Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Author: search.filters.author.Elci, SebnemHas files: No

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Now showing 1 - 7 of 7
  • Article
    Uncertainty Assessment of the Impacts of Climate Change on Streamflow in the Iznik Lake Watershed, Türkiye
    (MDPI, 2026) Tezel, Anil Caliskan; Akpinar, Adem; Bor, Asli; Elci, Sebnem
    Study region: This study focused on the Iznik Lake Watershed in northwestern T & uuml;rkiye. Study focus: Climate change is increasingly affecting water resources worldwide, raising concerns about future hydrological sustainability. This study investigates the impacts of climate change on river streamflow in the Iznik Lake Watershed, a critical freshwater resource in northwestern T & uuml;rkiye. To capture possible future conditions, downscaled climate projections were integrated with the SWAT+ hydrological model. Recognizing the inherent uncertainties in climate models and model parameterization, the analysis examined the relative influence of climate realizations, emission scenarios, and hydrological parameters on streamflow outputs. By quantifying both the magnitude of climate-induced changes and the contribution of different sources of uncertainty, the study provides insights that can guide decision-makers in future management planning and be useful for forthcoming modeling efforts. New hydrological insights for the region: Projections indicate wetter winters and springs but drier summers, with an overall warming trend in the study area. Based on simulations driven by four representative grid points, the results at the Karadere station, which represents the main inflow of the watershed, indicate modest changes in mean annual streamflow, ranging from -7% to +56% in the near future and from +19% to +54% in the far future. Maximum flows (Qmax) exhibit notable increases, ranging from +0.9% to +47% in the near future and from +21% to +63% in the far future, indicating a tendency toward higher peak discharges under future climate conditions. Low-flow conditions, especially in summer, exhibit the greatest relative variability due to near-zero baseline discharges. Relative change analysis revealed considerable differences in Karadere and Findicak sub-catchments, reflecting heterogeneous hydrological responses even within the same basin. Uncertainty analysis, conducted using both an ANOVA-based approach and Bayesian Model Averaging (BMA), highlighted the dominant influence of climate projections and potential evapotranspiration calculation methods, while land use change contributed negligibly to overall uncertainty.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Numerical Assessment of Vertical Axis Hydrokinetic Turbine Efficiencies With Different Grate Protections
    (Inst Engineering Technology-IET, 2025) Karakaya, Derya; Elci, Sebnem
    Hydrokinetic turbines are crucial for sustainable power generation, but their performance is often impacted by floating debris and sediment transport, which can damage turbine blades. Sediment retention enhances the turbine's lifespan and reduces maintenance by preventing blade erosion, cavitation and clogging. Protective grates reduce abrasive particle entry, minimising blade wear. They also avoid buildup of sediment, lowering the risk of blockages and cavitation, which harm efficiency and accelerate degradation. This study presents the numerical performance of Darrieus-type vertical axis hydrokinetic turbines under the impact of straight and Coanda type grate protection structures. The effects of these two types of grate structures with different design angles on turbine power coefficient (CP) and torque coefficient (CT) were investigated using the ANSYS Fluent program. The dynamic mesh technique simulated the turbine rotation and the semi-implicit method for pressure-linked equations (SIMPLE) was applied with a shear stress transport (SST) k-omega turbulence model. The turbine's efficiency was compared and the results were evaluated for steady and unsteady flow conditions. The highest power coefficients were obtained as 0.230 and 0.264 for steady and unsteady flow, respectively, in the Coanda grate with a 30 degrees central angle. The highest power coefficients were obtained as 0.215 and 0.247 for steady and unsteady flow, respectively, in the straight grate design with a 60 degrees inclination angle. The sediment retention capacities of Coanda grates (30 degrees central angle) and straight grates (60 degrees inclination angle) with varying particle size distributions were further investigated using the discrete phase model (DPM) under steady flow conditions.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 5
    Hydrokinetic Power Potential Assessment of the Çoruh River Basin
    (Elsevier, 2024) Karakaya, Derya; Ozturk, Bahadir; Elci, Sebnem
    Hydrokinetic power contributes to energy security by a sustainable and predictable power source, and its decentralized nature fosters economic development in local communities. Unlike large-scale hydropower projects, hydrokinetic power has lower environmental impacts, promoting technological innovation and supporting the transition to cleaner energy systems. Furthermore, it pledges to guarantee electricity in isolated regions where traditional power systems are not suited, enhancing energy accessibility. This study presents a method that combines the Soil and Water Assessment Tool (SWAT) with the Hydrologic Engineering Center's River Analysis System (HEC-RAS) to forecast the hydrokinetic power capacity of a basin. The research site chosen is the & Ccedil;oruh River, a transboundary river basin with unavailable publicly accessible flow data. This method approximates the flow data utilizing the SWAT model, which relies on hydrological factors. Following the prediction of the flow data in the basin, the HECRAS model simulates the river's hydraulic conditions to estimate hydrokinetic energy potential. This integrated methodology provides a framework for optimizing hydrokinetic resources in diverse settings, guiding resource management, and sustainable energy planning. This study calculated theoretical hydrokinetic energy potential by considering flow velocity values. Results of the study indicated that the average flow velocity in the & Ccedil;oruh basin reaches its maximum value of 0.99 m/s in spring and its minimum value of 0.69 m/s in summer, respectively. Based on the seasonal analysis of the integrated approach, the highest maximum theoretical hydrokinetic power density in the basin reaches 26 kW/m2 during the spring and in subbasins 5, 7, and 8. The average theoretical hydrokinetic power density is calculated as 0.28 kW/m2. Finally, the study presents several potential locations along the & Ccedil;oruh River through GIS mapping, where small-scale hydrokinetic turbines could be installed as a viable option.
  • 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
    Factors Influencing the Cyanobacterial Dominance in Lakes: Analysis of Lakes in Central Germany
    (IAHR-Int Assoc Hydro-Environment Engineering Research, 2023) Elci, Sebnem; Rinke, Karsten
    This study aimed to identify the key factors influencing the phytoplankton development in twenty- eight lakes located in Central Germany (state of Sachsen-Anhalt). A multivariate analysis of biological (phytoplankton), physicochemical, morphological, and hydrometeorological variables of the lakes collected between 2005 and 2021 is presented here. This analysis is the first approach for this dataset to summarize the statistics and to explore trends and patterns of evolution from a multivariate perspective to improve understanding of the conditions that favor the emergence of different phytoplankton classes and taxons. Correlation analysis of the data showed that both, the biovolume of the phytoplankton and chlorophyll-a were positively correlated with, total nitrogen and phosphorus, and negatively correlated to the depth to epilimnion, residence time and conductivity. The thresholds for total nitrogen, phosphorus and average depths are investigated for cyanobacterial genera of 'Aphanizomenon', 'Anabaena', 'Microcystis' and 'Planktothrix'. Higher chlorophyll-a concentrations (>100 mu g/l) are observed when TN>2 mg/l, P>0.1 mg/l and the average depth was less than 1 m. These thresholds are also valid for higher biovolume values (>5 cm(3)/m(3)) of these cyanobacterial taxons observed in all lakes. The nonlinear equations proposed for chlorophyll-a and biovolume of the phytoplankton derived by the genetic algorithm greatly improved the goodness of fit with respect to the linear models. When all data is considered R2 values are calculated as 68% for chlorophyll-a concentrations and 55% for the biovolume suggesting that these models can be applied for future studies.
  • 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.