Browsing by Author "Koçak, Eyup"

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Evaluating Machine Learning Techniques for Fluid Mechanics: Comparative Analysis of Accuracy and Computational Efficiency
(2024) Koçak, Eyup; Makine Mühendisliği
This study focuses on applying machine learning (ML) techniques to fluid mechanics problems. Various ML techniques were used to create a series of case studies, where their accuracy and computational costs were compared, and behavior patterns in different problem types were analyzed. The goal is to evaluate the effectiveness and efficiency of ML techniques in fluid mechanics and to contribute to the field by comparing them with traditional methods. Case studies were also conducted using Computational Fluid Dynamics (CFD), and the results were compared with those from ML techniques in terms of accuracy and computational cost. For Case 1, after optimizing relevant parameters, the Artificial Neural Network (ANN), Random Forest (RF), and Support Vector Machine (SVM) models all achieved an R² value above 0.9. However, in Case 2, only the ANN method surpassed this threshold, likely due to the limited data available. In Case 3, all models except for Linear Regression (LR) demonstrated predictive abilities above the 0.9 threshold after parameter optimization. The LR method was found to have low applicability to fluid mechanics problems, while SVM and ANN methods proved to be particularly effective tools after grid search optimization.
Kanat Profili-Silindir Konfigürasyonunun aerodinamik ve aeroakustik performansının sayısal analizi
(2021) Türkoğlu, Haşmet; Ayli, Ece; Koçak, Eyup; 265836; Makine Mühendisliği
Fanlar, rüzgâr ve su türbinleri gibi birçok akım makinesinde ve uçak gövdesi bileşenlerinde akışın fiziğinin ve akustik performansının anlaşılmasında, kanat profilisilindir konfigürasyonlarının akış performansından yararlanılmaktadır. Silindirin arkasında meydana gelen kayma tabakası ayrılmaları ve Von Karman girdapları, kanat girişinde parçalanmakta ve birçok küçük yapı 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.
Numerical Acoustic Investigation of Rod-Airfoil Configuration Using Ffowcs-Williams-Hawkings Equations
(2021) Koçak, Eyup; Turkoglu, Hasmet; Ayli, Ece; 265836; Makine Mühendisliği
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-WILLIAMSHAWKINGS (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.
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; Makine Mühendisliği
Performance Evaluation of reverse engineered wind tunnel axial fan
(2020) Ulucak, O.; Kartal, M.; Mendi, C.; Surgun, K.; Günce, C.; Kantar, E.; Koçak, Eyup; Aylı, Ece; 283455; 265836; Makine Mühendisliği