ENCIT2012-338 NUMERICAL SIMULATION OF A 2D TURBULENT FLOW CLOSE TO A SEPARATION POINT - PDF
Leon Matos Ribeiro de Lima, Norberto Mangiavacchi, UERJ, Brazil
Abstract: This work presents a 2D analysis of a turbulent flow over a steep hill, without turbulence model, focusing on the turbulent boundary layer separation. The numerical methodology employs a Finite Element code with first order Semi-Lagrangian scheme for time discretization. Velocity and pressure fields are decoupled by the Discrete Projection Method. The separation and reattachment points, mean velocity profiles and the wall shear stress distribution are compared to numerical and experimental results found in recent literature. The study provides interesting results regarding the applicability of simple 2D numerical models to the simulation of turbulent flows over hills.
Keywords:Turbulent flows; Finite Element Method; Boundary layer separation.
Presentation Schedule: Thursday, 14:40-15:00. Session: FMR4-5. Presenter: Leon Matos Ribeiro de Lima.
ENCIT2012-039 NUMERICAL ANALYSIS OF THE INTERACTION AMONG FLOWS AT LOW REYNOLDS NUMBERS AND ELASTICALLY MOUNTED CYLINDERS - PDF
Rafael de Almeida Gonçalves, Paulo Roberto de Freitas Teixeira, FURG, Brazil
Eric Didier, Laboratório Nacional de Engenharia Civil, Portugal
Abstract: The vortex-induced vibration (VIV) phenomenon has drawn the attention of researchers in Engineering for several decades. An example is the riser used for petroleum exploration, in which it is subjected to marine flows that may cause oscillations due to vortex shedding. In this paper, numerical analyses of the phenomena that occur in the interaction among flows at low Reynolds number and elastically mounted cylinders are presented. The simulation is carried out by using the numerical model that uses a semi-implicit two-step Taylor-Galerkin method to discretize the Navier-Stokes equations and the arbitrary lagrangean-eulerian formulation to follow the cylinder movement. The rigid body motion description is calculated by using the Newmark method. Firstly, the characteristics of the vortex generation process for the fixed cylinder are analyzed. In this case, the Strouhal number, the mean drag and the RMS lift coefficients for Reynolds numbers ranging from 90 to 140 are shown. Afterwards, an analysis of a flexible supported cylinder (with a spring and a damper) in transverse direction subject to flows with Reynolds numbers ranging from 90 to 140 is carried out. The cylinder displacement and the vibration frequencies are studied; the synchronization between the vortex shedding and the vibration frequency (lock-in) is analyzed. Similar results to the experimental ones developed by Anagnostopoulos and Bearman (1992) were obtained in this study.
Keywords:Finite element method; Oscillating cylinder; Fluid-structure interaction.
Presentation Schedule: Thursday, 15:40-16:00. Session: FMR4-5. Presenter: Rafael Almeida Gonçalves.
ENCIT2012-069 PSEUDOSPECTRAL AND FINITE VOLUME SOLUTIONS OF THE BURGERS EQUATION - PDF
Andreia Aoyagui Nascimento, Elie Luis Martinez Padilla, UFU, Brazil
Felipe Pamplona Mariano, UFG, Brazil
Abstract: The Finite Volume method (FVM) and Fourier Pseodospectral method (FPM) are applied to solve the problem convection and diffusion named Burgers equation, with a viscosity (\&\#957;= 0,2 [m2 /s]) and advecting with the velocity c=4,0 [m/s] (Canuto et al., 2006). At the present work, proposes the solution this equation for two domians: periodic and non periodic. Towards the FVM, was used two differents interpolation scheme: the upwind and central-difference. Which was possible to show that at periodic domain, the central-difference scheme of the FVM, reach the better results in comparison with upwind scheme. In simulations obtained by FPM, the results con\&\#64257;rm the high accuracy of Fourier pseudospectral method and reach round-off errors. For the non-periodic domain, the boundary conditions were modeling by immersedboundary. In this case the solution of FPM attain only second order convergency.
Keywords:Burgers equation; Fourier Pseudospectral methodo; Finite Volume method.
Presentation Schedule: Wednesday, 15:20-15:40. Session: FMR4-4. Presenter: Andreia Aoyagui Nascimento.
ENCIT2012-113 THE IMPORTANCE OF THREE-DIMENSIONAL SIMULATIONS IN FLOW OVER A BACKWARD FACING STEP - PDF
Felipe Mariano, UFG, Brazil
Leonardo de Queiroz Moreira, Aristeu da Silveira Neto, UFU, Brazil
Abstract: The flow over backward-facing step is a classic Fluid Dynamic problem, it consists in a suddenly expansion duct, where the flow develop downstream of the expansion. The geometry of domain is simple (Cartesian) and the detached point is known, at the same time, the flow developed is complex, where many physical structures flow are generated, recirculation zone, Kelvin-Helmholtz instabilities, reattachment of boundary layer, etc. The aim of the present article is to study the influence of tree-dimensional simulations in flow over backward-facing step, for this purpose the IMERSPEC methodology is used to solve the Navier-Stokes and continuity equations. The IMERSPEC consist in use the Pseudo-Spectral Fourier Method (PSFM). This method provides an excellent numerical accuracy and low computational cost in comparison with another high-accuracy methods. Another important issue is that in Fourier space, the solution of Navier-Stokes equations does not require to solve a Poisson equation, which is usually the most computational onerous part in classic methodologies. For model the boundaries conditions of the problem Immersed Boundary Method (IBM) is used. This approach is necessary due to the requirement of periodic boundary conditions to use FFT. The results show that the dependency of flow at high Reynolds numbers of three-dimensional simulations.
Keywords:Backward-facing step; Fourier Pseudo-Spectral Method; Immersed Boundary Method.
Presentation Schedule: Monday, 15:20-15:40. Session: FMR4-1. Presenter: Felipe Pamplona Mariano.
ENCIT2012-154 AGGLOMERATION SCHEMES STUDIES IN THE ADDITIVE CORRECTION MULTIGRID METHOD APPLIED TO NUMERICAL SOLUTION OF NAVIER-STOKES EQUATIONS WITH UNSTRUCTURED GRIDS - PDF
Susie Cristine Keller, Clovis Raimundo Maliska, UFSC, Brazil
Abstract: Multigrid methods efficiently solve large linear equations systems resulting from the discretization of partial differential equations. These methods improve the convergence rate of iterative methods by reducing all error frequency modes iteratively solving the problem in several meshes. The Additive Correction Multigrid Method (ACM) has several advantages compared to the traditional multigrid methods, normally the geometrical ones, in which the agglomeration is done based on the geometry of the grid and interpolation is required for passing the solution from one grid to the coarse one. In the ACM the discretization is done only in the original (fine) grid with the approximate equations in the coarse grid obtained using coefficients from the previous grid. It is a conservative method applied to structured as well as unstructured grids that efficiently deals with discontinuous or anisotropics coefficient problems since it allows the use of adaptive agglomeration schemes. The agglomeration scheme is of utmost importance for the method and, in order to improve this procedure, different ways to perform cells agglomeration were tested here.
Keywords:Additive Correction Multigrid; Agglomeration Schemes; Navier-Stokes Equations; Unstructured Grids.
Presentation Schedule: Monday, 18:00-18:20. Session: FMR4-2. Presenter: Susie Cristine Keller.
ENCIT2012-199 INFLUENCE OF ASPECT RATIO IN THE TURBULENT CONVECTION IN A RECTANGULAR CAVITY - PDF
Renata Munhoz Guimarães, Viviana Cocco Mariani, PUCPR, Brazil
Kátia Cordeiro Mendonça, Université de La Rochelle, France
Abstract: The purpose of this study is to know the air distribution in a conditioned room, through the numerical investigation of the influence of aspect ratio in the thermal and fluid dynamics behavior of a turbulent flow. To achieve that objective, some simulations were done of the flow inside a rectangular room, where the air enters through an opening in the top of one wall and leaves the room through an opening in the bottom of the opposite wall. The Reynolds mean equations are used, with the turbulence model RSM BSL (Reynolds Stress Model - Baseline) to solve four cases, with different geometries. It was concluded that, in general, the turbulence model used in this work is capable to predict quite well the fluid dynamics behavior of the flow, which is influenced by the room length, but not by its width.
Keywords:turbulence; CFD; Reynolds Stress Model.
Presentation Schedule: Monday, 17:40-18:00. Session: FMR4-2. Presenter: Renata Munhoz Guimarães.
ENCIT2012-276 SEMI-LAGRANGIAN HIGH-ORDER 3D INTERPOLATION: SURVEY ON A FINITE ELEMENT Z-TYPE OPERATOR - PDF
Gustavo Charles Peixoto de Oliveira, Norberto Mangiavacchi, UERJ, Brazil
José da Rocha Miranda Pontes, UFRJ, Brazil
Abstract: Discrete models using Semi-Lagrangian advection depend on a good mechanism of interpolation because they not only rely on the integration the trajectories of fluid particles traveling in space but also on the evaluation of quantities at determined points that do not necessarily match to the mesh points. The subject of this paper is to discuss and to survey new capabilities of a high-order interpolation operator using cubic shape functions as well as to demonstrate the reduction of errors originating from a Z-Type approach by considering directional derivatives over every element. This capability translates into a good fit for the convective term embedded into the incompressible Navier-Stokes equations, since the velocity at the departure point, whether it has to be interpolated, is found with more accuracy. Maximum error value obtained is limited to O(10\&\#8722;3). A fairly good approximation is produced showing the influence of the directional derivatives calculated over the edges of the element.
Keywords:Semi-Lagrangian; Finite Element; Interpolation.
Presentation Schedule: Thursday, 15:20-15:40. Session: FMR4-5. Presenter: Gustavo Charles Peixoto de Oliveira.
ENCIT2012-318 ANALYSIS OF STRONG STABILITY PRESERVING TIME-MARCHING SCHEMES FOR PARTIAL DIFFERENTIAL EQUATIONS - PDF
Gabriel de Moraes, Renan de Souza Teixeira, IME, Brazil
Leonardo Santos de Brito Alves, UFF, Brazil
Abstract: Several unsteady problems in transport phenomena require highly accurate solutions. It is, therefore, strongly desirable to increase the order of accuracy in time, while still maintaining the same stability properties. Strong stability preserving (SSP) methods are designed to achieve this goal. This paper was concerned with the main concepts in the field of the so-called non-linear monotone, high-order methods. In order to numerically investigate some features about this class of methods, some numerical tests were made on the shock tube problem.
Keywords:Strong Stability Preserving; Runge-Kutta methods; Total Variation Diminishing.
Presentation Schedule: Monday, 18:20-18:40. Session: FMR4-2. Presenter: Leonardo Santos de Brito Alves.
ENCIT2012-025 EFFECT OF FINITE DOMAIN ON VON KÁRMÁN PROFILES DEVELOPED IN THE NEIGHBORHOOD OF ROTATING DISK ELECTRODES - PDF
Carlos Domingo Mendez Gaona, UFRJ, Brazil
Gustavo Anjos, Norberto Mangiavacchi, UERJ, Brazil
José da Rocha Miranda Pontes, UFRJ, Brazil
Abstract: For many years the stability of rotating disk flow has been studied following the evolution of small perturbations superposed to the classical von Kármán's solution, von Kármán (1921, ZAMM, Vol. 19, pp. 233-252), Oliveira (Ms.C dissertation 2011, COPPE/UFRJ). These equations were obtained assuming an infinite domain. In this condition side wall effects are negligible Zandbergen (1987, Fluid Mechanics, Vol. 19, pp. 465-491), Barcia (2000, Journal of The Electrochemical Society, Vol. 155, No. 5, pp. 424-427), Anjos (Ms.C dissertation 2007, COPPE/UFRJ). In the present work we consider the effect of a finite domain on von Kármán's solution, aiming to find the minimum dimensions of the electrochemical cell, bellow which the assumption of von Kármán flow, with nondimensional velocity profiles dependen on the axial cordinate only, no longer holds.
Keywords:von Kármán; velocity profiles; Finite Elements Method.
Presentation Schedule: Tuesday, 17:00-17:20. Session: FMR4-3. Presenter: Carlos Domingo Mendez Gaona.
ENCIT2012-083 VORTEX SHEDDING SUPPRESSION ON A BLUFF BODY IN THE VICINITY OF A MOVING GROUND - PDF
Alex Mendonça Bimbato, Luiz Antonio Alcântara Pereira, FEI, Brazil
Miguel Hiroo Hirata, UERJ, Brazil
Abstract: The present work deals with the Vortex Method to study the vortex shedding suppression which occurs when a circular cylinder is placed near a plane surface that moves with the same velocity as the incident flow; this situation is particular important in practical engineering problems since it works with relative motion. Experimental data available in the literature show that in this kind of flow there is practically no boundary layer developed on the ground surface; using these observations in this work the ground plane motion is represented by the absence of vorticity generation on it. The numerical results obtained show that the above numerical strategy represented successfully the vortex shedding suppression.
Keywords:Vortex Method; Ground Effect; Moving Ground; Vortex Shedding Suppression.
Presentation Schedule: Monday, 16:00-16:20. Session: FMR4-1. Presenter: Alex Mendonça Bimbato.
ENCIT2012-086 PARALLEL BLOCK-STRUCTURED ADAPTIVE MESH REFINEMENT FOR INCOMPRESSIBLE NAVIER-STOKES EQUATIONS. - PDF
Rafael Sene de Lima, Márcio Ricardo Pivello, Aristeu da Silveira Neto, UFU, Brazil
Alexandre Megiorin Roma, USP, Brazil
Abstract: The numerical simulation of fluid flow involving complex geometries is greatly limited by the spatial grid resolution required. These flows often contain small regions with complex motions, while the remaining flow is relatively smooth. Adaptive mesh refinement (AMR) enables the spatial grid to be refined in local regions that require finer grids to resolve the flow. This work describes an approach to parallelization of a structured adaptive mesh refinement (SAMR) algorithm. This type of methodology is based on locally refined grids superimposed on coarser grids to achieve the desired resolution in numerical simulations. The main elements to achieve parallelization of SAMR algorithms are a dynamic load-balancing method to distribute work to rocessors and a dynamic distribution technique to manage communications. The methodology is based on a message passing model using the recursive coordinate bisection (RCB) for domain partition. For this work, a semi-implicit projection method has been implemented to solve the incompressible Navier-Stokes equations.
Keywords:Adaptive Mesh Refinement; Dynamic Load Balancing; Incompressible Navier Stokes Equations.
Presentation Schedule: NO PRESENTATION.
ENCIT2012-137 NUMERICAL SIMULATION OF NEWTONIAN AND NON-NEWTONIAN FREE SURFACE FLOWS USING THE SDPUS-C1 UPWINDING SCHEME - PDF
Giseli Aparecida Braz de Lima, Miguel Antonio Caro Candezano, Laís Corrêa, Valdemir Garcia Ferreira, USP, Brazil
Abstract: This study deals with the numerical simulation of complex incompressible fluid flows using a novel continuously differentiable bounded convection scheme (called SDPUS-C1). The scheme is based on TVD stability criteria and implemented in the context of finite difference methodology. The performance of the SDPUS-C1 scheme is assessed by solving 2D Newtonian and non-Newtonian free surface flows.
Keywords:free surface flow; non-linear convective terms; upwinding.
Presentation Schedule: Tuesday, 18:00-18:20. Session: FMR4-3. Presenter: Giseli Aparecida Braz de Lima.
ENCIT2012-200 A NEW TYPE OF TVD/CBC POLYNOMIAL UPWIND SCHEME FOR HYPERBOLIC CONSERVATION LAWS AND FLUID DYNAMICS PROBLEMS - PDF
Miguel Antonio Caro Candezano, USP, Colombia
Valdemir Garcia Ferreira, Giseli Aparecida Braz de Lima, USP, Brazil
Abstract: A new high-resolution polynomial TVD/CBC-based upwind scheme is developed for numerical solution of hyperbolic conservation laws and related fluid dynamic problems. The scheme, called TDPUS-C3, is implemented into the CLAWPACK software. Unsteady simulation of nonlinear problems demonstrates that the scheme is capable of stably reproducing shocks, discontinuities and complex structures in flows.
Keywords:CONVECTIVE TERMS; SIMULATION OF HYPERBOLIC CONSERVATION LAWS; UPWINDING; TVD/CBC.
Presentation Schedule: Wednesday, 15:00-15:20. Session: FMR4-4. Presenter: Giseli Aparecida Braz de Lima.
ENCIT2012-214 LOCAL DIFFERENTIAL QUADRATURE METHOD WITH RADIAL BASIS FUNCTIONS: NUMERICAL ASPECTS AND APPLICATIONS IN FLUID DYNAMICS AND HEAT TRANSFER PROBLEMS - PDF
Luís Guilherme Cunha Santos, Nelson Manzanares Filho, Genésio José Menon, FEI, Brazil
Abstract: The Local Differential Quadrature Method with Radial Basis Functions (LDQM-RBF) is a collocation method for numerical solution of partial differential equations. It has been recently proposed for treating complex discretizations including structured and non-structured meshes and meshless schemes. In this work, numerical experiments are carried out using a Poisson-type equation in a unit square domain with uniform equidistant meshes and various stencils. The influence of relevant parameters of LDQM-RBF (multiquadric shape parameter c, mesh size h and stencil structure) is discussed. Then, two applications of the LDQM-RBF in physical problems are made: a problem of incompressible hydrodynamics and a problem of natural convection, both in a square domain. Results are compared with the literature and discussed.
Keywords:Local Differential Quadrature Method; Radial Basis Functions; Multiquadric; Fluid Dynamics and Heat Transfer.
Presentation Schedule: Thursday, 16:00-16:20. Session: FMR4-5. Presenter: Luis Guilherme Cunha Santos.
ENCIT2012-382 A LOW ORDER ADVECTION DISCRETIZATION SCHEME BASED ON AN ADDITIONAL GRADIENT EQUATION - PDF
Luiz Eduardo Bittencourt Sampaio, Roney Leon Thompson, UFF, Brazil
Abstract: Several numerical schemes have been proposed in the literature to deal with flows involving convection, but all of them present some spurious effects. It is generally agreed that a high order scheme is preferable, and that it must be complemented with some kind of limiting technique to avoid spurious oscillations, which necessarily leads to a low order approximation for small structures. In this paper we revisit some literature consensus regarding numerical schemes, like TVD enforcing, order of convergence, and the possible role in physical modeling of turbulence. We show that many literature recommendations in this respect come from a misleading error assessment used in the analysis and design of such schemes. A more physically-oriented error assessment tool is thus proposed, in which the initial reconstruction errors are separated from the errors due to the physical transport. Focusing on the latter and ignoring the former allowed the development of a preliminary scheme that, despite being based on first order stencils, provided improved results for all cases tested, when compared to several higher order traditional schemes in linear and non-linear convection. In the particular case of 1D linear convection in a uniform field, commonly used as benchmark for aero-acoustics, the total transport errors were of the order of machine precision, with virtually zero diffusion and dispersion.
Keywords:Numerical schemes; convection; dispersion; diffusion; CFD.
Presentation Schedule: Thursday, 14:20-14:40. Session: FMR4-5. Presenter: Luiz Eduardo Bittencourt Sampaio.
ENCIT2012-383 MINIMAL GAIN MARCHING SCHEMES FOR STEADY-STATE SOLUTION GENERATION - PDF
Renan de Souza Teixeira, IME, Brazil
Leonardo Santos de Brito Alves, UFF, Brazil
Abstract: The numerical simulations of free shear layer has a critical point in the definition of accurate initial and boundary conditions. Different explicit and implicit marching schemes are described in this current paper. This procedure can be applied in a existing code designed for unsteady simulations. The steady-state are obtained efficiently with a parameter \$$\backslash$theta\$ of marching methods. Linear stability analysis is the fundamental theory that guarantee the optimal convergence in a process. This new methodology is tested on a code designed for compressible Navier-Stokes equation with arbitrary Mach number. Different parameters are investigated to demonstrate the efficiency of the methodology.
Keywords:Implicit and explicit scheme; Numerical Stability Analysis; Arbitrary Mach number; Steady-State solution; Initial and Boundary Conditions.
Presentation Schedule: Monday, 17:20-17:40. Session: FMR4-2. Presenter: Renan de Souza Teixeira.
ENCIT2012-016 HYDRODYNAMICS OF ELECTROCHEMICAL CELLS WITH A ROTATING SEMI-SPHERICAL ELECTRODE - PDF
Rachel Manhães Lucena, UFRJ, Brazil
Gustavo Rabello dos Anjos, Norberto Mangiavacchi, UERJ, Brazil
José da Rocha Miranda Pontes, UFRJ, Brazil
Abstract: We propose a numerical model to obtain results for the velocity and concentration profiles close to semispherical rotating electrodes in electrochemical cells. The profiles refer to nondimensional velocity components along the radial direction, for straight lines ranging from angles with the rotating axis 0 < theta < pi/2 obtained by solving the Navier-Stokes equations using the finite element method. The discretization of the domain is made with an object oriented approach. Spatial discretization of diffusive terms and the pressure is made by the Galerkin method. For the material derivative we use a semi-lagrangian method.
Keywords:Corrosion; Rotating Disk Flow; Semi-spherical Electrode; Finite Element Method.
Presentation Schedule: Monday, 17:00-17:20. Session: FMR4-2. Presenter: Rachel Manhães de Lucena.
ENCIT2012-031 ANTISYMMETRICAL MODE OF VORTEX SHEDDING DUE TO STREAMWISE VORTEX INDUCED VIBRATIONS OF A BLUFF BODY - PDF
Bruna Oliveira Passos e Silva Siqueira, Luiz Antonio Alcântara Pereira, FEI, Brazil
Miguel Hiroo Hirata, UERJ, Brazil
Abstract: The antisymmetrical A-I mode of vortex formation synchronized with the circular cylinder forced oscillation with respect to the free stream has been studied. Capture of the wake frequency by structural motion analysis utilising a Poisson equation for the pressure and numerical simulations, using the Discrete Vortex Method were carried out. This typical VIV response was investigated in a high Reynolds number flow of 100,000 at reduced velocity of 25 and ratio of amplitude and diameter Ax/d=0,13. The A-I mode ocurred as an alternate, out-of-phase shedding vortices from either side of the cylinder over an oscillation cycle, being so identified as the classical mode of formation of the Kármán street.
Keywords:bluff body; in-line oscillation; vortex shedding; lock-in phenomenon; vortex method.
Presentation Schedule: Wednesday, 16:20-16:40. Session: FMR4-4. Presenter: Bruna Oliveira Passos e Silva Siqueira.
ENCIT2012-032 THE FORMATION OF BINARY-VORTEX STREET BEHIND TWO CIRCULAR CILINDERS ARRANGED IN TANDEM - PDF
Paulo Guimaraes Moraes, Luiz Antonio Alcântara Pereira, FEI, Brazil
Miguel Hiroo Hirata, UERJ, Brazil
Abstract: Numerical investigations on the characteristics of the flow around a pair of immovable circular cylinders arranged in tandem were carried out. A purely Lagrangian Vortex Method was associated with a Poisson equation for the pressure to calculate global as well as local quantities at a supercritical Reynolds number (Re=65,000). The dominant vortex shedding frequencies in the wake of two cylinders were measured simultaneously using two fixed points placed behind each cylinder. A discontinuous jump on drag coefficient and Strouhal number was identified at a critical centre-to-centre distance between the cylinders; this behavior was found due to bi-stable nature of the gap flow. When the distance was larger than the critical spacing, the flow pattern was referred as co-shedding type, with both cylinders shedding vortices. For some pitch ratios there may be synchronization between the vortex shedding process and the vortex streets of the upstream and downstream cylinders, and the possible formation of a binary-vortex street behind downstream cylinder. A primary focus on the formation of binary-vortex street was analyzed in this study.
Keywords:: flow around two cylinders; in tandem; dominant vortex frequencies; wake interference; vortex method.
Presentation Schedule: Thursday, 16:20-16:40. Session: FMR4-5. Presenter: Luiz Antonio Alcântara Pereira.
ENCIT2012-127 NUMERICAL ANALYSIS OF THERMAL MODELS OF PLASTIC BALL GRID ARRAY COMPONENTS TYPE - PDF
Guilherme Rosati Mecelis, Alex Pereira da Cunha, Amarildo Tabone Paschoalini, Márcio Antonio Bazani, Reginaldo Ribeiro de Sousa, UNESP, Brazil
Abstract: Currently, circuits using complex electronic components are becoming bigger and increasing the number of components, leading to an enhancement of thermal computer simulations because of the large amounts of elements needed in the mesh. This study compares the components very detailed BGAs with the simplifications usually made to reduce the processing time, but keep the results within a tolerable error range. It aims to show that even using a simplified model, it is possible to obtain consistent results, saving processing time. This comparison is to perform a thermal simulation with component detailed in a numerical wind tunnel (with the following quantities: pressure, velocity and temperature controlled), collect the results and its processing time, and then perform the same simulation, but with the simplified component, which is basically a block with the basic features of the component, such as junction temperatures (tetajc and tetajb), thermal emissivity of the material of the package, etc., collect the same data analysis anterior. And finally, compare the results to gain insight into how different are the results of complex model for the simplified model and estimate the amount of error that exists in the simplified version.
Keywords:thermal model; PQFP; OpenFOAM.
Presentation Schedule: Monday, 16:20-16:40. Session: FMR4-1. Presenter: Edson Del Rio Vieira.
ENCIT2012-201 NUMERICAL SIMULATION OF THE THERMAL STORAGE TANK OF AN ADSORPTION AIR CONDITIONING SYSTEM POWERED BY SOLAR ENERGY - PDF
Cristian Adolfo, UFPB, Brazil
Belkacem Zeghmati, UPVD/LAMPS, France
Antonio Pralon Ferreira Leite, UFPB, Brazil
Abstract: The environmental conscience is bringing up significant methods and techniques to save energy and substitute the fossile fuel resources by renewable ones. The adsorption air conditioning system at LES-UFPB, has been projected by this point of view, as it's powered by solar energy. One of its components is a heat storage tank, which supply the adsorbers with water at high temperatures and also pre-heat the water flow before it goes to the solar collector field. The main goal of this article is to study numerically the effect of inlets and outlets flow on velocity and temperature fields inside this tank. The numerical computation was performed using the Fluent software. A grid independence was carried out and results of velocity and temperature fields are presented.
Keywords:CFD; heat storage tank; bi-dimensional; temperature field; velocity field.
Presentation Schedule: Tuesday, 17:40-18:00. Session: FMR4-3. Presenter: Cristian Adolfo.
ENCIT2012-237 NUMERICAL ANALYSIS AND OPTIMIZATION OF MIXERS - PDF
Jonathas Assunção Castro, Taygoara Felamingo de Oliveira, Carlos Humberto Llanos Quintero, UnB, Brazil
Abstract: The purpose of this paper is to present an analysis of the CNG-air mixers and propose their geometric optimization. The mixer is the section where mixing occurs and is associated with loss of pressure, generating increased emission of pollutants and loss of power in a combustion engine. It aims the development of a mixer with lower pressure drop and more homogeneous mixture. Through the numerical methodology is evaluated a conventional simulator. The velocity of the mixture increases with the Reynolds number, however, the quality of the mixture, ie, its homogeneity independs of the flow Reynolds, being dependent only of the geometry of the mix section .
Keywords:Openfoam; mixer; turbulence; orifice plate; compressed natural gas.
Presentation Schedule: NO PRESENTATION.
ENCIT2012-273 A STUDY OF BREAKING WAVE USING THE SMOOTHE PARTICLE HYDRODYNAMICS METHOD - PDF
José Gustavo Coelho, UFTM, Brazil
Taygoara Felamingo de Oliveira, Antonio Cesar Pinho Brasil Junior, UnB, Brazil
Pierre Maruzewski, EDF Group (France), France
Abstract: The flow in conditions of free surface has characteristics that make it difficult to simulate using the conventional numerical methods, like Finite Volume Method (FVM) or Finite Element Method (FEM). In this context, the Smoothed Particle Hydrodynamics (SPH) method is used to simulate the breaking waves. This is a Lagrangian and meshless method and the flow is divided into volume parts of fluid, using the concept of particles. The code was validated with experimental data and in the future, we intend to study the phenomenon of erosion by coupling the results obtained from the impacts of waves in coastal regions.
Keywords:SPH; meshless; wave; Lagrangian referencial.
Presentation Schedule: Tuesday, 17:20-17:40. Session: FMR4-3. Presenter: José Gustavo Coelho.
ENCIT2012-286 A NUMERICAL METHODOLOGY FOR PERMEABILITY DETERMINATION OF REINFORCEMENTS FOR POLYMERIC COMPOSITES - PDF
Jeferson Avila Souza, Liércio André Isoldi, Elizaldo Domingues dos Santos, Cristiano Peres Oliveira, FURG, Brazil
Sandro Campos Amico, UFRGS, Brazil
Abstract: This work focus on developing a numerical methodology for the determination of permeability of RTM reinforcements. The method allows the calculation of the three permeability components (Kxx, Kyy and Kzz) from a set of time dependent flow front coordinates data; one coordinate for each permeability component. An initial guess is set for the permeabilities and the difference between numerical and experimental values of flow front position at a specific time is minimized with the solution of an algebraic system of equations. Newton-Raphson method was used to solve the non-linear system of equations. The results presented in this paper were obtained for a rectilinear (1D) and a radial 2D problem, both with analytical solutions for the flow front position as a function of time. For the 1D comparison between the numerically calculated Kxx and the analytical value agreed within 1.7\% and, for the 2D radial problem, numerical and analytical values of Kxx and Kyy agreed within 1.3\%.
Keywords:RTM; Permeability; Numerical modeling.
Presentation Schedule: Monday, 15:40-16:00. Session: FMR4-1. Presenter: Jeferson Avila Souza.
ENCIT2012-085 NUMERICAL SIMULATION OF A DUMMY FOR EVALUATION OF THERMAL ENVIRONMENT - PDF
Fábio Alexandre Castelli, Anderson Morikasu Oshiro, Maurício Silva Ferreira, Guenther Carlos Krieger Filho, USP, Brazil
Abstract: In this paper results from CFD simulation and experimental results from literature are compared to validate a geometry for numerical evaluation of thermal environment. A female dummy is discretized into 16 segments: head, chest, back, pelvis, arms, forearms, hands, thighs, legs and feet. For sensitivity analysis a simple geometry with cylindrical segments and a more complex geometry are used. The experiment was conducted with the dummy in a sitting position inside a wind tunnel with controlled conditions: fixed temperature and flow velocity from zero (stagnation condition) to 5m/s. The dummy has superficial temperature control for heat transfer analysis. In numerical simulation the Navier-Stokes equations and the radiative transfer equation are solved. A two-equations turbulence model is used, as well as the enhanced wall treatment that adapts both coarse and refined meshes in the boundary layer region. All the grid used in this paper are unstructured and composed by tetrahedral elements. There are layers of prismatic elements near the surfaces of the dummy to improve the heat transfer calculation. The grid for cylindrical geometry (hear called the simple geometry) has approximately 2.5 million elements and the grid for complex geometry has approximately 3.2 million elements. The results show that the cylindrical geometry is sufficient to simulate the heat transfer by thermal convection and radiation. A more detailed geometry may not be advantageous due to the increased computational cost. The results also show that the adimensional y+ must be well controlled and the wall function must be well chosen.
Keywords:CFD; Heat transfer; Thermal manikin; Enclosed environment; Thermal comfort.
Presentation Schedule: Wednesday, 16:40-17:00. Session: FMR4-4. Presenter: Fábio Alexandre Castelli.
ENCIT2012-155 NUMERICAL SIMULATION OF SEA WAVE ENERGY CONVERTERS USING THE OPENFOAM SOFTWARE - PDF
Jeferson Avila Souza, Liércio André Isoldi, Elizaldo Domingues dos Santos, FURG, Brazil
Mateus das Neves Gomes, IFPR, Brazil
Luiz Alberto Oliveira Rocha, UFRGS, Brazil
Abstract: In this work OpenFOAM software is used to simulate the generation of regular gravity waves inside a rectangular tank. Interaction between the generated waves and an oscillating water column (OWC) device, used to convert wave energy into electrical energy, is also simulated. The main goal of this work is to develop a numerical strategy to simulate OWC converters using OpenFOAM. Obtained results for the regular wave generation were compared with analytical solution. Maximum errors of 10\% were observed between numerical and analytical results for the wave crest elevation. For the OWC device, it was investigated the influence of the lip, distance between the water mean level and the depth of submergence of the OWC, on the mass flow passing through the device's chimney. Results showed that for the wave climate tested, an increase in the lip length results into a decrease in the mass flow rate.
Keywords:Wave energy; OpenFOAM; Numerical Simulation; VOF.
Presentation Schedule: Wednesday, 14:20-14:40. Session: FMR4-4. Presenter: Jeferson Avila Souza.
ENCIT2012-070 APPLICATION OF THE COMPUTATIONAL MODELING IN THE RESIN TRANSFER MOLDING (RTM) PROCESS: A CASE STUDY OF A MARINE PROPELLER - PDF
Joseane da Silva Porto, Max Letzow, Elizaldo Domingues dos Santos, Jeferson Avila Souza, Liércio André Isoldi, FURG, Brazil
Sandro Campos Amico, UFRGS, Brazil
Abstract: This work presents how the computational modeling can help in the Resin Transfer Molding (RTM) process when it is applied to the production of parts with complex geometry, such as the marine propellers. This manufacture process of composite material parts consists in the injection of a polymeric resin into a closed mold where a fibrous reinforcement is previously placed. The numerical simulation of the RTM process, that can be considered as the resin flow through a porous media, was developed in the FLUENT package and was applied to study a propeller for naval propulsion. As the propeller has a complex format, the use of computational approach as a preliminar step in the manufacturing process is very important for the correct definition of the inlet and outlet nozzles. So, it is possible to design an efficient mold, avoinding extras costs related with the mold redesign, the resin waste and the increase of injection time. The preliminar results showed that an inadequate positioning of the mold outlet nozzles causes a significant increase (about 10\%) in the production time for obtaining the marine propeller by RTM process. Moreover, for the final version of this work, a discussion about the amount of the wasted resin due the inadequate localization of these outlet nozzles will be performed.
Keywords:Resin Transfer Molding (RTM); Polymeric Composite Materials; Computational Modeling; FLUENT.
Presentation Schedule: Wednesday, 16:00-16:20. Session: FMR4-4. Presenter: Jeferson Avila Souza.
ENCIT2012-071 SEMI-LAGRANGIAN ALGORITHMS FOR SECOND ORDER FOR THE STUDY OF HYDRODYNAMICS OF ELECTROCHEMICAL CELLS - PDF
Eberson Luis de Souza Moraes, UFRJ, Brazil
Gustavo Charles Peixoto de Oliveira, Gustavo Rabello dos Anjos, Norberto Mangiavacchi, UERJ, Brazil
José Miranda da Rocha Pontes, UFRJ, Brazil
Abstract: The problem of current oscillations in electrochemical cells using a rotating disk electrode has been addressed for more than 15 years by the Metallurgy and Materials Engineering Department of the Federal University of Rio de Janeiro. During these years, we developed a computational code that simulates the hydrodynamic behavior and obtained a good accuracy using the MINI element in domain discretization and a semi-Lagrangian algorithm of first order. This work is the implementation of the element SQUARED algorithm and a semi-Lagrangian second order in time in order to seek a more refined computational mesh and a simulation with more accurate results.
Keywords:Corrosion; Rotating Disk Flow; Second-Order Algorithms; Semi-Lagrangian Method; Finite Element Method.
Presentation Schedule: Wednesday, 15:40-16:00. Session: FMR4-4. Presenter: Eberson Luis de Souza Moraes.
ENCIT2012-112 FLOW PAST OVER CONFINED CYLINDER - COMPARISON BETWEEN IMMERSED BOUNDARY AND FINITE VOLUME METHOD - PDF
Felipe Pamplona Mariano, Andreia Aoyagui Nascimento, Ricardo Humberto de Oliveira Filho, Rhander Viana, Carlos Alberto de Almeida Vilela, UFG, Brazil
Abstract: The purpose of present paper is to show a comparison between Boundary Fitted Coordinate (BFC) and Immersed Boundary Method (IBM) for represent the boundary conditions of immersed geometry in flow. For this purpose, the confined flow over circular cylinder is performed and two-dimensional Navier-Stokes equations for incompressible and isothermal flows is solved using two different discretization methods, for to test the BFC the finite volume method with QUICK and Second Order Upwind discretization schemes is performed. For IBM investigations, Fourier pseudo-spectral method is carried. The streamline over the flow, pressure and drag coefficients and computational performance are campared.
Keywords:Immersed Boundary Method; Finite Volume Method; Pseudo-Spectral Method; Flow over confined cylinder; Boundary Fitted Coordinate.
Presentation Schedule: Wednesday, 14:40-15:00. Session: FMR4-4. Presenter: Felipe Pamplona Mariano.
ENCIT2012-283 NUMERICAL AND EXPERIMENTAL STUDY OF FLOW IN SMALL WIND TUNNEL TEST SECTION OPERATING WITH LOW SPEED - PDF
Cleide Barbosa Soares, CEFET-MG, Brazil
Sérgio de Morais Hanriot, Cristiana Brasil Maia, Luben Cabezaz-Gómes, Matheus Santos Guzella, Rodrigo Bruck Cunha, PUC-Minas, Brazil
Abstract: In the past years, several wind tunnels are being designed and built to measure aerodynamic forces and moments. It is observed that, even with the recent computational advances, wind tunnels are still an essential tool to the study of the aerodynamics. This paper presents a comparison between the two turbulence models: shear stress transport SST models and BSL Reynolds Stress, in the test section of a low speed wind tunnel. Experimental results were used as boundary conditions for simulations. An analysis of the behavior of the turbulence kinetic energy profile for both turbulence models was done. The comparison between the two turbulence models showed that the model BSL Reynolds Stress presents a more detailed airflow characteristics and best results for turbulence kinetic energy.
Keywords:wind tunnel; hot wire anemometry; CFD; kinetic energy.
Presentation Schedule: Thursday, 15:00-15:20. Session: FMR4-5. Presenter: Cleide Barbosa Soares.