The CIAO Multi-Dialect Compiler and System: An Experimentation Workbench for Future (C)LP Systems

CIAO is an advanced programming environment supporting Logic and Constraint programming. It offers a simple concurrent kernel on top of which declarative and non-declarative extensions are added via librarles. Librarles are available for supporting the ISOProlog standard, several constraint domains, functional and higher order programming, concurrent and distributed programming, internet programming, and others. The source language allows declaring properties of predicates via assertions, including types and modes. Such properties are checked at compile-time or at run-time. The compiler and system architecture are designed to natively support modular global analysis, with the two objectives of proving properties in assertions and performing program optimizations, including transparently exploiting parallelism in programs. The purpose of this paper is to report on recent progress made in the context of the CIAO system, with special emphasis on the capabilities of the compiler, the techniques used for supporting such capabilities, and the results in the ��reas of program analysis and transformation already obtained with the system.

The CIAO multi-dialect compiler and system: An experimentation workbench for future (C)LP systems

Abstract is not available.

Numerical and Experimental Studies of Sail Aerodynamics

The purpose of this investigation was the determination of the aerodynamic performance of sails and gain knowledge of the phenomena involved in order to improve the aerody��namic characteristics. In this research, the airflow around different sails in four scenarios was studied. The method to analyze these scenarios was the combination of numerical simulations and experimental tests by taking advantage of the best of each tool. Two different Com��putational Fluid Dynamic codes were utilized: the ANSYS-CFX and the CD-Adapco���s STAR-CCM+. The experimental tests were conducted in the Atmospheric Boundary Layer Wind Tunnel at the Universidad de Granada (Spain), the Twisted Flow Wind Tunnel at the University of Auckland (New Zealand) and the A9 Wind Tunnel at the Universidad Polit��ecnica de Madrid (Spain). Through this research, it was found the three-dimensional effect of the mast on the aerodynamic performance of an IMS Class boat. The pressure distribution on a Transpac 52 Class mainsail was also determined. Moreover, the aerodynamic perfor��mance of the 43ft and 60ft Dhow Classes was obtained. Finally, a feasibility study was conducted to use a structural wing in combination with conventional propulsions systems. The main conclusion was that this research clarified gaps on the knowledge of the aerodynamic performance of sails. Moreover, since commercial codes were not specifically designed to study sails, a procedure was developed. On the other hand, innovative experimental techniques were used and applied to model-scale sails. The achievements of this thesis are promising and some of the results are already in use by the industry on a daily basis. El prop��sito de este estudio era determinar el comportamiento aerodin��mico de unas velas y mejorar el conocimiento de los fen��menos que suceden para optimizar las caracter��sticas aerodin��micas de dichas velas. En esta investigaci��n se estudi�� el flujo de aire alrededor de diferentes velas en cuatro escenarios. El m��todo para analizar estos escenarios fue la combinaci��n de simulaciones num��ricas y ensayos experimentales mediante el aprovechamiento de las ventajas de cada herramienta. Se utilizaron dos c��digos de din��mica de fluidos computacional: el ANSYS-CFX y el STAR-CCM+ de la empresa CD-Adapco. Los ensayos experimentales se desarrollaron en el t��nel de viento de capa l��mite de la Universidad de Granada (Espa��a), el t��nel de viento de la Universidad de Auckland (Nueva Zelanda) y en el t��nel A9 de la Universidad Polit��cnica de Madrid (Espa��a). Mediante esta investigaci��n, se determin�� el efecto tridimensional del m��stil en un velero de la clase IMS. Tambi��n se describi�� la distribuci��n de presiones sobre una mayor de un Transpac 52. Adem��s, se obtuvo el comportamiento aerodin��mico de las clases 43ft y 60ft de los veleros Dhows. Finalmente, se llev�� a cabo un estudio de viabilidad de la utilizaci��n de un ala estructural en combinaci��n con sistemas de propulsi��n convencionales. La conclusi��n principal de esta investigaci��n fue la capacidad de explicar ciertas lagunas en el conocimiento del comportamiento aerodin��mico de las velas en diferentes escenarios. Adem��s, dado que los c��digos comerciales no est��n espec��ficamente dise��ados para el estudio de velas, se desarroll�� un procedimiento a tal efecto. Por otro lado, se han utilizado innovadoras t��cnicas experimentales y se han aplicado a modelos de velas a escala. Los logros de esta investigaci��n son prometedores y algunos de los resultados obtenidos ya est��n siendo utilizados por la industria en su d��a a d��a.

Provisos for classic linear oscillator design methods. New linear oscillator design based on the NDF/RRT

In this paper, the classic oscillator design methods are reviewed, and their strengths and weaknesses are shown. Provisos for avoiding the misuse of classic methods are also proposed. If the required provisos are satisfied, the solutions provided by the classic methods (oscillator start-up linear approximation) will be correct. The provisos verification needs to use the NDF (Network Determinant Function). The use of the NDF or the most suitable RRT (Return Relation Transponse), which is directly related to the NDF, as a tool to analyze oscillators leads to a new oscillator design method. The RRT is the "true" loop-gain of oscillators. The use of the new method is demonstrated with examples. Finally, a comparison of NDF/RRT results with the HB (Harmonic Balance) simulation and practical implementation measurements prove the universal use of the new methods.

Comments and remarks over classic linear loop-gain method for oscillator design and analysis. New proposed method based on NDF/RRT

Abstract. This paper describes a new and original method for designing oscillators based on the Normalized Determinant Function (NDF) and Return Relations (RRT)- Firstly, a review of the loop-gain method will be performed. The loop-gain method pros, cons and some examples for exploring wrong solutions provided by this method will be shown. This method produces in some cases wrong solutions because some necessary conditions have not been fulfilled. The required necessary conditions to assure a right solution will be described. The necessity of using the NDF or the Transpose Return Relations (RRT), which are related with the True Loop-Gain, to test the additional conditions will be demonstrated. To conclude this paper, the steps for oscillator design and analysis, using the proposed NDF/RRj method, will be presented. The loop-gain wrong solutions will be compared with the NDF/RRj and the accuracy of this method to estimate the oscillation frequency and QL will be demonstrated. Some additional examples of plane reference oscillators (Z/Y/T), will be added and they will be analyzed with the new NDF/RRj proposed method, even these oscillators cannot be analyzed using the classic loop gain method.

The dicode workbench: A flexible framework for the integration of information and web services

Aiming to address requirements concerning integration of services in the context of ?big data?, this paper presents an innovative approach that (i) ensures a flexible, adaptable and scalable information and computation infrastructure, and (ii) exploits the competences of stakeholders and information workers to meaningfully confront information management issues such as information characterization, classification and interpretation, thus incorporating the underlying collective intelligence. Our approach pays much attention to the issues of usability and ease-of-use, not requiring any particular programming expertise from the end users. We report on a series of technical issues concerning the desired flexibility of the proposed integration framework and we provide related recommendations to developers of such solutions. Evaluation results are also discussed.

Computational Methods for Identification of Vibrating Structures

System identification deals with the problem of building mathematical models of dynamical systems based on observed data from the system" [1]. In the context of civil engineering, the system refers to a large scale structure such as a building, bridge, or an offshore structure, and identification mostly involves the determination of modal parameters (the natural frequencies, damping ratios, and mode shapes). This paper presents some modal identification results obtained using a state-of-the-art time domain system identification method (data-driven stochastic subspace algorithms [2]) applied to the output-only data measured in a steel arch bridge. First, a three dimensional finite element model was developed for the numerical analysis of the structure using ANSYS. Modal analysis was carried out and modal parameters were extracted in the frequency range of interest, 0-10 Hz. The results obtained from the finite element modal analysis were used to determine the location of the sensors. After that, ambient vibration tests were conducted during April 23-24, 2009. The response of the structure was measured using eight accelerometers. Two stations of three sensors were formed (triaxial stations). These sensors were held stationary for reference during the test. The two remaining sensors were placed at the different measurement points along the bridge deck, in which only vertical and transversal measurements were conducted (biaxial stations). Point estimate and interval estimate have been carried out in the state space model using these ambient vibration measurements. In the case of parametric models (like state space), the dynamic behaviour of a system is described using mathematical models. Then, mathematical relationships can be established between modal parameters and estimated point parameters (thus, it is common to use experimental modal analysis as a synonym for system identification). Stable modal parameters are found using a stabilization diagram. Furthermore, this paper proposes a method for assessing the precision of estimates of the parameters of state-space models (confidence interval). This approach employs the nonparametric bootstrap procedure [3] and is applied to subspace parameter estimation algorithm. Using bootstrap results, a plot similar to a stabilization diagram is developed. These graphics differentiate system modes from spurious noise modes for a given order system. Additionally, using the modal assurance criterion, the experimental modes obtained have been compared with those evaluated from a finite element analysis. A quite good agreement between numerical and experimental results is observed.

Pulsatile flow in coronary bifurcations for different stenting techniques

The objective of this work is to analyze the local hem odynamic changes caused in a coronary bifurcation by three different stenting techniques: simple stenting of the main vessel, simple stenting of the main vessel with kissing balloon in the side branch and culotte. To carry out this study an idealized geometry of a coronary bifurcation is used, and two bifurcation angles, 45�� and 90��, are chosen as representative of the wide variety of re al configurations. In order to quantify the influence of the stenting technique on the local blood flow, both numeri- cal simulations and experimental measurements are performed. First, steady simulations are carried out with the commercial code ANSYS-Fluent, and then, experimental measurements with PIV (Particle Image Velocimetry) obtained in the laboratory are used to validate the numerical simulation. The steady computational simulations show a good overall agreement with the experimental data. Second, pulsatile flow is considered to take into account the tran- sient effects. The time averaged wall shear stress, scillatory shear index and pressure drop obtained numerically are used to compare the behavior of the stenting techniques.

Unidad did��ctica sobre el uso del programa Virtual.Lab para simulaciones ac��sticas. Parte I

El presente Proyecto de Fin de Carrera supone el prop��sito conjunto de los alumnos ��lvaro Morillas y Fernando S��ez, y del profesor Vladimir Ulin, de desarrollar una unidad did��ctica sobre el programa de simulaci��n para ingenier��a Virtual.Lab. La versi��n sobre la que se ha trabajado para realizar este texto es la 11, publicada en agosto de 2012. Virtual.Lab, del fabricante belga LMS International, es una plataforma software de ingenier��a asistida por ordenador, que agrupa en una misma aplicaci��n varias herramientas complementarias en el dise��o de un producto, desde su definici��n geom��trica a los an��lisis de durabilidad, ruido u optimizaci��n. No obstante, de entre todas las posibles simulaciones que nos permite el programa, en este proyecto s��lo se tratan las que est��n relacionadas con la ac��stica. Cabe resaltar que gran parte de los conceptos manejados en Virtual.Lab son compatibles con el programa CATIA V5, ya que ambos programas vienen instalados y funcionan conjuntamente. Por eso, el lector de este proyecto podr�� transportar sus conocimientos al que es uno de los programas est��ndar en las industrias aeron��utica, naval y automovil��stica, entre otras. Antes de este proyecto, otros alumnos de la escuela tambi��n realizaron proyectos de fin de carrera en el campo de la simulaci��n computarizada en ac��stica. Una caracter��stica com��n a estos trabajos es que era necesario hacer uso de distintos programas para cada una de las etapas de simulaci��n (como por ejemplo, ANSYS para el modelado y estudio de la vibraci��n y SYSNOISE para las simulaciones ac��sticas, adem��s de otros programas auxiliares para las traducciones de formato). Con Virtual.Lab desaparece esta necesidad y el tiempo empleado se reduce. Debido a que las soluciones por ordenador est��n ganando cada vez m��s importancia en la industria actual, los responsables de este proyecto consideran la necesidad de formaci��n de profesionales en esta rama. Para responder a la demanda empresarial de trabajadores cualificados, se espera que en los pr��ximos a��os los planes de estudio contengan m��s cursos en esta materia. Por tanto la intenci��n de los autores es que este material sea de utilidad para el aprendizaje y docencia de estas asignaturas en cursos sucesivos. Por todo esto, se justifica la relevancia de este PFC como manual para introducir a los alumnos interesados en iniciarse en un sistema actual, de uso extendido en otras universidades tecnol��gicas europeas, y con buenas perspectivas de futuro. En este proyecto se incluyen varios ejemplos ejecutables desde el programa, as�� como v��deos explicativos que ayudan a mostrar gr��ficamente los procesos de simulaci��n. Estos archivos se pueden encontrar en el CD adjunto. Abstract This final thesis is a joint project made by the students ��lvaro Morillas and Fernando S��ez, and the professor Vladimir Ulin. The nature of the joint regards the writing of a didactic unit on Virtual.Lab, the simulation software. The software version used in this text is the number 11, released in August 2012. Virtual.Lab, from the Belgian developer LMS International, is a computer-aided engineering software which is used for several related tasks in this field: product design, durability simulation, optimization, etc. However, this project is focused on the acoustical capabilities. It is worthy to highlight that most procedures explained in this text can be used in the software CATIA V5 as well. Both tools come installed together and may be used at the same time. Therefore, the reader of this project will be able to use the acquired knowledge in one of the most relevant softwares for the aerospace, marine and automotive engineering. Previously to the development of this project, this School has conducted projects on this field. These projects regarded the use of ANSYS for modeling and meshing stages as well as the use of SYSNOISE for the final acoustic analysis. Since both systems use different file formats, a third-party translation software was required. This thesis fulfill this pending necessity with Virtual.Lab; the translation software procedure is not necessary anymore and simulations can be done in a more flexible, fast way. Since companies have an increasing usage of numerical methods in the development of their products and services, the authors think that it is important to develop the appropriate method to instruct new professionals in the field. Thus, the aim of this project is to help teachers and students in their process of learning the use of this leading software in acoustical simulations. For all the reasons mentioned above, we consider that this project is relevant for the School and the educational community. Aiming to achieve this objective the author offers example files and video demonstrations with guidance in the CD that accompanies this material. This facilitates the comprehension of the practical tasks and guides the prospect users of the software.

An��lisis del acoplamiento vibro-ac��stico en resonadores de membrana

El presente Trabajo Fin de M��ster pretende llevar a cabo el an��lisis del comportamiento vibratorio de resonadores de membrana, consistentes en un panel delgado y ligero montado a cierta distancia de un elemento constructivo r��gido y pesado. Este tipo de sistemas resonantes son empleados habitualmente como absorbentes de media-baja frecuencia en aplicaciones de acondicionamiento ac��stico de salas. El an��lisis har�� especial hincapi�� en la influencia del acoplamiento mec��nico-ac��stico entre la placa vibrante (estructura) y el colch��n de aire (fluido) encerrado entre la misma y la pared r��gida. En primer lugar, realizaremos el an��lisis modal experimental del resonador objeto de ensayo a partir de las mediciones de su respuesta vibratoria, con el fin de caracterizar su comportamiento en base a sus primeros modos propios acoplados de flexi��n. El an��lisis de las se��ales vibratorias en el dominio de la frecuencia para la identificaci��n de dicho modos se realizar�� en el entorno de programaci��n MATLAB, haciendo uso de una herramienta propia que implementa los m��todos de c��lculo y los algoritmos necesarios para tal fin. Asimismo, simularemos el comportamiento del resonador mediante el m��todo de elementos finitos (FEM), utilizando las aplicaciones ANSYS y SYSNOISE, considerando diferentes condiciones frontera en el modelo generado. Los resultados aqu�� obtenidos ser��n de utilidad para complementar aquellos obtenidos de forma experimental a la hora de extraer conclusiones pr��cticas del an��lisis realizado. SUMMARY. This Master's Thesis intends to carry out the analysis of the vibratory behaviour of resonance absorbers, consisting of a thin and lightweight panel mounted at a distance from a rigid wall. Such systems are commonly used as sound absorption systems for mid-low frequency in room acoustics applications. The analysis will emphasize the influence of mechanical-acoustic coupling between the vibrating plate (structure) and the air cushion (acoustic element) enclosed behind it. First of all, we are performing the experimental modal analysis of the resonance absorber under test from the vibrational response measurements, in order to characterize its behaviour based on its first bending coupled-modes. The analysis of vibration signals in the frequency domain for the identification of such modes will be made in MATLAB programming environment, using a proprietary tool that implements the calculation methods and algorithms needed for this purpose. Furthermore, we are simulating the behaviour of the resonance absorber applying the Finite Element Method (FEM) ��� using ANSYS and SYSNOISE applications - considering different boundary conditions in the model created. The results from the simulation will be useful to complement those obtained experimentally when drawing practical conclusions from this analysis.

High power beam dump project for the accelerator prototype LIPAc: Cooling design and analysis

En el campo de la fusi��n nuclear y desarroll��ndose en paralelo a ITER (International Thermonuclear Experimental Reactor), el proyecto IFMIF (International Fusion Material Irradiation Facility) se enmarca dentro de las actividades complementarias encaminadas a solucionar las barreras tecnol��gicas que a��n plantea la fusi��n. En concreto IFMIF es una instalaci��n de irradiaci��n cuya misi��n es caracterizar materiales resistentes a condiciones extremas como las esperadas en los futuros reactores de fusi��n como DEMO (DEMOnstration power plant). Consiste de dos aceleradores de deuterones que proporcionan un haz de 125 mA y 40 MeV cada uno, que al colisionar con un blanco de litio producen un flujo neutr��nico intenso (1017 neutrones/s) con un espectro similar al de los neutrones de fusi��n [1], [2]. Dicho flujo neutr��nico es empleado para irradiar los diferentes materiales candidatos a ser empleados en reactores de fusi��n, y las muestras son posteriormente examinadas en la llamada instalaci��n de post-irradiaci��n. Como primer paso en tan ambicioso proyecto, una fase de validaci��n y dise��o llamada IFMIFEVEDA (Engineering Validation and Engineering Design Activities) se encuentra actualmente en desarrollo. Una de las actividades contempladas en esta fase es la construcci��n y operaci��n de una acelarador prototipo llamado LIPAc (Linear IFMIF Prototype Accelerator). Se trata de un acelerador de deuterones de alta intensidad id��ntico a la parte de baja energ��a de los aceleradores de IFMIF. Los componentes del LIPAc, que ser�� instalado en Jap��n, son suministrados por diferentes pa��ses europeos. El acelerador proporcionar�� un haz continuo de deuterones de 9 MeV con una potencia de 1.125 MW que tras ser caracterizado con diversos instrumentos deber�� pararse de forma segura. Para ello se requiere un sistema denominado bloque de parada (Beam Dump en ingl��s) que absorba la energ��a del haz y la transfiera a un sumidero de calor. Espa��a tiene el compromiso de suministrar este componente y CIEMAT (Centro de Investigaciones Energ��ticas Medioambientales y Tecnol��gicas) es responsable de dicha tarea. La pieza central del bloque de parada, donde se para el haz de iones, es un cono de cobre con un ��ngulo de 3.5o, 2.5 m de longitud y 5 mm de espesor. Dicha pieza est�� refrigerada por agua que fluye en su superficie externa por el canal que se forma entre el cono de cobre y otra pieza conc��ntrica con ��ste. Este es el marco en que se desarrolla la presente tesis, cuyo objeto es el dise��o del sistema de refrigeraci��n del bloque de parada del LIPAc. El dise��o se ha realizado utilizando un modelo simplificado unidimensional. Se han obtenido los par��metros del agua (presi��n, caudal, p��rdida de carga) y la geometr��a requerida en el canal de refrigeraci��n (anchura, rugosidad) para garantizar la correcta refrigeraci��n del bloque de parada. Se ha comprobado que el dise��o permite variaciones del haz respecto a la situaci��n nominal siendo el flujo cr��tico calor��fico al menos 2 veces superior al nominal. Se han realizado asimismo simulaciones fluidodin��micas 3D con ANSYS-CFX en aquellas zonas del canal de refrigeraci��n que lo requieren. El bloque de parada se activar�� como consecuencia de la interacci��n del haz de part��culas lo que impide cualquier cambio o reparaci��n una vez comenzada la operaci��n del acelerador. Por ello el dise��o ha de ser muy robusto y todas las hip��tesis utilizadas en la realizaci��n de ��ste deben ser cuidadosamente comprobadas. Gran parte del esfuerzo de la tesis se centra en la estimaci��n del coeficiente de transferencia de calor que es determinante en los resultados obtenidos, y que se emplea adem��s como condici��n de contorno en los c��lculos mec��nicos. Para ello por un lado se han buscado correlaciones cuyo rango de aplicabilidad sea adecuado para las condiciones del bloque de parada (canal anular, diferencias de temperatura agua-pared de decenas de grados). En un segundo paso se han comparado los coeficientes de pel��cula obtenidos a partir de la correlaci��n seleccionada (Petukhov-Gnielinski) con los que se deducen de simulaciones fluidodin��micas, obteniendo resultados satisfactorios. Por ��ltimo se ha realizado una validaci��n experimental utilizando un prototipo y un circuito hidr��ulico que proporciona un flujo de agua con los par��metros requeridos en el bloque de parada. Tras varios intentos y mejoras en el experimento se han obtenido los coeficientes de pel��cula para distintos caudales y potencias de calentamiento. Teniendo en cuenta la incertidumbre de las medidas, los valores experimentales concuerdan razonablemente bien (en el rango de 15%) con los deducidos de las correlaciones. Por motivos radiol��gicos es necesario controlar la calidad del agua de refrigeraci��n y minimizar la corrosi��n del cobre. Tras un estudio bibliogr��fico se identificaron los par��metros del agua m��s adecuados (conductividad, pH y concentraci��n de ox��geno disuelto). Como parte de la tesis se ha realizado asimismo un estudio de la corrosi��n del circuito de refrigeraci��n del bloque de parada con el doble fin de determinar si puede poner en riesgo la integridad del componente, y de obtener una estimaci��n de la velocidad de corrosi��n para dimensionar el sistema de purificaci��n del agua. Se ha utilizado el c��digo TRACT (TRansport and ACTivation code) adapt��ndalo al caso del bloque de parada, para lo cual se trabaj�� con el responsable (Panos Karditsas) del c��digo en Culham (UKAEA). Los resultados confirman que la corrosi��n del cobre en las condiciones seleccionadas no supone un problema. La Tesis se encuentra estructurada de la siguiente manera: En el primer cap��tulo se realiza una introducci��n de los proyectos IFMIF y LIPAc dentro de los cuales se enmarca esta Tesis. Adem��s se describe el bloque de parada, siendo el dise��o del sistema de rerigeraci��n de ��ste el principal objetivo de la Tesis. En el segundo y tercer cap��tulo se realiza un resumen de la base te��rica as�� como de las diferentes herramientas empleadas en el dise��o del sistema de refrigeraci��n. El cap��tulo cuarto presenta los resultados del relativos al sistema de refrigeraci��n. Tanto los obtenidos del estudio unidimensional, como los obtenidos de las simulaciones fluidodin��micas 3D mediante el empleo del c��digo ANSYS-CFX. En el quinto cap��tulo se presentan los resultados referentes al an��lisis de corrosi��n del circuito de refrigeraci��n del bloque de parada. El cap��tulo seis se centra en la descripci��n del montaje experimental para la obtenci��n de los valores de p��rdida de carga y coeficiente de transferencia del calor. Asimismo se presentan los resultados obtenidos en dichos experimentos. Finalmente encontramos un cap��tulo de ap��ndices en el que se describen una serie de experimentos llevados a cabo como pasos intermedios en la obtenci��n del resultado experimental del coeficiente de pel��cula. Tambi��n se presenta el c��digo inform��tico empleado para el an��lisis unidimensional del sistema de refrigeraci��n del bloque de parada llamado CHICA (Cooling and Heating Interaction and Corrosion Analysis). ABSTRACT In the nuclear fusion field running in parallel to ITER (International Thermonuclear Experimental Reactor) as one of the complementary activities headed towards solving the technological barriers, IFMIF (International Fusion Material Irradiation Facility) project aims to provide an irradiation facility to qualify advanced materials resistant to extreme conditions like the ones expected in future fusion reactors like DEMO (DEMOnstration Power Plant). IFMIF consists of two constant wave deuteron accelerators delivering a 125 mA and 40 MeV beam each that will collide on a lithium target producing an intense neutron fluence (1017 neutrons/s) with a similar spectra to that of fusion neutrons [1], [2]. This neutron flux is employed to irradiate the different material candidates to be employed in the future fusion reactors, and the samples examined after irradiation at the so called post-irradiative facilities. As a first step in such an ambitious project, an engineering validation and engineering design activity phase called IFMIF-EVEDA (Engineering Validation and Engineering Design Activities) is presently going on. One of the activities consists on the construction and operation of an accelerator prototype named LIPAc (Linear IFMIF Prototype Accelerator). It is a high intensity deuteron accelerator identical to the low energy part of the IFMIF accelerators. The LIPAc components, which will be installed in Japan, are delivered by different european countries. The accelerator supplies a 9 MeV constant wave beam of deuterons with a power of 1.125 MW, which after being characterized by different instruments has to be stopped safely. For such task a beam dump to absorb the beam energy and take it to a heat sink is needed. Spain has the compromise of delivering such device and CIEMAT (Centro de Investigaciones Energ��ticas Medioambientales y Tecnol��gicas) is responsible for such task. The central piece of the beam dump, where the ion beam is stopped, is a copper cone with an angle of 3.5o, 2.5 m long and 5 mm width. This part is cooled by water flowing on its external surface through the channel formed between the copper cone and a concentric piece with the latter. The thesis is developed in this realm, and its objective is designing the LIPAc beam dump cooling system. The design has been performed employing a simplified one dimensional model. The water parameters (pressure, flow, pressure loss) and the required annular channel geometry (width, rugoisty) have been obtained guaranteeing the correct cooling of the beam dump. It has been checked that the cooling design allows variations of the the beam with respect to the nominal position, being the CHF (Critical Heat Flux) at least twice times higher than the nominal deposited heat flux. 3D fluid dynamic simulations employing ANSYS-CFX code in the beam dump cooling channel sections which require a more thorough study have also been performed. The beam dump will activateasaconsequenceofthe deuteron beam interaction, making impossible any change or maintenance task once the accelerator operation has started. Hence the design has to be very robust and all the hypotheses employed in the design mustbecarefully checked. Most of the work in the thesis is concentrated in estimating the heat transfer coefficient which is decisive in the obtained results, and is also employed as boundary condition in the mechanical analysis. For such task, correlations which applicability range is the adequate for the beam dump conditions (annular channel, water-surface temperature differences of tens of degrees) have been compiled. In a second step the heat transfer coefficients obtained from the selected correlation (Petukhov- Gnielinski) have been compared with the ones deduced from the 3D fluid dynamic simulations, obtaining satisfactory results. Finally an experimental validation has been performed employing a prototype and a hydraulic circuit that supplies a flow with the requested parameters in the beam dump. After several tries and improvements in the experiment, the heat transfer coefficients for different flows and heating powers have been obtained. Considering the uncertainty in the measurements the experimental values agree reasonably well (in the order of 15%) with the ones obtained from the correlations. Due to radiological reasons the quality of the cooling water must be controlled, hence minimizing the copper corrosion. After performing a bibligraphic study the most adequate water parameters were identified (conductivity, pH and dissolved oxygen concentration). As part of this thesis a corrosion study of the beam dump cooling circuit has been performed with the double aim of determining if corrosion can pose a risk for the copper beam dump , and obtaining an estimation of the corrosion velocitytodimension the water purification system. TRACT code(TRansport and ACTivation) has been employed for such study adapting the code for the beam dump case. For such study a collaboration with the code responsible (Panos Karditsas) at Culham (UKAEA) was established. The work developed in this thesis has supposed the publication of three articles in JCR journals (���Journal of Nuclear Materials��� y ���Fusion Engineering and Design���), as well as presentations in more than four conferences and relevant meetings.

A nonlinear analysis of laying a floating pipeline on the seabed

In this article, a model for the determination of displacements, strains, and stresses of a submarine pipeline during its construction is presented. Typically, polyethylene outfall pipelines are the ones treated by this model. The process is carried out from an initial floating situation to the final laying position on the seabed. The following control variables are considered in the laying process: the axial load in the pipe, the flooded inner length, and the distance of the control barge from the coast. External loads such as self-weight, dead loads, and forces due to currents and small waves are also taken into account.This paper describes both the conceptual framework for the proposed model and its practical application in a real engineering situation. The authors also consider how the model might be used as a tool to study how sensitive the behavior of the pipeline is to small changes in the values of the control variables. A detailed description of the actions is considered, especially the ones related to the marine environment such as buoyancy, current, and sea waves. The structural behavior of the pipeline is simulated in the framework of a geometrically nonlinear dynamic analysis. The pipeline is assumed to be a two-dimensional Navier_Bernoulli beam. In the nonlinear analysis an updated Lagrangian formulation is used, and special care is taken regarding the numerical aspects of sea bed contact, follower forces due to external water pressures, and dynamic actions. The paper concludes by describing the implementation of the proposed techniques, using the ANSYS computer program with a number of subroutines developed by the authors. This implementation permits simulation of the two-dimensional structural pipe behavior of the whole construction process. A sensitivity analysis of the bending moments, axial forces, and stresses for different values of the control variables is carried out. Using the techniques described, the engineer may optimize the construction steps in the pipe laying process

Metodolog��a de simulaci��n num��rica de la transferencia de calor por ebullici��n en pel��cula en torno a superficies esf��ricas refrigeradas por l��quido saturado en convecci��n libre: aplicaci��n a reactores nucleares de lecho de bolas (PBR)

En la presente Tesis se realiz�� un an��lisis num��rico, usando el c��digo comercial Ansys-Fluent, de la refrigeraci��n de una bola de combustible de un reactor de lecho de bolas (PBR, por sus siglas en ingl��s), ante un escenario de emergencia en el cual el n��cleo sea desensamblado y las bolas se dejen caer en una piscina de agua, donde el mecanismo de transferencia de calor inicialmente ser��a la ebullici��n en pel��cula, implicando la convecci��n y la radiaci��n al fluido. Previamente se realizaron pruebas de validaci��n, comparando los resultados num��ricos con datos experimentales disponibles en la literatura para tres geometr��as diferentes, lo cual permiti�� seleccionar los esquemas y modelos num��ricos con mejor precisi��n y menor costo computacional. Una vez identificada la metodolog��a num��rica, todas las pruebas de validaci��n fueron ampliamente satisfactorias, encontr��ndose muy buena concordancia en el flujo de calor promedio con los datos experimentales. Durante estas pruebas de validaci��n se lograron caracterizar num��ricamente algunos par��metros importantes en la ebullici��n en pel��cula con los cuales existen ciertos niveles de incertidumbre, como son el factor de acoplamiento entre convecci��n y radiaci��n, y el factor de correcci��n del calor latente de vaporizaci��n. El an��lisis t��rmico de la refrigeraci��n de la bola del reactor por ebullici��n en pel��cula mostr�� que la misma se enfr��a, a pesar del calor de decaimiento, con una temperatura superficial de la bola que desciende de forma oscilatoria, debido al comportamiento inestable de la pel��cula de vapor. Sin embargo, la temperatura de esta superficie tiene una buena uniformidad, not��ndose que las ��reas mejor y peor refrigeradas est��n localizadas en la parte superior de la bola. Se observ�� la formaci��n de m��ltiples domos de vapor en diferentes posiciones circunferenciales, lo cual causa que el ��rea m��s caliente de la superficie se localice donde se forman los domos m��s grandes. La separaci��n entre los domos de vapor fue consistente con la teor��a hidrodin��mica, con la adici��n de que la separaci��n entre domos se reduce a medida que evolucionan y crecen, debido a la curvatura de la superficie. ABSTRACT A numerical cooling analysis of a PBR fuel pebble, after an emergency scenario in which the nucleus disassembly is made and the pebbles are dropped into a water pool, transmitting heat by film boiling, involving convection and radiation to the fluid, is carried out in this Thesis. First, were performed validation tests comparing the numerical results with experimental works available for three different geometries, which allowed the selection of numerical models and schemes with better precision and lower computational cost. Once identified the numerical methodology, all validation tests were widely satisfactory, finding very good agreement with experimental works in average heat flux. During these validation tests were achieved numerically characterize some important parameters in film boiling with which there are certain levels of uncertainty, such as the coupling factor between convection and radiation, and the correction factor of the latent heat of vaporization. The thermal analysis of pebble cooling by film boiling shows that despite its decay heat, cooling occurs, with pebble surface temperature descending from an oscillatory manner, due to the instability of the vapor film. However, the temperature of this surface has a good uniformity, noting that the best and worst refrigerated area is located at the top of the pebble. The formation of multiple vapor domes at different circumferential positions is observed, which cause that the hottest area of the surface was located where biggest vapor domes were formed. The separation between vapor domes was consistent with the hydrodynamic theory, with the addition that the separation is reduced as the vapor dome evolves and grows, due to the surface curvature.

Selected topics in the Hydrodynamics of floating offshore wind turbines: heave damping and second order surge motions

La Energ��a el��ctrica producida mediante tecnolog��a e��lica flotante es uno de los recursos m��s prometedores para reducir la dependencia de energ��a proveniente de combustibles f��siles. Esta tecnolog��a es de especial inter��s en pa��ses como Espa��a, donde la plataforma continental es estrecha y existen pocas ��reas para el desarrollo de estructuras fijas. Entre los diferentes conceptos flotantes, esta tesis se ha ocupado de la tipolog��a semisumergible. Estas plataformas pueden experimentar movimientos resonantes en largada y arfada. En largada, dado que el periodo de resonancia es largo estos puede ser inducidos por efectos de segundo orden de deriva lenta que pueden tener una influencia muy significativa en las cargas en los fondeos. En arfada las fuerzas de primer orden pueden inducir grandes movimientos y por tanto la correcta determinaci��n del amortiguamiento es esencial para la analizar la operatividad de la plataforma. Esta tesis ha investigado estos dos efectos, para ello se ha usado como caso base el dise��o de una plataforma desarrollada en el proyecto Europeo Hiprwind. La plataforma se compone de 3 columnas cil��ndricas unidas mediante montantes estructurales horizontales y diagonales, Los cilindros proporcionan flotabilidad y momentos adrizante. A la base de cada columna se le ha a��adido un gran ���Heave Plate��� o placa de cierre. El dise��o es similar a otros dise��os previos (Windfloat). Se ha fabricado un modelo a escala de una de las columnas para el estudio detallado del amortiguamiento mediante oscilaciones forzadas. Las dimensiones del modelo (1m di��metro en la placa de cierre) lo hacen, de los conocidos por el candidato, el mayor para el que se han publicado datos. El dise��o del cilindro se ha realizado de tal manera que permite la fijaci��n de placas de cierre planas o con refuerzo, ambos modelos se han fabricado y analizado. El modelo con refuerzos es una reproducci��n exacta del dise��o a escala real incluyendo detalles distintivos del mismo, siendo el m��s importante la placa vertical perimetral. Los ensayos de oscilaciones forzadas se han realizado para un rango de frecuencias, tanto para el disco plano como el reforzado. Se han medido las fuerzas durante los ensayos y se han calculado los coeficientes de amortiguamiento y de masa a��adida. Estos coeficientes son necesarios para el c��lculo del fondeo mediante simulaciones en el dominio del tiempo. Los coeficientes calculados se han comparado con la literatura existente, con c��lculos potenciales y por ultimo con c��lculos CFD. Para disponer de informaci��n relevante para el dise��o estructural de la plataforma se han medido y analizado experimentalmente las presiones en la parte superior e inferior de cada placa de cierre. Para la correcta estimaci��n num��rica de las fuerzas de deriva lenta en la plataforma se ha realizado una campa��a experimental que incluye ensayos con modelo cautivo de la plataforma completa en olas bicromaticas. Pese a que estos experimentos no reproducen un escenario de oleaje realista, los mismos permiten una verificaci��n del modelo num��rico mediante la comparaci��n de fuerzas medidas en el modelo f��sico y el num��rico. Como resultados de esta tesis podemos enumerar las siguientes conclusiones. 1. El amortiguamiento y la masa a��adida muestran una peque��a dependencia con la frecuencia pero una gran dependencia con la amplitud del movimiento. siendo coherente con investigaciones existentes. 2. Las medidas con la placa de cierre reforzada con cierre vertical en el borde, muestra un amortiguamiento significativamente menor comparada con la placa plana. Esto implica que para ensayos de canal es necesario incluir estos detalles en el modelo. 3. La masa a��adida no muestra grandes variaciones comparando placa plana y placa con refuerzos. 4. Un coeficiente de amortiguamiento del 6% del cr��tico se puede considerar conservador para el c��lculo en el dominio de la frecuencia. Este amortiguamiento es equivalente a un coeficiente de ���drag��� de 4 en elementos de Morison cuadr��ticos en las placas de cierre usadas en simulaciones en el dominio del tiempo. 5. Se han encontrado discrepancias en algunos valores de masa a��adida y amortiguamiento de la placa plana al comparar con datos publicados. Se han propuesto algunas explicaciones basadas en las diferencias en la relaci��n de espesores, en la distancia a la superficie libre y tambi��n relacionadas con efectos de escala. 6. La presi��n en la placa con refuerzos son similares a las de la placa plana, excepto en la zona del borde donde la placa con refuerzo vertical induce una gran diferencias de presiones entre la cara superior e inferior. 7. La m��xima diferencia de presi��n escala coherentemente con la fuerza equivalente a la aceleraci��n de la masa a��adida distribuida sobre la placa. 8. Las masas a��adidas calculadas con el c��digo potencial (WADAM) no son suficientemente precisas, Este software no contempla el modelado de placas de peque��o espesor con dipolos, la poca precisi��n de los resultados aumenta la importancia de este tipo de elementos al realizar simulaciones con c��digos potenciales para este tipo de plataformas que incluyen elementos de poco espesor. 9. Respecto al c��digo CFD (Ansys CFX) la precisi��n de los c��lculos es razonable para la placa plana, esta precisi��n disminuye para la placa con refuerzo vertical en el borde, como era de esperar dado la mayor complejidad del flujo. 10. Respecto al segundo orden, los resultados, en general, muestran que, aunque la tendencia en las fuerzas de segundo orden se captura bien con los c��digos num��ricos, se observan algunas reducciones en comparaci��n con los datos experimentales. Las diferencias entre simulaciones y datos experimentales son mayores al usar la aproximaci��n de Newman, que usa ��nicamente resultados de primer orden para el c��lculo de las fuerzas de deriva media. 11. Es importante remarcar que las tendencias observadas en los resultados con modelo fijo cambiarn cuando el modelo este libre, el impacto que los errores en las estimaciones de fuerzas segundo orden tienen en el sistema de fondeo dependen de las condiciones ambientales que imponen las cargas ultimas en dichas l��neas. En cualquier caso los resultados que se han obtenido en esta investigaci��n confirman que es necesaria y deseable una detallada investigaci��n de los m��todos usados en la estimaci��n de las fuerzas no lineales en las turbinas flotantes para que pueda servir de gu��a en futuros dise��os de estos sistemas. Finalmente, el candidato espera que esta investigaci��n pueda beneficiar a la industria e��lica offshore en mejorar el dise��o hidrodin��mico del concepto semisumergible. ABSTRACT Electrical power obtained from floating offshore wind turbines is one of the promising resources which can reduce the fossil fuel energy consumption and cover worldwide energy demands. The concept is the most competitive in countries, such as Spain, where the continental shelf is narrow and does not provide space for fixed structures. Among the different floating structures concepts, this thesis has dealt with the semisubmersible one. Platforms of this kind may experience resonant motions both in surge and heave directions. In surge, since the platform natural period is long, such resonance can be excited with second order slow drift forces and may have substantial influence on mooring loads. In heave, first order forces can induce significant motion, whose damping is a crucial factor for the platform downtime. These two topics have been investigated in this thesis. To this aim, a design developed during HiPRWind EU project, has been selected as reference case study. The platform is composed of three cylindrical legs, linked together by a set of structural braces. The cylinders provide buoyancy and restoring forces and moments. Large circular heave plates have been attached to their bases. The design is similar to other documented in literature (e.g. Windfloat), which implies outcomes could have a general value. A large scale model of one of the legs has been built in order to study heave damping through forced oscillations. The final dimensions of the specimen (one meter diameter discs) make it, to the candidate���s knowledge, the largest for which data has been published. The model design allows for the fitting of either a plain solid heave plate or a flapped reinforced one; both have been built. The latter is a model scale reproduction of the prototype heave plate and includes some distinctive features, the most important being the inclusion of a vertical flap on its perimeter. The forced oscillation tests have been conducted for a range of frequencies and amplitudes, with both the solid plain model and the vertical flap one. Forces have been measured, from which added mass and damping coefficients have been obtained. These are necessary to accurately compute time-domain simulations of mooring design. The coefficients have been compared with literature, and potential flow and CFD predictions. In order to provide information for the structural design of the platform, pressure measurements on the top and bottom side of the heave discs have been recorded and pressure differences analyzed. In addition, in order to conduct a detailed investigation on the numerical estimations of the slow-drift forces of the HiPRWind platform, an experimental campaign involving captive (fixed) model tests of a model of the whole platform in bichromatic waves has been carried out. Although not reproducing the more realistic scenario, these tests allowed a preliminary verification of the numerical model based directly on the forces measured on the structure. The following outcomes can be enumerated: 1. Damping and added mass coefficients show, on one hand, a small dependence with frequency and, on the other hand, a large dependence with the motion amplitude, which is coherent with previously published research. 2. Measurements with the prototype plate, equipped with the vertical flap, show that damping drops significantly when comparing this to the plain one. This implies that, for tank tests of the whole floater and turbine, the prototype plate, equipped with the flap, should be incorporated to the model. 3. Added mass values do not suffer large alterations when comparing the plain plate and the one equipped with a vertical flap. 4. A conservative damping coefficient equal to 6% of the critical damping can be considered adequate for the prototype heave plate for frequency domain analysis. A corresponding drag coefficient equal to 4.0 can be used in time domain simulations to define Morison elements. 5. When comparing to published data, some discrepancies in added mass and damping coefficients for the solid plain plate have been found. Explanations have been suggested, focusing mainly on differences in thickness ratio and distance to the free surface, and eventual scale effects. 6. Pressures on the plate equipped with the vertical flap are similar in magnitude to those of the plain plate, even though substantial differences are present close to the edge, where the flap induces a larger pressure difference in the reinforced case. 7. The maximum pressure difference scales coherently with the force equivalent to the acceleration of the added mass, distributed over the disc surface. 8. Added mass coefficient values predicted with the potential solver (WADAM) are not accurate enough. The used solver does not contemplate modeling thin plates with doublets. The relatively low accuracy of the results highlights the importance of these elements when performing potential flow simulations of offshore platforms which include thin plates. 9. For the full CFD solver (Ansys CFX), the accuracy of the computations is found reasonable for the plain plate. Such accuracy diminishes for the disc equipped with a vertical flap, an expected result considering the greater complexity of the flow. 10. In regards to second order effects, in general, the results showed that, although the main trend in the behavior of the second-order forces is well captured by the numerical predictions, some under prediction of the experimental values is visible. The gap between experimental and numerical results is more pronounced when Newman���s approximation is considered, making use exclusively of the mean drift forces calculated in the first-order solution. 11. It should be observed that the trends observed in the fixed model test may change when the body is free to float, and the impact that eventual errors in the estimation of the second-order forces may have on the mooring system depends on the characteristics of the sea conditions that will ultimately impose the maximum loads on the mooring lines. Nevertheless, the preliminary results obtained in this research do confirm that a more detailed investigation of the methods adopted for the estimation of the nonlinear wave forces on the FOWT would be welcome and may provide some further guidance for the design of such systems. As a final remark, the candidate hopes this research can benefit the offshore wind industry in improving the hydrodynamic design of the semi-submersible concept.

Estudio del flujo sangu��neo para diferentes t��cnicas de implantaci��n de stents en bifurcaciones coronarias

Las enfermedades arteriales vienen presididas por la aterosclerosis, que es un proceso cr��nico de degeneraci��n, que evoluciona hacia la obstrucci��n de la luz arterial. La pared de la arteria se engrosa debido al dep��sito de elementos grasos tales como el colesterol. Los stents intraluminales son diminutas estructuras tubulares autoexpandibles de malla de metal, que se colocan dentro de la arteria coronaria despu��s de una angioplastia con bal��n para prevenir el cierre de dicha arteria. A pesar de estar dise��ados para ser compatibles con el tejido humano, a menudo se da una reacci��n en cadena de consecuencias indeseables. La reestenosis intra-stent es un problema creciente debido al importante incremento que se ha producido en la utilizaci��n del stent intracoronario como forma de revascularizaci��n percut��nea. Se habla de una incidencia global del 28%, siendo la causa principal de su aparici��n la proliferaci��n neointimal a trav��s de una compleja cascada de sucesos que pueden tardar meses en desarrollarse. Una de las reacciones m��s importantes es la trombosis o la formaci��n de una fina capa de co��gulo como respuesta a la presencia de un material extra��o. Este proceso es multifactorial, y en ��l intervienen la regresi��n de la pared como consecuencia del estiramiento previo, la denudaci��n endotelial, lo que permite la agregaci��n plaquetaria, la proliferaci��n neointimal, lo que facilita a los receptores de membrana desencadenar un proceso de agregaci��n posterior y, por ��ltimo, el remodelado negativo inadecuado de la pared, lo que produce p��rdida de luz arterial. Se ha observado frecuentemente que el dep��sito de ateroma en la pared arterial est�� relacionado con el valor de los esfuerzos cortantes en la misma. Hay mayores probabilidades de engrosamiento de la pared en las zonas donde son bajos los esfuerzos cortantes, quiz�� por el mayor tiempo de residencia de las part��culas circulantes por el torrente sangu��neo. Si nos centramos en la afirmaci��n anterior, el siguiente paso ser��a buscar las zonas susceptibles de presentar un valor bajo de dichos esfuerzos. Las zonas potencialmente peligrosas son los codos y bifurcaciones, entre otras. Nos hemos centrado en una bifurcaci��n coronaria, ya que los patrones de flujo que se suelen presentar, tales como recirculaci��n y desprendimiento de v��rtices est��n ��ntimamente relacionados con las t��cnicas de implantaci��n de stents en esta zona. Proyectamos nuestros esfuerzos en el estudio de dos t��cnicas de implante, utilizando un ��nico stent y una tercera a trav��s de una configuraci��n de culotte con el uso de dos stents. El primer caso trata de una bifurcaci��n con un ��nico stent en la rama principal cuyos struts cierran el orificio lateral que da salida a la rama secundaria de la bifurcaci��n, es decir ser��a un stent sin orificio. El segundo consiste en un ��nico stent tambi��n, pero con la diferencia de que ��ste presenta un orificio de comunicaci��n con la rama lateral. Todas estas t��cnicas se aplicaron a bifurcaciones de 45�� y de 90��. Introdujimos las geometr��as -una vez confeccionadas con el c��digo comercial Gambit- en el programa Ansys-Fluent contemplando r��gimen estacionario. Los resultados obtenidos fueron cotejados con los experimentales, que se realizaron paralelamente, con el fin de corroborarlos. Una vez validados, el estudio computacional ya cont�� con la fiabilidad suficiente como para abordar el r��gimen no estacionario, tanto en la versi��n de reposo como en la de ejercicio ���hiperemia- El comportamiento reol��gico de la sangre para r��gimen no estacionario en estado de reposo es otra de las tareas abordadas, realizando una comparativa de los modelos Newtoniano, Carreau y Ley de Potencias. Finalmente, en una ��ltima etapa, debido a la reciente incursi��n de los stents dise��ados espec��ficamente frente a los convencionales, se aborda el comportamiento hemodin��mico de los mismos. Concretamente, se compar�� el patr��n de flujo en un modelo de bifurcaci��n coronaria con los nuevos stents (Stentys) y los convencionales. Se estudiaron cuatro modelos, a saber, stent simple en la rama principal, stent simple en la rama secundaria, culotte desplegando el primer stent en la rama principal y culotte desplegando el primer stent en la rama secundaria. La bifurcaci��n estudiada presenta un ��ngulo de apertura de 45�� y la relaci��n de di��metros de las ramas hija se ajustaron de acuerdo a la ley de Finet. Se recogieron resultados experimentales en el laboratorio y se corrieron simulaciones num��ricas con Ansys Fluent paralelamente. Las magnitudes que se tuvieron en cuenta con el fin de ubicar las regiones potencialmente ateroscler��ticas fueron los esfuerzos cortantes, vorticidad y ca��da de presi��n. ABSTRACT Nowadays, restenosis after percutaneous dilation is the major drawback of coronary angioplasty. It represents a special form of atherosclerosis due to the healing process secondary to extensive vessel trauma induced after intracoronary balloon inflation. The use of coronary stents may decrease the incidence of this phenomenon. Unfortunately, intra-stent restenosis still occurs in 20-30% of the cases following the stent implantation. Most experiments suggest a correlation between low wall shear stress and wall thickness. The preferential locations for the atherosclerotic plaque are bifurcations. The objective of this work is to analyze the local hemodynamic changes caused in a coronary bifurcation by three different stenting techniques: simple stenting of the main vessel, simple stenting of the main vessel with kissing balloon in the side branch and culotte. To carry out this study an idealized geometry of a coronary bifurcation is used, and two bifurcation angles, 45�� and 90��, are chosen as representative of the wide variety of real configurations. Both numerical simulations and experimental measurements are performed. First, steady simulations are carried out with the commercial code Ansys-Fluent, then, experimental measurements with PIV (Particle Image Velocimetry), obtained in the laboratory, are used to validate the numerical simulations. The steady computational simulations show a good overall agreement with the experimental data. Then, pulsatile flow is considered to take into account the transient effects. The time averaged wall shear stress, oscillatory shear index and pressure drop obtained numerically are used to compare the behavior of the stenting techniques. In a second step, the rheologic behavior of blood was considered comparing Newtonian, Carreau and Power Law models. Finally, as a result of previous investigations with conventional stents and after the recent emergence of several devices specifically designed for coronary bifurcations angioplasty, the hemodynamic performance of these new devices (Stentys) was compared to conventional ones and techniques in a coronary bifurcation model. Four different stenting techniques: simple stenting of the main vessel, simple stenting of the side vessel, culotte deploying the first stent in the main vessel and culotte deploying the first stent in the side vessel have been considered. To carry out this study an idealized geometry of a coronary bifurcation is used. A 45 degrees bifurcation angle is considered and the daughter branches diameters are obtained according to the Finet law. Both experiments in the laboratory and numerical simulations were used , focusing on important factors for the atherosclerosis development, like the wall shear stress, the oscillation shear index, the pressure loss and the vorticity.