WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7150

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Author: search.filters.author.Hazar, OguzLanguage: search.filters.language.en

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  • Article
    Citation - Scopus: 1
    Mitigating Thermal Stratification in Lakes/Reservoirs Through Wind-Powered Air Diffusers
    (Wiley, 2024) Hazar, Oguz; Elci, Sebnem
    Thermal stratification can cause various water quality issues in large water bodies. To address this, a new wind-powered artificial mixing system is designed and experimentally tested for various Savonius rotor combinations (three-stage and four-stage rotors). These turbines directly utilize wind energy to draw air into the water column for aeration, bypassing the need for electrical conversion. The rotor performances were tested in terms of power and torque coefficients. Additionally, these rotors were tested for artificial mixing efficiencies in a specially designed water tank that can mimic thermal stratification typically observed in an actual water supply reservoir. Among the rotors, the three-stage rotor with a 60 degrees phase shift was found to exhibit superior power and torque coefficients, achieving a power efficiency value of 0.14. As for the mixing efficiency, the four-stage rotor with a 45 degrees phase shift excelled in mixing efficiency, reaching 95%.Practitioner Points A new wind-powered artificial mixing system is designed and tested for various Savonius rotor combinations. While keeping the total rotor height constant, the three-stage Savonius rotor class shows superior performance against the four-stage Savonius rotor class in terms of power and torque efficiency. Apart from the rotor performance results, the four-stage Savonius rotors show greater artificial mixing efficiency than the three-stage Savonius rotors. Single-pump/diffuser artificial destratification system exhibits better mixing efficiency than multiple-pump/diffuser systems. A new wind-powered artificial mixing system is designed and tested for various Savonius rotor combinations. The three-stage 60 degrees phase shift Savonius rotor demonstrated the best performance of turbine efficiency. The four-stage Savonius rotor with a 45 degrees phase shift connected to a single-pump system achieved the highest destratification efficiency at 95%. image
  • Conference Object
    Renewable Energy Powered Artificial Mixing of the Reservoirs
    (IAHR-Int Assoc Hydro-Environment Engineering Research, 2023) Hazar, Oguz; Elci, Sebnem
    Reservoirs are essential and critical infrastructures and require proper management practices to improve water quality. Thermal stratification observed in the reservoirs impairs the water quality affecting the algae population and the solubility of heavy metals from sediment particles. Artificial mixing methods are widely used to improve water quality in thermally stratified eutrophic lakes and reservoirs. Air diffuser systems, water pumps, and water jets are commonly applied for aeration and mixing purposes. Although these methods proved to be effective in the literature, aeration and pumping equipment consume a great amount of electricity and require complementary infrastructures and facilities resulting in high costs. The presented study focuses on aeration of the water column powered by renewable energy. A Savonius turbine is implemented to an artificial mixing setup tested in the laboratory. The shaft of the turbine is directly connected to the pump so that the motion is transferred to the pump shaft eliminating the need for the production/storage of the electricity. The effectiveness of the wind turbine on destratification of the water column is investigated based on various wind conditions. In the experiments, static and dynamic torque values are monitored using a modified design of a rope brake dynamometer composed of a highly precise torque sensor, pulleys, and, a platform for connecting this torque measurement system to the wind turbine. The system is further evaluated for its destratification efficiency of the water column through the experiments.
  • Conference Object
    Citation - Scopus: 1
    Morphological Analysis of Büyük Menderes River Over the Years Using Satellite Imagery
    (IAHR-Int Assoc Hydro-Environment Engineering Research, 2023) Bor, Asli; Hazar, Oguz; Elci, Sebnem
    Both bank erosion and sediment deposition on the inner margins are important watershed management problems for streams. Bank erosion not only causes the loss of agricultural lands, but also leads to the narrowing of the cross sections of the streams with the accumulation of sediment in the interior, resulting in floods, damage to the cultivated areas, reduction in dam reservoir lifespan and thus, serious damage to a country's economy. In this study, the morphological analysis of the B. Menderes River, which is one of the most important rivers of Turkey and a residential and intensive agriculture region, for the thirty-year period between 1990-2020 is made via utilization of QGIS for the analysis of Landsat satellite images. This study is thought to be a preliminary study to quantify the morphological changes in B.Menderes River and is expected to be a basis for linking these changes to the changes in the hydrological regime in the basin. During this analysis, the shoreline of the main river, approximately 570 km long, was divided into 10 segments and the sinuosity index values, which are fold parameters, were calculated for each segment. According to the study, it is found that the curvature of the meanders of the B. Menderes River varies between 1.5 and 2.5 in most places.
  • Conference Object
    Design of an Artificial Destratification System To Control Cyanobacteria Growth in Reservoirs
    (Iahr-int Assoc Hydro-environment Engineering Research, 2022) Hazar, Oguz; Bahadiroglu, Nisa; Karakaya, Derya; Elci, Sebnem
    This study aims at designing an artificial destratification system to control cyanobacteria growth in the reservoirs. Previous applications for artificial destratification in reservoirs were based on trial and error on site, where neither the effect of air bubble size and configuration nor the effect of air density in the bubble plume could be investigated. This study seeks for the optimized design. We have tackled this task at four steps. Firstly, we setup an experimental system that mimics a thermally stratified reservoir experiencing hypoxia and oxygenate/mix the water column. We maintain a stable stratification by a novel setup designed for this study enabling to form consistent and desired stratified layers along the water column. Next, we investigate the effects of bubble size, bubble slip velocity and other parameters on destratification efficiency. Nondimensional numbers involving bubble diameter, bubble diffusing area, air rate and stratification rates are used to quantify destratification efficiency for the best design of aeration systems. Then, we simulate the hydrodynamics during the mixing of thermally stratified water columns by air diffusers via a 3-D numerical model. The Eulerian multiphase model and k-. turbulence model are found to be suitable for the purposes of the study. In the final part, the numerical model is validated with the experiments. Based on the error analysis of comparisons of the model and observations, the best configuration of air diffuser is proposed, and the numerical model is found to be successful in simulating the destratification of thermally stratified water columns by air diffuser.