Aksoy, Muharrem Hilmi
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Aksoy, Muharrem H.
Aksoy, M. Hilmi
Aksoy, M.H.
Aksoy, M. H.
Aksoy, M. Hilmi
Aksoy, M.H.
Aksoy, M. H.
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mhaksoy@ktun.edu.tr
muharremaksoy@gmail.com
muharremaksoy@gmail.com
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02.10. Department of Mechanical Engineering
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Current Staff
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Sustainable Development Goals
7
AFFORDABLE AND CLEAN ENERGY
4
Research Products
9
INDUSTRY, INNOVATION AND INFRASTRUCTURE
3
Research Products
13
CLIMATE ACTION
2
Research Products
Documents
35
Citations
508
h-index
14
Documents
23
Citations
286
Scholarly Output
28
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23
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1/0
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2
Supervised PhD Theses
0
WoS Citation Count
94
Scopus Citation Count
140
WoS h-index
6
Scopus h-index
7
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0
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2
WoS Citations per Publication
3.36
Scopus Citations per Publication
5.00
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14
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2
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| Journal | Count |
|---|---|
| Physics of Fluids | 2 |
| Applied Engineering Letters | 2 |
| Advanced Engineering Letters | 1 |
| Applied Ocean Research | 1 |
| European Journal of Mechanics B-Fluids | 1 |
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28 results
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Now showing 1 - 10 of 28
Article Citation - WoS: 4Citation - Scopus: 3The Groove Effect on Wake Characteristics of Rotating Cylinders(American Institute of Physics, 2024) 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 Citation - WoS: 7Citation - Scopus: 7Reconstruction of Flow Field With Missing Experimental Data of a Circular Cylinder Via Machine Learning Algorithm(Aip Publishing, 2023) Aksoy, Muharrem Hilmi; Goktepeli, Ilker; İspir, Murat; Cakan, AbdullahIn this study, artificial neural networks (ANNs) have been implemented to recover missing data from the particle image velocimetry (PIV), providing quantitative measurements of velocity fields. Due to laser reflection or lower intensity of particles in the interrogation area, the reconstruction of erroneous velocity vectors is required. Therefore, the distribution of time-averaged and normalized flow characteristics around a circular cylinder has been demonstrated as streamwise and cross-stream velocities at Re = 8000. These velocity components have been given for different regions at x/D = 0.5, x/D = 1.25, x/D = 2, and y/D = 0. These stations have been chosen to estimate missing data for near-wake, mid-wake, far-wake, and symmetry regions. The missing data ratios (A*) for 0.5 <= x/D <= 2 are A* = 3.5%, 7%, and 10%. In addition, these values are A* = 4%, 8%, and 12% for y/D = 0, while A* = 7.5% for the shaded region. The increment of area positively affects the estimation results for near-wake and mid-wake regions. Moreover, the errors tend to decrease by moving away from the body. At y/D = 0, increasing the area negatively influences the prediction of the results. The mean velocity profiles of predicted and experimental data have also been compared. The missing data have been predicted with a maximum percentage error of 3.63% for horizontal stations. As a result, the ANN model has been recommended to reconstruct PIV data.Article Citation - WoS: 1Citation - Scopus: 1Experimental Flow Control Around Circular Cylinders with Porous Media Coatings(Springer Wien, 2025) Goktepeli, Ilker; Ispir, Murat; Aksoy, Muharrem HilmiFlow structures have been experimentally obtained for the circular cylinders with porous media coatings (PMC) at Reynolds number values from Re = 5000 to Re = 10,000. Furthermore, flow characteristics have been exhibited for different contour graphics and the velocity profiles have been indicated at four downstream stations. The regions having minimum streamwise velocity component values approached the circular cylinders by increasing Reynolds numbers. Nevertheless, it is not valid for the cases of PMC1 and PMC2 from Re = 7500 to Re = 10,000. Because of the separated flows from the upper and lower cylinder surfaces, the maximum streamwise velocity components have been attained. The same effect has been observed for the cross-stream velocity component values, and these clusters approached the circular cylinders. As expected, the flow separations caused wake fluctuations. Nonetheless, the cluster sizes have also been decreased by the decrement of Reynolds numbers. It is significant for the occurrence of turbulence intensity in the wake regions of the circular cylinders. However, there is no obvious difference between the bare cylinder and the PMC3 in terms of flow patterns. Another important result is that the coating effect is explicitly exhibited by the increase in Reynolds numbers. As explained by the velocity values, these zones moved away from the bodies due to the decrement of Reynolds numbers. As a parameter, Reynolds number is considerably dominant on the cluster positions. Similar patterns have been approximately observed for PMC1, PMC2 and PMC4 in terms of Reynolds stress correlations.Conference Object Citation - Scopus: 2Cost-Effectiveness of an Automatic Lubrication System for Bearings(Springer Science and Business Media Deutschland GmbH, 2024) Yildiz, S.; Apakhan, M.; Aksoy, M.H.Improper lubrication is a leading cause of bearing failures, accounting for half of all instances. Lubricating bearings with grease or oil forms a protective film that prevents direct metal-to-metal contact, reducing friction and overheating, and prolonging the bearing’s lifespan. Lubrication also acts as a barrier against foreign particles and wear. In this study, an analysis of automatic lubrication in a milling plant was carried out and compared to manuel lubrication. A milling factory with 22 roller mills with a total production capacity of 450 tons/day is considered. It is calculated that the failure of eight bearings in each mill roller due to lubrication issues results in a substantial cost of $39,000 over a two-year period. The Automatic lubrication system named “SmartLub” regulates lubricant quantity, timing, and application points, ensuring optimal lubrication. The choice of the oil pump was determined by considering both the viscosity of the oil and the head loss within the piping system utilized. By adhering to calculated frequencies, the system extends bearing service life to four years. Furthermore, the manual system reduces labor costs by $400 per roller mill every two years, while unplanned downtimes caused by lubrication issues are minimized. The automatic system eliminates the need for bi-monthly one-day shutdowns in the conventional lubrication systems, saving a total of six days per year. With an estimated lifespan of 20 years, the system achieved a payback period of 1.23 years, demonstrating its cost-effectiveness and long-term benefits. Overall, automation in bearing lubrication enhances machine efficiency, reduces spare parts and maintenance costs, and ensures optimal lubrication in the grain milling sector. Its implementation leads to extended bearing lifespan, reduced downtime, and improved profitability. © 2024, The Author(s), under exclusive license to Springer Nature Switzerland AG.Article Effect of Scourer Screen Patterns on the Wheat Husk Removal Efficiency(The Association of Intellectuals for the Development of Science in Serbia "The Serbian Academic Center" Novi Sad, 2022) Bal, D.; Bakırhan, M.; Apakhan, M.; Ekem, H.; Şahin, Ö.S.; Aksoy, M.H.The scourer machines remove wheat husk contaminated with pesticides and other impurities that adversely affect product quality and shelf life. For this purpose, at least one scourer machine is used in each industrial grain flour factory, depending on the capacity. The efficiency of these machines is highly dependent on the surface texture and scourer screen patterns. In this study, the efficiency of the wheat scourer machines with various wall patterns and meshes was investigated experimentally. The investigation employed six distinct types of scourer screens. Type-4 has produced the best results in fractured grain rate, whereas Type-2 has produced the best in ash content. It was revealed that wheat's scouring efficiency and physical and chemical properties vary depending on the scourer screen pattern. © 2022 by the authors.Article Citation - WoS: 2Impact of Tilt Angle on the Performance of the Photovoltaic Systems for Different Row Spacing(Gazi Univ, 2023) Aksoy, Muharrem Hilmi; İspir, Murat; Yeşil, EminThe optimum tilt angle for a photovoltaic (PV) system depends on the row spacing because it affects the amount of shading on the panels. This study modeled PV systems for four different panel row spacings of 2 m, 2.5 m, 3 m, and 4 m in a fixed 3000 m2 area in Konya province, Turkey. For different panel row spacings, the system performances were compared using a constant tilt angle of 35 degrees, expressed as a proper angle for PV installations at the considered location. In addition, the optimum tilt angle is found for four different cases in terms of electricity generation. In systems with 35 degrees tilt angles at electricity were produced annually as 622.77 MWh, 566.49 MWh, 495.36 MWh, and 385.72 MWh, respectively, for panel row spacings of 2 m, 2.5 m, 3 m, and 4 m. In addition, these electricity productions are 6.19%, 4.41%, 2.56%, and 0.92% higher with optimum tilt angles as 1 degrees, 15 degrees, 21 degrees and 27 degrees. Similarly, the Performance Ratio (PR) values obtained with the optimum angles are 20.61%, 8.39%, 4.12%, and 1.44%, higher than the fixed tilt angle cases. According to the economic analysis, systems with a fixed tilt angle for these panel row spacings pay back themselves in 5.13, 4.67, 4.44, and 4.28 years, respectively, while systems at optimum angles pay back themselves in a shorter time by 5.83%, 4.26%, 2.49%, and 0.91%. Furthermore, the highest NPV/INV, IRR, and ROI values were obtained from the system with 3 m panel row spacing with the optimum tilt angle of 21 degrees as 0.915, 20.42%, and 91.57%, respectively, which is techno economically found to be the most feasible case.Conference Object Citation - WoS: 5Cfd Modelling of Industrial Air Curtains With Heating Unit(E D P SCIENCES, 2019) Aksoy, Muharrem Hilmi; Yağmur, Sercan; Doğan, SercanIndustrial air curtains are used to prevent air from moving from one space to another space or to environment. The most common used type is downward-facing blower fan mounted over the entrance of a building, or an opening door between two spaces conditioned at different temperatures. In many factories and industrial buildings, heating or cooling applications are difficult due to the huge doors. These huge doors cause heat loses with convection phenomena of the inside air. In this study an air curtain having heater unit is analyzed numerically by CFD. The height of the air curtain from the bottom side is vary between 2.5 m, 3 m, 4m, 5m and 6 m mounted over the entrance door of the conditioned volume. For CFD studies proper mesh structure is created on the flow domain and Shear Stress Transport (SST) k-omega models were used in Unsteady Reynolds Averaged Navier-Stokes (URANS) computations. The blowing temperature of the air curtain has adjusted to 60 degrees C with the inside temperature was aimed to kept at +7 degrees C while the outside temperature was-5 degrees C. It is found that there is less flow occurred to the environment from conditioned volume at 2.5 3, 4 and 5 meter height cases. In these cases, the air curtain also contributes the heating of the conditioned room. But some ratio of the air flows through the atmosphere and the room cannot kept at the +7 degrees C initial temperature at 6 m case. It is also found that the heating ratio at different blowing heights differs between 0,89-1,98 comparing the case without an air curtain.Article Solar Radiation Estimation Using Anfis Model: Evaluation of Membership Function Types and Data Selection(Springer Nature, 2024) Unal, R.E.; Guzel, M.H.; Sen, M.A.; Aksoy, M.H.This study proposed a model for estimating monthly solar radiation values using the adaptive network-based fuzzy inference systems (ANFIS-SR). The ANFIS-SR model is obtained by training the meteorological measurement data from the Adana province from 2017 to 2021. The monthly average sunshine duration and ambient temperature are inputs for the ANFIS-SR. The investigation evaluates the impact of different membership functions and data selection methodologies for training and testing on the ANFIS-SR outcomes. Four types of membership functions, Triangular (Trim), Gaussian, Trapezoidal, and Generalized Bell-Shaped (Gbell), are considered to study the input's influence. Additionally, two data selection cases are examined: one involving a serial date (S cases) arrangement and the other with a random (R cases) order. According to the errors, Gbell ensures higher estimating performance with the lowest error than other membership functions in training and testing data in S cases. In the case of R, Gbell is more successful in the training, while Trim can provide better estimates on the testing data. The test results show that the mean absolute percentage error and regression values are 4.364% and 0.984 for S cases and 4.265% and 0.981 for R cases, respectively. According to the obtained results, the Gbell membership function provides more solar radiation prediction performance than the others for the examined location. It also shows that random data selection outperforms serial data selection. The results prove that the proposed model ANFIS-SR can effectively model solar radiation estimation within an acceptable error range, thus offering substantial application potential in this field. © The Author(s) under exclusive licence to Iranian Society of Environmentalists (IRSEN) and Science and Research Branch, Islamic Azad University 2024.Article Citation - Scopus: 14Techno-Economic Feasibility of Different Photovoltaic Technologies(Serbian Academic Center, 2023) Aksoy, Muharrem Hilmi; Ispir, MuratThis study modeled monocrystalline (mono-Si), polycrystalline (poly-Si), and amorphous silicon (a-Si) Photovoltaic (PV) systems with a 300 kWp installed power using PVsyst software in Konya province, Turkey. The system’s electricity generation was calculated and compared with different PV technologies. In addition, an economic analysis for a 25 year lifespan was made with the obtained data. The annual global horizontal radiation (GI) and effective global irradiation (GE) are found to be 2001.7 kWh/m² and 1949.6 kWh/m², respectively. The highest yearly total electricity production was obtained from mono-Si, with a value of 513.91 MWh. This value is 1.91% and 3.07% higher than poly-Si and a-Si, respectively. Since the Performance Ratio (PR) values are proportional to the generated electricity and incoming irradiation to the surface of the PV panels, it calculated 0.853, 0.847, and 0.830 for mono-Si, poly-Si, and a-Si, respectively. According to the basic payback method, the economic analysis showed that mono-Si and poly-Si pay off in about 5.8-5.9 years, while a-Si pays off in 9,1 years. A net profit of $1.5 million, $1.45 million, and $1.1 million was obtained from mono-Si, poly-Si, and a-Si, respectively. It was concluded that the ratio of income values to investment cost was 253%, 244.77%, and 126.6%, respectively. Therefore, it was concluded that mono-Si and poly-Si are economically quite feasible for small and medium-scale PV systems, but a-Si is still not feasible due to lower efficiency and higher costs. © 2023 Published by the Serbian Academic Center.Article EFFECT OF AZIMUTH ANGLE ON THE PERFORMANCE OF A SMALL-SCALE ON-GRID PV SYSTEM(2022) Aksoy, Muharrem Hilmi; Çiylez, İsmail; Ispir, MuratAbstract: In this study, the effective solar irradiation on the PV surface, electricity generation, and performance ratios of a small-scale system were investigated for a 100 kW on-grid PV system in Konya, Turkey, by PVsyst software. Five different azimuth angles as -30°, -15°, 0°, 15°, and 30° were investigated for no-shading simulations with a fixed optimum tilt angle of 33°. As a result, the highest effective solar radiation comes to the system with an azimuth of 0° as 1966.4 kWh/m², which is 2.12%, 0.46%, 0.79%, and 2.66% greater than the other azimuth angles of -30°, -15°, 15° and 30°, respectively. On the other hand, it is seen that the highest energy production is obtained from the system with an azimuth angle of 0° with annual energy of 174.33 MWh. This value is 1.91%, 0.37%, 0.89%, and 2.8% greater than the other azimuth angles of -30°, -15°, 15°, and 30°, respectively. In addition, to evaluate the shading effect on the performance of the PV panels, two different panel spacings as, 4 m and 8 m, were also considered. It was seen that the electricity generation with an 8 m span system was 8.88% better than the 4m. Another finding is that the height of the panels is negligible according to electricity generation. Finally, the highest performance ratio is obtained from the azimuth angle of 0°, as 0.857.
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