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This paper delves into the application of digital twin monitoring techniques for enhancing offshore floating wind turbine performance, with a detailed case study that uses open-source digital twin software. We explore the practical implementation of digital twins and their efficacy in optimizing operations and predictive maintenance, focusing on controlling the real-time structural state of composite wind turbine structures and forecasting the remaining useful life by tracking the fatigue state in the structure. Our findings emphasize digital twins’ potential as a valuable tool for renewable energy, driving efficiency and sustainability in offshore floating wind installations. These aspects, along with the aforementioned simulations, whether in real-time or forecasted, reduce costly and unnecessary inspections and scheduled maintenance., Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Postprint (published version)

This paper describes the research performed within the scope of H2020 project FIBRE4YARD in the development of a suitable thermo-mechanical framework to analyse composite structures under fire loads. The thermo-mechanical model uses the adiabatic temperature to obtain the through-thickness distribution of temperature of the triangular shell element, this formulation is able to predict phenomena such as pyrolysis, thermo-mechanical yielding and large displacements (non-linear buckling). An application case of a load-bearing section of a container ship is shown to demonstrate the correctness of the methodology, two type of materials are considered in the analysis, traditional materials such steel and advanced materials like fibre reinforced plastic (FRP) composites., Preprint

The current paradigm in ship design is focused in producing ships that are more environmental friendly. Lightweight or advanced materials are the perfect candidate to make ship transportation more efficient, however the current state-of-the-art is in demand of novel techniques that aid in the design of marine composite structures when exposed to fire. This paper aims to describe a technique that couples a fire dynamic simulator with a thermo-mechanical tool specialised in the calculus of laminated FRP structures, the application can be extended to other areas of engineering as well. An application of the technique is illustrated in the analysis of one of the decks of the superstructure of a Panamax containership where a fire has ignited and the active fire protection system is disabled. A second objective addressed in this paper is the discussion of the misconception that composites, although outperforming steel in several mechanical aspects, show a substantial lower thermo-mechanical performance. The research conducted here shows that composite are advantageous from the thermal point of view, and certainly have benefits in their thermo-structural response, specially when the life of human beings is under consideration., Preprint

This paper describes the research performed within the scope of H2020 project FIBRESHIP in the development and validation of a thermo-mechanical model to assess the fire performance of composite structures. A one-dimensional thermal model with pyrolysis is used to obtain the temperature profile across the thickness, and later, introduced in the thermo-mechanical model with a quadrilateral shell element approach. The composite constitutive model employed is the so-called Serial/Parallel Rule of Mixtures (SPROM) which has been modified to introduce the effect of the thermal deformation. A set of experimental tests are then used to validate the correctness of the numerical method proposed. The experimental data used to validate the thermal model is the classic Henderson experimental test. The thermo-mechanical coupling is validated against an original vertical furnace test of an FRP ship’s bulkhead, following on the 2010 FTP Code standards. These validations demonstrate the correctness and accuracy of the proposed decoupled thermo-mechanical formulation., Postprint (author's final draft)

A la pàgina XIX del Sumari manquen: la pàgina 333: "Original publications" i les pàgines 335 a 361 "Bibliography", The high strength-weight ratio of composite materials have made them one of the best materials for the design of light-weight structures. However, its special complexity has made them not suitable for the design of structures with a relative complexity or with numerous structural component and pieces. Hence, the importance in the development of adequate constitutive models which allow simulating the micro-macro scale interaction of composites, and to address the intrinsic and natural flexibility of composites that is not as relevant in traditional materials. Meanwhile, the mechanical development of these materials is a mature research branch with more than four groundbreaking decades of life, this is not certainly met at the thermo-mechanical level which is still in an early stage and, consequently, limiting the extensive use of composites in real world and complex structures, particularly structures in which a strong and detailed fulfilment of fire criteria is necessary. E.g., this is the very situation in the large-length ship design sector, where the share in the market for ships built using composite material, tends to be very reduced and closely accompanied by tools which serve to perform structural health monitoring, in order to palliate, the amount of high uncertainty of the present thermo-mechanical response, found in the design of these structures. The present thesis focuses on the development, formulation-wise and computational implementation, of a numerical model in order to predict the non-linear constitutive behaviour of fibre-reinforced plastic (FRP) composites exposed to thermal degradation due to high temperatures. This very model is cemented in the groundbreaking development of constitutive mechanical formulations specially tailored for composites also known as rule of mixtures -- in this present context, the formulation is the so-called serial-parallel rule of mixtures -- which establish a set of closure equations to obtain the suitable micro-macro, Per als materials compostos, la seva relació esforç-pes elevada ha fet d'ells un dels millors materials per al disseny d'estructures lleugeres. No obstant això, la seva especial complexitat, fa d'ells un difícil treball quan es tracta del disseny d'estructures amb una certa complexitat, o, en l'existència de nombroses divisions estructurals i peces. En conseqüència, el desenvolupament de models constitutius adients és de vital importància, en especial aquells que permeten la simulació de la interacció per la micro-macro escala dels compostos, i que resolguin la flexibilitat natural i intrínseca d'aquests materials avançats, qüestió que no és tan rellevant per al disseny de materials tradicionals. Mentrestant, el desenvolupament de teories mecàniques per aquests materials es troba ja a la seva maduració, amb més de quatre dècades de descobriments en aquesta branca. D'altra banda, en qüestions que involucren l'anàlisi termo-mecànica, el paradigma es considera relativament verd, el qual limita l'aplicació extensiva dels compostos en aplicacions pràctiques i d'estructures complexes, de fet, és particularment limitant en el disseny d'estructures que requereixen del compliment d'exigents i detallats criteris relatius al foc. E.g., això mateix succeeix en el disseny d'embarcacions de grans eslores, on la quota de mercat dels vaixells construïts mitjançant materials compostos sol ser reduïda, i estretament acompanyada per eines de monitoratge de la integritat estructural, per així poder pal·liar la gran incertesa vinculada a la resposta termo-mecànica, fruit de les capacitats del disseny comercial actual. L'actual tesi se centra en el desenvolupament, de manera teòrica, i amb corresponent implementació computacional, d'un model numèric capaç de predir el comportament no-linear constitutiu de compostos plàstics amb fibra embedida (FRP) quan aquests són exposats a altes temperatures i en conseqüència a la degradació tèrmica. Aquest mateix model està inspirat en els desenvolup, Para los materiales compuestos, su relación esfuerzo-peso elevada ha hecho de ellos uno de los mejores materiales para el diseño de estructuras ligeras. No obstante, su especial complejidad, hace de ellos un arduo trabajo cuando se trata del diseño de estructuras con una cierta complejidad, o, en la existencia de numerosas divisiones estructurales o piezas. Consecuentemente, el desarrollo de modelos constitutivos adecuados es de importancia, en especial aquellos que permiten la simulación de la interacción para la micro-macro escala de los compuestos, y que resuelven la flexibilidad natural e intrínseca de estos materiales avanzados, cuestión que no es tan relevante para el diseño de materiales tradicionales. Mientras tanto, el desarrollo de teorías mecánicas para estos materiales se encuentra en su madurez, con más de cuatro décadas de hallazgos en esta rama. En contraposición, en cuestiones que atañen el análisis termo-mecánico, el paradigma se encuentra relativamente verde, lo cual limita la aplicación extensiva de los compuestos en aplicaciones prácticas y estructuras complejas, de hecho, es particularmente limitante en el diseño de estructuras que requieren del cumplimiento de exigentes y detallados criterios relativos al fuego. E.g., esto mismo sucede en el diseño de embarcaciones de grandes esloras, donde la cuota de mercado de los buques construidos mediante materiales compuestos suele ser reducida, y estrechamente acompañada por herramientas de monitorización de la integridad estructural, para así poder paliar la gran incertidumbre vinculada a la respuesta termo-mecánica, fruto de las capacidades del diseño comercial actual. La actual tesis se centra en el desarrollo, de manera teórica, y con su correspondiente implementación computacional, de un modelo numérico capaz de predecir el comportamiento no-lineal constitutivo de compuestos plásticos con fibra embebida (FRP) cuando estos son expuestos a altas temperaturas y en consecuencia a la degradación térmica, Postprint (published version)

This paper analyzes the partitioned and monolithic strategies to simulate tightly coupled hidroelastic problems. The seakeeping hydrodynamics solver used is based on a first-order linear time-domain FEM model with forward speed and double-body linearization. The structural dynamics solver is based on a full 3D time-domain FEM with corotational shell elements accounting for the geometric non-linearity. Both solvers are implemented under the same programming framework, which allows to implement the monolithic strategy, and to minimize the communication overheads of the partitioned strategy. Two case studies are used to test and compare the partitioned and monolithic coupling: a flexible catamaran in oblique waves, and a large floating reticulated structure made of fiber reinforced plastic. In both cases, the monolithic strategy is between three and four times faster than the partitioned strategy. This project has been developed under the H2020 project FIBRESHIP aimed at developing the technology to design and build the structure of large-length vessels in fiber reinforced polymers., Peer Reviewed, Postprint (author's final draft)

In this paper a numerical model for thermo-mechanical analysis of laminated composite structures under fire exposure is presented. The analysis is solved using a decoupled approach where temperature modifies the mechanical properties of the constituent materials. The thermal model is based on the research by Henderson et al. [1, 2], which takes into account the energy transfer processes of heat conduction, pyrolysis of the polymer resin and diffusion of decomposed gases. The mechanical model is based on finite element shell elements [3] and the laminated constitutive model is based on damage theory [4, 5, 6] and the serial-parallel rules of mixtures by Rastellini et al. [7], both have been adaptedto introduce the thermal expansion effect and thermal degradation of mechanical properties similar as described by Mouritz [8, 9, 10, 11] and Gibson [12, 13, 14, 15]. The boundary conditions introduced in the thermal model are obtained from a fire dynamics simulation (FDS) [16]. Finally, an application case of a fire collapse analysis of a structure exposed to a fire scenario is presented, the latter specifically demonstrates how the structural integrity of divisions of large-length composite vessels evolves under fire load., This work was funded thanks to H2020 project FIBRESHIP sponsored by the EUROPEAN COM- MISSION under the grant agreement 723360 ”Engineering, production and life-cycle management for complete construction of large-length FIBRE-based SHIPs”. www.fibreship.eu/about And part of the research project NICESHIP sponsored by the Spanish Ministry of Science and Inno- vation under Grant RTI2018-094744-B-C21., Peer Reviewed, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Postprint (published version)

This thesis covers the implementation of a new tool to solve fluid problems capable of solving free-surface and fluid-solid interfaces. This tool is based on a Semi-Lagrangian Particle Finite Element Method (SL-PFEM) approach of solve the Navier-Stokes equations. In a similar fashion to the Particle Finite Element Method (PFEM) and its second generation version (PFEM-2), Lagrangian particles are used to solve the convection problem while a background mesh is used to solve the elliptic part of the Navier-Stokes equations. One of the objectives is that the tool must be efficient when calculating problems. This is managed by first developing the numerical scheme so that it is second order accurate in time and space and then optimising the implementation so that it can perform well in HPC environments. To solve the general interface problems such as fluid-fluid, fluid-solid or the two combined, then an enrichment method is applied to the scheme. This, joined with an SL-PFEM variation of the Level-Set Method allows to accurately capture and compute these types of problems. This implementation leads to the ability to solve multi-body problems that can interact with multiple fluids., Esta tesis trata sobre la implementación de una nueva herramienta para resolver problemas fluidodinámicos tratando, en particular, los problemas de interfaces fluido-fluido y sólido-fluido. Esta herramienta está basada en el "Semi-Lagrangian Particle Finite Element Method" (SL-PFEM) para resolver las ecuaciones de Navier-Stokes. De manera similar al "Particle Finite Element Method" (PFEM) y su segunda versión (PFEM-2), partículas Lagrangianas son usadas para resolver el problema de convección mientras que una malla fija se usa para resolver la parte elíptica de las ecuaciones de Navier-Stokes. Uno de los objetivos es que la herramienta debe ser capaz de resolver los problemas de manera eficiente. Para ello, primero se desarrolla el esquema numérico para que sea un esquema de segundo orden tanto en espacio y tiempo y, luego, se optimiza la implementación para obtener un buen rendimiento en entornos de supercomputación. Para resolver problemas de interfaces como los de fluido-fluido, solido-fluido o la combinación de ambas, un método de enriquecimiento es aplicado al esquema numérico. Esto, junto con una variación del método "Level-Set" aplicado al SL-PFEM permite capturar y calcular de forma precisa estos tipos de problemas. Además, esta implementación lleva a la capacidad de resolver problemas con más de un cuerpo que puedan interactuar con varios fluidos., Postprint (published version)

This paper describes the behaviour of large-length ships built using fibre-reinforced plastic compositematerials under fire and large deformations. A novel methodology is proposed in order to analyseinelastic buckling and post-buckling of steel structures due to thermal loading and also extend thisto the phenomenon regarded as pyrolysis that is natural in composite structures. The methodologyis validated against the literature. A model of a container-ship where a fire scenario located in theengine room is used to demonstrate the methodology against a real case scenario. The section of thecargo hold closest to the engine room is structurally analysed, focusing in the integrity of the bulkheadand the supports of the TEU containers., This work was funded thanks to H2020 project FIBRESHIP sponsored by the EUROPEAN COM- MISSION under the grant agreement 723360 ”Engineering, production and life-cycle management for complete construction of large-length FIBRE-based SHIPs, Peer Reviewed, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Postprint (author's final draft)

The application of composite materials in large-length shipbuilding is attracting considerable attention thanks to their significant expected structural weight reduction, resulting in advantages such as bunkering savings, lower greenhouse gas emissions, higher payload cargo capacity, or suppression of corrosion problems, which might produce maintenance costs reduction. The H2020 European research project FIBRESHIP (EU 2020) aims to develop the technologies required to use composites in large length ships. The project covers all aspects required to make reality this new generation of ships, from materials to shipyard requirements; from the numerical tools required for designing fibreships, to the development of guidelines and rules that define how this design should be made. Current work presents the main work conducted in the field of material selection and characterization, numerical tools developments, and shipyard requirements., Postprint (published version)

Tesi amb "Menció Internacional": capítols 1-4, 12-13 escrits en anglès i castellà, resta de la tesi en anglès. La tesi es publica amb una secció retallada per drets de l'editor., A new thin shell finite element is presented. This new element doesn’ t have rotational degrees of freedom. Instead, in order to overcome the C1 continuity requirement across elements, the author resorts to enhance the geometric description of the flat triangles of a mesh made out of linear triangles, by means of Bernstein polynomials and triangular Bernstein-Bézier patches. The author estimates the surface normals at the nodes of a mesh of triangles, in order to use them to define the Bernstein-Bézier patches. Ubach, Estruch and García-Espinosa performed a comprehensive statistical comparison of different weighting factors. The conclusion of that work is that the inverse of the area of the circumscribed circle to the triangle and the internal angle of the triangle at the node considered, should be used as weighting factor. Using this new weighting factor, we reduce by about 10% the root mean square error in the estimation of normals of randomly generated surfaces with respect to the previous best weighting factor found in the literature. The author uses the information of the normal vectors at the nodes and the triangular Bernstein-Bézier patches to build cubic Bézier triangles. These cubic Bézier triangles are surface interpolants; C1 continuous at the nodes and C0 continuous across the edges. Owing to this approach, the new element is called Bézier-enhanced shell triangle (BEST). The BEST element takes advantage of all the nodes’ connectivities in each triangle of the mesh. The computation of the normal vectors at the nodes doesn’ t depend on the number of triangles surrounding each node of the mesh. The BEST element is independent from the mesh topology. A new paradigm is presented consisting on the reconstruction of the geometry of a cubic triangular element. This geometric reconstruction exploits the properties of cubic B-spline functions (cubic Bézier triangle). This way, the author builds a conforming continuum-based shell finite element. A cubic Bézier tria, Se presenta un nuevo elemento finito de lámina delgada. Este nuevo elemento no usa rotaciones como grados de libertad. En su lugar, para sortear el requisito de mantener continuidad C1 entre elementos, el autor mejora la descripción geométrica de los triángulos planos de una malla de triángulos lineales, por medio de polinomios de Bernstein y particiones triangulares de Bernstein-Bézier. Para definir las particiones de Bernstein-Bézier, el autor estima las normales a la superficie en los nodos de una malla de triángulos. Ubach, Estruch y García-Espinosa hicieron una comparación estadística exhaustiva entre distintos factores de ponderación. La conclusión de dicho trabajo conduce a usar como factor de ponderación: el inverso del área de la circunferencia circunscrita al triángulo y el ángulo interno del triángulo en el nodo considerado. Con este nuevo factor de ponderación, se reduce en aproximadamente un 10% el error medio cuadrático cometido en la estimación de las normales de superficies generadas aleatoriamente, respecto del mejor factor usado previamente en la literatura. Con la información de los vectores normales en los nodos, el autor construye triángulos cúbicos de Bézier. Estos triángulos cúbicos de Bézier interpolan la superficie; con continuidad C1 en los nodos y C0 en las aristas. En virtud a este planteamiento, el nuevo elemento recibe el nombre de BEST. El elemento BEST aprovecha todas las conectividades nodales de cada triángulo de la malla. El número de triángulos que rodean cada nodo de la malla no afecta al cálculo de los vectores normales. El elemento BEST es independiente de la topología de la malla. Se propone un nuevo paradigma que consiste en reconstruir la geometría de un elemento triangular cúbico. Esta reconstrucción geométrica aprovecha las propiedades de las funciones cúbicas B-spline (triángulo cúbico de Bézier). Así, el autor crea un elemento de lámina conforme basado en el continuo. Un triángulo cúbico de Bézier tiene 30 parámetros (3, Es presenta un nou element finit de làmina prima. Aquest nou element no fa servir rotacions com a graus de llibertat. Enlloc d'això, per esquivar el requisit de mantenir continuïtat C1 entre els elements, l'autor millora la descripció geomètrica dels triangles plans d'una malla de triangles lineals, mitjançant polinomis de Bernstein i particions triangulars de Bernstein-Bézier. Per definir les particions de Bernstein-Bézier, l'autor estima les normals a la superfície en els nodes d'una malla de triangles. Ubach, Estruch i García-Espinosa varen fer una comparació estadística exhaustiva entre diferents factors de ponderació. La conclusió d'aquest treball condueix a fer servir com a factor de ponderació: l'invers de l'àrea de la circumferència circumscrita al triangle i l'angle intern del triangle en el node considerat. Amb aquest nou factor de ponderació, es redueix aproximadament en un 10% l'error quadràtic mig comès en l'estimació de les normals de superfícies generades aleatòriament, respecte del millor factor usat prèviament a la literatura. Amb la informació dels vectors normals en els nodes, l'autor construeix triangles cúbics de Bézier. Aquests triangles cúbics de Bézier interpolen la superfície; amb continuïtat C1 als nodes i C0 a les arestes. En virtut d'aquest plantejament, el nou element rep el nom de BEST (Bézier-enhanced shell triangle). L'element BEST aprofita totes les connectivitats nodals de cada triangle de la malla. El nombre de triangles que envolten cada node de la malla no afecta al càlcul dels vectors normals. L'element BEST és independent de la topologia de la malla. Es proposa un nou paradigma que consisteix en reconstruir la geometria d'un element triangular cúbic. Aquesta reconstrucció geomètrica aprofita les propietats de les funcions cúbiques B-spline (triangle cúbic de Bézier). D'aquesta manera l'autor crea un element de làmina que és conforme i basat en el continu. Un triangle cúbic de Bézier té 30 paràmetres (3 coordenades per cadascun, Postprint (published version)

The aim of this master’s thesis is to extend the functionalities of a simulation of marine devices program, seafem, by coupling it to a control simulation program, simulink, through a communication interface following a tcp/ip protocol. thus, more complex external loads could be applied on the model to simulate. to verify and demonstrate the correct functioning of the suggested system it has been used to solve two situations: finding the power produced from the flux going through the turbine of an oscillating water column device and finding the reduction of the roll due to the effect of the stabilizing fins installed onboard a wigley type hull introducing a control algorithm. finally, this last case has been applied in more adverse sea conditions similar to reality. En este Trabajo Final de Máster se ha pretendido extender las capacidades de un programa de simulación de artefactos marinos, SeaFEM, acoplándolo con un programa de simulación de control, Simulink, mediante una interfaz de comunicación siguiendo un protocolo TCP/IP. De esta manera, se podrían aplicar cargas externas más complejas y bajo un algoritmo de control sobre el modelo a simular. Para verificar y demostrar el correcto funcionamiento del sistema propuesto se han resueltodos situaciones: conocer la potencia producida a partirdel flujo que circula a través de la turbina de una columna de agua oscilante y la reducción del balance debida al efecto de las aletas estabilizadoras instaladas en un casco de tipo Wigley introduciendo así un algoritmo de control. Finalmente, este último caso se ha aplicado en unas condiciones de mar más adversas,similares a las reales.

Ocean turbulence is a classic example of turbulent motion and observations of turbulence in the ocean lack in regions of complex topography since in-situ and experimental data are complicated to obtain. As a result, ocean circulation and flow interaction with obstacles such as seamounts and submarine canyons rely heavily on modelling and numerical simulation such that these are the only tools that can provide insights and ideas which are essential to the scientific community. This research investigated the capability of a stabilized finite element method (SFEM) based on the finite increment calculus (FIC) procedure, which is one of the most promising approaches to numerically simulate turbulent flows with particular interest in its application in simulating oceanic turbulence. The use of the FIC procedure allows solution of a wide range of fluid flow problems without the need of a turbulence model. The available numerical model was first validated through numerical simulations of various test cases such as Taylor-Couette flow, Ekman spiral, lock-exchange flow and circulation driven by oscillatory forcing over a theoretical submarine canyon model. Excellent qualitative agreement with available numerical and experimental data was obtained through minimal modification of the numerical model using TCL programming codes. To improve on modeling capabilities, which eventually allowed simulation of oceanic turbulence, a systematic modification of the numerical model was done by introducing additional paramaters on the governing equation, which is the incompressible Navier-Stokes equations. The resulting stabilized finite element equation was subsequently implemented into the numerical model, and the modification produced a coastal ocean model version. It was validated through numerical simulations of flow in coastal areas affected by topography, upwelling flow and submarine canyon. These flows are particularly reliant on numerical simulation, as the extreme nature of their, Postprint (published version)