Uğur Yücel | Pamukkale University (original) (raw)

Papers by Uğur Yücel

Journal of Language and Linguistic Studies, 2011

An analytical method for calculating the stiffness and damping coefficients for journal bearings ... more An analytical method for calculating the stiffness and damping coefficients for journal bearings is briefly reviewed with author's contributions. These coefficients are required for stability calculations of rotor-bearing systems. The Reynolds equation governing the pressure field within a bearing is obtained by simplifying the Navier-Stokes equations in Cartesian coordinates. It is then solved analytically using the short bearing approximation to obtain pressures in the fluid film. Integration of the pressure obtained by the solution of the Reynolds equation defines the bearing forces and the corresponding dynamic stiffness and damping coefficients of short circular bearings. The results presented in this work can be used in the stability calculations of rotor systems with short circular bearings.

Journal of Engineering for Gas Turbines and Power, 2000

Labyrinth seals are commonly found in turbines and compressors. Their objective is to control gas... more Labyrinth seals are commonly found in turbines and compressors. Their objective is to control gas leakage from high pressure regions to low pressure regions. The correct prediction and control of this leakage is crucial for the efficient and economic operation of turbomachinery. In this paper we present approaches for obtaining the above prediction in a simple analytical and explicit method. Both constant and pressure dependent flow coefficients are incorporated in the present study which extends to the higher inlet/outlet pressure differences. The results obtained with our methods compare favorably with the ones obtained by both numerical and experimental techniques. In many cases there is hardly a distinction between our results and the numerical prediction.

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In various industrial applications there is a need for higher speed, yet reliably operating rotat... more In various industrial applications there is a need for higher speed, yet reliably operating rotating machinery. A key factor in achieving this type of machinery continues to be the ability to accurately predict the dynamic response and stability of a rotor-bearing system. This paper introduces and explains the nature of rotordynamic phenomena from comparatively simple analytic models. Starting with the most simple rotor model that is supported in two rigid bearings at its ends, the more realistic and more involved cases are considered by incorporating the effects of flexible bearings. Knowledge of these phenomena is fundamental to an understanding of the behavior of complex models, which corresponds to the real rotors of turbomachines.

In this paper, an efficient technique based on the Chebyshev polynomial expansions for computing ... more In this paper, an efficient technique based on the Chebyshev polynomial expansions for computing the eigenvalues of second- and fourth-order Sturm–Liouville boundary value problems is proposed. This technique reduces the given Sturm–Liouville problem to an integral equation. The resulting integral equation is then transformed into the eigenvalue equation by calculating the integrals at the grid points using the Chebyshev expansions. Thus, the required eigenvalues of the given problem are obtained by solving this eigenvalue equation. The excellent performance of this scheme is illustrated through some numerical examples, and comparison with other methods is presented.

Applied Mathematical Modelling, 2012

European Physical Journal-applied Physics, 2011

In this paper, a new model is proposed for the heat transfer characteristics of power law non- Ne... more In this paper, a new model is proposed for the heat transfer characteristics of power law non- Newtonian fluids. The effects of power law viscosity on temperature field were taken into account by assuming that the temperature field is similar to the velocity field with modified Fourier's law of heat conduction for power law fluid media. The solutions obtained by

Thesis (Ph. D.)--Lehigh University, 2000. Includes bibliographical references (leaves 182-186). I... more Thesis (Ph. D.)--Lehigh University, 2000. Includes bibliographical references (leaves 182-186). Includes vita.

In this study, the main features of the Boubaker Polynomials Expansion Scheme (BPES) are outlined... more In this study, the main features of the Boubaker Polynomials Expansion Scheme (BPES) are outlined on the basis of published, compared and confirmed solution to differently established applied-physics nonlinear problems. Some new applications of the same scheme in the field of fluids motion and waves dynamics are also discussed.

Cogent Mathematics, 2015

Abstract In this paper, an efficient technique based on the Chebyshev polynomial expansions for c... more Abstract In this paper, an efficient technique based on the Chebyshev polynomial expansions for computing the eigenvalues of second- and fourth-order Sturm–Liouville boundary value problems is proposed. This technique reduces the given Sturm–Liouville problem to an integral equation. The resulting integral equation is then transformed into the eigenvalue equation by calculating the integrals at the grid points using the Chebyshev expansions. Thus, the required eigenvalues of the given problem are obtained by solving this eigenvalue equation. The excellent performance of this scheme is illustrated through some numerical examples, and comparison with other methods is presented.

Pressure measurements in flows of highly viscous and elastic fluids are of practical importance i... more Pressure measurements in flows of highly viscous and elastic fluids are of practical importance in many manufacturing processes. Problems may arise during such pressure measurements, since high fluid viscosity and elasticity result in excessive dynamic response time of the pressure measuring systems as well as in some distortion. This is true for systems that consist of manometers as well as

Volume 8: Mechanics of Solids, Structures and Fluids, 2012

ISRN Optics, 2012

The effects of stacking sequences of composite laminated optical beams on free vibration frequenc... more The effects of stacking sequences of composite laminated optical beams on free vibration frequencies are investigated using two methods: the Boubaker Polynomials Expansion Scheme (pbes) and the Differential Quadrature Method (dqm). In the last decades, these two techniques have been separately performed for obtaining accurate numerical solutions to several initial boundary value problems (Vo et al. 2010, Li et al. 2008, Chen 2003, Hu et al. 2008, Karami et al. 2003, Malekzadeh et al. 2004, Khare et al. 2004, Della and Shu 2005, Ramtekkar et al. 2002, Adam 2003). Conjointly yielded results are compared and discussed.