Yazar "Canbolat, Gökhan" seçeneğine göre listele

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    A Numerical Study on Cross Flow Heat Exchanger with Different Reynolds (Re) Numbers
    (Alanya Alaaddin Keykubat University, 2023) Canbolat, Gökhan
    Heat exchangers are highly popular in engineering and industrial applications. Numerical studies on heat exchangers to investigate the performance of heat transfer have been carried out widely by Computational Fluid Dynamics (CFD) in recent years. In this study, a circular pipe with hot water in cross flow is investigated in different Reynolds (Re) numbers. Flow is turbulent flow and the Re number varies from 3165 to 4643 in the circular pipe. The air is at a temperature of 303 K and the water is at 333 K. Variation of flow characteristics and thermal performance is observed according to an increase in Re numbers such as Wall Shear Stress (WSS), Skin Friction Coefficient (Cf), Nusselt Number (Nu), heat transfer coefficient (h) and surface temperature of the circular pipe. Results show that there are no significant changes for the WSS and Cf values in the specified range of the Re number. However, when the thermal performance is evaluated, the temperature of the surface of the circular pipe, heat transfer coefficient, and Nu number values are increased by an increase in the Re number. Here, the increase is approximately 2% for the specified range of Re number, and it is shown that it can be increased by the flow conditions. The maximum Nu number is 4482.37 at the Re number of 4643. As a result, the Re number is highly effective in controlling the heat transfer performance of a heat exchanger
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    Analysis of One-Way Fluid-Structure Interactions for a Straight Pipe under Different Thermal and Pressure Conditions
    (2023) Canbolat, Gökhan
    Numerical studies on stress, deformation, and damages due to fluid flow have been highly carried out using Fluid-Structure Interaction (FSI) in recent years. FSI is highly efficient in investigating a solid domain deformed by the fluid flow. In this study, a one-way fluid-structure interaction study is performed by a straight pipe under different pressure and thermal conditions. Here, the thermophysical properties of the fluid and mechanical properties of the solid domain can be subjected to change during fluid flow. An aluminum straight pipe with a 1 mm wall thickness is operated under 1 Bar, 5 Bar, and 10 Bar with three different surface temperatures -10ºC, 20ºC, and 50ºC. This study aims to investigate the structural variation of aluminum by the temperature and pressure change of operating fluid in the pipe. Variation of thermophysical properties of fluid by heated pipe surface is integrated into the numerical analysis by generated functions. Numerical analysis showed that the variation of temperature in operating fluid highly affects the fluid characteristic and the structural response of the solid domain by different temperatures. An increase in the operating pressure caused maximum deformation to approximately %100 from 1 Bar to 5 Bar, and approximately %120 from 1 Bar to 10 Bar for the adiabatic process as expected but in the heating conditions stress is nearly three times higher than cooling conditions. As a result, one-way FSI solutions are highly effective in investigating the deformed solid domain as a result of flow, thermal, and operating conditions.
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    Numerical Investigation of Hydrodynamic and Thermal Boundary Layer Flows over a Flat Plate and Transition Control
    (2020) Canbolat, Gökhan; Yıldızeli, Alperen; Köse, Haluk Anıl; Cadirci, Sertac
    In this study, Computational Fluid Dynamics (CFD) calculations are performed with ANSYS-Fluent for an external flow over a flat plate under constant surface temperature conditions. By using an Active Flow Control (AFC) method, the flat-plate is heated to manipulate the transition region. Calculations are performed for a steady and turbulent flow at 15 m/s free-stream velocity. Local skin friction coefficient and local heat transfer coefficient distributions along the flat-plate are investigated for laminar and turbulent boundary layers at various constant surface temperatures. For laminar and turbulent flow boundary layer characteristics, theoretical correlations in the literature are used to verify the numerical results. Results show that theoretical correlations are highly consistent with CFD results only in the laminar and turbulent regions and it is also shown that transition can only be predicted by CFD simulations. On the other hand, heating as an AFC method is found to be useful in delaying transitionregime over a flat plate.
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    Numerical investigation of patient-specific thoracic aortic aneurysms and comparison with normal subject via computational fluid dynamics (CFD)
    (Springer Heidelberg, 2021) Etli, Mustafa; Canbolat, Gökhan; Karahan, Oğuz; Koru, Murat
    Vascular hemodynamics play an important role in cardiovascular diseases. This work aimed to investigate the effects of an increase in ascending aortic diameter (AAD) on hemodynamics throughout a cardiac cycle for real patients. In this study, two scans of thoracic aortic aneurysm (TAA) subject with different AADs (42.94 mm and 48.01 mm) and a scan of a normal subject (19.81 mm) were analyzed to assess the effects of hemodynamics on the progression of TAA with the same flow rate. Real-patient aortic geometries were scanned by computed tomography angiography (CTA), and steady and pulsatile flow conditions were used to simulate real patient aortic geometries. Aortic arches were obtained from routine clinical scans. Computational fluid dynamics (CFD) simulations were performed with in vivo boundary conditions, and 3D Navier-Stokes equations were solved by a UDF (user-defined function) code defining a real cardiac cycle of one patient using Fourier series (FS). Wall shear stress (WSS) and pressure distributions were presented from normal subject to TAA cases. The results show that during the peak systolic phase pressure load increased by 18.56% from normal subject to TAA case 1 and by 23.8% from normal subject to TAA case 2 in the aneurysm region. It is concluded that although overall WSS increased in aneurysm cases but was low in dilatation areas. As a result, abnormal changes in WSS and higher pressure load may lead to rupture and risk of further dilatation. CFD simulations were highly effective to guide clinical predictions and assess the progress of aneurysm regions in case of early surgical intervention.