<p>The purpose of air distribution systems for HVAC is tocreate proper air quality and thermal conditions in an occupiedzone. In mixing type air distribution systems air is suppliedinto a room through various types of outlets and distributed byturbulent air jets. These air jets are the primary factorsaffecting room air motion. The ASHRAE handbook recognises fourmajor zones of maximum velocity decay along a jet.</p><p>Although numerous theoretical and experimental studies havebeen conducted to develop turbulent air jet theory from the1930's, air jet performance in the further field from theoutlet is still not well understood.</p><p>Many studies were therefore carried out, and the followingconclusions can be drawn from them:</p><p>    The end centerline velocities of zone 3 for both "free"jet and wall jet could strongly depend on the outletvelocities and room size.</p><p>    The<i>K</i>-value of wall jets could be a function of bothoutlet velocities and outlet size.</p><p>    It is very important to choose suitable sampling time toevaluate jet performance.</p><p>    CFD can not always be used to predict jet behaviour,especially for the jet with low outlet velocity and in thearea far away from the outlet. However, for a two-dimensionwall jet, CFD could be a powerful tool for designers.</p><p><b>KEYWORDS</b>: air jet, centerline velocity,<i>K</i>-velocity, air diffuser, ventilation, measurement,CFD</p>

<p>With the present drive in turbomachine engine developmenttowards thinner and lighter bladings, closer spaced blade rowsand higher aerodynamic loads per blade row and blade, advanceddesign criteria and accurate prediction methods for vibrationalproblems such as forced response become increasingly importantin order to be able to address and avoid fatigue failures ofthe machine early in the design process. The present worksupports both the search for applicable design criteria and thedevelopment of advanced prediction methods for forced responsein transonic turbine stages. It is aimed at a betterunderstanding of the unsteady aerodynamic mechanisms thatgovern forced response in transonic turbine stages and furtherdevelopment of numerical methods for rotor stator interactionpredictions.</p><p>The investigation of the unsteady aerodynamic excitationmechanisms is based on numerical predictions of thethree-dimensional unsteady flow field in representative testturbine stages. It is conducted in three successive steps. Thefirst step is a documentation of the pressure perturbations onthe blade surface and the distortion sources in the bladepassage. This is performed in a phenomenological manner so thatthe observed pressure perturbations are related to thedistortion phenomena that are present in the blade passage. Thesecond step is the definition of applicable measures toquantify the pressure perturbation strength on the bladesurface. In the third step, the pressure perturbations areintegrated along the blade arc to obtain the dynamic bladeforce. The study comprises an investigation of operationvariations and addresses radial forcing variations. With thehelp of this bottom-up approach the basic forcing mechanisms oftransonic turbine stages are established and potential routesto control the aerodynamic forcing are presented.</p><p>For the computation of rotor stator interaction aerodynamicsfor stages with arbitrary pitch ratios a new numerical methodhas been developed, validated and demonstrated on a transonicturbine test stage. The method, which solves the unsteadythree-dimensional Euler equations, is formulated in thefour-dimensional time-space domain and the derivation of themethod is general such that both phase lagged boundaryconditions and moving grids are considered. Time-inclination isutilised to account for unequal pitchwise periodicity bydistributing time co-ordinates at grid nodes such that thephase lagged boundary conditions can be employed. The method isdemonstrated in a comparative study on a transonic turbinestage with a nominal non integer blade count ratio and anadjusted blade count ratio with a scaled rotor geometry. Thepredictions show significant differences in the blade pressureperturbation signal of the second vane passing frequency, whichwould motivate the application of the new method for rotorstator predictions with non-integer blade count ratios.</p>

<p>In order to eliminate or reduce vibration problems inturbomachines without a high increase in the complexity of thevibratory behavior, the adjacent airfoils around the wheel areoften mechanically connected together with lacing wires, tip orpart-span shrouds in a number of identical sectors. Although anaerodynamic stabilizing effect of tying airfoils together ingroups on the whole cascade is indicated by numerical andexperimental studies, for some operating conditions suchsectored vane cascade can still remain unstable.</p><p>The goal of the present work is to investigate thepossibilities of a sectored vane cascade to undergoself-excited vibrations or flutter. The presented method forpredicting the aerodynamic response of a sectored vane cascadeis based on the aerodynamic work influence coefficientrepresentation of freestanding blade cascade. The sectored vaneanalysis assumes that the vibration frequency is the same forall blades in the sectored vane, while the vibration amplitudesand mode shapes can be different for each individual blade inthe sector. Additionally, the vibration frequency as well asthe amplitudes and mode shapes are supposed to be known.</p><p>The aerodynamic analysis of freestanding blade cascade isperformed with twodimensional inviscid linearized flow model.As far as feasible the study is supported by non-linear flowmodel analysis as well as by performing comparisons againstavailable experimental data in order to minimize theuncertainties of the numerical modeling on the physicalconclusions of the study.</p><p>As has been shown for the freestanding low-pressure turbineblade, the blade mode shape gives an important contributioninto the aerodynamic stability of the cascade. During thepreliminary design, it has been recommended to take intoaccount the mode shape as well rather than only reducedfrequency. In the present work further investigation using foursignificantly different turbine geometries makes these findingsmore general, independent from the low-pressure turbine bladegeometry. The investigation also continues towards a sectoredvane cascade. A parametrical analysis summarizing the effect ofthe reduced frequency and real sector mode shape is carried outfor a low-pressure sectored vane cascade for differentvibration amplitude distributions between the airfoils in thesector as well as different numbers of the airfoils in thesector. Critical (towards flutter) reduced frequency maps areprovided for torsion- and bending-dominated sectored vane modeshapes. Utilizing such maps at the early design stages helps toimprove the aerodynamic stability of low-pressure sectoredvanes.</p><p>A special emphasis in the present work is put on theimportance for the chosen unsteady inviscid flow model to bewell-posed during numerical calculations. The necessity for thecorrect simulation of the far-field boundary conditions indefining the stability margin of the blade rows isdemonstrated. Existing and new-developed boundary conditionsare described. It is shown that the result of numerical flowcalculations is dependent more on the quality of boundaryconditions, and less on the physical extension of thecomputational domain. Keywords: Turbomachinery, Aerodynamics,Unsteady CFD, Design, Flutter, Low-Pressure Turbine, Blade ModeShape, Critical Reduced Frequency, Sectored Vane Mode Shape,Vibration Amplitude Distribution, Far-field 2D Non-ReflectingBoundary Conditions. omain.</p><p><b>Keywords:</b>Turbomachinery, Aerodynamics, Unsteady CFD,Design, Flutter, Low-Pressure Turbine, Blade Mode Shape,Critical Reduced Frequency, Sectored Vane Mode Shape, VibrationAmplitude Distribution, Far-field 2D Non-Reflecting BoundaryConditions.</p>

With the decrease in feature size in semiconductor manufacturing, molecular contamination problems are increased significantly. In order to optimize the yields in wafer fabrication units there is a need for process modeling that addresses the details of wafer contamination. Wafer contamination and cleaning is a complex process that covers various length and time scale events and phenomena. At the largest scales, there is the availability and transport of specific species within the fabrication unit and subsequent contamination of the wafer surface either through processing steps or through simple ambient transport processes. To limit wafer contaminant levels and/or to decontaminate them, wafers in the semiconductor fabrication unit are often cleaned and transported in a closed enclosure called Front Opening Unified Pod (FOUP) and purged with an inert gas like nitrogen. For the FOUP geometry, I analyze the large scale process modeling approaches to cleaning wafers. At smaller scales, the specific molecular configuration of the contaminant species impacts the kinetic chemical-physical cleaning mechanisms. To determine, from a fundamental perspective, the mechanisms contributing to wafer cleaning requires different scale tools from transport tools aimed at characterizing equipment scale (e.g., FOUP) contamination issues. I use molecular dynamics models and optimization techniques to infer physicochemical rates for molecular desorption on wafer surfaces. This dissertation considers these problems from a common perspective. The objective of this study has been to characterize the multi-scale problem of wafer cleaning with the objective of developing appropriate tools and models at different scales to best predict the dynamics of contaminant removal from wafer surfaces. A standardized method has been presented to extract kinetic rate parameters using molecular dynamics simulation (smaller-scale) and optimization for use in a larger-scale model of wafer decontamination using computational fluid dynamics (CFD). Also, by using available experimental data and CFD analysis an optimized FOUP purging recipe for better decontamination is presented and the relative magnitude of the time scales associated with surface kinetics and FOUP purging have been estimated. / text

This study focused on the improvement of film cooling for gas turbine vanes using both computational and experimental techniques. The experimental component used a matched Biot number model to measure scaled surface temperature (overall effectiveness) distributions representative of engine conditions for two new configurations. One configuration consisted of a single row of holes on the pressure surface while the other used numerous film cooling holes over the entire vane including a showerhead. Both configurations used internal impingement cooling representative of a 1st vane. Adiabatic effectiveness was also measured. No previous studies had shown the effect of injection on the mean and fluctuating velocity profiles for the suction surface, so measurements were made at two locations immediately upstream of film cooling holes from the fully cooled cooling configuration. Different blowing conditions were evaluated. Computational tools are increasingly important in the design of advanced gas turbine engines and validation of these tools is required prior to integration into the design process. Two film cooling configurations were simulated and compared to past experimental work. Data from matched Biot number experiments was used to validate the overall effectiveness from conjugate simulations in addition to adiabatic effectiveness. A simulation of a single row of cooling holes on the suction side also gave additional insight into the interaction of film cooling jets with the thermal boundary layer. A showerhead configuration was also simulated. The final portion of this study sought to evaluate the performance of six RANS models (standard, realizable, and renormalization group k-ε; standard k-ω; k-ω SST; and Transition SST) with respect to the prediction of thermal boundary layers. The turbulent Prandtl number was varied to test a simple method for improvement of the thermal boundary layer predictions. / text

The behaviour of gas-liquid foams has been the subject of extensive research in the past century because of the usefulness of liquid foams in industry. In this work we present new experimental and theoretical developments concerning flow and drainage behaviour of surfactant based liquid foams and films. The flow of free films and foam was studied in vertical tubes for different liquid properties. Measurements of the thickness of the lubricating layer on the wall and CFD simulation shows a relationship between the liquid thickness, liquid viscosity and pressure drop for the flow of free films. For foam flow, friction factors were determined for all systems and data lied remarkably on a unique line on the friction factor-Reynolds number plot and has a practical significance in that pressure drop can be calculated using a constant friction factor along a pipe of a constant cross section in any flow regime. An improved ER technique has been developed for accurate measurements of foam resistance, which includes the liquid layer at the wall. Traditional ER-methods for characterising the drainage of a wall-confined static foams do not take into consideration the effects of a substantial liquid layer established on the wall during drainage which transports a substantial amount of liquid. A method is proposed for the estimation of temporal as well axial variations of the wall liquid thickness inferred from the measurements of the local liquid holdup. A theoretical model is proposed for foam drainage based on the analogy of liquid flow through a packed bed of solid particles. A good agreement is obtained between theory and experiment on the basis of judicious estimations of foam cell size and shape factor.

Steady, three-dimensional viscous numerical analysis of airflow over a rectangular NACA 0012 base wing (BW) with a rounded tip and with three NACA 0015 tip-sails (WTS) is performed. The flow physics and aerodynamic forces are studied at Reynolds numbers (Re) of 60,000 and 600,000, angles of attack (α) of 0, 5, 7.5, and 10°, and two sets of tip-sail dihedral angles (leading to trailing tip-sail): 50, 45, and 40° and 60, 45, and 30°. The Shear Stress Transport turbulence and intermittency-transition Reynolds number transitional turbulence models were used. For α > 0°, the WTS produced higher lift coefficients (CL) and drag coefficients (CD) than the BW. At Re = 600,000 and α > 0°, the CL/CD was higher for the WTS than the BW. Good agreement was seen with experimental data at Re = 600,000 for the BW results and the WTS CL but not the WTS CD. / October 2015

The iron and steel industry emitted 8 % of all CO2 emissions in Sweden, 2011. Investigating alternative energy carriers is the purpose of this thesis. By pyrolyzing biomass, an energetic solid, gaseous and liquid (bio oil) fraction is obtained. If pyrolyzing biomass in a fluidized-bed reactor, the highest value may be added to the combined products. Additional understanding of pyrolysis in fluidized beds is pursued, using Computational Fluid Dynamics (CFD) and comprehensive kinetic schemes. The obtained solid product is investigated as a bio-injectant in blast furnaces for ironmaking. A new approach of separately modeling, the primary and secondary pyrolysis, is developed in this thesis. A biomass particle devolatilizes during pyrolysis. Primary pyrolysis is the solid decomposition which results in the volatiles that can leave the particle. Secondary pyrolysis is the decompositions of these volatiles, primarily in the gas phase. The primary pyrolysis (35 species, 15 reactions) mainly occurs in the bed-zone and as such, the model needs to take into account the complex physical interaction of biomass-particles with the fluidizing media (sand) and the fluidizing agent (gas). This is accomplished by representing the components by Eulerian phases and implementing interaction terms, as well as using a Stiff Chemistry Solver for the implemented reactions.  The secondary pyrolysis (not considering heterogeneous reactions), mainly occurs outside the bed zone in one phase. The fluid flow is simpler but the chemistry is more complex, with a larger variety of molecules emerging. Carrying out the simulations time-effectively, for the secondary pyrolysis (134 species, 4169 reactions) is accomplished by using Dimension Reduction, Chemistry Agglomeration and In-situ Tabulation (ISAT); in a Probability Density Functional (PDF) framework. An analysis of the numerical results suggest that they can be matched adequately with experimental measurements, considering pressure profiles, temperature profiles and the overall yield of gas, solid and liquid products. Also, with some exceptions, the yield of major and minor gaseous species can be matched to some extent. Hence, the complex physics and chemistry of the integrated process can be considered fairly well-considered but improvements are possible. A parametric study of reaction atmospheres (or fluidizing agents), is pursued as means of understanding the process better. The models revealed significant effects of the atmosphere, both physically (during the primary and secondary pyrolysis) and chemically (during secondary pyrolysis). During primary pyrolysis, the physical influence of reaction atmospheres (N2, H2O) is investigated. When comparing steam to nitrogen, heat flux to the biomass particles, using steam, is better distributed on a bed level and on a particle level. During secondary pyrolysis, results suggest that turbulence interaction plays an important role in accelerating unwanted decomposition of the liquid-forming volatiles. Steam, which is one of the investigated atmospheres (N2, H2O, H2, CO, CO2), resulted in a lower extent of unwanted secondary pyrolysis. Altough, steam neither resulted in the shortest vapor residence time, nor the lowest peak temperature, nor the lowest peak radical concentration; all factors known to disfavor secondary pyrolysis. A repeated case, using a high degree of turbulence at the inlet, resulted in extensive decompositions. The attractiveness of the approach is apparent but more testing and development is required; also with regards to the kinetic schemes, which have been called for by several other researchers. The solid fraction after pyrolysis is known as charcoal. Regarding its use in blast furnaces; modelling results indicate that full substitution of fossil coal is possible. Substantial reductions in CO2 emissions are hence possible. Energy savings are furthermore possible due to the higher oxygen content of charcoal (and bio-injectants in general), which leads to larger volumes of blast furnace gas containing more latent energy (and less non-recoverable sensible energy). Energy savings are possible, even considering additional electricity consumption for oxygen enrichment and a higher injection-rate on energy basis. A survey of biomass availability and existing technology suppliers in Sweden, suggest that all injection into Blast furnace M3 in Luleå, can be covered by biomass. Based on statistics from 2008, replacement of coal-by-charcoal from pyrolysis could reduce the on-site carbon dioxide emissions by 28.1 % (or 17.3 % of the emissions from the whole industry). For reference, torrefied material and raw biomass can reduce the on-site emissions by 6.4 % and 5.7 % respectively. / Järn och stålindustrin stod för 8 % av alla koldioxidutsläpp i Sverige, 2011. Alternativa energibärare undersöks i denna avhandling. Genom pyrolys av biomassa, fås en energirik fast produkt, och samtidigt en gasformig och en vätskeformig produkt (bio-olja). Om en fluidbäddsreaktor används kan största möjliga mervärde tillföras de kombinerade produkterna. Djupare förståelse för pyrolys i fluidbäddar har eftersträvats med hjälp fluiddynamikberäkningar (CFD) och detaljerade kinetikscheman. Den fasta produkten har undersökts som bio-injektion i masugnar. En ny approach för modellering av primär och sekundär pyrolys separat, har utvecklats i denna avhandling. En biomassapartikel avflyktigas under pyrolys. Primär pyrolys är nedrytningen av den fasta biomassan till intermediärer (flyktiga ämnen) som kan lämna partikeln. Sekundärpyrolys är nedbrytning av dessa flyktiga ämnen, som primärt sker i gasfas. Primärpyrolysen (i detta arbete, 35 ämnen och 15 reaktioner) sker mestadels i bäddzonen och därmed behöver modellen ta hänsyn till den komplexa fysiska interaktionen av biomassapartiklarna med fluidbäddsmediet (sand) och fluidiseringsgasen. Detta åstadkoms med hjälp av Euleriska faser och interaktionstermer, samt en lösare för hantering av styva reaktionssystem. Sekundärpyrolysen sker huvudsakligen utanför bäddzonen. Fluiddynamiken är enklare men kemin är mer komplex, med fler ämnen närvarande. Att tidseffektivt köra beräkningarna, för sekundärpyrolysen (134 ämnen, 4169 reaktioner) åstadkoms med hjälp Dimensionsreducering, Kemiagglomerering och In-situtabulering (ISAT); som implementerats i en sannolikhetstäthetsfunktion (PDF). En analys av de numeriska beräkningarna antyder att de kan matchas med experimentella resultat, med avseende på tryckprofil, temperaturprofil, utbyte av gasformiga, fasta och vätskeformiga produkter. Dessutom, med några undantag, kan beräkningarna matchas ganska väl med de viktigaste gasformiga produkterna. Därmed kan de huvudsakliga fysiska och kemikaliska mekanismerna representeras av modellen men förbättringar är givetvis möjliga. En parameterstudie av reaktionsatmosfärer (dvs fluidiseringsgaser) genomfördes, för att förstå processen bättre. Modellen visade på betydande effekter av atmosfären, fysisk (både under primär och sekundärpyrolys), och kemiskt (under sekundärpyrolysen).   Under primärpyrolysen undersöktes den fysiska inverkan av reaktionsatmosfärer (N2, H2O). När ånga jämfördes med kvävgas, visade det sig att värmeflödet sker mer homogent på både bäddnivå och på partikelnivå, med ångatmosfär. Under sekundärpyrolysen, så antyder resultaten på att turbulensinteraktion spelar en viktig roll för accelererad oönskad sekundärpyrolys av de vätskebildande ämnena. Ånga som är en av de undersökta atmosfärerna (N2, H2O, H2, CO, CO2), resulterade i den lägsta omfattningen av sekundärpyrolys. Dock så ledde en ångatmosfär varken till den lägsta residenstiden, den lägsta peaktemperaturen eller den lägsta radikalkoncentrationen; som alla normalt motverkar sekundärpyrolysen. Ett repeterat case, med hög turbulens i inloppet, gav betydande sekundärpyrolys av de vätskebildande ämnena. Attraktiviteten av approachen är given men mer testning och utveckling behövs, som också påkallats av andra forskare. Den fasta produkten efter pyrolys kallas träkol. Angående dess applicering i masugnar, så visar modelleringsresultaten att full substitution av fossilt kol går att göra. Betydande minskningar i koldioxidutsläpp är därmed möjliga. Energibesparingar är dessutom möjligt, tack vare det höga syreinnehållet i träkol (och biobränslen generellt), vilket ger större volymer av masugnsgas med högre värmevärde (och mindre sensibel värme som inte är utvinnbar). Energibesparingar är möjliga även om hänsyn tas till högre eleffekt för syrgasanrikning i blästerluften och en högre injektionsåtgång på energibasis. En översikt över biomassatillgången och existerande teknikleverantörer i Sverige, indikerar att all injektion i Masugn 3 (i Luleå) kan ersättas med biomassa. Baserat på statistik från 2008, så kan ersatt kol med träkol, minska de platsspecifika koldioxidutsläppen med 28.1 % (eller 17.3 % av alla utsläpp från stålindustrin). Som jämförelse kan torrifierad biomassa and obehandlad biomassa reducera utsläppen med 6.4 % respektive 5.7 %. / <p>QC 20150827</p>

The drag approximations done in the initial design phase needed to be verified. A model of the aircraft has been analyzed with CFD and results examined to see how accurate the estimations were. A step by step analysis was made and then a simulation was run. The drag results of the CFD analysis did not meet the goal of the initial design study. Several reasons for this are discussed. The analysis shows that the aircraft design works well aerodynamically but also shows a few areas where the design can be improved. / Det approximerade värdet på luftmotståndet som gjordes I den preliminära designfasen behövde verifieras. En flygplansmodell har analyserats med CFD och resultaten har undersökts för att se hur exakta antagandena var. En analys gjordes steg för steg och slutligen har en simulering utförts. Det uppmätta luftmotståndet motsvarade inte målet i den preliminära designfasen. Flera olika anledningar till detta diskuteras. Analysen visar att denna flygplansdesign fungerar bra aerodynamiskt men identifierar också en del punkter på vilken den kan förbättras.

This thesis presents a study of the cooling process of a solid block performed by a turbulent air flow channel. The study focuses on the turbulent flow and its influence in the heat transfer of the block. The first part of the thesis is an analysis of the different turbulent model and their adaptation on the necessities of this study. Once the turbulent model has been confirmed it makes a study of the behavior of the cooling process by CFD (Computational Fluid Dynamics), and an analysis of the numerical accuracy of this computational study. When the procedure of the study of the cooling process is defined it proposes some different variations in the initial solution to improve this process. The study concentrates in variations of the turbulence and the geometry of the studied block. Finally, the different improving are discussed analyzing parameters as the heat transfer, pressure drop, time consuming or energy consuming.