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International Review of Mechanical Engineering - November 2007 - Papers

A Two-dimensional Numerical Simulation of Oscillating Flow Using a Pseudo Spectral Method, by H. Soufi, D. Nehari, L. Adjlout, O. Imine
Method to Smooth the 3D Surfaces of the Blades of Francis Turbine Runner, by T. Miloş
Computer Simulations of Fluid-Structure Interaction Generated by a Flat-Blade Paddle in a Vessel Tank, by Z. Driss, S. Karray, H. Kchaou, M. S. Abid
Numerical Study of Swirling Confined Non-premixed Flames with Determination of Pollutant Emissions, by A. Khelil, H. Naji, L. Loukarfi
Pareto Optimum Design of Robust PI Controllers for Systems with Parametric Uncertainty, by A. Hajiloo, N. Nariman-zadeh, A. Jamali, A. Bagheri, A. Alasti
An Analytical Model for Capacity Curves Generation and Damage Prediction of Masonry Structures, by Y. Belmouden, P. Lestuzzi
Improved Wavelet Diagnostics of Antifriction Bearings with Minimum Shannon’s Entropy and Periodicity, by J. Colin-Ocampo, J. M. Arzola-Castro, M. E. Baltazar-Lopez,D. Szwedowicz, M. A. Oliver-Salazar
Contribution to Thermo-Hydrodynamic Study of Journal Bearing Under a Stationary Load, by R. Benzeguir, D. Rezini, N. Tala Ighil, A. Bounif
An Artificial Neural Network Model for Predicting Mechanical Properties of CMn (V-Nb-Ti) Pipeline Steel in Industrial Production Conditions, by A. Guedri, S. Tlili, B. Merzoug, A. Zeghloul
Stress Triaxiality as Fracture Toughness Transferability Parameter for Notched Specimens, by O. Akourri, I. Elayachi, G. Pluvinage
Tool Wear Phenomena by Drilling of Microholes in Particle-Reinforced Al-Alloy Matrix Composites, by L. Kudla
Performance Assessment of New Brake Actuator with Magneto–Rheological Working Fluid, by Z. Kesy, A. Kesy
Effect of Surface Energy of Slit Die Wall Materials on Slippage and Appearance Surface Defects During Extrusion, by A. Mezghani, A. Ayadi
A Simplified Analytical Solution of a Two-Dimensional Stefan Problem with a Periodic Boundary Condition, by F. Yigit
Condensation of R-134a in a Multi Flow Channel Aluminum Flat Tube Condenser with Micro-Fins, by S. N. Sapali, K. C. Gaikwad, P.W. Deshmukh

International Review of Mechanical Engineering - Papers

A Two-dimensional Numerical Simulation of Oscillating Flow Using a Pseudo Spectral Method
by H. Soufi, D. Nehari, L. Adjlout, O. Imine

Abstract - In this paper, results obtained from a two-dimensional numerical investigation of oscillating flow around a circular cylinder immersed in a fluid at rest are presented. The Navier-Stokes equations governing the related flow are formulated in terms of stream function and vorticity in polar coordinates and are solved by a pseudo-spectral method of high precision. By using this approach, the velocity components, the vorticity fields and force coefficients are computed for different flow regimes according to Tatsuno & Bearman map. Good agreement is found with previously obtained experimental and numerical observations.

Keywords: Navier-Stokes equations, circular cylinder, oscillating flow, Keulegan-Carpenter number, Stokes number, Fourier spectral method.

Method to Smooth the 3D Surfaces of the Blades of Francis Turbine Runner
by T. Miloş

Abstract - Using CAD techniques to design Francis turbine runner allow a better optimization of the blade shape in the actual context of many hydro-power plant refurbishments that are equipped with runners designed 20…30 years ago. In actual conditions of calculus technique available, the number of calculus sections of the Francis turbine runner blade is between 10…20, so that for a runner having large dimensions (2…10 m, diameter) it does not offer sufficiently good precision for defining pressure and suction side of the blade.
Trough proposed method, using cubic spline functions of interpolation, we might find 4…10 more points for defining blade surfaces and the initial calculated points remain unchanged. As well it is an advantage for very precise manufacturing on machine tools with numerical control, and if the runner is monobloc of cast steel it favors exact manufacturing of the casting form.
In this way calculus of the smoothness of the blade sections on the stream surfaces can be improved, focusing computing resources to hydrodynamic optimization and afterwards geometrical smoothness of the entire domain can be made done using this method. In the paper are presented, using a concrete example, the stages, the considerations and the modalities of application of this method. The method can be applied at centrifugal pumps and axial hydraulic machines too.

Keywords: 3D surface, blade, Francis turbine runner, method, smooth, spline.

Computer Simulations of Fluid-Structure Interaction Generated by a Flat-Blade Paddle in a Vessel Tank

by Z. Driss, S. Karray, H. Kchaou, M. S. Abid

Abstract - This paper presents a coupling method between the computational fluid dynamics (CFD) code and the computational structure dynamics (CSD) code solver for computing the trim of a flexible turbine in a vessel tank. It is applied in order to predict the equilibrium of elastic blade in fluid turbulent flow. Since the fluid and the structural models differ in their formulation and discretization, an interface model has to be introduced that represents the connectivity and physical interaction between the two single domain models. The structure is represented by finite elements and the related equations are solved using CSD code. The fluid flow is described by the three-dimensional Euler equations, solved by CFD code. The resulting coupled field problem containing the fluid and the structural state equations is solved by applying a coupling algorithm. In each solution step the interface and boundary conditions are exchanged and updated.
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Keywords: Turbine, 3D modelling, Coupling partitioned algorithm, CSD, CFD, Turbulent.

Numerical Study of Swirling Confined Non-premixed Flames with Determination of Pollutant Emissions

by A. Khelil, H. Naji, L. Loukarfi

Abstract - In this paper the numerical simulation of a high swirled confined natural gas diffusion flames are studied. Several factors influencing the combustion process are examined. One of the goals is to study the influence of the turbulence models and the reaction mechanism on the prediction of the flow, temperature fields and modelling of NO_xemissions. The numerical calculation has been performed using the commercial code Fluent. The standard k-ε and RSM models are used to describe the turbulent flow. The Eddy dissipation model (6 species and 2 reactions) and a chemical equilibrium model in conjunction with (β function) PDF model (9 species and 8 reactions) are used to model the turbulence-chemistry interaction. A NO_xpost-processor has been used for predicting NO emissions from combustors. The concentration of O and OH radicals are obtained assuming the partial-equilibrium assumption and using a PDF in terms of temperature. The comparison of the numerical results with the available experimental data shows a satisfactory agreement.

Keywords: Diffusion flames, NO_x emissions, RANS-CFD, Swirling flow.

Pareto Optimum Design of Robust PI Controllers for Systems with Parametric Uncertainty

by A. Hajiloo, N. Nariman-zadeh, A. Jamali, A. Bagheri, A. Alasti

Abstract - A combined robust and reliability-based approach for the Pareto optimum design of PI controllers for systems with probabilistic uncertainty is presented. In this way, some non-dominated optimum PI controllers in the Pareto sense are found using four non-commensurable objective functions both in time and frequency domains based on stochastic behavior of a system with parametric uncertainties. Such conflicting objective functions are, namely, the probability of instability, the probability of failure to a desired time response and its variance, the probability of failure to a desired disturbance rejection and its variance, and the degree of stability from the Nyquist diagram’s percentiles. The first three objective functions have to be minimized whilst the last one to be maximized simultaneously. It is shown that multi-objective Pareto optimization of such robust PI controllers using a recently developed diversity preserving mechanism genetic algorithm unveils some very important and informative trade-offs among these objective functions. Consequently, some optimum PI controllers can be compromised and chosen from the Pareto frontiers.

Keywords: Uncertain systems, Robust control, Reliability, Optimization, Genetic algorithm, Pareto.

An Analytical Model for Capacity Curves Generation and Damage Prediction of Masonry Structures
by Y. Belmouden, P. Lestuzzi

Abstract - In this paper a planar-frame analytical model with openings is presented. The model deals with seismic analysis using the Pushover method for medium-to-short masonry buildings. Each wall with opening can be decomposed into parallel structural walls made of an assemblage of piers and a portion of spandrels. As formulated, the structural model undergoes inelastic flexural as well as inelastic shear deformations. The mathematical model is based on the smeared cracks and distributed plasticity approaches. Both zero moment location shifting in piers and in spandrels can be evaluated. The constitutive laws are modeled as bilinear curves in flexure and in shear. A biaxial interaction rule for both axial force - bending moment and axial force – shear force are considered. An event-to-event strategy is used to solve the nonlinear problem. A application was used to show the ability of the proposed model to analyze unreinforced masonry structures. Relevant findings are compared to analytical results from experimental, simplified models and finite element models using ETABS finite element package.

Keywords: Pushover analysis; Unreinforced masonry; Structural wall; Seismic evaluation.

Improved Wavelet Diagnostics of Antifriction Bearings with Minimum Shannon’s Entropy and Periodicity

by J. Colin-Ocampo, J. M. Arzola-Castro, M. E. Baltazar-Lopez,D. Szwedowicz, M. A. Oliver-Salazar

Abstract - A study of vibration signals of antifriction bearings using an improved wavelet transform analysis of frequency bands through minimum Shannon’s Entropy and Periodicity was done. Optimum shape forms of the analyzing wavelet function were obtained by using minimum Shannon Entropy providing better time-frequency localization by minimizing the energy loss between original signal and wavelet coefficients representing such a signal, thus assuring the best time-frequency resolution representation of the signal. Once the obtained signals from the bearing were analyzed by wavelet transform, they were subjected to a Single Value Decomposition method to help in the identification of vibration signals with evolution of a possible deterioration at an incipient stage and thus be able to prevent failure on bearing components.

Keywords: Antifriction bearing diagnostics, Minimum Shannon’s Entropy, Periodicity, Wavelet Analysis.

Contribution to Thermo-Hydrodynamic Study of Journal Bearing Under a Stationary Load

by R. Benzeguir, D. Rezini, N. Tala Ighil, A. Bounif

Abstract - The present work is a synthesis of some studies, realized on hydrodynamics journal bearings. The behavior of the lubricant film in the hydrodynamic contact is described by the equation of viscous thin film, also denominated the Reynolds equation. The boundaries conditions used to study the journal bearing with finite length are those of Reynolds and Elrod. A global thermal study is done in order to evaluate the effect of temperature. Direct problem (consisting in determining the load for a given position of shaft in the bearing) and the inverse problem (consisting in determining the position of the shaft in the bearing for an applied loading) of lubrication are treated. Obtained results for a finite length bearing are compared with those obtained using the theory of the short bearing. A flow chart taking in account the resolution of the problems cited above is elaborated. A computer code is realized permit the calculation and the visualization of the important parameters of a hydrodynamic contact.

Keywords: Hydrodynamic Bearing, Static load, Thermal effect, Elrod, Reynolds.

An Artificial Neural Network Model for Predicting Mechanical Properties of CMn (V-Nb-Ti) Pipeline Steel in Industrial Production Conditions
by A. Guedri, S. Tlili, B. Merzoug, A. Zeghloul

Abstract - The mechanical properties of API X60/X70 microalloyed steel were investigated with industrial thermomechanical experiments. The many parameters of processes obtained during production of the plant were systematically changed to optimise the strength and toughness properties. The optimised parameters were used for the production of the API X60/X70 steel. However, it is not easy to determine as to what parameters under which conditions influence the mechanical properties of the material. Therefore, in this study, a generalised regression neural network was developed to predict the mechanical properties as a function of experimental conditions. The predicted values of the yield and tensile strengths using the neural network are found to be in good agreement with the actual values from the experiments.

Keywords: Microalloyed steel; Mechanical properties; Artificial neural network; regression neural network.

Stress Triaxiality as Fracture Toughness Transferability Parameter for Notched Specimens
by O. Akourri, I. Elayachi, G. Pluvinage

Abstract - The problem of fracture toughness transferability is treated by using the stress triaxiality and by introduction of a new transferability parameter called p. This parameter is a combination of effective critical stress triaxiality (mean value of stress triaxiality over effective distance) and multiplies by a geometrical function. Application of this method has been made on three point bending specimens made in XC 38 steel. Comparison of 2D and 3D approaches is made.

Keywords: Transferability parameter, Stress triaxiality, Notch radius, Notch depth, Steel.

Tool Wear Phenomena by Drilling of Microholes in Particle-Reinforced Al-Alloy Matrix Composites
by L. Kudla

Abstract - Metal matrix composites (MMCs) form a new class of materials, which have very attractive functional properties but afford specified machining troubles. This problem is well seen by drilling of microholes having diameters within the range of 100...500 μm. The paper presents conditions of the drilling tests, results of the tool wear observations for selected tool materials and coatings, morphology of forming chips, influence of cutting parameters and coolants on the tool wear and on the quality of produced microholes.

Keywords: Cutting, Micro-Drilling, Composites, Tool Wear.

Performance Assessment of New Brake Actuator with Magneto–Rheological Working Fluid
by Z. Kesy, A. Kesy

Abstract - In this paper the possibility of utilizing smart fluids in a controlled brake actuator working in a printing press drive system is considered. The new actuator is created by replacing the powder with a smart fluid in a powder brake. Magnetic fluid and ferrofluid are used as smart fluids. The derivation of static and dynamic curves of the brake was undertaken on an experimental test rig. The test rig allowed measurement of the rotational speed and braking torque of a brake shaft. A comparison of the tested brake with one typically used for printing presses shows that the new brake fulfils the technical requirements and gives new possibilities for the mechanical drive braking application.

Keywords: actuator, magnetic fluids, powder brake , viscotic brake.

Effect of Surface Energy of Slit Die Wall Materials on Slippage and Appearance Surface Defects During Extrusion
by A. Mezghani, A. Ayadi

Abstract - The physical and chemical properties of a fluorinated material surface can present some varied interactions with the melted polymers during extrusion process. We have studied the flow of an eraser silicone through the two-dimensional dies of different materials wall. We have put in evidence the differences of roughness and surface energy properties in order to be able to understand and to interpret phenomena, which appear during the melted polymer flows through slit die achieved in such materials. This work will permit to understand the influence of these materials on the apparition of extrusion defects and in particular the sharkskin form. We will confirm the primordial effect of the surface energy, of the materials wall as well as the melted polymer on the phenomenon of slip and elimination of extrusion defects. This slip delays or eliminates completely the apparition of surface instabilities. This has an obvious direct impact on the industrial manufacture process.

Keywords: Extrudate defects, Fluorinated die, PDMS polymer, Slip, Surface energy.

A Simplified Analytical Solution of a Two-Dimensional Stefan Problem with a Periodic Boundary Condition
by F. Yigit

Abstract - A two-dimensional heat conduction problem with phase-change is solved by using a linear perturbation method. Temperature at the outer surface of the mold is approximately uniform, but contains a small sinusoidal perturbation in one space dimension. The problem is solved analytically with the assumption of infinitely large diffusivities of the solidified shell and mold materials. Results are obtained for the solid/melt interface as a function of time and for the temperature distributions in the shell and mold. The inverse problem, in which the solid/melt boundary is prescribed and the mold outer surface temperature is to be determined, is also discussed. The effect of process parameters such as the mold thickness, the thermal contact resistance between the shell and mold, and the thermal conductivity ratios between the shell and mold materials on the growth of the perturbation in the shell thickness and the outer temperature of the mold is investigated in detail.

Keywords: Perturbation, Phase-Change, Solidification, Stefan.

Condensation of R-134a in a Multi Flow Channel Aluminum Flat Tube Condenser with Micro-Fins
by S. N. Sapali, K. C. Gaikwad, P.W. Deshmukh

Abstract - Aluminum Multi Flow Channel Flat Tube (MFC) Condenser with micro-fins is the recent development in the field of automobile air conditioning (AC) systems. The condenser rejects heat to the atmosphere. Various correlations, based on physics of condensation process are available for determining pressure drop and heat transfer coefficients. Efforts are made to measure pressure drop and heat transfer coefficient by experimental as well as analytical methods. In order to study the behavior of MFC tube condenser, for an automobile AC unit, using R-134a as a working medium, and for developing heat transfer coefficient correlations for the same, a project work is undertaken. The available correlations to determine heat transfer coefficient for the MFC geometry are studied and Yang & Webb (1997) correlation is found to be the best fit for the job. Such correlations are being tested for the boundary conditions of interest and the results are discussed in this paper.

Keywords: Heat transfer, R-134a, Condensation, Two-phase flow.

International Review of Mechanical Engineering - November 2007 - Papers

Computer Simulations of Fluid-Structure Interaction Generated by a Flat-Blade Paddle in a Vessel Tank

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