Makine Mühendisliği Bölümü

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Citation Count: Koçak, Eyüp; Aylı, Ece; Türkoğlu, Haşmet (2022). "A Comparative Study of Multiple Regression and Machine Learning Techniques for Prediction of Nanofluid Heat Transfer", JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS, Vol. 14, No. 6.
A Comparative Study of Multiple Regression and Machine Learning Techniques for Prediction of Nanofluid Heat Transfer
(2022) Koçak, Eyüp; Aylı, Ece; Türkoğlu, Haşmet; 283455; 265836; 12941
The aim of this article is to introduce and discuss prediction power of the multiple regression technique, artificial neural network (ANN), and adaptive neuro-fuzzy interface system (ANFIS) methods for predicting the forced convection heat transfer characteristics of a turbulent nanofluid flow in a pipe. Water and Al2O3 mixture is used as the nanofluid. Utilizing fluent software, numerical computations were performed with volume fraction ranging between 0.3% and 5%, particle diameter ranging between 20 and 140 nm, and Reynolds number ranging between 7000 and 21,000. Based on the computationally obtained results, a correlation is developed for the Nusselt number using the multiple regression method. Also, based on the computational fluid dynamics results, different ANN architectures with different number of neurons in the hidden layers and several training algorithms (Levenberg-Marquardt, Bayesian regularization, scaled conjugate gradient) are tested to find the best ANN architecture. In addition, ANFIS is also used to predict the Nusselt number. In the ANFIS, number of clusters, exponential factor, and membership function (MF) type are optimized. The results obtained from multiple regression correlation, ANN, and ANFIS were compared. According to the obtained results, ANFIS is a powerful tool with a R-2 of 0.9987 for predictions.
Citation Count: Türkoğlu, Haşmet. "Analysis and simplified modelling of simulation of tests for mediumduty truck collision with twin antiram bollards", Trabzon: 5 th International Anatolian Energy Symposium.
Analysis and simplified modelling of simulation of tests for mediumduty truck collision with twin antiram bollards
(2020) Türkoğlu, Haşmet; 12941
Citation Count: Özgirgin Yapıcı, Ekin; Aylı, Ece; Türkoğlu, Haşmet (2024). "Analysis of heat transfer enhancement of passive methods in tubes with machine learning", Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, Vol. 238, No. 8, pp. 3613-3633.
Analysis of heat transfer enhancement of passive methods in tubes with machine learning
(2024) Özgirgin Yapıcı, Ekin; Aylı, Ece; Türkoğlu, Haşmet; 31329; 265836; 12941
This study investigates the efficacy of machine learning techniques and correlation methods for predicting heat transfer performance in a dimpled tube under varying flow conditions, including the presence of nanoparticles. A comprehensive numerical analysis involving 120 cases was conducted to obtain Nusselt numbers and friction factors, considering different dimple depths and velocities for both pure water and water-Al2O3 nanofluid at 1%, 2%, and 3% volume concentrations. Utilizing the data acquired from the numerical simulations, a correlation equation, SVM ANN architectures were developed. The predictive capabilities of the statistical approach, ANN, and SVM models for Nusselt number distribution and friction factor were meticulously assessed through mean average percentage error (MAPE) and correlation coefficients (R2). The research findings reveal that machine learning techniques offer a highly effective approach for accurately predicting heat transfer performance in a dimpled tube, with results closely aligned with Computational Fluid Dynamics (CFD) simulations. Particularly noteworthy is the superior performance of the ANN model, demonstrating the most precise predictions with an error rate of 2.54% and an impressive R2 value of 0.9978 for Nusselt number prediction. In comparison, the regression model achieved an average error rate of 6.14% with an R2 value of 0.8623, and the SVM model yielded an RMSE value of 2.984% with an R2 value of 0.9154 for Nusselt number prediction. These outcomes underscore the ANN model’s ability to effectively capture complex patterns within the data, resulting in highly accurate predictions. In conclusion, this research showcases the promising potential of machine learning techniques in accurately forecasting heat transfer performance in dimpled tubes. The developed ANN model exhibits notable superiority in predicting Nusselt numbers, making it a valuable tool for enhancing thermal system analyses and engineering design optimization.
Citation Count: Elibol, Emre Aşkın; Türkoğlu, H. (2017). " Gözenekli Düz Bir Yüzeye Çarpan Jetin Sayısal Olarak İncelenmesi", Karadeniz Fen Bilimleri Dergisi, Vol. 7, No.1, pp.1-9.
Gözenekli Düz Bir Yüzeye Çarpan Jetin Sayısal Olarak İncelenmesi
(2017) Elibol, Emre Aşkın; Türkoğlu, Haşmet; 12941
Bu çalışmada, gözenekli malzeme ile kaplanmış sabit sıcaklıkta tutulan düz levha üzerine çarpan jetin akış ve ısı transferine etkileri nümerik olarak incelenmiştir. Birbirine paralel olarak duran, iki yatay levhadan biri olan alt levha, gözenekli bir tabaka ile kaplanmış ve üst levhanın ortasında bulunan lüleden çıkan hava jeti alt levhaya çarptırılmıştır. Gözenekli tabakanın katı matrisi ile akışkan arasında yerel ısıl denge olduğu kabul edilerek, laminar ve kararlı rejim için çözümler yapılmıştır. Gözeneklilik, gözenekli tabakanın kalınlığı ve jet Reynolds sayısının farklı değerlerinde simülasyonlar yapılarak, bu parametrelerin yerel Nusselt sayısı’na (Nu) etkileri analiz edilmiştir. Sonuçlar, yatay (x) yönde; yerel Nu sayıları ve sıcak alt levhadan olan ısı akıları, gözenekli tabaka bulunmayan durum ile karşılaştırılarak yorumlanmıştır. Analizler için yazılım paketi olan ANSYS Fluent yazılımı kullanılmıştır. Sonuçlar, sıcak levha yüzeyinin gözenekli tabaka ile kaplandığı durumlarda, gözenekli malzemenin belirli gözeneklilik ve kalınlık değerleri aralığında olması halinde, ısı transferinin gözenekli tabaka kullanılmayan duruma göre daha etkin olduğunu göstermiştir.
Citation Count: Koçak, Eyüp; Aylı, Ece; Türkoğlu, Haşmet. "Kanat Profili-Silindir Konfigürasyonunun aerodinamik ve aeroakustik performansının sayısal analizi/Numerical Investigation of Aerodynamic and Aeroacoustic Performance on Rod-Airfoil Configuration, 14. Ulusal Tesisat Mühendisliği Kongresi, 2019.
Kanat Profili-Silindir Konfigürasyonunun aerodinamik ve aeroakustik performansının sayısal analizi
(2019) Koçak, Eyüp; Aylı, Ece; Türkoğlu, Haşmet; 12941
Fanlar, rüzgâr ve su türbinleri gibi birçok akım makinesinde ve uçak gövdesi bileşenlerinde akışın fiziğinin ve akustik performansının anlaşılmasında, kanat profili-silindir konfigürasyonlarının akış performansından yararlanılmaktadır. Silindirin arkasında meydana gelen kayma tabakası ayrılmaları ve Von Karman girdapları, kanat girişinde parçalanmakta ve birçok küçük yapılar meydana getirmektedir. Ortaya çıkan akış-katı yüzey etkileşimine bağlı olarak gürültü ve titreşim meydana gelmektedir. Akım makinelerinde geniş bant gürültüsünün en önemli sebebi, türbülanslı akış ve stator kanat giriş ucu etkileşimidir. Bundan dolayı akım makineleri gürültüsünün analizi için, kanat profili-silindir konfigürasyonu modellemesi yapılır. Bu çalışmada, kanat profili dairesel silindirin iz bölgesine yerleştirilerek sayısal simülasyonlar yapılmıştır. Simülasyonlar için Large Eddy Simulation (LES) metodu kullanılmıştır. Sayısal sonuçlar literatürdeki deneysel çalışmalar ile karşılaştırılarak sonuçlar doğrulandıktan sonra, farklı çaplardaki silindirler için simülasyonlar yapılarak, silindir çapının girdap oluşum bölgesi, akış birleşme noktası, akış ayrılma noktası, basınç dağılımı ve ses basınç seviyesi üzerindeki etkileri incelenmiştir. Elde edilen sonuçlar, Strouhal sayısındaki artış ile ses basınç seviyelerinin yükseldiğini göstermiştir.
Citation Count: Turgut, Oguz; Ozcan, Ahmet Cem; Turkoglu, Hasmet, "Laminar Forced Convection Over An Inclined Flat Plate With Unheated Starting Length", Journal of Polytechnic-Politeknik Dergisi, Vol. 22, No. 1, pp. 58-62, (March 2019).
Laminar Forced Convection Over An Inclined Flat Plate With Unheated Starting Length
(Gazi Univ, 2019) Turgut, Oğuz; Özcan, Ahmet Can; Türkoğlu, Haşmet; 12941
Two-dimensional laminar forced convection over an inclined flat plate with an unheated starting length was investigated numerically for both constant surface temperature and constant heat flux boundary conditions. The numerical study was implemented using the commercial software ANSYS Fluent 15.0. Air is used as working fluid. The influence of Reynolds number, inclination angle and the length of unheated plate on velocity and temperature distributions, surface temperature, surface heat flux and local Nusselt number was investigated. The results show that Reynolds number, inclination angle and the length of unheated region of plate play important role on heat transfer from the plate. It is seen that Nusselt number increases with increasing Reynolds number and inclination angle of inclined flat plate but decreases with increasing the length of unheated region of plate.
Citation Count: Aylı, E.; Koçak, E.; Türkoğlu, H. (2023). "Machine Learning Based Developing Flow Control Technique Over Circular Cylinders", Journal of Computing and Information Science in Engineering, Vol.23, No.2.
Machine Learning Based Developing Flow Control Technique Over Circular Cylinders
(2023) Aylı, Ece; Koçak, Eyup; Türkoğlu, Haşmet; 265836; 283455; 12941
This paper demonstrates the feasibility of blowing and suction for flow control based on the computational fluid dynamics (CFD) simulations at a low Reynolds number flows. The effects of blowing and suction position, and the blowing and suction mass flowrate, and on the flow control are presented in this paper. The optimal conditions for suppressing the wake of the cylinder are investigated by examining the flow separation and the near wake region; analyzing the aerodynamic force (lift and drag) fluctuations using the fast Fourier transform (FFT) to separate the effects of small-scale turbulent structures in the wake region. A method for stochastic analysis using machine learning techniques is proposed. Three different novel machine learning methods were applied to CFD results to predict the variation in drag coefficient due to the vortex shedding. Although, the prediction power of all the methods utilized is in the acceptable accuracy range, the Gaussian process regression (GPR) method is more accurate with an R2(coefficient of determination) > 0.95. The results indicate that by optimizing the blowing and suction parameters like mass flowrate, slot location, and the slot configuration, up to 20% reduction can be achieved in the drag coefficient.
Citation Count: Kocak, E., Ayli, E., Türkoglu, H., Numerical Analysis of Aerodynamic and Aeroacoustic Characteristics of Subsonic Rectangular Cavity with Different Aspect Ratios, 5th International Anatolian Energy Symposium, 24-26 March, Trabzon, Turkey, 2020.
Numerical Analysis of Aerodynamic and Aeroacoustic Characteristics of Subsonic Rectangular Cavity with Different Aspect Ratios
(2020) Koçak, Eyup; Aylı, Ece; Türkoğlu, Haşmet; 283455; 265836; 12941
Citation Count: Kahroba, Mitra; Türkoğlu, Haşmet, "Numerical analysis of pulsating circular impinging laminar jet on a planar disc", Isı Bilimi Ve Teknigi Dergisi-Journal Of Thermal Science And Technology, Vol.37, No.2, pp.89-95, (2017).
Numerical analysis of pulsating circular impinging laminar jet on a planar disc
(Turkish Soc Thermal Sciences Technology, 2017) Kahroba, Mitra; Türkoğlu, Haşmet; 12941
In this study, the flow and heat transfer characteristics of pulsating circular air jets impinging on a flat surface were numerically analyzed. The jet velocity pulsated in time. The objective of the work is to investigate the influence of the jet Reynolds number, pulsation amplitude and pulsation frequency on the rate of heat transfer from the target hot surface. For the analysis, a computer program, based on the control volume method and SIMPLE algorithm, was developed. Laminar flow with the time averaged jet Reynolds numbers between 300 and 700 were analyzed. The pulsation amplitude is ranged between 0.0V(0) (steady jet) and 0.8V(0) (m/s) (V-0 is period averaged jet velocity), and the frequency is ranged between 1 and 6 Hz. The nozzle-to-plate distance was kept constant at H/d=3. From the simulation results, it was observed that at any instant of the pulsation period, the local Nusselt number is maximum at the stagnation point, and it decreases along the plate. This decrease in the local Nusselt number is not monatomic as in the steady jet cases. It has local maximum and minimum values (fluctuations) due to the moving recirculating flow regions along the bottom plate. At low frequencies, the time (period) averaged stagnation point Nusselt numbers are lower than the corresponding steady jet Nusselt numbers. However, with the increasing frequency, the stagnation point Nusselt number increases and become higher than the steady jet Nusselt number.
Citation Count: Aylı, Ece; Koçak, Eyüp; Türkoğlu, Haşmet (2021). "Numerical Investigation Of Rod-Airfoil Configuration Aeroacoustic Characteristics Using Ffowcs-Williams-Hawkings Equations", Journal of Thermal Engineering, Vol. 7, No. 2, pp. 58-70.
Numerical Investigation Of Rod-Airfoil Configuration Aeroacoustic Characteristics Using Ffowcs-Williams-Hawkings Equations
(2021) Aylı, Ece; Koçak, Eyüp; Türkoğlu, Haşmet; 12941
The rod-airfoil configuration is a fundamental study to understand sound generation processes and the acoustic phenomena in the application of turbines, fans, and airfoils. In the present research, the noise that is originated by the rod-airfoil configuration is examined using numerical methods which are Large Eddy Simulation (LES), and Reynolds Averaged Navier Stokes (RANS) models, coupled with an FFOWCS-WILLIAMS-HAWKINGS (FW-H) technique. For the RANS method, k-ω SST and Spalart Allmaras (S-A) turbulence models are utilized in order to investigate the capability of different models for the analysis of the aeroacoustic flow field. The ANSYS FLUENT solver is chosen to carry out the numerical simulations. The examined rod and chord diameter Reynolds numbers are 48000 and 480000, respectively and the Mach number is 0.2. Results are obtained for both in the near field and acoustic far-field. The obtained numerical results are verified with an experimental study from the literature, and the results of both approaches are compared with each other and the experiment. Comparisons are performed for mean velocity profiles in the rod and airfoil wakes, pressure spectra and power spectral density. The results obtained show that LES is preferable for this problem as it is capable of capturing the flow separation, reattachments, vortex street, and various length scales of turbulence. Although both RANS and LES methods provide a consistent flow field with experimental methods, the RANS approach overestimates the vortex shedding frequency and Strouhal number. The RANS model predicts the flow field well; however, it overestimates the noise spectra. The LES model predicts satisfactory acoustic spectra. © 2021. Journal of Thermal Engineering. All rights reserved.
Citation Count: Koçak, E.; Türkoğlu, H.; Aylı, E. (2023). "Performance Optimization of Finned Surfaces Based on the Experimental and Numerical Study", Journal of Thermal Science and Engineering Applications, Vol.15, No.9.
Performance Optimization of Finned Surfaces Based on the Experimental and Numerical Study
(2023) Koçak, Eyup; Türkoğlu, Haşmet; Aylı, Ece; 283455; 12941; 265836
This paper presents the findings of numerical and experimental investigations into the forced convection heat transfer from horizontal surfaces with straight rectangular fins at Reynolds numbers ranging from 23,600 to 150,000. A test setup was constructed to measure the heat transfer rate from a horizontal surface with a constant number of fins, fin width, and fin length under different flow conditions. Two-dimensional numerical analyses were performed to observe the heat transfer and flow behavior using a computer program developed based on the OPENFOAM platform. The code developed was verified by comparing the numerical results with the experimental results. The effect of geometrical parameters on heat transfer coefficient and Nusselt number was investigated for different fin height and width ratios. Results showed that heat transfer can be increased by modifying the fin structure geometrical parameters. A correlation for Nusselt number was developed and presented for steady-state, turbulent flows over rectangular fin arrays, taking into account varying Prandtl number of fluids such as water liquid, water vapor, CO2, CH4, and air. The correlation developed predicts the Nusselt number with a relative root mean square error of 0.36%. This research provides valuable insights into the effects of varying Prandtl numbers on the efficiency of forced convection cooling and will help in the design and operation of cooling systems. This study is novel in its approach as it takes into account the effect of varying Prandtl numbers on the heat transfer coefficient and Nusselt number and provides a correlation for the same. It will serve as a valuable reference for engineers and designers while designing and operating cooling systems.
Citation Count: Erşahin, Yasin; Türkoğlu, Haşmet. (2017). "Soğutma Yüküne Bağlı Olarak Set Sıcaklığı Değişen Hava Soğutmalı Soğutma Grubunun Performansının Deneysel İncelenmesi", Soğutma Dünyası, Vol.20, No.78, pp.60-72.
Soğutma Yüküne Bağlı Olarak Set Sıcaklığı Değişen Hava Soğutmalı Soğutma Grubunun Performansının Deneysel İncelenmesi
(2017) Erşahin, Yasin; Türkoğlu, Haşmet; 12941
Alışılmış enerji kaynaklarının global enerji ihtiyacını karşılamadaki yetersizliği, her geçen gün enerji ihtiya- cının artması ve enerji üretiminden kaynaklanan çevre kirliliği gibi sebepler enerji verimliliğinin önemini artır- maktadır. Günümüzde bütün sektörlerde, enerjiyi ola- bildiğince verimli kullanabilecek teknikler geliştirilmeye çalışılmaktadır. Gelişmiş ülkeleri incelediğimizde, ısıt- ma ve soğutma alanındaki önceliklerde ilk sırayı enerji verimliliği almaktadır. Merkezi yaşam alanları için gerekli olan soğutma ih- tiyacı, gün veya sezon içerisinde sürekli değişiklik gös- termektedir. Mahaldeki insan sayısının ve hava hare- ketliliğinin değişmesiyle ihtiyaç olan soğutma yükü de değişmektedir. Mahale bağlı bulunan soğutma grubu- nun bu değişken soğutma yüküne göre kendini ayar- layıp, hızlı bir şekilde reaksiyon vermesi enerjinin daha verimli kullanılmasını sağlamaktadır. Bu çalışmada, standart soğutma grubu kontrol tekniği ve adaptif algoritmalı kontrol tekniği ile kontrol edilen bir soğutma grubunun performansı ve enerji tüketimi, deneysel olarak incelenmiş ve sonuçlar karşılaştırma- lı olarak sunulmuştur. Testlerde, her iki kontrol sistemi için değişken soğutma yükü sağlanması amacıyla ciha- zın evaporatör su giriş sıcaklığı 12-7°C arasında de- ğiştirilerek, soğutma grubu kompresörlerinin devreye girmesi ve devreden çıkması sağlanmıştır. Tam ve kıs- mi soğutma yükleri altında yapılan ölçümlerde, adap- tif kontrol sistemi ile kontrol edilen soğutma grubunun, standart kontrol sistemine göre ortalama %10,72 daha az enerji tükettiği ve toplam ekserji yıkımının ise orta- lama % 6,23 daha az olduğu görülmüştür.

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