Browsing by Author "Teksin, Suleyman"

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Comparison of Flow Structures in the Downstream Region of a Cylinder With Flexible Strip
(E D P Sciences, 2015) Teksin, Suleyman; Yayla, Sedat
The present study investigates the details of flow structure to downstream of a circular cylinder mounted on a flat surface, in successive plan-view plane both in the boundary layer and up level region. The behavior of the flow in the wake of the bare cylinder and attached a flexible strip which has a 1400 N/mm2 modulus of elasticity vinyl PVC transperent film. The length of strip 240 mm (L/D=4) is investigated using Particle Image Velocimetry (PIV) technique for Reynolds numbers based on the cylinder diameter of 2500. The flow data downstream of the cylinder are presented using time-averaged velocity vector map, V-avg, streamline patterns, psi(avg), vorticity contours, omega(avg), and Reynolds stress correlations, u'u'(avg), v'v'(avg), u'v'(avg) and rms velocity values. The locations of the peak values of Reynolds stress correlations and other data are also presented in both bare cylinder and attached body in order to determine the regions under high fluctuations. Another L/D ratios will be investigated in other experiments.
Control of Flow Structures Around a Cylinder in Deep Water Employing a Passive Control Element
(Iop Publishing Ltd, 2019) Yayla, Sedat; Teksin, Suleyman; Sahin, Besir
This study aimed to experimentally investigate the swirling flow characteristic in the periphery of a cylinder located vertically in a deep water channel using a particle image velocity measurement method (PIV). In addition to the PIV method, paint visualization experiments were performed to observe the structures of vortical flow qualitatively. Based on the cylinder diameter, Reynolds numbers were changed incrementally as 2.5 x 10(3), 5 x 10(3), and 7.5 x 10(3), while the length of the control element, L = 180 mm was kept constant. The flexible splitter plate made of a plastic material was easily deformed under the influence of vortical flow. In the horizontal plane, taken from the middleheight of the cylinder, instantaneous flow data was measured first. Along these measurements, the distributions and magnitude of the velocity vectors, < V >, vorticity concentrations, , patterns of streamlines, , root mean square of velocity component such as < urms > and < vrms >, correlations of shear stresses, < u'u'>, < v'v'> and < u'v'>, turbulent kinetic energy, TKE, and spectral analysis is conducted to define the frequency, f of vortex formations. The presence of a flexible flow control element located along the central axis line of the cylinder significantly affects the vortex formations. The existence of the flexible flow control element can significantly influence the wake flow region. Furthermore, many of the value of flow characteristics decreased as mentioned with respect to the bare case.
Effects of Flexible Plate Attached To the Rear of the Cylinder on Flow Structure
(Korean Soc Mechanical Engineers, 2017) Teksin, Suleyman; Yayla, Sedat
In this experimental study, the flow structure in the wake flow region was investigated with the Particle image velocimetry technique (PIV) by attaching elastic plates at different lengths behind the cylinder. The flow structure occurred at the wake flow region altered depending on the length of the flexible matter. In this experiment, the strips with the lengths of 75, 90, 120, 135 and 180 mm were used to control instabilities. Diameter of the cylinder (D) is 60 mm and the water height (h(w)) is 600 mm. Reynolds number was kept constant as 5000 based on cylinder diameter. The images were captured at mid-height of the cylinder (h(m)) which is 250 mm. As a result of experimental studies, attached flexible strip suppressed vortex shedding occurred in the behind of the cylinder and it is observed that effect of the length flexible of the strip is pretty much. Maximum level of flow characteristics such as Reynolds stress, fluctuation velocities and turbulent kinetic energy were decreased with flexible splitter plate and shifted through the downstream region.
Flow Measurement Around a Cylindrical Body by Attaching Flexible Plate: a Piv Approach
(Elsevier Sci Ltd, 2018) Yayla, Sedat; Teksin, Suleyman
In this study, flow structures and downstream wake behind a flexible splitter plate attached to a circular cylinder have been qualitatively and quantitatively investigated at three different Reynolds numbers of 2500, 5000 and 7500. The Particle Image Velocimetry (PIV) technique was implemented to examine the flow field downstream of the bluff body in deep water. Laser sheet illuminated the region 5 mm below the top of the cylinder. All results were compared with a bare cylinder case to analyze differences in flow characteristics. Time-averaged velocity vector field < V > , vorticity contours < omega > , turbulent kinetic energy, TKE, rms of streamwise, u(rms), transverse, v(rms), velocity components were acquired and also frequency, f of vortex shedding was carried out using single point spectral analysis from PIV data to indicate flow structures. It was observed that the flexible splitter plate had a considerable effect on vortex shedding and fluctuations were prominently weakened by the use of control material.
Investigation of Effect of Boundary Layer on Flow Structure Around a Cylinder With a Strip
(E D P Sciences, 2015) Yayla, Sedat; Teksin, Suleyman
In this study, the flow characteristic of the circular cylinder was placed vertically in channel which has dimensions as 8000 mm, 1000 mm, 750 mm, lenght, width and height repectively, was investigated. The cylinder was located in boundary layer with a diameter of 60 mm (D) and a elastic stripwhich has a 1400 N/mm(2) modulus of elasticity vinyl PVC transperent film was attached behind the cylinder. Lenght of the strip (L) was 240 mm L/D=4. The Reynolds number was fixed at Re=7500. The time-averaged and instantaneous velocity vector maps, vorticity contours, Reynold shear and normal stresses, turbulent kinetic energy and frequency of shedding were obtained using the particle image velocimetry (PIV) technique. It was found that the elastic plate which exists behind the cylinder has a slight influence on the flow structure of the wake-boundary layer interaction. Values of turbulent kinetic energy, streamwise Reynold stress, transverse Reynold stresses were decreased by attaching strip.
Performance Analysis of Savonius Wind Turbines in Different Models
(Sage Publications Ltd, 2022) Simsek, Ayse; Teksin, Suleyman; Akansu, Selahaddin Orhan; Akansu, Yahya Erkan
This study presents experimental results of power performance characterizations for of 12 different Savonius turbine blades. There are three different models and the numbers of each blade types have been selected as 2, 3, 4, and 5. Three different blade types are drawn in a CAD program and all blade models are produced from 3D printer. The experiments are carried out in the subsonic wind tunnel laboratory of the Faculty of Aeronautics and Astronautics at Erciyes University. The wind tunnel has 15 kW motor power to produce wind flow. Test zone inlet and outlet section is 0.57 m x 0.57 m and 0.59 m x 0.59 m respectively. Shaft to shaft type torque meter is mounted between turbine and electric motor. Measurements have been made at wind speeds between 1 and 30 m/s. The performance values of each turbine have been measured. While the 3-bladed turbine showed the highest power coefficient values in the whole study, the maximum value was obtained from the modified helical turbine type.