Profile URL: https://hdl.handle.net/20.500.13091/11677
Job Title:Dr. Öğr. Üyesi
Email Address:igoktepeli@ktun.edu.tr
Main Affiliation:02.10. Department of Mechanical Engineering
Status: Current Staff
ORCID:
0000-0002-2886-8018
0000-0002-2886-8018Scopus ID:
57194015600
57194015600YÖK Akademik: E368AF9A71A04525
Google Scholar:
jgpN43IAAAAJ
jgpN43IAAAAJWeb of Science ID:
ABF-7549-2021
ABF-7549-2021Name Variants:
Goktepeli, I. Göktepeli, İ.
31 results
Scholarly Output Search Results
Now showing 1 - 10 of 31
Article Citation - WoS: 1Citation - Scopus: 1Drag Reduction by the Effect of Rounded Corners for a Square Cylinder(Aip Publishing, 2024-09-01) Göktepeli, İlkerFlow around square cylinders has been studied via unsteady simulations done at a Reynolds number of Re = 100. In the present study, the effects of rounded corners on different flow characteristics have been evaluated. The main influence of rounded corners has been considered for various ratios (r*) up to 0.45 in terms of drag coefficient values. Flow stagnation points have been obtained in front of the square cylinders. These points constitute the maximum pressure. The cluster sizes for cross-stream velocity components are nearly the same. Viscous flow generates vortices around the top and bottom edges of the square cylinder. The produced vortices have been affected by the wake region. When moving away from the bodies, streamwise velocity profiles have been influenced by the variation of the rounded corner ratios. The wake region has shrunk owing to the rounded corners, and the drag reduction has been provided. The drag coefficient (CD) has been obtained as 1.418 for r* = 0. As a result of increasing the ratio for the rounded corners, drag coefficients decreased for the square cylinders. The percentage values are 4.6%, 7.2%, 8.4%, 9.6%, 11.1%, 11.9%, 12.5%, 13.3%, and 14.3% for the drag decrement from r* = 0.05 to r* = 0.45 when compared to the reference value. The most effective value for drag reduction has been attained as 4.6% for the ratio of rounded corners in a row. Even though the decrement percentage tends to increase by enhancing the ratio of the rounded corners, the increment rate indicates the decreasing trend.Article Citation - WoS: 4Citation - Scopus: 3The Groove Effect on Wake Characteristics of Rotating Cylinders(American Institute of Physics, 2024-07-01) Yagmur, S.; Aksoy, M.H.; Dogan, S.; Goktepeli, I.; Ispir, M.In the present study, active and passive flow control methods have been implemented to investigate their effects on the wake flow structures of a circular cylinder. Grooves having circular, rectangular, and triangular cross sections have been applied to the cylinders exposed to the rotation rates, α, from 0 to 0.79. The experiments have been conducted by particle image velocimetry at a Reynolds number of Re = 5 × 103. The contour graphics of time-averaged results have been presented. Moreover, the variations in velocity profiles have also been depicted. The experimental results revealed significant variations for flow patterns, wake structures, and turbulence parameters due to the effects of both groove geometries and rotational motion. In the stationary cases, for turbulence intensity, the circular grooved cylinder exhibited a 15% increase, while the triangular grooved cylinder showed a slightly higher increase of around 20% compared to that of the bare cylinder (BC). Conversely, in non-stationary cases, the rectangular grooved cylinder displayed the most prominent reduction in turbulence intensity, decreasing by approximately 10% compared to that of the BC. The groove type has considerably affected the flow structures of the wake regions, especially for the lower rotation rates. © 2024 Author(s).Article Numerical Modeling of Backward-Facing Step Flow Via Computational Fluid Dynamics(2023) Göktepelı, Ilker; Atmaca, UlaşAs a fundamental case for problems of fluid mechanics, examination of flow separation and its reattachment is important for engineering applications. Considering the significance of the subject, backward-facing step flow has been modeled via Computational Fluid Dynamics (CFD) based on an experimental study previously done at Re = 5000. Steady simulations have been conducted by k-ε Renormalization Group (RNG) considering the same flow conditions of the reference study. Pressure distributions, streamwise and cross-stream velocity components, velocity magnitude values with streamline patterns and turbulence kinetic energy values have been presented by using contour graphics. Furthermore, the stations for pressure distributions, velocity profiles for streamwise components and turbulence kinetic energy values have been defined for evolution of related data. Lower pressure zone for the wake region of the backward-facing step has been attained due to flow separation. Separation of the upstream boundary layer has been seen and it became a curved one. Moreover, turbulence level of the step wake has been obtained as higher than those of any other points. Transition to core flow has been attained at y* = 1.1 that is above the step height. Flow oscillations have been observed for x* ≥ 2 and y* ≤ 1 since the fluctuations for these values were effective in the wake region. To sum up, the dimensionless reattachment length has been numerically obtained as 5.92 which is very good agreement with the experimental results at same Reynolds number. The deviation from the reference results is from 0.34 % to 1.33 %.Article Computational Modeling of Three-Dimensional Flow Around a Complex Bridge Pier by Different Methods(Springer Science and Business Media Deutschland GmbH, 2025-08-30) Goktepeli, IlkerHydrodynamic flow structures of a complex bridge pier have been scrutinized in the present study for a value of Reynolds number as Re = 3.87 × 104. Considering reference cases, different turbulence models have been compared with respect to variant flow structures and drag coefficient values obtained for steady and three-dimensional flow. For the pier, the maximum pressure value has been obtained at the point representing the first flow contact. The reason is the flow stagnation indicating the sudden decline of velocity values. Separated flow caused lower pressure region for the elements of the complex bridge pier. As a result of decreasing cross-sectional areas, flow acceleration between the piles has been observed. At the upstream, there are two dominant clusters representing cross-stream velocity components. The direction of rotation is clockwise for positive values while it is vice versa for negative ones. Moreover, drag coefficients have been obtained as 1.16 ≤ C<inf>D</inf> ≤ 1.178 via different turbulence models. Regarding the past results from literature, k-ω SST turbulence model is the most successful one when it comes to the drag coefficient. As a recommendation, the second one is k-ε Realizable turbulence model by the difference of 0.78% for the drag coefficient. The percentage difference of the drag coefficient is 1.47% obtained by Transition SST turbulence model. Similar situation is obvious for the flow characteristics compared to the reference study. © 2025 Elsevier B.V., All rights reserved.Article Computational Study on the Effect of the Staggered Ribs on Heat Transfer Phenomena Between the Horizontal Plates(2021-03-31) Göktepeli, İlker; Atmaca, Ş. Ulaş; Atmaca, UlasIn terms of multifarious technical applications, various kinds of passive methods are preferred to the active techniques when it comes to increase the amount of convection heat transfer via less energy consumption. As a vortex generator within the scope of the passive method, rib is usually employed to induce the heat transfer enhancement. In this study, the rectangular cross-sectional ribs have been placed to increase the amount of the heat transfer for the staggered arrangement between the horizontal parallel plates. Numerical simulations have been conducted by using k-? SST turbulence model at Re = 10000. The rib effect has been comparatively investigated in case of thermal and hydraulic performance presented via the numerical results. Time-averaged results for temperature, pressure, streamwise velocity component and streamline patterns have been presented in terms of contour graphics. Furthermore, heat transfer enhancement by using the ribs has been given depending on the increment ratio of Nusselt numbers. Including friction losses due to the ribs mounted on the plates, the values of thermal performance factor for all ducts have been calculated. According to these results for heat transfer augmentation at Re = 10000, h' = 0.1 with S' = 0.5 having ? = 1.049 and h' = 0.1 with S' = 0.75 having ? = 1.019 have been recommended rather than the smooth duct.Article Examination of Wake Characteristics for Tandem Circular Cylinders via Computational Fluid Dynamics(2025-03-31) Goktepelı, IlkerWake characteristics of the cylinders have been numerically investigated for tandem arrangement. The study was done for airflow at a diameter-based Reynolds number of Re = 200 via ANSYS-Fluent 2021 R1. Variations of horizontal distances between two cylinders with the same diameter have been considered in the 1.5 ≤ L* ≤ 6 range. The drag coefficients have been attained, and these results have been presented along with flow characteristics of velocity components, magnitude values for vorticity, and pressure distributions. In front of the upstream cylinder, flow stagnated in all cases. Nonetheless, it has been observed for L* ≥ 4.5 in terms of the downstream cylinder. The periodical clusters for cross-stream velocity components have been attained in the wake region. Vortex shedding has been observed in the flow patterns. The unsteady flow structures have been seen. The spacing between the circular cylinders influenced the drag force. Nevertheless, the effect of an upstream cylinder on the downstream one disappeared for L* ≥ 4.5 in this study. The drag coefficient of the upstream cylinder is approximately the same concerning the value of a single one in terms of L* ≥ 4.5 as a result of the studyArticle The Effects of Nanofluids on Forced Convection Heat Transfer Inside Parallel Plate Heated With Flush Mounted Discrete Heater Sources(2023) Atmaca, Şükrü Ulaş; Göktepeli, İlker; Ateş, AliA numerical solution on forced convection of Al2O3-water nanofluid for different volume fractions is investigated for laminar flow through a parallel plate with flush mounted discrete heat sources. The model used for nanofluid mixture is a single-phase approach and fluid properties are considered constant with temperature. The finite difference method is used for solutions and four different volume fractions are considered varying from 0% to 4%. A fully developed laminar velocity profile is considered and the parallel plate is assumed as heated with three discrete heat sources flush mounted to the top and bottom plate with the same lengths. Uniform wall temperature boundary condition is taken for discrete heaters. Peclet numbers are in the range of 20-100. For comparison and validity of the solution the results for a classical problem, laminar flow through a parallel plate which is heated at the downstream region with constant temperature, are obtained. Results are presented in terms of bulk temperature, heat flux, and local Nusselt number. Heat transfer is enhanced with the particle volume concentration. For comparison, pure water results are also shown in the figures. At the locations where heat is applied the heat flux values decrease as the volume fraction increase and the bulk temperature values are higher for the higher volume fractions at the heated locations. As the volume fraction increases the local Nusselt number can increase up to 30% than to pure water.Article Bir Sanayi Tesisi İçin Gerçek ve Simüle Edilmiş Fotovoltaik Sistemlerin Karşılaştırılması(Necmettin Erbakan Üniversitesi, 2025-12-31) Deveci, Mustafa; İspir, Murat; Aksoy, Muharrem Hilmi; Göktepeli, İlkerBu çalışma, Türkiye’nin Konya ilinde yer alan bir endüstriyel tesise ait operasyonel ve simüle edilmiş fotovoltaik (PV) sistemleri, PVsyst yazılımı kullanılarak karşılaştırmaktadır. En yüksek ışınım şiddeti Temmuz ayında kaydedilirken, en düşük değer Aralık ayında gözlemlenmiştir. Yıllık küresel yatay ışınım 1761.1 kWh/m², yıllık etkili küresel ışınım ise 1661.1 kWh/m² olarak hesaplanmıştır. Etkili ışınım açısından en yüksek ve en düşük değerler sırasıyla Haziran ve Ekim aylarında elde edilmiş olup, yıllık bazda toplam fark %5.68 olarak bulunmuştur. Her iki sistem için en yüksek ve en düşük elektrik üretimi sırasıyla Temmuz ve Ocak aylarında gerçekleşmiştir. Yıllık ortalamaya göre, aylık ortalama elektrik üretimi operasyonel sistem için 210.2 MWh, simüle edilmiş sistem için ise 201.1 MWh olarak ölçülmüştür. Her iki durumda da, en yüksek performans oranı (PR) Şubat ayında elde edilmiş; bu değerler operasyonel sistem için 0.827, simüle sistem için ise 0.954’tür. En düşük PR değerleri Mayıs ayında gerçekleşmiş olup, sırasıyla 0.703 ve 0.656 olarak tespit edilmiştir. Operasyonel ve simüle sistemler için yıllık ortalama PR değerleri sırasıyla 0.797 ve 0.756 olarak belirlenmiştir. Elde edilen sonuçlar, simüle edilen sistem performansının gerçek sistem verileriyle güçlü bir uyum içinde olduğunu göstermekte olup, PVsyst yazılımının endüstriyel uygulamalarda fotovoltaik sistem davranışını değerlendirmede doğruluğunu ve güvenilirliğini ortaya koymaktadır. The present study compares operational and simulated photovoltaic (PV) systems for an industrial facility located in Konya Province, Türkiye, using PVsyst software. The highest radiation intensity was recorded in July, while the lowest was in December. The global horizontal irradiance is 1761.1 kWh/m² per year, while the effective global irradiance is 1661.1 kWh/m² per year. The maximum and the minimum values were obtained in June and October, respectively, with an overall annual difference of 5.68%. The highest and the lowest electricity generation values have been observed for both systems in July and January, respectively. On annual basis, the monthly average electricity generation was 210.2 MWh for the operational system and 201.1 MWh for the simulated system. In both cases, the peak performance ratio (PR) was 0.827 for the actual system and 0.954 for the simulated one in February. The lowest values were obtained in May, with 0.703 for the operational system and 0.656 for the simulated system. The annual average PR values for the actual and the simulated systems were 0.797 and 0.756, respectively. The results demonstrate that the performance of the simulated system closely matches that of the actual system, confirming the accuracy and reliability of PVsyst simulations for evaluating real-world photovoltaic system behavior in industrial applications.Article Dik Düz Plakadan Geçen İki Boyutlu Akışın Sayısal Olarak İncelenmesi(2025-10-20) Goktepelı, IlkerNormal düz bir plakanın etrafındaki aerodinamik akış özellikleri, geçici rejimdeki simülasyonlar açısından Reynolds sayısının (Re) 100 ve 150 değerlerinde dikkate alınmıştır. Bu çalışma sayısal sonuçlar olarak basınç değerlerini, akış yönündeki ve akışa dik yöndeki hız bileşenlerini, akım çizgileriyle sunulan hız büyüklüğü değerlerini, girdap büyüklüğü değerlerini ve sürükleme katsayılarını sunmaktadır. En yüksek basınç, yukarı akış bölgesi için durgun akış nedeniyle elde edilmiştir. Normal düz plaka etrafındaki basınç düşüşü ayrılmış akış kaynaklıdır. Ancak, art izi bölgesi daha önemli bir basınç düşüşüne neden olmuştur. Birincil dönümlü akış bölgesi Re = 100'den Re = 150'ye küçülmüştür. Öte yandan, ikincil bölge daha büyük boyutta olmuştur. Normal düz plakanın art izi bölgesinde, akışa dik yöndeki hız bileşenlerinin periyodik dağılımları sağlanmıştır. Artan Reynolds sayısının bir sonucu olarak, aşağı akım bölgesi için gözlenen girdap saçıntısı nedeniyle uzamış kayma tabakaları elde edilmiştir. Kararsız girdap yapıları akış alanının çıkış bölgesine kadar uzamıştır. Bununla birlikte, en yüksek girdap değeri, yüksek viskoz difüzyon nedeniyle daha düşük Reynolds sayısı değeri için aşağı akım yönüde azalmıştır. Sürükleme katsayıları sırasıyla Re = 100 ve Re = 150'de CD = 2,42 ve CD = 2,51 olarak elde edilmiştir. Bu değerler, benzer Reynolds sayısı değerleri için önceki çalışmalarda sunulan değerlerle oldukça uyumludur.Article Citation - WoS: 30Citation - Scopus: 34Turbulence Modeling Approaches on Unsteady Flow Structures Around a Semi-Circular Cylinder(PERGAMON-ELSEVIER SCIENCE LTD, 2020-03-01) Yağmur, Sercan; Doğan, Sercan; Aksoy, Muharrem Hilmi; Göktepeli, İlkerThis paper presents the flow field around a Semi-Circular Cylinder (SCC), a basic geometry for fluid mechanics, obtained numerically by Computational Fluid Dynamics (CFD) at Reynolds number of 3.2 x 10(4). Time-averaged flow characteristics such as vorticity, velocity fields with streamline patterns, Reynolds stress correlations, Turbulence Kinetic Energy (TKE), pressure and drag coefficients have been examined by using Reynolds-averaged Navier-Stokes (RANS), Detached Eddy Simulation (DES) and Large Eddy Simulations (LES) turbulence models. Several RANS approaches with turbulence modeling including SST k-omega, k-epsilon and their derivatives were used, while in the LES simulations, the dynamic Smagorinsky subgrid-scale model was employed. The obtained results of the present study have been compared with an experimental study from the open literature. The results of the investigation showed that when numerical findings are compared to experimental ones, the results of LES and DES turbulence models were found to be more consistent than those obtained by using k-epsilon and SST k-omega models. Time-averaged flow patterns have been found to be considerably symmetric with respect to the axis passing through the end of the curved surface of the SCC. The deviation of LES and DES results, and experimental results was less than 7% in terms of the drag coefficient.
Research Topics
Domains
Physical Sciences
Fields
EngineeringEnvironmental Science
Subfields
Computational MechanicsAerospace EngineeringEnvironmental EngineeringMechanical Engineering
Specific Research Areas
Fluid Dynamics and Vibration Analysis
Aerodynamics and Fluid Dynamics Research
Fluid Dynamics and Turbulent Flows
Wind and Air Flow Studies
Heat Transfer Mechanisms
Sustainable Development Goals
7AFFORDABLE AND CLEAN ENERGY
2
Research Products
Documents
18
Citations
176
h-index
7
Documents
14
Citations
143
Publication Collaboration
| Affiliation Name | Count |
|---|---|
| Konya Technical University | 30 |
| Adana Science and Technology University | 4 |
| Selçuk University | 3 |
| Laboratoire d'Innovation Thérapeutique | 1 |
| Istanbul Technical University | 1 |
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Data obtained from OpenAlex
| Journal | Count |
|---|---|
| Physics of Fluids | 3 |
| Ocean Engineering | 2 |
| Firat University Journal of Experimental and Computational Engineering (Online) | 1 |
| Flow Measurement and Instrumentation | 1 |
| Flow Turbulence and Combustion | 1 |
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Scholarly Output
31
Articles
30
Views / Downloads
50/45
Supervised MSc Theses
0
Supervised PhD Theses
0
WoS Citation Count
97
Scopus Citation Count
112
Patents
0
Projects
0
WoS Citations per Publication
3.13
Scopus Citations per Publication
3.61
Open Access Source
13
Supervised Theses
0
Scopus Quartile Distribution
Competency Cloud
