Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Conference Object Determination of Interfacial Heat Transfer Coefficient for a Mixed Convection Heat Transfer in a Vertical Channel Filled With Uniformly Heated Blocks(Begell House Inc., 2015) Çelik, Hasan; Mobedi, Moghtada; Manca,O.; Buonomo,B.The interfacial convective heat transfer coefficient of a periodic porous medium under mixed convection heat transfer is determined computationally by using volume averaging method. The porous medium consists of square blocks in inline arrangement. The continuity, momentum and energy equations are solved in dimensionless form for a representative elementary volume of porous medium and the velocity and temperature fields for different values of Richardson and Reynolds numbers are obtained. Based on the obtained results, the interfacial convective heat transfer coefficient is calculated by using volume average method. The temperature of the solid phase is considered uniform and different than the inlet temperature. A detailed discussion on the effect of the governing dimensionless parameters (i.e. Reynolds, Richardson numbers, and porosity) on the local and average interfacial Nusselt number is done. It is concluded that the local interfacial convective heat transfer coefficient increases with Reynolds number, however the rate of increase depends on Richardson number and porosity. The study is performed for two values of porosity of 0.51 and 0.94. © 2021, Begell House Inc. All rights reserved.Conference Object A Numerical Study on the Determination of the Effects of Pore To Throat Size Ratio on the Thermal Dispersion in Porous Media(Begell House, 2014) Özgümüş, Türküler; Mobedi, Moghtada; Özkol, ÜnverDirect pore-level numerical simulations are widely used to estimate macroscopic properties of fluid flow and heat transfer in porous media. Thermal dispersion is one of the most important macroscopic transport parameters for analyzing convective heat transfer in a porous medium. It should be known in order to predict the macroscopic temperature distribution. In the present study, a microscopic scale analysis is performed for a porous medium with periodic structure. A representative elementary volume is chosen from an infinite medium consists of rectangular rods in inline arrangement. The continuity and momentum equations are solved to obtain flow field and the energy equations for fluid and solid phases are solved to obtain microscopic temperature distributions in two phases. There are velocity and temperature deviations between macroscopic and microscopic local values. Volume averaging method is applied to the computed deviations and thermal dispersion conductivity of porous media is determined. The aim of this study is to analyze the effects of pore to throat size ratio on the longitudinal and transverse thermal dispersion in porous media. The study is performed for representative elementary volumes with different pore to throat size ratios and Reynolds numbers from 1 to 100. The study is performed for high porosity porous media (ε = 0.7 and 0.91). It is shown that the porosity and pore to throat size ratio have more influence on the transverse rather than longitudinal thermal dispersion. © 2014, Begell House Inc. All rights reserved.Book Part Citation - WoS: 1Citation - Scopus: 1A Historical Review of Polyhedral Linkages(Springer, 2024) Kiper, GökhanPolyhedral linkages are linkages that resemble polyhedral shapes at different configurations. This paper summarizes the necessary geometrical fundamentals of polyhedral geometry and presents a historical and critical review of the polyhedral linkage designs available in the literature. Basic definitions of polyhedral geometry and operations are needed to comprehend and design polyhedral linkages. First, early works on polyhedral linkages are presented, where flexible polyhedra with rigid faces and flexible edges are issued. The final part is reserved to conformal polyhedral linkages, which go through shape transformations while plane, dihedral and solid angles are preserved. Conformal polyhedral linkages are examined in four categories: 1) Jitterbug-like linkages with screwing polygonal links connected to each other with dihedral angle preserving links, 2) polyhedral linkages with planar kinematic chains in radial motion planes, 3) polyhedral linkages with planar kinematic chains on faces, that are connected to each other with dihedral angle preserving links, and 4) other conformal polyhedral linkages. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.Conference Object Energy and Exergy Analysis of a Roof-Mounted Photovoltaic System in Gebze-Turkey(Springer, 2024) Khalejan, Seyed Hamed Pour Rahmati; Cankurt, Tolga; Dede, Mehmet İsmet CanThis study investigates the electrical and thermal exergy, power conversion efficiency and exergy efficiency of a roof-mounted photovoltaic (PV) system considering environmental parameters such as solar irradiation, ambient temperature and wind speed over a year. The values of solar exergy and solar potential are obtained by taking into account the solar insolation. Experimental and theoretical results indicate that wind speed and surface temperature have significant effects on the thermal exergy and exergy efficiency of solar PV systems. The mean solar potential in the region was found to be 93%. In addition, the electrical exergy was varied from 9145 W to 40460 W and the thermal exergy of PV systems was varied from 1639 W to 6193 W. While the range of PV power conversion efficiency varies from 6.15% to 11.56% over a year, the range of exergy efficiency varies from 5.31% to 9.78%. © 2024, The Author(s), under exclusive license to Springer Nature Switzerland AG.Conference Object Citation - WoS: 1Citation - Scopus: 1Modeling a Magneto-Rheological Fluid-Based Brake Via a Neural Network Method(Springer international Publishing Ag, 2022) Kucukoglu, Sefa Furkan; Dede, Mehmet Ismet Can; Ceccarelli, MarcoIdentifying the model of a magneto-rheological (MR) fluid-based brake is extremely important for designing and controlling a haptic device with hybrid actuation. Therefore, in this study, an Elman Recurrent Neural Network (ERNN) is designed to understand and model a characterization of an MR fluid-based rotational brake. Three important factors that affect the MR brake's performance are chosen as inputs: current, speed, and the first derivative of the input current. The proposed network is trained, and the performance of the network is tested with three different experimental scenarios. Then, the effect of these inputs on the system is investigated. According to the results, it can be said that the designed ERNN is a good candidate for modelling an MR brake.Conference Object Citation - Scopus: 1Kinematic Representation of a Biomimetic Squid Soft Robot's Arms in a Simulation Environment(Springer international Publishing Ag, 2022) Emet, Hazal; Dede, M. I. CanBiomimetic robot systems have received attention from researchers and in accordance the implementation of soft robotic arms has been studied. Kinematic and dynamic modeling of robots with infinite degrees of freedom is challenging and a number of methods have been proposed. In this work, a procedure is proposed to represent soft robot arm motion in a simulation environment. A biomimetic squid robot is used as a case study. This robot's soft arms are modeled by using the Piecewise Constant Curvature approach. This model is visualized by discretizing the soft arms into a finite number of rigid-body manipulators in MatLab using its 3D animation toolbox.Conference Object Training and Modelling the Non-Linear Behavior of an Mr Brake by Using Rnn and Lstm(VDE Publishing House, 2021) Karabulut, Mehmet Görkem; Küçükoğlu, Sefa Furkan; Dede, Mehmet İsmet CanA magneto-rheological (MR) fluid-based semi-active actuation system, or in other words, an MR-fluid based brake system, was designed for displaying larger amount of resistive forces without jeopardizing the dynamic performance of a haptic interface. The working principle of the MR brake device depends on the viscous fluid called MR fluid that changes its viscosity when exposed to the magnetic field. Thus, generated resistive torque can be controlled via regulating the magnetic field by modifying the electrical current that passes along a coil which provides this magnetic field.Dynamic system modeling is required in order to develop a high-performance control. In this study, modeling methods of an MR-fluid based brake is investigated in terms of its friction and hysteresis characteristics.There are numerous works in the literature in which two well-known learning sequence methods, Recurrent Neural Network (RNN) and Long Short-Term Memory (LSTM), are used for non-linear dynamic system modeling. In the scope of this study, the performance of RNN and LSTM are compared with the Bouc-Wen model which is commonly used in MR-fluid based system modeling. The effect of learning rate and the number of epoch being the important hyper-parameters, for RNN and LSTM models are investigated.In accordance with these information, both methods can be used for the control purposes of a MR-fluid based brake system. © VDE VERLAG GMBH · Berlin · Offenbach.Conference Object Citation - Scopus: 26Optimization of Hip Implant Designs Based on Its Mechanical Behaviour(Springer, 2022) Göktaş, Hasan; Subaşı, Eda; Uzkut, Metin; Kara, Mustafa; Biçici, Hamit; Shirazi, Hadi; Mihçin, ŞenayTotal Hip Arthroplasty (THA) is one of the best advancements in healthcare. THA is required when the hip joint causes immobility and pain. The designed hip implants vary in geometry with different geometrical parameters. The geometry plays an important role in the mechanical behavior of the hip implant. In this study, the optimum selection of hip implant under static loading was evaluated using Finite Element Modeling (FEM). Hip implants with three different stem cross-sections including. (a) elliptic, (b) oval, and (c) trapezoidal were designed using a commercial Computer-Aided Design (CAD) software package. The FEM analysis was carried out via ANSYS R2019 to assess the key mechanical parameters of the implants such as stress distribution and deformation. The results were evaluated for the best stress and strain values. The optimum design had equivalent stress (von Misses) of 258,1 MPa, equivalent strain of 0.004, with total deformation of 0.24 mm and frictional stress of 0.362 MPa producing best values for trapezoidal cross-sectioned design. The findings of this study provided an insight into the selection of appropriate hip implant design with certain geometric design parameters to produce optimum results in clinical applications. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Conference Object Citation - Scopus: 14Mechanical Investigation for the Use of Polylactic Acid in Total Hip Arthroplasty Using Fem Analysis(Springer, 2022) Çelik, Emre; Alemdar, Furkan; Batı, Murat; Daşdemir, Muhammed Furkan; Büyükbayraktar, Onur Alp; Chethan, K.N.; Mihçin, ŞenayPolylactic acid (PLA) is a biodegradable non-toxic, biocompatible polymer used as a popular filament material in biomedical applications with the advance of 3D printing technologies. PLA is considered a suitable implant material due to its contribution to bone regeneration. In this study, the use of PLA in Total Hip Arthroplasty (THA) as a liner material was assessed. In this regard, the PLA liner with different material combinations in THA was examined to provide evidence for its potential. The hip implant prototypewas drawn using a computer-aided design tool then transferred into a commercial finite element analysis (FEA) software. The prototypesconsisted of assemblies of PLA with titanium, chrome cobalt, stainless steels, dense NiTi shape-alloys, and Alumina-Zirconia. Simulations were run under static loading conditions. To evaluate and compare the results for the optimum design; factor of safety, total deformation and von Mises stress analysis were used. The results show that Co-Cr implemented implants produce the highest factor of safety. When Al-Zi combined with PLA, it produced least deformation and reasonable von- Mises stress values. PLA might perform best when used with Al-Zi. As a next step, experimental pre-clinical tests are planned to assess the clinical potential. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Article Citation - Scopus: 1Sizing of Autonomous Wind/Solar Hybrid Energy Conversion Systems for Urla, Turkey(ACTA Press, 2009) Özerdem, Barış; Ekren, OrhanIn this paper, an optimum sizing procedure of autonomous hybrid (wind + solar) energy system is presented which can be used to satisfy the requirements of given load distribution. The main purpose of this study is to find out an appropriate wind-photovoltaic hybrid energy system to satisfy electricity consumption of GSM (Global System for Mobile communication) base station at Izmir Institute of Technology Campus Area, Urla, Izmir, Turkey. To do this, monthly average daily solar radiation and wind speed data are collected. The monthly average wind speeds are measured at 10 m height during 3 years period on Izmir Institute of Technology Campus Area. The monthly average wind speed values are obtained between 5.7 and 7.7 m/s, on the other hand, the monthly average daily value of solar radiations on horizontal surfaces are ranged from 1.4 to 6.9kWh/m2 at Izmir Institute of Technology Campus Area. The hybrid system considered in the present analysis consists of one 5kW nominal power wind energy conversion systems (WECS), 21.82 m2 of photovoltaic (PV) panels (18 mono crystal PV panels each having 75 W power output) together with a battery storage system.