Yazar "Akbiyik, Hurrem" seçeneğine göre listele

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    A Study on the Plasma Actuator Electrode Geometry Configurations for Improvement of the Aerodynamic Performance of an Airfoil
    (Assoc Mechanical Engineers Technicians Slovenia, 2018) Akbiyik, Hurrem; Yavuz, Hakan; Akansu, Yahya Erkan
    In this study, the induced flow effects of plasma generated by various types of electrode geometry configurations are presented. The model chosen for the study is a NACA0015 airfoil. The experiments are conducted in a wind tunnel at Reynolds number of 4.8x10(4). The plasma actuators mounted on the leading edge of the airfoil at chord position of 0.1 (x/C). The plasma actuators consist of an embedded and exposed electrode between which a dielectric material is placed. The applied voltage is set to 7 kV(pp). The excitation frequency is also set to 3.5 kHz. Three different electrode geometry configurations, namely as rinear, saw-tooth and square, are considered for the study. As a part of the experimental study, the two dimensional and three dimensional flow structures generated by the plasma actuators and related analysis results are presented. In addition, necessary measurements are also made to determine the drag and lift forces.
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    Active control of flow around a circular cylinder by using intermittent DBD plasma actuators
    (ELSEVIER SCI LTD, 2017) Akbiyik, Hurrem; Akansu, Yahya Erkan; Yavuz, Hakan
    In this study, for active control of flow, the effect of the Dielectric Barrier Discharge (DBD) plasma actuator consisting of intermittent electrodes in the lengthwise direction of circular cylinder is investigated. The experiments were conducted in the wind tunnel at the Reynolds numbers between 6000 and 12,500. In three different cases, the lengths of the actuators and gaps between them are chosen as 20 mm, 25 mm, and 50 mm, respectively. The applied voltage is in the range of 4.5-7.5 kVpp and the constantly applied frequency is 3.5 kHz for producing the plasma. By using the equally placed DBD plasma actuators for the circular cylinder, 2 dimensional flow structure in the wake region is converted into 3-dimensional flow structure that leads to reduce in the mean and fluctuating forces acting on the cylinder. The wake region is narrower than the plain cylinder at the middle point of the electrode spanwise position and the width of the wake region increases at the end point of the electrode spanwise position.
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    Aerodynamic and energy-efficiency-based assessment of plasma actuator's position on a NACA0015 airfoil
    (Wiley-V C H Verlag Gmbh, 2020) Akbiyik, Hurrem; Yavuz, Hakan; Akansu, Yahya E.
    In recent years, there has been an increase in the number of research papers on plasma and its use in active flow control applications. The main objective of this study is to assess the plasma actuator's position on a NACA0015 airfoil in terms of aerodynamic forces. In addition, optimization of the plasma actuator's position and its configuration are studied in order to identify the optimum configuration for improvement in lift coefficient. The experiments are conducted in an open-suction-type wind tunnel at Reynolds numbers of 48,000, 75,000, and 100,000. The plasma actuators are mounted on various positions (x/C) starting from the leading edge to trailing edge of the airfoil. The experimental results on aerodynamic force measurement are presented to illustrate the increasing lift effect of the generated plasma. It is also shown that the plasma actuators used as an active flow control device appears to shift the stall angle of the airfoil. The results of the experimental study suggest that the energy efficiency of airborne systems can be improved with the use of plasma actuators due to its increasing lift coefficient effect. This result becomes a vital finding considering that the same flight can be achieved with less fuel and less amount of environmental pollution for the same distance of journey. It is also worth mentioning that increasing lift effect would mean taking off from a shorter runway or allowing the airborne vehicle with the ability to fly with additional payload.
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    Comparison of the Linear and Spanwise-Segmented DBD Plasma Actuators on Flow Control Around a NACA0015 Airfoil
    (IEEE-Inst Electrical Electronics Engineers Inc, 2017) Akbiyik, Hurrem; Yavuz, Hakan; Akansu, Yahya Erkan
    In this paper, linear and spanwise-segmented plasma actuator implementations as well as base airfoil with no plasma cases are presented. These approaches are used to control the flow around a NACA0015 airfoil. The experiments were conducted in a wind tunnel at Reynolds number of 3.6x10(4). The plasma actuators mounted on the leading edge of the airfoil at chord position of 0.1 (x/C). The electrical parameters used for the plasma generating device are set to constant values of 6-kV(pp) applied voltage and 3.5-kHz excitation frequency. It is observed that the use of spanwise-segmented plasma actuators converts the 2-D flow structure around the airfoil into 3-D forcing flow structure. The change of the wake region width of the airfoil is visualized by using the smoke-wire method. The flow visualization is performed at attack angles of 0 degrees, 5 degrees, 10 degrees, and 15 degrees. In addition, necessary measurements are also made to determine drag and lift forces. A comparative study on the drag and lift forces for the NACA0015 airfoil is performed. As a part of the conclusions, linear and spanwise-segmented plasma actuator implementations as well as base airfoil with no plasma cases are compared and related results on flow control are presented.
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    Effect of plasma actuator and splitter plate on drag coefficient of a circular cylinder
    (E D P SCIENCES, 2016) Akbiyik, Hurrem; Akansu, Yahya Erkan; Yavuz, Hakan; Bay, Ahmet Ertugrul; Dancova, P; Vesely, M
    In this paper, an experimental study on flow control around a circular cylinder with splitter plate and plasma actuator is investigated. The study is performed in wind tunnel for Reynolds numbers at 4000 and 8000. The wake region of circular cylinder with a splitter plate is analyzed at different angles between 0 and 180 degrees. In this the study, not only plasma actuators are activated but also splitter plate is placed behind the cylinder. A couple electrodes are mounted on circular cylinder at +/- 90 degrees. Also, flow visualization is achieved by using smoke wire method. Drag coefficient of the circular cylinder with splitter plate and the plasma actuator are obtained for different angles and compared with the plain circular cylinder. While attack angle is 0 degree, drag coefficient is decreased about 20% by using the splitter plate behind the circular cylinder. However, when the plasma actuators are activated, the improvement of the drag reduction is measured to be 50%.
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    Effect of the duty cycle on the spark-plug plasma synthetic jet actuator
    (E D P SCIENCES, 2016) Seyhan, Mehmet; Akansu, Yahya Erkan; Karakaya, Fuat; Yesildag, Cihan; Akbiyik, Hurrem; Dancova, P; Vesely, M
    A promising novel actuator called Spark-Plug Plasma Synthetic Jet (SPSJ) has been developed in Atmospheric Plasma Research Laboratory at Nigde University. It generates electrothermally high synthetic jet velocity by using high voltage. SPSJ actuator can be utilized to be an active flow control device having some advantages such as no moving parts, low energy consumption and easy to integrate the system. This actuator consists of two main components: semi-surface spark plug (NGK BUHW) as an anode electrode and a cap having an orifice as a cathode electrode. The cap, having a jet exit orifice diameter of 2 mm, has diameter of 4.4 mm and height of 4.65 mm. This study presents the characteristics of SPSJ actuator by using the hot wire anemometer in order to approximately determine jet velocity in quiescent air. Peak velocity as high as 180 m/s was obtained for f(e) = 100 and duty cycle 50%. The flow visualization indicated that the actuator's jet velocity is enough to penetrate the developed boundary layer.
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    EFFECTIVE FLOW CONTROL AROUND A CIRCULAR CYLINDER BY USING BOTH A SPLITTER PLATE AND PLASMA ACTUATORS AS PASSIVE AND ACTIVE CONTROL METHODS
    (Turkish Soc Thermal Sciences Technology, 2021) Akbiyik, Hurrem; Akansu, Yahya Erkan
    In this study, passive and active flow control methods were used together to manipulate the flow around a circular cylinder. The experiments were conducted in a wind tunnel for the Reynolds number range of 4000 and 10000 based on the diameter of the circular cylinder (D). A splitter plate was used as passive flow control device and its length was chosen to be about 3.75D. Plasma actuators were placed on the circular cylinder at a position of +/- 90 degrees as an active flow control device. Combining the active and passive flow control methods, a greater reduction of the drag coefficient was achieved compared to that of the cases when using these methods separately. For Reynolds numbers of 5000 and 10000, the hybrid method gives a reduction in drag of 48% and 45%, respectively. The velocity measurements were carried out by using the hot-wire anemometry and velocity profiles were obtained in the wake region. The flow was visualized by using a smoke wire method. The results revealed that the wake region of the circular cylinder with plasma actuator and splitter plate has a narrower width than the plain cylinder and with splitter plate. Also, it can be seen from spectral analysis that the vortex shedding frequency was suppressed significantly by usage of the hybrid flow control method was used.