Papers by Ahmet ihsan Kutlar
Pneumatic conveying systems are widely used in a variety of industrial settings since different t... more Pneumatic conveying systems are widely used in a variety of industrial settings since different types of materials can be conveyed. There are some classifications of flow modes for conveying of powders and bulk solid particles based on mean particle size, density, and inter particle cohesion forces. In this paper, three different cases which are vertical (test case 1), horizontal (test case 2) and continuous conveying test case are constructed and considered in order to determine the flow modes in pneumatic conveying systems. Seven solid particles are used with the range of 200 kg/m 3 < ρblp < 2400 kg/ m 3 and 150 μm < dp < 2750 μm in these three cases. In vertical test setup unstable zone and fluidized dense phase is occurred, then in the horizontal test setup slug flow and plug flow is observed and lastly plug flow and dilute phase is occurred visually in continuous conveying test case. Finally, all obtained data are considered for the classification according to flow modes in pneumatic conveying systems. The observed flow modes are considered and tabulated with respect to all test cases.
Paint coating of marine (ship-hull) surfaces is known to alter the original substrate roughness t... more Paint coating of marine (ship-hull) surfaces is known to alter the original substrate roughness topography of the base surface. The effect of coating on the frictional resistance of such painted surfaces so far has not been investigated thoroughly as regards the flow wall turbulence, although a few useful and relevant papers have so far been published Musker & Sarabchi (1980) and Walderhaug (1986). None of the work done so far has concentrated on gathering of detailed data on the mean flow or on the accompanying turbulence structure along with an appropriate roughness topography survey. The present experiment was set up to fill this gap.
Progress in Computational Fluid Dynamics, 2016
Cartesian grid generation methods are especially designed algorithms to generate automatic grids ... more Cartesian grid generation methods are especially designed algorithms to generate automatic grids for complex geometries and to simulate flows around such geometries regardless of the body shape. Cartesian grids are generated by constructing an octree-based data structure for the purpose of connecting the Cartesian cells to each other. Entire algorithm is implemented in object-oriented FORTRAN programming language. Some special Cartesian algorithms, namely, Ray-Casting method and cut-cell adaptation are used around three-dimensional closed bodies. The flow field around the solid body is obtained by employing Euler equations which are discretised by using finite volume method. Validation of the numerical results is accomplished by comparison with the experimentally obtained data from the flow around ONERA M6 wing. Employing the solution adaptation techniques, pressure coefficients and contours of the flow around the wing have verified and captured two shock waves (weak leading edge shock and midchord shock) by the developed grid-generator-with-eULER-solver-for-3D-applications (GeULER3D) code.
Current Directions in Biomedical Engineering, Sep 1, 2019
Glaucoma is an eye disorder in which the optic nerve is damaged over time due to a sustained elev... more Glaucoma is an eye disorder in which the optic nerve is damaged over time due to a sustained elevation of the intraocular pressure (IOP). Being the second leading cause of blindness according to the reports of the World Health Organization, glaucoma is not only a serious ocular disease that threatens individuals, but also a community health problem. In recent years, great improvement has been achieved in the technology of implants used in the treatment of the disease. Despite the great effort dedicated to the design and implementation of the glaucoma drainage devices (GDD), they still have unsolved problems and weaknesses. Most of the currently employed GDDs are very simple and have major problems such as reversed flow, choking and a coarse interval of pressure control. Experiments must be devised to investigate the flow behavior inside these devices. In this study, an accurate microfluidics experimental setup is constructed to analyze and characterize the in-vitro performance of actively employed GDDs on the glaucoma treatment. Proposed setup includes a pressurized fluid reservoir, ELVEFLOW microfluidics flow rate measurement/control unit, microfluidics flow/pressure sensors, and data analysis system. In the setup, more precise measurements than experimental setups in literature is planned to be provided. It is estimated that the results showing consistency with in-vivo measurements will be obtained, behavior of the fluid passing through the GDDs will be observed and issues with design flaws will be addressed.
Journal of Aeronautics and Space Technologies, 2016
Cartesian grids employ specially designed algorithms to generate automatic grids for complex geom... more Cartesian grids employ specially designed algorithms to generate automatic grids for complex geometries and to simulate flows around such geometries regardless of the body shape and number of bodies. The main advantage of Cartesian methods over the body-conformal approach is that without regard to drawbacks of the geometric complexity of the embedded boundaries, the computational grid does not alter except close to all boundaries where cutcells are employed. In this study, implementation of generated two-dimensional adaptive refinement/coarsening scheme codes is appended to the developed compressible flow solver by using special Cartesian-based algorithms. Cartesian grids are generated by constructing a quadtree based data structure in two-dimensional flows. By means of solution adaptation, a finer grid is obtained around a shock wave. Convergence rate is increased with multi-grid method. Thus, a “hands-off”, Cartesian grid generator based flow solver is implemented in object-orient...
Journal of Applied Fluid Mechanics, 2019
Cartesian grids represent a special extent in unstructured grid literature. They employ chiefly c... more Cartesian grids represent a special extent in unstructured grid literature. They employ chiefly created algorithms to produce automatic meshing while simulating flows around complex geometries without considering shape of the bodies. In this article, firstly, it is intended to produce regionally developed Cartesian meshes for two dimensional and three dimensional, disordered geometries to provide solutions hierarchically. Secondly, accurate results for turbulent flows are developed by finite volume solver (GeULER-NaTURe) with both geometric and solution adaptations. As a result, a "hands-off" flow solver based on Cartesian grids as the preprocessor is performed using object-oriented programming. Spalart-Allmaras turbulence model added Reynolds Averaged Navier Stokes equations are solved for the flows around airfoils and wings. The solutions are validated and verified by one two dimensional and one three dimensional turbulent flow common test cases in literature. Both case studies disclose the efficaciousness of the developed codes and qualify in convergence and accuracy.
Energy and Buildings, 2017
HVAC systems in buildings are composed of many subcomponents which consume energy in huge amounts... more HVAC systems in buildings are composed of many subcomponents which consume energy in huge amounts. In recent years, energy consumption becomes very important aspect due to the lack of energy resources and environmental reasons. In terms of energy consumption, the components of HVAC systems account for large portion of total energy used in buildings. Therefore optimization of energy consumption in HVAC applications is an essential requirement in terms of thermodynamic and economic point of views. Besides, the efforts for decreasing energy consumption turn into economic recovery. It also provides benefits for human health and cleaner environment. In this paper, as originality, thermodynamic and economic analyses of an existing social and cultural building which has a heating and cooling area of 8852 m 2 are presented by comparing of a conventional HVAC and a VRF system. A novel contribution is given to the open literature by comparing two systems with actual data measured from the existing system. The other originality is to apply and test a VRF system to a complex-structured building. This study is a rare one which contains insulation, heating and cooling accounts of a building together. In this paper, VRF system is modelled to the existing building for the comparison of the conventional HVAC system. Both systems have been compared in terms of heating and cooling capacity, initial, operation and maintenance costs. It is found that the VRF system is more economic and efficient such that the VRF system is found to have 44% cost profit when compared with the conventional HVAC system.
AIP Conference Proceedings, 2017
International Journal of Hydrogen Energy, 2017
In this study, five models are considered for the use of biogas-based electricity and sewage slud... more In this study, five models are considered for the use of biogas-based electricity and sewage sludge obtained from a municipal wastewater treatment plant for green hydrogen production. These models include alkaline, PEM, high temperature water electrolysis, alkaline hydrogen sulfide electrolysis and dark fermentation biohydrogen production processes. Energy and exergy analyses are performed on these models by applying thermodynamic procedures and the results are compared. The daily hydrogen production rates of the
Journal of Cleaner Production, 2017
This paper presents a comparative life cycle assessment (LCA) of an existing digested sewage slud... more This paper presents a comparative life cycle assessment (LCA) of an existing digested sewage sludge incineration for heat and power production. Operations of an existing sewage sludge incineration plant based on a fluidized bed combustor (FBC) and a hypothetical cement kiln (CK) facility using sludge as a secondary fuel are described in detail as two different scenarios. The comparison of these two scenarios is performed based on 15 impact categories in the characterization stage. The results show that the sewage sludge incineration scenario based on FBC has a better environmental performance in the most of the impact categories including global warming, respiratory organic and inorganic, aquatic and terrestrial ecotoxicity, terrestrial acidification/nutrition, aquatic acidification, land occupation, and mineral extraction. In the human health category, the scores of the CK scenario precedes the scores of FBC scenario because the residual materials of the incineration in the cement kiln are immobilized with the produced clinkers whereas in the FBC system, they are landfilled. This study aims to show the environmental burdens of each option based on different impact categories in order to give a clear perspective to decision makers for drawing an environmentally friendly and sustainable sludge disposal policy.
Nevşehir Bilim ve Teknoloji Dergisi, 2015
Cartesian grids constitute a special branch in unstructured grid technology. They use specially d... more Cartesian grids constitute a special branch in unstructured grid technology. They use specially designed algorithms to generate automatic grids for complex geometries and to simulate flows around such geometries regardless of the body shape and number of bodies. Cartesian grids are generated by constructing a quadtree based data structure for the purpose of connecting the Cartesian cells to each other. A "hands-off", Cartesian grid generator based Euler solution called GeULER is implemented in object-oriented FORTRAN programming language. In this study, implementations of generated two-dimensional adaptive refinement/coarsening scheme codes are appended to the developed compressible flow solver by using special Cartesian-based algorithms, namely cut-cell adaptation and curvature adaptation around BOEING TR-1322 multi-element airfoil. A subsonic flow at free stream Mach number of 0.11 around the airfoil is tested to predict pressure distributions around it and Mach contours of the flow are depicted by using the developed GeULER code.
Biophysical Journal, 2012
electron donating properties that would optimize photoinduced electron transfer (PET) from the li... more electron donating properties that would optimize photoinduced electron transfer (PET) from the ligand to the protein and prompt charge-induced conformational changes. Our study focuses on the interaction of four 3,9-substituted perylenes with Human Serum Albumin (HSA), which is the prime protein model for the binding of PAH. We present docking simulation results for possible sites for the perylenes within HSA with the lowest free energy of binding and correlate the docking simulations with fluorescence result. Docking simulations reveal that all the peylen derivatives bind at the core of HSA and that the dimethoxy derivative has larger affinity than the other perylenes. Docking seems to be stabilized by aromatic interactions with Tyr and Trp groups.
Nevşehir Bilim ve Teknoloji Dergisi, 2015
Cartesian grids constitute a special branch in unstructured grid technology. They use specially d... more Cartesian grids constitute a special branch in unstructured grid technology. They use specially designed algorithms to generate automatic grids for complex geometries and to simulate flows around such geometries regardless of the body shape and number of bodies. Cartesian grids are generated by constructing a quadtree based data structure for the purpose of connecting the Cartesian cells to each other. A "hands-off", Cartesian grid generator based Euler solution called GeULER is implemented in object-oriented FORTRAN programming language. In this study, implementations of generated two-dimensional adaptive refinement/coarsening scheme codes are appended to the developed compressible flow solver by using special Cartesian-based algorithms, namely cut-cell adaptation and curvature adaptation around BOEING TR-1322 multi-element airfoil. A subsonic flow at free stream Mach number of 0.11 around the airfoil is tested to predict pressure distributions around it and Mach contours of the flow are depicted by using the developed GeULER code.
Particulate Science and Technology, 2008
Discharge characteristics of polydisperse powders through a conical hopper were experimentally in... more Discharge characteristics of polydisperse powders through a conical hopper were experimentally investigated by observing the solids discharge regimes under different positive pressure differences (i.e., ΔP > 0) and also measuring the corresponding solids discharge rates. The observations and measurements were systematically conducted at least four diameters of hopper orifice (2.5 mm ≤ Do ≤ 30.0 mm) under five positive ΔP values (0 Pa ≤ ΔP ≤ 1405 Pa) for the test powders: river sand, zeolite, fertilizer, and sawdust. Effects of positive ΔP on both discharge regime and solids discharge rate are first predicted for different orifice diameters and test powders in this study. One of the novel results on the discharge regime is that increase of positive ΔP value up to a critical value conserves or successively stabilizes the discharge regime observed when ΔP = 0 (i.e., for gravity flow condition) through the same hopper. However, the additional increase of positive ΔP over this critical value destabilizes the discharge regime, as in conformity with the effect of increase in negative ΔP cited in the literature.
Advanced Powder Technology, 2009
Commonly used glaucoma drainage devices have many disadvantageouscircumstancesespecially in posto... more Commonly used glaucoma drainage devices have many disadvantageouscircumstancesespecially in postoperative period such as hypotony, flammation, etc. There are great efforts to overcome these problems in literature. Researchershave investigated glaucoma drainage devicesby in-vivo, ex-vivo and in-vitro experimental setups and tried to overcome their disadvantages. In this study,one branch of them, in-vitro experimental setups currently usedin testing of glaucoma drainage devices are surveyed.
The developed Cartesian-grid based GeULER-NS code is validated for compressible and laminar flows... more The developed Cartesian-grid based GeULER-NS code is validated for compressible and laminar flows on subsonic viscous flow over a NACA 0012 airfoil. Solution refinement effectiveness and Roe’s flux calculation versus AUSM are tested. Drag coefficient results, skin friction coefficient distribution and symmetric behavior of the distribution are compared with the results from milestone computational studies found in literature.
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Papers by Ahmet ihsan Kutlar