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Thermal Analysis of a Sea Wave GeneratorQuijada, Ezequiel January 2017 (has links)
Wave power has been increasing the interest of many researchers looking for alternative sustainable energy sources since the reserves have proved to be capable of satisfying a considerable percentage of the world´s energy demands. This option has not been adopted as a sustainable source since there are some challenges in the process of designing a low cost device that converts the kinetic energy of the waves into electric energy and that could still be efficient enough to be competitive against other options. A new proposal from Anders Hagnestål looks like a very promising way of moving forward in this field. The structure of this newly proposed generator includes neodymium magnets that at temperatures over 60°C might suffer irreversible demagnetization, compromising the normal functioning of the machine. Because of the electrical losses in iron components, overheating is a possibility that must be studied. The aim of this study is to find the temperature distribution of the components that are subject to changing magnetic fields (where the losses will occur). This will be done for a variety of cases regarding environmental and working conditions with the purpose of determining if the generator will need a cooling technique to avoid damage to the magnets. The studied structure consists of a stator and a translator conformed by iron, FR4, glass fiber and, of course, the magnets. The task at hand was carried out first through a one-dimensional analytical model, then through a two-dimensional analytical model and finally by means of simulations on Comsol Multiphysics (Computer-Aided-Engineering software). All of the aforementioned methods implicate assumptions that deviate from reality, but are still useful for the task at hand. Results from the 1D calculation turned out to be unreliable due to the numerous approximations but helped to prove and understand the effect of each of the environmental conditions on the temperature distribution. On the other hand, the 2D calculations and the simulations had a very good agreement which provides some reliability. Furthermore, said results showed that the components might even reach temperatures as high as 380°C under certain conditions. As this number is clearly over the safe limit of the magnets, it was concluded that cooling techniques are needed to ensure the safety of the generator. After some discussion with Hagnestål, cooling methods were proposed. In addition to this, the seemingly most appropriate option was pointed out with the intention of achieving a low-enough temperature and keeping the costs as low as possible. This alternative was a combination of modifying geometric parameters (which would ultimately reduce heat generation) and inducing a low velocity air flow. / Vågkraft är en hittills outnyttjad förnybar energikälla som i framtiden kan tillgodose i storleksordningen 10 % av världens energibehov, om de tekniska utmaningarna kan lösas så att vågkraft kan levereras till konkurrenskraftiga priser. Därmed finns också ett starkt intresse från både akademi och näringsliv att lösa dessa utmaningar. Anders Hagnestål håller på att utveckla en ny linjär generatortyp som enligt beräkningar slår alla befintliga lösningar för effektomvandling för vågkraft med bred marginal. Maskinen har dock komplex geometri, och det är svårt att beräkna dess prestanda. Maskinen innehåller neodymmagneter, vilka kan avmagnetiseras om de blir för varma där 60°C kan ses som en gräns då magneterna börjar påverkas. Om magneterna avmagnetiseras blir maskinen svagare. Eftersom magneterna upphettas av virvelströmmar i magneterna och förluster i omgivande elektroplåt, är det av intresse att göra en termisk analys av maskinen vilket är syftet med detta examensarbete. Målet är att beräkna temperaturutbredningen i maskinens olika delar vid olika driftsfall, och se om man behöver tillföra extern kylning av maskinen för att skydda magneterna. Maskinen består av en translator som omsluter den inre statorn där magneterna är lokaliserade, vilka är byggda av fiberkompositer, elektroplåt, rostfritt stål och neodymmagneter. Beräkningar gjordes först med en endimensionell analytisk modell, därefter med en tvådimensionell analytisk modell och slutligen med numeriska beräkningar i 2D med det kommersiella finita elementmetodberäkningsprogrammet Comsol Multiphysics. Samtliga dessa modeller har avvikelser från det verkliga fallet, men är ändå användbara och ger en fingervisning om hur den termiska situationen för maskinen kan se ut. 1D-beräkningarna visade sig innehålla lite för grova approximationer för att ge pålitliga resultat, men gav en del intuitiv insikt om problemet. Den analytiska 2D-beräkningen stämde bra överens med Comsol-beräkningen, vilket indikerar att beräkningarna är korrekta. Resultaten visade på mycket höga temperaturer i vissa driftsfall utan kylsystem, 380 °C, vilket är en indikator på att antingen någon form av kylning förmodligen behövs, i.a.f. i en del driftsfall, eller att värmeförlusterna i den delen av generatorn behöver minskas genom t.ex. att pollängden ökas. En kombination av luftflöden med låg hastighet och förändrad geometri har föreslagits i examensarbetet för att minska temperaturen.
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Parametric Studies of Soil-Steel Composite Bridges for Dynamic Loads, a Frequency Domain Approach using 3D Finite Element ModellingLjung, Jonathan January 2019 (has links)
In this thesis, parametric studies have been performed for a soil-steel compositebridge to determine and investigate the most influential parameters on the dynamicresponse.High-speed railways are currently being planned in Sweden by the Swedish TransportAdministration with train speeds up to 320 km/h. According to the European designcodes, bridges must be verified with respect to dynamic resonance behaviour for trainspeeds exceeding 200 km/h. However, there are no guidelines or design criterion forperforming dynamic verifications of soil-steel composite bridges. The aim of thisthesis has therefore been to investigate the influence of the geometry and materialproperties of soil-steel composite bridges on their dynamic response.This thesis is based upon the frequency domain approach for dynamic analysis ofa soil-steel composite bridge using finite element software. In 2018, field measurementswere performed on a soil-steel composite bridge in Hårestorp, Sweden. Areference finite element model was developed based on previous research and wasverified against these field measurements. Parametric studies where performed byextrapolating the geometry of the reference model, focusing primarily on the crownheight, culvert span width and the location of the bedrock. Sensitivity analyses ofthe density- and stiffness of the soil was also performed.The parametric studies showed that the crown height was the most influential parameterwith respect to the amplitude of the resonance peak. Increasing it from 1 mto 3 m reduced the amplitude by approximately 70 %. An increased span width ofthe culvert was found to reduce the frequency and amplitude of the resonance peak,however increasing the stiffness of the culvert increased the resonance frequency.The position of the rock layer also reduced the amplitude of the resonance peak iflowered, likely because of lessened wave reflection. The lowest rock level investigatedshowed a significant decrease of more than 70 % in amplitude. However, the modelused to calculate this response was heavily extrapolated and thus difficult to verify.The sensitivity analyses showed that the soil density- and stiffness was negativelyand positively correlated with the resonance frequency, respectively. Additionally,the soil density lowered the amplitude of the resonance peak if increased.
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Investigating the decrease ofgroundwater levels and the effect of fracture zone on recovery time: A case study of decrease in groundwater levels in a tunnel construction site in Vinsta, StockholmKassiou, Evgenia January 2017 (has links)
Groundwater is one of the main natural resources worldwide. Groundwater exists in aquifers below the earth surface and provides quantities of water for various purposes such as supply to households and businesses, public supply, drinking water supply, irrigation and agriculture. Sweden is also highly dependent on groundwater. As mentioned in the list of 16 Environmental Quality Objectives, that the Swedish Parliament established, "groundwater must assure a safe and sustainable supply of drinking water, as well as promoting viable habitats for plants and animals in lakes and watercourses". However, the protection of groundwater and generally the aquifer resources is prone to various human activities that are harmful in terms of volume and quality. The present thesis aims to investigate the behavior of groundwater towards such human activities of large scales, like a tunnel construction, and small scale, like a construction of a geothermal plant. The area under study is investigated through spatial analysis, using ArcGIS; the groundwater levels are monitored and further statistically analyzed by implementing a Modified Double Mass Statistical Analysis; and further on a 3D numerical model is built in COMSOL Multiphysics in order to simulate possible drawdown caused by human intervention to the natural environment. The created 3D model was used in order to evaluate the drawdown and different scenarios were implemented with the aim to determine the degree of sensitivity the model has towards fracture parameters. Since the occurrence of fractures in the rock mass is often connected to extended investigation and time/cost consuming techniques, the model contains an overall uncertainty concerning the location and properties of the fracture formations in the area. The different scenarios involve variation of fracture zone width and thus the behavior of the top soil layer is investigated in terms of recovery after drawdown. The results indicated connection to human activities, with the statistical analysis to support this. Also, the numerical model showed that the fracture properties are connected to the recovery time of the groundwater levels after a drawdown is noticed. Wider fracture zone width implied more time needed for the groundwater levels to get to their initial values, under the perception that the source of recharge is precipitation. On the other hand, narrow fracture zone width was connected with greater drawdown, compared to the wider width scenario, and also earlier in time recovery of the groundwater levels. The type of the soil layer and its vulnerability to human activities can vary greatly in terms of volume loss which can prove a hazard to existing infrastructure on the ground surface. The present study can prove useful in cases of prestudy of drilling projects of any scale. There is strong connection between fracture formations and recovery of groundwater levels and thus such kind of models can generate innovative techniques of planning before a project begins. / Grundvatten är en av de viktigaste naturresurserna världen över. Grundvatten finns i akviferer under jordytan och ger vatten för olika ändamål så som tillförsel till hushåll och företag, kommunalt bruk, dricksvattenförsörjning, bevattning och jordbruk. Även Sverige är mycket beroende av grundvatten. I en sammanställning av 16 nationella miljökvalitetsmål fastställde riksdagen bland annat att "grundvatten måste säkerställa ett säkert och hållbart utbud av dricksvatten samt att främja livskraftiga livsmiljöer för växter och djur i sjöar och vattendrag". Skyddet av grundvatten och de allmänna vattenresursresurserna är framtaget för att begränsa påverkan från olika mänskliga aktiviteter som är skadliga när det gäller volym och kvalitet. Föreliggande uppsats syftar till att undersöka grundvattnets beteende till följd av storskaliga mänskliga aktiviteter, till exempel en tunnelkonstruktion, och mindre aktiviteter, till exempel byggnation av en geotermisk anläggning. Det område som studeras undersöks genom rumslig analys, med hjälp av ArcGIS; grundvattennivån övervakas och analyseras vidare statistiskt genom implementering av en statistisk analys av Modified Double Mass Statistical Analysis; en numerisk 3D-modell byggs i mjukvaran COMSOL Multiphysics för att simulera möjlig grundvattennivåsänkning orsakad av mänsklig påverkan i den naturliga miljön. 3D-modellen användes för att utvärdera eventuell grundvattensänkning och olika scenarier implementerades med syfte att bestämma graden av känslighet med avseende på sprickparameterar i modellen. Eftersom förekomst av sprickor i bergmassan ofta innebär ett behov av utökad undersökning och tid/kostnadskrävande tekniker innehåller modellen en övergripande osäkerhet om platsen samt egenskaper hos sprickorna i området. De olika scenarierna involverar variation av sprickzonsbredd och det övre jordskiktets beteende betraktas i termer av återhämtning efter avsänkt grundvattennivå. Resultaten indikerade koppling till mänskliga aktiviteter, den statistiska analysen stödjer detta. Den numeriska modellen visade också att sprickornas egenskaper är kopplade till grundvattennivåernas återhämtningstid efter det att en grundvattennivåsänkning noterats. Bredare sprickzonsbredd innebar längre återhämtningstid för grundvattennivåerna att stiga till deras ursprungliga värden, under förutsättning att källan till återhämtning är nederbörd. Å andra sidan var en smalare sprickzonsbredd förenad med större grundvattenavsänkning samt snabbare återhämtning av grundvattennivån jämfört med scenariot för bredare sprickzoner. Jordlagrets typ och dess känslighet för påverkan från mänskliga aktiviteter kan variera kraftigt i fråga om volymförlust vilket kan utgöra en fara för befintlig infrastruktur på markytan. Den aktuella studien kan vara användbar i förstudier till borrprojekt av vilken skala som helst. Det finns stark koppling mellan sprickbildning och återhämtning av grundvattennivån, och sålunda denna typ av modeller generera innovativa planeringstekniker innan ett projekt börjar.
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Fluid Flow Characterization and In Silico Validation in a Rapid Prototyped Aortic Arch ModelKnauer, Alexandra Mariel 01 August 2016 (has links) (PDF)
Transcatheter aortic heart valve replacement (TAVR) is a procedure to replace a failing aortic valve and is becoming the new standard of care for patients that are not candidates for open-heart surgery [2]. However, this minimally invasive technique has shown to cause ischemic brain lesions, or “silent infarcts”, in 90% of TAVR patients, which can increase the patient’s risk for stroke by two to four times in future years [3]. Claret Medical Inc., a medical device company, has developed a cerebral protection system that filters and captures embolic debris released during endovascular procedures, such as TAVR. This thesis utilized CT scans from Claret Medical to create a physical construct of the aortic arch to experimentally validate a theoretical computer model through flow visualization. The hypothesis was that the empirical model can accurately mimic the fluid dynamic properties of the aortic arch in order validate an in silico model using the finite elements program COMSOL MultiPhysics® Modeling Software. The physical model was created from a patient CT scan of the aortic arch using additive manufacturing (3D printing) and polymer casting, resulting in the shape of the aortic arch within a transparent, silicone material. Fluid was pumped through the model to visualize and quantify the velocity of the fluid within the aortic arch. COMSOL MultiPhysics® was used to model the aortic arch and obtain velocity measurements, which were statistically compared to the velocity measurements from the physical model. There was no significant difference between the values of the physical model and the computer model, confirming the hypothesis. Overall, this study successfully used CT scans to create an anatomically accurate physical model that was validated by a computer model using a novel technique of flow visualization. As TAVR and similar procedures continue to develop, the need for experimental evaluation and visualization of devices will continue to grow, making this project relevant to many companies in the medical device industry.
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Modifikace struktury křemíkových solárních článků / Modification of silicon solar cells structureStrachala, Dávid January 2014 (has links)
The aim of the work is to create a coherent overview of the silicon monocrystaline solar cell in terms of the physical principle of the structure and sequence of technological operations necessary for its production. The effect of individual manufacturing steps is discussed in relation to the requirement of decreasing recombination, optical and ohmic losses of the monocrystalline solar cell. Due to a theoretical assumption, one-dimensional model of solar cell was created in a PC1D software that was later optimized to achieve the highest possible efficiency. Using the available technologies, final model of the solar cell is manufactured in Solartec company and in the end of the work compared with the output of simulation.
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Low power steering electrodes within microfluidic channels for blood cancer cell separation for MRD applicationsSuryadevara, Vinay Kumar 12 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / In this study, a novel model for manipulating cancer blood cells based on multi-stage micro channels under varied low field concepts is proposed. Steering Device approach was followed to manipulate the cancer cells based on their various differential potentials across their membranes. The proposed approach considers the size and the surface potential as well as the iso electronic structure of the cells. These research objectives emphasize the separation of the cells in the blood stream, and differentiates various blood cells and tumors for further analysis within the microfluidic channels. The dimensions of the channel sets the required electric field for manipulating the cancer cells within the channels using low electrode voltage function. The outcomes of this research may introduce a new diagnostic approach of finding the minimum residual disease (MRD) scans, early detection and analysis scans. This thesis provides a mathematical model, detailing the theory of the cell sorting device, manipulating the blood cancer cells and design of the device structure are also detailed, leading to the optimum research parameters and process. A Computer Aided Design (CAD) was used to model the multi-cell sorting lab-on-chip device, details of hardware and software were used in the simulation of the device various stages. Reverse engineering to configure the potentials for sorting mechanism needs is discussed. The thesis work also presents a comparative study of this sorting mechanism and the other commercially available devices. The practical model of the proposed research is laid out for future consideration.
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Thermal energy management and chemical reaction investigation of micro-proton exchange membrane fuel cell and fuel cell system using finite element modellingMcGee, Seán January 2015 (has links)
Fuel cell systems are becoming more commonplace as a power generation method and are being researched, developed, and explored for commercial use, including portable fuel cells that appear in laptops, phones, and of course, chargers. This thesis examines a model constructed on inspiration from the myFC PowerTrekk, a portable fuel cell charger, using COMSOL Multiphysics, a finite element analysis software. As an educational tool and in the form of zero-dimensional, two-dimensional, and three-dimensional models, an investigation was completed into the geometric construction, air conditions and compositions, and product materials with a best case scenario completed that summarizes the results identified. On the basis of the results of this research, it can be concluded that polyoximetylen and high-density polyethylene were considered as possible materials for the majority of the product, though a more thorough investigation is needed. Air flow of above 10 m/s, air water vapour mass fraction below 50% and initial temperature between 308K and 298K was considered in this best scenario. Suggestions on future expansions to this project are also given in the conclusion.
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Modelování elektromagnetického pole ve tkáni / Elektromagnetic field mapping in tissuePort, Martin January 2013 (has links)
This thesis is an introduction to the modeling of electromagnetic fields in the tissue and is focused on the knowledge of electromagnetic field theory. Maxwell's equations and their solutions are described the spread of plane waves in the environment. It also discusses the exposure limit values of specific absorbed power and hygienic limits based on the standards in force in the Czech Republic on health protection against nonionizing radiation in accordance with Government Regulation No. 106/2010 Coll. It also deals with the software interface in COMSOL Multiphysics 4.2 for solving physical modeling and simulation. There is mention of the RF module, which is used for modeling. Work mentions in detail about the menu of the program and the most important part - the Model Builder.
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Modelování prvků pro bioelektroniku / Modelling of bioelectronic devicesTruksa, Jan January 2018 (has links)
Tématem této práce je počítačové modelování organického elektrochemického tranzistoru (OECT). Pro vytvoření modelu bylo třeba vypočítat rozložení elektrického pole a koncentrace iontů elektrolytu. Výpočet byl proveden numericky pomocí metody konečných prvků. Bylo vypočítáno rozložení elektrického potenciálu na povrchu kanálu OECT, dále byly vypočítány změny vodivosti a výstupní proud OECT. Výpočty byly provedeny na osobním počítači pomocí komerčního softwaru COMSOL Multiphysics. Kvůli nedostatečnému výpočetnímu výkonu musel být model rozdělen na části a drasticky zjednodušen. Prezentované výsledky se liší od literatury, protože se nepodařilo správně modelovat saturaci tranzistoru. Odchylky od reálného chování OECT jsou pravděpodobně způsobeny zjednodušením modelu.
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Senzor pro měření průtoku / Flow sensorSymerský, Tomáš January 2011 (has links)
This diploma thesis is divided into two parts - theoretical and practical. In its first, theoretical part, deals with the theory of fluid and gas flow, heat transfer and diversification of sensors for flow measurement working on the electrical principle. It also deals with thermodynamic principle, which can be used for measuring very small flow and low-temperature ceramics that is used to implement microcanals for sensing very low flows. The practical part of the thesis deals with the very simulation of the entire structure in the program “COMSOL Multiphysics” - both in 2D and 3D views. Then there is shown the implementation and measurement of the flow sensor in a low-temperature ceramics, working on a thermodynamic principle.
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