Browsing by Author "Genc, Mustafa Serdar"

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Measurements of Flow Characterization Revealing Transition to Turbulence Associated With the Partial Flexibility-Based Flow Control at Low Reynolds Number
(Springer Heidelberg, 2025) Koca, Kemal; Keskin, Sinem; Sahin, Rumeysa; Veerasamy, Dhamotharan; Genc, Mustafa Serdar
In order to comprehend the flow characteristics of both controlled and uncontrolled SD7062 wind turbine airfoils with local flexible membrane material throughout a variety of angles of attack at a Reynolds number of 1.05 x 105, an experimental investigation was conducted. The time-dependent force measurement, the hot-wire experiment with a boundary layer and glue-on probes, and the oil-flow visualization technique were all utilized in the present study to measure the flow over the airfoil and examine the laminar-turbulent transition, laminar separation bubble, and the impact of a special flow control method that uses flexibility. A comprehensive intermittency analysis by utilizing hot-wire results was employed to obtain the flow physics effects of the local flexibility the first in the literature. The key results of the experiment demonstrated that the stall was delayed from alpha = 10 degrees to 12 degrees by the local flexibility. The hot-wire results are dedicated to laminar, transitional and turbulent regions and the transition phenomena at different locations over the suction surface of the airfoil in the analysis graphs. As demonstrated by the results of the oil-flow visualization experiment, in the uncontrolled case, the laminar separation bubble formed over the airfoil at alpha = 8 degrees between x/c = 0.16 and x/c = 0.42. The use of flexible membrane material over the airfoil provided that the oscillation of this material triggered the transition to turbulence and a bypass transition, which resulted in the reattached flow.
Citation - WoS: 18
Citation - Scopus: 19
Passive Flow Control Application Using Single and Double Vortex Generator on S809 Wind Turbine Airfoil
(MDPI, 2023) Ozden, Mustafa; Genc, Mustafa Serdar; Koca, Kemal
The current study is aimed at investigating the influences of vortex generator (VG) applications mounted to the suction and pressure surfaces of the S809 wind turbine airfoil at low Reynolds number flow conditions. Both single and double VG applications were investigated to provide technological advancement in wind turbine blades by optimizing their exact positions on the surface of the airfoil. The results of the smoke-wire experiment for the uncontrolled case reveal that a laminar separation bubble formed near the trailing edge of the suction surface, and it was moved towards the leading edge as expected when the angle of attack was increased, resulting in bubble burst and leading-edge flow separation at & alpha; = 12 & DEG;. The u/U-& INFIN;, laminar kinetic energy and total fluctuation energy contours obtained from the numerical study clearly show that both the single and double VG applications produced small eddies, and those eddies in the double VG case led the flow to be reattached at the trailing edge of the suction surface and to gain more momentum by energizing. This situation was clearly supported by the results of aerodynamic force; the double VG application caused the lift coefficient to increase, resulting in an enhancement of the aerodynamic performance. A novel finding is that the VG at the pressure surface caused the flow at the wake region to gain more energy and momentum, resulting in a reattached and steadier flow condition.
Citation - WoS: 14
Citation - Scopus: 16
Investigation of the Effect of Hidden Vortex Generator-Flap Integrated Mechanism Revealed in Low Velocities on Wind Turbine Blade Flow
(Pergamon-Elsevier Science Ltd, 2023) Ozden, Mustafa; Genc, Mustafa Serdar; Koca, Kemal
In this study, the flap and vortex generator (VG) mechanisms which were employed separately in aircraft were used as integrated first in literature. In this mechanism, the flap motion triggered and activated the VGs when it was needed at low speeds. Thus, this flap mechanism eliminated the unnecessary drag force generation when VGs were not needed. Numerical simulations which were validated with experimental data were employed in the study. In the first step, the flow characteristics formed on the S809 airfoil with 4 different flap angles ( beta = 30 degrees, 20 degrees, 10 degrees, 0 degrees) were investigated without the VG. Then, those flow structures formed on the S809 airfoil with both flap and VG were examined under the same conditions. According to the results, utilizing flap and VGs together had a positive impact at low wind speeds. Moreover, due to the flap and vortex generator integrated mechanism closed up to be not unnecessary drag formation at high wind speeds, thus those structures increased further to the positive effect with the increasing wind velocity. In terms of energy output, it was shown that this novel idea provided more energy output in this study.
Citation - WoS: 1
Citation - Scopus: 1
Role of Partial Flexibility on Flow Evolution and Aerodynamic Power Efficiency Over a Turbine Blade Airfoil
(MDPI, 2024) Koca, Kemal; Genc, Mustafa Serdar
In this study, the aerodynamic performance of a cambered wind turbine airfoil with a partially flexible membrane material on its suction surface was examined experimentally across various angles of attack and Reynolds numbers. It encompassed physical explanation at the pre/post-stall regions. The results of particle image velocimetry revealed that the laminar separation bubble was diminished or even suppressed when a local flexible membrane material was employed on the suction surface of the wind turbine blade close to the leading edge. The results of the deformation measurement indicated that the membrane had a range of flow modes. This showed that the distribution of aerodynamic fluctuations due to the presence of LSB-induced vortices was reduced. This also led to a narrower wake region occurring. Aerodynamic performance improved and aerodynamic vibration significantly lowered, particularly at the post-stall zone, according to the results of the aerodynamic force measurement. In addition to the lift force, the drag force was enormously reduced, corroborating and matching well with the results of PIV and deformation measurements. Consequently, significant benefits for a turbine blade were notably observed, including aerodynamic performance enhancement, increased aerodynamic power efficiency, and reduced aerodynamic vibration.
Citation - WoS: 21
Citation - Scopus: 22
Experimental Flow Control Investigation Over Suction Surface of Turbine Blade With Local Surface Passive Oscillation
(Pergamon-Elsevier Science Ltd, 2022) Koca, Kemal; Genc, Mustafa Serdar; Veerasamy, Dhamotharan; Ozden, Mustafa
Impact of the local flexible membrane (LFM) on aerodynamic phenomena including the formation of a laminar separation bubble (LSB) and transition to turbulence was experimentally investigated over the suction surface of a Clark-Y airfoil first time in literature. The experiments such as aerodynamic force measurement, smoke-wire flow visualization and hot-film tests were carried out at the free-stream velocity of U infinity = 3.2 m/s, U infinity = 6.4 m/s, U infinity = 9.6 m/s, U infinity = 12.8 m/s, and Reynolds number based upon on the chord length was Rec = 3.5 x 104, Rec = 7.0 x 104, Rec = 1.05 x 105 and Rec = 1.4 x 105, respectively. The experimental angle of attack was set at 0 degrees = alpha <= 20 degrees. In detailed intermittency analysis by the hot-film sensor over the uncontrolled airfoil, it was seen that the LSB and transition to turbulence formed close to the trailing edge at a lower angle of attack, and it moved towards the leading edge when increasing the angle of attack simultaneously. Employing LFM on the suction surface obviously affected the progress of these flow phenomena. In the results of smoke-wire flow visualization, either the size of the laminar separation bubble (LSB) was reduced or its presence was suppressed at lower in-cidences. The aerodynamic force measurement results also supported those behaviors. In particular, at lower incidences, the negative effects of LSB were mitigated, resulting in the presence of a more stable lift curve. Additionally, it was clearly observed that utilizing LFM ensured positive effects, especially at the pre-and the post-stall regions in terms of fewer fluctuations at the CL curve, meaning that less aerodynamic vibration and noise on wind/hydro turbine could be obtained.
Citation - WoS: 10
Citation - Scopus: 11
Investigation of the Mechanical Behavior of a New Generation Wind Turbine Blade Technology
(MDPI, 2023) Ciftci, Cihan; Erdogan, Ayse; Genc, Mustafa Serdar
Wind turbine blades are one of the largest parts of wind power systems. It is a handicap that these large parts of numerous wind turbines will become scrap in the near future. To prevent this handicap, newly produced blades should be recyclable. In this study, a turbine blade, known as the new generation of turbine blade, was manufactured with reinforced carbon beams and recycled, low-density polyethylene materials. The manufacturing addressed in this study reveals two novelties: (1) it produces a heterogeneous turbine blade; and (2) it produces a recyclable blade. In addition, this study also covers mechanical tests using a digital image correlation (DIC) system and modeling investigations of the new generation blade. For the mechanical tests, displacement and strain data of both new generation and conventional commercial blades were measured by the DIC method. Instead of dealing with the modeling difficulty of the new generation blade's heterogeneity we modeled the blade structural system as a whole using the moment-curvature method as part of the finite element method. Then, the behavior of both the new generation and commercial blades at varying wind speeds and different angles of attack were compared. Consequently, the data reveal that the new generation blades performed sufficiently well compared with commercial blades regarding their stiffness.