Eugenio Oñate

• Ph.D., Ms.C
• Executive Vicepresident and Director of CIMNE at CIMNE - Centre Internacional de Metodes Numerics en Enginyeria, Barcelona, Spain

This work presents a data-driven continuum–discrete multiscale methodology to simulate heat transfer through granular materials. The two scales are hierarchically coupled, where the effective thermal conductivity tensor required by the continuous method at the macroscale is obtained from offline microscale analyses. A set of granular media samples...

Database of the dimensionless components of the effective thermal conductivity tensor (Kxx, Kyy, and Kxy) for a given porosity and fabric, generated from the homogenization of DEM solutions in several Representative Volume Elements (RVEs).

This work presents an enhanced version of the semi-explicit particle finite element method for incompressible flow problems. This goal is achieved by improving the methodology that results from applying the Strang splitting operator by adding an acceleration term. The advective step is evaluated on the mesh considering the new term leading to a mor...

The methodology previously proposed by the authors to solve particle-laden turbulent flows through a multiscale approach is extended by introducing a continuous function for the dispersed phase concentration. The proposed continuous model is especially useful for studying the motion of particle streams in which gravitational and inertial effects ca...

The behavior of the cable jacket in fire characterized by the tendency to melt and drip constitutes a major source of fire hazard. The reason is that the melted material may convey the flame from one point to another, expanding fire and contributing to the fire load. In this article, the capability of a new computational strategy based on the parti...

We present an overview of the Pseudo-Direct Numerical Simulation (P-DNS in short) method for the solution of multi-scale phenomena. The method can be seen as an adaptation of the variational multi-scale (VMS) method, where the fine solution is solved numerically instead of analytically. Also, from the point of view of homogenization methods it can...

Many polymer-made objects show a trend of melting and dripping in fire, a behavior that may be modified by adding flame retardants (FRs). These affect materials properties, e.g., heat absorption and viscosity. In this paper, the effect of a flame retardant on the fire behavior of polymers in the UL 94 scenario is studied. This goal is achieved esse...

We present a Lagrangian nodal integration method for the simulation of Newtonian and non-Newtonian free-surface fluid flows. The proposed nodal Lagrangian method uses a finite element mesh to discretize the computational domain and to define the (linear) shape functions for the unknown nodal variables, as in the standard Particle Finite Element Met...

Conventional and high-speed train lines are being constructed all over the world with the objective of improving the mobility of both people and goods. Most of these infrastructures are built with railway ballast, a granular material whose main functions are resisting train loads and facing climate actions. The growth in popularity of railway infr...

Rail transport, both for people and goods, is becoming increasingly significant all over the world, which is reflected in the great growth of conventional and high-speed train lines. Most of these infrastructures are built with railway ballast, a granular material whose main functions are to resist vertical and horizontal loads and to face climatic...

Two versions of a monolithic ALE FSI model (unified and mixed-kinematics) proposed and applied to biomechanics problems.

In this work a stabilized mixed formulation for the solution of non-linear solid mechanics problems in nearly-incompressible conditions is presented. In order to deal with high material deformation, an implicit Material Point Method is chosen. Such choice allows avoiding the classical limitations of the Finite Element Method, e.g., element tangling...

Presentation about the last advances in the modelling of railway ballast using the Discrete Element Method.

The tendency of the polymers to melt and drip when they are exposed to external heat source play a very important role in the ignition and the spread of fire. Numerical simulation is a promising methodology for predicting this behaviour. In this paper, a computational procedure that aims at analyzing the combustion, melting and flame spread of poly...

Aircraft emission targets worldwide and their climatic effects have put pressure in government agencies, aircraft manufacturers and airlines to reduce water vapour, carbon dioxide (\(CO_{2}\)) and oxides of nitrogen (\(NO_{x}\)) resulting from aircraft emissions. The difficulty of reducing emissions including water vapor, carbon dioxide (\(CO_{2}\)...

In this chapter we present recent advances on the Discrete Element Method (DEM) and on the coupling of the DEM with the Finite Element Method (FEM) for solving a variety of problems in non linear solid mechanics involving damage, plasticity and multifracture situations.

The main objective of this work lies in the development of a variational implicit Material Point Method (MPM), implemented in the open source Kratos Multiphysics framework. The ability of the MPM technique to solve large displacement and large deformation problems is widely recognised and its use ranges over many problems in industrial and civil en...

This paper extends to three dimensions (3D), the computational technique developed by the authors in 2D for predicting the onset and evolution of fracture in a finite element mesh in a simple manner based on combining the finite element method and the discrete element method (DEM) approach (Zárate and Oñate in Comput Part Mech 2(3):301–314, 2015)....

This chapter presents an overview of some computational methods for the analysis of problems in ship hydrodynamics. Attention is focused on the description of stabilized finite element formulations derived via a finite increment calculus (FIC) procedure. Both arbitrary Lagrangian–Eulerian (ALE) and fully Lagrangian forms are presented. Details of t...

Particle methods in computational fluid dynamics (CFD) are numerical tools for the solution of the equations of fluid dynamics, obtained by replacing the fluid continuum with a finite set of particles. One of the key attributes of particle methods is that pure advection is treated exactly. The convection of properties eases the solution of multi‐ma...

In this paper we analyze the capabilities of two numerical techniques based on DEM and FEM–DEM approaches for the simulation of fracture in shale rock caused by a pulse of pressure. We have studied the evolution of fracture in several fracture scenarios related to the initial stress state in the soil or the pressure pulse peak. Fracture length and...

Fluid-structure interaction modeling involving multi-fluids and membranes

Some important infrastructures like roads, railway tracks or dams were constructed in places threatened by natural hazards. With the purpose of preserving these infrastructures from landslides and rock-falls, different containment systems are installed, and one of the most popular are the flexible metallic fences [1]. The development of full-scale...

Railway ballast is a layer of granular material that resists to vertical and horizontal loads, produced by the passing train over the rail. The calculation of this kind of complex geomechanic problems has been traditionally addressed using refined constitutive models, based in continuum assumptions. Although these models may be suitable in the eval...

Double curvature arch dams feature geometrical complexity with a significant amount of parameters involved. Different criteria exist to assist in the design task, from simplified geometrical approaches to optimization procedures. However, most of them present a lack of flexibility and are not integrated in computer-aided design tools. In this contr...

The static and seismic analysis of Janneh arch-gravity dam (157 m) is carried out by considering a combination of self-weight, hydrostatic, uplift and seismic loads. Linear and nonlinear analyses are performed for both static and seismic cases. Nonlinear behavior is studied by means of joint elements in the contact between the rock foundation and t...

In this paper we present an accurate stabilized FIC-FEM formulation for the multidimensional steady-state advection–diffusion–absorption equation. The stabilized formulation is based on the Galerkin FEM solution of the governing differential equations derived via the Finite Increment Calculus (FIC) method using two stabilization parameters. The val...

The aim of this paper is to present a Lagrangian formulation for thermo-coupled fluid–structure interaction (FSI) problems and to show its applicability to the simulation of hypothetical scenarios of a nuclear core melt accident. During this emergency situation, an extremely hot and radioactive lava-like material, the corium, is generated by the me...

Fast and accurate Lagrangian finite element model for solving Navier-Stokes equations

The Discrete Element Method (DEM) was found to be an effective numerical method for the calculation of engineering problems involving granular materials. However, the representation of irregular particles using the DEM is a very challenging issue, leading to different geometrical approaches. This document presents a new insight in the application o...

In this paper we present an overview of the possibilities of the finite increment calculus (FIC) approach for deriving computational methods in mechanics with improved numerical properties for stability and accuracy. The basic concepts of the FIC procedure are presented in its application to problems of advection-diffusion-reaction, fluid mechanics...

We present a new stabilized finite element (FEM) formulation for incompressible flows based on the Finite Increment Calculus (FIC) framework (Oñate, 1998). In comparison to existing FIC approaches for fluids, this formulation involves a new term in the momentum equation, which introduces non-isotropic dissipation in the direction of velocity gradie...

Introduction and Objectives: An adequate artificial bladder is still a challenge to overcome. The computational model presented here intends to assist the conception of artificial solutions for bladder replacement. The numerical model for the urinary bladder was implemented using Finite Element Method, taking into account anatomical morphometry of...

We present three velocity-based Updated Lagrangian formulations for standard and quasi-incompressible hypoelastic-plastic solids. Three finite elements, named V, VP and VPS elements are derived and tested for benchmark for non-linear solid mechanics problems. The V-element is based on a standard velocity approach, while for the VP and VPS elements...

We propose here a numerical model for a three-dimensional simulation of glass forming processes. Using the basic philosophy of the Particle Finite Element method (PFEM), we introduce several new features adapting the strategy to suit the problem of interest. A modified fractional step method for the solution of the flow equations is applied. This a...

The development of overtopping protection systems often requires detailed analyses of complex physical phenomena. This hinders the comprehensive knowledge of their behavior, and therefore the development of suitable design criteria. In recent years, the authors have developed and validated different methods, combining continuous, particle and disc...

The solid-shells are an attractive kind of element for the simulation of forming processes, due to the fact that any kind of generic 3D constitutive law can be employed without any additional hypothesis. The present work consists in the improvement of a triangular prism solid-shell originally developed by Flores[2, 3]. The solid-shell can be used i...

Many countries are implementing new dam safety regulations that often include more restrictive standards. This, together with the increasing average age of dams, results in a greater need for dam control and maintenance works. The advances in information and communications technologies improved the performance of dam monitoring systems, so a large...

The development of high-speed train lines has increased during the last twenty years, leading to more demanding loads in railway infrastructures. For these reasons, the implementation of a numerical tool for the calculation of railway ballast behaviour has been found useful, as it will enables design optimization. Regarding the numerical method, th...

Dam bottom outlets play a vital role in dam operation and safety, as they allow controlling the water surface elevation below the spillway level. For partial openings, water flows under the gate lip at high velocity and drags the air downstream of the gate, which may cause damages due to cavitation and vibration. The convenience of installing air v...

A new mixed displacement-pressure element for solving solid–pore fluid interaction problems is presented. In the resulting coupled system of equations, the balance of momentum equation remains unaltered, while the mass balance equation for the pore fluid is stabilized with the inclusion of higher-order terms multiplied by arbitrary dimensions in sp...

Progressive fracture in quasi-brittle materials is often treated via strain softening models in continuum damage mechanics. Such constitutive relations favour spurious strain localization and ill-posedness of boundary value problems. The introduction of non-local damage models together with a characteristic length parameter controlling the size of...

Predictive models are essential in dam safety assessment. They have been traditionally based on simple statistical tools such as the hydrostatic-season-time (HST) model. These tools are well known to have limitations in terms of accuracy and reliability. In the recent years, the examples of application of machine learning and related techniques are...

In previous works [S. R. Idelsohn, J. Marti, P. Becker, E. O nate, Analysis of multifluid flows with large time steps using the particle

In this work, we present a new methodology for the treatment of the contact interaction between rigid boundaries and spherical discrete elements (DE). Rigid body parts are present in most of large-scale simulations. The surfaces of the rigid parts are commonly meshed with a finite element-like (FE) discretization. The contact detection and calculat...

We present a procedure for coupling the finite element method (FEM) and the discrete element method (DEM) for analysis of the motion of particles in non-Newtonian fluids. Particles are assumed to be spherical and immersed in the fluid mesh. A new method for computing the drag force on the particles in a non-Newtonian fluid is presented. A drag forc...

A modular discrete element framework is presented for large-scale simulations of industrial grain-handling systems. Our framework enables us to simulate a markedly larger number of particles than previous studies, thereby allowing for efficient and more realistic process simulations. This is achieved by partitioning the particle dynamics into disti...

Trends in Computational Mechanics that may have Future.

The authors present results on the use of the discrete element method (DEM) for the simulation of drilling processes typical in the oil and gas exploration industry. The numerical method uses advanced DEM techniques using a local definition of the DEM parameters and combined FEM-DEM procedures. This paper presents a step-by-step procedure to build...

In this paper, an adjoint-based error estimation and mesh adaptation framework is developed for the compressible inviscid flows. The algorithm employs the Finite Calculus (FIC) scheme for the numerical solution of the flow and discrete adjoint equations in the context of the Galerkin finite element method (FEM) on triangular grids. The FIC scheme t...

We present a Lagrangian monolithic strategy for solving fluid-structure interaction (FSI) problems. The formulation is called Unified because fluids and solids are solved using the same solution scheme and unknown variables. The method is based on a mixed velocity-pressure formulation. Each time step increment is solved via an iterative partitioned...

This article (author's post-print) is available at my website: http://nadukandi.es/publications.html In this paper we present an accurate stabilized FIC-FEM formulation for the 1D advection-diffusion-reaction equation in the exponential and propagation regimes using two stabilization parameters. Both the steady-state and transient solutions are co...

This paper presents a new computational technique for predicting the onset and evolution of fracture in a continuum in a simple manner combining the finite element method (FEM) and the discrete element method (DEM). Onset of cracking at a point is governed by a simple damage model. Once a crack is detected at an element side in the FE mesh, discret...

We present a new 2-noded beam element based on the refined zigzag theory and the classical Euler-Bernoulli beam theory for the static analysis of composite laminate and sandwich beams. The proposed element is able to take into account distortion effects due to shear elastic strains and can predict delamination. The element has four degrees of freed...

Purpose – Continuum-based discrete element method is an explicit numerical method, which is a combination of block discrete element method (DEM) and FEM. When simulating large deformation problems, such as cutting, blasting, water-like material flowing, the distortion of elements will lead to no convergence of the numerical system. To solve the con...

This paper presents a local constitutive model for modelling the linear and non linear behavior of soft and hard cohesive materials with the discrete element method (DEM). We present the results obtained in the analysis with the DEM of cylindrical samples of cement, concrete and shale rock materials under a uniaxial compressive strength test, diffe...

A new implicit stabilized formulation for the numerical solution of the compressible Navier-Stokes equations is presented. The method is based on the finite calculus (FIC) scheme using the Galerkin finite element method (FEM) on triangular grids. Via the FIC formulation, two stabilization terms, called streamline term and transverse term, are added...

The contact problem where particles and solids are involved is of great interest in the industry with many possible applications. One of these applications is the contact of tires on a particulate soil with gravel or sand; in this case, the Finite Element Method is used for the solution of the solids while the Discrete Element Method turns to be a...

RESUMEN Los avances en los instrumentos de medida y en las técnicas de transmisión y almacenamiento de información han permitido aumentar el control de la seguridad de las presas, con medidas más fiables, precisas y frecuentes. En general, estos avances no han sido acompañados por una mejora en las técnicas de tratamiento y análisis de los datos de...

In the last decades, the technology of dam protection has undergone major advancements. The increasing demand for safety in modern society has created the need for cost-effective measures to protect critical infrastructure such as dams. This situation has resulted in the drafting of new regulations and technical manuals in countries like Norway, Sw...

Water management is one of the key factors in Proton Exchange Fuel Cell (PEFC) performance. The water produced within the fuel cell is evacuated through the gas channels, but at high current densities water can block the channel, thus limiting the current density generated in the fuel cell. A semi-analytical model of a water droplet emerging from a...

The aim of the present work is to present an overview of some numerical procedures for the simulation of free surface flows within a porous structure. A particular algorithm developed by the authors for solving this type of problems is presented. A modified form of the classical Navier–Stokes equations is proposed, with the principal aim of simulat...

The purpose of this paper is to study the effect of the bulk modulus on the iterative solution of free surface quasi-incompressible fluids using a mixed partitioned scheme. A practical rule to set up the value of a pseudo-bulk modulus a priori in the tangent bulk stiffness matrix for improving the conditioning of the linear system of algebraic equa...

This paper presents the work carried out during the last years for the creation of a numerical model to simulate transient seepage phenomena in rockfill dams when overtopping occurs. The objective is to analyze the trigger of failure mechanism in the downstream slope due to hydrodynamic forces. The current work aims to give a contribution to thi...

A reduced-order model for an efficient analysis of cardiovascular hemodynamics problems using multiscale approach is presented in this work. Starting from a patient-specific computational mesh obtained by medical imaging techniques, an analysis methodology based on a two-step automatic procedure is proposed. First a coupled 1D-3D Finite Element Sim...

Multifluids are those fluids in which their physical properties (viscosity or density) vary internally and abruptly forming internal interfaces that introduce a large nonlinearity in the Navier–Stokes equations. For this reason, standard numerical methods require very small time steps in order to solve accurately the internal interface position. In...

Design of two-dimensional supersonic diffusers as a part of the wind tunnel is investigated in this paper. A methodology based on the mixture of try-and-error method and optimization algorithm is developed to handle the design problem. In the first design step, using try-and-error approach, the main parameters related to the geometry of diffuser su...

We present a generalized Lagrangian formulation for analysis of industrial forming processes involving thermally coupled interactions between deformable continua. The governing equations for the deformable bodies are written in a unified manner that holds both for fluids and solids. The success of the formulation lays on a residual-based expression...

Purpose – The purpose of this paper is to describe a set of simple yet effective, numerical method for the design and evaluation of parachute-payload system. The developments include a coupled fluid-structural solver for unsteady simulations of ram-air type parachutes. The main features of the computational tools are described and several numerical...

An experimental and numerical investigation of the effect of bisphenol A bis(diphenyl phosphate) (BDP) and polytetrafluoroethylene (PTFE) on the fire behaviour of bisphenol A polycarbonate/acrylonitrile butadiene styrene (PC/ABS) in the vertical UL 94 scenario is presented. Four PC/ABS blends were discussed, which satisfy different UL 94 classifica...

The paper presents a systematically numerical procedure based on the finite-element method for three-dimensional analysis of segmentally constructed prestressed concrete bridges using hexahedral elements including realistic tendon profiles. The enhanced assumed strain (EAS) is used in the formulation of the hexahedral element in order to improve th...

We present a Lagrangian numerical technique for the analysis of flows incorporating physical particles of different sizes. The numerical approach is based on the particle finite element method (PFEM) which blends concepts from particle-based techniques and the FEM. The basis of the Lagrangian formulation for particulate flows and the procedure for...

This paper aims at the development of a new stabilization formulation based on the finite calculus (FIC) scheme for solving the Euler equations using the Galerkin FEM on unstructured triangular grids. The FIC method is based on expressing the balance of fluxes in a space–time domain of finite size. It is used to prevent the creation of instabilitie...

SUMMARY We present a Lagrangian formulation for finite element analysis of quasi-incompressible fluids that has excellent mass preservation features. The success of the formulation lays on a new residual-based stabilized expression of the mass balance equation obtained using the finite calculus method. The governing equations are discretized with t...

Water management is a key limiting factor of Polymer Electrolyte Membrane fuel cells (PEMFC). At high current densities, liquid water accumulation in the electrode and channel can severely limit fuel cell performance. Liquid water produced during operation can block the channel leading to channel blockage and reactant maldistribution [1]. Droplet...

SUMMARYA finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind‐biased discretization of the Euler equations, written in arbitrary Lagrangian–Eulerian form and integrated in time by means of a dual‐time steeping technique. In order to exploi...

A numerical method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated plate/shell structures is presented. The originality of this method is the use of 4-noded quadrilateral plate finite elements whit only seven variables per node to discretize the plate/shell geometry. The ability to capture the relative displace...

In this paper, "finite point method" (FPM) is presented for modeling 2D shallow water flow problem. The method is based on the use of a weighted least-square approximation procedure, incorporating QR factorization and an iterative adjustment of local approximation parameters. The stabilization of the convective term in this present work is derived...

A new bilinear four-noded quadrilateral element (called quadrilateral linear refined zigzag) for the analysis of composite laminated and sandwich plates/shells based on the refined zigzag theory is presented. The element has seven kinematic variables per node. Shear locking is avoided by introducing an assumed linear shear strain field. The perform...

The paper focuses on the analysis of radial-gated spillways, which is carried out by the solution of a numerical model based on the finite element method (FEM). The Oliana Dam is considered as a case study and the discharge capacity is predicted both by the application of a level-set-based free-surface solver and by the use of traditional empirical...

Many structures have uniform geometry in a particular “prismatic” direction. Examples are plates and bridges with rectangular or curved plant. Also the meridional section of an axisymmetric shell does not change along the circumference (Figure 11.1). The name prismatic structure will refer hereonwards to a structure with uniform geometrical and mat...

Strength performance and weight advantages of composite materials versus traditional concrete and steel have led to their sustained and increased applications in aircraft and aerospace vehicles, automotive, naval and civil structures. The design of efficient and reliable composite structures however requires improved computational methods that accu...

Kirchhoff plate elements studied in the previous chapter are restricted to thin plate situations only (thickness/average side ≤ 0.10). Also the C 1 continuity requirement for Kirchhoff elements poses severe difficulties for deriving a conforming deflection field. These problems can be overcome by using the plate formulation due to Reissner [Re] and...

A three-dimensional (3D) beam, also called a rod, is a member that carries axial, flexural (shear and bending) and torsion force resultants. Structures containing 3D beams are found in frames of buildings and industrial constructions, arches, stiffened shells, structural parts in land transport vehicles, fusselages of airplanes and spacecrafts, shi...

This chapter studies the bending of slender plane beams using the classical Euler-Bernoulli beam theory and the FEM. Many readers will ask themselves why we are applying the FEM to a simple structural problem that can be solved by standard Strength of Materials techniques [Ti2]. The answer is that the study of beam elements is of great interest as...

A shell can be seen, in essence, as the extension of a plate to a nonplanar surface. The non-coplanarity introduces axial (membrane) forces in addition to flexural (bending and shear) forces, thus providing a higher overall structural strength.

High-performance and lightweight characteristics of composite materials have motivated a wide range of applications of these materials in aeronautic and space vehicles and in naval, automotive and civil structures, among other fields [Bar2,BC,Mar,TH4,Ts,Wh]. The development of costeffective and reliable composite laminated structures requires advan...

This chapter studies Timoshenko plane beam elements. Timoshenko beam theory accounts for the effect of transverse shear deformation. Timoshenko beam elements are therefore applicable for “thick” beams \(\left(\lambda = \frac{L}{h} where transverse shear deformation has an influence in the solution, as well as for slender beams \((\lambda > 100)\) w...

This chapter introduces the study of structures formed by “thin surfaces” such as plates and shells. Plates will be studied in this and the two following chapters. Shell structures formed by assembly of flat plates will be considered in Chapter 8. Axisymmetric shells will be treated in Chapter 9. Finally, the more general case of curved shell struc...

We present in this chapter the implementation of several of the elements for beam, plate and shell analysis studied in this book in the MAT-fem code environment written using the MATLAB® and GiD programming tools [On4]. MAT-fem includes several codes for FEM analysis of different structures.

Many shell structures of practical interest have axisymmetric forms. Examples are water and oil tanks, grain silos, cooling towers, nuclear containment shells, spherical and conical roofs and other structures outside the civil construction industry such as pressure vessels, missiles, airplane and spacecraft fuselages, etc. (Figure 9.1).

This chapter studies the derivation of curved shell elements for analysis of shells of arbitrary shape. Curved shell elements are an alternative to the “flat” shell elements studied in Chapter 8 and their formulation is interesting both from the theoretical and practical points of view.

We propose a fully Lagrangian monolithic system for the simulation of the underwater implosion of cylindrical aluminum containers. A variationally stabilized form of the Lagrangian shock hydrodynamics is exploited to deal with the ultrahigh compression shock waves that travel in both air and water domains. The aluminum cylinder, which separates the...