LAMEC is the Computational Mechanics Laboratory of the Civil Engineering Program at COPPE/UFRJ, where work is done to develop numerical models to solve problems in Civil Engineering and related areas.

LAMEC’s research activities began in 1976 with Professors Webe João Mansur and José Claudio de Faria Telles, at which time the work focused on the development of models based on the Boundary Element Method (BEM). Until the early 1990s, the work carried out at LAMEC focused on the development of MEC formulations and algorithms for potential theory (Laplace and Poisson equations), for groundwater flow problems in the permanent regime (saturated medium or with a free surface) and transient regime, for the theory of elasticity and plasticity and for elastic and acoustic wave propagation problems.

Subsequently, new problems were also incorporated into developments with the Boundary Element Method, and other numerical methods (finite element and finite difference methods) also became part of the Laboratory’s routine.

Boundary Elements

Research in this area focuses on the development of new formulations and computational techniques for elastic, poroelastic and acoustic wave propagation, fracture mechanics, elasticity, plasticity, cathodic protection, etc.

• Computational efficiency and new formulations

• Fracture Mechanics

• Dynamic analysis in the time and frequency domain

• Plasticity

Numerical Methods in General

Research in this area focuses on the development and computational implementation of numerical techniques based on the Boundary Element, Finite Element and Finite Difference Methods for the solution of problems in engineering and related areas.

Numerical techniques:
Parallel processing on microcomputer clusters, iterative solvers, implicit and explicit schemes in the time domain and formulations in the frequency domain for acoustics, elastodynamics and poroelastodynamics.

• The finite difference and finite element methods for modeling acoustic wave propagation in anisotropic inhomogeneous poroelastic media, time marching schemes, “silent” contours, formulations in the frequency domain.

• Finite difference procedures for modeling wave propagation in inhomogeneous, anisotropic media: standard formulation, interleaved mesh, coupling between acoustic, elastic and poroelastic media, operators in space and time, “silent” contours.

• Procedures based on the finite element method for analyzing the propagation of elastic, acoustic and poroelastic waves: coupling between different media, performance of infinite elements, formulations in the frequency domain.

Applied Research

Geoacoustics

Seismic and acoustic wave propagation in the ocean

Objectives:

Training of professionals with solid knowledge of wave propagation for applications in the oil industry and various other areas of knowledge, with emphasis on the following topics: numerical modeling of seismic wave propagation, underwater acoustics and dynamic soil-structure interaction.

This master’s and doctoral program, whose emphasis is in the area of seismic and acoustic wave propagation and signals, is aimed at engineers, geophysicists, geologists, physicists, mathematicians and professionals working in related areas. Students have a wide range of subjects to choose from at COPPE.

Dynamic Soil-Structure Interaction

Finite elements and boundary elements are used to develop computer programs for the static and dynamic analysis of elastic, plastic, poroelastic, inhomogeneous poroelasto-plastic and anisotropic media. Interaction with the structure (linear or non-linear) and with fluids is considered.

Silent contours are considered in order to avoid artificial reflections in truncation contours of finite element meshes.

Formulations in the time and frequency domains are considered. The basic disciplines related to this topic are the same as those of the seismic modeling topic.

Seismic Modeling and Imaging

Geological structures capable of trapping oil: post-migration model

Research in this area focuses on the development of techniques based on MEC, MEF and MDF for applications in the oil and construction industries.

To date, the majority of case studies by the oil industry at international level use explicit MDF formulations. Developments related to implicit finite difference schemes and procedures based on MEC and MEF are being considered. Applications are aimed at modeling wave propagation in inhomogeneous, anisotropic, acoustic, elastic and poroelastic media. Formulations in the frequency domain are also being considered.

This line of development is, in principle, very close to that of Soil-Structure Interaction, and the basic disciplines are the same.

• Acoustic, elastic and poroelastic modeling

• Reverse Time Migration (RTM) 2D and 3D

• Reverse Time Migration (RTM) imaging condition

• Simulation of unconventional seismic surveys (seabed cable)

• Seismic surveys in regions with irregular topography

• Distribution of pressures due to the firing of the air cannon and interference with marine fauna

• Simulation of unconventional 3D and 4C seismic surveys

• Tomography applied to civil structures

Environmental Acoustics

This topic focuses on the development of computer programs based on the EF, DF and EC methods for modeling urban and underwater acoustics.

• Urban acoustics: acoustic barriers including soil absorption, interaction with thin panels, case studies in urban environments

• Sound propagation in shallow and deep waters and interference with marine fauna

• Numerical modeling in environmental damage and impact

Serra da Mesa dam detour structure – GO

Objectives:

• Training of professionals with generalized knowledge in numerical modeling of practical engineering problems. Special emphasis is given to the boundary element method and its applications to various problems in continuum mechanics.

• The scope of this line includes problems in the theory of elasticity, both linear and non-linear, geometric and physical, as well as applications to potential theory in general.

Fracture Mechanics

Simulating an elliptical crack in a thick-walled cylinder

In the theory of elasticity, applications to fracture mechanics generate some of the most difficult problems to solve numerically with adequate precision. The singular behavior of the stress fields in the vicinity of the crack tips, coupled with the discontinuity of the displacements across the crack surface (i.e. the so-called crack “openings”), are strongly responsible for this finding.

In this area, the Boundary Element Method (BEM) has been providing reliable results at a very competitive computational cost. However, the existence of two different surfaces sharing the same position in space produces a degeneration in the boundary integral equation, which can impose the continuity of displacements in the crack, if the limit is not taken correctly, or even a singularity in the matrix of the system of equations, if two different nodal points, one opposite the other, are on different surfaces.

In view of this, MEC cannot succeed in these specific applications without special devices being implemented to avoid these problems.

Currently, three alternative formulations are predominant:

1. Extension of the idea of sub-regions, where the crack surfaces appear as continuations of the interfaces, on which the conditions of compatibility and equilibrium are not imposed.

2. Introduction of the hypersingular equation (or surface force equation) on the contour, replacing the classical equation when the source point is located on one of the crack’s opposite surfaces.

3. Use of Green’s functions corresponding to the infinite medium already containing unloaded cracks of geometries identical to those of the problem to be solved.

This last alternative leads to a formulation where only the classical integral equation is used, without the need to place source points in the cracks, which contributes significantly to increasing the accuracy of the results, due to the lack of discretization in elements in the critical regions of the problem.

Thermal Fatigue

Temperature distribution

One of the concerns in a nuclear power plant is thermal stratification in pipes. The variation in temperature at a specific point or in different regions of the section induces variations in stresses that can result in cracks due to fatigue.

Therefore, a two-dimensional transient thermoelastic analysis of the thermal stratification problem using the Boundary Element Method becomes relevant, as does the evaluation of the fatigue that occurs in pipes subjected to this phenomenon.

As an application, the waste heat removal line of the primary circuit of the Angra 1 Power Plant was analyzed, where thermal stratification can occur due to temperature variations in the pipe section. The temperature profile on the outside of the pipe was provided by a monitoring system installed in some sections.

With the stress variations, a fatigue assessment was carried out for critical points, estimating the possibility of cracks and providing information to predict the need for corrective and preventive maintenance.

Cathodic protection

Electrochemical potential distribution on the P-48 Platform Vessel

Corrosion problems are frequent and occur in a wide range of activities, where economic losses and, above all, human lives must be avoided. These losses include the cost of replacing parts and equipment, accidental or maintenance stoppages, loss of efficiency, product contamination, project oversizing, among others.

Cathodic protection is one of the most widely used methods for combating corrosion and is applied to buried structures, submerged or in contact with electrolyte. Protection is achieved by reducing the electrode potential to the iron’s thermodynamic immunity domain by means of cathodic polarization, usually by impressed current or sacrificial anodes.

Although the fundamentals of cathodic protection are well known, the practice still represents a challenge in structures with complex geometry, such as offshore platforms, where the polarization potential can vary significantly on the metal surface.

Combining experimental results with numerical-computational techniques contributes significantly to improving design methodologies, especially in the context of the deepwater offshore industry.

The modeling of cathodic protection systems requires the consideration of time-varying polarization curves that are distinct for different regions of the structure.

Computational techniques allow the analysis of two-dimensional, axisymmetric and three-dimensional problems described by Laplace’s equation, making it possible to calculate the electrochemical potential distribution and current density at the structure/electrolyte interface.

Acoustics

Underwater Acoustics

This research project aims to develop numerical models in the frequency domain to simulate the propagation of acoustic waves in shallow water along irregular surfaces, considering constant velocity and the seabed as a rigid surface.

For constant depths, the fundamental solutions already incorporate the boundary conditions on the surface and bottom, avoiding discretization.

Acoustics in Wind Farms

The use of alternative energies, such as wind power, has become viable in the face of the energy crisis and the need to diversify the energy matrix.

In wind farms, the emission of acoustic noise is a limiting factor in configuration, and it is necessary to assess the appropriate distance from residential areas by means of acoustic prognostics.

The aim of this project is to numerically model the noise generated by wind turbines in wind farms using the boundary element method.

Acoustic Barriers

On streets and highways with heavy traffic, noise emissions can be harmful to the health of neighboring populations.

Studies can be carried out by means of numerical simulations using the boundary element method, with the aim of minimizing the harmful effects of environmental noise.