Articles de revista
http://hdl.handle.net/2117/516
2016-12-04T20:35:34ZGuided to leaky mode transition in uniaxial optical slab waveguides
http://hdl.handle.net/2117/97541
Guided to leaky mode transition in uniaxial optical slab waveguides
Torner Sabata, Lluís; Recolons Martos, Jaume; Pérez Torres, Juan
The guided-to-leaky hybrid mode transition in slab optical waveguides made on uniaxial crystals such as LiNbO/sub 3/, or LiTaO/sub 3/, is analyzed. Two different guided-to-leaky transitions have been identified, namely the ordinary cutoff and the extraordinary cutoff, which occur when considering negative and positive birefringent materials, respectively. Analytical but transcendental expressions have been obtained, yielding the critical optical axis orientation, relative to the waveguide axis, above which the totally guided hybrid modes become leaky. The results indicate that the value of the critical orientation strongly depends on the waveguide parameters. The possibility of tuning this critical orientation to a desired value through the waveguide parameters is discussed.
2016-11-30T15:37:45ZTorner Sabata, LluísRecolons Martos, JaumePérez Torres, JuanThe guided-to-leaky hybrid mode transition in slab optical waveguides made on uniaxial crystals such as LiNbO/sub 3/, or LiTaO/sub 3/, is analyzed. Two different guided-to-leaky transitions have been identified, namely the ordinary cutoff and the extraordinary cutoff, which occur when considering negative and positive birefringent materials, respectively. Analytical but transcendental expressions have been obtained, yielding the critical optical axis orientation, relative to the waveguide axis, above which the totally guided hybrid modes become leaky. The results indicate that the value of the critical orientation strongly depends on the waveguide parameters. The possibility of tuning this critical orientation to a desired value through the waveguide parameters is discussed.Lagrangian finite element model for the 3D simulation of glass forming processes
http://hdl.handle.net/2117/90788
Lagrangian finite element model for the 3D simulation of glass forming processes
Ryzhakov, Pavel; García Espinosa, Julio; Oñate Ibáñez de Navarra, Eugenio
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 approach, on the one hand, inherits the computational efficiency of the original fractional step approach, and on the other hand shows better mass conservation features. These features are particularly attractive taking into account the importance of the correct prediction of the glass product’s wall thickness. A smart mesh update strategy and a simple mechanical contact scheme are introduced. In order to account for temperature-dependent viscosity, the heat equation is coupled to the mechanical model. Viscosity is obtained from the temperature field via an empirical law. The model is validated and an example modeling the processes in the final blow mold of the bottle manufacturing process is proposed.
2016-10-14T13:42:47ZRyzhakov, PavelGarcía Espinosa, JulioOñate Ibáñez de Navarra, EugenioWe 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 approach, on the one hand, inherits the computational efficiency of the original fractional step approach, and on the other hand shows better mass conservation features. These features are particularly attractive taking into account the importance of the correct prediction of the glass product’s wall thickness. A smart mesh update strategy and a simple mechanical contact scheme are introduced. In order to account for temperature-dependent viscosity, the heat equation is coupled to the mechanical model. Viscosity is obtained from the temperature field via an empirical law. The model is validated and an example modeling the processes in the final blow mold of the bottle manufacturing process is proposed.A laminated structural finite element for the behavior of large non-linear reinforced concrete structures
http://hdl.handle.net/2117/89389
A laminated structural finite element for the behavior of large non-linear reinforced concrete structures
Escudero Torres, Cuauhtemoc; Oller Martínez, Sergio Horacio; Martínez García, Javier; Barbat Barbat, Horia Alejandro
In order to correctly predict the kinematics of complex structures, analysis using three-dimensional finite elements (3DFEs) seems to be the best alternative. However, simulation of large multi-layered structures with many plies can be unaffordable with 3DFEs because of the excessive computational cost, especially for non-linear materials. In addition, the discretization of very thin layers can lead to highly distorted FEs carrying numerical issues, therefore, reduced models arise as an affordable solution.
This paper describes a new finite element formulation to perform numerical simulations of laminated reinforced concrete structures. The intention of this work is that the proposed scheme can be applied in the analysis of real-life structures where a high amount of computational resources are needed to fulfill the meshing requirements, hence the resulting formulation has to be a compromise between simplicity and efficiency.
So that, the condensation of a dimension (thickness), mandatory to model three-dimensional structures with two-dimensional finite elements (2DFEs), leads to refer all layers contained within such FEs to a plane, which is typically named middle plane or geometrical plane, since its sole function is to serve as a geometrical reference. This work is based on the assumption that the geometrical plane has to be distinguished from a mechanical plane, which is where the resultant stiffness of all layers is contained. It is also assumed in this work that the mechanical plane changes its position due to non-linear response of the component materials.
2016-08-29T10:23:57ZEscudero Torres, CuauhtemocOller Martínez, Sergio HoracioMartínez García, JavierBarbat Barbat, Horia AlejandroIn order to correctly predict the kinematics of complex structures, analysis using three-dimensional finite elements (3DFEs) seems to be the best alternative. However, simulation of large multi-layered structures with many plies can be unaffordable with 3DFEs because of the excessive computational cost, especially for non-linear materials. In addition, the discretization of very thin layers can lead to highly distorted FEs carrying numerical issues, therefore, reduced models arise as an affordable solution.
This paper describes a new finite element formulation to perform numerical simulations of laminated reinforced concrete structures. The intention of this work is that the proposed scheme can be applied in the analysis of real-life structures where a high amount of computational resources are needed to fulfill the meshing requirements, hence the resulting formulation has to be a compromise between simplicity and efficiency.
So that, the condensation of a dimension (thickness), mandatory to model three-dimensional structures with two-dimensional finite elements (2DFEs), leads to refer all layers contained within such FEs to a plane, which is typically named middle plane or geometrical plane, since its sole function is to serve as a geometrical reference. This work is based on the assumption that the geometrical plane has to be distinguished from a mechanical plane, which is where the resultant stiffness of all layers is contained. It is also assumed in this work that the mechanical plane changes its position due to non-linear response of the component materials.Impact of logistics and shipping in the sustainable development of societies
http://hdl.handle.net/2117/86595
Impact of logistics and shipping in the sustainable development of societies
Martínez Marín, Jesús Ezequiel
Definitely, although not very obvious, shipping affects the daily lives of the majority of the
world population. The socio-economic implications of logistics undoubtedly affect the social
development of cities. With the implementation of sustainability in the supply chain, and not
only think of a commercial profit but in an overall benefit in mind the impact it is having on the
ecosystem. Solutions, research and discussion topics to open an academic contribution is
interesting, that would open up discussions.
2016-05-04T15:24:37ZMartínez Marín, Jesús EzequielDefinitely, although not very obvious, shipping affects the daily lives of the majority of the
world population. The socio-economic implications of logistics undoubtedly affect the social
development of cities. With the implementation of sustainability in the supply chain, and not
only think of a commercial profit but in an overall benefit in mind the impact it is having on the
ecosystem. Solutions, research and discussion topics to open an academic contribution is
interesting, that would open up discussions.Validation on large scale tests of a new hardening–softening law for the Barcelona plastic damage model
http://hdl.handle.net/2117/86285
Validation on large scale tests of a new hardening–softening law for the Barcelona plastic damage model
Barbu, Lucia Gratiela; Martínez García, Javier; Oller Martínez, Sergio Horacio; Barbat Barbat, Horia Alejandro
2016-04-27T16:27:14ZBarbu, Lucia GratielaMartínez García, JavierOller Martínez, Sergio HoracioBarbat Barbat, Horia AlejandroAn efficient multi-scale method for non-linear analysis of composite structures
http://hdl.handle.net/2117/85989
An efficient multi-scale method for non-linear analysis of composite structures
Otero Gruer, Fermín Enrique; Martínez García, Javier; Oller Martínez, Sergio Horacio; Salomon Rotlisbeger, Ramon Omar
The use of multi-scale procedures is encouraged by the continuous increase of computational capacity, but it is still a challenge performing a non-linear analysis of real composite structures without the aid of large computers. This work proposes a strategy to conduct non-linear multi-scale analysis in an efficient way. The proposed method considers that in a large structure, in general, material non-linear processes only take place in a localized region (or in a reduced number of finite elements, if a FE method is used). The strategy determines the elements that require a non-linear analysis defining of a non-linear activation function that accounts for the failure of the most critical point in the microstructure. The procedure conserves the dissipated energy through the scales, being mesh independent as the mesh objectivity concept is extended to the microstructure. The validity of the strategy proposed is proved with the analysis of academic examples showing not only the mesh independency but also the reduction of computational cost. Finally, an industrial composite component is solved using a standard computer, showing that the proposed strategy is capable of reducing the computational cost from 32 days and 14 hours (required by a classical multi-scale method) to less than 12 hours.
2016-04-20T13:54:56ZOtero Gruer, Fermín EnriqueMartínez García, JavierOller Martínez, Sergio HoracioSalomon Rotlisbeger, Ramon OmarThe use of multi-scale procedures is encouraged by the continuous increase of computational capacity, but it is still a challenge performing a non-linear analysis of real composite structures without the aid of large computers. This work proposes a strategy to conduct non-linear multi-scale analysis in an efficient way. The proposed method considers that in a large structure, in general, material non-linear processes only take place in a localized region (or in a reduced number of finite elements, if a FE method is used). The strategy determines the elements that require a non-linear analysis defining of a non-linear activation function that accounts for the failure of the most critical point in the microstructure. The procedure conserves the dissipated energy through the scales, being mesh independent as the mesh objectivity concept is extended to the microstructure. The validity of the strategy proposed is proved with the analysis of academic examples showing not only the mesh independency but also the reduction of computational cost. Finally, an industrial composite component is solved using a standard computer, showing that the proposed strategy is capable of reducing the computational cost from 32 days and 14 hours (required by a classical multi-scale method) to less than 12 hours.A FEM fluid-structure interaction algorithm for analysis of the seal dynamics of a Surface-Effect Ship
http://hdl.handle.net/2117/84942
A FEM fluid-structure interaction algorithm for analysis of the seal dynamics of a Surface-Effect Ship
García Espinosa, Julio; Capua, Daniel di; Serván Camas, Borja; Ubach Fuentes, Pere-Andreu; Oñate Ibáñez de Navarra, Eugenio
This paper shows the recent work of the authors in the development of a time-domain FEM model for evaluation of the seal dynamics of a surface effect ship. The fluid solver developed for this purpose, uses a potential flow approach along with a streamline integration of the free surface. The paper focuses on the free surface-structure algorithm that has been developed to allow the simulation of the complex and highly dynamic behaviour of the seals in the interface between the air cushion, and the water.; The developed fluid-structure interaction solver is based, on one side, on an implicit iteration algorithm, communicating pressure forces and displacements of the seals at memory level and, on the other side, on an innovative wetting and drying scheme able to predict the water action on the seals. The stability of the iterative scheme is improved by means of relaxation, and the convergence is accelerated using Aitken's method.; Several validations against experimental results have been carried out to demonstrate the developed algorithm. (C) 2015 Elsevier B.V. All rights reserved.
2016-03-31T11:20:03ZGarcía Espinosa, JulioCapua, Daniel diServán Camas, BorjaUbach Fuentes, Pere-AndreuOñate Ibáñez de Navarra, EugenioThis paper shows the recent work of the authors in the development of a time-domain FEM model for evaluation of the seal dynamics of a surface effect ship. The fluid solver developed for this purpose, uses a potential flow approach along with a streamline integration of the free surface. The paper focuses on the free surface-structure algorithm that has been developed to allow the simulation of the complex and highly dynamic behaviour of the seals in the interface between the air cushion, and the water.; The developed fluid-structure interaction solver is based, on one side, on an implicit iteration algorithm, communicating pressure forces and displacements of the seals at memory level and, on the other side, on an innovative wetting and drying scheme able to predict the water action on the seals. The stability of the iterative scheme is improved by means of relaxation, and the convergence is accelerated using Aitken's method.; Several validations against experimental results have been carried out to demonstrate the developed algorithm. (C) 2015 Elsevier B.V. All rights reserved.Development of a decision support system for optimization of the performance of sailing yachts
http://hdl.handle.net/2117/84909
Development of a decision support system for optimization of the performance of sailing yachts
García Espinosa, Julio; Ortigosa Barragán, Inma; Fernandez, A
In this paper, the conception and design of a new monitoring system for a racing yachts rig is presented. The sensors developed are able to process the measured strain data, by applying artificial neural networks (ANN) algorithms, and then evaluate the load acting on an element and identify the direction of the action of that force. This way, it is possible to identify the actual operating conditions of the yacht rig. The required data for ANN training is generated from the results obtained from different finite element method (FEM) computational models of the device. Furthermore, during the design phase of the system, different experimental campaigns were carried out. The experimental tests were designed to serve as proof of concept, as well as to validate the different procedures used in the system development and application.; The developed monitoring system is wireless, low-intrusive and easily adaptable to any yacht configuration. This work also presents the integration of the monitoring system into a coupled fluid-structure computation model for the sails and rig of a boat. The resulting system is an efficient tool for evaluating performance and decision support in the adjustment of a sailboat rig. (C) 2014 CIMNE (Universitat Politecnica de Catalunya). Published by Elsevier Espana, S.L.U. All rights reserved.
2016-03-30T16:45:12ZGarcía Espinosa, JulioOrtigosa Barragán, InmaFernandez, AIn this paper, the conception and design of a new monitoring system for a racing yachts rig is presented. The sensors developed are able to process the measured strain data, by applying artificial neural networks (ANN) algorithms, and then evaluate the load acting on an element and identify the direction of the action of that force. This way, it is possible to identify the actual operating conditions of the yacht rig. The required data for ANN training is generated from the results obtained from different finite element method (FEM) computational models of the device. Furthermore, during the design phase of the system, different experimental campaigns were carried out. The experimental tests were designed to serve as proof of concept, as well as to validate the different procedures used in the system development and application.; The developed monitoring system is wireless, low-intrusive and easily adaptable to any yacht configuration. This work also presents the integration of the monitoring system into a coupled fluid-structure computation model for the sails and rig of a boat. The resulting system is an efficient tool for evaluating performance and decision support in the adjustment of a sailboat rig. (C) 2014 CIMNE (Universitat Politecnica de Catalunya). Published by Elsevier Espana, S.L.U. All rights reserved.Improving the efficiency of a high speed catamaran through the replacement of the propulsion system
http://hdl.handle.net/2117/84853
Improving the efficiency of a high speed catamaran through the replacement of the propulsion system
Melo Rodríguez, Germán de; Echevarrieta Sazatornil, Ignacio; Marí Serra, Juan
The high speed vessels are primarily designed for short distances services as public transport of passengers and vehicles. The range of high speed, according to the Code of high-speed vessels begins at 20 knots, which depends on the cruise speed you desire for your vessel; you will have to use the most appropriate type of propellant. In general, in the past 20 years, they have been building high-speed vessels with speeds above 33 knots, which meant installing water jet propellants coupled to powerful engines and therefore of high consumption of fuel, increasing operating costs and causing increased air pollution. Although the prices of fuel have been reduced to half, due to the sharp fall in oil prices, the consumption of fuel and the air pollution remains high at these speeds and powers used, in addition to that the reduction of the time spent on each trip is not excessive, mainly in short routes that are less than an hour . This article is about adapting a ship of high-speed service, with a maximum speed in tests of 34 knots and to reduce its operating costs (fuel, maintenance, etc.) and make it economically viable; before the transformation, this vessel was operating with a service speed of 22 knots, and with a consumption per mile of 135 litters of MGO. The transformation process has consisted by: – Replacement of the two original water jet with four shaft lines with fix pitch propeller. – Replacement of the two original main engines (2 x 6500 kW = 13000 kW) by four engines (4 x 1380kW = 5.520 kW). – Changing the underwater hull shape to fit the new propellers and maximize its efficiency. – Relocation of auxiliary engines, to achieve the most efficient trim. – Installation of two lateral propellers to improve maneuverability and shorten the total time of journey. After the reform and the return to service of the vessel with a service speed of over 22 knots, it has been verified that the consumption per mile is of 45 litters MGO, representing a reduction of 65% of consumption and even more reduction of emissions as the new engines comply with the latest regulations.
2016-03-30T10:32:04ZMelo Rodríguez, Germán deEchevarrieta Sazatornil, IgnacioMarí Serra, JuanThe high speed vessels are primarily designed for short distances services as public transport of passengers and vehicles. The range of high speed, according to the Code of high-speed vessels begins at 20 knots, which depends on the cruise speed you desire for your vessel; you will have to use the most appropriate type of propellant. In general, in the past 20 years, they have been building high-speed vessels with speeds above 33 knots, which meant installing water jet propellants coupled to powerful engines and therefore of high consumption of fuel, increasing operating costs and causing increased air pollution. Although the prices of fuel have been reduced to half, due to the sharp fall in oil prices, the consumption of fuel and the air pollution remains high at these speeds and powers used, in addition to that the reduction of the time spent on each trip is not excessive, mainly in short routes that are less than an hour . This article is about adapting a ship of high-speed service, with a maximum speed in tests of 34 knots and to reduce its operating costs (fuel, maintenance, etc.) and make it economically viable; before the transformation, this vessel was operating with a service speed of 22 knots, and with a consumption per mile of 135 litters of MGO. The transformation process has consisted by: – Replacement of the two original water jet with four shaft lines with fix pitch propeller. – Replacement of the two original main engines (2 x 6500 kW = 13000 kW) by four engines (4 x 1380kW = 5.520 kW). – Changing the underwater hull shape to fit the new propellers and maximize its efficiency. – Relocation of auxiliary engines, to achieve the most efficient trim. – Installation of two lateral propellers to improve maneuverability and shorten the total time of journey. After the reform and the return to service of the vessel with a service speed of over 22 knots, it has been verified that the consumption per mile is of 45 litters MGO, representing a reduction of 65% of consumption and even more reduction of emissions as the new engines comply with the latest regulations.Analysis and measurement of NOx emissions in port auxiliary vessels
http://hdl.handle.net/2117/84850
Analysis and measurement of NOx emissions in port auxiliary vessels
Melo Rodríguez, Germán de; Murcia Gonzalez, Juan Carlos
This paper is made NOx pollution emitted by port auxiliary vessels, specifically by harbour tugs, due to its unique operating characteristics of operation, require a large propulsion power changes discontinuously, also possess some peculiar technical characteristics, large tonnage and high propulsive power, that differentiate them from other auxiliary vessels of the port. Taking into account all the above features, there are no studies of the NOx emission engines caused by different working regimes of power because engine manufacturers have not measured these emissions across the range of operating power, but usually we only report the pollution produced by its engines to a maximum continuous power.
2016-03-30T10:20:03ZMelo Rodríguez, Germán deMurcia Gonzalez, Juan CarlosThis paper is made NOx pollution emitted by port auxiliary vessels, specifically by harbour tugs, due to its unique operating characteristics of operation, require a large propulsion power changes discontinuously, also possess some peculiar technical characteristics, large tonnage and high propulsive power, that differentiate them from other auxiliary vessels of the port. Taking into account all the above features, there are no studies of the NOx emission engines caused by different working regimes of power because engine manufacturers have not measured these emissions across the range of operating power, but usually we only report the pollution produced by its engines to a maximum continuous power.