Serkan Özgen - Academia.edu (original) (raw)
Papers by Serkan Özgen
This work describes the optimization process of a morphing wing for an unmanned air vehicle (UAV)... more This work describes the optimization process of a morphing wing for an unmanned air vehicle (UAV) by using multi-objective gradient based optimization algorithm in which maximization of lift to drag ratio and minimization of bending moment at wing root chord plane are defined as the objective functions. Six different optimization problems are solved by changing weighted sum coefficients of the objective functions in order to observe the morphing wing planform and the airfoil shape change. According to the results, 15.2% lift to drag ratio increase is obtained while the increase in the bending moment is 2%. * , and maximum speed, + , of the base UAV, BASE, are defined as inequality constraints so that OPT can satisfy level flight at these speeds. After that, the multi-objective morphing wing optimization problem is defined. In this problem, both maximization of and minimization of bending moment around the root chord plane are defined as objective functions by using the weighted sum method. Six different optimization problems are solved by changing the weighting coefficients. The aerodynamic design tool consists of the three-dimensional panel method, twodimensional boundary layer solution and generalized reduced gradient method-based optimization algorithm. Wing lift, , , wing-induced drag, ,-, and wing pressure drag, ,/ , are obtained by using the three-dimensional panel method, which is a first-order method and consists of constant strength sources and doublets. Wing skin friction drag, ,0 , is calculated by using the two-dimensional laminar and turbulent boundary layer models of Thwaites and Head, respectively. Aerodynamic forces on horizontal tail, vertical tail and body are calculated by conceptual design empirical formulas. Generalized reduced gradient method algorithm is used as the optimization solver.
Ice accretion on unmanned air vehicle's wing modifies the initial airfoil contour and changes the... more Ice accretion on unmanned air vehicle's wing modifies the initial airfoil contour and changes the aerodynamic characteristic of the wing. The aim of this research is to calculate performance losses on a wing due to the accretion of rime ice. In this study, ice formation on NREL S826 airfoil is predicted by using ice accretion tool. The computed aerodynamic loads are compared for clean wings and iced wings with different aspect ratios. The computations are based on the lifting-line method. According to the results, predicted aerodynamic performance loss is higher for small aspect ratio than that of the bigger for the rime ice.
9th AIAA Atmospheric and Space Environments Conference
© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Computa... more © 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Computational studies have been performed in order to predict mixed phase ice accretion on aircraft components. In-house developed TAICE tool has been used in this study. Previously, TAICE was already validated for icing cases due to water droplets only. In addition, in the framework of High Altitude Ice Crystals (HAIC) FP7 European project, mixed phase ice accretion prediction capability has been added to TAICE. Up to now, Turkish Aerospace Industries (TAI) has implemented models related to ice crystal accretion calculation. Drag coefficient prediction, heat transfer & phase change, impingement, erosion and accretion models are among these models. Moreover, extended Messinger model has been modified for mixed phase icing conditions and are used in this study. Validations of the generated tool have been performed before by using COX and NASA-NRC wind tunnel results. Numerical comparison results on representative pitot probe and engine inlet are given to show capability of the tool
Journal of Aeronautics and Space Technologies (Havacilik ve Uzay Teknolojileri Dergisi), 2020
Ice accretion on unmanned air vehicle's wing modifies the initial airfoil contour and changes... more Ice accretion on unmanned air vehicle's wing modifies the initial airfoil contour and changes the aerodynamic characteristic of the wing. The aim of this research is to calculate performance losses on a wing due to the accretion of rime ice. In this study, ice formation on NREL S826 airfoil is predicted by using ice accretion tool. The computed aerodynamic loads are compared for clean wings and iced wings with different aspect ratios. The computations are based on the lifting-line method. According to the results, predicted aerodynamic performance loss is higher for small aspect ratio than that of the bigger for the rime ice.
This work describes the optimization process of a morphing wing for an unmanned air vehicle (UAV)... more This work describes the optimization process of a morphing wing for an unmanned air vehicle (UAV) by using multi-objective gradient based optimization algorithm in which maximization of lift to drag ratio and minimization of bending moment at wing root chord plane are defined as the objective functions. Six different optimization problems are solved by changing weighted sum coefficients of the objective functions in order to observe the morphing wing planform and the airfoil shape change. According to the results, 15.2% lift to drag ratio increase is obtained while the increase in the bending moment is 2%.
Computers & Fluids, 2019
Ice accretion on wind turbine blades distorts blade profiles and causes degradation in the aerody... more Ice accretion on wind turbine blades distorts blade profiles and causes degradation in the aerodynamic characteristic of the blades. In this study ice accretion on turbine blades are simulated under various icing conditions, and the resulting power losses are estimated. The Blade Element Momentum method is employed together with an ice accretion prediction methodology based on the Extended Messinger model in a parallel computing environment. The predicted iced profiles are first validated with the experimental and numerical data available in the literature. 2D flow solutions and aerodynamic loads over iced blade profiles are obtained with 3 different flow solvers of increasing fidelity; XFOIL, an open-source panel code coupled with a turbulent boundary layer model, SU2, an open-source RANS solver, and METUDES, an inhouse DDES solver. The power production losses of a 30 kW wind turbine operating with iced blades are then investigated in detail. It is shown that the XFOIL-based tool developed for the performance analysis of iced wind turbines successfully predicts ice profiles on turbine blades under various icing conditions and the consequent power losses. About 20% power loss is predicted for a 30 kW wind turbine exposed to icing conditions for an hour.
Mixed phase ice accretion prediction capability of the 3D version of TAICE is presented in this s... more Mixed phase ice accretion prediction capability of the 3D version of TAICE is presented in this study. First, computational approach while performing numerical analyses is detailed. In this part, the effect of the number of panels used in the chordwise direction and the effect of number of time steps used in the multi-step analyses are discussed. Then, in-flight ice formation results on finite wings are given. COX and TUBS experimental results are used for ice shape comparisons on wing sections in order to validate the tool. Thus, the present study is an effort to extend the previous work on two-dimensional analysis to three dimensions and to predict ice shapes with the new tool.
This paper provides solution method and sample results for discontinuous Galerkin finite element ... more This paper provides solution method and sample results for discontinuous Galerkin finite element method (DG-FEM) solutions of two dimensional Euler equations which govern the inviscid and adiabatic flows with a set of quasi-steady hyperbolic equations. DG-FEM discretization of Euler equations are presented with proper boundary conditions. Implementation of boundary conditions is discussed in detail. Choice of flux function and limiting are addressed through the discretization. An explicit time integration method is chosen. Since the DG-FEM solves each cell in a discontinuous manner and cells are only connected to their neighbors, it is highly suitable for an object oriented approach and parallelization. INTRODUCTION Particularly in aerospace industry, understanding the fluid dynamics has enormous importance in the design process of the products. Experimental and theoretical approaches are two historically major branches of fluid dynamics. Experimentation helps to understand and eval...
In this article, a linear stability analysis is presented for a liquid jet discharging into a sta... more In this article, a linear stability analysis is presented for a liquid jet discharging into a stagnant gas medium. Following the usual approach for a linear analysis, a dispersion relation that relates the amplification factor of a disturbance to its wave number is obtained from the equations of motion for incompressible, viscous, axisymmetric flows in cylindrical coordinates. Surface tension, viscosity of the liquid and electrical charge are the parameters of the problem. It is shown that the surface tension stabilizes the flow in the atomization regime, while the electric charges destabilize it. These results are in agreement with the results of the inviscid analysis. On the other hand, a more viscous liquid jet results in a more stable flow.
Objective of the study is to employ a scaling method that produces scaled ice accretions over a w... more Objective of the study is to employ a scaling method that produces scaled ice accretions over a wide range of test conditions and to validate the method before the icing wind tunnel tests. A scaling method for size and test-condition scaling that is based on similitudes of geometry, flow field, droplet trajectory, water catch, energy balance and surface water dynamics is validated with icing analyses for reference and scaled conditions using FENSAP-ICE software and an in-house icing code AEROMSICE-2D. The ice accretions obtained by analyses are compared with experimental data and the scaling method is tested for several Appendix-C icing conditions. Comparisons of reference and scaled results show good agreement. INTRODUCTION Icing is one of the most dangerous hazards to be encountered by air vehicles in flight. The formation of ice on aircraft surfaces occurs during flight through supercooled droplets. Supercooling is the state in which water exists as a liquid at a temperature belo...
In the present study, the aim is to predict ice accumulation on a 2-D commercial engine intake. T... more In the present study, the aim is to predict ice accumulation on a 2-D commercial engine intake. The developed tool mainly consists of four modules: modules for the calculation of the flow-field, droplet trajectories and collection efficiencies, thermodynamics and ice accretion. The flow-field solution is done by a panel method modified for the intake geometry and the required engine mass flow rate using a superposition technique. The droplet trajectories are computed using the Lagrangian approach, while the Extended Messinger Model is implemented in the ice accretion module. The results are compared with numerical literature data.
The mission adaptive wings aim to overcome the inefficient behaviour of the classical fixed wings... more The mission adaptive wings aim to overcome the inefficient behaviour of the classical fixed wings, especially for the off-design conditions, by changing their geometry actively to adopt to changing flight conditions for maximized performance. This study presents the structural design, analysis and experimental modal testing of an unmanned aerial vehicle wing having mission adaptive characteristics.
In this study, the developing steps of aerodynamic and structural design and optimization of full... more In this study, the developing steps of aerodynamic and structural design and optimization of fully morphing wings were presented. The fully morphing wings are the outcome of recent advances in the production of adaptive aerospace materials and structures and can provide the optimum shape for varying flight conditions such as, diving, climbing, cruising, maneuvering and loitering.
Journal of Physics: Conference Series, 2016
Ice accretion on wind turbine blades modifies the sectional profiles and causes alteration in the... more Ice accretion on wind turbine blades modifies the sectional profiles and causes alteration in the aerodynamic characteristic of the blades. The objective of this study is to determine performance losses on wind turbines due to the formation of ice in cold climate regions and mountainous areas where wind energy resources are found. In this study, the Blade Element Momentum method is employed together with an ice accretion prediction tool in order to estimate the ice build-up on wind turbine blades and the energy production for iced and clean blades. The predicted ice shapes of the various airfoil profiles are validated with the experimental data and it is shown that the tool developed is promising to be used in the prediction of power production losses of wind turbines.
SAE Technical Paper Series, 2015
This work describes the optimization process of a morphing wing for an unmanned air vehicle (UAV)... more This work describes the optimization process of a morphing wing for an unmanned air vehicle (UAV) by using multi-objective gradient based optimization algorithm in which maximization of lift to drag ratio and minimization of bending moment at wing root chord plane are defined as the objective functions. Six different optimization problems are solved by changing weighted sum coefficients of the objective functions in order to observe the morphing wing planform and the airfoil shape change. According to the results, 15.2% lift to drag ratio increase is obtained while the increase in the bending moment is 2%. * , and maximum speed, + , of the base UAV, BASE, are defined as inequality constraints so that OPT can satisfy level flight at these speeds. After that, the multi-objective morphing wing optimization problem is defined. In this problem, both maximization of and minimization of bending moment around the root chord plane are defined as objective functions by using the weighted sum method. Six different optimization problems are solved by changing the weighting coefficients. The aerodynamic design tool consists of the three-dimensional panel method, twodimensional boundary layer solution and generalized reduced gradient method-based optimization algorithm. Wing lift, , , wing-induced drag, ,-, and wing pressure drag, ,/ , are obtained by using the three-dimensional panel method, which is a first-order method and consists of constant strength sources and doublets. Wing skin friction drag, ,0 , is calculated by using the two-dimensional laminar and turbulent boundary layer models of Thwaites and Head, respectively. Aerodynamic forces on horizontal tail, vertical tail and body are calculated by conceptual design empirical formulas. Generalized reduced gradient method algorithm is used as the optimization solver.
Ice accretion on unmanned air vehicle's wing modifies the initial airfoil contour and changes the... more Ice accretion on unmanned air vehicle's wing modifies the initial airfoil contour and changes the aerodynamic characteristic of the wing. The aim of this research is to calculate performance losses on a wing due to the accretion of rime ice. In this study, ice formation on NREL S826 airfoil is predicted by using ice accretion tool. The computed aerodynamic loads are compared for clean wings and iced wings with different aspect ratios. The computations are based on the lifting-line method. According to the results, predicted aerodynamic performance loss is higher for small aspect ratio than that of the bigger for the rime ice.
9th AIAA Atmospheric and Space Environments Conference
© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Computa... more © 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Computational studies have been performed in order to predict mixed phase ice accretion on aircraft components. In-house developed TAICE tool has been used in this study. Previously, TAICE was already validated for icing cases due to water droplets only. In addition, in the framework of High Altitude Ice Crystals (HAIC) FP7 European project, mixed phase ice accretion prediction capability has been added to TAICE. Up to now, Turkish Aerospace Industries (TAI) has implemented models related to ice crystal accretion calculation. Drag coefficient prediction, heat transfer & phase change, impingement, erosion and accretion models are among these models. Moreover, extended Messinger model has been modified for mixed phase icing conditions and are used in this study. Validations of the generated tool have been performed before by using COX and NASA-NRC wind tunnel results. Numerical comparison results on representative pitot probe and engine inlet are given to show capability of the tool
Journal of Aeronautics and Space Technologies (Havacilik ve Uzay Teknolojileri Dergisi), 2020
Ice accretion on unmanned air vehicle's wing modifies the initial airfoil contour and changes... more Ice accretion on unmanned air vehicle's wing modifies the initial airfoil contour and changes the aerodynamic characteristic of the wing. The aim of this research is to calculate performance losses on a wing due to the accretion of rime ice. In this study, ice formation on NREL S826 airfoil is predicted by using ice accretion tool. The computed aerodynamic loads are compared for clean wings and iced wings with different aspect ratios. The computations are based on the lifting-line method. According to the results, predicted aerodynamic performance loss is higher for small aspect ratio than that of the bigger for the rime ice.
This work describes the optimization process of a morphing wing for an unmanned air vehicle (UAV)... more This work describes the optimization process of a morphing wing for an unmanned air vehicle (UAV) by using multi-objective gradient based optimization algorithm in which maximization of lift to drag ratio and minimization of bending moment at wing root chord plane are defined as the objective functions. Six different optimization problems are solved by changing weighted sum coefficients of the objective functions in order to observe the morphing wing planform and the airfoil shape change. According to the results, 15.2% lift to drag ratio increase is obtained while the increase in the bending moment is 2%.
Computers & Fluids, 2019
Ice accretion on wind turbine blades distorts blade profiles and causes degradation in the aerody... more Ice accretion on wind turbine blades distorts blade profiles and causes degradation in the aerodynamic characteristic of the blades. In this study ice accretion on turbine blades are simulated under various icing conditions, and the resulting power losses are estimated. The Blade Element Momentum method is employed together with an ice accretion prediction methodology based on the Extended Messinger model in a parallel computing environment. The predicted iced profiles are first validated with the experimental and numerical data available in the literature. 2D flow solutions and aerodynamic loads over iced blade profiles are obtained with 3 different flow solvers of increasing fidelity; XFOIL, an open-source panel code coupled with a turbulent boundary layer model, SU2, an open-source RANS solver, and METUDES, an inhouse DDES solver. The power production losses of a 30 kW wind turbine operating with iced blades are then investigated in detail. It is shown that the XFOIL-based tool developed for the performance analysis of iced wind turbines successfully predicts ice profiles on turbine blades under various icing conditions and the consequent power losses. About 20% power loss is predicted for a 30 kW wind turbine exposed to icing conditions for an hour.
Mixed phase ice accretion prediction capability of the 3D version of TAICE is presented in this s... more Mixed phase ice accretion prediction capability of the 3D version of TAICE is presented in this study. First, computational approach while performing numerical analyses is detailed. In this part, the effect of the number of panels used in the chordwise direction and the effect of number of time steps used in the multi-step analyses are discussed. Then, in-flight ice formation results on finite wings are given. COX and TUBS experimental results are used for ice shape comparisons on wing sections in order to validate the tool. Thus, the present study is an effort to extend the previous work on two-dimensional analysis to three dimensions and to predict ice shapes with the new tool.
This paper provides solution method and sample results for discontinuous Galerkin finite element ... more This paper provides solution method and sample results for discontinuous Galerkin finite element method (DG-FEM) solutions of two dimensional Euler equations which govern the inviscid and adiabatic flows with a set of quasi-steady hyperbolic equations. DG-FEM discretization of Euler equations are presented with proper boundary conditions. Implementation of boundary conditions is discussed in detail. Choice of flux function and limiting are addressed through the discretization. An explicit time integration method is chosen. Since the DG-FEM solves each cell in a discontinuous manner and cells are only connected to their neighbors, it is highly suitable for an object oriented approach and parallelization. INTRODUCTION Particularly in aerospace industry, understanding the fluid dynamics has enormous importance in the design process of the products. Experimental and theoretical approaches are two historically major branches of fluid dynamics. Experimentation helps to understand and eval...
In this article, a linear stability analysis is presented for a liquid jet discharging into a sta... more In this article, a linear stability analysis is presented for a liquid jet discharging into a stagnant gas medium. Following the usual approach for a linear analysis, a dispersion relation that relates the amplification factor of a disturbance to its wave number is obtained from the equations of motion for incompressible, viscous, axisymmetric flows in cylindrical coordinates. Surface tension, viscosity of the liquid and electrical charge are the parameters of the problem. It is shown that the surface tension stabilizes the flow in the atomization regime, while the electric charges destabilize it. These results are in agreement with the results of the inviscid analysis. On the other hand, a more viscous liquid jet results in a more stable flow.
Objective of the study is to employ a scaling method that produces scaled ice accretions over a w... more Objective of the study is to employ a scaling method that produces scaled ice accretions over a wide range of test conditions and to validate the method before the icing wind tunnel tests. A scaling method for size and test-condition scaling that is based on similitudes of geometry, flow field, droplet trajectory, water catch, energy balance and surface water dynamics is validated with icing analyses for reference and scaled conditions using FENSAP-ICE software and an in-house icing code AEROMSICE-2D. The ice accretions obtained by analyses are compared with experimental data and the scaling method is tested for several Appendix-C icing conditions. Comparisons of reference and scaled results show good agreement. INTRODUCTION Icing is one of the most dangerous hazards to be encountered by air vehicles in flight. The formation of ice on aircraft surfaces occurs during flight through supercooled droplets. Supercooling is the state in which water exists as a liquid at a temperature belo...
In the present study, the aim is to predict ice accumulation on a 2-D commercial engine intake. T... more In the present study, the aim is to predict ice accumulation on a 2-D commercial engine intake. The developed tool mainly consists of four modules: modules for the calculation of the flow-field, droplet trajectories and collection efficiencies, thermodynamics and ice accretion. The flow-field solution is done by a panel method modified for the intake geometry and the required engine mass flow rate using a superposition technique. The droplet trajectories are computed using the Lagrangian approach, while the Extended Messinger Model is implemented in the ice accretion module. The results are compared with numerical literature data.
The mission adaptive wings aim to overcome the inefficient behaviour of the classical fixed wings... more The mission adaptive wings aim to overcome the inefficient behaviour of the classical fixed wings, especially for the off-design conditions, by changing their geometry actively to adopt to changing flight conditions for maximized performance. This study presents the structural design, analysis and experimental modal testing of an unmanned aerial vehicle wing having mission adaptive characteristics.
In this study, the developing steps of aerodynamic and structural design and optimization of full... more In this study, the developing steps of aerodynamic and structural design and optimization of fully morphing wings were presented. The fully morphing wings are the outcome of recent advances in the production of adaptive aerospace materials and structures and can provide the optimum shape for varying flight conditions such as, diving, climbing, cruising, maneuvering and loitering.
Journal of Physics: Conference Series, 2016
Ice accretion on wind turbine blades modifies the sectional profiles and causes alteration in the... more Ice accretion on wind turbine blades modifies the sectional profiles and causes alteration in the aerodynamic characteristic of the blades. The objective of this study is to determine performance losses on wind turbines due to the formation of ice in cold climate regions and mountainous areas where wind energy resources are found. In this study, the Blade Element Momentum method is employed together with an ice accretion prediction tool in order to estimate the ice build-up on wind turbine blades and the energy production for iced and clean blades. The predicted ice shapes of the various airfoil profiles are validated with the experimental data and it is shown that the tool developed is promising to be used in the prediction of power production losses of wind turbines.
SAE Technical Paper Series, 2015