Makine Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/263
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Article Citation - WoS: 7Citation - Scopus: 7Development and Experimental Investigation of Electrochemical Drilling Method Using Rotary Tube Tool(Gazi Univ, Fac Engineering Architecture, 2013) Ozerkan, H. Bekir; Çoğun, Can; Cogun, Can; Mekatronik MühendisliğiIn this study, a new hybrid electrochemical drilling (ECD) method, based on electrochemical machining in nonconventional machining processes, was developed. In the developed method, tube tool makes rotary motion together with inner through hole flushing. A small scale prototype ECD machine has been designed and manufactured to test the developed method. One of the important features of the new system is the regulation of tool feed rate using current feedback control. The Hadfield (manganese) steel, whose strain hardening behavior makes it very difficult to machine with conventional methods, and AISI 1040 steel, whose machinability is fairly good, were drilled using the prototype machine and results were compared. Workpiece material removal rate increased with the increasing machining voltage, tool rotational speed, electrolyte concentration and flushing pressure in both types of steels. Average radial overcut values increased with the rotational speed of the tool. The AISI 1040 steel hole geometries were regular than that of Hadfield steel. Experimental results showed that deep holes can be drilled successfully with the proposed hybrid ECD method.Article Citation - WoS: 3Citation - Scopus: 3Empirical and Statistical Modeling of Heat Loss From Surface of a Cement Rotary Kiln System(Gazi Univ, Fac Engineering Architecture, 2013) Simsek, Baris; Altunok, Taner; Simsek, Emir H.; Altunok, Taner; Makine MühendisliğiIn branches of industry too much energy consuming such as cement sector, controlled use of energy, only it is possible to know how energy is distributed in the system. In cement production process, a large portion of the heat losses which is due to energy consumption consist of convection and radiation heat losses from the surface of rotary kiln. In this study, empirical equation was derived for heat loss from surface of rotary kiln in a cement factory using empirical equations and statistical modeling techniques by the help of temperatures measured surface of rotary kiln. Measured with thermal cameras and the data necessary for experimental modeling was obtained the factory central control room. Total heat loss of system was calculated using Matlab. Statistical analysis related to results was carried out by Minitab 15.1.1 program. It was concluded that heat losses throughout rotary kiln increased toward the center of the kiln.Article Citation - WoS: 3Citation - Scopus: 4Numerical Analysis of a Commercial Display Cabinet With Air Curtain(Gazi Univ, Fac Engineering Architecture, 2011) Caliskan, Sinan; Altunok, Taner; Altunok, Taner; Baskaya, Senol; Gungunes, H. Murat; Makine MühendisliğiMaintaining food temperatures below critical values is the important maximising the high quality display life of chilled foods. Air curtains are especially used in stores and retailer supermarkets as barrier systems to seperate inner and outer spaces from each other. For both air quality and energy saving, it is crucial that the air transfer between these two spaces are at minimum. Minimization of air transfer between inner and outer spaces, not only decreases heat transfer but also stabilizes the humidity balance. In this study, numerical analysis of a commercial display cabinet has been carried out. For this purpose PHOENICS, a computational fluid dynamics code, is utilized. Optimum jet system conditions for each of the one jet, two jet and there jet systems has been modified according to temperature change of the air, and comparisons among them have been made. The results indicate that, the results the both CFD analysis and experimental results are almost equal and refrigeration systems with three jets is required to obtain the necessary temperature values to keep products fresh in display cabinets, especially because they can distribute temperature in a homogeneous way, meaning that the temperature value is the best ideal system at every point in the cabinet with three jets.Article Citation - Scopus: 5Fused Filament Fabrication in Cad Education: a Closed-Loop Approach(Sage Publications inc, 2025) Totuk, Onat Halis; Selvi, Ozguen; Akar, SametIntegrating low-cost fused filament fabrication 3D printing as a foundation for learning 3D modelling is explored. This method blends traditional computer aided design (CAD) instruction with additive manufacturing possibilities. Experimental results demonstrate increased comprehension speed and reduced learning time. This hands-on approach empowers students by enabling direct engagement with the modelling process. Analogous to reverse engineering, the strategy instructs engineering students from final product to model creation, closing the gap between theory and practice. Incorporating 3D printing bridges this divide, enhancing understanding, creativity and problem-solving. The study underscores technology's influence on learning strategies, aligning with the surge of 3D printing in education. Results link advanced design technology usage to improved student performance, with 3D-printed materials yielding 45% higher grades and 30% faster task completion. This study advocates curricular advancement for design-focused careers through enhanced technology integration and favourable 3D printing model reception.Article Citation - WoS: 10Citation - Scopus: 11Analysis of Heat Transfer Enhancement of Passive Methods in Tubes With Machine Learning(Sage Publications Ltd, 2024) Ayli, Ece; Turkoglu, Hasmet; Yapici, Ekin Ozgirgin; Özgirgin Yapıcı, EkinThis 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.Article Citation - WoS: 5Citation - Scopus: 6Prediction of the Heat Transfer Performance of Twisted Tape Inserts by Using Artificial Neural Networks(Korean Soc Mechanical Engineers, 2022) Kocak, Eyup; Ayli, EceA numerical study is undertaken to investigate the effect of twisted tape inserts on heat transfer. Twisted tapes with various aspect ratios and single, double, and triple inserts are placed inside a tube for Reynolds numbers ranging from 8000 to 12000. Numerical results show that the tube with a twisted tape and different numbers of tape is more effective than the smooth tube in terms of thermo-hydraulic performance. The highest heat transfer is achieved with the triple insert, with the highest turning number and an increment of 15 %. Then, an artificial neural network (ANN) model with a three-layer feedforward neural network is adopted to obtain the Nusselt number on the basis of four inputs for a heated tube with a twisted insert. Several configurations of the neural network are examined to optimize the number of neurons and to identify the most appropriate training algorithm. Finally, the best model is determined with one hidden layer and thirteen neurons in the layer. Bayesian regulation is chosen as the training algorithm. With the optimized algorithm, excellent precision for measuring the output is provided, with R2 = 0.97043. In addition, the optimized ANN architecture is applied to similar studies in the literature to predict the heat transfer performance of twisted tapes. The developed ANN architecture can predict the heat transfer enhancement performance of similar problems with R2 values higher than 0.93.Article Kinematic Analyses of Metallic Plate Perforation by Penetrators With Various Nose Geometries(defence Scientific information Documentation Centre, 2022) Akyurek, T.This study analyses kinematics of a metallic plate perforation by a penetrator with truncated ogive nose geometry to find solutions also to blunt, conical, ogive, and hemi-spherical nosed penetrators. Plugging, ductile hole enlargement, dishing, and petal forming failure modes are used in the analyses. Acceleration throughout perforation is calculated by using the related failure mode, analytical model, and the target-penetrator interaction geometry. Depending on the failure model; back lip and front lip formation during ductile hole enlargement, plug formation during plugging, and deflection of target plate during dishing is also analysed. Analyses are based on projectile???s equation of motion, momentum and energy equations, and projectile-target plate interactions. The analyses results for selected cases, with the impact velocity range 215-863 m/s, are compared with the test data. The residual velocity estimation for a strike velocity is close to the related test data with an error of 0.3-2.2 %, except for conical nosed penetrators at impact velocities approaching the ballistic limit velocity.Article Citation - WoS: 1Citation - Scopus: 1Analyses of Plate Perforation for Various Penetrator-Target Plate Combinations(Korean Soc Mechanical Engineers, 2022) Akyurek, TurgutIn this study, kinetics and kinematics of perforation process for various penetrator-target plate combinations is analyzed, a methodology in a flow chart format to decide on failure mode, and for each failure mode, an appropriate combined analytical model that requires only common test data is proposed. The proposed methodology and analytical models that are recommended for the related failure mode are assessed by using a huge amount of test data from the literature. The penetrator-target plate configurations cover the penetrators with ogive, conical, hemi-spherical and blunt noses, at different plate thicknesses, and plate thickness to penetrator diameter ratios, made of different metallic materials. Analyzed failure modes include ductile hole enlargement, plugging, dishing, and petal forming. Assessment is done for impact velocities ranging between 215-863 m/s. The estimations based on the proposed flow chart and recommended failure models are in good agreement with the related test data and numerical analysis results.Article Citation - WoS: 8Citation - Scopus: 8Supervised Learning Method for Prediction of Heat Transfer Characteristics of Nanofluids(Korean Soc Mechanical Engineers, 2023) Kocak, Eyup; Ayli, EceThis study focuses on the alication and investigation of the predictive ability of artificial intelligence in the numerical modelling of nanofluid flows. Numerical and experimental methods are powerful tools from an accuracy point of view, but they are also time- and cost-consuming methods. Therefore, using soft-computing techniques can improve such CFD drawbacks by patterning the CFD data. After obtaining the aropriate ANN and ANFIS architecture using the CFD data, many new data can be created without requiring numerical and experimental methods. In the scope of this research, the FCM-ANFIS and ANN methods are used to predict the thermal behaviour of the turbulent flow in a heated pipe with several nanoparticles. A parametric CFD study is carried out for water-TiO2, water-CuO, and water-SiO2 nanofluid through a pipe. The Reynolds number is varied between 7000 and 15000, and the nanofluid concentration is varied between 0.25 % and 4 %. The effects of using nanofluid on local values of Nusselt number and shear stress distribution were investigated. Numerical results indicate that with the increasing nanoparticle volume fraction of nanofluid, the average Nusselt number increases, but the required pumping power also increases. The obtained soft computing results demonstrate that the FCM clustering ANFIS has given better results both in training and testing when it is compared to the ANN architecture with an R-2 of 0.9983. Regarding this, the FCM-ANFIS is an excellent candidate for calculating the Nusselt number in heat transfer problems.Article Citation - WoS: 4Citation - Scopus: 4Performance Optimization of Finned Surfaces Based on the Experimental and Numerical Study(Asme, 2023) Ayli, Ece; Kocak, Eyup; Turkoglu, HasmetThis 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.