WSEAS Transactions on
Applied in Theoretical Mechanics

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Print ISSN: 1991-8747
E-ISSN: 2224-3429

Volume 7, 2012

Issue 1, Volume 7, January 2012

Title of the Paper: Plane Wave Based Method: Analytic Integration and Frequency Behaviour

Authors: Soufien Essahbi, Emmanuel Perrey-Debain, Mabrouk Ben Tahar, Lotfi Hammami, Mohamed Haddar

Abstract: This paper deals with 2D acoustic problem. In order to study this problem, a finite element enriched by a plane wave base is used. This work focus on two aspects. Firstly, the study of this element depending on the frequency. Secondly, the description of an analytic integration technique. Two examples are studied, the first resemble to car cavity and the second resemble to rectangular duct. A comparison between numerical results obtained by standard finite element and enriched finite element are done, for the first one. And, for the second example, a comparison between numerical results obtained by the use of enriched finite element and analytic results are presented. With this work, the results found show that the performance of the enriched finite element increases while increasing the frequency, in the same way for the analytic integration.

Keywords: Helmholtz equation, Finite elements, Plane wave basis, Frequency behaviour, Analytic integration, GAUSS integration

Title of the Paper: Algorithm of the Maintenance Activities Optimization with an Approximate Solution to the Problem of Scheduling Preventive Task

Authors: Aissam Aboussalim, Mohamed Mediouni

Abstract: Maintenance is a factor of competitivity since it affects the production, quality and cost.
It is essential for the increasing development of the company and its assets.
The approach presented in this paper is a contribution to research related to the scheduling of maintenance tasks, to the allocation of resources and to the optimization of maintenance costs. This work proposes an algorithm based on: the real-time decision, the planning of maintenance tasks, the allocation of tasks to the appropriate resources under the constraints of the tasks duration and skills, and at the same time minimizing the cost of maintenance service. The criterion for maintenance optimization is evaluated by the sum of advances / delays of preventive maintenance cost by including other tasks, dynamic or delays, in elementary windows.

Keywords: Tasks, preventive maintenance, scheduling, optimization, resource, cost

Title of the Paper: Distinguishing Profile Deviations from a Part’s Deformation Using the Maximum Normed Residual Test

Authors: Ali Aidibe, Antoine S. Tahan, Gad N. Abenhaim

Abstract: Non-rigid parts, in free-state, may have a considerable different shape than their nominal model due to dimensional and geometric variations of manufacturing process, gravity loads and residual stress induced distortion. Therefore, sorting profile deviation from a part's deformation by comparing the part's nominal shape to its scanned free-state shape is a challenging task. This task is a key step in the Iterative Displacement Inspection (IDI) algorithm used for the inspection of non-rigid parts without the use of costly specialized fixtures. This paper proposes the use of the statistical maximum normed residual test to improve the aforementioned identification task. Thirty two simulated manufactured parts are studied to show that the proposed method reduces the type I and II identification error of the IDI method.

Keywords: Rigid registration, non-rigid registration, quality control, tolerancing, inspection, metrology, non-rigid parts, deformation, Geometric dimensioning and tolerancing (GD&T)

Title of the Paper: Determination of Relaxation and Retardation Spectrum from Modulus of Complex Frequency-Domain Material Functions

Authors: Vairis Shtrauss, Aldis Kalpinsh

Abstract: The paper is devoted to improving and simplifying determination of the relaxation and retardation spectrum (RRS). A concept is postulated that determination of RRS from some specially selected material responses differing from the explicitly defined material functions, such as the real or imaginary parts of complex compliance and complex modulus, may improve the recovery performance at the price of better measurability of these specific material responses. As one of possible implementations of the postulated concept, we propose to recover RRS from the modulus (absolute value) of a complex frequency-domain (dynamic) material function, which, compared to the real or imaginary part, can be more accurately and easy acquired by measuring the amplitudes of harmonic responses of a material. It is demonstrated that RRS recovery problem from the modulus of a complex frequency-domain material function may be interpreted as a filtering task with a diffuse magnitude response bounded by the responses of the Mellin deconvolution filters corresponding to the minimum (zero) and maximum imaginary parts according to the Kramers-Kronig relation. A discrete RRS recovery filter operating with geometrically sampled data is constructed for recovering RRS from the modulus and the simulation results are presented. A measurement system is proposed implementing RRS recovery through the modulus of a complex frequency-domain material function, where a material under test is subjected to multi-harmonic excitation at geometrically spaced frequencies with subsequent measuring the amplitudes of multi-harmonic responses and processing them by a discrete RRS recovery filter.

Keywords: Relaxation and Retardation Spectrum (RRS), Modulus of a Complex Frequency-Domain Function, Complex Compliance, Complex Modulus, Mellin Deconvolution Filter, Diffuse Magnitude Response

Title of the Paper: Nonlinear Static Analysis to Assess Seismic Performance and Vulnerability of Code - Conforming RC Buildings

Authors: A. Cinitha, P. K. Umesha, Nagesh R. Iyer

Abstract: The seismic zone map of Indian subcontinent emphasis that more than 60% of land is under severe to moderate earthquake and approximate hábitat requirement is 20-25 lakhes of buildings in each year. The adequacy of post occupancy of buildings after an earthquake is highly demanded. This paper investigates seismic performance and vulnerability analysis of 4-storey and 6-storey code-conforming (IS: 456-2000, Indian standard for plain and reinforced concrete code and IS: 1893-2002, Indian standard criteria for earthquake re-sistant design of structures) reinforced concrete (RC) buildings. The buildings are designed for two different cases such as ordinary moment resisting frame (OMRF) and special moment resisting frame (SMRF). The non-linear static analysis (pushover analysis) is used to capture initial yielding and gradual progressive plastic be-haviour of elements and overall building response under seismic excitations. The deformation characteristics of structural elements are essential to simulate the plastic hinge formation in the process of generation of capacity curve during the pushover analysis. An analytical procedure is developed to evaluate the yield, plastic and ulti-mate rotation capacities of beams and columns along with different plastic hinge lengths. In the present study, user defined plastic hinge properties of beams and columns are modeled using analytical expressions developed based on Eurocode 8 and incorporated the same in pushover analysis using SAP2000. The nonlinear static analysis is carried out for load patterns proportional to fundamental mode. The analysis gives an estimate of seismic capacity of the structural system and its components based on its material characteristics and detailing of member dimensions. A 100% dead load plus 50% live load is applied prior to the lateral load in the push-over analysis. The building performances are assessed with the capacity curve generated. Performance levels are used to describe the limiting damage condition, which may be considered satisfactory for a building under specific earthquake. The performance levels are expressed in terms of target displacement, defined by limiting values of roof drift, as well as deformation of structural elements. The three performance levels considered in the present study are immediate occupancy, life safety and collapse prevention. The vulnerability of the buildings is estimated in terms of vulnerability index to assess the performance of the building.

Keywords: Post occupancy, Plastic hinge length, Seismic performance, Nonlinear static analysis, Perform-ance levels, Vulnerability index

Title of the Paper: Numerical Study of Transition Process in a Separated Boundary Layer on a Flat Plate with Two Different Leading Edges

Authors: Zhiyin Yang

Abstract: Transition from laminar flow to turbulent flow occurs very often and plays a crucial role in many practical engineering flows. There are many different kinds of transition and broadly speaking they can be classified into three categories: classical transition in attached boundary; bypass transition in attached boundary layer and separated boundary layer transition. This paper presents a comparative study of separated boundary layer transition on a flat plate with a blunt/semi-circular leading edge. Boundary layer may separate due to an adverse pressure gradient or due to flow geometry. In the current study the geometry is a flat plate with two different leading edges: a blunt one and a semi-circular one. The main purpose of the study is to identify how similar or how different the transition process is with two different leading edges. This study shows that for both cases (blunt and semi-circular leading edges) the primary two-dimensional instability originates from the free shear layer of the separation bubble via the Kelvin-Helmholtz mechanism. Three-dimensional motions develop under any small spanwise disturbances and similar coherent structures have been observed from flow visualization in both cases, strongly indicating that the transition process is very similar.

Keywords: Large-Eddy Simulation (LES), transition process, free shear layer, instability

Title of the Paper: Assisted Creative Robot Arm Assembly and Control Program Design

Authors: Meng-Hui Hsu, Ting-Sheng Weng

Abstract: Applied techniques in smart robots implicates various basic and applied courses in different fields, activities relating to education on high-tech smart robots are good methods to inspire students to become outstanding technological personnel. Thus, this study used training activities based on the creative DIY Lego robot block combination designs, and in turn, used the program design to control the robotic arm actions of Lego robots in order to cultivate student ability in understanding and applying principles of robotic movement and control. This study intended that students would apply creative, inventive abilities to solve problems, produce innovative ideas, and new design methods for games.
This study aimed to teach students to learn the basic principles of robotic movement, the writing, and design of Java code, and in turn, complete repetitive works for controlling robotic arms to pick up objects at fixed points, move them, and place them. These activities can inspire student concepts in using robots to replace human resources and related applied technologies, and is intended to educating students to engage in new beneficial research relating to robots.

Keywords: Robots, Robot arms, Creative combination, Assisted computer programming language instruction, Java

Issue 2, Volume 7, April 2012

Title of the Paper: Fuzzy-Rule-Based Faults Classification of Gearbox Tractor

Authors: Shaban Ghavami Jolandan, Hossein Mobli, Hojat Ahmadi, Mahmoud Omid, Seyed Saeid Mohtasebi

Abstract: This paper presents a fault Classification method based on a fuzzy inference system. The vibration signal from a piezoelectric transducer is captured for the following conditions of MF 285 gearbox: ‘Healthy Gearbox’ (H), ‘Gear with tooth face worn’ (W) and ‘Gear with tooth face broken’ (B), at three working speed (700, 1500 and 1800 rpm). The features of signal were extracted using descriptive statistic parameters. The output of the J48 algorithm is a decision tree that was employed to produce the crisp if-then rule and membership function sets. Results showed that the total classification accuracy for 700, 1500 and 1800 rpm conditions were about 79.63%, 100% and 96.3%.

Keywords: Vibration-Based Condition Monitoring, J48 Algorithm, Gearbox, Fuzzy, Tractor, Fault

Title of the Paper: Study of Workpiece Thermal Profile in Electrical Discharge Machining (EDM) Process

Authors: Ali Moarrefzadeh

Abstract: Electric Discharge Machining (EDM) removes metal with sparks. A shaped graphite or copper electrode is used to make a cavity that is the mirror image of the electrode, without direct contact with the workpiece. Sparks travel through a dielectric fluid, typically a light oil, at a controlled distance. EDM can machine cavities with thin walls and fine features, achieve difficult part geometry, produce burr-free parts, and is insensitive to workpiece hardness.The values of these parameters significantly affect such machining outputs as material removal rate and electrodes wear. In this paper, the mathematical relationships between input and output parameters of EDM are established using regression method and the best set of models is chosen. Genetic Algorithm is then used to optimally determine input parameters levels in order to obtain any desired set of outputs. Numerical simulation of process in ANSYS software an for gaining the thermal profile, the effect of parameter variation on temperature field and process optimization are done. The numerical results show the time-dependant distributions of arc pressure, current density, and heat transfer at the workpiece surface are different from presumed Gaussian distributions in previous models.

Keywords: EDM parameters, Workpiece, Discharge, Machining, ANSYS

Title of the Paper: Machine Tools Foundation Static and Free Vibration Analyses

Authors: Thamir Salah, Suhair G. Hussain, Wedad AlAzzawy

Abstract: Machine tools foundations are very important element of these machine structures. Deformations for foundations under static load are studied in present work, the effect of changing stiffening plates shape and cutting conditions such as type of cutting process and angle of cutting forces on these deformation are investigated using finite element program (ANSYS5.4) also effects of these parameters on the foundation natural frequencies are obtained.

Keywords: machine tools, foundations, free vibration, static analyses, structure, finite element method

Title of the Paper: Simulation and Modeling of Physical Vapor Deposition (PVD) Process

Authors: Ali Moarrefzadeh

Abstract: The deposition of thin film layers from the vapor phase is accomplished through several techniques. We review the physical vapor deposition (PVD) techniques and equipment that are in common use in the high-volume production of coatings that find application in the optical, display, decorative and tribological. Specific PVD processes and coating materials have been developed and optimized for each application. It is well established that low pressure physical vapor deposition processes such as thermal evaporation and the many variants of sputtering utilize nearly collision less vapor transport to a substrate. This results in line-of-sight deposition. The deposition of uniform coatings on complex shapes using these approaches therefore requires substrate rotation or a multiple evaporation source strategy. In many cases, the line-of-sight requirement precludes the use of these processes entirely. Recently, developed rarefied gas jet based deposition processes, however, operate at much higher pressures where many gas phase collisions occur. Direct simulation Monte Carlo (DSMC) simulations have been used to understand the fundamental phenomena involved and to identify the role of the process conditions on the coating’s uniformity.

Keywords: Modeling, Simulation, workpiece, coating, Surface, PVD

Title of the Paper: TVD Flux Vector Splitting Algorithms Applied to the Solution of the Euler and Navier-Stokes Equations in Three-Dimensions – Part I

Authors: Edisson Sávio De Góes Maciel

Abstract: In the present work, the Steger and Warming, the Van Leer, the Liou and Steffen Jr. and the Radespiel and Kroll schemes are implemented, on a finite volume context and using a structured spatial discretization, to solve the Euler and the Navier-Stokes equations in three-dimensions. A MUSCL (“Monotone Upstream-centered Schemes for Conservation Laws”) approach is implemented in these schemes aiming to obtain second order spatial accuracy and TVD (“Total Variation Diminishing”) high resolution properties. An implicit formulation is employed to the Euler equations, whereas the Navier-Stokes equations use an explicit formulation. The algebraic turbulence models of Cebeci and Smith and of Baldwin and Lomax are implemented. The problems of the supersonic flow along a compression corner (inviscid case), and of the supersonic flow along a ramp (viscous case) are solved. The results have demonstrated that the most severe and most accurate results are obtained with the Liou and Steffen Jr. TVD scheme. The turbulent results are presented in the second part of this work.

Keywords: Steger and Warming algorithm, Van Leer algorithm, Liou and Steffen Jr. algorithm, Radespiel and Kroll algorithm, TVD high resolution schemes, Turbulence models, Euler and Navier-Stokes equations, Three-Dimensions

Title of the Paper: TVD Flux Vector Splitting Algorithms Applied to the Solution of the Euler and Navier-Stokes Equations in Three-Dimensions – Part II

Authors: Edisson Sávio De Góes Maciel

Abstract: In the present work, the Steger and Warming, the Van Leer, the Liou and Steffen Jr. and the Radespiel and Kroll schemes are implemented, on a finite volume context and using a structured spatial discretization, to solve the Euler and the Navier-Stokes equations in three-dimensions. A MUSCL (“Monotone Upstream-centered Schemes for Conservation Laws”) approach is implemented in these schemes aiming to obtain second order spatial accuracy and TVD (“Total Variation Diminishing”) high resolution properties. An implicit formulation is employed to the Euler equations, whereas the Navier-Stokes equations use an explicit formulation. The algebraic turbulence models of Cebeci and Smith and of Baldwin and Lomax are implemented. The problems of the supersonic flow along a compression corner (inviscid case), and of the supersonic flow along a ramp (viscous case) are solved. The results have demonstrated that the most severe and most accurate results are obtained with the Liou and Steffen Jr. TVD scheme. The first paper of this work treats the inviscid and laminar viscous results. In this paper, the second of this series, the turbulent results are presented.

Keywords: Steger and Warming algorithm, Van Leer algorithm, Liou and Steffen Jr. algorithm, Radespiel and Kroll algorithm, TVD high resolution schemes, Turbulence models, Euler and Navier-Stokes equations, Three-Dimensions

Title of the Paper: Windage Power Loss in Spur Gear Sets

Authors: Fakher Chaari, Manel Ben Romdhane, Walid Baccar, Taher Fakhfakh, Mohamed Haddar

Abstract: The windage power loss in gear transmission systems at high speeds can be significant and must be taken into account at the design stage in order to optimize the geometrical shape of the gear’s bodies to improve the mechanical efficiency. The main objective of this work is, first, to propose a design of a two-dimensional geometry of the spur gear using the commercial Computational Fluid Dynamics (CFD) Fluent 6.3.26 which enable us to detect the pressure and viscous moments due to the aerodynamic drag of the teeth in the airlubricant mixture. In addition, a parametric study concerning the influence of the geometrical shape of teeth and the lubricant on the evolution of the windage power losses on the gear teeth is carried out.

Keywords: windage power loss, spur gear, CFD, lubrication, addendum modification

Issue 3, Volume 7, July 2012

Title of the Paper: Simulation of Fully Coupled Thermomechanical Analysis of Disc Brake Rotor

Authors: Ali Belhocine, Mostefa Bouchetara

Abstract: Vehicle braking system is considered as one of the most fundamental safety-critical systems in modern vehicles as its main purpose is to stop or decelerate the vehicle. The frictional heat generated during braking application can cause numerous negative effects on the brake assembly such as brake fade, premature wear, thermal cracks and disc thickness variation (DTV). In the past, surface roughness and wear at the pad interface have rarely been considered in studies of thermal analysis of a disc brake assembly using finite element method.. The ventilated pad-disc brake assembly is built by a 3D model with a thermo-mechanical coupling boundary condition and multi-body model technique. The numerical simulation for the coupled transient thermal field and stress field is carried out by sequentially thermal-structural coupled method based on ANSYS to evaluate the stress fields and of deformations which are established in the disc had with the pressure of the pads and in the conditions of tightening of the disc thus the contact pressures distributions field in the pads which is another significant aspect in this research .The results obtained by the simulation are satisfactory compared with those of the specialized literature.

Keywords: Brake Discs, Pads, Heat flux, Heat transfer coefficient, Thermo-mechanical coupling, Von Mises stress, Contact pressure

Title of the Paper: Explicit and Implicit TVD High Resolution Schemes in 2D

Authors: Edisson Sávio De Góes Maciel

Abstract: The present work compares the TVD schemes of Roe, of Van Leer, of Yee,Warming and Harten, of Harten, of Yee and Kutler and of Hughson and Beran applied to the solution of an aeronautical problem. Only the Van Leer scheme is a flux vector splitting one. The others are of flux difference splitting type. The Roe and Van Leer schemes reach second order accuracy and TVD properties by the use of a MUSCL approach, which employs five different types of nonlinear limiters, that assures TVD properties, being them: Van Leer limiter, Van Albada limiter, minmod limiter, Super Bee limiter and -limiter. The other schemes are based on the Harten’s ideas of the construction of a modified flux function to obtain second order accuracy and TVD characteristics. The implicit schemes employ an ADI (“Alternating Direction Implicit”) approximate factorization to solve implicitly the Euler equations, whereas in the explicit case a time splitting method is used. Explicit and implicit results are compared trying to emphasize the advantages and disadvantages of each formulation. The Euler equations in conservative form, employing a finite volume formulation and a structured spatial discretization, are solved in two-dimensions. The steady state physical problem of the supersonic flow along a compression corner is studied. A spatially variable time step procedure is employed aiming to accelerate the convergence of the numerical schemes to the steady state condition. This technique has proved an excellent behavior in terms of convergence gains, as shown in Maciel. The results have demonstrated that the most accurate solutions are provided by the Roe TVD scheme in its Super Bee variant.

Keywords: Roe scheme, Van Leer scheme, Yee, Warming and Harten scheme, Harten scheme, Yee and Kutler scheme, Hughson and Beran scheme, Explicit and implicit formulations, TVD formulation, Euler and Navier-Stokes equations

Title of the Paper: Novel Metaheuristic Algorithms Applied to Optimization of Structures

Authors: Letícia Fleck Fadel Miguel, Leandro Fleck Fadel Miguel

Abstract: This paper aims at to evaluate the performance in engineering problems of two of the most recent metaheuristic algorithms developed in the last decade. The selected metaheuristic methods are Harmony Search (HS) and Firefly Algorithm (FA). Initially a brief description of both methods is presented and next they are applied in the field of classical structural optimization problems of truss structures. The effectiveness of Harmony Search and Firefly Algorithm is demonstrated through four benchmark structural optimization problems. The results show the ability of both metaheuristic algorithms to find optimal solutions for structural optimization problems in a relatively low computational cost.

Keywords: Harmony Search, Firefly Algorithm, Optimization, Engineering Design, Benchmark Problems, Truss Structures

Title of the Paper: Numerical Study of Solid Particles-Based Airlift Pump Performance

Authors: A.-F. Mahrous

Abstract: This work aims to numerically investigate the performance of airlift pump, lifting solid particles, under a variety of conditions. A numerical model of airlift pump based on the concept of momentum balance was developed and validated against available experimental data. Parametric predictive studies of the effects of solid particles conditions on model airlift pump performance were carried out. The predicted results showed that the solid particles volumetric concentration in the suction section of the airlift tube would significantly affect the airlift pump efficiency based on solids as the main gain of the pump. On the other hand, larger diameters of solid particles and higher input airflow rates would have a negative effect on the pump performance.

Keywords: Airlift pump, Performance study, Two-phase flow, Three-phase flow

Title of the Paper: Explicit and Implicit TVD and ENO High Resolution Algorithms Applied to the Euler and Navier-Stokes Equations in Three-Dimensions – Turbulent Results

Authors: Edisson Sávio De Góes Maciel

Abstract: In the present work, the Harten and Osher TVD/ENO and the Yee TVD symmetric schemes are implemented, on a finite volume context and using a structured spatial discretization, to solve the laminar/turbulent Navier-Stokes equations in the three-dimensional space. The Harten and Osher TVD/ENO schemes are flux difference splitting type, whereas the Yee TVD scheme is a symmetric one, which incorporates TVD properties due to the appropriated definition of a limited dissipation function. All three schemes are second order accurate in space. Turbulence is taken into account considering two algebraic models, namely: the Cebeci and Smith and the Baldwin and Lomax ones. A spatially variable time step procedure is also implemented aiming to accelerate the convergence of the algorithms to the steady state solution. The gains in convergence with this procedure were demonstrated in Maciel. The schemes are applied to the solution of the physical problem of the low supersonic flow along a ramp. The results have demonstrated that the most accurate results are obtained with the Harten and Osher ENO scheme. This paper is the third part of this work, TURBULENT RESULTS, considering the description of the turbulence models and the solutions obtained with them and compared with the laminar results.

Keywords: Harten and Osher algorithm, TVD/ENO formulations, Yee symmetric algorithm, TVD formulation, Euler and Navier-Stokes equations, Turbulence models, Explicit and implicit algorithms, Finite Volumes

Title of the Paper: Optimal Low-Thrust Trajectories to Reach the Asteroid Apophis

Authors: D. P. S. Santos, A. F. B. A. Prado

Abstract: Apophis is considered by the Greeks as chaos, the God of destruction. For this reason, in current times, this name returns to scene to represent a destructive potential threat to the Earth. It is the name of an asteroid that orbits a region that represents a high risk of collision with the Earth. This asteroid was discovered in 2004 and received the initial name of 2004MN4. Then it was named Apophis, and several researchers and institutes are monitoring and designing missions with the goal of finding more information about the asteroid. The present research has the goal of finding optimal (in the sense of minimum fuel consumption) interplanetary missions, based in low thrust propulsion systems to send a spacecraft to Apophis. The spacecraft is assumed to leave the Earth from a Low Earth Orbit (LEO). An indirect optimization method is used in the simulations to find the trajectories. Two different engines will be used to determine the trajectories: the PPS1350 and the Phall 1. This is done to get some insights of the differences between a propulsion system that has a fixed magnitude for the force and one that has a magnitude that varies with the distance between the spacecraft and the Sun. Another reason to perform this research is to test the parameters of the Phall 1, that is an engine under development.

Keywords: Astrodynamics, Celestial Mechanics, Space Trajectories, Low-Thrust, Solar Electric Propulsion

Title of the Paper: The Geometric Effect on the Evolution of a Long Bubble in a Circular Contraction Tube Followed by an Expansion Tube

Authors: G.-C. Kuo, C.-H. Hsu, C.-C. Chang,Y.-H. Hu, W.-L. Liaw, K.-J. Wang, K.-Y. Kung, Yute Chen

Abstract: In this paper, a long bubble elongates through a contraction tube followed by an expansion tube filled with viscoplastic fluids was studied experimentally and numerically. The effects of both tube geometry and fluid characteristics on the bubble profiles and fractional converge were evaluated. In the experimental aspect, the bubble profiles and the fractional converge were obtained by image processing the photos captured with a high-speed camera. In the numerical analysis aspect, the continuity equation and momentum equation were converted to the equations in the form of streamline and vorticity. The differential equations were discretized with the finite difference method. Gauss-Seidel Iteration method with successive over-relaxation (SOR) were applied in the computation of the viscous fluid flows. The evolution of the bubble contour predicted by a conservative Level Set Method was applied to this study. The results showed that the fractional converge of the fluid, the bubble profile and velocity changed due to the effects of the fluid viscosity, the gas the flow rate and the contraction/ expansion angle of the tube. The bubble profile, developing along the stream line, was changed by the effects of the inertia force, surface tension and capillary force, etc. The bubble profiles and the flow fields generated by numerical simulation were applied to explain the experimental observations. Both experimental observation and numerical simulation results were in the same trend. A good consistency was shown between our results and the related researches.

Keywords: Evolution, Level Set Method, Long Bubble, Streamline, Viscoplastic Fluids, Vorticity

Issue 4, Volume 7, October 2012

Title of the Paper: Determination of Onboard Coplanar Orbital Maneuvers with Orbits Determined using GPS

Authors: Ana Paula Marins Chiaradia, Antonio Fernando Bertachini De Almeida Prado, Hélio Koiti Kuga

Abstract: In the present paper a study is made in order to find an algorithm that can calculate coplanar orbital maneuvers for an artificial satellite. The idea is to find a method that is fast enough to be combined with onboard orbit determination using GPS data c

Keywords: Astrodynamics, Orbital Maneuver, Artificial Satellite, GPS, Lambert Problem.

Title of the Paper: Specific Peculiarities of the Jets Penetrating the Liquid Pool of Different Density under Severe Accidents at the NPP Conditions and their Modeling and Simulation

Authors: Ivan V. Kazachkov, Vahid Hasani Moghaddam

Abstract: The paper is devoted to one of the problems of the modelling and simulation of the severe accidents at the nuclear power plants (NPP) in touch with development and operation of the passive protection systems against severe accidents. The results of the ma

Keywords: Jet, Penetration, Pool, Bifurcation, Mathematical Modelling, Non-linear Phenomenon, Switch of Radius, Passive Protection System

Title of the Paper: Thermochemical Non-Equilibrium Reentry Flows in Two-Dimensions: Seven Species Model - Part I

Authors: Edisson Sávio De Góes Maciel, Amilcar Porto Pimenta

Abstract: This work presents a numerical tool implemented to simulate inviscid and viscous flows employing the reactive gas formulation of thermochemical non-equilibrium. The Euler and Navier-Stokes equations, employing a finite volume formulation, on the context o

Keywords: Thermochemical non-equilibrium, Reentry flow, Seven species chemical model, Arrhenius formula, Structured and unstructured solutions, Euler and Navier-Stokes equations, Two-Dimensions.

Title of the Paper: TVD and ENO Applications to Supersonic Flows in 2D – Part II

Authors: Edisson Sávio De Góes Maciel, Eduardo Manfredini Ferreira

Abstract: In this work, second part of this study, the high resolution numerical schemes of Yee and Harten, of Yang second order, of Yang third order, and of Yang and Hsu are applied to the solution of the Euler and Navier-Stokes equations in two-dimensions. All sc

Keywords: Yee and Harten algorithm, Yang second order TVD/ENO algorithm, Yang third order TVD/ENO algorithm, Yang and Hsu UNO algorithm, Euler and Navier-Stokes equations, Finite Volumes