Yazar "Sahin, Besir" seçeneğine göre listele
Listeleniyor 1 - 8 / 8
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe ANN approaches for the prediction of bridge backwater using both field and experimental data(Taylor & Francis Ltd, 2011) Pinar, Engin; Seckin, Galip; Sahin, Besir; Akilli, Huseyin; Cobaner, Murat; Canpolat, Cetin; Atabay, SerterThis paper presents the findings of laboratory model testing of arched bridge constrictions in a rectangular open-channel flume whose bed slope was fixed at zero. Four different types of arched bridge models, namely single-opening semi-circular arch, multiple-opening semi-circular arch, single-opening elliptic arch, and multiple-opening elliptic arch, were used in the testing program. The normal crossing (phi = 0) and five different skew angles (phi = 10 degrees, 20 degrees, 30 degrees, 40 degrees, and 50 degrees) were tested for each type of arched bridge model. Recently, a major coverage of backwater field data obtained from the medieval arched bridge constrictions was published by the Hydraulic Research Wallingford in the UK (Brown, P. M., 1985. Hydraulics of bridge waterways: Interium report. Wallingford, UK: Hydraulic Research Wallingford, Report SR 60; Brown, P. M., 1987. Afflux at arch bridges: second interium report. Wallingford, UK: Hydraulic Research Wallingford, Report SR 115; Brown, P. M., 1988. Afflux at arch bridges. Wallingford, UK: Hydraulic Research Wallingford, Report SR 182). These data were also used in the analysis. The main aim of this study is to develop a suitable model for estimating backwater through arched bridge constrictions with normal and skewed crossings using both experimental and field data. Therefore, different artificial intelligence approaches, namely multi-layer perceptron (MLP), radial basis neural network (RBNN), generalized regression neural network (GRNN), and multi-linear and multi-nonlinear regression models, MLR and MNLR, respectively were used. The comparison between these developed models and one of the most commonly used traditional methods (Biery, P.F. and Delleur, J.W., 1962. Hydraulics of single span arch bridge constrictions. ASCE Journal of the Hydraulics Division, 88, 75-108) has been made. The test results showed that the MLP model gave highly accurate results than those of Biery and Delleur, MLR, MNLR, and GRNN and gave similar results with the RBNN model when applied to both field and experimental data.Öğe Artificial neural network approaches for prediction of backwater through arched bridge constrictions(Elsevier Sci Ltd, 2010) Pinar, Engin; Paydas, Kamil; Seckin, Galip; Akilli, Huseyin; Sahin, Besir; Cobaner, Murat; Kocaman, SelahattinThis paper presents the findings of laboratory model testing of arched bridge constrictions in a rectangular open channel flume whose bed slope was fixed at zero. Four different types of arched bridge models, namely single opening semi-circular arch (SOSC), multiple opening semi-circular arch (MOSC), single opening elliptic arch (SOE), and multiple opening elliptic arch (MOE), were used in the testing program. The normal crossing (phi = 0), and five different skew angles (phi = 10 degrees, 20 degrees, 30 degrees, 40 degrees, and 50 degrees) were tested for each type of arched bridge model. The main aim of this study is to develop a suitable model for estimating backwater through arched bridge constrictions with normal and skewed crossings. Therefore, different artificial neural network approaches, namely multi-layer perceptron (MLP), radial basis neural network (RBNN), generalized regression neural network (GRNN), and multi-linear and multi-nonlinear regression models, MLR and MNLR, respectively were used. Results of these experimental studies were compared with those obtained by the MLP, RBNN, GRNN, MILK and MNLR approaches. The MLP produced more accurate predictions than those of the others. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.Öğe Behaviour of flow at the junction of cylinder and base plate in deep water(Elsevier Sci Ltd, 2009) Sahin, Besir; Ozturk, N. AdilThe present study aims at looking into the nature of the horseshoe vortex system and its interaction with the wake-flow region in the base of circular cylinder mounted on a base plate in deep water. These kinds of flows have been attracting considerable attention due to its importance in engineering applications. Flow fields in plan and side-view planes were visualized using a laser based particle image velocimetry to examine the flow structure quantitatively for the range of Reynolds number 1500 <= Re-d <= 9600. The analysis of the cinema of instantaneous flow data, time-averaged velocity vectors map, streamlines, vorticity patterns, Reynolds stress correlations and fluctuations of the velocity components clearly demonstrate that the flow structure occurred in the base of the cylinder is three dimensional. The area of flow field occupied and affected by the horseshoe vortex system around the cylinder varies as a function of Reynolds number. This horseshoe vortex system emanating from the upstream of the cylinder swirls while travelling in the main flow direction. Counter-clockwise rotating vortices take place downstream of the cylinder in vertical plan-view plane. These swirling and rotating vortices in the junction region of the plate and cylinder cause scour mechanisms. Horseshoe vortices magnify the entrainment process and circulatory motions between the main and wake-flow regions downstream of the cylinder which stimulate the scour mechanisms. (C) 2008 Elsevier Ltd. All rights reserved.Öğe Flow details of a circular cylinder mounted on a flat plate(Int Assoc Hydraulic Research, 2008) Ozturk, Nurhan Adil; Akkoca, Azize; Sahin, BesirThe main purpose of this study is to investigate the flow structure up- and downstream of a circular cylinder mounted on a flat surface in the boundary layer region using a Particle Image Velocimetry (PIV) technique for Reynolds numbers ranging from 750 to 9600. The interaction between the primary, incoming, and counter-clock-wise rotating vortices and the trail of the horseshoe vortices formed at the upstream base of the cylinder are quantitatively identified in terms of the instantaneous and time-averaged flow data. The entrainment is shown to be activated between the main and separated flow regions across the shear layer by interactions of opposite signed rotating vortices which are responsible for scour in the upstream region of the cylinder. The surface fluid bursts to create counter-clock-wise rotating vortices upstream of the cylinder to split the incoming clock-wise rotating vortex into an independent vortex. Since the counter-clock-wise rotating vortices are not fed continuously by the surface fluid, they gradually expand in size but lose the strength and later are swept away by the developing vortices.Öğe Horseshoe vortex studies in the passage of a model plate-fin-and-tube heat exchanger(Elsevier Science Inc, 2008) Sahin, Besir; Ozturk, Nurhan Adil; Gurlek, CahitAn experimental investigation is reported using particle image velocimetry of the flow structure in the flow through a rectangular duct containing a circular cylinder with axis normal to the flow. A duct with a narrow gap was designed to simulate a fin-tube heat exchanger containing a single circular cylinder. The time-averaged velocity vectors map, < V >, patterns of streamlines, and corresponding vorticity contours, (omega) were obtained using 490 instantaneous images. Development of the entrainment process between the main flow and wake-flow regions is magnified by a helical horseshoe vortex system emerging upstream of the cylinder. The occurrence and development of boundary layer separation and the formation of horseshoe vortices upstream of the cylinder close to both upper and lower plate surfaces and the merging of these developing horseshoe vortices into a primary horseshoe vortex system were also observed in the side-view plane for the Reynolds number range of 1500 <= Re-d <= 6150. (c) 2007 Elsevier Inc. All rights reserved.Öğe Horseshoe vortex system in the vicinity of the vertical cylinder mounted on a flat plate(Elsevier Sci Ltd, 2007) Sahin, Besir; Ozturk, N. Adil; Akilli, HuseyinThe present investigation concentrates on the flow structure around the base of the vertical cylinder mounted on a flat plate for the Reynolds number of Re = 4000. The technique of high-image density particle image velocimetry (PIV) is employed in order to obtain instantaneous representations of the unsteady flow for a specified flow field. The time history of velocity and time-averaging of PIV data, particularly near the juncture, reveal valuable information about the behaviour of the horseshoe vortex system. In the forward face of the cylinder base, three different stagnation points occur, indicating the development of three different horseshoe vortices. These vortices occasionally roll up to combine a single primary vortex. Four different measuring planes were taken across the boundary layer in order to observe the effect of these three-dimensional junction flows arising from the base of the cylinder on the flow structures downstream of the cylinder. (C) 2007 Elsevier Ltd. All rights reserved.Öğe PIV measurements of flow past a confined cylinder(2008) Ozturk, N. Adil; Akkoca, Azize; Sahin, BesirThis study investigates the flow past a confined circular cylinder built into a narrow rectangular duct with a Reynolds number range of 1,500 ? Re d ? 6,150, by employing the particle image velocimetry technique. In order to better explain the 3-D flow behaviour in the juncture regions of the lower and upper plates and the cylinder, respectively, as well as the dynamics of the horseshoe vortex system, both time-averaged and instantaneous flow data are presented for regions upstream and downstream of the cylinder. The size, intensity and interaction of the vortex systems vary substantially with the Reynolds number. Although the narrow rectangular duct with a single built-in cylinder is a geometrically symmetrical arrrangement, instantaneous flow data have revealed that the flow structures in both the lower and upper plate-cylinder junction regions are not symmetrical with respect to the centreline of the flow passage. The vortical flow structures obtained in side-view planes become dominant sometimes in the lower juncture region and sometimes in the upper juncture region in unsteady mode. © 2008 Springer-Verlag.Öğe PIV measurements of flow through normal triangular cylinder arrays in the passage of a model plate-tube heat exchanger(Elsevier Science Inc, 2016) Ozturk, N. Adil; Ozalp, Coskun; Canpolat, Cetin; Sahin, BesirIn this work, the flow behaviors of multiple circular cylinders in a staggered arrangement, located in a rectangular duct with a narrow gap are studied experimentally using laser particle image velocimetry (PIV). Each cylinder is positioned at the corner of an equilateral triangle with a pitch ratio of 2d. It is known that multiple cylinders in staggered arrangements are more efficient than in-line tube arrangements in the case of heat transfer. With this in mind, this study examines the effect of a combination of multiple cylinders on flow characteristics. The staggered arrangement of the multiple cylinders guides the flow to be in a mode of repeated growth-and-destruction of the boundary-layer. This flow phenomenon increases the disorder of the vortical flow characteristics profoundly. Since the efficiency of heat exchangers depends mainly on the hydrodynamic, this investigation focuses on the flow characterization particularly on the development of horseshoe vortices. In this regard, distributions of velocity vectors, streamlines, vorticity and Reynolds stress, turbulent kinetic energy and single point spectral analysis are used to analyze the flow characteristics in detail. (C) 2016 Elsevier Inc. All rights reserved.
