Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Scaled Down Modelling of a Horizontal Wind Turbine for a Floating Wind Turbine Research(Izmir Institute of Technology, 2020) Erol, Serkan; Özkol, ÜnverFloating wind turbines have to operate under the influence of hydrodynamic and aerodynamic forces which are usually coupled in nature. Due to complicated interactions of wave and wind forces on its structure, predicting motion and performance of a floating wind turbine usually depend on many assumptions. In order to understand the dynamics of the system, experimental studies are required to obtain results by taking into account all parameters. This study is a part of a Tübitak project (217M451) that investigates the dynamics of different floating platforms with a wind turbine attached to it under an atmospheric boundary layer wind profile. In this thesis, a scaling methodology was used to model a wind turbine to use in experimental studies. Reynolds number discrepancy was demonstrated in floating wind turbine modeling. For this reason, the method was created by using Froude number and tip speed ratio similitude, and geometric, kinematic and dynamic similarity was achieved. According to the created methodology, an onshore wind turbine that has 320kW nominal power was scaled down to be used in experimental studies according to the open sea conditions. Along with the model turbine, a thrust force measuring mechanism, hot-wire sensor travers system and a motion detection method by a video have been realized. A wave maker and a wind nozzle which are the part of the Tübitak project of which the model turbine described in this thesis will be used, therefore; small description of those are also given in the thesis.Master Thesis Airfoil Boundary-Layer Stability Calculations and Transition Prediction(Izmir Institute of Technology, 2019) Pekdüz, Umut; Özkol, ÜnverThis study involves research and understanding of airfoil laminar boundary-layer transition based on three codes in written FORTRAN: panel code, boundary-layer code and stability code, namely HSPM, BLP2D and STP2D. All codes were connected to each other via inputs-outputs in the one code, called as PBS code. Firstly, the inviscid pressure distribution was obtained using Hess-Smith panel method. Secondly, differential boundary-layer equations were solved for obtained inviscid pressure distribution from panel code. Thirdly, stability calculation was performed using obtained boundary velocity profiles from boundary-layer code at each streamwise stations. Finally, the onset of transition location was predicted using en method based on linear small-disturbance theory. The PBS code was first validated on NACA 0012 and NACA 0015 airfoils making comparison with an experimental work in literature. After validation, three different thick airfoils designed for wind turbine applications were analyzed in terms of lift coefficient and transition location, namely NACA 64-618, DU91W250 and DU4050. The results were compared with XFoil’s viscous and inviscid solutions and experimental measurements based on infrared thermography. It was seen that amplified disturbance frequency magnitude, amplification starting point and choice of threshold value are key points to correctly predict transition point for en method. Additionally, it was found that followings: First, as airfoil thickness increases, the need of interactive boundary-layer method increases for accurate lift coefficient; however, transition point can be still correctly predicted using inviscid pressure distribution. Second, at high angle of attacks and high Reynolds numbers, laminar boundary-layer separation point can be directly taken as transition point instead of using the en method.Master Thesis Design and Numerical Analyses of Guide Vanes of a Multistage Submersible Pump(Izmir Institute of Technology, 2019) Demirtaş, Mert; Özkol, ÜnverThe objective of this thesis is to analyze a multistage submersible pump numerically, figure out the inefficient sections of flow and propose a modified design according to the simulation results. Hydraulic parts of a submersible pump are impeller, diffuser and return channel. In this study, the investigated pump’s stages have only impellers and return channels. According to the literature, the inefficiencies in pump stages might be caused by angle misalignment of impeller and guide vanes, channel geometries or vane designs. The investigated five stage submersible pump and its CAD models are provided by a manufacturing company. In the first part of the study, fluid domain is created for numerical computations and analyses are performed with ANSYS Fluent software. According to the simulation results, flow nonuniformities are observed in return channels and identified that the reason is guide vane geometry. The second part of the study includes the modified design of guide vane and set of simulations with different wrap angles to find out the optimized value. The simulation results of this thesis study are quite satisfactory when they are compared to experimental data of manufacturing company. After modifications, the nonuniformities which are observed in original design are diminished and efficiency of the pump is increased.