid. Om bolagen tar sig ann utmaningen så kan det leda till en positiv tillväxt samt flera investerare och en mer rättvis värdering. / Background: Chinese companies on the U.S. OTC market are today often associated with fraud and bad communication against the investor. This means that the U.S. market does not have confidence in these companies. This unreliability is making these companies mispriced in the majority of cases, for the legitimate companies this will lead them to becoming underpriced. The question that arises here is: Can a company get a more fair valuation by getting listed on a marketplace outside of the U.S. e.g. in Sweden? Purpose: This study aims to investigate how a transition for a Chinese company from an OTC list in the U.S. to a senior listing on the regulated stock market in Sweden will affect the valuation of the company. Method: The study is designed to a quantitative survey. Calculations are made in Excel from the data collected. The calculations made ​​are mathematical and statistical tests where the calculated results will form the analysis that will be made on the basis of the financial theories; behavioral finance and the efficient market hypothesis. Findings: The study shows that there are advantages for Chinese companies to be listed on the Swedish market since it does not have the same experience as the U.S. market, however, it will require a new type of communication and greater control of the Chinese companies. This adaptation can be a problem for companies as it would require an entirely new work approach that they are not used to. If companies are able to make these changes it could lead to positive growth, additional investors and a more fair valuation.

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The facies architecture and geometry of stratigraphic surfaces within a lignite bearing interval of the Paleocene upper Calvert Bluff Formation is mapped on a photomosaic of the 150 ft (50 m) high and 12,000 ft (4km) long “C” area highwall of Big Brown Mine, near Fairfield, Texas. Observed bedding and facies architecture are interpreted in terms of temporal changes, depositional environments and sequence stratigraphic setting. A three dimensional grid of 89 subsurface logs is correlated to this photomosaic to characterize log response patterns of facies. Six facies are observed: 1) lignite, 2) interdistributary bay mud, 3) prograding delta, 4) delta top mud, 5) distributary channels, and 6) incised valley fill. The six facies were defined by a combination of mapped photomosaic observations and subsurface log correlations. The lignite deposit formed in a low depositional energy, low sediment input, high-organic productivity interchannel basin. Overlying mud records overbank flooding followed by avulsion and progradation of delta deposits. Tidal-flat deposits overlying prograding delta deposits record fluctuating energy conditions on the emerging delta top. Channel deposits cutting into the delta top record lateral channel migration across delta top floodplains. These regressive delta deposits are capped by a local incised sequence boundary overlain by fluvial channel deposits inferred to have allowed sediment to bypass further basinward during lowstand. A sheet of channel deposits capping this highwall exposure records more recent erosion, followed by development of modern soil horizons. The Big Brown Mine highwall exposes a relatively complete high-frequency Paleocene stratigraphic sequence developed in an area landward of the shoreline position during maximum transgression, that progresses upsection from: 1) highstand alluvial flood basin coals, 2) a thin condensed maximum flooding interdistributary shale, 3) a thick succession of regressive deltaic strata, and 4) a high-relief, sequence-bounding erosion surface overlain by a lowstand to transgressive fill of channel deposits. Correlations with regional Wilcox Group stratigraphic studies spanning coeval shoreline and shelf strata indicate that this high-frequency sequence is within the transgressive systems tract of a 3rd order stratigraphic sequence. It appears that high-frequency sequences of sub-regional extent control the complex distribution of coal seams within central Texas.

Denna studie grundar sig i den splittring som PR-konsulten befinner sig i, gällande de många etiska ställningstaganden som denne ställs inför. Detta i kombination med, att public relations som yrke ännu inte betraktas som en erkänd profession, gör att PR-branschen blir utsatt för intrång på dess område från övriga kommunikationsbranschen. Intresset för studien väcktes i samband med den intensiva mediebevakningen runt PR-konsulternas användande av bluff-PR och det sken som bluff-PR kastar över PR-branschen. Studien grundar sig i den fragmentering som idag präglar PR-branschen, gällande vikten av förtroende och etiska värderingar, samt den inverkan som bluff-PR har på yrkesverksamma PR-konsulter. I det här sammanhanget ses bluff-PR, som en PR-kampanj för att skapa nyfikenhet kring något utan att vara tydlig med avsändaren, för att vid ett senare skede avslöja vad det egentligen handlar om. Studiens syfte och frågeställningar är besvarade med hjälp av en kvalitativ metod; samtalsintervjuer. Yrkesverksamma PR-konsulter i Sverige, samtliga medlemmar i PRECIS, bjöds inledningsvis in att delta i vår studie. Resultatet som presenteras i studien är baserat på genomförda intervjuer med dessa PR-konsulter. Resultatet visar att PR-konsulterna befinner sig mitt i en pågående branschglidning som kommit att möjliggöra för andra att praktisera PR-konsultens ursprungliga uppgift. Samt att branschglidningen i sin tur möjliggjort för framväxten av bluff-PR. Därefter pekar resultatet på att den personliga etiken är den mest framstående gällande hur PR-konsulten resonerar kring sin yrkesroll. Respondenterna tror dock inte att användandet av bluff-PR kommit att förändra de förtroende som de inger i sin yrkesroll.

Syftet med denna uppsats är att svara på frågan hur läsare och media reagerade på bloggen Black Ascot i egenskap av en litterär bluff, även kallad en litterär fabrikation. Målet är även att komma fram till hur mottagare av textbaserad kommunikation reagerar på att bli lurade. För att uppnå syftet undersöks läsarnas och medias reception av Black Ascot. Uppsatsen diskuterar även om det finns förklaringar till receptionen i bloggens litterära utformning. I analyserna framkommer det att diskussioner gällande framförallt autenticitet och moral uppstod såväl i media som bland läsarkommentarerna. Trots att negativa reaktioner förekommer i båda undersökningsgrupperna tyder resultatet på att en majoritet av bloggläsarna uppskattade bloggen även som en litterär fabrikation. Enligt uppsatsen beror detta bland annat på bloggens tematik och dess intentionsambivalens.

Bluff body stabilization of flames is a commonly employed technique for combustion applications, such as thrust augmentors. These combustors are usually required to operate at lean conditions governed by a lower stability limit on combustion denoted by lean blow off. Lean blow off is believed to be a dynamically unstable phenomenon that leads to flame extinction or convection from a stable, usually desired, point in space. Current theories predict lean blow off based on models that were developed over specific domain of inflow parameters. This thesis sought to compile, re-evaulate, and analyze past blowoff data presented in literature using time scale correlations, Damkohler numbers, by employing modern chemical kinetic solvers to approximate characteristic chemical times. The research has conclusively shown that it is possible to express blowoff data for multiple flow conditions using a power law relationship between Damkohler number and Reynolds numbers. From the analysis of this power law relations, trends are validated using past empirical observations, and some new information regarding flame stability is also conveyed.