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Öğe An acoustic structure design supported by shear thickening fluid for sound absorption(Elsevier Ltd, 2021) Aslan, Ramazan; Turan, OsmanIn this study, an acoustic structure consisting of cellular and perforated panel absorbers has been designed to noise control. Then, the sound absorption behaviour of designed acoustic structure has been investigated experimentally by reinforcing with STFs having different rheological properties. In addition, the sound absorption performance of the designed acoustic structure has been compared with the Gyroid which is a type of cellular sound absorber. The findings have indicated that the perforated panel activates significantly the sound absorption performance of the designed acoustic structure especially in the low (f[removed]3500Hz) frequency ranges. In addition, it has been also observed that this effect becomes stronger with STF reinforcement and significantly improves the sound absorption behaviour of the designed acoustic structure. Besides, it has been noticed that the sound absorption performance of the designed acoustic structure increases with increasing molecular weight of PEG for low frequencies (i.e. f[removed]3500Hz). Finally, it has been detected that the effectiveness of STF on the sound absorption performance of designed acoustics structure improves remarkably with increasing silica-nanoparticle ratio in the case of low and high frequencies (i.e. f[removed]3500Hz).Öğe ÇİFT FRENSEL LENSLİ BİR YOĞUNLAŞTIRILMIŞ FOTOVOLTAİK SİSTEMİN PERFORMANS ANALİZİ VE OPTİMİZASYONU(Kahramanmaras Sutcu Imam University, 2022) Kartal, Ferhat; Turan, OsmanBu çalışmada, yoğunlaştırıcı optik eleman olarak nokta odaklı Fresnel lens kullanılan çift optik elemanlı bir CPV sistemin performansı deneysel olarak incelenmiştir. Bu kapsamda, birincil ve ikincil optik eleman yoğunlaşma oranları (C_1, C_2), f sayıları (f_1, f_2) ve lensler arası mesafenin (L_D) CPV sistem performansı üzerindeki etkileri tek ve çift Fresnel lensli farklı konfigürasyonlar için araştırılmıştır. Genel olarak, lensler arası mesafe belirli bir kritik değere (L_(D,crit)) ulaşıncaya kadar, L_D artışı ile CPV sistem performansının iyileşmekte olduğu ancak L_D’nin kritik değerin üzerine çıktığında sistem performansının kötüleşmeye başladığı gözlenmiştir. Ayrıca, L_(D,crit)’in önemli ölçüde Fresnel lens çiftinin optik özelliklerine bağlı olduğu not edilmiştir. Bunun yanı sıra, yüksek f_1 değerine sahip çift Fresnel lensli CPV sistemlerinin, tekli Fresnel lens uygulamalarına göre daha iyi performans sergilediği görülmüştür. f_1>0.5 olduğunda CPV sisteminin performansının ikincil bir Fresnel lens kullanılarak iyileştirilebileceği tespit edilmiştir. Bunların ötesinde, Fresnel lens çiftlerinin optik özelliklerinin CPV sistem performansına etki oranını karşılaştırmak için deneysel veriler kullanılarak ANOVA analizleri yapılmıştır. ANOVA analizi sonuçları, birincil optik eleman özellikleri C_1 ve f_1’in çift Fresnel lensli CPV sistem performansı üzerinde ağırlıklı olarak etkili olduğunu işaret etmiştir. Öte yandan, diğer parametrelerle karşılaştırıldığında f_2'nin CPV sistem performansı üzerinde en az etkiye sahip olduğu da görülmüştür. Son olarak, genetik algoritma ve yapay sinir ağı temelli çalışmalar ile optimum C_1, C_2, f_1, f_2 and L_(D,crit) tahmin edilmiştir.Öğe Effects of wall heating on laminar mixed convection in a cylindrical enclosure with a rotating end wall(Elsevier France-Editions Scientifiques Medicales Elsevier, 2018) Turan, Osman; Yigit, Sahin; Chakraborty, NilanjanSteady-state laminar mixed convection in a cylindrical enclosure has been numerically analysed for different values of Reynolds, Richardson and Prandtl numbers given by 500 <= Re <= 3000, 0 <= Ri <= 1 and 10 <= Pr <= 500 respectively. The aspect ratio (i.e. height: radius = AR = H/R) of the cylindrical container is considered to be unity (ie. AR = H/R = 1). The bottom and top covers of the cylindrical enclosure are kept at different temperatures (T-C < T-H), while the cylindrical surface is taken to be adiabatic. The simulations for rotating top and bottom cover configurations yield the same numerical values of the mean Nusselt number (Nu) over bar when the thermal boundary conditions are kept unaltered. For this reason, only rotating top hot wall (ie. C1 configuration) and rotating top cold wall (ie. C2 configuration) have been considered for this analysis. The mean Nusselt number (Nu) over bar has been found to assume higher values in the C2 configuration than in the Cl configuration. Moreover, it has been found that the variation of the mean Nusselt number with Richardson number in the C2 configuration is qualitatively different from that in the C1 configuration. The simulation data has been used to propose a correlation for (Nu) over bar for the range of Re, Ri and Pr considered here for both Cl and C2 configurations. In addition to this, a regime diagram has been proposed for the C2 configuration in order to demarcate different flow regimes.Öğe Estimation of the Dominant Process Parameters on Coating Thickness in a Continuous Galvanizing Line With Computational Fluid Dynamics and Machine Learning Approaches(Wiley, 2025) Simsir, Cansu; Bilgin, Metin; Turan, OsmanIn this study, the dominant process parameters in the air-jet continuous galvanizing line on coating thickness were estimated by computational fluid dynamics and machine learning approaches. First, 128 different cases consisting of different levels of process parameters were created with the Taguchi method. Then, numerical analyses were performed for each case, calculating the maximum pressure gradient and maximum shear stress values on the strip, which were then used in the analytical model developed based on one-dimensional lubrication theory to obtain coating thickness values. Lastly, artificial intelligence techniques based on different machine learning algorithms such as K-Nearest Neighbors, linear regression, random forest and Adaboost, the relative effects of the process parameters influencing the coating thickness were compared through the feature importance values. It was observed that the dominant process parameters differ in low and high jet pressure cases. Accordingly, in the case of low jet pressure, air jet pressure, nozzle slot opening and velocity of the steel strip stand out as the dominant parameters, while in the case of high jet pressure, the most effective parameters influencing the coating thickness are air jet pressure and nozzle slot opening. In addition to this, the effect of the distance between the nozzle and the zinc pot influencing the coating thickness can also be neglected in both low and high pressure cases. Moreover, it was also noticed that the effects of nozzle angle and the distance between the nozzle and the steel strip influencing the coating thickness increase with increasing jet pressure.Öğe Free convection of power-law fluids in enclosures with partially heating from bottom and symmetrical cooling from sides(Pergamon-Elsevier Science Ltd, 2019) Yigit, Sahin; Battu, Madhusudhan; Turan, Osman; Chakraborty, NilanjanSteady-state laminar free convection of power-law fluids in a square enclosure with partial heating from below and symmetrical cooling from sides has been investigated based on numerical simulations. The partially heating is conducted by a centrally heated heat source on the bottom wall for different values of normalised heat source length IA (ranging from 0.2 to 0.8); power-law index n (from 0.6 to 1.8); nominal Rayleigh number (Ra) (from 10(3) to 10(6)) and nominal Prandtl number Pr (from 10 to 10(3)). An increase in the power-law index n leads to weakening of thermal advection owing to the augmentation of viscous resistance. This is reflected as an increment in the mean Nusselt number (Nu) over bar with decreasing value of n. Additionally, (Nu) over bar increases with an increase in Ra and IA for shear thinning (i.e. n < 1), Newtonian (i.e. n = 1) and shear thickening (i.e. n > 1) fluids. The observed influences of Ra, Pr, n and 1/L on (Nu) over bar have been explained by physical and scaling arguments and parameterized by a correlation for the mean Nusselt number. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Gypsum-based sound absorber produced by 3D printing technology(Elsevier Sci Ltd, 2020) Aslan, Ramazan; Turan, OsmanThe paper presents an alternative gypsum-based porous cellular sound absorber manufactured using 3D printing technology. The effects of cell structure and porosity on sound absorption coefficient have been experimentally investigated for the designed gypsum-based porous metamaterials. In addition to this, the numerical acoustic analyses were also performed to predict sound absorption behaviour of the produced gypsum-based porous metamaterials. Furthermore, the numerical flow analyses were also carried out to gain insight into the basic parameters such as flow resistance and tortuosity that affect the sound absorption behaviour of the designed gypsum-based porous metamaterials. As a result of the experimental and numerical studies, it has been observed that the gypsum specimens produced in porous structure provide a significant sound absorption in comparison to non-porous reference specimen. It has been also noticed that the open-cell gypsum specimens, in which the cells are interaction with each other, are much more efficient in terms of sound absorption than the open-cell structure in which there is no direct interaction between the cells. In addition to this, it was found that the gypsum specimens having Octet unit-cell structure have the highest sound absorption performance in the open cell structures. In other respects, it was also found that the sound absorption behaviour of each unit cell structure is getting worse with the increasing porosity. The numerical flow analyses have indicated that increase in porosity reduces the flow resistance and tortuosity levels of the open unit-cell structures and consequently worsens the sound absorption behaviour. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Just in time vessel arrival system for dry bulk carriers(Springer, 2023) Senss, Alexander; Canbulat, Onder; Uzun, Dogancan; Gunbeyaz, Sefer Anil; Turan, OsmanCargo conveyance onboard dry bulk carriers is contemporarily often affiliated to preoperational waiting times, which may affect the income situation of stakeholders and the sustainability of the sector. Therefore, repetitively occurring waiting problems, potentially paired with port congestion phenomena, indicating that just in time (JIT) arrival potential for a distinct or a combination of reasons has not been realised, can be frequently identified. Undesired increment of waiting times and development of port congestion is frequently responded to by an array of measures. JIT arrival concepts, vessel arrival systems (VAS) and virtual arrival (VA) agreements thereby do not strive to eliminate waiting times but facilitate their sensible transformation into additional navigation time. In practice, VAS applications may, however, only enfold their inherent sustainability potential within closely defined delimitations. At the same time, JIT mechanisms and VA agreements may lack acceptance due to impracticability or missing alignment to underlying trade requirements. Therefore, fair but environmentally inefficient arrival mechanisms like the first come first serve (FCFS) concept remain widely applied. As a remedy, a VAS has been conceptualised by diverting from a static to a dynamic time-, distance- and speed JIT concept wherein these parameters are defined by predicted berth and cargo operation availability. A circular based Reporting Line furnished with the functions attributable to the place where line up positions are customarily allocated is fluctuating in correspondence to the time to go until the nearest berthing opportunity becomes available. The concept does not only provide for a dynamically shifting line and corridor to obtain an often highly valued line up position, but for the distance and conditions where under a vessel is going to arrive JIT. The FCFS concept interwoven with unbiased allocating of line-up positions is being retained as an integral part while VA applications are supported. © 2023, The Author(s).Öğe Laminar mixed convection of power-law fluids in cylindrical enclosures with heated rotating top wall(Pergamon-Elsevier Science Ltd, 2018) Turan, Osman; Yigit, Sahin; Liang, Ruibin; Chakraborty, NilanjanLaminar mixed convection of inelastic non-Newtonian fluids obeying a power law model in a cylindrical enclosure with a heated rotating top cover has been investigated numerically in this study. The steadystate axisymmetric simulations have been carried out for a range of different nominal Reynolds, Prandtl, Richardson numbers (i.e. 500 <= Re <= 2000; 10 <= Pr <= 500 and 0 <= Ri <= 1) and power-law index (i.e. 0.6 <= n <= 1.8) for an aspect ratio (height/radius) of unity (i.e. AR = 1.0). It has been found that mean Nusselt number (Nu) over bar increases as Re and Pr increase, whereas (Nu) over bar decreases with increasing values of Ri for shear-thinning (i.e. n < 1), Newtonian (i.e. n = 1) and shear-thickening (i.e. n > 1) fluids. It has also been observed that the variation of Ni with n differs depending on the values of Re and Ri. For instance, for small values of Reynolds number, (Nu) over bar exhibits a non-monotonic trend (i.e. increases before reaching a maximum followed by a decreasing trend) with increasing n for small values of Richardson number, whereas (Nu) over bar monotonically increases with increasing values of n for high Richardson number cases. However, in the case of high Reynolds number, (Nu) over bar increases with n before reaching a maximum value which is followed by a decreasing trend for all values of Ri considered here. Detailed physical explanations are provided for the influences of Re, Pr, Ri, and n on (Nu) over bar based on an elaborate scaling analysis. Finally, the numerical findings have been used to propose a correlation for (Nu) over bar for the ranges of Re, Pr, Ri, n considered here. (C) 2018 Elsevier Ltd. All rights reserved.Öğe Mixed convection of power-law fluids in cylindrical enclosures with a cold rotating top cover and a stationary heated bottom wall(Elsevier, 2020) Turan, Osman; Yigit, Sahin; Chakraborty, NilanjanSteady-state laminar mixed convection in cylinders with a rotating top cold cover and a heated bottom has been numerically analysed for inelastic shear-thinning/shear-thickening fluids by applying power-law model of viscosity. In this analysis, axisymmetric incompressible flow simulations have been conducted for a range of different values of Reynolds, Richardson, Prandtl numbers (i.e. 500 <= Re <= 2000; 0 <= Ri <= 1.0; 10 <= Pr <= 1000) and power-law index (i.e. 0.6 n 1.8) for an aspect ratio (height/radius) of unity (i.e. AR = 1.0). The thermal convective transport has been found to strengthen with increasing Re and Pr, which in turn gives rise to an increase in the mean Nusselt number Nu. By contrast, an increase in Ri leads to a mild increase in Nu for small Richardson number values but Nu becomes insensitive to the changes in Ri for large Richardson numbers within the range of 0 <= Ri <= 1.0 for all values of n considered here. The mean Nusselt number Nu exhibits a nonmonotonic trend (i.e. increases before reaching a maximum followed by a decreasing trend) with the variation of n. The influences of Ra, Pr and Ri on the mean Nusselt number Nu have been explained in terms of scaling arguments. The scaling relations along with the numerical findings have been utilised to propose a correlation for the mean Nusselt number for the configuration and the parameter range considered here.Öğe Numerical investigation of laminar mixed convection in a square cross-sectioned cylindrical annular enclosure(2020) Turan, OsmanAbstract:Steady-state laminar mixed convection of Newtonian fluids in a square cross-sectioned cylindrical annular enclosure with rotating inner wall and heated top cover has been numerically analysed based on axisymmetric incompressible flow simulations. ...Öğe NUMERICAL INVESTIGATION OF LAMINAR MIXED CONVECTION IN A SQUARE CROSS-SECTIONED CYLINDRICAL ANNULAR ENCLOSURE(Yildiz Technical Univ, 2020) Turan, OsmanSteady-state laminar mixed convection of Newtonian fluids in a square cross-sectioned cylindrical annular enclosure with rotating inner wall and heated top cover has been numerically analysed based on axisymmetric incompressible flow simulations. Richardson number, Reynolds number and r(i)/R effects on heat and momentum transport have been investigated for the range of Richardson number 0 <= Ri <= 1, Reynolds number 500 <= Re <= 2000 and 0.25 <= r(i)/R <= 8 at a representative value of Prandtl number (i.e Pr = 1.0). A scaling analysis has been also carried out in order to elucidate the possible influences of Reynolds, Richardson and Prandtl numbers and r(i)/R on the mean Nusselt number. It has been found that the mean Nusselt number (Nu) over bar demonstrates a monotonically decreasing trend with increasing Ri whereas (Nu) over bar increases with increasing r(i)/R and Re which is consistent with scaling estimation. It is also observed that the flow pattern in the case of purely forced convection (i.e Ri > 0) is significantly different from those in mixed convection (i.e Ri > 0). In the case of Ri = 0 (i.e. purely forced convection), a one-cell flow structure with two small vortexes on the top corners is observed for r(i)/ <= 1, whereas a second cell appears in the flow field for r(i)/R > 1 at Re = 1000. On the other hand, in the case of mixed convection (i.e Ri > 0), two-cell and four-cell flow structures occur in the flow field depending on Ri and r(i)/R for the range of Ri, Re and r(i)/R considered here at Pr = 1.0. Based these observations, a flow regime diagram has been proposed here for mixed convection (i.e Ri > 0) for the range of Ri, Re and r(i)/R analysed in this study.Öğe The effects of bottom wall heating on mixed convection of yield stress fluids in cylindrical enclosures with a rotating end wall(Pergamon-Elsevier Science Ltd, 2018) Turan, Osman; Chakraborty, NilanjanSteady-state laminar mixed convection of Bingham fluids in cylindrical enclosures with a rotating top cover has been numerically analysed for the configuration where the bottom cover is kept at a higher temperature than the rotating top cover. The numerical investigations have been carried out based on steady-state axisymmetric incompressible flow simulations for a range of different values Reynolds, Richardson, and Prandtl number given by 500 <= Re 3000, 0 <= Ri <= 1 and 10 <= Pr <= 500 respectively. The aspect ratio (i.e. height: radius = AR = H/R) of the cylindrical container is considered to be unity (i.e. AR = H/R = 1). The mean Nusselt number (Nu) over bar has been found to decrease sharply with increasing Bn owing to flow resistance arising from yield stress, but subsequently (Nu) over bar asymptotically approaches a value of unity, which is indicative of a conduction-driven transport. In addition, the mean Nusselt number (Nu) over bar has been found to increase with increasing Reynolds number due to the strengthening of advective transport. However, the mean Nusselt number (Nu) over bar exhibits a non-monotonic trend (i.e. increases with increasing Ri for small values of Richardson number before showing a weak decreasing trend) with increasing Ri for Newtonian fluid (i.e. Bn = 0), whereas (Nu) over bar increases with increasing Ri for small values of Richardson number before becoming a weak function of Ri for Bingham fluids. A step change in the mean Nusselt number has also been observed with an increase in Richardson number for some Bingham number values due to a change in flow pattern. The influences of Prandtl, Reynolds, Richardson, and Bingham numbers on the mean Nusselt number have been explained in detail based on both physical and scaling arguments. The simulation data and scaling relations have been utilised to propose a correlation for the mean Nusselt number, which has been shown to capture the numerical findings satisfactorily for the parameter range considered here. 2018 Elsevier Ltd. All rights reserved.Öğe The effects of uniform injection and suction on heat transfer with viscous dissipation through a permeable surface in zero pressure gradient(Pergamon-Elsevier Science Ltd, 2020) Turan, Osman; Cuhadaroglu, BurhanIn the present study; the effects of injection/suction velocity and viscous dissipation on the temperature dis-tribution through a permeable surface with constant temperature was investigated theoretically. The hydro-dynamic and thermal wall functions which include the influence of viscous dissipation and injection/suction velocity were obtained for the boundary layer flow with zero pressure gradient in streamwise. The effect of viscous dissipation was considered with a dimensionless parameter of Br-m = u(tau)(3)rho/q(w) which is a modified Brinkman number. It was noted that the temperature distribution in both the laminar and turbulent boundary layers was substantially influenced by the viscous dissipation. Moreover, viscous dissipation induced internal heat generation causes to a jump in the fluid temperature at the wall T-w,T-f for high Br-m values. In addition, it was seen that viscous dissipation effect on temperature distribution can be noticeably controlled by using injection and suction through permeable surface. Viscous dissipation effect weakens with injection (suction) for low (high) Br-m case. Finally, the critical modified Brinkman number Br-m,Br- (crit) where the heat transfer direction begins to change with strengthening viscous dissipation induced internal heat generation in the flow field has been obtained. It has been found that Br-m,Br- (crit) increases with increasing suction velocity while it decreases with in-creasing injection velocity. It has further observed that Br-m,Br- (crit )decreases (increases) with increasing Pr for suction (injection) although it takes the same values for different Pr values in case of no-injection and suction.
