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Computational Modeling (MCSUL), 2009 Third Southern Conference on

Date 23-25 Nov. 2009

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Displaying Results 1 - 25 of 36
  • [Front cover]

    Page(s): C1
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  • [Title page i]

    Page(s): i
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  • [Title page iii]

    Page(s): iii
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  • [Copyright notice]

    Page(s): iv
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  • Table of contents

    Page(s): v - vii
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  • Preface

    Page(s): viii
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  • Program Committee

    Page(s): ix - x
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  • Reviewers

    Page(s): xi - xii
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  • Mathematical Optimization: Application to the Design of Optimal Micro-channel Heat Sinks

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (499 KB) |  | HTML iconHTML  

    This paper documents the geometrical optimization of a micro-channel heat sink. The objective is to optimize (minimize) the wall peak temperature of the heat sink subject to various constraints such as manufacturing restraints, fixed pressure drop and total fixed volume. A gradient based optimization algorithm is used as it adequately handles the numerical objective function obtained from the computational fluid dynamics simulation. Optimal geometric parameters defining the micro-channel were obtained for a pressure drop ranging from 10 kPa to 60 kPa for a given fixed volume. The effect of pressure drop on the aspect ratio, solid volume fraction, channel hydraulic diameter and the minimized peak temperature are reported. Results also show that as the dimensionless pressure drop increases the maximised dimensionless global thermal conductance also increases. These results are in agreement with previous work found in literature. View full abstract»

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  • Constructal Design Applied to the Optimization of Heat Transfer in a Solid Conducting Wall

    Page(s): 7 - 11
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB) |  | HTML iconHTML  

    The present paper applies Constructal Design to optimize the geometry of a Y-shaped negative fin that intrudes a solid conducting wall with heat generation. The main goal is the minimization of the thermal global resistance between the solid wall and the negative fin, which removes energy from the wall. The optimization is achieved by varying the angle between the tributary branch of the Y-Shaped fin and the horizontal axis, as well as, by varying the ratio between the volume of the fin and the rectangular volume that circumscribes it (ψ), while the other geometric parameters are maintained fixed. Constructal Design led to a best configuration, with a thermal global resistance of 53%, 49% and 48% for ψ = 0.3, ψ = 0.4 and ψ = 0.5, respectively, smaller than the ones for the worst configuration. View full abstract»

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  • Thermal Optimization of Circular Bodies Submitted to an Intense Heat Flux by Constructal Design

    Page(s): 12 - 17
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1443 KB) |  | HTML iconHTML  

    The present work studies the optimization of a circular body with an intense heat flux by Constructal Design. The problem concerns the minimization of the global thermal resistance of a three-dimensional structure submitted to an intense uniform heat flux, which is cooled through microchannels inserted in the circular body. For the optimization the body and the channels volumes are kept constants, while the geometrical configuration varies. Two geometric configurations were studied: radial and with one level of bifurcation-the first construct. The conservation equations of mass, momentum and energy are solved using a commercial package based on the finite volume method. For the radial configuration the system was successfully optimized as function of the number of ducts intruded into the body. For the bifurcated configuration Constructal Design led to a double optimization: one as function of the angle between the branches on the bifurcation (δ) and other as function of the ratio between the length of a single duct (L0) and the radius of the circular domain (L). View full abstract»

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  • A Comparison between Random and Deterministic Tree Networks for River Drainage Basins

    Page(s): 18 - 23
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (367 KB) |  | HTML iconHTML  

    A fully determinisitc erosion model recently developed was used to explain the natural creation of river networks, which was assumed to be due to the optimal reduction of the flow resistance in a area to point flow. This work adds to this discussion, modifying the model to a fully random approach. The results showed that randomness does not create networks, but the global reduction of the flow resistance follows the same trend of the deterministic networks. This suggest that local factors also are important to the explanation of the very existance of natural networks. View full abstract»

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  • Analytical/Numerical Solution for the Lagrangian Flamelet Model Equations

    Page(s): 24 - 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (195 KB) |  | HTML iconHTML  

    In the last years, the understanding of the combustion processes has been facilitated through the progress of asymptotic methods in applied mathematics, of the computation and of experimental techniques. The aim of this work is to obtain and compare analytical/numerical results with experimental data for a confined jet diffusion flame. All thermochemical variables are determined by mixture fraction because the Sandia Flame D, used to check the results, is close to equilibrium. The developed method, based on the low Mach number formulation, allows to decrease the time needed to obtain reasonable results for confined jet diffusion flame. The analytical/numerical results compare well with the experimental data available in the literature. View full abstract»

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  • A Numerical Study of the Influence of Temperature Fluctuations in the Thermal Radiation Field

    Page(s): 31 - 36
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (410 KB) |  | HTML iconHTML  

    The present paper performs a numerical study of the influence of fluctuations on the temperature field over the thermal radiation field with the purpose to simulate the effect of Turbulence-Radiation Interactions (TRI). To evaluate the behaviour of the divergence of radiative heat flux for a flame in a cylindrical cavity, four temperature profiles are imposed: an average temperature profile and other three with 10%, 20% and 30% of turbulence intensity. The radiative transfer equation is solved using the discrete ordinates method (DOM) and the participating medium is treated as a gray gas. The results achieved demonstrate that the fluctuations of temperature profiles increase significantly the mean divergence of the radiative heat flux in comparison with the average temperature profile, reaching to approximately 20% for the profile with 30% of turbulence intensity. View full abstract»

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  • Numerical Simulation Flow Analyses around a Cylinder under Transversal and Eight Trajectories

    Page(s): 37 - 42
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    This work aims to study a two-dimensional incompressible flow around a cylinder in forced movement in order to understand the phenomena that occur in cylindrical structures under periodic oscillation using the Direct Numerical Simulation technique. The simulations were taken using the computational code named Incompact3d. It was used the Reynolds Number as 400 in all simulations. The trajectories transversal and eight shapes were simulated for a range of displacement amplitude. The Navier-Stokes and continuity equations were used to discretize the flow in a Cartesian mesh. It was used the third-order Runge-Kutta scheme with low-storage for the pass-time and the body was represented by the virtual boundary method. The temporal mean of the drag and lift coefficients and vortex shedding mode were computed. The results show large variations of the mean lift coefficient with the amplitude displacement for all trajectories, and so altering the vortex shedding mode. The 2S mode was observed for simulations with transversal trajectories, except for amplitude of 0.55D, which presented the 2P mode. Simulations with eight trajectory presented 2P mode in most cases, and for certain amplitudes the periodic shedding modes were not observed. View full abstract»

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  • Numerical Simulation of the Interaction of a Regular Wave and a Submerged Cylinder

    Page(s): 43 - 48
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB)  

    A numerical simulation of the interaction between a regular wave and an immersed horizontal cylinder, whose axis is 3-radius deep, perpendicular to the direction of the wave propagation, is presented in this paper. The numerical model uses the semi-implicit two-step Taylor- Galerkin method to integrate Navier-Stokes equations in time and space. Arbitrary lagrangean-eulerian formulation is employed to describe the free surface movement. The free surface elevations near the cylinder and in some gauges along the channel, as well the spectrum distribution, are compared with experimental ones, and good agreement is obtained. The analysis shows that the viscous effects only affect the area that is very close to the cylinder. View full abstract»

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  • Evaluation of Air -- Water Flow in an Evaporative Condenser

    Page(s): 49 - 54
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    Evaporative condensers present a hard problem fornumerical modeling because of the complex phenomena of heatand mass transfer outside of the bundle tubes in turbulent flows. The goal of this work is to study the air and water behavior inside an evaporative condenser operating with ammonia as the refrigerant fluid. A commercial CFD software package (FLUENT) is employed to predict the two-phase flow of air and water droplets in this equipment. The air flow is modeled as a continuous phase using the Eulerian approach while the droplets water flow is modeled as a disperse phase with Lagrangian approach. The coupling between pressure and velocity fields is performed by the SIMPLE algorithm. The pressure, velocity and temperature fields are used to perform qualitative analyses toidentify functional aspects of the condenser, while thetemperature and the relative humidity evolution contributed to verify the agreement between the results obtained with the numerical model and those presented by equipmentmanufacturer. View full abstract»

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  • Numerical Simulation of Water Circulation in a Cylindrical Horizontal Thermal Tank

    Page(s): 55 - 59
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (662 KB) |  | HTML iconHTML  

    It is carried out a numerical study of the three-dimensional temperature and velocity fields in a cylindrical horizontal thermal tank during the process of water circulation. The numerical simulations were made using an academic Finite Volumes numerical code. This simulation considers that the thermal tank is connected to solar collectors. So, in the tank, the inlet jet temperature is higher than those inside the tank. This study aims to investigate the influence of the inlet jet on thermal stratification. The results show that for the mass flow rate studied, there is no significant variation on thermal stratification. View full abstract»

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  • Computational Modeling of a Regular Wave Tank

    Page(s): 60 - 65
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    This work studies two different numerical methodologies for the generation of regular gravity waves. Numerical simulations for the wave generation were performed with the FLUENT® package, using the multiphase Volume of Fluid (VOF) model to reproduce the wave propagation inside the tank. Therefore, it was possible to analyze two methodologies for regular wave generation that could be used in future works, mainly in the study of devices for sea wave energy conversion in electric energy. View full abstract»

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  • Numerical Study of Reservoir Cooling by Means of Peltier Effect

    Page(s): 66 - 70
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    The present work studies numerically and experimentally the water cooling process by means of natural convection inside a closed reservoir. The cooling process is performed by Peltier or Thermoelectric effect. The purpose here is to obtain the thermal gradient inside the reservoir and to search for the best point where the coldest water can be extracted from the reservoir, which can be considered a geometric optimization of the device thermal design. The analyzed flow is incompressible, laminar, transient and three-dimensional. The Boussinesq approximation is employed for the treatment of buoyancy forces. For the numerical approach of the flow, the mass, momentum and energy conservation equations are solved by a commercial package based on the finite volume method (FLUENT®). The temperature field as function of time obtained by numerical simulations is confronted with the experimental data. The numerical results estimated satisfactorily the transient thermal behavior predicted by laboratory experiments. View full abstract»

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  • An Adaptive Mesh Strategy for Transient Flows Simulations

    Page(s): 71 - 76
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3188 KB) |  | HTML iconHTML  

    An adaptive mesh strategy for the numerical simulation of incompressible transient flows with heat transfer and mass transport is presented in this work. The Finite Element technique, with unstructured meshes formed by tetrahedral elements, and the two-step Taylor-Galerkin method are used. The velocity field is obtained by an explicit scheme, while pressure field is computed by an implicit scheme using a pre-conditioned conjugate gradient method. Error indicators, an adaptation criterion, a refinement scheme, a smoothing process and an appropriate data structure are used to obtain a suitable mesh in order to get accurate results. To evaluate the adaptive mesh strategy performance, two numerical applications involving transient incompressible viscous fluid flows with heat transfer and mass transport, taking into account relevant error indicator, are presented. View full abstract»

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  • A Mathematical Model for the Estimation of Treatment Cost in Cancer Radiotherapy

    Page(s): 77 - 81
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (397 KB) |  | HTML iconHTML  

    In this work we present a methodology for the investigation of costs of cancer treatment by radiotherapy, aiming to reduce the undesired effects of radiation and to obtain better results of the treatment. The tumor growth is simulated by using a mathematical model composed of three ordinary diferential equations corresponding to the population of Normal (N), Tumoral (T) and Imune (I) cells. The effect of radiation over each type of cells is considered using the linear quadratic model applied for the various distinct treatment protocols investigated. Cost of treatment is obtained using a model based on the concept of tumor cure probability, cost per fraction and cost of failure. The concept of biological effective dose is used in order to compare differente treatment protocols. We investigated different protocols currently used for various tumor types. Our results show that with this approach it is possible to obtain more efficient protocols with lower cost that those used. It is also possible to investigate the effect of fractionation protocols on the tumor evolution in order to obtain less aggressive protocols that are effective for patient cure with lower total dose and in smaller treatment time. View full abstract»

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  • A General Purpose Cave-Like System for Visualization of Animated and 4D CAD Modeling

    Page(s): 82 - 87
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (813 KB) |  | HTML iconHTML  

    In the last decade, virtual reality (VR) systems have been used to enhance the visualization of CAD projects. The immersive VR techniques allow to the designer interacting and modeling in a more intuitive and efficient way. Current 4D and animated simulation CAD tools are a new challenge for immersive visualization. In this paper we propose a general purpose cave-like system that enables interactive visualization of 4D and animated CAD models. In an automated way, the system is able to treat static and dynamic 3D environments, allowing to share the experience of navigation in the scene among the users, even geographically distributed. The system proposed is validated through a case-study using dynamic 3D models created on digital manufacturing softwares of Shipbuilding and Offshore Industries. View full abstract»

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  • A Framework for Distributed Shared Memory - Case Study in Geoscience Applications on Clusters of Computers

    Page(s): 88 - 93
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    This paper describes how to distribute application data using a middleware composed of a remote access Memory Management Data Base as base layer and a convergence layer to the application. One server of de MMDB must be installed on each node of a computer network and over it a convergence layer that distributes the data transparently. The ideas are presented through a case example implementation using Berkeley DataBase as storage layer and a convergence layer to Network Common Data Form - NetCDF, standard used in geosciences to store large volumes of data. View full abstract»

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  • Energy from the Sea: Computational Modeling of an Overtopping Device

    Page(s): 94 - 99
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    This work presents a brief study about the wave energy as well as a computational modeling of an overtopping device. The numerical simulation was performed with the FLUENT® Computational Fluid Dynamic software code, employing the multiphase Volume of Fluid (VOF) model. The obtained results showed a satisfactory agreement between the numerical and analytical solutions, being the maximum difference calculated for the wave generation of approximated 4.6%. It was also observed that the knowledge of the wave height and an adequate ramp design are factors that determine the overtopping occurrence. View full abstract»

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