Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Conference Object A Numerical Study on the Determination of the Effects of Pore To Throat Size Ratio on the Thermal Dispersion in Porous Media(Begell House, 2014) Özgümüş, Türküler; Mobedi, Moghtada; Özkol, ÜnverDirect pore-level numerical simulations are widely used to estimate macroscopic properties of fluid flow and heat transfer in porous media. Thermal dispersion is one of the most important macroscopic transport parameters for analyzing convective heat transfer in a porous medium. It should be known in order to predict the macroscopic temperature distribution. In the present study, a microscopic scale analysis is performed for a porous medium with periodic structure. A representative elementary volume is chosen from an infinite medium consists of rectangular rods in inline arrangement. The continuity and momentum equations are solved to obtain flow field and the energy equations for fluid and solid phases are solved to obtain microscopic temperature distributions in two phases. There are velocity and temperature deviations between macroscopic and microscopic local values. Volume averaging method is applied to the computed deviations and thermal dispersion conductivity of porous media is determined. The aim of this study is to analyze the effects of pore to throat size ratio on the longitudinal and transverse thermal dispersion in porous media. The study is performed for representative elementary volumes with different pore to throat size ratios and Reynolds numbers from 1 to 100. The study is performed for high porosity porous media (ε = 0.7 and 0.91). It is shown that the porosity and pore to throat size ratio have more influence on the transverse rather than longitudinal thermal dispersion. © 2014, Begell House Inc. All rights reserved.Conference Object Citation - WoS: 1Citation - Scopus: 1Development of a New Universal Inverse Through-Flow Program and Method for Fully Coupled Split-Flow Turbomachinery Systems(The American Society of Mechanical Engineers(ASME), 2015) Acarer, Sercan; Özkol, ÜnverStreamline curvature technique for inverse through-flow modeling of turbomachinery is still one of the most prevalent alternatives in design. Even though the subject has been studied in numerous aspects over many years, open literature on fully coupled split-flow turbomachinery system design which is encountered in turbofan engines, is still limited. The principal method, viable for analysis mode, may easily give rise to undesired streamline distortion near the splitter leading edge whilst operating in design mode. Besides, spanwise discontinuity of flow properties along the stagnation streamline prior to final solution convergence may be another outcome. The present study is geared towards eliminating these potential drawbacks by developing an alternative generally applicable split-flow scheme incorporated in a recently developed streamline curvature software. This new scheme disposes the need to define a stagnation streamline, while preserving full coupling between the main and split ducts. This is achieved through removal of by-pass ratio restriction, which makes local velocity vector always perfectly aligned with the splitter leading edge without any limit on fan-splitter axial distance. A two-step validation strategy is followed: Firstly, 2D split-flow solutions of the developed method for representative duct geometries having design by-pass ratios ranging between 0.25 and 6.5, but without turbomachinery, are compared with a commercial CFD software; Secondly, the method is compared with 3D viscous CFD solution of NASA Rotor 37 geometry, whose flowpath is modified to include a downstream flowpath splitter. It is shown that the proposed scheme can be used as a practical alternative to the conventional treatment that promises minimal effort to implement to an existing compressor streamline curvature methodology.Article Citation - WoS: 1Citation - Scopus: 2Off-Design Analysis of Transonic Bypass Fan Systems Using Streamline Curvature Through-Flow Method(Walter de Gruyter GmbH, 2019) Acarer, Sercan; Özkol, ÜnverThe two-dimensional streamline curvature through-flow modeling of turbomachinery is still a key element for turbomachinery preliminary analysis. Basically, axisymmetric swirling flow field is solved numerically. The effects of blades are imposed as sources of swirl, work input/output and entropy generation. Although the topic is studied vastly in the literature for compressors and turbines, combined modeling of the transonic fan and the downstream splitter of turbofan engine configuration, to the authors' best knowledge, is limited. In a prior study, the authors presented a new method for bypass fan modeling for inverse design calculations. Moreover, new set of practical empirical correlations are calibrated and validated. This paper is an extension of this study to rapid off-design analysis of transonic by-pass fan systems. The methodology is validated by two test cases: NASA 2-stage fan and GE-NASA bypass fan case. The proposed methodology is a simple extension for streamline curvature method and can be applied to existing compressor methodologies with minimum numerical effort.Conference Object Computational Determination of Volume Averaged Transport Properties of Heat and Fluid Flow in Porous Media by Using Microtomography Images(Begell House, 2017) Çelik, Hasan; Mobedi, Moghtada; Nakayama, Akira; Özkol, ÜnverIn this study, the theory and techniques for obtaining VAM (Volume Average Theory) transport properties of a porous medium from micro-tomography images are described. The validation of the results with reported experimental or numerical values in literature may not be sufficient, hence a comprehensive attention is paid to the techniques that can be used for verification of the obtained numerical results at each step of this long computational process. The suggested verification techniques are categorized and explained in details. © 2017, Begell House Inc. All Rights Reserved.