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Roman, Federico. "Large eddy simulation tool for environmental and industrial processes." Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3210.
Повний текст джерелаComputational Fluid Dynamics (CFD) is an established tool for consulting and for basic research in fluid mechanics. CFD is required to provide information where analytical approaches or experiments would be impossible or too expensive. Most of the flows of engineering interest are turbulent. Turbulence is an unresolved problem of classical physics, because of the non linearity of the fluid motion equations. At the moment the only way to face them is numerically. Turbulence is composed of eddies in a broad range of size. To solve numerically the Navier-Stokes equations, the equations set that governs the fluid motion, a very fine grid is necessary in order to catch also the smallest eddies. The computational cost increases as Re3 (Re = ul/ is the Reynolds number with u and l an inertial velocity and length scales and the kinematic viscosity). Real life problems are characterized by very large Reynolds numbers and the consequent computational cost is enormous. So the direct solutions of Navier-Stokes equations (DNS) is not feasible. In many applications it is not necessary to solve all the eddies, it can be sufficient to supply the effects of unresolved scale to the flow. In Large Eddy Simulation (LES) most of the scales of motion are directly solved, in particular all the large energy carrying scales. These scales are influenced by the boundaries and they are strongly anisotropic. The smaller and dissipative scales must be modeled, but these scales loosing memory of the boundary conditions are more isotropic and hence formulating a general model that accounts for their effect is relatively easier. Large Eddy Simulation is a prospective tool for investigation in real life problems, in particular when high detailed analysis is required. This is the case for many industrial and environmental processes. For example, acoustic problems due to hydrodynamic noise are governed over a range of large scales which are easily reproduced by LES solution. However in these types of flows many difficulties arise also for LES. In general these flows are characterized by high Reynolds number. Wall-bounded flow at high Re requires high computational cost because LES is constrained to be DNS-like. Besides complex geometries are often involved. Structured or Unstructured body-fitted grid can be very hard to made, moreover unstructured grid can be expensive and not suited for LES. Scope of this thesis is to develop tools to apply LES to such configurations in order to make numerical simulation more adaptable to real life problems. In particular to deal with complex geometry an Immersed Boundary Methodology has been developed for curvilinear coordinates. The method has been applied to several test cases with good results. Then this methodology has been extended to high Reynolds number flows through the use of a wall model. In order to work on anisotropic grid, typical in sea coastal domain, a modified Smagorisky model has been proposed. Finally particle dispersion has been considered in stratified environmental flow. These tools has been applied to an industrial and to an environmental problem with good results.
La fluidodinamica computazionale (CFD) ´e uno strumento affermato per le consulenze e per la ricerca di base nella meccanica dei fluidi. Alla CFD ´e richiesto di fornire informazioni quando approcci analitici o sperimentali sarebbero impossibili o troppo costosi. La maggior parte dei flussi di interesse ingegneristico ´e di tipo turbolento. La turbolenza ´e uno dei problemi irrisolti della fisica classica, ci´o ´e dovuto alla non linearit´a delle equazioni che governano il moto dei fluidi. Al momento l’unico modo per affrontarle ´e numericamente. La turbolenza si compone di vortici di diverse dimensioni. Per risolvere numericamente le equazioni di Navier-Stokes, le equazioni che governano il moto dei fluidi, una griglia molto fine ´e necessaria al fine di simulare propriamente anche i vortici di scala pi´u piccola. Il costo computazionale cresce come Re3 (Re = ul/ ´e il numero di Reynolds, con u e l una velocit´a ed una lunghezza scala caratteristici e la viscosit´a cinematica). I problemi reali sono caratterizzati da numeri di Reynolds altissimi e conseguentemente il costo computazionale di queste simulazioni ´e enorme. Per questo motivo la soluzione diretta delle equazioni di Navier-Stokes (DNS) non ´e possibile. In molte applicazioni non ´e necessario risolvere tutte le scale dei vortici, pu´o essere sufficiente fornire l’effetto delle scale non risolte al flusso. Nella Large Eddy Simulation gran parte delle scale di vortici ´e direttamente risolta, in particolare le larghe scale energetiche. Queste scale sono influenzate dalle condizioni al contorno e sono fortemente anisotrope. Le scale piccole e dissipative devono essere modellate, ma queste scale perdendo memoria delle condizioni al contorno sono generalmente isotrope ed un modello per riprodurre il loro effetto risulta semplice. La LES ´e uno strumento d’avanguardia per lo studio di flussi realistici, in particolare risulta molto potente quando vengono richieste analisi dettagliate del moto. Questo ´e il caso di molti problemi in campo industriale ed ambientale. Per esempio problemi acustici dovuti a rumore idrodinamico sono governati dalle grandi scale che nella LES sono facilmente riprodotte. Comunque anche per la LES sorgono molte difficolt´a nel affrontare questi problemi. Generalmente questi flussi sono caratterizzati da alti numeri di Reynolds. Flussi di parete ad alti Re richiedono un costo computazionale elevatissimo e alla fine la LES deve soddisfare a requisiti tipici della DNS. Inoltre spesso questi flussi sono caratterizzati da geometrie complesse. Griglie strutturate o non strutturate che si adattano alle geometrie possono essere molto difficili da sviluppare, inoltre le griglie non strutturate possono essere molto costose e non particolarmente adatte alla LES. Lo scopo di questa tesi ´e di sviluppare degli strumenti atti a rendere efficiente l’applicazione della LES a flussi realistici. In particolare per affrontare le geometrie complesse ´e stata sviluppata una metodologia Immersed Boundary per coordinate curvilinee. Il metodo ´e stato provato su diversi casi con buoni risultati. La metodologia ´e stata quindi estesa al caso di flussi ad alto numero di Reynolds tramite lo sviluppo di un modello parete. ´E stato quindi sviluppato un modello modificato di Smagorinsky per lavorare con griglie fortemente anisotrope, tipiche per flussi in ambito marino costiero. Infine ´e stata studiata la dispersione di particelle in flussi ambientali stratificati. Gli strumenti sviluppati sono stati quindi applicati ad un problema industriale ed ad uno ambientale con ottimi risultati.
XXI Ciclo
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PASINATO, HUGO DARIO. "TURBULENCE IN WALL REGION MODELING." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1998. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19290@1.
Повний текст джерелаNeste trabalho são apresentados de uma pesquisa orientada à modelagem da turbulência de baixos números de Reynolds. Com esse objetivo foi caracterizado o escoamento turbulento de baixos números de Reynolds na região viscosa vizinha a uma parede, na base de dados experimentais e correlação empírica. Sobre essa caracterização foi feita uma análise dos valores médios de interesse para modelos de turbulência de duas equações, a qual permitiu obter conclusões sobre o comportamento da turbulência de baixos Reynolds e propor modelos para a mesma. Essa modelagem implica em fornecer um fechamento para a equação de dissipação de energia cinética turbulenta e uma expressão para a viscosidade efetiva da turbulência, na região viscosa. O fechamento da equação de dissipação foi feito analisando os termos fontes de vorticidade, usando resultados prévios da ordem de grandeza relativa dos mesmos. A equação de dissipação obtida desse modo não contém funções de amortecimento. Com relação à expressão proposta para calcular a viscosidade efetiva de turbulência, considera-se que a transferência de quantidade de movimento devido à turbulência pode ser obtida em função da energia cinética do escoamento médio. Considera-se que a modelagem proposta é uma complementação para modelos de turbulência de duas equações, para simular zonas de baixos Reynolds incluídos os casos em sub-camada logarítmica aparente. Problemas de escoamentos turbulentos com cisalhamento médio com diferentes características, usualmente utilizadas para avaliar modelos de turbulência, foram usados como testes. Como resultados relevantes desta pesquisa, considera-se o fato de se usar em forma sistemática informação experimental para o desenvolvimento de modelos de turbulência, a obtenção de um fechamento para a equação de dissipação sem funções de amortecimento e uma expressão para a viscosidade da turbulência na região viscosa. No caso da viscosidade da turbulência, a expressão proposta permite obter a distribuição da velocidade média na região amortecedora, apresentando boa concordância com dados experimentais.
This thesis presents the results of research work aiming at low Reynolds turbulence modeling. For an stablished boundary layer turbulent low Reynolds flow in the viscous layer near a wall was characterized based on experimental data and empirical polynomials. On this basis an analysis of the distribuition of the mean values in the near-wall region was performed allowing for the proposal of a low Reynolds turbulence model within a two-equation model methodolgy. The low Reynolds proposal involves a closure to the dissipation equation and the proposal of an effective turbulence viscosity expression. The dissipation equation closure like as the effective viscosity proposal were made based on previous results of scale time rate analysis through the viscous region. On the other hand, the effective turbulence viscosity expression allows for the representation of the Reynolds stress as a function of mean flow kinetic energy. The low Reynolds turbulence modeling proposal can be seen as a complementation of two eqaution models for low Reynolds turbulence. The model was tested in several case tests of turbulent flow with different kind of mean shear, frequently used for turbulence model assessment. As main results of this work can be mentioned the systematic use of experimental data to build, analyze and test turbulence models; the closure of the dissipation equation without damping functions and the turbulence effective viscosity expression for the viscous region. This last proposed relation allows for the attainment of a mean velocity distribuition profile in the buffer region, which adequately fits experimental data.
Lubchenko, Nazar. "Near-wall modeling of bubbly flows." Thesis, Massachusetts Institute of Technology, 2018. https://hdl.handle.net/1721.1/121709.
Повний текст джерелаThesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2018
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 119-127).
Multiphase computational fluid dynamics (M-CFD) codes are gaining acceptance in the nuclear industry for the prediction of thermal-hydraulic behavior, offering the potential to improve the operation, economics, and safety of current systems, and enhance the design of next generation reactors. The common approach when applying M-CFD methods to the bubbly flow regime is to use an Eulerian-Eulerian two-fluid model, which solves for averaged mass and momentum equations for liquid and gas phases, as well as the k-epsilon turbulence model with modifications to account for the presence of bubbles. The resulting partial differential equations require well-posed boundary conditions, with special treatment at the walls, where there exist strong gradients of all variables. The present work systematically addresses the boundary conditions at solid walls for turbulent bubbly flows.
The complete coupled problem involving six variables is decoupled into three separate tasks, which consider void fraction profile, turbulent quantities, and gas velocity near the wall. Based on available experimental data it is shown that the reduction in void fraction near the wall is a consequence of the bubble shape, and not the wall lubrication effect repelling bubbles from the wall. Aiming at restoring the correct profile, a new wall force is derived from consideration of the interfacial forces balance near the wall. Its performance is evaluated through simulations of bubbly pipe flow experiments, confirming its improvements when compared to previous models. Three phenomena, namely, bubble-induced turbulence, buoyancy of gas, and displacement of liquid by gas, are speculated to have effect on the near-wall turbulent boundary layer.
These effects are incorporated in the Analytical Wall Functions (AWF), which provide quantitative treatment of these bubble effects in the boundary layer. The boundary layer model is validated on the existing experimental data, and the AWF are assessed based on simulations of bubbly pipe flow experiments, as well as at the prototypical reactor conditions. It is demonstrated that most of the effects that arise due to bubbles in the boundary layer can be neglected, and consequently, single phase wall functions can be used in numerical simulations. Finally, through analysis of experimental data, it is suggested that the relative velocity between bubbles and the surrounding liquid does not remain constant throughout the domain in the Eulerian-Eulerian representation of the flow, but instead increases near the wall. A corresponding correction to the drag coefficient is proposed and validated against the experimental data.
by Nazar Lubchenko.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Nuclear Science and Engineering
Calafell, Sandiumenge Joan. "Efficient wall modeling for large eddy simulations of general non-equilibrium wall-bounded flows." Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/667230.
Повний текст джерелаEl principal objectiu d’aquesta tesi ha estat contribuir al desenvolupament de metodologies relacionades amb wall modeling aplicat a Large Eddy Simulations (LES) de fluxos de paret, especialment per a números de Reynolds alts. Aquesta configuració de flux es troba en un ampli número d’aplicacions industrials. Tot i això, donada la naturalesa de les capes límit, la resolució numèrica acurada d’aquest tipus de flux de manera rutinària és inviable. La tècnica de wall modeling pretén reproduir els efectes de la capa límit interna sense necessitat de resoldre-la explícitament. Això permet la resolució de fluxos de paret a alts números de Reynolds amb una fracció del cost que tindria si la capa límit interna fos resolta tant des d’un punt de vista espacial com temporal. Aquest treball està format per sis capítols. El primer és una introducció a la dinàmica de fluids computacional (CFD en les seves sigles en anglès), des de les metodologies més acurades i generals, fins a les tècniques més específiques i simplificades. Al segon capítol s’introdueixen les magnituds físiques rellevants que s’han d’analitzar per a avaluar i confirmar la fiabilitat d’una determinada simulació numèrica CFD d’alta fidelitat. Es consideren tant els aspectes espacials com temporals, els quals són fonamentals per a la correcta resolució d’un flux turbulent. Al tercer capítol es presenta un model de paret Two-Layer per a fluxos de no-equilibri i geometries complexes. Els models wall shear stress en general i els models basats en RANS en particular, estan afectats per els problemes de “log-layer mismatch” i “resolved Reynolds stresses inflow”, que deterioren la qualitat de les prediccions numèriques. El model proposat incorpora un filtre temporal a la interfície entre el model de paret i el domini LES, el qual suprimeix els dos errors comentats prèviament amb un sol pas de baix cost computacional. Fins ara, la eliminació d’aquests dos errors es duia a terme amb tècniques separades que en alguns casos eren complexes i costoses des d’un punt de vista computacional. A més a més, es proposa una metodologia per a la determinació de la longitud de filtre temporal òptima, la qual és validada tant en condicions d’equilibri com de no-equilibri. La nova tècnica està basada en l’obtenció de l’espectre de freqüències de la velocitat, el qual revela les característiques de les escales temporals del flux en la regió propera a la paret. Segons els resultats obtinguts en els tests, es conclou que per als models Two-Layer basats en RANS, les freqüències més altes que el límit entre el rangs energy-containing i inercial, s’han de filtrar. En el capítol quatre es presenta el model matemàtic del Two-Layer model basat en les equacions URANS. A més a més, es detalla la metodologia numèrica utilitzada per a la seva resolució a través del mètode dels volums finits. Al capítol cinc es presenta la implementació del model numèric presentat al capítol quatre. El model desenvolupat en aquesta tesi és un solver de CFD complert basat en les equacions URANS. Donat que el principal objectiu del wall modeling és la reducció de costos computacionals, és necessària una implementació eficient del model. És per això que la eficiència paral·lela del codi implementat s’analitza a través d’un strong scalability test. En aquestes proves es determina el bon comportament del codi, encara que s’identifiquen punts en els que es pot optimitzar la implementació actual. Finalment, a l’últim capítol es presenten les conclusions generals del treball. A més a més, s’hi inclouen un seguit de propostes sobre futures línies de recerca dirigides aprofundir en les conclusions obtingudes durant la realització del present estudi.
Krank, Benjamin [Verfasser], Wolfgang A. [Akademischer Betreuer] Wall, Wolfgang A. [Gutachter] Wall, and Claus-Dieter [Gutachter] Munz. "Wall Modeling via Function Enrichment for Computational Fluid Dynamics / Benjamin Krank ; Gutachter: Wolfgang A. Wall, Claus-Dieter Munz ; Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1180602099/34.
Повний текст джерелаPajayakrit, Palanunt. "Turbulence modeling for curved wall jets under adverse pressure gradient." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ26861.pdf.
Повний текст джерелаKamel, Sherif I. (Sherif Ibrahim). "Mathematical modeling of wet flashover mechanism of HVDC wall bushings." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28792.
Повний текст джерелаThe random processes associated with the wetting dynamics and pattern as well as the air gaps breakdowns are accounted for in a novel statistical approach to model the flashover process of the HVDC wall bushings under the proposed mechanism.
The work is supported by an experimental investigation into surface resistance and minimum flashover stress of full scale HVDC wall bushings under nonuniform rain.
The findings of the model have been satisfactorily compared with experiments and field observations and can for the first time account for the following aspects of flashover mechanism: critical dry zone length, polarity effect, specific leakage length, wet layer conductance, dry zone position as well as DC system voltage. The model was also used to assess the performance of RTV coated bushings and to compare the strength or an SF$ sb6$ bushing to that of a conventional oil-paper design under nonuniform rain.
Pajayakrit, Palanunt Carleton University Dissertation Engineering Mechanical and Aerospace. "Turbulence modeling for curved wall jets under adverse pressure gradient." Ottawa, 1997.
Знайти повний текст джерелаMensah-Gourmel, Johanne. "Modeling biodegradable stents and their effect on the arterial wall." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX034/document.
Повний текст джерелаToday, sent deployment is the most common treatment for symptomatic atherosclerosis. Bioresorbable stents (BRS) are based on the premise that a stent is needed only until arterial wound healing occurs after which it would be desirable for the stent to degrade so that the arterial wall recovers its natural compliance. Deployment of a stent profoundly alters the mechanical environment in the arterial wall, and these alterations play an important role in regulating the incidence of complications such as restenosis and neointimal hyperplasia. In the case of a BRS, the mechanical stresses in both the stent and the arterial wall evolve as the stent degrades. Furthermore, the hydrolysis-driven degradation of the stent can be accelerated by mechanical stresses in the stent, an additional coupling that needs to be taken into account. We are interested in determining the evolution of stresses in both the stent and the arterial wall during the stent deployment and degradation process and in elucidating the effect of these stresses on the stent degradation and on the remodeling process in the wall, which would also be influenced by the loss of endothelial cells and the amount of inflammation induced by the stent deployment and degradation. To this end, we have developed a 3D finite element model of the deployment and degradation of a polylactic acid (PLA) BRS that integrates the coupling between the stent and the artery.This allows one to predict the zones of dismantling of the stent and the evolution of the arterial thickness in response to a BRS stenting procedure. Since the model relies strongly on parameters that need to be determined experimentally, we became interested in developing methods to follow stent degradation. With this aim, we used optical coherence tomography (OCT) to image several BRS that were deployed into tubes and allowed to degrade in a saline solution at 37°C over a period of two years. We subsequently developed a versatile method for automatically detecting stent struts on the OCT images and quantifying the strut gray scale intensity. The results suggest that this automated method of OCT image analysis represents a promising tool to quantitatively assessing BRS degradation states. Lastly, we were interested in establishing the ability of a stented artery to adapt to a modification in its wall shear stress. Studying the in vivo evolution of the lumen of stented mini-swine arteries followed by OCT imaging allowed us to demonstrate that whereas a bare metal stent cages the artery, a BRS, presumably due to its degradation-induced dismantling, frees the vessel and enables it to adapt its lumen diameter in order to decrease its absolute level of shear stress and the compliance mismatch with the unstented portion of the artery. This lumen adaptation allowed by the stent dismantling could be taken into account in future computational models
Sjölinder, Emil. "Spray and Wall Film Modeling with Conjugate Heat Transfer in OpenFOAM." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-84487.
Повний текст джерелаThiele, Roman. "Mechanistic Modeling of Wall-Fluid Thermal Interactions for Innovative Nuclear Systems." Doctoral thesis, KTH, Reaktorteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-177370.
Повний текст джерелаNästa generations kärnkraftverk (GEN-IV) kan inte bara producera el på ett pålitligt, säkert och hållbart sätt, utan det kan också reducera mängden kärnavfall, som har producerats under tiden som man använt nuvarande generationen kärnkraftverk, genom att transmutera avfallen. Framtidens kärnkraftverk använder andra kylmedel än nuvarande kraftverk som t.ex. flytande bly, gas eller superkritiskt vatten. Det betyder att många beräkningsverktyg måste testas, utvecklas och förbättras så att man kan genomföra termohydrauliska designberäkningar. Den här avhandlingen omfattar två olika kylmedel, flytande bly och superkritiskt vatten, som har ett Prandtl-tal som skiljer sig från 1 och kommer att användas i GEN-IV reaktorer. Studien undersöker olika strategier för att modellera turbulens som Large Eddy Simulation (LES) och Reynolds-Averaged Navier-Stokes (RANS) och hur man kan använda dessa strategierna i beräkningar av strömning och värmetransfer i den nya kylvätskan. Undersökningen visar att RANS turbulensmodeller delvis kan förutsäga värmeöverföringen vid en vägg i en ringformad strömningsgeometri. Förbättringar av förutsägelsen ska vara möjlig genom användning av avancerade strategier för turbulensmodellering, t.ex. termiska turbulensmodeller. En stor prestandajämförelse för värmeöverföring i superkritiskt vatten visade att ingen av nuvarande strategier för turbulensmodellering kan förutsäga försämrad värmeöverföring i en 7-stavknippet under superkritiskt tryck. Nya modeller, som omfattar de starka flytkrafterna och den snabba förändringen av den molekulära Prandtl-tal vid väggen som uppstår när vätskan går genom pseudokritiska punkten, måste utvecklas. Avancerade väggfunktioner är en av strategierna som kan ta hänsyn till dessa fenomen. Väggfunktioner kan inte bara hjälpa till att modellera de typer av flöden som behövs utan kan också hjälpa till att sänka beräkningstiden med en eller två tiopotenser. Olika avancerade väggfunktioner i open-source beräkningsverktyget OpenFOAM implementerades och deras prestation i sub- och superkritiska vattenflödar värderades. Baserat på detta rekommenderas Gerasimovs modell för ytterligare utredning. Dessutom läggs olika strategier fram för att utöka modellens validitet till flöde med superkritiskt vatten i sammanband med försämrad och förbättrad värmeöverföring. Kunskap om beteendet av temperatur och hastighet i väggens närhet är viktigt för väggens integritet, detta då väggen även påverkar beteendet. Väggens termiska tröghet påverkar flödets temperatur och hastighet. Dock är ett ännu viktigare problem, som kan uppträda, är att temperaturfluktuationer kan framkalla termisk utmattning i en vägg. Med användning av LES utreds termisk blandning av varmt och kallt vatten i en simplifierad modell av ett styrstavsledrör, inklusive temperaturfältet i styrstaven och ledrörsväggen. Användningen av WALE LES-turbulensmodellen gör det möjligt att utföra beräkningar i den komplexa geometrin, detta eftersom modellen anpassar sig automatiskt till fenomenen nära väggen utan användning av ad-hoc funktioner. LES resultaten för alla värden som är viktiga för att bestämma utmattningsbeteende, som amplitud och frekvens av temperaturfluktuationer i väggens närhet och i väggen själv, är i god överensstämmelse med resultaten från experiment från KTH i samma geometri.Kunskapen som vunnits genom ovannämnda utredningar användes för att optimera den termohydrauliska designen av en liten, pool-typ GEN-IV reaktor som är passivt kyld med flytande bly. Reaktorn är designad som en utbildnings- och träningsreaktor och optimeringen genomfördes med hjälp av 3D CFD. Beräkningarna genomfördes på en fjärdedel av reaktorns hela geometrin. Regioner med små detaljer, som de åtta värmeväxlarna och reaktorns kärna, modellerades genom porösa material. Det visar sig att för att ha en optimal kylning av kärnan, utan att förändra reaktorns globala geometri, måste förhållandet mellan tryckförlust i reaktorkärnan och värmeväxlarna vara nära 1. Detta uppnås genom att designa plattan vid ingången till kärnan så att tillräckligt med bly flödar genom kärnan utan att kväva flödet i denna. Ytterligare en förbättring i reaktorkylningen uppnås genom att reducera värmeförlusten genom väggen som skiljer varm och kall vätska. Detta görs med en strategi som förekommer i gasturbinteknologin, genom att man lägger till ett tunt skikt av termiskt isolerande material på väggen, som reducerar värmeöverföring med ungefär 50%.
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Rausch, Sophie [Verfasser], Wolfgang A. [Akademischer Betreuer] Wall, and Markus [Akademischer Betreuer] Böl. "Computational and Experimental Modeling of Lung Parenchyma / Sophie Rausch. Gutachter: Wolfgang A. Wall ; Markus Böl. Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2012. http://d-nb.info/1025150422/34.
Повний текст джерелаPfaller, Martin [Verfasser], Wolfgang A. [Akademischer Betreuer] Wall, Wolfgang A. [Gutachter] Wall, and Dominique [Gutachter] Chapelle. "Predictive Computational Modeling of Patient-Specific Cardiac Mechanics / Martin Pfaller ; Gutachter: Wolfgang A. Wall, Dominique Chapelle ; Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1190818744/34.
Повний текст джерелаIsmail, Mahmoud [Verfasser], Wolfgang A. [Akademischer Betreuer] Wall, and Perumal [Akademischer Betreuer] Nithiarasu. "Reduced Dimensional Modeling of the Entire Human Lung / Mahmoud Ismail. Gutachter: Wolfgang A. Wall ; Perumal Nithiarasu. Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1068315776/34.
Повний текст джерелаLi, Jinxia. "Lubricating grease Experiments and modeling of wall-bounded- and free-surface flows." Doctoral thesis, Luleå tekniska universitet, Maskinelement, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26489.
Повний текст джерелаGodkänd; 2014; 20141017 (jinlit); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Jinxia Li Ämne: Maskinelement/Machine Elements Avhandling: Lubricating Grease Experiments and Modellingo f Wall-Bounded and Free-Surface Flours Opponent: Professor Arto Lehtovaara, University of Technology, Tampere, Finland Ordförande: Professor Erik Höglund, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Fredag den 19 december 2014, kl 09.00 Plats: E632, Luleå tekniska universitet
Gil, Edward Matthew. "Computational Modeling of Glass Curtain Wall Systems to Support Fragility Curve Development." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/94051.
Повний текст джерелаMaster of Science
Performance-based engineering (PBE) can allow engineers and building owners to design a building envelope for specific performance objectives and strength/serviceability levels, in addition to the minimum design loads expected. These envelope systems benefit from PBE as it improves their resiliency and performance during natural multi-hazard events (i.e. earthquakes and hurricanes). A useful PBE tool engineers may utilize to estimate the damages an envelope system may sustain during an event is the fragility curve. Fragility curves allow engineers to estimate the probability of reaching a damage state (i.e. glass cracking, or glass fallout) given a specified magnitude of an engineering demand parameter (i.e. an interstory drift ratio during an earthquake). These fragility curves are typically derived from the results of extensive experimental testing of the envelope system. However, computational simulations can also be utilized as they are a viable option in current fragility curve development frameworks. As it’s popularity amongst owners and architects was evident, the architectural glass curtain wall (CW) was the specific building envelope system studied herein. Glass CWs would benefit from implementing PBE as they are very susceptible to damages during earthquakes and hurricanes. Therefore, the goal of this computational research study was to develop fragility curves based on the analytical results obtained from the computational simulation of glass CW systems, which could aid in multi-hazard PBE design of CWs. As v opposed to utilizing limited, small experimental data sets, these simulations can help to improve the accuracy and decrease the uncertainties in the data required for fragility curve development. To complete the numerical simulations, 3D finite element (FE) models of a glass CW system were generated and validated against experimental tests. 11 multi-panel CW system configurations were then modeled to analyze their effect on the glass CW’s performance during in-plane and out-of-plane loading simulations. These parametric configurations included changes to the: equivalent clamping load, glass thickness, and glass-to-frame clearance. Fragility curves were then generated and compared to the single panel CW fragility curves derived experimentally within the FEMA P-58 Seismic Fragility Curve Development study. The fragility curves within FEMA P-58 were determined to be more conservative since they are based on single panel CWs. These fragility curves do not consider: the effects of multiple glass panels with varying aspect ratios; the possible component interactions/responses that may affect the extent of damages; and the continuity of the CW framing members across multiple panels. Finally, a fragility dispersion study was completed to observe the effects of implementing different levels of uncertainty and dispersion in the fragility curves based on analytical results.
Bair, Shawn D. "Computational Modeling of the Electrical Sensing Properties of Single Wall Carbon Nanotubes." Youngstown State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1441813278.
Повний текст джерелаHabteyes, Firdaweke. "Modeling Acute Changes in Bladder Wall Tension, Shape and Compliance During Filling." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3537.
Повний текст джерелаHörmann, Julia Maria [Verfasser], Wolfgang A. [Akademischer Betreuer] Wall, Wolfgang A. [Gutachter] Wall, and Björn H. [Gutachter] Menze. "Multiphysics Coupled Computational Modeling in Cardiac Electromechanics / Julia Maria Hörmann ; Gutachter: Wolfgang A. Wall, Björn H. Menze ; Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1186889403/34.
Повний текст джерелаRoth, Christian J. [Verfasser], Wolfgang A. [Akademischer Betreuer] [Gutachter] Wall, and Marcel [Gutachter] Filoche. "Multi-dimensional Coupled Computational Modeling in Respiratory Biomechanics / Christian J. Roth ; Gutachter: Wolfgang A. Wall, Marcel Filoche ; Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1140165925/34.
Повний текст джерелаLEE, KWANGDEOK. "QUANTIFYING BARRIERS TO MACROMOLECULAR TRANSPORT IN THE ARTERIAL WALL." Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1152557910.
Повний текст джерелаValsecchi, Pietro. "Temporal Numerical Simulations of Turbulent Coanda Wall Jets." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195025.
Повний текст джерелаChung, Daniel Pullin Dale Ian Pullin Dale Ian. "Numerical simulation and subgrid-scale modeling of mixing and wall-bounded turbulent flows." Diss., Pasadena, Calif. : California Institute of Technology, 2009. http://resolver.caltech.edu/CaltechETD:etd-05292009-123828.
Повний текст джерелаAdvisor name found in the Acknowledgments pages of the thesis. Title from home page (viewed 05/04/2010). Includes bibliographical references.
Barp, Stefan. "Numerical prediction of horizontal, thermally unstably stratified, turbulent wall flows by RANS modeling /." Zürich, 2005. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16016.
Повний текст джерелаPapadimitriou, Andreas. "Modeling, Identification and Control of a Wall Climbing Robot Based on Vortex Actuation." Thesis, Luleå tekniska universitet, Drift, underhåll och akustik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70626.
Повний текст джерелаGupta, Ankit. "Multi-Scale Modeling of Mechanical Properties of Single Wall Carbon Nanotube (SWCNT) Networks." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1022.
Повний текст джерелаBarrows, Richard James. "Two Dimensional Finite Element Modeling of Swift Delta Soil Nail Wall by "ABAQUS"." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4741.
Повний текст джерелаKormendy, Imre, and Mustafa Muwaili. "Timber Shear Wall Analysis : Parameterized Finite Element Modelling." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-77199.
Повний текст джерелаMahmud, Khan Raqib. "Sensitivity Analysis of Near-Wall Turbulence Modeling for Large Eddy Simulation of Incompressible Flows." Thesis, KTH, Numerisk analys, NA, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-146098.
Повний текст джерелаVäggmodellering är viktigt i simuleringar av turbulenta flöden ikomplexa geometrier då de mest inverkande flödesegenskaperna skakarakteriseras. Prestandan hos Large Eddy Simulation-tekniker med olikaväggmodeller analyseras för simuleringar av turbulenta flöden med höga Reynoldstal.Två alternativ som kan användas för turbulenta gränsskikt är “Wall Shear StressModel” och “Delayed Detached Eddy Simulation Wall Model”. I detta projektanvänds en wall shear stress modell för det turbulenta flödet vid väggentillsammans med G2 simuleringsmetodiken. En känslighetsanalys av denna modellmed hänsyn till modellparameterar presenteras för simuleringar avinkompressibla turbulenta flöden
Luo, Haoxiang. "The interaction of near-wall turbulence with compliant tensegrity fabrics : modeling, simulation, and optimization /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3144307.
Повний текст джерелаJayamon, Jeena Rachel. "Seismic Performance Assessment of Wood-Frame Shear Wall Structures." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/84902.
Повний текст джерелаPh. D.
Alaoui, Miloud. "Coherent structures and wall-pressure fluctuations modeling in turbulent boundary layers subjected to pressure gradients." Thesis, Paris, ENSAM, 2016. http://www.theses.fr/2016ENAM0077/document.
Повний текст джерелаThe flow around vehicles creates a turbulent boundary layer in the vicinity of the wall. The turbulent behavior induces pressure fluctuations that make the panels vibrate. These vibrations are then transmitted though the structure of the vehicle and radiate noise inside the cabin. The flow-induced noise levels increase with the speed of the vehicle. For this reason, aircraft manufacturers show a great interest in this topic.There are two objectives for this thesis: understand the mechanisms responsible for the wall-pressure fluctuations and predict this source of aircraft panel excitation.A study of available Large Eddy Simulation (LES) computations was performed. The database consists in simulations of turbulent boundary layer flows submitted to favorable, adverse and zero pressure gradients. This is necessary to understand the nature of the flow over curved geometries such as the aircraft flight deck. The effect of pressure gradients on coherent hairpin structures and hairpin packets could be identified and quantified based on visualization and statistical analysis methods. Linear stochastic estimation of the velocity fields revealed a pair of counter-rotating streamwise vortices above hairpin packets. These vortices have a vorticity opposite to that of the hairpins and an “inverse hairpin” model was proposed.Following the work of Ahn et al. (2010), a stochastic model for wall-pressure spectrum was developed. The idea is to build a stochastic turbulent velocity field using hairpin packets which are subjected to a mean flow. The characteristics of the packets depending on the pressure gradient are based on the analyses of the LES database. The pressure field at the wall is obtained by solving a Poisson equation. The results of the hairpin packet model are compared to numerical and experimental data. Finally, the model is used as input for a Statistical Energy Analysis (SEA) simulation in order to predict the levels of vibrations of panels submitted to a turbulent boundary layer flow over a portion of an aircraft cabin
Golshan, Roozbeh. "Residual-based Variational Multiscale LES with Wall-modeling for Oceanic Boundary Layers in Shallow Water." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5489.
Повний текст джерелаWiechert, Lena [Verfasser], Gerhard A. [Akademischer Betreuer] Holzapfel, and Wolfgang A. [Akademischer Betreuer] Wall. "Computational Modeling of Multi-Field and Multi-Scale Phenomena in Respiratory Mechanics / Lena Wiechert. Gutachter: Gerhard A. Holzapfel ; Wolfgang A. Wall. Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2011. http://d-nb.info/1013436458/34.
Повний текст джерелаMetzke, Robert [Verfasser], Wolfgang A. [Akademischer Betreuer] Wall, and Mohammad R. K. [Akademischer Betreuer] Mofrad. "Modeling and experimental investigation of the mechanobiological environment associated with alveolar pneumocytes / Robert Metzke. Gutachter: Wolfgang A. Wall ; Mohammad R. K. Mofrad. Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1064695000/34.
Повний текст джерелаLaing, Jeffrey M. "Finite Element Modeling and Validation of a Novel Process for Extruding Thin Wall Hollow Copper Profiles." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1327333357.
Повний текст джерелаHazer, Dilana [Verfasser]. "Automated Patient-Specific Modeling of Blood Flow and Vessel Wall Mechanics in Aortic Pathology / Dilana Hazer." München : Verlag Dr. Hut, 2010. http://d-nb.info/100948530X/34.
Повний текст джерелаWu, Ai. "Etudes comparatives des architectures des reseaux locaux et implementation du protocole x. 25 sur ibm pc." Paris, ENST, 1987. http://www.theses.fr/1987ENST0017.
Повний текст джерелаVaal, Michael Hamman de [Verfasser], Wolfgang A. [Akademischer Betreuer] Wall, Ulrich A. [Akademischer Betreuer] Stock, and Michael W. [Akademischer Betreuer] Gee. "Computational modeling, clinical comprehension and improvement of aortic manipulation / Michael Hamman de Vaal. Betreuer: Wolfgang A. Wall. Gutachter: Wolfgang A. Wall ; Ulrich A. Stock ; Michael W. Gee." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1079323937/34.
Повний текст джерелаMaier, Andreas [Verfasser], Wolfgang A. [Akademischer Betreuer] Wall, C. Alberto [Akademischer Betreuer] Figueroa, and Hans-Henning Georg Ulrich [Akademischer Betreuer] Eckstein. "Computational Modeling of Rupture Risk in Abdominal Aortic Aneurysms / Andreas Maier. Gutachter: C. Alberto Figueroa ; Wolfgang A. Wall ; Hans-Henning Georg Ulrich Eckstein. Betreuer: Wolfgang A. Wall." München : Universitätsbibliothek der TU München, 2012. http://d-nb.info/103626243X/34.
Повний текст джерелаAndrae, Johan. "Wall Related Lean Premixed Combustion Modeled with Complex Chemistry." Doctoral thesis, KTH, Kemiteknik, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3455.
Повний текст джерелаQC 20100504
Wang, Jin. "Modeling of concrete dehydration and multhiphase transfer in nuclear containment concrete wall during loss of cooling accident." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30098/document.
Повний текст джерелаNuclear power plant now takes an important part in the world's electricity generation. In human history, there have already been two tragic accidents in Chernobyl and Fukushima causing severe radioactive matter leakage. To pre- vent this kind of accident from happening again, concrete structure plays an important role as material of containment building, which is the last barrier to isolate the radioactive matter from the environment. Hence, the transfer properties of concrete under severe circumstances, especially high tempera- ture, are important for this usage. This PhD thesis aims to investigate the behavior of the concrete under high temperature up to 200°C. In the first part, a dehydration model was proposed. The model consists of different dehydration sub-models for main hydrates in the cement paste. In the second part, the dehydration model was implemented in a thermo-hygral model. The thermo- hygral model was then used to simulate a mock-up for which experimental results are available in the literature, without considering the mechanical behaviors. At last, parametric studies were performed to investigate the influ- ence of some parameters, and the model was then applied to structures under different heating rates, and structures with different thicknesses to compare the temperature and gas pressure profiles across a wall
Wells, Jesse Buchanan. "Effects of Turbulence Modeling on RANS Simulations of Tip Vortices." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34343.
Повний текст джерелаMaster of Science
Andersson, Johan, and Oscar Wyckman. "Modeling of Fuel Dynamics in a Small Two-Stroke Engine Crankcase." Thesis, Linköpings universitet, Fordonssystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119061.
Повний текст джерелаFör alla tvåtaktsmotorer med bränslematning genom vevhuset är bränsledynamiken svårpredikterad. Detta beror på att bränslet måste passera vevhusvolymen innan det når förbränningskammaren. Denna uppsats handlar om utveckling av en modell som ger realistisk dynamik för bränslet i tvåtaktsmotorers vevhus. Vevhusmodellen i denna uppsats har två delar. Den ena delen är en modell för bränslefilm på motorväggar och den andra delen är en modell för koncentration av förångat bränsle i vevhusvolymen. Bränslefilmsmodellen har två parametrar som måste trimmas. Den ena är andelen bränsle från förgasaren som inte förångas direkt och den andra är tidsåtgången för förångning av bränslefilmen. Uppsatsen behandlar trimning av dessa parametrar genom körning av modellen med indata från mätningar. Eftersom inte all indata kan mätas behövs även modeller för dessa. Därför behandlar uppsatsen även utveckling av enkla modeller för luftflöde, bränsleflöde, gasblandning i avgasvolymen och beteende hos den för mätningar använda λ-sonden. Parameterestimeringen för vevhusmodellen som är gjord i denna uppsats resulterar i parametrar som svarar mot konstant andel av bränslet från förgasaren som förångas direkt och en förångningshastighet för bränslefilmen som ökar med ökande motorhastighet. Parameterestimeringen är gjord med mätdata från normal körning vid tre olika motorhastigheter. Giltigheten för modellen är begränsad till dessa hastigheter och kan inte appliceras på körning av motorn vid kallstart. Modellen är körd och jämförd med valideringsdata från olika körfall. Modellen förutser dynamiska beteenden väl, men har ett systematiskt fel gällande medelvärdet på λ. Eftersom detta medelvärde beror på förhållandet mellan luftflöde och bränsleflöde in i vevhuset är sannolikt detta systematiska fel en effekt av osäkerhet i de enkla modeller som utvecklats för dessa flöden.
Maurya, Abhilasha. "Computational simulation and analytical development of Buckling Resistant Steel Plate Shear Wall (BR-SPSW)." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/34466.
Повний текст джерелаMaster of Science
Faisal, Md Tanvir. "A multiscale approach to mechancial modeling of a leaf petiole: integrating cell wall, cellular tissues, and structural morphology." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121448.
Повний текст джерелаUne plante est une structure hiérarchique naturelle, qui présente des propriétés mécaniques remarquables. Les propriétés mécaniques à grande échelle d'une plante sont le résultat cumulatif des propriétés structurelles du niveau précédent de la hiérarchie structurelle. Pour développer des structures de génie inspirées par une plante et ses organes, une caractérisation détaillée de ses propriétés mécaniques manifestées aux multiples niveaux hiérarchiques est essentielle pour imiter ces structures pour les applications d'ingénierie. Cette thèse présente un ensemble de modèles théoriques et numériques à divers niveaux hiérarchiques structuraux afin de capturer les propriétés structurelles aux niveaux globaux d'un pétiole d'une plante. La méthode de modélisation est cadrée au sein d'un système mécanique à niveaux multiples, qui est essentiel pour toute structure composée de plusieurs ordres hiérarchiques d'organisation. Les propriétés structurelles à grande échelle, c.à.d. la raideur en flexion et en torsion, d'un pétiole d'une plante sont obtenues par la corrélation entre la construction de la paroi cellulaire, la microstructure des tissus, et la morphologie de la forme structurelle. La raideur de la paroi cellulaire est modélisée en utilisant la théorie des matériaux composites à renfort fibreux. La microarchitecture des constituants des tissus qui gouverne les propriétés du pétiole est modélisée avec un nouveau algorithme – La tessellation de Voronoi de centre à bord fini (FECVT) - qui est capable de fournir une visualisation réaliste du tissu. La raideur effective des constituants des tissus est obtenue par la méthode des éléments finis des modèles FECVT accouplée avec les propriétés de la paroi cellulaire. La forme du pétiole en coupe transversale au niveau structural ensemble avec les propriétés des tissus sont considérées afin de déterminer sa raideur en flexion et en torsion, qui sont également validés expérimentalement pour le pétiole de la rhubarbe. Ce modèle mécanique à échelles multiples éclaircira le rôle de chaque niveau de la hiérarchie structurelle pour déterminer la souplesse structurelle du pétiole. Une méthode de modélisation hiérarchique qui capture les propriétés structurelles globales d'un pétiole a été introduite dans cette thèse. Notamment, le modèle établit une relation entre les propriétés du micro et macro niveaux structuraux en utilisant un procédé mécanique adapté, à échelles multiples. Par conséquent, cette recherche peut combler le vide entre la biologie végétale et le génie afin de développer de nouveaux matériaux et des structures bio-inspirées. Cette recherche peut également aider à développer les connaissances fondamentales de la biomécanique cellulaire des plantes et son impact sur la mécanique macroscopique des tiges et des pétioles avec l'objectif final de transférer ces connaissances pour le traitement et la conception des structures et matériaux souples de génie.
Almohammed, Naser [Verfasser]. "Modeling and Simulation of Particle Agglomeration, Droplet Coalescence and Particle-Wall Adhesion in Turbulent Multiphase Flows / Naser Almohammed." Hamburg : Helmut-Schmidt-Universität, Bibliothek, 2018. http://d-nb.info/1153126729/34.
Повний текст джерелаSchrottenbaum, Ines. "Influence of Wall Biofilm on Pathogen Transport in Water Distribution Systems. Modeling Estimates Derived from Synthetic Biofilm Experiments." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1427812859.
Повний текст джерелаSharma, Abhinav. "ESTIMATING THE EFFECTS OF BLASTING VIBRATIONS ON THE HIGH-WALL STABILITY." UKnowledge, 2017. https://uknowledge.uky.edu/mng_etds/38.
Повний текст джерелаBen, Nasr Ouissem. "Numerical simulations of supersonic turbulent wall-bounded flows." Phd thesis, INSA de Rouen, 2012. http://tel.archives-ouvertes.fr/tel-01059805.
Повний текст джерела