Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
Browse
3 results
Search Results
Master Thesis Experimental Investigation of the Pressure Drop Performance and the Cavitation of a Plunger Valve(Izmir Institute of Technology, 2020) Aydeniz, Emre; Özkol, ÜnverThis thesis, realized within the scope of a TUBITAK project of DOĞUġ VANA A.ġ, is aimed to characterize the pressure drop and cavitation performance of plunger valve with various cavitation lattices in different opening ratios. Pressure drop performance and cavitation studies have been examined experimentally. Loss coefficients and flow coefficients were used to examine the pressure drop performance of four different types of cavitation lattices. According to the results of this experimental study, it was observed that the loss coefficient is almost independent of Reynolds number except for Re < 4x105. Cavitation creates vibration and noise in high-frequency ranges. Therefore, cavitation detection was examined in the high-frequency range of 5 kHz to 18 kHz and was performed using an accelerometer. Fourier Transform (FT) and Power Spectrum Density (PSD) were used to measure the energy levels of vibrations. Cavitation limits (incipient and critical cavitation) were detected by comparing PSD levels and cavitation indexes at different aperture ratios for all lattices. As a result, the safe cavitation range for the valve was determined by comparing the cavitation indexes according to the valve opening ratio. A new cavitation index estimation study was performed for the new diameter and upstream pressure values with the effect of size scaling and pressure scaling.Master Thesis Hydrodynamic Interaction in Rotational Flow(Izmir Institute of Technology, 2007) Çağatay, Filiz; Yılmaz, OğuzThe interaction of water waves with arrays of vertical cylinders problem is studied using diffraction of water waves and addition theorem for bessel functions. The linear boundary value problem which is derived from physical assumptions is used as the approximate mathematical model for time-harmonic waves. Linearization procedure is described for the nonlinear boundary conditions on the free surface. The problem is solved by using Addition theorem for Bessel functions. Limiting case, k 0, known as long wave approximation, is analysed using limiting forms of Bessel functions. Vortex-cylinder interaction is analyzed using a similar technique involving Laurent series expansions of complex velocity and the Circle Theorem. But this method failed to work. Further analysis is necessary. Vortex dynamics is analysed in annular domains, which can conformally be mapped into infinite domain with two cylinders, using the terminology of q-calculus. Finally, the result of vortex-cylinder interaction in annular domain is transformed into the infinite domain with two cylinders using conformal mapping. Image representation clearly shows the mechanism of inverse images which accumulate at zero and infinity in the w-plane and a and 1/a in the z-plane.Master Thesis Modeling of Hydrodynamics and Sedimentation in a Stratified Reservoir: Tahtalı Reservoir, Izmir(Izmir Institute of Technology, 2008) Çalışkan, Anıl; Elçi, ŞebnemThe main goal of this study was to investigate the hydrodynamics of a stratified reservoir for different flow and weather conditions through numerical modeling. This study also investigated the effects of selective withdrawal, climate change, and sediment deposition on hydrodynamics. A three-dimensional numerical model, Environmental Fluid Dynamics Code (EFDC) has been selected in the present study to model the hydrodynamics in the lake. The study site was selected as the main pool of Tahtali Reservoir providing 40% of the water used in the city of zmir (Population: 3.4 million by 2000). Applied numerical model was validated by monthly observations of water velocity and temperature profiles. Field measurements were performed from July 2006 to September 2007 in the lake and in two rivers (aal and Tahtali). The water velocity measurements in the lake were made using a 1.5-MHz acoustic Doppler current profiler. For water temperature and quality measurements, a hand-held water quality meter with a depth sensor were used for both lake and river measurements. Furthermore, a weather station was set up by the lake in order to collect accurate data for wind conditions in the study site.The numerical model predicted the observed velocity profiles and temperature time series satisfactorily. Possible reasons for discrepancies were investigated. Numerical model results indicated that water velocities were strongly dominated by the wind data and correct measurement of wind stress on the lake surface is necessary for accurate prediction of velocities in the water column. Withdrawal of the water at the bottom outlet was found to be the most effective choice encouraging the mixing of the water column. Possible climate change impacts modeled numerically indicated that the thermocline depths were lowered in the water column causing the deterioration of water quality. Sedimentation thickness was estimated via numerical modeling and the long term erosion rate was calculated by USLE method. Modeling the sedimentation zones provided valuable information on the capacity of the reservoir. The results of this study can be used to guide the further investigations in the lake including modeling of water quality for better management practices.