Person: BAŞOL, Altuğ Melik
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Altuğ Melik
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BAŞOL
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ArticlePublication Metadata only On the individual droplet growth modeling and heat transfer analysis in dropwise condensation(IEEE, 2021-10) Azarifar, Mohammad; Budaklı, M.; Başol, Altuğ Melik; Arık, Mehmet; Mechanical Engineering; BAŞOL, Altuğ Melik; ARIK, Mehmet; Azarifar, MohammadThe low convective coefficient at condenser part of spreaders and vapor chambers due to film blanket blocking encourages utilizing dropwise condensation (DWC). Challenges exist in the experimental characterization of DWC, which includes dependency on numerous parameters and more importantly measurement difficulties due to low driving temperature differences. This highlights the necessity of accurate modeling of this complex process. The widely used macroscale modeling process of DWC, known as classical analytical modeling of DWC, typically combines state of the art droplet size distribution model with a simplified shape-factor based heat transfer analysis of a single droplet which contains major simplifications such as conduction-only through the bulk liquid, hemispheric droplet shape, and homogeneously distributed temperature over the entire droplet surface. Recent numerical approaches included effect of Marangoni convection and implanted realistic thermal boundary conditions on liquid-vapor interface and reported significant errors of classical modeling. Based on a novel dynamic numerical approach which incorporates surface tension, Marangoni convection, and active mass transfer at the liquid-vapor interface, droplet growth phenomenon has been modeled in this study. Notable differences of droplet growth and flow field have been observed resulted from dynamic growth modeling of the droplet as more than 70% heat transfer rate underestimation of quasi steady modeling in 1 mm droplets with contact angle of 150° is observed. Effect of shape change due to gravity on the heat and mass transfer analysis of individual droplets found to be negligible.ArticlePublication Open Access Numerical analysis and diffuser vane shape optimization of a radial compressor with the open-source software su2(Turk Isi Bilimi ve Teknigi Dernegi, 2023) Uzuner, Mustafa Kürşat; Başol, Altuğ Melik; Mischo, B.; Jenny, P.; Mechanical Engineering; BAŞOL, Altuğ Melik; Uzuner, Mustafa KürşatIn recent years, the usage of open-source computational fluid dynamics tools is on a rise both in industry and academia. SU2 is one of these open-source tools. Unlike other open-source alternatives, SU2 is equipped with boundary condition types, solvers and methods that are especially developed for the analysis and design of turbomachinery. The aim of this work is to explore and investigate the capabilities of SU2 in the prediction of performance parameters of radial compressors. Two different single stage shrouded compressor geometries, one with a vaneless diffuser and the other with a vaned diffuser have been investigated with steady state CFD. The compressors were designed by MAN Energy Solutions Schweiz AG. Computational results with SU2 showed a satisfactory agreement with both the experimental data and reference CFD solutions obtained with Fidelity Flow, which is formerly known as Numeca Fine TURBO. Only at the relatively higher mass flow rates the difference between references and SU2 were higher compared to other operating points. After performance parameters were successfully calculated with SU2, the optimization tools that come with SU2 were also used. A 2D adjoint optimization study on the vane of the vaned diffuser was carried out. The study was carried out at a single operating point that is close to choke conditions. The loss generated by the large separated flow region at the suction side of the diffuser vane was reduced by 0.55 % in the optimized geometry using minimal modifications on the existing vane geometry to keep the performance of the compressor intact at other operating points. However, the resulting modification increased the total pressure loss by 0.86 % at one of the design operating points. This performance penalty could be due to the discontinuity in the vane geometry generated by the optimizer. Overall, the study shows that SU2 has the basic numerical schemes and models that are required for the analysis of radial turbomachinery flows and geometry optimization.ArticlePublication Metadata only An Eulerian multiphase frost model based on heat transfer measurements(Elsevier, 2023-12-01) Saygın, Alper; Başol, Altuğ Melik; Arık, Mehmet; Mechanical Engineering; BAŞOL, Altuğ Melik; ARIK, Mehmet; Saygın, AlperIn this paper, a laminar numerical model is developed to predict frost formation over a horizontal cold flat surface. An Eulerian-Eulerian multiphase approach is followed to model humid air and ice phases separately. Frost accumulation on the cold surface is modeled with an empirical mass source term. Model constants were tuned in a systematic way using experimental heat flux and frost thickness data. A velocity dependent model constant is introduced into the mass source term. The heat flux rise observed experimentally at the initial stages of the frosting could be captured with the use of the velocity dependent model constant and the addition of this term considerably improved the accuracy of the frost model at the initial stages of frosting. It was also observed that the selected particle diameter for the solid ice phase has a considerable effect on the velocity profile over the frost layer. This requires tuning of the velocity dependent model constant parameters according to the selected ice particle diameter. The developed numerical model was tested with three different frost thermal conductivity models. Using the thermal conductivity of solid ice for the frost thermal conductivity resulted in the most accurate prediction at the early stages of the frost growth process indicating a rather column-wise vertical growth of ice crystals with very low lateral branching. However, the overprediction of the numerical heat flux with the thermal conductivity of solid ice points out a decrease in the thermal conductivity of the newly added frost layers indicating a more pronounced lateral branching of ice crystals within the frost layer. The effect of the diffusion coefficient of the water vapor in humid air on frosting is also investigated. An artificial increase in the diffusion coefficient improved the accuracy of the heat flux prediction of the model at the initial stages of frosting which might indicate an eddy-driven enhanced mixing in the boundary layer which might not be captured in the laminar flow model. Finally, the developed numerical model is also tested on another scenario with the surface temperature held at -30 °C. Detailed analysis of the numerical simulations showed a more porous frost layer with the surface temperature at -30 °C as compared to the frost porosity formed on the surface at -20 °C.ArticlePublication Open Access Üniversite dış mekânları i̇çin zaman-mekânsal haritalama yöntemine dayanan bir kullanım sonrası değerlendirme modeli(Yildiz Technical University Faculty Of Architecture, 2020) Göçer, Ö.; Göçer, K.; Başol, Altuğ Melik; Kıraç, Mustafa Furkan; Torun, A. O.; Bakovic, M.; Siddiqui, F. P.; Özcan, Barış; Computer Science; Mechanical Engineering; BAŞOL, Altuğ Melik; KIRAÇ, Mustafa Furkan; Özcan, BarışÜniversite yerleşkeleri yalnızca çeşitli sosyal ve eğitsel binalardan oluşmakla kalmaz, dış mekânları ve donatıları, rekreasyon ve peyzaj alanları ile bütünleşik bir kurgu oluştururlar. Dış mekânlar, yerleşke kullanıcılarının toplumsal etkileşim, dinlenme ve rahatlama, rekreasyon, fikir alışverişinde bulunma ve güçlü bir mülkiyet ve aidiyet hissi oluşturma potansiyeli taşırlar. İnsanların birbirleriyle iletişim kurmalarını ve sosyalleşmelerini sağlayarak sosyal yaşam için ortak bir kimlik oluşturmak dış mekânların en önemli işlevidir. Ne var ki dış mekânlar ne kadar akılcı tasarlansa da, uygulamada beklenenin dışında bir kullanımla karşılaşılabilmektedir. Beklentiler ile uygulanan arasındaki farkın belirlenebilmesi için dış mekânlar ile bina grupları arasındaki ilişki, yeterlilik, kullanım süresi, erişilebilirlik ve fiziksel çevrenin etkileşimi bütünsel bir yaklaşımla incelenmelidir. Dış mekânlarda insan kullanımının ve tasarım niyetinin başarılı olup olmadığını değerlendirmenin en iyi yöntemlerinden biri olarak kullanım sonrası değerlendirme (KSD) önerilmektedir. Ne yazık ki, iç mekânların değerlendirilmesine ilişkin KSD yöntemleri hakkında çalışmalar her geçen gün artsa da, dış mekânların değerlendirilmesine yönelik özellikle üniversite yerleşkelerinde uygulanabilecek kapsamlı bir KSD çalışmasına rastlanmamaktadır. Bu çalışmada dış mekân kullanımını etkileyen değişkenleri ve bu değişkenler arasındaki etkileşimi bütüncül olarak ele alan bir KSD yöntemi tanıtılmıştır. Önerilen yöntem kent dışı bir üniversite yerleşkesinde uygulanmış ve uygulama sonuçları dış mekân kullanım değeri bakımından değerlendirilmiştir.ArticlePublication Metadata only A preconditioned multigrid for simulation of atmospheric flow and wind turbine wakes(Elsevier, 2015-11-20) Jafari, S.; Başol, Altuğ Melik; Chokani, N.; Abhari, R. S.; Mechanical Engineering; BAŞOL, Altuğ MelikThis paper demonstrates a low Mach number preconditioning formulation for high Reynolds number, low Mach number atmospheric flows. The preconditioning is implemented together with multigrid approach into a multistage solver in order to provide an efficient and robust all purpose solver to be used for the simulation of high Reynolds number viscous flows. Several modification and scaling of the preconditioned parameter are introduced to ensure robust use of the scheme for this particular flow regime in presence of stagnation points and seperation regions. The simulations results of standard cases of atmospheric flow over hilly terrain with attached and separated flow are presented to demonstrate the superior convergence, accuracy and robustness of the developed preconditioned scheme. An immersed wind turbine model is also developed and embedded into the preconditioned solver which allows for the simulations of far wake behind wind turbines in wind farms. The use of the immersed model reduces the stringent grid requirements of full RANS simulations around wind turbines and allows one to efficiently predict the wake evolution within wind farms.ArticlePublication Metadata only Numerical analysis of the radiant heating effectiveness of a continuous glass annealing furnace(Elsevier, 2022-03-05) Altun, Gönenç Can; Başol, Altuğ Melik; Mechanical Engineering; BAŞOL, Altuğ Melik; Altun, Gönenç CanRadiative heat transfer is the dominant mode of heat transfer in glass annealing furnaces. Especially in electrically heated furnaces due to the nonparticipating nature of the furnace atmosphere the radiative heat transfer predominantly occurs between surfaces. In this regard, in container glass manufacturing the layout of the container glasses inside the furnace can considerably affect the radiative heating effectiveness of the furnace. In this numerical study, the effect of the spacing between the bottle rows on the radiant heating effectiveness of the furnace was numerically investigated. An industrial scale continuous annealing furnace model was used and the combined conduction – radiation heat transfer modes in the furnace were solved with the in-house developed transient solver. The convective heat transfer inside the furnace was not taken into account due to its relatively lower contribution in heat transfer. The computational cost of the numerical model is reduced with the use of a computational domain consisting of 7 bottle rows instead of full 29 bottle rows. Reverse Monte Carlo Ray Tracing method is used to solve for the surface-to-surface radiative heat transfer inside the radiant heating zone and integrated into GPU to reduce its computational cost. Further computational speed-up was achieved with the use of a 2nd order accurate radiation boundary condition implementation. It allows a time step increase of 2.5x in comparison with the first order accurate implementation for the same level of accuracy. Finally, a parametric study on the effect of the spacing between the bottle rows on the radiative heating of the bottles have been conducted. In this regard, the spacing between the bottle rows and the conveyor speed have been altered in a way that the throughput of the furnace, the number bottles processed per unit time, is kept constant. The study shows that there is an optimum spacing value between the bottle rows. For the particular bottle geometry considered in this study, the optimum row spacing value is found to be 35% of the bottle diameter. Running the furnace at this optimum value, the length of the heating zone could be reduced by 8.5% compared to the case when the furnace was operated with the bottles almost in touch with each other.Conference ObjectPublication Metadata only An experimental investigation into frost accumulation over vertical finned and unfinned surfaces during impinging air flow(ASME, 2020) Öksüz, Enes Abdülhakim; Saygın, Alper; Başol, Altuğ Melik; Budaklı, M.; Arık, Mehmet; Mechanical Engineering; BAŞOL, Altuğ Melik; ARIK, Mehmet; Öksüz, Enes Abdülhakim; Saygın, AlperFrost formation on evaporators negatively affects the cooling performance of refrigerators. It increases the thermal resistance between the refrigerant and air leading to a reduction in the system cooling capacity. In this study, the effect of frost accumulation over a bare and finned surface on the convective thermal resistances has been experimentally investigated under impinging flow conditions. The surfaces are vertically positioned in a horizontal wind tunnel. The convective resistances have been measured with an in-house developed heat flux measurement system. Finally, the effectiveness of the finned surface was derived from the measurements for dry, condensing flow and as well as for frosting conditions. Under frosting conditions, the effectiveness of the finned surface is measured as 1.4 that is by a factor of 2X lower compared to the effectiveness of the same finned surface operating under dry conditions. It has been observed that the frost accumulation initially takes place at the tip of the fins and leads to a 45% drop in the heat transfer rate when the fin tips are completely covered with frost. Further frost accumulation on the fin base does not result in an additional drop in the heat transfer rate. In this regard, the study emphasizes the importance of the fin tip design for the heat sinks operating under frosting conditions.Conference ObjectPublication Metadata only A numerical investigation into frost formation under impinging flow conditions(IEEE, 2021) Saygın, Alper; Öksüz, Enes Abdülhakim; Başol, Altuğ Melik; Arık, Mehmet; Mechanical Engineering; BAŞOL, Altuğ Melik; ARIK, Mehmet; Saygın, Alper; Öksüz, Enes AbdülhakimFrost formation is an undesired phenomenon for a wide range of practical applications as it diminishes amount of heat dissipation from heat transfer regions. In this paper, frost growth process on a vertically suspended plate is numerically investigated. Modeling of a frost structure is a multifaceted task since contribution of mass and heat transfer effects must be considered simultaneously. An Eularian-Eularian multiphase-multicomponent model is used and source terms are added to conservation equations in order to generate frosting phase change process. The model implemented herein is able to predict frost deposition on a surface under impinging flow conditions. Computational domain is formed of two separate phases which are humid air and frost phases. Humid air phase is also consisted of dry air and water vapor, latter is transformed into frost layer by means of introduced source terms. Experimental results were used to validate the numerical approach. Results showed a good agreement with the frost thickness growth observed during the experiments. Predicted temperature and density variations inside the porous frost layer were discussed. Frost thickness increased rapidly at the beginning of the experiments; later rate of increase is decreased. Denser frost layers obtained adjacent to the frosting surface. Temperature within the frost layer is dropped during the growth process.Conference ObjectPublication Metadata only A Monte Carlo random walk-based methodology for calculation of sensitivity coefficients in inverse radiant boundary design problem(Begell House Inc., 2023) Yıldız, Ersin; Başol, Altuğ Melik; Mengüç, Mustafa Pınar; Mechanical Engineering; BAŞOL, Altuğ Melik; MENGÜÇ, Mustafa Pınar; Yıldız, ErsinThis study presents a methodology for the solution of inverse boundary design problems involving transient heat conduction in solid objects imposed by radiant boundary condition. The inverse solution aims to find the required time-varying radiant wall temperature that provides the desired temperature histories at several selected design points inside the solid objects. Gradient-based optimization approach is employed, and a novel methodology is developed for the calculation of the sensitivity coefficients. The sensitivity coefficients are compared with the reference solution obtained from finite difference approximation. First, the inverse boundary design methodology was tested on two scenarios with known radiant wall temperature profiles. Using the true solutions of the problems, the validity of the developed methodology was verified. Next, the methodology was tested on a case where a constant cooling rate at a single design point was set as objective function. Results show that the methodology can successfully determine the required radiant wall temperature profile that fulfills the desired cooling rate.Conference ObjectPublication Metadata only Investigation of soot formation of ethylene/air jet diffusion flame with rank correlated slw including ethylene and acetylene radiation(Begell House Inc., 2023) Halvaşi, Berkay; Başol, Altuğ Melik; Mengüç, Mustafa Pınar; Ertunç, Özgür; Mechanical Engineering; BAŞOL, Altuğ Melik; MENGÜÇ, Mustafa Pınar; ERTUNÇ, Özgür; Halvaşi, BerkayRadiation is significant, especially in sooting flames. The interaction between radiation and soot considerably affects the combustion regime. Spectral radiation models that account for the radiative effects of sooting flames are critical. This study numerically investigates the interaction between the radiation and soot formation on a sooting jet diffusion flame. A rank correlated spectral line-based weighted sum of gray gases (RC-SLW) global model is implemented in Ansys Fluent and used for the combustion modeling of a jet diffusion flame. RC-SLW model, including ethylene and acetylene radiation, shows considerable improvement in predicting soot volume fraction compared to the domain-based with single gray gas weighted sum of gray gases (WSGG) model in Ansys Fluent. Increasing the number of gray gases in the RC-SLW model from 5 to 22 reduces the error in the maximum soot volume fraction from 30% to 1%. It was found that the effect of ethylene and acetylene radiation in the RC-SLW model has a minor effect on soot formation. Simulations without the effect of ethylene and acetylene radiation in the RC-SLW model underpredict maximum soot volume fraction by 5%.