LaCàN - Laboratori de Càlcul Numèric
http://hdl.handle.net/2117/2072
2015-11-27T02:50:45ZApplications of numerical differentiation to computational plasticity
http://hdl.handle.net/2117/26511
Applications of numerical differentiation to computational plasticity
Pérez Foguet, Agustí; Rodríguez Ferran, Antonio; Huerta, Antonio
Report del Departament de Matemàtica Aplicada III - MA010
2015-02-25T13:30:29ZPérez Foguet, AgustíRodríguez Ferran, AntonioHuerta, AntonioModeling microwave drying of soils
http://hdl.handle.net/2117/26510
Modeling microwave drying of soils
Pérez Foguet, Agustí; Huerta, Antonio
Report del Departament de Matemàtica Aplicada III - MA009
2015-02-25T13:23:57ZPérez Foguet, AgustíHuerta, AntonioKey issues in computational geomechanics
http://hdl.handle.net/2117/26507
Key issues in computational geomechanics
Pérez Foguet, Agustí; Rodríguez Ferran, Antonio; Huerta, Antonio
2015-02-25T13:12:15ZPérez Foguet, AgustíRodríguez Ferran, AntonioHuerta, AntonioComputation of bounds for anchor problems in limit analysis and decomposition techniques
http://hdl.handle.net/2117/26454
Computation of bounds for anchor problems in limit analysis and decomposition techniques
Muñoz Romero, José; Rabiei, Syednima; Lyamin, Andrei; Huerta, Antonio
Numerical techniques for the computation of strict bounds in limit analyses
have been developed for more than thirty years. The efficiency of these techniques
have been substantially improved in the last ten years, and have been successfully
applied to academic problems, foundations and excavations. We here extend
the theoretical background to problems with anchors, interface conditions, and
joints. Those extensions are relevant for the analysis of retaining and anchored walls,
which we study in this work. The analysis of three-dimensional domains remains
as yet very scarce. From the computational standpoint, the memory requirements
and CPU time are exceedingly prohibitive when mesh adaptivity is employed. For
this reason, we also present here the application of decomposition techniques to
the optimisation problem of limit analysis. We discuss the performance of different
methodologies adopted in the literature for general optimisation problems, such as
primal and dual decomposition, and suggest some strategies that are suitable for the
parallelisation of large three-dimensional problems. The propo sed decomposition
techniques are tested against representative problems.
2015-02-20T15:55:43ZMuñoz Romero, JoséRabiei, SyednimaLyamin, AndreiHuerta, AntonioNumerical techniques for the computation of strict bounds in limit analyses
have been developed for more than thirty years. The efficiency of these techniques
have been substantially improved in the last ten years, and have been successfully
applied to academic problems, foundations and excavations. We here extend
the theoretical background to problems with anchors, interface conditions, and
joints. Those extensions are relevant for the analysis of retaining and anchored walls,
which we study in this work. The analysis of three-dimensional domains remains
as yet very scarce. From the computational standpoint, the memory requirements
and CPU time are exceedingly prohibitive when mesh adaptivity is employed. For
this reason, we also present here the application of decomposition techniques to
the optimisation problem of limit analysis. We discuss the performance of different
methodologies adopted in the literature for general optimisation problems, such as
primal and dual decomposition, and suggest some strategies that are suitable for the
parallelisation of large three-dimensional problems. The propo sed decomposition
techniques are tested against representative problems.Esquema adaptativo para problemas tridimensionales de convección-difusión
http://hdl.handle.net/2117/26367
Esquema adaptativo para problemas tridimensionales de convección-difusión
Monforte, Lluis; Pérez Foguet, Agustí
We present an adaptive scheme for three-dimensional convection-diffusion problems discretized by the Finite Element Method. The adaptive scheme is based on a remeshing strategy that applies a maximum volume constraint to the elements of a reference mesh. The remeshing can increase or decrease drastically the size of the elements in a single step automatically. With this strategy, the mesh quality does not deteriorate; as a consequence, the number of iterations required to solve the system of linear equations using iterative algorithms is kept constant. Two examples of very different characteristics are presented in order to analyze the proposal for a wide range of situations. The first is a three-dimensional extension of the Smolarkiewicz problem and the second is a simplified version of a point source pollutant transport problem. The results show the flexibility of the proposal. An optimal remeshing frequency, from a computational cost and accuracy of the results point of view, can be defined for both kinds of problems.
2015-02-16T14:14:57ZMonforte, LluisPérez Foguet, AgustíWe present an adaptive scheme for three-dimensional convection-diffusion problems discretized by the Finite Element Method. The adaptive scheme is based on a remeshing strategy that applies a maximum volume constraint to the elements of a reference mesh. The remeshing can increase or decrease drastically the size of the elements in a single step automatically. With this strategy, the mesh quality does not deteriorate; as a consequence, the number of iterations required to solve the system of linear equations using iterative algorithms is kept constant. Two examples of very different characteristics are presented in order to analyze the proposal for a wide range of situations. The first is a three-dimensional extension of the Smolarkiewicz problem and the second is a simplified version of a point source pollutant transport problem. The results show the flexibility of the proposal. An optimal remeshing frequency, from a computational cost and accuracy of the results point of view, can be defined for both kinds of problems.Arbitrary Lagrangian–Eulerian (ALE) formulation for hyperelastoplasticity
http://hdl.handle.net/2117/26359
Arbitrary Lagrangian–Eulerian (ALE) formulation for hyperelastoplasticity
Rodríguez Ferran, Antonio; Pérez Foguet, Agustí; Huerta, Antonio
The arbitrary Lagrangian–Eulerian (ALE) description in non-linear solid mechanics is nowadays stan-
dard for hypoelastic–plastic models. An extension to hyperelastic–plastic models is presented here.
A fractional-step method—a common choice in ALE analysis—is employed for time-marching: every
time-step is split into a Lagrangian phase, which accounts for material e>ects, and a convection phase,
where the relative motion between the material and the ?nite element mesh is considered. In contrast to
previous ALE formulations of hyperelasticity or hyperelastoplasticity, the deformed con?guration at the
beginning of the time-step, not the initial undeformed con?guration, is chosen as the reference con?g-
uration. As a consequence, convecting variables are required in the description of the elastic response.
This is not thecasein previous formulations, whereonly theplastic responsecontains convection
terms. In exchange for the extra convective terms, however, the proposed ALE approach has a major
advantage: only the quality of the mesh in the spatial domain must be ensured by the ALE remeshing
strategy; in previous formulations, it is also necessary to keep the distortion of the mesh in the material
domain under control. Thus, the full potential of the ALE description as an adaptive technique can be
exploited here. These aspects are illustrated in detail by means of three numerical examples: a necking
test, a coining test and a powder compaction tes
2015-02-16T09:40:36ZRodríguez Ferran, AntonioPérez Foguet, AgustíHuerta, AntonioThe arbitrary Lagrangian–Eulerian (ALE) description in non-linear solid mechanics is nowadays stan-
dard for hypoelastic–plastic models. An extension to hyperelastic–plastic models is presented here.
A fractional-step method—a common choice in ALE analysis—is employed for time-marching: every
time-step is split into a Lagrangian phase, which accounts for material e>ects, and a convection phase,
where the relative motion between the material and the ?nite element mesh is considered. In contrast to
previous ALE formulations of hyperelasticity or hyperelastoplasticity, the deformed con?guration at the
beginning of the time-step, not the initial undeformed con?guration, is chosen as the reference con?g-
uration. As a consequence, convecting variables are required in the description of the elastic response.
This is not thecasein previous formulations, whereonly theplastic responsecontains convection
terms. In exchange for the extra convective terms, however, the proposed ALE approach has a major
advantage: only the quality of the mesh in the spatial domain must be ensured by the ALE remeshing
strategy; in previous formulations, it is also necessary to keep the distortion of the mesh in the material
domain under control. Thus, the full potential of the ALE description as an adaptive technique can be
exploited here. These aspects are illustrated in detail by means of three numerical examples: a necking
test, a coining test and a powder compaction tesNumerical differentiation for local and global tangent operators in computational plasticity
http://hdl.handle.net/2117/26356
Numerical differentiation for local and global tangent operators in computational plasticity
Pérez Foguet, Agustí; Rodríguez Ferran, Antonio; Huerta, Antonio
In this paper, numerical di¿erentiation is applied to integrate plastic constitutive laws and to compute the corresponding consistent
tangent operators. The derivatives of the constitutive equations are approximated by means of di¿erence schemes. These derivatives are
needed to achieve quadratic convergence in the integration at Gauss-point level and in the solution of the boundary value problem.
Numerical di¿erentiation is shown to be a simple, robust and competitive alternative to analytical derivatives. Quadratic convergence
is maintained, provided that adequate schemes and stepsizes are chosen. This point is illustrated by means of some numerical
examples.
2015-02-16T09:16:20ZPérez Foguet, AgustíRodríguez Ferran, AntonioHuerta, AntonioIn this paper, numerical di¿erentiation is applied to integrate plastic constitutive laws and to compute the corresponding consistent
tangent operators. The derivatives of the constitutive equations are approximated by means of di¿erence schemes. These derivatives are
needed to achieve quadratic convergence in the integration at Gauss-point level and in the solution of the boundary value problem.
Numerical di¿erentiation is shown to be a simple, robust and competitive alternative to analytical derivatives. Quadratic convergence
is maintained, provided that adequate schemes and stepsizes are chosen. This point is illustrated by means of some numerical
examples.Implementing pro-poor policies in a decentralized context: the case of the Rural Water Supply and Sanitation Program in Tanzania
http://hdl.handle.net/2117/26354
Implementing pro-poor policies in a decentralized context: the case of the Rural Water Supply and Sanitation Program in Tanzania
Jiménez Fernández de Palencia, Alejandro; Pérez Foguet, Agustí
This paper examines the challenge of achieving
a balance between the implementation of centrally
designed pro-poor policies and the decentralization of
responsibilities to local governments in many African
countries. It analyzes the implementation of the Rural
Water Supply and Sanitation Program in Tanzania. Key
mechanisms for planning and allocating resources are
analyzed at ministry, district, and village levels. Results
show that a mixture of policy incoherencies, technical
shortcomings and political influence determine that only a
small proportion of funds reaches the underserved areas.
We argue that a greater connection between the bottom-up
and top-down planning mechanisms, and a sharp increase
of downwards accountability are needed before decentral-
ized decision-making result in better resources allocation.
Meanwhile a bigger intervention from central government
is needed.
2015-02-16T09:06:23ZJiménez Fernández de Palencia, AlejandroPérez Foguet, AgustíThis paper examines the challenge of achieving
a balance between the implementation of centrally
designed pro-poor policies and the decentralization of
responsibilities to local governments in many African
countries. It analyzes the implementation of the Rural
Water Supply and Sanitation Program in Tanzania. Key
mechanisms for planning and allocating resources are
analyzed at ministry, district, and village levels. Results
show that a mixture of policy incoherencies, technical
shortcomings and political influence determine that only a
small proportion of funds reaches the underserved areas.
We argue that a greater connection between the bottom-up
and top-down planning mechanisms, and a sharp increase
of downwards accountability are needed before decentral-
ized decision-making result in better resources allocation.
Meanwhile a bigger intervention from central government
is needed.Dimensionless analysis of HSDM and application to simulation of breakthrough curves of highly adsorbent porous media
http://hdl.handle.net/2117/26352
Dimensionless analysis of HSDM and application to simulation of breakthrough curves of highly adsorbent porous media
Pérez Foguet, Agustí; Casoni Rero, Eva; Huerta, Antonio
The homogeneous surface diffusion model (HSDM) is widely used for adsorption modeling of aqueous solutions. The Biot number is usually used to characterize model behavior. However, some limitations of this characterization have been reported recently, and the Stanton number has been proposed as a complement to be considered. In this work, a detailed dimensionless analysis of HSDM is presented and limit behaviors of the model are characterized, confirming but extending previous results. An accurate and efficient numerical solver is used for these purposes. The intraparticle diffusion equation is reduced to a system of two ordinary differential equations, the transport-reaction equation is discretized by using a discontinuous Galerkin method, and the overall system evolution is integrated with a time-marching scheme. This approach facilitates the simulation of HSDM with a wide range of dimensionless numbers and with a correct treatment of shocks, which appear with nonlinear adsorption isotherms and with large Biot numbers and small surface diffusivity modulus. The approach is applied to simulate the breakthrough curves of granular ferric hydroxide. Published experimental data is adequately simulated.
2015-02-16T08:50:14ZPérez Foguet, AgustíCasoni Rero, EvaHuerta, AntonioThe homogeneous surface diffusion model (HSDM) is widely used for adsorption modeling of aqueous solutions. The Biot number is usually used to characterize model behavior. However, some limitations of this characterization have been reported recently, and the Stanton number has been proposed as a complement to be considered. In this work, a detailed dimensionless analysis of HSDM is presented and limit behaviors of the model are characterized, confirming but extending previous results. An accurate and efficient numerical solver is used for these purposes. The intraparticle diffusion equation is reduced to a system of two ordinary differential equations, the transport-reaction equation is discretized by using a discontinuous Galerkin method, and the overall system evolution is integrated with a time-marching scheme. This approach facilitates the simulation of HSDM with a wide range of dimensionless numbers and with a correct treatment of shocks, which appear with nonlinear adsorption isotherms and with large Biot numbers and small surface diffusivity modulus. The approach is applied to simulate the breakthrough curves of granular ferric hydroxide. Published experimental data is adequately simulated.Adaptive finite element simulation of stack pollutant emissions over complex terrains
http://hdl.handle.net/2117/26322
Adaptive finite element simulation of stack pollutant emissions over complex terrains
Oliver Serra, Albert; Montero Garcia, Gustavo; Montenegro Armas, Rafael; Rodriguez Barrera, Eduardo; Escobar Sánchez, José M.; Pérez Foguet, Agustí
A three-dimensional finite element model for the pollutant dispersion is presented. In these environmental processes over a complex terrain, a mesh generator capable of adapting itself to the topographic characteristics is essential. The first stage of the model consists on the construction of an adaptive tetrahedral mesh of a rectangular region bounded in its lower part by the terrain and in its upper part by a horizontal plane. Once the mesh is constructed, an adaptive local refinement of tetrahedra is used in order to capture the plume rise. Wind measurements are used to compute an interpolated wind field, that is modified by using a mass-consistent model and perturbing its vertical component to introduce the plume rise effect. Then, we use an Eulerian convection–diffusion–reaction model to simulate the pollutant dispersion. In this work, the transport of pollutants is considered and dry deposition is formulated as a boundary condition. The discretization of the stack geometry allows to define the emissions as boundary conditions. The proposed model uses an adaptive finite element space discretization, a Crank-Nicolson time scheme, and a splitting operator. This approach has been applied in La Palma island. Finally, numerical results and conclusions are presented.
2015-02-12T13:18:48ZOliver Serra, AlbertMontero Garcia, GustavoMontenegro Armas, RafaelRodriguez Barrera, EduardoEscobar Sánchez, José M.Pérez Foguet, AgustíA three-dimensional finite element model for the pollutant dispersion is presented. In these environmental processes over a complex terrain, a mesh generator capable of adapting itself to the topographic characteristics is essential. The first stage of the model consists on the construction of an adaptive tetrahedral mesh of a rectangular region bounded in its lower part by the terrain and in its upper part by a horizontal plane. Once the mesh is constructed, an adaptive local refinement of tetrahedra is used in order to capture the plume rise. Wind measurements are used to compute an interpolated wind field, that is modified by using a mass-consistent model and perturbing its vertical component to introduce the plume rise effect. Then, we use an Eulerian convection–diffusion–reaction model to simulate the pollutant dispersion. In this work, the transport of pollutants is considered and dry deposition is formulated as a boundary condition. The discretization of the stack geometry allows to define the emissions as boundary conditions. The proposed model uses an adaptive finite element space discretization, a Crank-Nicolson time scheme, and a splitting operator. This approach has been applied in La Palma island. Finally, numerical results and conclusions are presented.