Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Estimation of Suspendent Sediment Concentration Using Acoustic Methods(Izmir Institute of Technology, 2009) Aydın, Ramazan; Elçi, ŞebnemAcoustic Doppler current meters (ADCP, ADP, and ADV) can provide information about the suspended sediment concentration (SSC) in the water; although, they are designed for flow velocity measurements. Contrary to conventional samplers, those are labor intensive for measuring SSC, when an acoustic instrument is calibrated for a water system; no additional sensor is needed to measure SSC, enabling the researchers to measure velocity and concentration simultaneously which is required for most sediment transport studies. Recently, the acoustic instruments are investigated in different studies where signal to noise ratio (SNR) and SSC were related using different formulations. However, these studies were limited to single study site where neither the effect of particle size nor the effect of temperature was investigated. In the scope of this study, different parameters that affect the ADV.s performance prediction of SSC were investigated. In order to investigate the reliability of ADV in different environments, SSC measurements were made in different streams. Soil samples were collected from all measuring stations and particle size analysis was conducted. The multivariate data analysis was applied to the measurements to derive a relation formula between SNR and SSC. Multivariate analysis indicated that reported SSC values depended on at least three parameters; water temperature, mean diameter of the soil, and shape of the particle size distribution curve. Also, effect of high SSC conditions on ADV performance was investigated during and after rain events. Results indicated that ADV was not capable of measuring SSC when a limit concentration (SSC>400 mg/l) was exceeded.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.