Browsing by Author "Koc, Emre"

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Airfoil-slat arrangement model design for wind turbines in fuzzy environment
(2020) Atalay, Kumru Didem; Dengiz, Berna; Yavuz, Tahir; Koc, Emre; Ic, Yusuf Tansel
In this study, a multi-element wind turbine blade that consists of NACA 6411 and NACA 4412 leading-edge slat design is investigated computationally. Optimum design parameters of the slatted wind turbine blade leading to maximum value of C-L/C-D related to the turbine power are obtained. In the optimization process, a new fuzzy logic linear programming methodology integrating with fuzzy linear regression and 2D CFD analysis is proposed. The aerodynamic characteristics of the slatted blade are computed by using Incompressible Navier-Stokes equations and k-omega turbulence modeling. Results are compared with the results of linear programming method and direct search optimization method. The computational results reveal that the proposed methodology for performance optimization is more effective than other methods to obtain high-performance value of the C-L/C-D. The maximum value of the C-L/C-D is obtained as 25.1 leading the maximum efficiency of 0.52.
CFD vs. XFOIL of Airfoil Analysis at Low Reynolds Numbers
(2016) Gunel, Onur; Koc, Emre; Yavuz, Tahir
For Blade Element Momentum (BEM) theory, the airfoil data needs to be as accurate as possible. Nowadays, Computational Fluid Dynamics (CFD) is used for optimization and design of turbine application. Lift coefficient, drag coefficient and lift coefficient over drag coefficient are significant parameters for turbine application. Selecting a suitable computational tool is crucial for design of the turbine. Panel method and an integral boundary layer formulation are combined in the MOIL code for the analysis of potential flow around the airfoils. In this study, XFOIL code and Transition SST k-omega model were used to predict the aerodynamic performance at low Reynolds numbers (Re = 3x10<^>5, 4x10<^>5, 5x10<^>5). The results were compared and CFD results and XFOIL, code result are compatible with each other until stall angle. Also XFOIL, and CFD results were shown a good coherence with literature.
Comparison of Qblade and CFD Results for Small-Scaled Horizontal Axis Wind Turbine Analysis
(2016) Koc, Emre; Gunel, Onur; Yavuz, Tahir
The software QBlade under General Public License is used for analysis and design of wind turbines. QBlade uses the Blade Element Momentum (BEM) method for the simulation of wind turbines and it is integrated with the XFOIL airfoil design and analysis. It is possible to predict wind turbine performance with it. Nowadays, Computational Fluid Dynamics (CFD) is used for optimization and design of turbine application. In this study, Horizontal wind turbine with a rotor diameter of 2 in, was designed and objected to performance analysis by QBlade and Ansys-Fluent. The graphic of the power coefficient vs. tip speed ratio (TSR) was obtained for each result. When the results are compared, the good agreement has been seen.
Effect of cone beam computed tomography voxel size and dental specialty status on the agreement of observers in the detection and measurement of periapical lesions
(2021) Kamburoglu, Kivanc; Koc, Emre; Sonmez, Gul; Elbahary, Shlomo; Rosen, Eyal; Tsesis, Igor; 34120879
Objective. To compare observer agreement between endodontists and oral and maxillofacial radiologists (OMRs) in the detection and measurement of periapical lesions as depicted in cone beam computed tomography (CBCT) with 2 voxel sizes. Study Design. In total, 256 CBCT images of maxillary molars were evaluated by 2 endodontists and 2 OMRs. Images were obtained at voxel sizes of 0.2 and 0.4 mm. Observers evaluated 64 endodontically and 64 nonendodontically treated teeth for the presence of periapical lesions using a 5-point confidence scale. Weighted k values were calculated to determine intra- and interobserver agreement. Intraclass correlation coefficients (ICCs) were calculated to assess intra- and interobserver agreement in width and height measurements of the lesions. Results. Intraobserver agreement ranged from fair to almost perfect, with k values higher for the OMRs than for the endodontists. Interobserver agreement between endodontists ranged from fair to moderate at the 0.2mm voxel size and was slight at 0.4 mm. Agreement between OMRs was almost perfect at 0.2 mm and ranged from substantial to almost perfect at 0.4 mm. ICC was excellent for all observers in all conditions. Conclusions. Intra- and interobserver reliability was affected by voxel size and specialty. Correlation for measurements exhibited no variation.