Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651
Browse
Search Results
Article Experimental Investigation of Granular Soil and Clay Interfaces with Direct Shear Tests(MDPI, 2026) Ozturk, Sevki; Ergun, Mehmet UfukThis study experimentally investigates the shear strength behavior of interfaces formed between granular soils and clay under drained conditions, with particular emphasis on peak-to-residual strength evolution. Large and small-scale direct shear tests were performed on clay, granular soils (sand and gravel), and their interfaces, and shearing was continued to large displacements to reliably capture residual behavior. Unlike most previous studies that focus on soil mixtures, this study explicitly quantifies interface-specific shear strength parameters and highlights their distinct mechanical response. The results show that while interface cohesion remains comparable to that of clay, the interface friction angle is consistently higher. Specifically, under residual conditions, the friction angle of the clay (12.9 degrees) increased to 16.4 degrees for the sand-clay interface and to 19.8 degrees for the gravel-clay interface. These findings demonstrate that adopting clay residual parameters for granular soil-clay interfaces may be overly conservative and that interface-specific residual friction angles should be considered in stability analyses of slopes and earth structures.Article An Investigation of Atmospheric Icing Effects on Wind Turbine Blade Aerodynamics and Power Output: A Case Study of the NREL 5 MW Turbine(MDPI, 2026) Ozturk, Berkay; Kocak, EyupThis study presents a numerical investigation of the effects of atmospheric icing on the aerodynamic performance and power output of the NREL 5 MW reference wind turbine. In cold climate regions, ice accretion on wind turbine blades significantly alters the airfoil geometry, leading to aerodynamic degradation characterized by increased drag, reduced lift, and substantial power losses. Understanding these effects is therefore essential for reliable performance prediction and efficient turbine operation under icing conditions. To address this problem, numerical simulations were conducted on six representative blade sections using the FENSAP-ICE framework, which integrates flow field calculations, droplet transport, and ice accretion modeling within a unified computational environment. The analyses were performed under different atmospheric icing conditions, considering liquid water content values of 0.22 g/m3 and 0.50 g/m3 and ambient temperatures of -2.5 degrees C and -10 degrees C. The median volumetric diameter was fixed at 20 & micro;m, and the icing duration was set to one hour for all cases, allowing for both glaze and rime ice formations to be systematically examined. The results reveal that ice accretion becomes increasingly pronounced toward the blade tip, mainly due to higher relative velocities and increased collection efficiency in the outer sections. Glaze icing conditions produce irregular horn-shaped ice formations and lead to severe aerodynamic degradation, whereas rime ice forms more compact structures near the leading edge and results in comparatively lower performance losses. The degraded aerodynamic coefficients obtained from the iced airfoils were subsequently incorporated into BEM-based power calculations, indicating that total power losses can reach up to 40% under severe icing conditions, with the outer blade sections contributing most significantly to this reduction. Furthermore, an economic assessment based on annual energy losses highlights the substantial impact of atmospheric icing on wind turbine performance and operational costs.Article System-Level Prediction and Optimization of Cyclone Separator Performance Using a Hybrid CFD-DEM-ANN Approach(MDPI, 2026) Kocak, EyupIn this study, the separation performance of cyclone separators with different geometric configurations was investigated using a hybrid approach that combines Computational Fluid Dynamics, the Discrete Element Method, and Artificial Neural Networks. In the first stage, the flow field was solved using the Reynolds-Averaged Navier-Stokes equations together with the Reynolds Stress Model turbulence closure, and particle motion was evaluated in detail through DEM. To examine the effect of geometric parameters, the inlet aspect ratio, vortex finder diameter, and cylinder height were systematically assessed. The results revealed the formation of a pronounced Rankine-type vortex structure inside the cyclone and showed that secondary flow regions intensified as the vortex finder diameter and cylinder height increased, thereby reducing the separation efficiency. In the inlet section, an optimal aspect ratio was identified. In the second stage, an ANN model was developed to expand the limited dataset obtained from the CFD-DEM analyses. By optimizing the activation function and the number of neurons, the best performance was achieved with a ReLU-based neural network containing a single hidden neuron, reaching a test-set accuracy of approximately R2 approximate to 0.991 and an overall fit of R2 approximate to 0.895. The ANN model also captured interaction trends between flow velocity and geometry that could not be observed with the limited CFD dataset. This hybrid approach provides an effective and low-cost method for performance prediction and optimization in cyclone separator design.Article Pseudo-Static Finite-Element Assessment of Seismic Soil-Pipeline Interaction in Multi-Line Buried Pipelines(MDPI, 2026) Sengor, Mahmut; Alrubaye, Maryam; Almusawi, AliThis study investigates the seismic response of double- and triple-buried steel pipeline systems using finite-element modeling in RS2, with particular emphasis on soil-pipeline interaction and symmetry-breaking behavior under pseudo-static seismic loading. Although the pipeline systems are initially symmetric in geometry, material properties, and boundary conditions, the analysis demonstrates that directional seismic excitation induces quantitatively measurable asymmetric responses in shear force, displacement, and spacing due to nonlinear soil-pipeline interaction. Five parametric scenarios were examined, including burial depth (1-5 m), pipeline diameter (8-56 in.), groundwater table (1.4-20 m), peak ground acceleration (0.1-0.6 g), and soil type. The results show that maximum shear forces increase with burial depth and diameter, reaching approximately 15-17 kN in clayey soils at a PGA of 0.4 g, whereas sandy and heterogeneous soils produce lower shear forces (approximate to 12-14 kN). Horizontal displacements are strongly governed by groundwater and PGA, increasing from about 1.2-1.8 m in dry or deep groundwater conditions to more than 2.8 m for shallow groundwater and exceeding 5 m at PGA = 0.6 g. Triple-pipeline systems exhibit higher shear demand due to confinement effects, with the middle pipeline often developing the largest shear force, while the pipeline facing the seismic load consistently experiences the greatest displacement. This study makes two primary contributions. First, it demonstrates that initially symmetric multilined buried pipeline systems exhibit systematic, quantifiable symmetry-breaking behavior under directional seismic loading, manifested as unequal shear forces, displacements, and interaction effects among adjacent pipelines. Second, it presents an integrated multi-parameter coupling analysis that simultaneously accounts for burial depth, pipeline diameter, groundwater level, soil type, and peak ground acceleration, revealing interaction mechanisms that cannot be captured through single-parameter or single-pipeline assessments.