Browsing by Publisher "American Society of Mechanical Engineers (ASME)"
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Item Dynamics of axially accelerating beams with an intermediate support(American Society of Mechanical Engineers (ASME), 2011) Bagdatli S.M.; Özkaya E.; Öz H.R.The transverse vibrations of an axially accelerating EulerBernoulli beam resting on simple supports are investigated. The supports are at the ends, and there is a support in between. The axial velocity is a sinusoidal function of time varying about a constant mean speed. Since the supports are immovable, the beam neutral axis is stretched during the motion, and hence, nonlinear terms are introduced to the equations of motion. Approximate analytical solutions are obtained using the method of multiple scales. Natural frequencies are obtained for different locations of the support other than end supports. The effect of nonlinear terms on natural frequency is calculated for different parameters. Principal parametric resonance occurs when the velocity fluctuation frequency is equal to approximately twice of natural frequency. By performing stability analysis of solutions, approximate stable and unstable regions were identified. Effects of axial velocity and location of intermediate support on the stability regions have been investigated. Copyright © 2011 by ASME.Item Magnetohydrodynamics mixed convection in a lid-driven cavity having a corrugated bottom wall and filled with a non-newtonian power-law fluid under the influence of an inclined magnetic field(American Society of Mechanical Engineers (ASME), 2016) Selimefendigil F.; Chamkha A.J.In this study, the problem of magnetohydrodynamics (MHD) mixed convection of lid-driven cavity with a triangular-wave shaped corrugated bottom wall filled with a non- Newtonian power-law fluid is numerically studied. The bottom corrugated wall of the cavity is heated and the top moving wall is kept at a constant lower temperature while the vertical walls of the enclosure are considered to be adiabatic. The governing equations are solved by the Galerkin weighted residual finite element formulation. The influence of the Richardson number (between 0.01 and 100), Hartmann number (between 0 and 50), inclination angle of the magnetic field (between 0 deg and 90 deg), and the power-law index (between 0.6 and 1.4) on the fluid flow and heat transfer characteristics are numerically investigated. It is observed that the effects of free convection are more pronounced for a shear-thinning fluid and the buoyancy force is weaker for the dilatant fluid flow compared to that of the Newtonian fluid. The averaged heat transfer decreases with increasing values of the Richardson number and enhancement is more effective for a shearthickening fluid. At the highest value of the Hartmann number, the averaged heat transfer is the lowest for a pseudoplastic fluid. As the inclination angle of the magnetic field increases, the averaged Nusselt number generally enhances. © 2016 by ASME.Item Numerical Study of Natural Convection in a Ferrofluid-Filled Corrugated Cavity with Internal Heat Generation(American Society of Mechanical Engineers (ASME), 2016) Selimefendigil F.; Oztop H.F.In this paper, numerical simulations for the natural convection in a ferrofluid-filled corrugated cavity with internal heat generation under the influence of a magnetic dipole source were performed. The cavity is heated from below and cooled from above while vertical side walls are assumed to be adiabatic. A magnetic dipole source was located under the bottom heated wall. The governing equations were solved by Galerkin weighted residual finite-element formulation. The influence of external Rayleigh number (between 104 and 5 × 105), internal Rayleigh number (between 104 and 5 × 106), magnetic dipole strength (between 0 and 4), horizontal (between 0.2 and 0.8) and vertical (between-5 and-2) locations of the magnetic dipole source on fluid flow, and heat transfer are numerically investigated. It was observed that depending on heating mechanism (the external or internal heating), the presence of corrugation of the bottom wall either enhances or deteriorates the absolute value of the averaged heat transfer. The strength and locations of the magnetic dipole source affect the distribution of the flow and thermal patterns within the cavity for both flat and corrugated wall cavity. The net effect of the complicated interaction of the internal heating, external heating, and ferroconvection of magnetic source results in heat transfer enhancement with increasing values of magnetic dipole strength. Wall corrugation causes more enhancement of averaged heat transfer and this is more pronounced for low values of vertical location of magnetic source. © 2016 by ASME.Item Simultaneous Determination of Disassembly Sequence and Disassembly-to-Order Decisions Using Simulation Optimization(American Society of Mechanical Engineers (ASME), 2016) Ilgin M.A.; Taşoǧlu G.T.Strict environmental regulations and increasing public awareness toward environmental issues force many companies to establish dedicated facilities for product recovery. All product recovery options require some level of disassembly. That is why, the cost-effective management of product recovery operations highly depends on the effective planning of disassembly operations. There are two crucial issues common to most disassembly systems. The first issue is disassembly sequencing which involves the determination of an optimal or near optimal disassembly sequence. The second issue is disassembly-to-order (DTO) problem which involves the determination of the number of end of life (EOL) products to process to fulfill the demand for specified numbers of components and materials. Although disassembly sequencing decisions directly affects the various costs associated with a disassembly-to-order problem, these two issues are treated separately in the literature. In this study, a genetic algorithm (GA) based simulation optimization approach was proposed for the simultaneous determination of disassembly sequence and disassembly-to-order decisions. The applicability of the proposed approach was illustrated by providing a numerical example and the best values of GA parameters were identified by carrying out a Taguchi experimental design. © Copyright 2016 by ASME.Item Effects of nanoparticle shape on slot-jet impingement cooling of a corrugated surface with nanofluids(American Society of Mechanical Engineers (ASME), 2017) Selimefendigil F.; Öztop H.F.Numerical study of jet impingement cooling of a corrugated surface with water-SiO2 nanofluid of different nanoparticle shapes was performed. The bottom wall is corrugated and kept at constant surface temperature, while the jet emerges from a rectangular slot with cold uniform temperature. The finite volume method is utilized to solve the governing equations. The effects of Reynolds number (between 100 and 500), corrugation amplitude (between 0 and 0.3), corrugation frequency (between 0 and 20), nanoparticle volume fraction (between 0 and 0.04), and nanoparticle shapes (spherical, blade, brick, and cylindrical) on the fluid flow and heat transfer characteristics were studied. Stagnation point and average Nusselt number enhance with Reynolds number and solid particle volume fraction for both flat and corrugated surface configurations. An optimal value for the corrugation amplitude and frequency was found to maximize the average heat transfer at the highest value of Reynolds number. Among various nanoparticle shapes, cylindrical ones perform the best heat transfer characteristics in terms of stagnation and average Nusselt number values. At the highest solid volume concentration of the nanoparticles, heat transfer values are higher for a corrugated surface when compared to a flat surface case. © 2017 by ASME.Item Optimal Perturbation Iteration Method for Solving Nonlinear Heat Transfer Equations(American Society of Mechanical Engineers (ASME), 2017) Deniz S.In this paper, the new optimal perturbation iteration method (OPIM) is introduced and applied for solving nonlinear differential equations arising in heat transfer. The effectiveness of the proposed method will be tested by considering two specific applications: the temperature distribution equation in a thick rectangular fin radiation to free space and cooling of a lumped system with variable specific heat. Comparing different methods shows that the results obtained by optimal perturbation iteration method are very good agreement with the numerical solutions and perform better than the most existing analytic methods. Copyright © 2017 by ASME.Item Laminar convective nanofluid flow over a backward-facing step with an elastic bottom wall(American Society of Mechanical Engineers (ASME), 2018) Selimefendigil F.; Öztop H.F.In the present study, laminar forced convective nanofluid flow over a backward-facing step was numerically investigated. The bottom wall downstream of the step was flexible, and finite element method was used to solve the governing equations. The numerical simulation was performed for a range of Reynolds number (between 25 and 250), elastic modulus of the flexible wall (between 104 and 106), and solid particle volume fraction (between 0 and 0.035). It was observed that the flexibility of the bottom wall results in the variation of the fluid flow and heat transfer characteristics for the backward-facing step problem. As the value of Reynolds number and solid particle volume fraction enhances, local and average heat transfer rates increase. At the highest value of Reynolds number, heat transfer rate is higher for the case with the wall having lowest value of elastic modulus whereas the situation is reversed for other value of Reynolds number. Average Nusselt number reduces by about 9.21% and increases by about 6.1% for the flexible wall with the lowest elastic modulus as compared to a rigid bottom wall for Reynolds number of 25 and 250. Adding nano-additives to the base fluid results in higher heat transfer enhancements. Average heat transfer rates enhance by about 35.72% and 35.32% at the highest solid particle volume fraction as compared to nanofluid with solid volume fraction of 0.01 for the case with wall at the lowest and highest elastic modulus. A polynomial type correlation for the average Nusselt number along the flexible hot wall was proposed, which is dependent on the elastic modulus and solid particle volume fraction. The results of this study are useful for many thermal engineering problems where flow separation and reattachment coupled with heat transfer occur. Control of convective heat transfer for such configurations with wall flexibility and nanoparticle inclusion to the base fluid was aimed in this study to find the effects of various pertinent parameters for heat transfer enhancement. © 2018 by ASME.Item Cooling of a partially elastic isothermal surface by nanofluids jet impingement(American Society of Mechanical Engineers (ASME), 2018) Selimefendigil F.; Öztop H.F.Numerical study of nanofluid jet impingement cooling of a partially elastic isothermal hot surface was conducted with finite element method. The impingement surface was made partially elastic, and the effects of Reynolds number (between 25 and 200), solid particle volume fraction (between 0.01 and 0.04), elastic modulus of isothermal hot surface (between 104 and 106), size of the flexible part (between 7.5 w and 25 w), and nanoparticle type (spherical, cylindrical, blade) on the fluid flow and heat transfer characteristics were analyzed. It was observed that average Nusselt number enhances for higher Reynolds number, higher values of elastic modulus of flexible wall, smaller size of elastic part, and higher nanoparticle solid volume fraction and for cylindrical shaped particles. It is possible to change the maximum Nusselt number by 50.58% and 33% by changing the elastic modulus of the hot wall and size of elastic part whereas average Nusselt number changes by only 9.33% and 6.21%. The discrepancy between various particle shapes is higher for higher particle volume fraction. © Copyright 2018 by ASME.Item A DEMATEL-Based Disassembly Line Balancing Heuristic(American Society of Mechanical Engineers (ASME), 2019) Ilgin M.A.Circular economy has emerged as a response to increasing environmental problems. As opposed to linear economy, circular economy aims at the preservation of energy, material, and labor contents of used products. A critical process in circular economy is product recovery which involves the recovery of materials or components from returned products through various recovery options including recycling, refurbishing, and remanufacturing. All recovery options require some level of disassembly and disassembly operations that are generally carried out in a disassembly line. Like assembly lines, disassembly lines must be balanced in order to ensure the effective operation of the line. Mathematical programming techniques, metaheuristics, and various heuristic procedures were employed in order to solve different types of disassembly line balancing problem (DLBP). However, the use of multi-attribute decision making techniques is limited to few studies. In this study, we propose a DEMATEL-based disassembly line balancing approach which does not require extensive knowledge in operations research and computer programming. A solution can be obtained by carrying out basic matrix operations and following the steps of the approach. Two numerical examples are also provided in order to present the applicability of the proposed approach. The results indicate that the proposed approach presents a satisfactory performance compared to the previously proposed approaches. Copyright © 2019 by ASME.Item Cold metal transfer welding of AA6061 to AA7075: Mechanical properties and corrosion(American Society of Mechanical Engineers (ASME), 2019) Çömez N.; Durmus H.Cold metal transfer (CMT) welding provides many advantages for welding of dissimilar materials and thin sheets with its superior heat input control mechanism. In this study, AA6061 and AA7075 aluminum alloys were joined with CMT welding. The effect of welding parameters on hardness, tensile strength, and corrosion rate was investigated. The Tafel extrapolation method was carried out to determine the corrosion rates of AA6061 and AA7075 base metals and AA6061–AA7075 joints. Increasing heat input was found to be detrimental for both mechanical properties and corrosion resistance. The outcomes showed that CMT welding produces adequate joints of AA6061–AA7075 in terms of mechanical properties and corrosion resistance, favorably with welding parameters that provide low heat input. © 2019 by ASME.Item Comparison of artificial neural network and fuzzy logic approaches for the prediction of in-cylinder pressure in a spark ignition engine(American Society of Mechanical Engineers (ASME), 2020) Solmaz O.; Gurbuz H.; Karacor M.In first stage, a machine learning (ML) was performed to predict in-cylinder pressure using both fuzzy logic (FL) and artificial neural networks (ANN) depending on the results of experimental studies in a spark ignition (SI) engine. In the ML phase, the experimental in-cylinder pressure data of SI engine was used. SI engine was operated at stoichiometric air-fuel mixture (u ¼ 1.0) at 1200, 1400, and 1600 rpm engine speeds. Six different ignition timings, ranging from 15 to 45 CA, were used for each engine speed. Correlations (R2) between data from in-cylinder pressure obtained via FL and ANN models and data form experimental in-cylinder pressure were determined. R2 values over 0.995 were obtained at an ML stage of ANN model for all test conditions of the engine. However, R2 values were remained between range of 0.820-0.949 with the FL model for different engine speeds and ignition timings. In the second stage, in-cylinder pressure prediction was performed by using an ANN model for engine operating conditions where no experimental results were obtained. Furthermore, indicated mean effective pressure (IMEP) values were calculated by predicting in-cylinder pressure data for different engine operation conditions, and then compared with experimental IMEP values. The results show that the in-cylinder pressure and IMEP results estimated with the trained ANN model are fairly close to the experimental results. Moreover, it was found that using the trained ANN model, the ignition timing corresponding to the maximum brake torque (MBT) used in the engine management systems and engine studies could be determined with high accuracy. Copyright © 2020 by ASMEItem Forced convection laminar pulsating flow in a 90-deg bifurcation(American Society of Mechanical Engineers (ASME), 2021) Selimefendigil F.; Oztop H.F.; Khodadadi J.M.Numerical investigation of laminar forced convection of pulsating flow in a 90-deg bifurcation was performed with the finite volume method. The inlet velocity varies sinusoidally with time while constant wall temperature is utilized. The working fluid is air with constant properties and the numerical work is conducted for a range of the Reynolds numbers (100–2000), dividing flowrates (0.3–0.7) and Strouhal numbers (0.1–10). It is observed that the amplitudes of oscillating heat transfer are damped as the value of the Strouhal number increases. The average value of Nu number rises for higher Reynolds number and the dividing flowrate for the downstream wall of the y-channel branch. As the value of the dividing flowrate increases from 0.3 to 0.7, heat transfer is less effective in the vicinity of the branch at the Reynolds number of 500. The effects of the Reynolds number on the average Nu number variation is more pronounced for the y-branch wall for different values of dividing flowrates. Resonant type behavior of average Nu number is obtained for the y-branch channel for diving flowrates of 0.3 and 0.5. Copyright © 2020 by ASMEItem Nanoliquid Jet Impingement Heat Transfer for a Phase Change Material Embedded Radial Heating System(American Society of Mechanical Engineers (ASME), 2022) Selimefendigil F.; Öztop H.F.Nanoliquid impingement heat transfer with a phase change material (PCM) installed radial system is considered. The study is performed by using the finite element method for various values of Reynolds numbers (100 ≤ Re ≤ 300), height of PCM (0.25H ≤ hpcm ≤ 0.75H), and plate spacing (0.15H ≤ hs ≤ 0.40H). Different configurations using water, nanoliquid, and nanoliquid + PCM are compared in terms of heat transfer improvement. Thermal performance is improved by using PCM, while best performance is achieved with nanoliquid and PCM-installed configuration. At Re = 100 and Re = 300, heat transfer improvements of 26% and 25.5% are achieved with the nanoliquid + PCM system as compared to water without PCM. The height of the PCM layer also influences the heat transfer dynamic behavior, while there is 12.6% variation in the spatial average heat transfer of the target surface with the lowest and highest PCM heights while discharging time increases by about 76.5%. As the spacing between the plates decreases, average heat transfer rises and there is 38% variation. © 2021 by ASME.Item Tribological Characteristics of Tantalum-Oxide Coating Fabricated on Pre-Treated 2024 Aluminum Alloys(American Society of Mechanical Engineers (ASME), 2023) Albayrak S.; Gul C.; Ci̧nici H.; Şahin Ö.Aluminum has many advantages, such as being lightweight, but it may not provide sufficient wear resistance for some applications. Tantalum oxide is a ceramic-based coating layer that can improve wear resistance. In this study, 2024 aluminum alloy samples with different surface treatments were coated with amorphous Ta2O5 using the RF spraying method under the same conditions. Polishing, 10% HCl solution, 5% NaOH solution, and 50% HNO3 solution, as well as sandblasting, were applied to the surfaces of aluminum alloys separately, and the sample groups were coated. The effects of pre-coating surface treatments on coating morphology and wear resistance were investigated. The surface morphologies of the coatings were examined using scanning electron microscopy, electron dispersion spectroscopy, and X-ray diffraction. Wear tests were then conducted to determine the mechanical properties, and after the tests, scanning electron microscopy examinations and volume loss calculations were performed using a profilometer. The wear test results were discussed and compared. The investigation yielded continuous, homogeneous, and crack-free coatings on the 2024 aluminum alloy surfaces. However, the wear resistance of these coatings was compromised by acid etching. Following polishing and sandblasting, the coated surfaces experienced a decrease in volume losses from abrasion by 4.3% and 44.8%, respectively, compared to the uncoated samples. Copyright © 2023 by ASME.Item Cooling Performance Improvement for Two Hot Elastic Plates by Using Double Channels With Rotating Cylinders(American Society of Mechanical Engineers (ASME), 2024) Selimefendigil F.; Öztop H.F.Alternative cooling systems that can be used for thermal management in different technological applications such as in batteries, solar panels, electronic systems, and in diverse heat transfer equipments are needed. This study uses a hybrid channel system with rotating circular cylinders to explore the cooling of two heated elastic plates. The numerical analysis of a coupled fluid–structure–thermal system with rotating cylinders is done using the finite element technique with arbitrary Lagrangian–Eulerian (ALE). The study is carried out for different values of the Reynolds number (Re) in the upper channel flow (between 200 and 1000), the nondimensional rotational speeds of the cylinders (Ω in the range between −1000 and 1000), and the nondimensional location of the cylinders (between 0.4 and 1) taking into account the cooling of both the rigid and elastic plates. Rigid plates have better cooling performance than elastic ones. The cooling performance increases for both rigid and elastic plates, up to 26.1% and 31.7%, respectively, at the maximum upper channel flow Re. For elastic and rigid plates, counter-clockwise (CCW) rotation at maximum speed increases cooling performance by 18.5% and 19%, respectively, but clockwise (CW) rotation increments cooling performance by only 7%. The rigid plate’s cooling performance increases by 23.6% when rotation is activated at its maximum speed as opposed to a cooling system without cylinders. Thermal performance varies between 26% and 29% when the cylinder is positioned horizontally differently. By using optimization, the cooling performance increase with rotating cylinders at Re = 200, which is determined to be 73.6% more than that of the case without cylinders. Optimization results in an extra 11.2% increase in cooling performance at Re = 1000 when compared to the parametric computational fluid dynamics (CFD) scenario. © 2024 by ASME.