Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 3Citation - Scopus: 3Numerical Assessment of Vertical Axis Hydrokinetic Turbine Efficiencies With Different Grate Protections(Inst Engineering Technology-IET, 2025) Karakaya, Derya; Elçi, Şebnem; 01. Izmir Institute of Technology; 03. Faculty of Engineering; 03.03. Department of Civil EngineeringHydrokinetic 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.Conference Object Design of an Artificial Destratification System To Control Cyanobacteria Growth in Reservoirs(Iahr-int Assoc Hydro-environment Engineering Research, 2022) Elçi, Şebnem; Bahadiroglu, Nisa; Karakaya, Derya; Elci, Sebnem; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThis 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.