Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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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, SebnemStudy 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: 3Citation - Scopus: 3Numerical Assessment of Vertical Axis Hydrokinetic Turbine Efficiencies With Different Grate Protections(Inst Engineering Technology-IET, 2025) Karakaya, Derya; Elci, SebnemHydrokinetic 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 - Scopus: 1Mitigating Thermal Stratification in Lakes/Reservoirs Through Wind-Powered Air Diffusers(Wiley, 2024) Hazar, Oguz; Elci, SebnemThermal 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%. imageArticle Citation - WoS: 3Citation - Scopus: 5Hydrokinetic Power Potential Assessment of the Çoruh River Basin(Elsevier, 2024) Karakaya, Derya; Ozturk, Bahadir; Elci, SebnemHydrokinetic 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.Article Citation - WoS: 9Citation - Scopus: 13Numerical Analysis of Three Vertical Axis Turbine Designs for Improved Water Energy Efficiency(Mdpi, 2024) Karakaya, Derya; Bor, Asli; Elci, SebnemA hydrokinetic turbine with a vertical axis is specifically designed to harvest the kinetic energy from moving water. In this study, three vertical axis water turbines, namely Gorlov, Darrieus, and Savonius turbines, were compared for their efficiency via numerical modeling for steady-state conditions via the ANSYS 2022 R2 Fluent model. The Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) was implemented with an SST k-omega turbulence model. The dynamic mesh technique, which allows modeling according to changes in angular velocity at each time step, was used to simulate flow around the turbines for six different velocities (from 0.5 to 3 m/s). The efficiency of the turbines was compared and the results were analyzed. The pressure, velocity, and turbulence kinetic energy distributions around the rotor were measured at different rotational angles and results indicated a wider operating range for the Darrieus and Gorlov turbines compared to the Savonius turbine. The highest power coefficient of 0.293 was achieved in the model featuring a Darrieus turbine, corresponding to a TSR value of 1.34, compared to 0.208 for the Gorlov and 0.257 for the Savonius turbine, at TSR values of 1.3 and 1.06, respectively. Numerical modeling results pointed to a significantly higher self-starting capacity for the Savonius turbine compared to the others.