Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
5 results
Search Results
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 - 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.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, SebnemThis 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.Article Citation - WoS: 4Citation - Scopus: 4Destratification of Thermally Stratified Water Columns by Air Diffusers(Elsevier, 2023) Elçi, Şebnem; Hazar, Oğuz; Bahadıroğlu, Nisa; Karakaya, Derya; Bor, AslıThis study aims at improving the understanding in order to optimise an aeration system for artificial destratification to control cyanobacteria growth in the reservoirs. Previous applications for artificial destratification in reservoirs were based on installations based on computational methods, 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 an optimized design with the help of experimental and numerical analyses. In order to perform experimental studies, a novel water tank enabling the heating/cooling of the water column as desired and a diffuser system were manufactured. During the experimental studies, effect of bubble size, bubble slip velocity, and other parameters of air diffuser on destratification efficiency were investigated. Based on the nondimensional parameters, a new destratification efficiency formula is obtained by the Genetic Algorithm (GA) approach. Additionaly, the hydrodynamics of the water tank during the mixing process by air diffuser was simulated via 3D numerical model and validated with experimental results. The Eulerian multiphase model with the ‘degassing’ boundary condition and k-ω turbulence model are found to be suitable for the purposes of the study. 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.