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    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, Serter
    This 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.
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    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, Besir
    In 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.