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On-going efforts to reduce aircraft drag through transition delay focus on understanding the process of boundary-layer transition from a physics-based perspective. For swept-wings subject to transition dominated by a stationary crossflow instability, one of the remaining challenges is understanding how freestream disturbances and surface features such as surface roughness create the initial amplitudes for unstable waves. These waves grow, modify the mean flow and create conditions for secondary instabilities to occur, which in turn ultimately lead to transition. Computational methods that model the primary and secondary instability growth can accurately model disturbance evolution as long as appropriate initial conditions are supplied. Additionally, transition delay using discrete roughness arrays that exploit known sensitivities to surface roughness has been demonstrated in flight and wind tunnel testing; however, inconsistencies in performance from the two test platforms indicate further testing is required. This study uses detailed hotwire boundary-layer velocity scans to quantify the relationship between roughness height and initial disturbance amplitude. Naphthalene flow visualization provides insight into how transition changes as a result of roughness height and spacing. Micron-sized, circular roughness elements were applied near the leading edge of the ASU(67)-0315 model installed at an angle of attack of -2.9 degrees in the Klebanoff-Saric Wind Tunnel. Extensive flow quality measurements show turbulence intensities less than 0.02% over the speed range of interest. A survey of multiple roughness heights for the most unstable and control wavelengths and Reynolds numbers of 2.4 x 10⁶ 2.8 x 10⁶ and 3.2 x 10⁶ was completed for chord locations of 10%, 15% and 20%. When care was taken to measure in the region of linear stability, it was found that the disturbance amplitude varies almost linearly with roughness height. Naphthalene flow visualization indicates that moderate changes in already-low freestream turbulence levels can have a significant impact on transition behavior.

Numerical simulations of a three dimensional diamond jet interaction flowfield at various diamond injector half angles into a supersonic crossflow were presented in this thesis. The numerical study was performed to improve the understanding of the flame holding potential by extending the numerical database envelop to include different injector half angles and examine the flow at Mach 2 and Mach 5. The configuration of a diamond injector shape was found to reduce the flow separation upstream, and produce an attached shock at the initial freestream interaction and the injection fluid has an increased field penetration as compared to circular injectors. The CFD studies were also aimed at providing additional information on the uses of multiple injectors for flow control. The numerical runs were performed with diamond injectors at half angles of 10° and 20° at a freestream Mach number of 5. The transverse counter-rotating pair of vortices found in the 15° does not form within the 10° and 20° cases at freestream Mach number 5. The 10° case had a barrel shock that became streamlined in the lateral direction. The 20° barrel shock had a very large spanwise expansion and became streamlined in the transverse direction. In both cases the trailing edge of their barrel shocks did not form the flat “V” shape, as found in the baseline case. At Mach 2 the 10° and 15° cases both formed the flat “V” shape at the trailing edge of the barrel shocks, and formed the transverse counter rotating vortex pairs. The 10° multiple injector case successfully showed the interaction shocks forming into a larger planer shock downstream of the injectors. The swept 15° case produced interaction shocks that were too weak to properly form a planar shock downstream. This planar shock has potential for flow control. Depending on the angle of incidence of the injector fluid with the freestream flow and the half angle of the diamond injector, the planar shocks will form further upstream or downstream of the injector.

<div> <p>Combustion will likely continue to be utilized over the next century to meet the world’s energy needs. As increasingly stringent requirements on emissions, particularly of oxides of nitrogen (NO and NO₂) are imposed on power plants due to their harmful effects on the environment, advanced combustor strategies to limit NO_X productions are needed. One such advanced concept involves axially staging the fuel to create a distributed combustion system. The fundamental problem for staged combustion involves the injection of a reacting jet into crossflow. This canonical problem is modified for this dissertation through injection of a reacting premixed natural gas and air jet into a compressible vitiated crossflow with negligible swirl. In addition, the experimental efforts for this work were conducted at elevated inlet air temperature and combustor pressure.</p><p>The development and performance of a perforated plate burner (PPB) to provide vitiated crossflow and operating using premixed natural gas (NG) and air at engine-relevant conditions is discussed. A significant benefit of using burners with simplified flow fields, such as the PPB, for experimental studies in the laboratory is the potential for decoupling the complex fluid dynamics in typical combustors from the chemical kinetics. The stable operation of the PPB within a high-pressure test rig was validated: successful ignition, effective use of redlines for flashback mitigation, and long duration steady-state operation in both piloted and non-piloted modes were all observed. Exhaust gas emissions measured using a Fourier-transform infrared (FTIR) spectrometer showed very good performance of the PPB in terms of the combustion efficiency and low levels of NO_X<i> </i>in non-piloted operation that were generally within 3 ppm.</p><p>Emissions measurements of the premixed reacting jet in vitiated crossflow were obtained for a variety of conditions and a significant NO_X reduction was achieved when the staged combustor exit Mach number was increased and the axial residence time was decreased. Based on this preliminary investigation, a test matrix was developed to independently vary the exit Mach number for a constant axial residence time by using modular rig hardware to change the length of the axial combustor. Up to 70% reduction in NO_X produced by the axial stage was observed when the combustor exit Mach number was increased from about 0.26 to 0.66 at a constant residence time of 1.4 ms. NO_X reduction based on variation in the Mach number and at a constant residence time has not been previously reported in the literature to the best of our knowledge. This decrease in NO_X is hypothesized to be due to the lower static temperature of a compressible flow and potentially better mixing of the jet with the crossflow due to the interaction occurring at high speeds.</p><p>Based on the strong effect of Mach number for NO_X reduction even at a constant residence time, further investigation using laser-based diagnostics is needed to provide insight on physical processes controlling this phenomenon. An optically-accessible secondary combustion zone was developed and fabricated to study the flame position and structure of reacting jets injected into a high-speed vitiated crossflow. The windowed combustor was capable of long-duration, steady-state operation despite a trifecta of: elevated pressures, high combustion gas temperatures, and high-speed reacting flows. High-speed imaging using OH* and CH* chemiluminescence was used to validate operation of the optically-accessible secondary combustion zone.</p><p>High-repetition-rate (1 – 10 kHz) planar laser-induced fluorescence (PLIF) imaging of OH and CH were performed on both premixed NG-air reacting jets and premixed NG-hydrogen-air reacting jets to investigate the flame structure of the reacting jet within a high-speed crossflow. OH-PLIF was performed in the A-X electronic system using excitation at near 283 nm in the (vʹ = 1, v″ = 0) band and near 311 nm in the (vʹ = 0, v″ = 0) band. The crossflow velocity and equivalence ratio were observed to have a strong impact on the stabilization of the reacting jet flame. Additional insight on the stabilization mechanism was obtained using 50 kHz OH* chemiluminescence imaging. CH-PLIF was performed in the C-X electronic system using R-branch excitation near 311 nm in the (vʹ = 0, v″= 0) band. The CH-PLIF images indicated local stoichiometric regions near the leeward side of jet injection and in regions where significant interaction of the fuel rich jet with the vitiated crossflow is expected. In addition, the CH-PLIF images showed evidence of broken, thickened, non-premixed reaction layers.<br></p></div>

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The laminar-to-turbulent transition process in swept-wing boundary layers is often dominated by an inflectional instability arising from crossflow. It is now known that freestream turbulence and surface roughness are two of the key disturbance sources in the crossflow instability problem. Recent experimental findings have suggested that freestream turbulence of low intensity (less than 0.2%) may have a larger influence on crossflow instability than was previously thought. The present work involves experimental measurement of stationary and traveling crossflow mode amplitudes in freestream turbulence levels between 0.02% and 0.2%. A 1.83 m chord, 45-degree swept-wing model is used in the Klebanoff-Saric Wind Tunnel to perform these experiments. The turbulence intensity and length scales are documented. Although a significant amount of research on the role of turbulence has been completed at higher turbulence levels, comparatively little has been done at the low levels of the present experiments, which more closely reflect the flight environment. It is found that growth of the traveling crossflow mode is highly dependent on small changes to the freestream turbulence. Additionally, previously studied attenuation of saturated stationary disturbance amplitudes is observed at these low turbulence levels. The extent of laminar flow is also observed to decrease in moderate freestream turbulence.

Very High Temperature Rector (VHTR) had been designated as one of those promising reactors for the Next Generation (IV) Nuclear Plant (NGNP). For a prismatic core VHTR, one of the most crucial design considerations is the bypass flow and crossflow effect. The bypass flow occurs when the coolant flow into gaps between fuel blocks. These gaps are formed as a result of carbon expansion and shrinkage induced by radiations and manufacturing and installation errors. Hot spots may appear in the core if the large portion of the coolant flows into bypass gaps instead of coolant channels in which the cooling efficiency is much higher. A preliminary three dimensional steady-state CFD analysis was performed with commercial code STARCCM+ 6.04 to investigate the bypass flow and crossflow phenomenon in the prismatic VHTR core. The k-ε turbulence model was selected because of its robustness and low computational cost with respect to a decent accuracy for varied flow patterns. The wall treatment used in the present work is two-layer all y+ wall treatment to blend the wall laws to estimate the shear stress. Uniform mass flow rate was chose as the inlet condition and the outlet condition was zero gauge pressure outlet. Grid independence study was performed and the results indicated that the discrepancy of the solution due to the mesh density was within 2% of the bypass flow fraction. The computational results showed that the bypass flow fraction was around 12%. Furthermore, the presence of the crossflow gap resulted in a up to 28% reduction of the coolant in the bypass flow gap while mass flow rate of coolant in coolant channels increased by around 5%. The pressure drop at the inlet due to the sudden contraction in area could be around 1kpa while the value was about 180 Pa around the crossflow gap region. The error analysis was also performed to evaluate the accumulated errors from the process of discretization and iteration. It was found that the total error was around 4% and the variation for the bypass flow fraction was within 1%.

AbstractThis thesis is the final part of the Innovation and Design Engineering Programme (180 ECTS credits)at the Faculty of Health, Nature and Engineering Science at Karlstad University. The extent of thisthesis is 22.5 ECTS credits and has been performed independently by Hannes Jernberg during thespring of 2013. Metso Paper Karlstad AB is the task maker of this project, and Arvid Johansson is thecompany Representative. Metso Paper Karlstad AB is one of the world leading developer andmanufacturer of tissue paper machines.In the current situation, the company has developed and patented a power management systembased on a Cross Flow Turbine. The current construction is limited to a paper width of 2.9 meters.The company wants to take advantage of all the opportunities provided by the patents, to develop aturbine solution paper machine with a paper width that is wider than 5.5 meters, and give the abilityto manufacture paper for lower energy consumption which is an important part of the production asit is very energy intensive.Problems arise with the increasing length of the turbine, ultimately resulting in that the deflectionbecomes too big and that the momentums, due to the increased torque the turbine blades breaks.By applying the design process, this work has resulted in a number of potential solutions to theproblem. Sketches, LEGO and engineering methodologies have contributed to the good result.The recommended solution generated by this project is to place two regular sized turbines by 2.9meters. The first turbine is placed in its optimal position at the Driver side of the turbine, themomentum provided by the water is leaded by a shaft towards the engine side of the machine. Thesecond turbine is placed directly under the first shaft. This allows the second turbine take care of therest of the water and energy. / SammanfattningDetta examensarbete är en del av innovation - och designingenjörsprogrammet vid Fakulteten förhälsa, natur- och teknikvetenskap vid Karlstads universitet. Omfattningen av detta arbete är 22,5högskolepoäng och har utförts självständigt av Hannes Jernberg under våren 2013. Uppdragsgivarentill detta arbete var Arvid Johansson vid Metso Paper Karlstad AB. Metso Paper Karlstad AB varvärldsledande utvecklare och tillverkare av tissue pappersmaskiner.I dagsläget har företaget utvecklat och patenterat ett energisparsystem med en Cross-flow turbinbegränsad till pappersmaskiner med en pappersbanbredd på ungefär 2,9meter. Företaget vill tatillvara på alla möjligheter som patentet ger, samt utveckla en turbinlösning till pappersmaskinermed en pappersbana som är bredare än 5,5 meter. Vilket i sin tur ger möjligheten att tillverka pappertill lägre energiförbrukning, vilket är en viktig del av en process som är mycket energikrävande.Problem uppstår med den ökande turbinlängden, förlängningen resulterar i att nedböjningen blir förstor samt att vridningen på grund av det ökande momentet vid kraftuttaget får turbinbladen attbrista.Genom att tillämpa designprocessen har detta arbete resulterat i ett flertal potentiella lösningar tillproblemet. Skisser, kreativt användande av LEGO och ingenjörsmässig metodik har bidragit till ettgott resultat.Lösningen som rekommenderas av detta arbete är att placera ut två redan optimerade turbiner medseparata axlar av originalmåttet 2,9 meter i olika nivåer i vattenstrålens plan detta möjliggör enöverlappning som bidrar till ett maximalt tillvaratagande av vattenstrålen.

This work is concerned with an alternative method for metal ion removal from aqueous solutions - surfactant enhanced ultrafiltration. Surfactant monomers aggregate above a certain concentration, specific to the surfactant, to form micelles. Anionic surfactant micelles will attract and bind metal cations. Free metal ions and surfactant monomers pass freely through an ultrafiltration membrane, but if the micelle-metal ion complex is sufficiently large it is rejected. Research reported in this thesis has been carried out on well defined aqueous solutions containing only one type of metal ion together with the natural surfactant lecithin. Lecithin is a food grade by-product of the soybean processing industry and it was chosen because it is non-toxic, biodegradable, abundant and inexpensive. It has a high molecular weight of about 750 Daltons and forms large size micelles. The main aim was to identify the basic mechanisms which influence the permeate flux and rejection levels of the process. The project was carried out in three stages. Stage one was the characterisation of the feed solution which included the determination of the critical micelle concentration using surface tension measurements, measurement of micelle size and zeta potential using a Malvern zeta sizer and visualisation of the micelle shape using scanning electron microscopy of freeze fractured lecithin solution droplet. In the second stage filtration experiments were carried out at a wide range of lecithin concentrations, metal ion concentrations and operating conditions. The experiments were run for 5 hours, by which stage a steady state condition was reached in all cases. Permeate samples were taken after I, 3 and 5 hours. Permeate flux was monitored throughout the experiment. The following properties were monitored for the feed solution at the beginning and the end of each experiment and for all permeate samples: lecithin concentration, copper concentration, pH, conductivity. In the 3 stage Electron Dispersive Analysis by X-ray (EDAX), Scanning Electron Microscopy (SEM) and a X-ray Photoelectron Spectrum Technique (XPS) were employed to investigate any membrane feed solution interactions. The results of the 3 stages were used to identify the basic mechanisms which control the permeate flux levels and the extent of component rejection in lecithin enhanced ultrafiltration.