Begell House Inc.
Hybrid Methods in Engineering
HME
1099-2391
1
4
1999
SIMULATION OF COPENHAGEN TRACER DIFFUSION EXPERIMENT BY MEANS OF A LAGRANGIAN PARTICLE MODEL
19
J. C.
Carvalho
Institute Nacional de Pesquisas Espaciais (INPE), Caixa Postal 515, 12201-970 São José dos Campos - SP, Brazil
Gervasio Annes
Degrazia
Departamento de Fisica, Universidade Federal de Santa Maria, Santa Maria; Consiglio Nazionale delle Ricerche, lstituto di Cosmo-Geofisica, Torino, Italy; and Universidade de Sao Paulo, Institute Astrondmico e Geofisico, Sao Paulo, Brazil
Domenico
Anfossi
Istituto di Cosmogeofisica del CNR, Corso Fiume4, 10133, Torino, Italy
S. Trini
Castelli
Istituto di Cosmogeofisica del CNR, Corso Fiume4, 10133, Torino, Italy
Using simulations with a stochastic Lagrangian model of turbulent diffusion, we have studied the dispersion of contaminants in the atmospheric boundary layer when both thermal and mechanical turbulent forcing terms are present. The model is based on a generalized form of the Langevin equation and in the vertical direction the probability density function (PDF) is non-Gaussian and represented by two different PDFs. By employing the Copenhagen tracer diffusion experiment, the model performances are evaluated against observed ground-level concentrations.
ON THE COMPUTATIONAL PERFORMANCE OF GENERALIZED INTEGRAL TRANSFORM SOLUTIONS
10
Alcino Resende
Almeida
Petrobras Research Center, DIPLOT/SEPROT, Ilha do Fundao Quadra 7, Rio de Janeiro, Brazil
Integral transform solutions of convective-diffusive problems are examined and some computational enhancements are analyzed, in connection with the one-dimensional viscous Burgers equation with a periodic initial condition. The drastic influence of quadratures on the final numerical cost is established and guidelines on the extension of the optimizations to more involved situations are presented. A numerical experiment leading the solution of a viscous Burguers equation toward its inviscid (hyperbolic) counterpart is also performed.
A PROJECTION METHOD COMBINED WITH A FINITE-VOLUME METHOD FOR UNSTEADY NAVIER-STOKES EQUATIONS COMPARED WITH BENCHMARK SOLUTIONS
26
J. E. Rengel
Hernandez
Department of Mechanical Engineering, University of Oriente, Puerto La Cruz, Anzodtegui, Venezuela
Sergio Hamilton
Sphaier
Ocean Engineering Department - EP/COPPE/UFRJ, CP50508, 21945-970, Rio de Janeiro, RJ, Brazil
The advance in the development of numerical methods in fluid flow problems is evident. Finite-difference, finite-volume, finite-element, spectral, and spectral element methods and generalized integral transform techniques are some of them to be mentioned. Nevertheless, limitations and difficulties persist. Herein one looks for the development of a procedure to simulate fluid problems in ocean engineering, in particular, vortex-induced vibrations due to the incidence of ocean currents about risers when installed in floating systems in deep waters to pipe oil from the sea floor to free surface equipment.
Having this objective, a numerical procedure to simulate the flow of incompressible viscous fluids around two-dimensional bluff bodies is presented. It is based on the projection method [1], combined with a finite-volume scheme in curvilinear coordinates having as independent variables the Cartesian velocity and pressure. Due to its splitting characteristic independent of the spatial discretization, the projection method can be associated to different numerical methods for the Burgers and for the Poisson equations.
To verify the accuracy and the efficiency of the procedure presented, it is applied to three problems with existing benchmark solutions and some experimental results containing characteristics such as recirculation, separation, change of contour form, and open boundaries. These are the vortex shedding behind a circular cylinder, the lid-driven cavity, and the backward-facing step. Particularly the fluid flow about a circular cylinder has a variety of applications in many different branches of engineering. The numerical results agree very well with the benchmark solutions.
EXACT SOLUTION OF LUIKOV'S EQUATIONS FOR DRYING IN CAPILLARY POROUS MEDIA
24
S. M.
Guigon
Mechanical Engineering Department, EE/COPPE, Universidade Federal do Rio de Janeiro, Brasil
Lucilia Batista
Dantas
Research and Development Institute, IP&D / UNIVAP, Av. Shishima Hifumi, 2911, 12244-000, Sao Josedos Campos - SP; Mechanical Engineering Department, EE/COPPE, Universidade Federal do Rio de Janeiro, Brasil
F. Scofano
Neto
Mechanical Engineering Department, EE/COPPE, Universidade Federal do Rio de Janeiro, Brasil
Renato M.
Cotta
Laboratory of Nano- and Microfluidics and Microsystems, LabMEMS,
Mechanical Engineering Department and Nanotechnology Engineering Dept.,
POLI & COPPE, Universidade Federal do Rio de Janeiro, Cidade Universitária,
Cx. Postal 68503, Rio de Janeiro, RJ, CEP 21945-970, Brazil; Interdisciplinary Nucleus for Social Development—NIDES/CT, UFRJ, Brazil;
Mechanical Engineering Department, University College London, UCL, United
Kingdom
The classical formulation of drying in capillary porous media, based on Luikov's theory, is solved exactly through integral transformation. The associated eigenvalue problem, which has been recently found to yield complex roots that were not accounted for within most previous works, is accurately and automatically treated through the generalized integral transform technique (GITT). This approach allows for a definitive establishment of the eigenvalues spectra, including any number of complex eigenvalues, which appear for certain combinations of the governing parameters in the partial differential formulation. Representative examples are selected and the convergence characteristics of the exact solution are illustrated.
A NEW SOLUTION OF THE EXTENDED GRAETZ PROBLEM WITH AXIAL CONDUCTION AND VARIABLE WALL TEMPERATURE
12
G. Elmor
Filho
Departamento de Engenharia Quimica (DE-5), Institute Militar de Engenharia (IME); Curso de Pos-Graduacao em Tecnologia de Processos Quimicos e Bioquimicos (TPQB), Departamento de Engenharia Quimica, Escola de Quimica, Centre de Tecnologia, FURJ, Brazil
E. M.
Queiroz
Curso de Pas-Graduacao em Tecnologia de Processes Quimicos e Bioquimicos (TPQB), Departamento de Engenharia Quimica, Escola de Quimica, Bloco E, Centro de Tecnologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
Affonso Silva
Telles
Curso de Pos-Graduagao em Tecnologia de Processos Quimicos e Bioquimicos (TPQB), Departamento de Engenharia Quimica, Escola de Quimica, Centre de Tecnologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
An analytical solution for the extended Graetz problem with axial heat conduction is presented. The method is applicable to a fully developed flow in a circular tube subject to more general, first-kind wall boundary conditions as a function of the axial distance. The solution is generated using a convenient complete basis for the set of square integrable functions in R, orthogonal to the Hermite polynomials. Thus, the solution for the temperature profile is obtained by the infinite series of products of functions, resulting in the decomposition of the energy equation into a set of ordinary differential equations, each of which depends only upon the two previous equations. This fact allows the set to be solved successively. Representative curves illustrating the variations of the temperature surfaces, bulk temperature, heat flux, and Nusselt numbers with pertinent parameters are obtained.
FREE-CONVECTION BOUNDARY LAYERS AT A THREE-DIMENSIONAL STAGNATION POINT DRIVEN BY EXOTHERMIC SURFACE REACTIONS
18
Derek B.
Ingham
Centre for CFD, Department of Applied Mathematical Studies, The University of Leeds, Leeds, LS2 9JT, UK; Energy-2050, Faculty of Engineering, University of Sheffield, Sheffield, S10 2TN, UK
Simon D.
Harris
Rock Deformation Research, School of Earth Sciences, University of Leeds, Leeds, LS2 9JT, UK
Ioan
Pop
Department of Applied Mathematics, Babes-Bolyai University, 400084 Cluj-Napoca, Romania
The free-convection boundary-layer flow at a three-dimensional stagnation point of attachment on a curved surface, due to an exothermic catalytic chemical reaction on that surface, is considered in this article. Using a suitable transformation of variables, the governing equations are reduced to a standard free-convection problem and then solved numerically for appropriate ranges of the Prandtl and Schmidt numbers and the local curvature parameter. Bifurcation diagrams of the surface temperature and concentration as a function of the ambient temperature are analyzed.
EXPLICIT PERTURBATION SOLUTION OF A MASS STRUCTURED CELL POPULATION BALANCE MODEL
24
F. C.
Peixoto
Institute de Pesquisa e Desenvolvimento (IPD), Grupo de Quimica, Rio de Janeiro, Brazil, and Escola de Quimica, Centro de Tecnologia, UFRJ, Cidade Universitdria, Rio de Janeiro, Brazil
Cell cultures can be thought as a continuum of organisms, each of which goes through a cycle that includes birth, aging, reproduction, and death. The properties of each organism change during this cycle and one (or more) of these properties can be used to continuously characterize the individuals present in the culture, using a frequency distribution function. Rigorous models for this kind of mixture are called population balance equations. Due to their integro-partial differential form, these equations are considered difficult to solve analytically, and approximations or numerical approaches are usually employed. In the present work, an explicit solution to this kind of equation is found, with minimum loss of generality, using a perturbational procedure. Once the recurrence is obtained, the terms are expanded in an orthonormal basis to calculate the time evolution of the distributions.