This report documents the adaptation of a two dimensional two phaseNavier-Stokes solver to axisymmetric problems. The changes fromCartesian to cylindrical coordinates are thoroughly described with finitedifference methods for the heat equation, Poisson equation, singleand two phase Navier-Stokes equations.The jump conditions at interfacesare modified to accommodate these changes for the two phaseNavier-Stokes equations.The changes to the solver are done step by step, and every changeis verified through intermediate test cases with analytical solutions tolimit the possible sources of errors.Finally all stepwise changes are joined together to form an axisymmetrictwo phase Navier-Stokes solver. Results are presented for aresting bubble, and for both viscous and inviscid oscillating ellipticbubbles.

A hyperelastic-viscoplastic material model intended for thermoplastics has been developed by SIMLab at NTNU. This model formed the basis of the thesis, where a material model for the polymer polypropylene was calibrated and validated. Four rounds of material testing were carried out. Tension and compression tests formed the basis for a calibration of the material model. Two different component tests were used for validation; stretching of a plate with a hole and plate impact tests.The calibrated model was implemented as a user-defined material model in the non-linear finite element code LS-DYNA, and numerical simulations of the tension and compression tests were carried out in order to verify the calibrated parameters. The component tests were numerically simulated with the purpose of controlling the ability of the model to predict the behaviour of the material when subjected to more complex loading cases.The calibrated material model was able to capture the main characteristics of the experimental tests. The model does, however, have limitations, as it was not able to correctly predict all strain rate effects of the material at high strain rates, like viscoelasticity. A partly recalibration of the material model was carried out to enable the model to predict the material’s behaviour at high strain rates.

Denne rapporten tar for seg validering av en hyperelastisk – viscoplastisk material modell som tidligere har blitt implementert i elementmetode koden LS – Dyna. Materialet som er evaluert er polyetylen (HDPE) som er levert av det tyske firmaet SIMONA. Material parameterne som er satt inn i den konstitutive material modellen er funnet fra eksperimentell testing og kalibrering.Modellen er validert ved å sammenligne resultater av to veldefinerte eksperimentelle tester ved numeriske forutsigelser. Det har blitt utført tester på plate med hull. Platene har en mer kompleks geometri grunnet hullet i platen, og vil derfor gi mer komplekse spenning og tøynings tilstander. I tillegg har platene veldefinerte randbetingelser. Disse har en mer komplisert sammensetning av trykk og strekk og vil derfor være mer realistiske, da en virkelig komponent brukt i industrien vil bli utsatt for både trykk og strekk samt påført last av ulike hastigheter. De eksperimentelle og simulerte testene er sammenlignet og evaluert i valideringskapittelet. Modellen fanger opp de viktigste egenskapene observert i testene.

This thesis is a practical application of Systems Engineering in a full-scale project. The author has participated as a member of NTNU's Eco-marathon team, who has spent the last two semesters designing and manufacturing an energy-efficient car for the Shell Eco-marathon competition 2012. The author made an assessment of the project to find the areas where he should focus his effort. The author also applied Lean Thinking to find the Systems Engineering methods that would best aid the team improve within the areas uncovered in the assessment. The areas where the team needed improvement were Knowledge management and Continuous improvements of the product development process. By using Model-based Systems Engineering processes the author produced a system model acting as a knowledge repository. Then, the author used methods from Lean Thinking for knowledge capture, namely Knowledge Briefs and learning events.For improving the product development process, the author introduced the team to Visual Workflow Management to help the team become more agile, and to visualize project progress from multiple perspectives in order to discover parts of the system which is not evolving at the desired rate.Key concepts in this thesis include:Lean Thinking, Lean Systems Engineering, Model-based Systems Engineering, Model-based Documentation, Knowledge management, Knowledge briefs, A3 method, system modelling, functional analysis, functional flow block diagrams (FFBDs), system architecture, Visual Workflow Management, Stand-up meetings, Visual project board, risk management

Simulations on liquid loads and flow rates which the Taitel-Dukler model predicts to have multiple solutions have been performed with ANSYS Fluent and LedaFlow. Both steady state and transient results in one, two and three dimensional flows are reported in this work. The hypothesis that the holdup of a pipe operated in the multiple solution region will be determined by the downstream holdup is investigated. Some results indicate that the hypothesized interface level gradients effects are correct.The Fluent steady state simulations had mass imbalance issues in addition to being both grid and geometry dependent, but produced results consistent with the independent Fluent transient simulations. The one dimension LedaFlow solver illustrated the effect shear stress modeling have on the multivalued solution region. The solver chose the intermediate solution for some flow rates, which by physical arguments can be excluded. The novel solver LedaFlow Q3D produced transient results displaying the wavy surface of the high holdup solutions. The results from the different models are deviating, but it is hard to predict which results are most the accurate since no comparison with experimental results have been conducted.

Aluminium is often treated as a homogeneous material. However, when investigated on a microscopic scale, a granular structure is observed. The mechanical properties of the constituents, together with the distribution of stresses and strains, determines the fracture toughness of the material.The objective of this master thesis was to investigate strain localization and fracture in aluminium on a microscopic scale. Relevant literature regarding fracture mechanisms was studied in order to determine which parameters influence the fracture toughness of aluminium. The distribution of effective plastic strain together with the stress triaxiality ratio is thought to give a prediction of the initiation of ductile fracture.A study of the microstructure of aluminium has been carried out. The aim of this study was to gain understanding of the mechanisms leading to the formation of a precipitate free zone (PFZ) near the grain boundary. Also the relation between the mechanical properties of the PFZ and the grain interior was studied. The literature study uncovered that the PFZ is expected to have a low yield stress and a high work hardening rate compared to the grain interior. A simplified numerical model representing a heterogeneous microstructure was developed. The aim of this model was to investigate the effect of certain parameters on the distribution of stresses and strains. The yield stress and work hardening rate of the PFZ as well as the global stress triaxiality, were all variables in a parameter study. A clear tendency of strain concentration in the PFZ was observed, which is consistent with the literature. For low global stress triaxiality, the PFZ oriented at an angle with respect to the external load was found to be the most likely location for initiation of intergranular fracture. Increasing the yield stress and work hardening rate of the PFZ was found to favor transgranular fracture.Due to long computational time, avoiding crystal plasticity analyses is of interest. Whether a material model using isotropic plasticity is able to give the same results as the crystal plasticity model has been investigated. The difference between the average effective plastic strain in the grain interior and in the PFZ was found to be lower using crystal plasticity than when using isotropic plasticity. Using crystal plasticity, the maximum effective plastic strain was found to be dependent of the crystallographic orientations of the grains. However, a more extensive study is required before conclusions regarding the consistency of the results are drawn.

Sediment erosion in Francis turbines is a big problem in hydropower plants in and around the Himalayas. The sediment composition in the rivers contains high levels of the hard mineral quarts. When the sediments enter the turbine they cause erosive damage to exposed parts such as covers, guide vanes and runner. The sediment concentration is at its highest during the monsoon period. During this period some turbines are stopped when the sediment consentration reaches certain levels to reduce the damage. Jhimruk power plant in the mid-western part of Nepal is a good example of how the sediment erosion affects the operation of a power plant. During the monsoon period the turbines can be eroded to an almost unrepairable state. The turbines have to go through substantial annually maintenance. A result of this is reduced power output and high maintenance costs. It is therefore of interest to design a new Francis turbine that can better withstand the sediment erosion. A cooperation project between Kathmandu University and The Norwegian University of Science and Technology was started as a part of the RenewableNepal project which aims to develop and start manufacturing of erosion resistant Francis turbines.A parameter study of different blade designs have been performed to find a more erosion resistant design. In this thesis FSI analyses have been performed on three different designs to verify their structural integrity. The designs transfers the hydraulic energy from the water to the blade in different sections. The results showed a stress distribution which coincided with the energy transfer along the blade. The reference design was analyzed with two different blade thickness. For all the designs the stress was relatively low compared to the criteria for hydraulic turbines.

This thesis presents an off-design simulation of offshore combined cycles. Offshore installations have a substantial power demand to facilitate the oil and gas production. To cover this need of power almost all the platforms use one or several gas turbines, often described as a simple cycle. However, because of high taxes on emissions, and increasing gas prices, more efficient technologies have been reviewed. One solution has been installing combined cycles (CC) offshore. Between 1999 and 2000 three combined cycles were installed on the Norwegian continental shelf and are still in operation. A combined plant may operate for prolonged time at off-design conditions, depending on power demand, ambient condition offshore. First, this thesis gives a description of combined cycles from a thermodynamic and technical point of view. A study of existing offshore combined cycles is performed, and some of the implications of using combined cycles offshore are discussed. In the study, also off-design performance regarding the gas turbine and steam cycle is presented. Further, the simulation tool GTPRO is used to model two CC plants, one designed for offshore installations, and one designed to achieve high efficiency. As part of the design process a sensitivity analysis is performed to find a good trade-off between efficiency and weight for the offshore plant. The model showed good agreements compared with the existing offshore plants, with a power output of 50.3MW, plant efficiency of 50.3%, and similar weight of the skids. The high efficient plant, based on the same gas turbine, and the same assumptions produced 53.1MW. This model gained 2.4MW more in power output, however with a penalty of 209 ton in extra weight.To review the plants performance and operability, off-design simulations were performed in GTMASTER. Both part load and changing ambient temperature were investigated. The results showed that both plants had similar behavior in performance at off-design, and that the GT strongly dictates the behavior of the steam cycle. At part load the relative SC efficiency increases, resulting in general high plant efficiency. At 60% GT load, the relative gas turbine efficiency is 81% compared to the relative plant efficiencies of about 90%. The difference in efficiency between the high efficient plant and the offshore plant remains constant at part load. The result from the simulations of ambient temperature is that none of plants will achieve higher plant gross efficiency at changing ambient temperature. The best plant efficiency occurs at design point. However, both plants have a long interval with approximately 100 % plant efficiency. From 15 to 0°C, the relative SC gross efficiency drops with 5 %, and the relative GT efficiency increase with 2%. However, the power output changes for both the GT and ST. From 28°C to about 0°C the power output increase almost linearly for the SC and GT.

Carbon composite materials and structures have low weight, high stiffness, high strength and chemical resistance. Throughout this master thesis a feasibility study to utilize carbon composites in tubes, designed to withstand high pressures, is undertaken both analytically and experimentally. The tube is meant to be used for well intervention, replacing the current solid carbon rod. In such operations is low weight, in addition to above mentioned properties, a critical factor for long reach. To extend the reach of the equipment the submerged weight of such a tube must be as low as possible.To enable a tube to withstand the high pressures, which can reach more than 1000bar, a thick walled tube is the only alternative to decrease the submerged weight compared to a solid rod. Work and literature on thick walled composite tubes with inner diameter to thickness ratios as low as 2 is minimal, if not absent.A two layered laminate structure was chosen for the tube. The inner layer existing of hoop winded fibers and the outer layer of longitudinal UD fibers. Such a layup will give both high radial strength and axial stiffness.Throughout the analysis it was found that the cause of failure would be instability. This conclusion was drawn as instability would occur before any of the chosen failure criterions were fulfilled. This implies that the strength of the material is utilized maximally.The experimental results had good coherency with the analytical results. Results from physical tests had a large scatter, but this was predicted as a result of a manual production process leading to uneven distribution of fibers and medium to large voids.Several parameters, both regarding load cases and necessary material properties, for the given requirements of the tube have not been assessed. However, results from conducted analytical and experimental work shows that thick walled composite tubes are able to withstand the given loading conditions, together with keeping the submerged weight sufficiently low.Future work based on the results in this thesis should include test results with statistical significance, analyses on the more complex load cases, optimal laminate design and identifying a suitable matrix material which can withstand the necessary temperature requirement.

Numerous applications, such as meso-scale heat exchangers, Lab-on-Chip devices (LOC), different systems within pharmaceutical and food industry, monodispersed emulsion and several other microfluidic systems, include two-phase flow through a meso-scale T-junction. When two-phase gas-liquid flow passes through an asymmetric meso-scale T-junction, a mal-distribution occurs. The phenomenon has proven itself to be unavoidable in most cases. In some applications this phenomenon can put the operational system at risk, while in other applications it is actually preferred. The phenomenon is still far from thoroughly understood. Thus the objective of this thesis is to further investigate this mal-distribution phenomenon. Split ratio for plug flow at a meso-scale T-junction has been investigated. A model for prediction of the split ratio has been proposed. Physical ingredients for determination of the split ratio have been focused upon. Much of the conducted work is based on findings in the MSc thesis by Hong et al. (2011) who proved the importance of the bubble length when predicting the split ratio. Split ratio, bubble length and pressure has been measured through experimentation. The T-junction used in the conducted experiments has a main channel, referred to simply as the “main”. It is connected in a straight line with one outlet referred to as the “run”. The second outlet is connected perpendicularly to the main and the run, and is referred to as the “branch”. All channels have a square shaped cross section with a hydraulic diameter of . Water and air was used as working fluids. For all conducted experiments the flow field took on a plug flow pattern. The branch channel has been observed to be rich in gas for all cases, except when the flow rate in the run is high. The flux in the main also has to be low to reduce the viscous drag forces between the two phases and the inertial forces of the plug. For increasingly high total flow rate in the run, a turning point has been located. When the flow rate exceeds this point the run becomes rich in gas. In both extreme cases (high flow rate in the run and in the branch) separation occurs for sufficiently short bubbles. The occurrence of separation is also highly dependent on the total flux in the main. To retain separation the surface tension has to overcome the viscous drag forces acting on the interface between the two phases. In the centre regime, where bubbles always break up and a plug flow pattern occurs in both outlets, the split ratio shows a strict relation to the bubble length. This strict relation between the split ratio and the bubble length were also concluded upon in the MSc thesis by Hong et al. (2011). In the defined centre regime changes in superficial velocities showed to have a negligible effect on the split ratio in comparison to variation in the bubble length. Long bubbles yields a split ratio located closest to perfect distribution. Decreasing the bubble length yields an increase in the void fraction (gas) in the branch. A model for prediction of the split ratio has been proposed. It is primarily valid within the centre regime, and is based on the time and area averaged Bernoulli equation. The model takes the bubble length into account, and predicts the split ratio on the main assumption that an increased amount of energy is lost to friction and separation as the fraction of water in the branch is increased. This while keeping the total fluxes in each of the outlets constant. An anticipated trend has been located through evaluating the model against experimental data. Therefore the model has been concluded upon to be physically sound.