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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Resource management for data streaming applications

Agarwalla, Bikash Kumar 07 July 2010 (has links)
This dissertation investigates novel middleware mechanisms for building streaming applications. Developing streaming applications is a challenging task because (i) they are continuous in nature; (ii) they require fusion of data coming from multiple sources to derive higher level information; (iii) they require efficient transport of data from/to distributed sources and sinks; (iv) they need access to heterogeneous resources spanning sensor networks and high performance computing; and (v) they are time critical in nature. My thesis is that an intuitive programming abstraction will make it easier to build dynamic, distributed, and ubiquitous data streaming applications. Moreover, such an abstraction will enable an efficient allocation of shared and heterogeneous computational resources thereby making it easier for domain experts to build these applications. In support of the thesis, I present a novel programming abstraction, called DFuse, that makes it easier to develop these applications. A domain expert only needs to specify the input and output connections to fusion channels, and the fusion functions. The subsystems developed in this dissertation take care of instantiating the application, allocating resources for the application (via the scheduling heuristic developed in this dissertation) and dynamically managing the resources (via the dynamic scheduling algorithm presented in this dissertation). Through extensive performance evaluation, I demonstrate that the resources are allocated efficiently to optimize the throughput and latency constraints of an application.
62

Effects Of Extrapolation Boundary Conditions On Subsonic Mems Flows Over A Flat Plate

Turgut, Ozhan Hulusi 01 January 2006 (has links) (PDF)
In this research, subsonic rarefied flows over a flat-plate at constant pressure are investigated using the direct simulation Monte Carlo (DSMC) technique. An infinitely thin plate (either finite or semi-infinite) with zero angle of attack is considered. Flows with a Mach number of 0.102 and 0.4 and a Reynolds number varying between 0.063 and 246 are considered covering most of the transitional regime between the free-molecule and the continuum limits. A two-dimensional DSMC code of G.A. Bird is used to simulate these flows, and the code is modified to examine the effects of various inflow and outflow boundary conditions. It is observed that simulations of the subsonic rarefied flows are sensitive to the applied boundary conditions. Several extrapolation techniques are considered for the evaluation of the flow properties at the inflow and outflow boundaries. Among various alternatives, four techniques are considered in which the solutions are found to be relatively less sensitive. In addition to the commonly used extrapolation techniques, in which the flow properties are taken from the neighboring boundary cells of the domain, a newly developed extrapolation scheme, based on tracking streamlines, is applied to the outflow boundaries, and the best results are obtained using the new extrapolation technique together with the Neumann boundary conditions. With the new technique, the flow is not distorted even when the computational domain is small. Simulations are performed for various freestream conditions and computational domain configurations, and excellent agreement is obtained with the available experimental data.
63

Pricing of European- and American-style Asian Options using the Finite Element Method

Karlsson, Jesper January 2018 (has links)
An option is a contract between two parties where the holder has the option to buy or sell some underlying asset after a predefined exercise time. Options where the holder only has the right to buy or sell at the exercise time is said to be of European-style, while options that can be exercised any time before the exercise time is said to be of American-style. Asian options are options where the payoff is determined by some average value of the underlying asset, e.g., the arithmetic or the geometric average. For arithmetic Asian options, there are no closed-form pricing formulas, and one must apply numerical methods. Several methods have been proposed and tested for Asian options. For example, the Monte Carlo method isslowforEuropean-styleAsianoptionsandnotapplicableforAmerican-styleAsian options. In contrast, the finite difference method have successfully been applied to price both European- and American-style Asian options. But from a financial point of view, one is also interested in different measures of sensitivity, called the Greeks, which are hard approximate with the finite difference method. For more accurate approximations of the Greeks, researchers have turned to the finite element method with promising results for European-style Asian options. However, the finite element method has never been applied to American-style Asian options, which still lack accurate approximations of the Greeks. Here we present a study of pricing European- and American-style Asian options using the finite element method. For European-style options, we consider two different pricing PDEs. The first equation we consider is a convection-dominated problem, which we solve by applying the so-called streamline-diffusion method. The second equation comes from modelling Asian options as options on a traded account, which we solve by using the so-called cG(1)cG(1) method. For American-style options, the model based on options on a traded account is not applicable. Therefore, we must consider the first convection-dominated problem. To handle American-style options, we study two different methods, a penalty method and the projected successive over-relaxation method. For European-style Asian options, both approaches give good results, but the model based on options on a traded account show more accurate results. For American-style Asian options, the penalty method give accurate results. Meanwhile, the projected successive over-relaxation method does not converge properly for the tested parameters. Our result is a first step towards an accurate and fast method to calculate the price and the Greeks of both European- and American-style Asian options. Because good estimations of the Greeks are crucial when hedging and trading of options, we anticipate that the ideas presented in this work can lead to new ways of trading with Asian options.
64

Effektivisering av produktionen av en ljudabsorbent i kartong / Streamlining the production of a cardboard sound absorber

Panikian Aljunidi, Elias, Skoglund, Joakim January 2022 (has links)
Sontech International AB är ett företag som är specialiserade på ljudabsorbenter i metall och skum. De har tagit fram en ljudabsorbent i kartong med slitsar som går längs arket med ett avstånd på max 5 mm mellan dem. Denna produceras idag med en CNC-maskin och det tar 17 minuter per kvadratmeter att producera absorbenten med 5 mm mellan slitsarna. För att produkten ska vara lönsam behöver produktionstiden ned på en minut per kvadratmeter. Det är ett relativt litet företag med stora kunder och har därför inte tid eller resurser att lägga på att utveckla produktionen av den. Därför har författarna fått i ansvar att som examensarbete inom maskinteknik försöka utveckla och till sist presentera en färdig modell på en maskin för lösningen. Efter skisser, prototyper och val mellan tre färdiga modeller på föll valet på maskinen vid namn Krattan. Krattan drivs med två pneumatiska cylindrar som lyfter upp arket och drar vad som kallas krattan som består av 199 knivar tvärs över det. Produktionstiden uppskattas ha sjunkit till ca 20 sekunder per kvadratmeter kartongark. / Sontech International AB is a company that specializes in sound absorbents made of metal and foam. They have a new product that is a sound absorbent made of cardboard with cuts along the sheet of cardboard with a maximum distance between the cuts of 5 mm. This product is made with a CNC-machine and it takes 17 minutes per square meter to produce a sheet with 5 mm between each cut. To make the product viable the production time needs to come down to a minute per square meter. Sontech is are latively small company which is why they have not been able to spare the resources to develop a solution for manufacturing this product. The writers have based their thesis paper in mechanical engineering on developing and presenting a complete model of a machine as a method of production. After many sketches, prototypes and a selection between three different solutions they picked a machine that they refer to as ‘‘The rake’’. ‘’The rake’’ is powered by two pneumatic cylinders. One cylinder lifts the sheet of cardboard and either pushes or pulls ‘’the rake’’ part of the machine that is made of 199 blades. The production time is estimated to be about twenty seconds per square meter of cardboard.
65

組織重組理論與實踐-第二階段精省作業對內政部組織重組影響之實證分析 / The theory and practice of reorganization: the practical analysis of the reorganization's effect on the Ministry of Interior in the second stage of streamlined-provincial project

李玉惠 Unknown Date (has links)
一九八0年以來政府再造蔚為世界風潮,組織改造工程為各國因應財政壓力及行政效率低落的重要基礎建設。蕭萬長內閣啟動精省列車,陳水扁總統重啟行政院組織法修正,皆有龐大政治效應,如何經驗接軌,為本文研究之動機。經由分析整理相關理論,探討組織重組可能的成因和動力,並藉由內政部精省第二階段組織調整作業之個案分析,希望透過理論的粹煉和展演,提昇組織重組的執行力,俾全面提昇政府效能,最後作者提出八項結論及八項建議。結論部分計列:一、影響公共組織組織重組因素中,以政治因素居首,其次為經濟因素,管理因素影響最微。二、組織重組機會之窗的開啟需以有重大事件為先決條件。三、組織重組的動力依序源於民意機關、上級機關及行政首長。四、組織重組方案係理性規劃或非理性規劃,端視其內、外推拉力量而定。五、組織調整方案應重視配套法案及其立法優先順序。六、組織調整方案應兼具穩健及開創性。七、第二階段精省作業強調員額精簡。八、第二階段精省組織調整之最大特色即組織法律制(修)定及暫行組織規程修訂案雙軌併行等八項。建議部分計列:一、組織改造核心理念應為政府職能調整,即為塑身,非瘦身。二、重視組織法制變革作業,且應有配套及優先審議順序。三、為顧及原省府員工權益,行政院應同意部會地區辦公室職務列等得逕依部會標準調列。四、組織重組方案應兼及穩健及開創性。五、組織重組方案合法化過程,應建立立法、行政及輿論之多數聯盟以爭取政治支持。六、應強化機關首長執行之意志。七、組織重組過程應重視員工權益,惟亦應避免人才反淘汰。八、訂定日出條款以縮短組織調整過渡期,避免組織動盪不安等八項。 / Since 1980 the government restructuring is the trend, the enginge of the organization reform is an important infrastructure to deal with the financial pressure and the loweringly administrative efficiency. The Shuie Cabinet starts the streamlined-provincial project,The President Chen Shui-bian starts the reform of the Executive Yuan Organization Act. There are both giganticly political effect.The motive of this paper is how to connect experience of both reforms.Through the analysis of relective theories and by the case study of the Ministry of Interior in the second stge of streamlined- provincial project to discuss on the possible cause and driver of reorganization. We hope to evaluate the implementing ability of reorganization to increase the government's efficiency wholesale.   In the end the writer has some suggestions:   一.The focus concept of the organizational reform is to accommate the government's function.In short way, it is shapping, not thinning.   二.To emphasis the modification of organization regulation and set its priority.   三.For pre-provincal employee's interest,the position-setting standards must be similar.   四.The reorganizational reform project must both be stable and innovative.   五.The legalization process of the reorganization project must build the majority of legal, administrative and public opponines to win the political support.   六.To reforce the implementing will of the executive.   七.To emphasis employee's interest, but avoid the talented's turnover.   八.To set the sunrise clause to shorten the passage of organization reform.
66

中國稀土的政治經濟分析 / The political economy analysis of China’s rare earth

吳皇明, Wu, Huan Ming Unknown Date (has links)
自2010年9月以來,中國大陸限制對日稀土出口所造成影響,在全球演然以成為熱門話題,亦為我所探究本論文鵠的。當時中國大陸在一片撻伐聲中,似成麻煩製造者,因影響片及整體稀土元素供需市場,特別是那些缺乏稀土元素生產卻又非常依賴中國大陸稀土的進口廠商所發出來的抗議。然事實上,稀土這元素在地球上並不匱乏,但因為它的開採上的成本高利潤卻不高,相對存量卻一直減少造成許多國家並不願去開採它,漸漸全球高逹95%以上的生產量由中國取代,卻也間接造成中國在稀土市場上的獨佔市場地位,但中國卻又是整個稀土市場價格的接受者,供需不均衡所造成的結果卻是相反地。因此中國政府當局大力支持與整合稀土產業進行一連串的體制改造及革新計畫整體架構十分迅速進行中。 此篇論文藉由所蒐集匱乏資料分析瞭解中國大陸稀土元素的發展,並透過經濟、政治分析中國不宜過度依賴稀土短期優勢,事實上,應可加強其稀土整體計劃在國際發展空間、提升稀土產業效能及加速其產業整合與技術提煉上改進,並同時兼顧環保及降低開採上污染等多個面向的思考,再者更瞭解稀土資源不但可增進人類的生活品質,其根本是歸屬大地之母-地球所擁有。 / The objective of this paper is to explore the hot issues of China’s Rare Earths Elements (REEs) on the global. Using a commonly-accepted methods and materials to research of China’s REEs, On the whole, the impact of China’s REEs restriction is almost regarded as mainstream troublemaker who become overshadows influence the REEs market in the world. However it’s not, On the contrary, the Earth is not in shortage of rare earth resources. The problem is in the worldwide supply and demand structure of REEs unbalance and the price is not reasonable for China’s REEs. China’s REEs growing forcefulness regards as a new strength called attention to foreign powers claim China stops exports of rare earth is completely groundless. REEs are as a new symbol of strength and high value metals in upcoming century changed China’s REEs racial policies turn into aggressively to enhance its national level security and pursing its welfare and hegemony in REEs. China is devoted to manage its REEs output quota reduced reliance on demand countries as strategic policies but so to the foreign countries changed their policies. Analysis of the paper indicated basic findings. China holds a main of capturing a larger portion of the global supply but couldn’t depend on its superiority of REEs’ reserves. In other words, China should be devoted to develop its REEs policies as a way to promote and engage China’s REEs grow space agenda with the rest of the world. Find ways to deals with the rough harsh international reality, strive to streamline its rare earth industry, accelerate industrial upgrading, technological innovation in accordance to protect its domestic REEs industries, the environment, reserve REEs resources and learn how to get along with other countries. Extremely, the China government should recognize the resources of REEs are belonging to human-beings and the Earth, not only to China has.
67

Stress, Flow and Particle Transport in Rock Fractures

Koyama, Tomofumi January 2007 (has links)
The fluid flow and tracer transport in a single rock fracture during shear processes has been an important issue in rock mechanics and is investigated in this thesis using Finite Element Method (FEM) and streamline particle tracking method, considering evolutions of aperture and transmissivity with shear displacement histories under different normal stresses, based on laboratory tests. The distributions of fracture aperture and its evolution during shear were calculated from the initial aperture fields, based on the laser-scanned surface roughness features of replicas of rock fracture specimens, and shear dilations measured during the coupled shear-flow-tracer tests in laboratory performed using a newly developed testing apparatus in Nagasaki University, Nagasaki, Japan. Three rock fractures of granite with different roughness characteristics were used as parent samples from which nine plaster replicas were made and coupled shear-flow tests was performed under three normal loading conditions (two levels of constant normal loading (CNL) and one constant normal stiffness (CNS) conditions). In order to visualize the tracer transport, transparent acrylic upper parts and plaster lower parts of the fracture specimens were manufactured from an artificially created tensile fracture of sandstone and the coupled shear-flow tests with fluid visualization was performed using a dye tracer injected from upstream and a CCD camera to record the dye movement. A special algorithm for treating the contact areas as zero-aperture elements was used to produce more accurate flow field simulations by using FEM, which is important for continued simulations of particle transport, but was often not properly treated in literature. The simulation results agreed well with the flow rate data obtained from the laboratory tests, showing that complex histories of fracture aperture and tortuous flow channels with changing normal stresses and increasing shear displacements, which were also captured by the coupled shear-flow tests of fracture specimens with visualization of the fluid flow. From the obtained flow velocity fields, the particle transport was predicted by the streamline particle tracking method with calculated flow velocity fields (vectors) from the flow simulations, obtaining results such as flow velocity profiles, total flow rates, particle travel time, breakthrough curves and the Péclet number, Pe, respectively. The fluid flow in the vertical 2-D cross-sections of a rock fracture was also simulated by solving both Navier-Stokes (NS) and Reynolds equations, and the particle transport was predicted by streamline particle tracking method. The results obtained using NS and Reynolds equations were compared to illustrate the degree of the validity of the Reynolds equation for general applications in practice since the later is mush more computationally efficient for large scale problems. The flow simulation results show that the total flow rate and the flow velocity predicted by NS equations are quite different from that as predicted by the Reynolds equation. The results show that a roughly 5-10 % overestimation on the flow rate is produced when the Reynolds equation is used, and the ideal parabolic velocity profiles defined by the local cubic law, when Reynolds equation is used, is no longer valid, especially when the roughness feature of the fracture surfaces changes with shear. These deviations of flow rate and flow velocity profiles across the fracture aperture have a significant impact on the particle transport behavior and the associated properties, such as the travel time and Péclet number. The deviations increase with increasing flow velocity and become more significant when fracture aperture geometry changes with shear. The scientific findings from these studies provided new insights to the physical behavior of fluid flow and mass transport in rock fractures which is the scientific basis for many rock mechanics problems at the fundamental level, and with special importance to rock engineering problems such as geothermal energy extraction (where flow rate in fractures dominates the productivity of a geothermal energy reservoir) and nuclear waste repositories (where radioactive nuclides transport through fractures dominates the final safety evaluations) in fractured rocks. / Vätskeflödet och spårämnestransporten i en enskild bergsspricka under skjuvningsprocesser har varit ett viktigt ämne inom bergmekanik. I denna avhandling undersöks ämnet med hjälp av finita element metoden (FEM) och en strömlinjebaserad partikelspårningsmetod. Hänsyn tas till utveckling av öppningar och transmissivitet med skjuvningens förflyttningshistoria under olika normala belastningar baserat på laboratorietester. Fördelningen av spricköppningar och deras utveckling under skjuvning beräknades från de initiala öppningsfälten baserat på det laserscannade provets ytas grovhetskännetecken sam tskjuvningsöppningar uppmätta under de kopplade skjuvning-flöde-spårämneslaboratorietesterna som utförts med nyutvecklad testapparatur i Nagasaki Universitet i Nagasaki, Japan. Tre bergssprickor i granit med olika grovhetskarakteristika användes som utgångsprover från vilka nio gipskopior gjordes. Kopplade skjuvning-flödes tester utfördes sedan under tre normala belastningstillstånd (två nivåer med konstant normal last (KNL) och en konstant normal styvhetstillstånd (KNS). För att visualisera spårämnestransporten tillverkades en transparent övre del av sprickproverna av akryl och en nedre del av gipsbaserat på en kostgjord spänningsspricka i sandsten och de kopplade skjuvning-flödes testerna med vätskevisualisering utfördes med färgspårämne injekterat uppströms och en CCD kamera monterad ovanför för att registrera färgens rörelse. En särskild algoritm användes för att behandla kontaktytorna som nollöppningsämnen användes för att åstadkomma mer exakta flödesfältssimuleringar med FEM. Detta är viktigt för kontinuerliga simuleringar av partikelflöden men uppmärksammas oftast inte tillräckligt i litteraturen. Simuleringsresultaten överensstämde väl med de flödesnivådata som erhölls från laboratorietesterna vilket visade att komplexa historier av spricköppningar och invecklade flöden överensstämde med ändrade normala belastningar och ökande skjuvningsförflyttningar, vilket även fångades av de kopplade skjuvning-flödestesterna av sprickproverna genom visualisering av vätskeflödet. Från de erhållna flödesfälten förutsågs partikeltransporten genom en strömlinjebaserad partikelspårningsmetod med kalkylerade flödeshastighetsfält (vektorer) från flödessimuleringarna genom vilka resultat som flödeshastighetsprofiler, totala flödesnivåer,partikeltransporttid, genombrottskurvor samt Pécletnumret, Pe, erhölls. Vätskeflödet i det vertikala tvådimensionella tvärsnittet av en bergsspricka simulerades även genom att både Navier-Stokes (NS) och Reynoldsekvationerna löstes och partikeltransporten förutsågs genom den strömlinjebaserade partikelspårningsmetoden. Resultaten som erhöllsmed NS och Reynoldsekvationerna jämfördes för att illustrera graden av tillförlitlighet för Reynoldsekvationen för allmänna tillämpningar i praktiken då den senare är betydligt mer beräkningseffektiv för storskaliga problem. Resultaten från flödessimuleringarna visar att den totala flödesnivån och den totala flödeshastigheten förutsedda med NS ekvationer är helt annorlunda motsvarande värden som förutsågs med Reynoldsekvationen. Resultaten visar att en ca 5-10 % för hög uppskattning av flödesnivån erhålls då Reynoldsekvationen används och de ideala parabola hastighetsprofilerna, som definieras av den lokala kubiklagen när Reynoldsekvationen används, inte längre är giltiga särskilt när sprickytornas grovhetskarakteristika ändras med skjuvning. De här avvikelserna i flödesnivå och flödeshastighetsprofiler längs med spricköppningen har en betydande påverkan på partikeltransportuppträdande och de tillhörande egenskaperna såsom rörelsetid och Pécletnummer. Avvikelserna ökar med ökande flödeshastighet och blir mer signifikanta när spricköppningarnas geometri ändras med skjuvning. Forskningsresultaten från dessa studier gav nya insikter i de fysiska uppträdandet av vätskeflöde och masstransporter i bergssprickor vilket är den vetenskapliga basen för många bergmekanikproblem på grundläggande nivå och som har särskild vikt för bergstekniksproblem såsom geotermisk energiutvinning (där flödesnivå i sprickor dominerar produktiviteten för en geotermisk energikälla) och kärnavfallsförvaringsplatser (där transporten av radioaktiva nuklider genom sprickor dominerar den slutgiltigasäkerhetsutvärderingen) i sprickigt berg. / QC 20100803
68

Transition Zone In Constant Pressure Boundary Layer With Converging Streamlines

Vasudevan, K P 01 1900 (has links)
The laminar-turbulent transition in viscous fluid flows is one of the most intriguing problems in fluid dynamics today. In view of the enormous applications it has in a variety of fields such as aircraft design, turbomachinery, etc., scientists have now realized the importance of tackling this problem effectively. Three-dimensional flows are usually associated with pressure gradient, streamline curvature, streamline convergence / divergence etc., all acting simultaneously. Towards a better understanding of the transition process and modeling the transition zone, it is important to study the effect of each of these parameters on the transitional flow. The present work aims at studying experimentally the effect of lateral streamline convergence alone on the laminar-turbulent transition zone under constant stream-wise pressure. The experimental setup consists of a low turbulence wind tunnel with its test section modified to cause lateral streamline convergence under constant pressure. This is achieved by converging the side-walls and appropriately diverging the roof, thus maintaining a constant stream-wise pressure. The half angle of convergence is chosen as 100 , which is approximately the same as the half of the turbulent spot envelope in constant pressure two-dimensional flows. Experiments are carried out to analyze the development of the laminar and transitional boundary layers, intermittency distribution in the transition zone and the overall characteristics of an artificially induced turbulent spot. The laminar velocity profiles are found to be of the Blasius type for two-dimensional constant pressure flows. However, the converging streamlines are found to contribute to an increased thickness of the boundary layer as compared to the corresponding two-dimensional flow. The intermittency distribution in the transition zone is found to follow the universal intermittency distribution for two-dimensional constant pressure flow. A simple linear-combination model for two-dimensional flows is found to perform very well in predicting the measured velocity profiles in the transition zone. An artificially introduced turbulent spot is found to propagate along a conical envelope with an apex cone angle of 220 which is very nearly the value for a corresponding constant pressure two-dimensional flow. The spot shapes and celerities are also comparable to those in two-dimensional flow. In summary, the present study brings out many similarities between a constant pressure laterally converging flow and a constant pressure two-dimensional flow.
69

Modeling single-phase flow and solute transport across scales

Mehmani, Yashar 16 February 2015 (has links)
Flow and transport phenomena in the subsurface often span a wide range of length (nanometers to kilometers) and time (nanoseconds to years) scales, and frequently arise in applications of CO₂ sequestration, pollutant transport, and near-well acid stimulation. Reliable field-scale predictions depend on our predictive capacity at each individual scale as well as our ability to accurately propagate information across scales. Pore-scale modeling (coupled with experiments) has assumed an important role in improving our fundamental understanding at the small scale, and is frequently used to inform/guide modeling efforts at larger scales. Among the various methods, there often exists a trade-off between computational efficiency/simplicity and accuracy. While high-resolution methods are very accurate, they are computationally limited to relatively small domains. Since macroscopic properties of a porous medium are statistically representative only when sample sizes are sufficiently large, simple and efficient pore-scale methods are more attractive. In this work, two Eulerian pore-network models for simulating single-phase flow and solute transport are developed. The models focus on capturing two key pore-level mechanisms: a) partial mixing within pores (large void volumes), and b) shear dispersion within throats (narrow constrictions connecting the pores), which are shown to have a substantial impact on transverse and longitudinal dispersion coefficients at the macro scale. The models are verified with high-resolution pore-scale methods and validated against micromodel experiments as well as experimental data from the literature. Studies regarding the significance of different pore-level mixing assumptions (perfect mixing vs. partial mixing) in disordered media, as well as the predictive capacity of network modeling as a whole for ordered media are conducted. A mortar domain decomposition framework is additionally developed, under which efficient and accurate simulations on even larger and highly heterogeneous pore-scale domains are feasible. The mortar methods are verified and parallel scalability is demonstrated. It is shown that they can be used as “hybrid” methods for coupling localized pore-scale inclusions to a surrounding continuum (when insufficient scale separation exists). The framework further permits multi-model simulations within the same computational domain. An application of the methods studying “emergent” behavior during calcite precipitation in the context of geologic CO₂ sequestration is provided. / text
70

Design- och simuleringsstudie av flödeshus och sensorkropp / A design and simulation study of a sensor body and flow housing

Larsson Sparr, Klara, Muhonen, Mathias January 2020 (has links)
I detta arbete har ett koncept utvecklats för en flödesmätningsmetod med en intern sensorkropp samt bibehållen flödeshastighet. Denna mätmetod består av en sensorkropp i ett flödeshus där mätningen av flödet utförs med hjälp av pitotrörsberäkningar. Två olika lösningar presenteras i detta arbete, där skillnaderna grundar sig i utformningen av sensorkroppen. Sensorkroppens tvärsnitt är liknande för båda lösningarna. Den ena lösningen är rotationssymmetrisk i centrum av röret medan den andra går från vägg till vägg centrerat i röret. För att åstadkomma bibehållen flödeshastighet så utfördes beräkningar för att modellera flödeshuset, så att flödets tvärsnittsarea motsvarade arean i röret utan sensorkropp. I dessa beräkningar ingick även att kompensera för ökade solida ytor, då dessa ytor skapar gränsskikt där flödets hastighet sänks. Jämförelser mellan arbetets genererade koncept och uppdragsgivarens nuvarande produkter utfördes. Jämförelsen resulterade i flera områden där arbetets koncept skulle kunna komplettera redan befintliga produkter. / In this project a concept for flow measurement has been developed, where there is an internal sensor body as well as a constant flow speed. This measurement method consists of a sensor body in a flow housing where the flow measurement is done using conventional pitot tube calculations. Two different solutions are presented in this work, the differences between the two solutions are based on the design of the sensor body. The cross-section of the sensor body is similar for both solutions, but one solution is rotationally symmetrical while the other goes from wall to wall. Both sensor bodies are centered in the tube. To accomplish continuous flow speed, calculations were made to model the flow housing, so the cross-sectional area of the flow corresponded to the area of the tube without the sensor body. In these calculations a compensation factor for increased solid surface area were included, as this area creates a boundary layer that lowers the flow speed and changes based on the design of the sensor body. Comparisons between the concept in this project and the commissioner's current products were made. This comparison resulted in several areas where this projects concept could complement existing products.

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