Begell House Inc.
Hybrid Methods in Engineering
HME
1099-2391
3
1
2001
SIMULATION OF INFILTRATION IN POROUS MEDIUM BY LAPLACE TRANSFORM TECHNIQUE AND FINITE DIFFERENCE METHOD
9
E.
Wendland
Depto. de Hidráulica e Saneamento, Universidade de São Paulo, Caixa Postal 359, São Carlos-SP-Brasil, 13 560-970
Marco T.
Vilhena
Departamento de Engenharia Mecânica, Instituto de Matematica Aplicada, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
A hybrid method using the Laplace transform and the finite difference method has been considered to determine the wetting profile in a soil submitted to an infiltration process. This scheme has been applied to the case of a semi-infinite column of sand, satisfying the constant flux condition at the surface. The numerical results and the experimental water content profiles are in good agreement.
STUDY OF DIFFERENT TURBULENCE CLOSURE MODELS SIMULATING A NEUTRAL WIND TUNNEL FLOW EXPERIMENT
13
E.
Ferrero
Dipartimento di Scienze e Tecnologie Avanzate, Università del Piemonte Orientale, Corso T. Borsalino 54, 15100, Alessandria, Italy
S. Trini
Castelli
Istituto di Cosmogeofisica del CNR, Corso Fiume4, 10133, Torino, Italy
Domenico
Anfossi
Istituto di Cosmogeofisica del CNR, Corso Fiume4, 10133, Torino, Italy
S.
Finardi
Arianet s.r.l., VialeElvezia 42, 20052 Monza (MI), Italy
E. Di
Lisi
Dipartimento di Fisica Generale, Università di Torino, via Pietro Giuria 1, 10125, Torino, Italy
In this work, three different turbulence closure models, based both on a prognostic transport-diffusion equation and a diagnostic equation, are implemented in the fluid-dynamical model RAMS to simulate a neutral flow in a wind tunnel. The first closure model (E-l) solves the equation for turbulent kinetic energy only, whereas in the second (E-ε) and third (E-ε-l) models both the turbulent kinetic energy equation and the one for its dissipation rate ε are solved. In the E-l model, ε is provided by a diagnostic equation as a function of E and the mixing length l. The E-ε and E-ε-l models differ in the definition of the diffusion coefficient for the momentum Km. E-ε closure prescribes Km by means of the prognostic values of E and ε, whereas the E-ε-l model uses the mixing length concept. Different values for the empirical constants defining the mixing length are adopted. The turbulence models are tested against observed data on flat terrain. An example of application over a two-dimensional valley (U.S. Environmental Protection Agency—RUSVAL experiments) is also shown. Mean wind and turbulent kinetic energy vertical profiles both measured and calculated are shown and compared.
STOCHASTIC THIRD-ORDER HYBRID STRESS-BASED FINITE ELEMENT METHOD
27
Marcin
Kaminski
Faculty of Civil Engineering, Architecture and Environmental Engineering, Technical University of Lodz, Poland
This article discuses the application of the second-order perturbation, third probabilistic moment approach in the hybrid stress-based finite element analysis. The approach is demonstrated through the example of the linear elastic heterogeneous medium, where the additional stochastic finite element method discretization is based on the Airy, Prandtl, and Goursat stress functions. The numerical examples shown in the article illustrate the probabilistic stress state in some engineering structures with randomly varying material and geometrical parameters. The results obtained in the computational experiments can be directly used in the third-order reliability method analyses of various engineering problems having any closed-form mathematical or approximative numerical solutions.
A NEW NUMERICAL TECHNIQUE FOR TRANSPORTATION OF AIRBORNE PARTICLES
13
S. D.
Wright
The School of the Environment, University of Leeds, Leeds, LS2 9JT, England
Lionel
Elliott
Department of Applied Mathematical Studies, The University of Leeds, Leeds LS2 9JT, West Yorkshire, England.
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
It is great of importance to be able to predict the trajectories of airborne particles that are released from exhaust systems into the atmospheric boundary layer. These particles may disperse under favorable weather conditions, but under certain weather conditions, or as a result of the local topography, potentially hazardous levels of contamination may occur. In this article, the differential equations that govern the transport of these particles within the atmospheric boundary layer are considered and a numerical algorithm is devised to solve them efficiently. It will be shown that, unlike the transportation of particles over small scales, the efficient integration of the equations of motion is nontrivial without making certain simplifying assumptions.
A LINEAR PROGRAMMING MODEL FOR BOTTLENECK IDENTIFICATION IN CELLULAR MANUFACTURING
7
R. Y.
Qassim
Program of Mechanical Engineering, COPPE, Federal University of Rio de Janeiro, Brazil
L. G. Azevedo
Filho
Department of Mechanical Engineering, School of Engineering, Federal University of Rio de Janeiro, Brazil
The objective of this work is to demonstrate the error in assuming that exceptional elements (EEs) constitute bottlenecks in cellular manufacturing. This is achieved by developing a linear programming model and applying it to an example from industry.
SOLVING FLEXIBLE FLOW SHOP PROBLEMS BY COMBINING LPT AND GUPTA SCHEDULING ALGORITHMS
13
Tzung-Pei
Hong
Department of Information Management, I-Shou University, Kaohsiung, 84008, Taiwan, R. O. C.
Shyue-Liang
Wang
Department of Information Management, I-Shou University, Kaohsiung, 84008, Taiwan, R.O.C.
Chan-Lon
Wang
Department of Information Management, I-Shou University, Kaohsiung, 84008, Taiwan, R.O.C.
Scheduling is an important process widely used in manufacturing, production, management, computer science, and so on. Appropriate scheduling not only reduces manufacturing costs but also reduces possibilities for violating due dates. Finding good schedules for given sets of jobs can thus help factory supervisors effectively control job flows and provide solutions for job sequencing. In simple flow shop problems, each machine operation center includes just one machine. If at least one machine center includes more than one machine, the scheduling problem becomes a flexible flow shop problem. Flexible flow shops can thus be thought of as generalizations of simple flow shops. In the past, Sriskandarajah and Sethi [6] proposed a heuristic algorithm for solving flexible flow shop problems for two machine centers. In this article, we extend their algorithm to solve flexible flow shop problems for more than two machine centers. The heuristic Gupta algorithm is adopted as the kernel for achieving this purpose. Because this problem is a nondeterministic-polynomial (NP)-complete problem, optimal solutions seem unnecessary, especially when the number of jobs is large.
CONVERGENCE ACCELERATION OF INTEGRAL TRANSFORM SOLUTIONS
6
Mikhail D.
Mikhailov
Applied Mathematics Center, PO Box 384, Sofia, Technical University, Sofia, Bulgaria; and Mechanical Engineering Department—EE/COPPE/UFRJ, Universidade Federal do Rio de Janeiro, Cidade Universitaria, CP 68.503, Rio de Janeiro, RJ, 21945-970, 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
A number of techniques, intended to accelerate convergence of eigenseries solution, are investigated. The test problem describes transient temperature distribution along fins of constant profile. The solutions are presented in a form that permitted to work with time independent functions. For any solution are used as many terms as necessary to obtain 5 significant digits. It is shown that the splitting-up solution offers ideal convergence in contrast to the slowly convergent classical integral transform solution. The convergence of single filter solution, double filter solution, integral balance solution, and combined filtering and integral balance solution are acceptable for practical applications. It is demonstrated that the Shanks transformation may considerably accelerate the convergence of eigenseries solution.
A HYBRID SPECTRAL NODAL METHOD FOR ONE-SPEED DISCRETE ORDINATES EIGENVALUE PROBLEMS IN TWO-DIMENSIONAL CARTESIAN GEOMETRY
15
Hermes Alves
Filho
Instituto Politécnico—IPRJ, Universidade do Estado do Rio de Janeiro, UERJ, Caixa Postal 97282, 28601-970, Nova Friburgo, RJ, Brazil
Fernando Carvalho
Da Silva
Programa de Engenharia Nuclear—COPPE, Universidade Federal do Rio de Janeiro—UFRJ, Caixa Postal 68509, 21 945-970, Rio de Janeiro, RJ, Brazil
Ricardo C.
Barros
Instituto Politécnico—IPRJ, Universidade do Estado do Rio de Janeiro, UERJ, Caixa Postal 97282, 28601-970, Nova Friburgo, RJ, Brazil
We describe a hybrid spectral nodal method applied to one-speed SN eigenvalue problems in X, Y-geometry for nuclear reactor global calculations. To solve the transverse-integrated SN nodal equations, we generalize the spectral diamond (SD) method that we developed for numerically solving slab-geometry SN eigenvalue problems with no spatial truncation error. In the present generalization, we approximate the transverse leakage through the edges of each spatial node by constants, so we call our method the SD-constant nodal (SD-CN) method, which we use in the fuel regions of the nuclear reactor core. In the nonmultiplying regions, for example, reflector and baffle, we use the spectral Green's function-constant nodal (SGF-CN) method; hence the hybrid characteristic of our method. To converge the numerical solution for each SN fixed source problem (inner iterations) in each outer iteration (power method), we use the one-node block inversion (NBI) scheme. We show numerical results for two typical model problems to illustrate the method's accuracy in coarse-mesh calculations and to justify the hybrid characteristic of the numerical algorithm.