Profile URL: https://hdl.handle.net/20.500.13091/11721
Job Title:Arş. Gör. Uzm.
Email Address:mispir@ktun.edu.tr
Main Affiliation:02.10. Department of Mechanical Engineering
Status: Current Staff
ORCID:
0000-0001-5238-6011
0000-0001-5238-6011Scopus ID:
58193831500
58193831500YÖK Akademik: A12F837431DEE0CC
Google Scholar:
HB-eILAAAAAJ
HB-eILAAAAAJWeb of Science ID:
HOH-5521-2023
HOH-5521-2023Name Variants:
Ispir, Murat İspir, M.
24 results
Scholarly Output Search Results
Now showing 1 - 10 of 24
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 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 Citation - WoS: 16Citation - Scopus: 16Machine Learning Approach for Flow Fields Over a Circular Cylinder Based on Particle Image Velocimetry Measurements(Elsevier B.V., 2023-12-01) Aksoy, M.H.; Goktepeli, I.; Ispir, M.; Cakan, A.Flow around a circular cylinder has been experimentally studied at Reynolds numbers of Re = 4 × 103 and Re = 8 × 103 using Particle Image Velocimetry (PIV). The Artificial Neural Network (ANN) method, a subset of machine learning, has been implemented to capture complex flow patterns and relationships within data to estimate the experimental results. Experimental and estimated results regarding instantaneous contour graphics for streamwise (u) and cross-stream (v) velocity components with velocity vector fields have been compared. Furthermore, drag coefficient (CD) and Strouhal number (St) have been validated. In flow features, instantaneous streamwise velocity components indicated a lower pressure zone in the wake region of the cylinder owing to flow separation. The ANN method has predicted the positions of the minimum velocity clusters with 3.2 % for Re = 8 × 103 as a mean relative error compared to the experimental results. Moreover, the average relative difference of 10.82 % between the experimental and the estimated results for the clusters with the minimum streamwise velocity components has been attained at Re = 4 × 103 and Re = 8 × 103. Regarding the cross-stream velocity components, the mean relative difference values have been observed for the clusters with maximum values of 6.83 % and the clusters with minimum values of 3.66 %. Drag coefficients have also been obtained, and these values are very close as CD = 1.090 and CD = 1.084 for PIV and ANN methods at Re = 8 × 103, respectively. Furthermore, St values of the circular cylinder are St = 0.216 at Re = 4 × 103 and St = 0.211 at Re = 8 × 103, which agree with the results of the literature. © 2023 Elsevier LtdArticle Performance Enhancement of Air Conditioning Systems for Agricultural Vehicles by Using an Integrated Condenser- Receiver/Filter/Drier Design(2025) İspir, Murat; Gülhan, Seyit Faruk; Aksoy, Muharrem Hilmi; Göktepeli, İlkerIn agricultural tractors, the air conditioning system traditionally consists of a separate condenser and external receiver/filter/drier (RFD). This study proposes an innovative design that integrates these two components into a single unit to enhance system performance. The impact of this combined structure on air conditioning performance has been experimentally investigated. The results have been compared with those of conventional systems featuring separate condenser and RFD units. The performance evaluation used the coefficient of performance (COP) as a key metric. For the combined system with 1.1 kg of R-134a refrigerant, COP improvements of 8.8% at 1500 rpm and 10.8% at 2000 rpm have been achieved compared to the conventional system. In contrast, for the combined system, the COP changes are -0.5% at 1500 rpm and +1% at 2000 rpm relative to the traditional configuration. These findings suggest the proposed integrated condenser–RFD system can improve efficiency and sustainability in agricultural vehicle air conditioning systems.Article Citation - Scopus: 2Wake Dynamics of a Rotating Cylinder With Cactus-Shaped Surface Elements(Pergamon-Elsevier Science Ltd, 2026) Ispir, Murat; Goktepeli, Ilker; Yagmur, Sercan; Aksoy, Muharrem HilmiFlow controls have been applied to a cylinder for a Reynolds number of Re = 2 x 103. The results have been procured by Particle Image Velocimetry (PIV). Rotation rates have been considered up to alpha = 1.26 as active control. Apex angles of cactus-shaped surfaces from beta = 7.5 degrees to beta = 45 degrees have been evaluated as passive control. Maximum streamwise values have been observed in regions externally to the wake. Minimum values have been recorded within wakes. Positive cross-stream values have been observed over stationary cylinders. However, these were in the far wake regions. In contrast, negative values have been detected below the stationary cylinders, with these readings occurring over the far wake regions. Beyond influence of apex angles, rotational rates also affected the spatial cluster distributions. Rotation changed the number and distributions of foci and saddle points. Analysis of fluctuating streamwise and cross-stream components revealed two distinct clusters and only one cluster, respectively. As apex angles and rotation rates increased, clusters tended to converge towards the cylinders. These were indicative of dominance stemming from wake and separated flows. It led to two clusters of Reynolds stress correlations. Apex angle impact on vorticity is comparatively limited. Influence of rotational dynamics proved to be more pronounced. Consequently, two vortical structures have been discerned with the positive ones emerging as more dominant because of the rotation. To sum up, the overall effects of active control are more overarching than those attained by passive ones.Article Data-Driven Estimation of Flow around Cactus-Inspired Cylinders Using ANN(Taylor & Francis Ltd, 2026) Goktepeli, Ilker; Ispir, Murat; Aksoy, Muharrem HilmiFlow past cactus-inspired cylinders has been examined by Particle Image Velocimetry (PIV) and Artificial Neural Network (ANN) at Reynolds numbers (Re) of 4000 and 6000. Apex angles including beta = 7.5 degrees, beta = 10 degrees, beta = 15 degrees, beta = 30 degrees and beta = 45 degrees have been considered. The results exhibited a good agreement between measurements and predictions. Increasing beta led to wake shrinkage and mitigation of flow separation. Drag coefficients (CD) are 1.1364 and 1.1483 for experimental and predicted results of Re = 6000. Drag reduction has been observed up to beta = 30 degrees except for beta = 10 degrees with ANN. For both PIV and ANN, the highest percentages of drag reduction are 18.83% and 17.64% at beta = 30 degrees, respectively. At beta = 15 degrees, drag coefficients have been reduced by 11.29% for PIV and 9.74% for ANN. However, for beta <= 10 degrees, the maximum percentage of drag reduction is 2.92% for PIV. Between these results, the peak deviation is 4.76% for beta = 10 degrees. The minimum deviation is 0.53% for beta = 45 degrees.Article Citation - Scopus: 1Active and Passive Wake Control of a Circular Cylinder Using Rotation and Surface Texturing(Pergamon-Elsevier Science Ltd, 2026) Aksoy, Muharrem Hilmi; Kurtulmus, Nazim; Ispir, Murat; Goktepeli, IlkerFlow structures over circular cylinders have been widely investigated due to their practical importance and the complexity of wake interactions. In this study, combined passive and active flow control strategies have been examined for rotating cylinders with surfaces having dimples/protrusions at a Reynolds number as Re = 2 x 103. Particle Image Velocimetry (PIV) measurements have been conducted for rotation rates ranging from alpha = 0 to alpha = 1.26 to explore modifications in wake topology for different circumferential angles ((3) between 15 degrees and 60 degrees. For the stationary bare cylinders, symmetric recirculation regions including counter-rotating eddies have been observed, whereas rotation caused the separated region to contract, shifted and lost its symmetry. Dimples/ protrusions, even without rotation, altered shear layer development with effects varying according to the circumferential angle. When rotation was applied, the modified surfaces produced notable changes compared with that of the bare cylinder, including reduced negative-velocity regions and more rapid momentum recovery. The time-averaged vorticity distributions indicated the diminished vortex intensity, while the periodic organization of the shedding became less distinct at higher rotation rates. Turbulence kinetic energy and Reynolds stress correlations presented that surface modifications, particularly at (3 = 30 degrees, 45 degrees and 60 degrees, enhanced shear layer energization, delayed flow separation and disrupted wake symmetry at alpha >= 0.84. The combination of rotation and surface texturing is therefore effective in reshaping wake dynamics and attenuating large scale vortex structures, offering practical implications for flow control applications.Article Analysis of the Azimuth Angles of a Medium-Scale Pv System in Non-Ideal Positions for Roof Application(2023) İspir, Murat; Bakırhan, Mahmud; Aksoy, Muharrem HilmiThe installation of photovoltaic (PV) panels on building roofs has seen a significant increase in recent years due to the rising cost of conventional energy sources. This shift towards renewable energy sources has been driven by the urgent need to mitigate the effects of climate change. PV applications is one of the most sustainable and cleanest sources of renewable energy, producing no greenhouse gas emissions during operation. By reducing reliance on fossil fuels, the use of PV panels can help to reduce carbon emissions and lower the overall carbon footprint of buildings. In addition to the environmental benefits, the installation of PV panels can also provide economic benefits, such as reduced energy costs and increased property value. In the past, installations were mostly made in the direction of the south, but now the roofs of the buildings facing west, east, and even north are also considered for PV panel installations. In this study, a grid-connected PV system with an installed power of 148 kWp at the Konya Technical University (KTUN) campus is modeled by PVsyst software. The PV systems' performance on building roofs oriented in different geographical directions (north, south, east, and west) with a 30° fixed tilt angle was investigated. In the modeling, the solar irradiation coming to the surfaces of the PV panels, electricity production values, performance ratios, and their economic feasibility were calculated. The highest effective irradiation value on the panel surface was obtained from the system facing south, found as 1964.4 kWh/m². It is 20.77%, 22.87%, and 73.48% higher than the solar irradiation obtained at -90°, +90°, and 180° azimuth angles, respectively. It is concluded that the electricity generation amounts of PV systems highly depend on the azimuth angle. Similarly, the highest annual electricity production was obtained from the system installed in the 0° azimuth angle found as 254.77 MWh. The annual total electricity generation is 19.66%, 22.55%, and 69.41% higher in systems modeled toward the east, west, and north, respectively. Performance ratio, defined as the ratio of radiation coming to the panel surface and the electricity produced, has relative values between 0.843 and 0.862 for four different azimuth angles. Furthermore, as an economic analysis, the Basic Payback Period (BPP) of the projects was found as 6.92 years, 4.08 years, 4.88 years, and 5.00 years for the systems modeled in the north, south, east, and west directions, respectively. It can be concluded that the most suitable orientation is south, and the other two directions, east, and west, can also be considered feasible.Article Citation - WoS: 9Citation - Scopus: 8Experimental Study on Cylinder Wake Control Using Forced Rotation(Elsevier B.V., 2024-03-01) Aksoy, M.H.; Yagmur, S.; Dogan, S.; Goktepeli, I.; Ispir, M.The study focused on the flow over a rotating circular cylinder in the context of flow control. Particle Image Velocimetry was employed to examine flow characteristics at 2.5 × 103 ≤ Re ≤ 10 × 103. The rotation rates (α) were considered up to 1.57. The mean drag coefficients (CD‾) and Strouhal numbers (St) were examined. The vortex formation length was obtained as approximately 2.1 times the cylinder diameter for α = 1.57. For the stationary cylinder, the length was 1.2 times the diameter from Re = 2.5 × 103 to Re = 10 × 103. Forced rotation enhanced the momentum for the boundary layer and postponed the flow separation on the upper side of the body, leading to flow attachment at α = 1.57. The values decreased from CD‾ = 1.029 to CD‾ = 0.907 as α increased from 0 to 0.39 due to the shrinkage of the wake at Re = 10 × 103. Drag reduction was 3.5 % for α = 0.13, 5.7 % for α = 0.26, and 11.8 % for α = 0.39 thanks to active flow control. The St was attained as 0.17 ≤ St ≤ 0.21 for Re varied, while it remained relatively stable for different α values at the same Re. © 2024 Elsevier LtdArticle Flow Patterns Around a Sphere in Terms of Wall Proximity(Sakarya University, 2025) Goktepelı, Ilker; Aksoy, Muharrem Hilmi; Ispir, MuratFlow over a sphere exhibits three-dimensional phenomena even at lower values of Reynolds number (Re). Nonetheless, three-dimensional flow structures may also be affected by boundary layers on the rough walls. For this reason, the effects of wall proximity are very significant for the present case. Regarding these issues, flow characteristics of a sphere have been examined for several gap ratios from G* = 0.01 to G* = 2 at Re = 250. The influence of jet flow between the sphere and the wall has increased by decreasing the gap ratio. Although symmetrical flow patterns have been observed for G* = 1 and G* = 2, this situation is not valid for G* ≤ 0.5 in the present study. It is clearly observed in the wake regions for G* ≤ 0.25 and the positive cross-stream velocity components become more dominant, especially for G* = 0.1 and G* = 0.25, respectively. The positive spanwise vorticity component becomes more dominant; however, the negative one is more dominant for G* ≤ 0.1 in terms of gap ratios. For the case of G* ≤ 0.05, the drag coefficients are less than CD = 0.47 and these values are so close to each other. For G* = 0.1, it is around CD = 0.5 for the present problem. By increasing the gap ratios, drag coefficient values also indicated an increasing trend. Moreover, CD = 0.579 has been attained for the case of G* = 0.25 and it is approximately CD = 0.68 for G* = 0.5 as observed. On the other hand, the values of G* = 1 and G* = 2 approached the values of the uniform flow conditions and the effect of the wall proximity by the boundary layer of the bottom surface disappeared.
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Research Topics
Domains
Physical Sciences
Fields
EngineeringEnergyComputer Science
Subfields
Computational MechanicsRenewable Energy, Sustainability and the EnvironmentArtificial IntelligenceAerospace Engineering
Specific Research Areas
Fluid Dynamics and Vibration Analysis
Photovoltaic System Optimization Techniques
Solar Radiation and Photovoltaics
Aerodynamics and Fluid Dynamics Research
Fluid Dynamics and Turbulent Flows
Sustainable Development Goals
7AFFORDABLE AND CLEAN ENERGY
7
Research Products
13CLIMATE ACTION
1
Research Products
9INDUSTRY, INNOVATION AND INFRASTRUCTURE
1
Research Products
Documents
10
Citations
51
h-index
4
Documents
9
Citations
39
Publication Collaboration
| Affiliation Name | Count |
|---|---|
| Konya Technical University | 17 |
| Adana Science and Technology University | 2 |
| Maulana Abul Kalam Azad Institute of Asian Studies | 2 |
| Doğuş University | 1 |
| Istanbul Aydın University | 1 |
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Data obtained from OpenAlex
| Journal | Count |
|---|---|
| Physics of Fluids | 2 |
| Ocean Engineering | 2 |
| Energies | 1 |
| European Journal of Mechanics B-Fluids | 1 |
| Flow Measurement and Instrumentation | 1 |
Current Page: 1 / 5
Scholarly Output
24
Articles
24
Views / Downloads
39/46
Supervised MSc Theses
0
Supervised PhD Theses
0
WoS Citation Count
41
Scopus Citation Count
58
Patents
0
Projects
0
WoS Citations per Publication
1.71
Scopus Citations per Publication
2.42
Open Access Source
13
Supervised Theses
0
Scopus Quartile Distribution
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