Yazar "Akbiyik, Hurrem" seçeneğine göre listele

Listeleniyor 1 - 3 / 3
  • [ X ]
    Öğe
    An experimental investigation on the flow control of the partially stepped NACA0012 airfoil at low Reynolds numbers
    (Pergamon-Elsevier Science Ltd, 2024) Seyhan, Mehmet; Akbiyik, Hurrem
    An experimental study of flow control around a NACA0012 airfoil modified with fully and partially step geometry was conducted at Reynolds numbers of 6 x 104 and 1.2 x 105. Partially step geometries, the location of the step on the airfoil, and Reynolds number are varied to show their effect on aerodynamic performance and flow structures on the airfoil. Experimental results show that fully and partially step geometries are effective for flow control around the airfoil and aerodynamic performance enhancement. The maximum increase in lift coefficient is approximately 46%, and the stall angle is shifted about 1 degrees by the SM4 model at Re of 6x104 while the step geometry is on the pressure side. For a Reynolds number of 1.2 x 105, the highest increase in the lift-to-drag ratio of the airfoil is observed about 17.1 at an angle of attack of 6 degrees by the SM2 model when step geometry is placed on the pressure side of the airfoil. In the event of partially or fully stepped at the pressure side of the model, step flow structures, including the reattachment line, recirculation zone, and corner eddy, are obtained. However, even though the step geometry is at the suction surface of the model, the formation of a laminar to turbulent transition is observed. The overall results suggest that the partially stepped geometry length, Reynolds number, and step location side on the airfoil have an important role in flow control to improve aerodynamic performance for various angles of attack.
  • [ X ]
    Öğe
    Low-cost saw/sinus-tooth-shaped circular microstrip patch antenna for in-space and satellite applications
    (Iop Publishing Ltd, 2024) Aydin, Emine Avsar; Akbiyik, Hurrem
    Antennas operating in S and C bands are crucial in space satellite applications due to their high bandwidth, which facilitates the swift transmission of large data volumes from space vehicles to Earth. These bands are less affected by atmospheric disturbances and exhibit lower noise levels, ensuring uninterrupted and reliable communication between spacecraft and Earth centers. They are essential for satellite-based remote sensing, analyzing surface properties, transmitting high-resolution images, scientific data, and other information. Additionally, they are used for spacecraft control and navigation, enabling precise mission operations. This study emphasizes user-friendly production antennas with different geometries and distinct feeding techniques, demonstrating various design implementations using CST Microwave Studio software. Innovative manufacturing methods such as 3D printing PLA substrates and using copper tape for antenna elements were explored to optimize costs and production processes. Precise cutting of antenna radiation geometries was achieved using the Cricut machine. Experimental validation through reflection coefficient (S11) measurements with a handheld vector network analyzer confirmed the practical application of theoretical foundations. The study's novelty lies in examining unconventional materials like PLA filament for antenna substrates, exploring fractalization theory for enhancing bandwidth, and discussing advancements in material science with flexible filaments like TPU. These contributions offer insights into user-friendly antenna production, innovative manufacturing techniques, and theoretical explorations in antenna design, enhancing the efficiency and effectiveness of space satellite communication systems.
  • [ X ]
    Öğe
    The effect of leading-edge tubercle on a tapered swept-back SD7032 airfoil at a low Reynolds number
    (Pergamon-Elsevier Science Ltd, 2022) Seyhan, Mehmet; Akbiyik, Hurrem; Sarioglu, Mustafa; Kececioglu, Sevda Ceren
    An experimental study is performed to research the effect of the implemented leading-edge tubercles on the tapered swept-back SD7032 airfoil at Re of 5.5 x 104 and 1.1 x 105. In this study, along with a baseline model with no tubercles (T0), in total four different configurations are used for analysis of the aerodynamic charac-teristics. In the other three models (T1, T2, T3) mainly different amplitude and wavelength modulations are studied. In all experimental studies, force measurements are performed by using a six-axis load cell force measurement device. To achieve detailed information on the flow field of all models, surface oil flow visuali-zation technique is used for visualization purposes at Re = 1.1 x 105. The geometric specifications of the model are the sweep angle of 300, the tip chord of 37.5 mm, the root chord of 112.5 mm, and the span of 300 mm. Airfoil models with the LE tubercles significantly improve lift curve at almost all AoAs as compared to the baseline model. The streamwise vortices are positioned together more closely leading to interaction with each other. Consequently, these interactions lead to an increase in turbulence. This increase in turbulence may lead to a better mixing and increase in momentum exchange in the boundary layer. Amongst the models (T1-T3), the best airfoil model is determined as T3, having a1 = 0.06c, lambda 1 = 0.5c, a2 = 0.015c, and lambda 2 = 0.125c parameters, in terms of lift, drag and CL/CD ratios.