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.Article Citation - WoS: 28Citation - Scopus: 30Bone Marrow Stem Cells Adapt To Low-Magnitude Vibrations by Altering Their Cytoskeleton During Quiescence and Osteogenesis(TUBITAK, 2015) Demiray, Levent; Özçivici, EnginApplication of mechanical vibrations is anabolic to bone tissue, not only by guiding mature bone cells to increased formation, but also by increasing the osteogenic commitment of progenitor cells. However, the sensitivity and adaptive response of bone marrow stem cells to this loading regimen has not yet been identified. In this study, we subjected mouse bone marrow stem cell line D1-ORL-UVA to daily mechanical vibrations (0.15 g, 90 Hz, 15 min/day) for 7 days, both during quiescence and osteogenic commitment, to identify corresponding ultrastructural adaptations on cellular and molecular levels. During quiescence, mechanical vibrations significantly increased total actin content and actin fiber thickness, as measured by phalloidin staining and fluorescent microscopy. Cellular height also increased, as measured by atomic force microscopy, along with the expression of focal adhesion kinase (PTK2) mRNA levels. During osteogenesis, mechanical vibrations increased the total actin content, actin fiber thickness, and cytoplasmic membrane roughness, with significant increase in Runx2 mRNA levels. These results show that bone marrow stem cells demonstrate similar cytoskeletal adaptations to low-magnitude high-frequency mechanical loads both during quiescence and osteogenesis, potentially becoming more sensitive to additional loads by increased structural stiffness.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.Article Fireproofing the Firefighting Robot(Laurin Publishing Co. Inc., 2009) Keçeci, Emin FarukResearchers at the Institute of Technology in Izmir, Turkey, have successfully developed a mechanical firefighter robot that will work inside the flames. The robot uses both passive and active cooling systems that, for a limited time, keep the inner temperature at a safe level for the electronic components inside the device, to survive the flame. The body of the robot is made of aluminum and comprises two shells attached to each other with rods. The robot is controlled with a remote unit by an operator, who can observe the fire via a CCD camera. Control and cooling subsystems will allow the robot to work in these rough conditions. The control system allows the robot to use the navigation system as well as the sensory and cooling systems. The robot will be controlled with radiofrequency communications and is able to break doors and climb stairs to work in upper-level fires.Conference Object Internship Experience for Learning the Operation of a Cable-Driven Robot for Rehabilitation Tasks(Springer, 2019) Carbone, G.; Cafolla, D.; Ceccarelli, M.; Aydınoğlu, Öndercan; Demirel, MuratThis paper describes an example of internship experience at LARM, Laboratory of Robotics and Mechatronics, at University of Cassino and South Latium. In particular, the main focus of this paper is the learning process as basis of a proper internship. Namely, a specific experiential learning approach is proposed as referring to a low-cost servo motor operation task. The learning task is further defined and developed as referring to a real application with a cable-driven robot for rehabilitation tasks, which has been designed and built at LARM in Cassino and under further investigation within Agewell project.Article Citation - WoS: 3Validation on of Local Thermal Equilibrium and Uniform Pressure Assumptions for an Isobaric Adsorption Process in an Adsorbent Bed(Türk Isı Bilimi ve Tekniği Derneği, 2016) Gediz İliş, Gamze; Mobedi, Moghtada; Ülkü, SemraBu çalışmanın amacı, adsorbent yatakta ısı ve kütle transferini analiz etmek için kullanılan yerel ısıl denge ve sabit basınç yaklaşımı varsayımların geçerliliğini araştırmaktır. İçerisinde silika jel partikülleri içeren bir yatak ile su kabı olan bir deney düzeneği tasarlanmış ve adsorpsiyon sürecinde yatağın içinde farklı yerlerde yerel sıcaklık ve basınç ölçülmüştür. Ayrıca, sabit basınç yaklaşımı ve yerel ısıl denge varsayımlara dayalı ısı ve kütle transferi denklemleri çözülmüştür. Sayısal sonuçlar, ilgili deneysel sonuçlarla karşılaştırılmış ve aralarında oldukça iyi bir uyum tespit edilmiştir. Gerçekleştirilen karşılaştırmaya dayanarak, incelenen yatak için iki önemli sonuç şu şekildedir: a) katı madde ve su buharı arasında yerel ısıl denge bulunmaktadır, b) bir yatak içinde parçacıklar arası kütle transferi direnci ihmal edilebilir düzeyde olup konsantrasyonunun ve sıcaklığın belirlenmesi için sabit basınç yaklaşımı geçerlidir. Ayrıca, bu çalışmada sunulan deneysel sonuçlar diğer araştırmacıların sayısal çalışmalarının geçerliliğini doğtulamak için değerli veriler sağlayacaktır.Article Citation - WoS: 6Citation - Scopus: 9Impact of Climate Change on Indoor Environment of Historic Libraries in Mediterranean Climate Zone(Inderscience Enterprises, 2019) Turhan, Cihan; Durmuş Arsan, Zeynep; Gökçen Akkurt, GüldenMost historic library buildings house valuable paper-based collections that are kept in unconditioned environments. This vulnerable cultural heritage is expected to be highly affected by climate change in the future. In this study, indoor microclimate of an unconditioned historic library, Necip Pasa Library (Izmir, Turkey) is analysed for existing conditions and future climate data. The measured and predicted indoor microclimate data from 'present' till 2080s are used to determine possible chemical degredation risk on library collection and human comfort. Comparison of periodic results of future climate data indicates an increase in temperature that could cause both an increase in chemical degredation risk on the library collection and a decline in thermal comfort conditions. Mitigation of climate change effects on library collection and human comfort requires taking some actions such as adding light and adaptive mechanical solutions.Conference Object Projectile Impact Testing Aluminum Corrugated Core Composite Sandwiches Using Aluminum Corrugated Projectiles: Experimental and Numerical Investigation(Trans Tech Publications, 2017) Odacı, İsmet Kutlay; Kılıçaslan, Cenk; Taşdemirci, Alper; Mamalis, Athanasios G.; Güden, MustafaE-glass/polyester composite plates and 1050 H14 aluminum trapezoidal corrugated core composite sandwich plates were projectile impact tested using 1050 H14 aluminum trapezoidal fin corrugated projectiles with and without face sheets. The projectile impact tests were simulated in LS-DYNA. The MAT_162 material model parameters of the composite were determined and then optimized by the quasi-static and high strain rate tests. Non-centered projectile impact test models were validated by the experimental and numerical back face displacements of the impacted plates. Then, the centered projectile impact test models were developed and the resultant plate displacements were compared with those of the TNT mass equal Conwep simulations. The projectiles with face sheets induced similar displacement with the Conwep blast simulation, while the projectiles without face sheets underestimated the Conwep displacements, which was attributed to more uniform pressure distribution with the use of the face sheets on the test plates. © 2018 Trans Tech Publications, Switzerland.Conference Object Computational Determination of Volume Averaged Transport Properties of Heat and Fluid Flow in Porous Media by Using Microtomography Images(Begell House, 2017) Çelik, Hasan; Mobedi, Moghtada; Nakayama, Akira; Özkol, ÜnverIn this study, the theory and techniques for obtaining VAM (Volume Average Theory) transport properties of a porous medium from micro-tomography images are described. The validation of the results with reported experimental or numerical values in literature may not be sufficient, hence a comprehensive attention is paid to the techniques that can be used for verification of the obtained numerical results at each step of this long computational process. The suggested verification techniques are categorized and explained in details. © 2017, Begell House Inc. All Rights Reserved.