Browsing by Author "Sahin, B."

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The Effect of Angle of Attack on the Flow Structure Over the Nonslender Lambda Wing
(2013) Yayla, S.; Canpolat, C.; Sahin, B.; Akilli, H.
The aim of the current study at first stage is to demonstrate the general flow structure qualitatively using the dye visualization technique. Secondly, the instantaneous flow data taken by a Stereoscopic Particle Image Velocimetry (stereo-PIV) over a stationary nonslender lambda wing is used to determine the time-averaged flow topology in order to provide detailed information about crucial events like formation of leading edge vortices and vortex breakdown in plan-view planes and cross-flow planes. The flow structure close to the lambda wing surface and development of the vortex breakdown are investigated as functions of angles of attack within the range of 7°≤α≤17°. Experimental analyses are composed of time-averaged patterns of streamlines, vorticity contours, transverse and streamwise velocity components, Reynolds-stress correlations, distribution of fluctuating velocities, and turbulent kinetic energy. Results show that the angle of attack has a substantial influence on the flow behavior on the nonslender lambda wing surface. © 2012 Elsevier Masson SAS. All rights reserved.
Effects of Perturbation on the Flow Over Nonslender Delta Wings
(American Institute of Aeronautics and Astronautics Inc, AIAA, 2015) Canpolat, C.; Sahin, B.; Yayla, S.; Akilli, H.
An experimental investigation is presented to reveal the flow physics and turbulence statistics of nonslender delta and diamond wings with a sweep angle of Λ = 40° under perturbation condition with the amplitude of Δα = +Δαsinωet = ±0.5° during Te=2π/ωe= 0.5s. The experiments are carried out using the techniques of dye visualization and Stereoscopic Particle Image Velocimetry (stereo-PIV) on the plan view and cross flow plane for the cases of stationary and perturbed wing as the angle of attack is varied within 7°≤α≤17°. In order to perform a comparison based on the wing planform, diamond wing is designed from the composition of same shape of the delta wing and an attachment part mounted on its trailing edge. This study also provides information about effects of trailing edge attachment mounted on a generic nonslender delta wing under current test conditions. It can be concluded that perturbation is beneficial in the control of flow over both wings at relatively high angles of attack, α.The duration required for occurrence of flow control increases for the current period and time of perturbation, when the trailing edge attachment (diamond wing case) is employed. Beyond this, trailing edge attachment takes role in attenuation of turbulence statistics, where leading edge vortex breaks down. © 2015, American Institute of Aeronautics and Astronautics, Inc.
Effects of Trailing-Edge Attachment on the Flow Structure Over a Generic Delta Wing
(Asce-amer Soc Civil Engineers, 2017) Canpolat, C.; Yayla, S.; Sahin, B.; Akilli, H.
The objective of this work is to reveal the significance of a trailing-edge attachment on the flow structure over a generic nonslender delta wing using the dye visualization technique on the top-view plane. Instantaneous images are acquired by stereoscopic particle image velocimetry (stereo-PIV) to calculate time-averaged flow data, with angle of attack, a, and yaw angle,., are varied within 7 degrees <= alpha <= 17 degrees and 0 degrees <= theta <= 15 degrees, respectively. It is shown that time-mean locations of vortex breakdown for the nonslender delta and lambda wings occur in the field close to the wings. As a result, no remarkable alteration is observed for the spatial locations of the vortex breakdown. The experiments also show that the., which is a crucial parameter, alters the flow structure over the nonslender delta wing substantially compared with the lambda wing. It is concluded that the trailing-edge attachment plays vital role when. becomes effective. (C) 2017 American Society of Civil Engineers.
On Ev-Degree and Ve-Degree Topological Indices
(Univ Kashan, Fac Mathematical Sciences, 2018) Sahin, B.; Ediz, S.
Recently two new degree concepts have been defined in graph theory: ev-degree and ve-degree. Also the ev-degree and ve-degree Zagreb and Randie indices have been defined very recently as parallel of the classical definitions of Zagreb and Randie indices. It was shown that ev-degree and ve-degree topological indices can be used as possible tools in QSPR researches [2]. In this paper, we define the ve-degree and ev-degree Narumi-Katayama indices, investigate the predicting power of these novel indices and extremal graphs with respect to these novel topological indices. Also we give some basic mathematical properties of ev-degree and ve-degree Narumi-Katayama and Zagreb indices. (C) 2018 University of Kashan Press. All rights reserved