Researcher: Öztürk, Çağlar
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Öztürk, Çağlar
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Publication Metadata only A novel approach to tube design via von Mises probability distribution(Taylor & Francis Ltd) Subay, Şehmuz Ali; N/A; N/A; N/A; Department of Mechanical Engineering; Oral, Atacan; Subaşı, Ömer; Öztürk, Çağlar; Lazoğlu, İsmail; PhD Student; Researcher; PhD student; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; N/A; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 179391Discharge tube is a critical component in a reciprocating compressor that carries the refrigerant. It also transmits vibrations from compressor body to housing, making the design of tube a complex engineering problem combining static, modal and flow behaviour. This study proposes a novel design algorithm for discharge tube, to decrease the dependency on the trial-and-error approach commonly used by manufacturers. The computational approach creates a tube that connects the inlet and outlet using von Mises probability distribution. The created geometries are checked for static and dynamic properties using FEA. The algorithm continues until a candidate design passes the imposed thresholds. The candidate designs perform similarly to benchmark in evaluated aspects, demonstrating promising results. The presented algorithm is successful in generating alternative tube designs from scratch and can accommodate varying requirements. The main novelty of this study is the development of a comprehensive decision algorithm that considers multiple engineering parameters simultaneously.Publication Metadata only A short-term in vivo evaluation of the Istanbul heart left ventricular assist device in a pig model(Middle East Society for Organ Transplantation, 2019) Küçükaksu, Deniz Süha; Bakuy, Vedat; Arat, Nurcan; Erkasap, Pelin Çelikbilek; Aksoy, Emin; Department of Mechanical Engineering; N/A; N/A; N/A; N/A; N/A; Lazoğlu, İsmail; Öztürk, Çağlar; Aka, İbrahim Başar; Yalçın, Özlem; Uğurel, Elif; Ruacan, Ahmet Şevket; Faculty Member; PhD Student; PhD Student; Faculty Member; Researcher; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; School of Medicine; School of Medicine; School of Medicine; 179391; N/A; N/A; 218440; N/A; N/AObjectives: a continuous-flow centrifugal blood pump system has been recently developed as an implantable left ventricular assist device for patients with endstage heart failure. The objective of this study was to evaluate the initial in vivo performance of a newly developed left ventricular assist device (iHeart or Istanbul heart; Manufacturing and Automation Research Center, Koc University, Istanbul, Turkey) in an acute setting using a pig model. Materials and Methods: three pigs (77, 83, 92 kg) received implants via a median sternotomy, with animals supported for up to 6 hours. An outflow cannula was anastomosed to the ascending aorta. Anticoagulation was applied by intravenous heparin administration. During the support period, pump performance was evaluated under several flow and operating conditions. All pigs were humanely sacrificied after the experiments, and organs were examined macroscopically and histopathologically. Results: flow rate ranged between 1.5 and 3.6 L/min with pump speeds of 1500 to 2800 revolutions/min and motor current of 0.6 to 1.3 A. Initial findings confirmed thatthe iHeart ventricular assist device had sufficient hydraulic performance to support the circulation. During the experimental period, plasma free hemoglobin levels were found to be within normalranges. Thrombus formation was not observed inside the pump in all experiments. Conclusions: the iHeart ventricular assist device demonstrated encouraging hemodynamic performance and good biocompatibility in the pig model for use as an implantable left ventricular assist device. Further acute in vivo studies will evaluate the short-term pump performance prior to chronic studies for long-term evaluation.Publication Metadata only Mechanics of milling 48-2-2 gamma titanium aluminide(Elsevier, 2020) Layegen, S. Ehsan; Arrazola, Pedro-J.; Lazcano, Xabier; Aristimuno, Patxi-X.; Subaşı, Ömer; Yavaş, Çağlar; N/A; Department of Mechanical Engineering; N/A; N/A; Hussain, Abbas; Lazoğlu, İsmail; Yiğit, İsmail Enes; Öztürk, Çağlar; PhD Student; Faculty Member; PhD Student; PhD Student; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; N/A; 179391; N/AAccurate and fast prediction of cutting forces is important in high-performance cutting in the aerospace industry. Gamma titanium aluminide (gamma-TiAl) is a material of choice for aerospace and automotive applications due to its superior thermo-mechanical properties. Nevertheless, it is a difficult to machine material. This article presents the prediction of cutting forces for Ti-48Al-2Cr-2Nb (48-2-2) gamma-TiAl in milling process using orthogonal to oblique transformation technique. The novelty of this paper lies in reporting the orthogonal database of 48-2-2 gamma-TiAl. Fundamental cutting parameters such as shear stress, friction angle and shear angle are calculated based on experimental measurements. Friction coefficients are identified for two different coating conditions which are AlTiN, and AlCrN on carbide tools. Predicted results are validated with the experimental cutting forces during end milling and ball-end milling operations for different cutting conditions. The simulated results showed good agreement with the experimental results, which confirms the validity of the force model.Publication Metadata only Effect of blade curvature on the hemolytic and hydraulic characteristics of a centrifugal blood pump(Sage Publications Ltd, 2018) N/A; N/A; N/A; Department of Mechanical Engineering; Öztürk, Çağlar; Aka, İbrahim Başar; Lazoğlu, İsmail; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 179391Aims: Impeller design has a significant impact on the overall performance of a blood pump. In this study, the effect of the blade curvature was investigated by performing in silico and in vitro studies on a recently developed centrifugal blood pump. Methods: A computational fluid dynamics study was performed for the flow rates of 3-5 L/min at 2000 r/min. The computational fluid dynamics model was also applied on the US Food and Drug Administration (FDA) benchmark blood pump to validate our computational method. The relative hemolysis index was calculated with the Eulerian hemolysis estimation method for five impellers with the wrap angles ranging from 0 degrees to 240 degrees. Hydraulic experiments were conducted for the validation of computational fluid dynamics results. In addition, the curved-blade impeller (120 degrees) and the straight-blade impeller (0 degrees) were evaluated with in vitro hemolysis tests using human blood. Results: The wrap angle of 120 degrees provided the best hydraulic and hemolytic performance. Pump achieved the physiologic operating pressures and flows with 85-115 mmHg at 2.5-5.9 L/min. Compared to the straight-blade impeller, the 120 degrees model reduces the relative hemolysis index and the plasma-free hemoglobin near 72.8% and 56.7%, respectively. Comparison of in silico and in vitro results indicated the similar trend to the blade curvature. Conclusion: Introducing a blade curvature enhanced the hydrodynamic and hemolytic performance compared to the straight-blade configuration for the investigated centrifugal blood pump. The findings of this study provide new insights into centrifugal blood pump design by examining the influence of the blade curvature.Publication Open Access Numerical investigation of volute tongue design on hemodynamic characteristics and hemolysis of the centrifugal blood pump(Springer, 2021) Aka, İbrahim Başar; N/A; Department of Mechanical Engineering; Öztürk, Çağlar; Lazoğlu, İsmail; PhD student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179391In the design of rotary blood pumps, the optimization of design parameters plays an essential role in enhancing the hydrodynamic performance and hemocompatibility. This study investigates the influence of the volute tongue angle as a volute geometric parameter on the hemodynamic characteristics of a blood pump. A numerical investigation on five different versions of volute designs is carried out by utilizing a computational fluid dynamics (CFD) software ANSYS-FLUENT. The effect of volute tongue angle is evaluated regarding the hydrodynamic performance, circumferential pressure distribution, the radial force, and the blood damage potential. A series of volute configurations are constructed with a fixed radial gap (5%), but varying tongue angles ranging from 10 to 50 degrees. The relative hemolysis is assessed with the Eulerian based empirical power-law blood damage model. The pressure-flow rate characteristics of the volute designs at a range of rotational speeds are obtained from the experimental measurements by using the blood analog fluid. The results indicate an inverse relationship between hydraulic performance and the tongue angle; at higher tongue angles, a decrease in performance was observed. However, a higher tongue angle improves the net radial force acting on the impeller. The pump achieves the optimized performance at 20 degrees of the tongue angle with the relatively high hydrodynamic performance and minor blood damage risk.