The thesis deals with solving the time dependent inverse heat conduction and heat transfer problem of the quenching process of a rotary solid cylinder by multiple impinging water jets. The development of such investigation consists of two parts that complement each other. As is the case of any scientific experiment, first of all, an initial hypothesis will be set to be demonstrated theoretically. The numerical validation is carried out with a series of artificial cooling curve data and sensitivity analyses in the inverse solution. Then, a series of recorded temperature data were implemented into the inverse solution to predict the surface heat transfer during the quenching process.The numerical study consists of the solution of a two-dimensional linear time dependent inverse heat conduction problem based on the Generalized Minimal Residual Method (GMRES). The inverse solution method is based on the solution of an iterative problem, validated by a set of artificial temperature data. Such solution allows the prediction of the surface temperature and heat flux distribution in the quenching process, making use of recorded internal temperatures of the specimen. In order to solve the problem, the Matlab and Comsol Multiphysics programs were used. The GMRES algorithm was written as Matlab code, while the computational domain was defined in Comsol Multiphysics. Moreover, both programs collaborated in the solution of the inverse problem. Once the problem was solved, a sensitivity analysis was carried out in order to study the dependence of the numerical result on various parameters and optimize the inverse solution setup for application of recorded experimental data.The validated inverse solution setup examined by the sensitivity analyses was used on a set of experimental data, allowing the demonstration of the initially proposed hypothesis. This sensitivity analyses were performed consecutively for different key parameters regarding the numerical definition of the problem. The values for the parameters were considered optimal when minimum values for the error of the predicted surface temperature were recorded. In this case, the analyzed parameters were the m-value, mesh cell size, effect of noise, initial quenching temperature and quenching cooling rate. The connection between the experimental and numerical studies is obvious, as the first oneprovides the latter with input data of the inner temperature data of the specimen for the solving of the inverse problem, as is the case of the practical application of the code developed in the present thesis, and the inverse solution is essential in order to predict thesurface temperature and heat flux that are key information in studying quenching systems.

In many situations, fluid flows can exhibit a wide range of temporal and spatial phenomena. It has become common to extract physically important features, called modes, as a first step in the analysis of flows with high complexity. One of the most prominent modal analysis techniques in the context of fluid dynamics is Proper Orthogonal Decomposition (POD), which enables extraction of energetically coherent structures present in the flow field. This method does, however, suffer from the lack of connection with the mathematical theory of dynamical systems and its utility in the analysis of arbitrarily complex flows might therefore be limited. In the present work, we instead consider application of the Koopman Mode Decomposition (KMD), which is an approach based on spectral decomposition of the Koopman operator. This technique is employed for modal analysis of the incompressible, two-dimensional ow past two side-by-side cylinders at Re = 60 and with a non-dimensional cylinder gap spacing g* = 1. This particular configuration yields a wake ow which exhibits in-phase vortex shedding during finite time, while later transforming into the so-called flip-flopping phenomena, which is characterised by a slow, periodic switching of the gap ow direction during O(10) vortex shedding cycles. The KMD approach yields modal structures which, in contrary to POD, are associated with specific oscillation frequencies. Specifically, these structures are here vorticity modes. By studying these modes, we are able to extract the ow components which are responsible for the flip-flop phenomenon. In particular, it is found that the flip-flop instability is mainly driven by three different modal structures, oscillating with Strouhal frequencies St1 = 0:023, St2 = 0:121 and St3 = 0:144, where it is noted that St3 = St1 + St2. In addition, we study the in-phase vortex shedding regime, as well as the transient regime connecting the two states of the flow. The study of the in-phase vortex shedding reveals| - not surprisingly - the presence of a single fundamental frequency, while the study of the transient reveals a Koopman spectrum which might indicate the existence of a bifurcation in the phase space of the flow field; this idea has been proposed before in Carini et al. (2015b). We conclude that the KMD offers a powerful framework for analysis of this ow case, and its range of applications might soon include even more complex flows.

Closed-loop combustion control is an on-going field of research for improving reducing engine emissions and increasing efficiency. Cylinder pressure is a key parameter to monitor for combustion feedback. Measuring pressure with a transducer is an option, although being able to estimate the pressure based on the crank angle measurement instead would be beneficial in terms of costs. A virtual crank angle based pressure sensor was therefore developed within this thesis. It was studied how the in-cylinder pressure trace for a full closed cycle could be modelled from a pressure trace from a rigid crankshaft model, the angular velocity measurement and heat release modelling. The pressure trace from the crankshaft model was subjected to a singularity at TDC and torsional oscillations, it was therefore of interest to study whether the singularity could be avoided by modelling the heat release. Further on, the indicated work and total heat released during combustion were estimated from the angular velocity measurements as they are important parameters for determining the heat release trace.   It was found that the indicated work could be approximated by comparing the kinetic power trace, obtained from the measured angular velocity, with the piston power trace, estimated using isentropic pressure curves for the compression and expansion within the cylinder. Accurate results were obtained for operating points at 800 rpm while large deviations were seen for higher speeds as a consequence of larger torsional effect on the angular velocity trace; on the form of perturbed oscillations. The results could be improved from local averaging of the kinetic power trace at the occasions of deceleration, although it could be concluded that only the low speed operating were still accurate enough.   The kinetic power trace was attempted to be corrected for torsional power using angular displacement estimations of the crankshaft nodes from a dynamic crankshaft model. Even though the model seemed to capture the torsional behaviour at parts of the cycle, the oscillations could not be completely removed and it was determined that the final work estimate could not be improved from the torsional power estimate. The torsion was further studied regarding frequency and amplitude of the oscillations within the angular velocity and acceleration trace. No clear relations between the torsional behaviour and operating speed and load could be concluded. Further, since inversion of the dynamic crankshaft model for pressure estimation resulted in an improper solution since before, the model was iterated instead. The pressure trace could thereby be derived accounting for torsion, however the trace still contained oscillations which highlights the challenge of estimating the torsion accurately. The torsion is a complex phenomenon to describe and further development of a model for estimating the torsion with high accuracy for all operating points would improve the virtual pressure sensor significantly.   The heat release was, as a first step, modelled as isochoric and isobaric. These models gave information of the limits of SOC by comparing the indicated work from the resulting pressure trace with the work estimate from the angular velocity measurement. Further, one Wiebe function was parametrised such that the resulting pressure derivative during late combustion was adapted to the trace from the crankshaft model in a least-square sense. This allowed for better adaption as the partial pressure trace was subjected to torsional oscillations. The fitted Wiebe function described the diffusive combustion well but missed out the shape of the premixed combustion. Lastly, a double Wiebe function parametrisation was done where the diffusive combustion function was fitted to the late combustion data and the premixed combustion function was adapted such that the resulting indicated work matched the estimated work. To receive more accurate results, the premixed SOC and duration had to be approximated beforehand from the kinetic power trace. The virtual pressure sensor and most of the sub models were most accurate for low speed operating points. It was concluded that the reason is most probably the torsional effect on the input data to all sub models. It was shown that the crankshaft model can be complemented with heat release estimations which improved the final pressure trace and removed the singularity present around TDC. / Förbränningsåterkoppling är ett aktuellt forskningsområde inom utvecklingsarbetet för att minska utsläpp och öka verkningsgraden hos förbränningsmotorer. Cylindertryck är en viktig parameter att mäta . Ett alternativ är att använda en tryckgivare men det skulle vara mer kostnadseffektivt att kunna uppskatta trycket baserat på vevvinkeln som redan idag mäts i motorer. Därav utvecklades en virtuell sensor för uppskattning av cylindertrycket genom detta examensarbete. Studien har berört hur tryck spår, bitvis noggranna för kompressionen och expansionen, från en stel vevaxelmodell kan kompletteras med modeller för värmeavgivningen från förbränningen för att erhålla ett fullt tryck spår. För att kunna bygga och utveckla modellerna utvecklades en metod för att bestämma det indikerade arbetet baserat på den uppmätta varvtalssignalen som beror mycket på hur förbränningen skett och är därmed en viktig parameter vid modellerande av värmeavgivningen.   Det indikerade arbetet kunde uppskattas genom att jämföra den kinetiska effekten med den effekt som kolvarna totalt bidrog med. Det upptäcktes att offseten mellan kurvorna motsvarade effekten av förlusterna och lasten som därmed kunde bestämmas vid de punkter där momentet från cylindrarna var i jämvikt. Den kinetiska effekten beräknades från varvtalssignalen medan effekten från kolvarna uppskattades genom att använda isentropiska tryckkurvor för kompressionen och expansionen, innan och efter förbränningen respektive. Relativt noggranna resultat erhölls för arbetspunkterna med ett varvtal på 800 rpm medan större avvikelser inträdde vid högre varvtal. Anledningen till detta var att torsionssvängningar influerade varvtalssignalen mer vid högre varvtal. Resultaten kunde förbättras genom lokal medelvärdesbildning av den kinetiska effekten vid de decelerationer som sker efter förbränningen i respektive cylinder. II   Torsionens inverkan på vevaxelns dynamik uppskattades genom att använda estimeringar av förvridningen av vevaxeln från en dynamisk vevaxelmodell. Uppskattningen tycktes vara tillräckligt noggrann inom vissa intervall men det var inte möjligt att avlägsna torsionssvängningarna i kinetiska effektspåret för hela cykeln. Uppskattningen av indikerat arbete kunde därför inte förbättras genom denna torsionsuppskattning. Torsionen var vidare studerad i form av frekvens och amplitud av svängningarna inom varvtalssignalen. Inga tydliga samband kunde säkerställas mellan svängningarna och arbetspunkternas varvtal och last. Detta tyder på att torsionen är för komplex att förutse. Vidare, då invertering av den dynamiska vevaxelmodellen tidigare visat sig ge en oriktig lösning kunde modellen istället itereras för att bestämma tryck spåret likt tidigare gjort för den stela vevaxelmodellen. Torsionssvängningarna influerade dock fortfarande det resulterande tryck spåret. Det finns stor potential att förbättra den virtuella sensorn om torsionen kan uppskattas noggrant för alla arbetspunkter.   Värmeavgivningen från förbränning var först modellerad som isochorisk och isobarisk i två respektive modeller. Dessa modeller gav information om gränsvärdena för tändningen genom att finna den tändning för modellerna som resulterade i samma arbete som det tidigare estimerade indikerade arbetet. Därefter anpassades en Wiebe funktion så att den resulterande tryckderivatan minsta-kvadrat anpassades till tryckderivatan från vevaxelmodellen under den sena förbränningen där vevaxelmodellen var mest noggrann. Wiebe funktion gav en bra anpassning till den senare diffusiva förbränningen men var inte tillräcklig för att beskriva den förblandade förbränningen. Slutligen anpassades två Wiebe funktioner där den diffusiva förbränningen anpassades likt för singel Wiebe-funktions anpassningen medan den förblandade förbränningen anpassades så att det resulterande arbetet stämde med det uppskattade indikerade arbetet. För att få bättre resultat bestämdes den förblandade förbränningens start och duration från uppskattningen av den kinetiska effekten innan anpassningen.   Den virtuella trycksensorn och de flesta av dess delmodeller var mest noggranna för arbetspunkterna vid låga varvtal. Slutsatsen var att det var främst på grund av torsionssvängningarnas påverkan på insignalerna till delmodellerna som noggrannheten föll för de högra varvtalen. Genom denna studie visades det att deltrycksspåret från vevaxelmodellen kunde kompletteras med en modell för värmeavgivningen för att slutligen få en bättre uppskattning av hela tryck spåret där singulariteten vid TDC kunde undvikas.

Closed-loop combustion control is an on-going field of research for improving reducing engine emissions and increasing efficiency. Cylinder pressure is a key parameter to monitor for combustion feedback. Measuring pressure with a transducer is an option, although being able to estimate the pressure based on the crank angle measurement instead would be beneficial in terms of costs. A virtual crank angle based pressure sensor was therefore developed within this thesis. It was studied how the in-cylinder pressure trace for a full closed cycle could be modelled from a pressure trace from a rigid crankshaft model, the angular velocity measurement and heat release modelling. The pressure trace from the crankshaft model was subjected to a singularity at TDC and torsional oscillations, it was therefore of interest to study whether the singularity could be avoided by modelling the heat release. Further on, the indicated work and total heat released during combustion were estimated from the angular velocity measurements as they are important parameters for determining the heat release trace. It was found that the indicated work could be approximated by comparing the kinetic power trace, obtained from the measured angular velocity, with the piston power trace, estimated using isentropic pressure curves for the compression and expansion within the cylinder. Accurate results were obtained for operating points at 800 rpm while large deviations were seen for higher speeds as a consequence of larger torsional effect on the angular velocity trace; on the form of perturbed oscillations. The results could be improved from local averaging of the kinetic power trace at the occasions of deceleration, although it could be concluded that only the low speed operating were still accurate enough. The kinetic power trace was attempted to be corrected for torsional power using angular displacement estimations of the crankshaft nodes from a dynamic crankshaft model. Even though the model seemed to capture the torsional behaviour at parts of the cycle, the oscillations could not be completely removed and it was determined that the final work estimate could not be improved from the torsional power estimate. The torsion was further studied regarding frequency and amplitude of the oscillations within the angular velocity and acceleration trace. No clear relations between the torsional behaviour and operating speed and load could be concluded. Further, since inversion of the dynamic crankshaft model for pressure estimation resulted in an improper solution since before, the model was iterated instead. The pressure trace could thereby be derived accounting for torsion, however the trace still contained oscillations which highlights the challenge of estimating the torsion accurately. The torsion is a complex phenomenon to describe and further development of a model for estimating the torsion with high accuracy for all operating points would improve the virtual pressure sensor significantly. The heat release was, as a first step, modelled as isochoric and isobaric. These models gave information of the limits of SOC by comparing the indicated work from the resulting pressure trace with the work estimate from the angular velocity measurement. Further, one Wiebe function was parametrised such that the resulting pressure derivative during late combustion was adapted to the trace from the crankshaft model in a least-square sense. This allowed for better adaption as the partial pressure trace was subjected to torsional oscillations. The fitted Wiebe function described the diffusive combustion well but missed out the shape of the premixed combustion. Lastly, a double Wiebe function parametrisation was done where the diffusive combustion function was fitted to the late combustion data and the premixed combustion function was adapted such that the resulting indicated work matched the estimated work. To receive more accurate results, the premixed SOC and duration had to be approximated beforehand from the kinetic power trace. The virtual pressure sensor and most of the sub models were most accurate for low speed operating points. It was concluded that the reason is most probably the torsional effect on the input data to all sub models. It was shown that the crankshaft model can be complemented with heat release estimations which improved the final pressure trace and removed the singularity present around TDC. / Förbränningsåterkoppling är ett aktuellt forskningsområde inom utvecklingsarbetet för att minska utsläpp och öka verkningsgraden hos förbränningsmotorer. Cylindertryck är en viktig parameter att mäta . Ett alternativ är att använda en tryckgivare men det skulle vara mer kostnadseffektivt att kunna uppskatta trycket baserat på vevvinkeln som redan idag mäts i motorer. Därav utvecklades en virtuell sensor för uppskattning av cylindertrycket genom detta examensarbete. Studien har berört hur tryck spår, bitvis noggranna för kompressionen och expansionen, från en stel vevaxelmodell kan kompletteras med modeller för värmeavgivningen från förbränningen för att erhålla ett fullt tryck spår. För att kunna bygga och utveckla modellerna utvecklades en metod för att bestämma det indikerade arbetet baserat på den uppmätta varvtalssignalen som beror mycket på hur förbränningen skett och är därmed en viktig parameter vid modellerande av värmeavgivningen. Det indikerade arbetet kunde uppskattas genom att jämföra den kinetiska effekten med den effekt som kolvarna totalt bidrog med. Det upptäcktes att offseten mellan kurvorna motsvarade effekten av förlusterna och lasten som därmed kunde bestämmas vid de punkter där momentet från cylindrarna var i jämvikt. Den kinetiska effekten beräknades från varvtalssignalen medan effekten från kolvarna uppskattades genom att använda isentropiska tryckkurvor för kompressionen och expansionen, innan och efter förbränningen respektive. Relativt noggranna resultat erhölls för arbetspunkterna med ett varvtal på 800 rpm medan större avvikelser inträdde vid högre varvtal. Anledningen till detta var att torsionssvängningar influerade varvtalssignalen mer vid högre varvtal. Resultaten kunde förbättras genom lokal medelvärdesbildning av den kinetiska effekten vid de decelerationer som sker efter förbränningen i respektive cylinder. Torsionens inverkan på vevaxelns dynamik uppskattades genom att använda estimeringar av förvridningen av vevaxeln från en dynamisk vevaxelmodell. Uppskattningen tycktes vara tillräckligt noggrann inom vissa intervall men det var inte möjligt att avlägsna torsionssvängningarna i kinetiska effektspåret för hela cykeln. Uppskattningen av indikerat arbete kunde därför inte förbättras genom denna torsionsuppskattning. Torsionen var vidare studerad i form av frekvens och amplitud av svängningarna inom varvtalssignalen. Inga tydliga samband kunde säkerställas mellan svängningarna och arbetspunkternas varvtal och last. Detta tyder på att torsionen är för komplex att förutse. Vidare, då invertering av den dynamiska vevaxelmodellen tidigare visat sig ge en oriktig lösning kunde modellen istället itereras för att bestämma tryck spåret likt tidigare gjort för den stela vevaxelmodellen. Torsionssvängningarna influerade dock fortfarande det resulterande tryck spåret. Det finns stor potential att förbättra den virtuella sensorn om torsionen kan uppskattas noggrant för alla arbetspunkter. Värmeavgivningen från förbränning var först modellerad som isochorisk och isobarisk i två respektive modeller. Dessa modeller gav information om gränsvärdena för tändningen genom att finna den tändning för modellerna som resulterade i samma arbete som det tidigare estimerade indikerade arbetet. Därefter anpassades en Wiebe funktion så att den resulterande tryckderivatan minsta-kvadrat anpassades till tryckderivatan från vevaxelmodellen under den sena förbränningen där vevaxelmodellen var mest noggrann. Wiebe funktion gav en bra anpassning till den senare diffusiva förbränningen men var inte tillräcklig för att beskriva den förblandade förbränningen. Slutligen anpassades två Wiebe funktioner där den diffusiva förbränningen anpassades likt för singel Wiebe-funktions anpassningen medan den förblandade förbränningen anpassades så att det resulterande arbetet stämde med det uppskattade indikerade arbetet. För att få bättre resultat bestämdes den förblandade förbränningens start och duration från uppskattningen av den kinetiska effekten innan anpassningen. Den virtuella trycksensorn och de flesta av dess delmodeller var mest noggranna för arbetspunkterna vid låga varvtal. Slutsatsen var att det var främst på grund av torsionssvängningarnas påverkan på insignalerna till delmodellerna som noggrannheten föll för de högra varvtalen. Genom denna studie visades det att deltrycksspåret från vevaxelmodellen kunde kompletteras med en modell för värmeavgivningen för att slutligen få en bättre uppskattning av hela tryck spåret där singulariteten vid TDC kunde undvikas.

In order to study three-dimensional unsteady turbulent flow fields such as the wakes of bluff bodies, a Digital Particle Image Velocimetry (DPIV) system was developed. This system allows non-intrusive two-dimensional and time varying velocity measurements. Software and hardware modifications necessary to enhance the capabilities of the system were preformed, resulting in increased frequency resolution. However, due to hardware limitations and limitations inherited from the implementation of the method, space resolution is reduced. Subsequently, digital image processing tools to improve the space resolutions were developed. The advantages and limitations of the method for the study of turbulent flows are presented in detail. The developed system is employed in the documentation of time-varying turbulent flow fields. Initially we study the spanwise variation of the near wake of a low-aspect ratio, surface-mounted, circular cylinder piercing a free surface. The asymmetry of the end conditions combined with the natural unsteadiness of the vortex shedding generates a very complex flow filed which is difficult to study with conventional methods. By employing the aforementioned system we are able to reveal a departure of the two-dimensional character of the flow in the form of oblique vortex shedding. The effect of free surface on the vortex formation length and on the vortex reconnection process is documented. Near the free surface the alternate mode of vortex shedding is suppressed, leading to simultaneous shedding of vortices in the wake. Indications of vortex dislocations and change of the vortex axis in order to reconnect to the free surface are observed. Finally, a novel approach of reconstructing the three-dimensional, time -varying volume of the flow field by obtaining simultaneous measurements of Laser Doppler Velocimetry and Particle Image Velocimetry planes is presented. The same field is investigated with focus on the streamwise structures. Three-dimensional streamwise vortical structures are known to exist due to instabilities of plane shear layers. Similar streamwise vortices, also known as braid vortices have been observed in the past in the wake of circular cylinders with symmetric boundary conditions. The present spatio-temporal analysis demonstrated coexistence of two types of streamwise vortices in the wake, bilge and braid type of vortices. These may be due to the three dimensionality introduced by the free surface. In addition, the sufficient time resolution allowed the detection of the primary Von-Karman vortex through a plane of interrogation normal to the free stream, thus revealing the spanwise variation of the vortex shedding and its evolution at different downstream stations. The combination of the effect of the asymmetric boundary conditions with a free surface is investigated by adding one more source of three-dimensionality in terms of inclination of the cylinder axis. Hydrogen-bubble and particle-flow visualizations are preformed in combination with Laser-Doppler Velocimetry measurements. From both qualitative and quantitative results the effects of inclination and Froude number are documented. It is proved that the vortex shedding is suppressed for high values of the Froude number, however the inclination counteracts the vortex suppression and favors the vortex shedding mechanism. In addition, in the region of the no-slip boundary condition the flow is dominated by the effect of the horseshoe vortex. The case of a three-dimensional separated flow over a surface-mounted prism is investigated using a modified version of the system. The character of the separated from the leading edge corner shear layer and the formed separation bubble are documented in space and time along the mid-plane of symmetry of the body. Three different flows corresponding to different Reynolds numbers are studied. The unsteadiness of the flow is presented indicating a pseudo-periodic character. Large-scale, low-frequency oscillations of the shear layer that have been observed in the past using point measurement methods are now confirmed by means of a whole field velocity measurement, technique allowing a holistic view of the flow. In addition, the unsteadiness of the point of reattachment is associated with the flapping of the shear layer and the shedding of vorticity in the wake. Finally, it is demonstrated that the apparent vortex shedding mechanism of such flows is dependent on the interaction of the primary vortex of the separation bubble with a secondary vortex formed by the separation of the reverse flow boundary layer. By performing measurements with such time and space resolution the inadequacy of time averaged or point measurement methods for the treatment of such complex and unsteady flow fields becomes evident. In final case we employ Particle-Image Velocimetry to show the effect of unsteady excitation on two-dimensional separated flow over a sharp edged airfoil. It is proved that such an approach can be used to effectively control and organize the character of the flow, potentially leading to lift increase and drug reduction of bluff bodies / Ph. D.

[pt] Diante dos cenários de produção cada vez mais desafiadores, a indústria de petróleo tem sido forçada a expandir os limites operacionais para vazões, temperaturas e pressões mais elevadas. Como consequência, cenários mais rigorosos são encontrados, levando à redução da vida útil dos equipamentos atuais, como por exemplo, a falha prematura por fadiga de linhas de controle de poços com completação inteligente. Estas linhas encontram-se expostas ao escoamento turbulento na região anular da coluna de produção, causando vibrações e tensões suficientemente altas, podendo levar a uma falha prematura das linhas por fadiga. Para prevenir estes problemas e desenvolver projetos mais eficientes, é necessário investigar os fenômenos associados a interação da vibração da linha com os desprendimentos de vórtices do escoamento. Estes foram modelados utilizando-se a metodologia DDES (Delayed Detached Eddy Simulation), o que requer alto custo computacional, devido à necessidade de utilização de pequenos passos de tempo e de espaçamento de malha. Buscando reduzir o custo computacional para a modelagem do problema, propõe-se, neste trabalho, tratar de forma desacoplada a análise estrutural e de fluidodinâmica. As forças atuantes nas linhas de controle no espaço anular do poço de completação são obtidas desprezando-se a flexibilidade das linhas. Paralelamente, o fator de amortecimento crítico, necessário para a análise estrutural da vibração da linha, é obtido através de uma simulação Fluido- Estrutura de um escoamento cruzado a um cilindro elástico. Os resultados obtidos mostram que a presente metodologia é promissora, pois permite uma representação dos fenômenos envolvidos melhor do que a encontrada nos procedimentos atualmente disponíveis na literatura. / [en] In face of increasingly challenging production scenarios, the oil industry has been forced to expand operational limits to higher flow rates, temperatures, and pressures. Therefore, challenging production scenarios are found, from integrity standpoint, leading to reduction in current equipment life expectancy. Premature failure of control lines due to fatigue in wells with intelligent completion is one of the problems that arises from those extreme conditions. These lines are exposed to turbulent flow in the annular region of the production string, causing sufficiently high vibrations and stresses. These dynamic stresses can lead to premature failure of the lines due to fatigue. To prevent these problems, and to develop more efficient designs, it is necessary to investigate the phenomena associated with the interaction of the line vibration with the vortex shedding of the flow. We modeled the phenomena using the DES (Delayed Detached Eddy Simulation) methodology, which has high computational cost due to the need of using small time steps and high mesh refinement. In order to reduce these computational costs, this work proposes to deal with structural and fluid dynamics analysis in a decoupled way. The forces acting on the control lines in the annular space of the completion well are obtained neglecting the flexibility of the lines. In parallel, the critical damping factor, necessary for the structural vibration analysis of control lines, is obtained through a Fluid-Structure Interaction (FSI) simulation of an elastic cylinder subjected to cross flow. The results obtained show that the present methodology is promising, allowing a better representation of the involved phenomena, compared to procedures currently available in the literature.

Controlling the temperature of the exhaust valves is paramount for proper functioning of engines and for the long lifespan of valve train components. The majority of the heat outflow from the valve takes place along the valve-seat-cylinder head-coolant thermal path which is significantly influenced by the thermal contact resistance (TCR) present at the valve/seat and seat/head interfaces. A test rig facility and experimental procedure were successfully developed to assess the effect of the valve/seat and seat/head interfaces on heat outflow from the valve, in particular the effects of the valve/seat interface geometry, seat insert assembly method, i.e. press or shrink fit, and seat insert metallic coating on the operating temperature of the valve. The results of tests have shown that the degree of the valve-seat geometric conformity is more significant than the thermal conductivity of the insert: for low conforming assemblies, the mean valve head temperature recorded during tests on copper-infiltrated insert seats was higher than that recorded during tests on noninfiltrated seats of higher conformance. The effect of the insert-cylinder head assembly method, i.e. shrink-fitted versus press-fitted inserts, has proved negligible: results have shown insignificant valve head temperature variations, for both tin-coated and uncoated inserts. On the other hand, coating the seat inserts with a layer of tin (20-22¿m) reduced the mean valve head temperature by approximately 15°C as measured during tests on uncoated seats. The analysis of the valve/seat and seat/head interfaces has indicated that the surface asperities of the softer metal in contact would undergo plastic deformation. Suitable thermal contact conductance (TCC) models, available in the public domain, were used to evaluate the conductance for the valve/seat and seat/cylinder head interfaces. Finally, a FE thermal model of the test rig has been developed with a view to assess the quality of the calculated TCC values for the valve/seat and seat/head interfaces. The results of the thermal analysis have shown that predicted temperatures at chosen control points agree with those measured during tests on thermometric seats with an acceptable level of accuracy, proving the effectiveness of the used TCC models.

This study focuses on multi-jet impingement for gas turbine geometries in which the objective is to understand the influence of the roughness elements on a target surface to the heat transfer. Current work has proven that implementing roughness elements for multi-jet impingement target surfaces has increased heat transfer ranging anywhere from 10-30%. This study has chosen to investigate three different roughness elements, elliptical in cross-section, to compare to smooth surface geometries for multi-jet impingement. An experimental was taken for this study to extend the current knowledge of multi-jet impingement geometries and to further understand the heat transfer performance. A temperature sensitive paint (TSP) technique was used to measure the heat transfer on the target surface, in which the local temperature was measured to estimate area averaged heat transfer coefficient (HTC) and row averaged HTC. In order stay consistent with literature, non-dimensional parameters were used for geometry locations and boundaries. For this study, the Reynolds number range, based on jet diameter and mass flux, is 10-15k. The X/D (streamwise direction), Y/D (spanwise direction), Z/D (channel height direction), L/D (thickness of the jet plate) constraints for this study are 5, 6, 3, and 1 respectively. From the local heat transfer distributions of the different roughness elements, it is concluded that the inclusion of these elements increases heat transfer by 2-12% as compared to a flat/smooth target plate. It is therefore recommended from this study, that elements, elliptical in shape, provide favorability in heat transfer for gas turbine configurations.

No description available.

No description available.