A non-linear finite element method on unstructured meshes for added resistance in waves

In this work a finite element method is proposed to solve the problem of estimating the added resistance of a ship in waves in the time domain and using unstructured meshes. Two different schemes are used to integrate the corresponding free surface kinematic and dynamic boundary conditions: the first one based on streamlines integration; and the second one based on the streamline-upwind Petrov–Galerkin stabilisation. The proposed numerical schemes have been validated in different test cases, including towing tank tests with monochromatic waves. The results obtained in this work show the suitability of the present method to estimate added resistance in waves in a computationally affordable manner.Postprint (author's final draft

Advances in the development of a time-domain unstructured finite element method for the analysis of waves and floating structures interaction

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Non-linear dynamic analysis of the response of moored floating structures

© 2016 Elsevier Ltd. The complexity of the dynamic response of offshore marine structures requires advanced simulations tools for the accurate assessment of the seakeeping behaviour of these devices. The aim of this work is to present a new time-domain model for solving the dynamics of moored floating marine devices, specifically offshore wind turbines, subjected to non-linear environmental loads. The paper first introduces the formulation of the second-order wave radiation-diffraction solver, designed for calculating the wave-floater interaction. Then, the solver of the mooring dynamics, based on a non-linear Finite Element Method (FEM) approach, is presented. Next, the procedure developed for coupling the floater dynamics model with the mooring model is described. Some validation examples of the developed models, and comparisons among different mooring approaches, are presented. Finally, a study of the OC3 floating wind turbine concept is performed to analyze the influence of the mooring model in the dynamics of the platform and the tension in the mooring lines. The work comes to the conclusion that the coupling of a dynamic mooring model along with a second-order wave radiation-diffraction solver can offer realistic predictions of the floating wind turbine performance.Postprint (published version

Seakeeping with the semi-Lagrangian particle finite element method

The application of the semi-Lagrangian Particle Finite Element Method (SL–PFEM) for the seakeeping sim-ulation of the Wave Adaptive Modular Vehicle under spray generating conditions is presented. The time integration of the Lagrangian advection is done using the explicit integra-tion of the velocity and acceleration along the streamlines (X-IVAS). Despite the suitability of the SL–PFEM for the considered seakeeping application, small time steps were needed in the X-IVAS scheme to control the solution accu-racy. A preliminary proposal to overcome this limitation of the X-IVAS scheme for seakeeping simulations is presented.Postprint (author's final draft

Experiencias en el desarrollo y aplicación de herramientas de cálculo y verificación de estructuras marinas para generación de energía

En los últimos años se ha despertado un enorme interés por la obtención de energía de fuentes renovables, siendo el mar uno de los principales focos de este interés. La razón principal es la enorme disponibilidad de energía en este medio, tanto en forma de viento, como de corrientes, diferencias de temperatura, oleaje y mareas. A raíz de este interés, se han invertido importantes recursos en el desarrollo de plantas para la extracción de energía de las diferentes fuentes mencionadas. De manera no exhaustiva, podemos mencionar los aerogeneradores, las plantas de extracción de energía de las olas, de corrientes, las presas de marea, los conversores de energía térmica del océano, generadores por diferencias de presión osmótica y de columna de agua oscilante. En este trabajo se presentan las experiencias de la empresa Compass Ingeniería y Sistemas S.A. (CompassIS) y del grupo de investigación naval del Centro Internacional de Métodos Numéricos en Ingeniería (CIMNE), en el desarrollo de herramientas de predicción de cargas, de cálculo y verificación de estructuras, así como de comportamiento en la mar. Finalmente se mostrarán diferentes ejemplos prácticos de aplicación al diseño de diferentes estructuras marinas de obtención de energía, desarrollados para varias empresas de relevancia en este campo. Over the last years great interest has developed in the harvesting of power from renewable resources. The sea has been a main focus of this development. The reason is the huge amount of energy available as waves, marine currents, thermal energy, tidal and wind waves. Significant resources have been invested in the development of plants to harvest the energy of the ocean in the different mentioned sources. For example, we can mention wind turbines, waves and marine-current energy converters, tidal barrages, ocean thermal energy converters OTEC, oscillating water column devices (OWC) and osmotic-pressure difference systems. In this work, the experiences of the company Compass Ingeniería y Sistemas S.A. (CompassIS) and the naval research group of the Internacional Center for Numerical Methods in Engineering (CIMNE) in the development of tools for sea loads prediction, structural design and verification, and seakeeping, will be presented. Several examples of application of these tools to the design of offshore energy converters will be introduced, including offshore wind turbines, oscillating water column devices and wave energy harvesting systems developed for some stakeholders in this field.Postprint (published version

A second-order semi-Lagrangian particle FEM method for the incompressible NavierStokes equations

In this work, a second-order semi-Lagrangian particle finite element method (SL-PFEM) is presented. The method is based on the second order velocity Verlet algorithm, using an explicit scheme to integrate the particles’ trajectories, and an implicit Crank-Nicholson scheme to integrate the particle’s velocities. The projection of the particle´s intrinsic variables onto the finite element (FE) mesh is based on a second-order global least-square. The elliptic part of the Navier-Stokes equations is discretized with the Crank-Nicholson scheme and solved using an iterative process. The method is verified against available analytical solutions, and applied to the classic flow around a cylinder problem

A second-order semi-lagrangian particle finite element method for fluid flows

In this paper, a second-order SL-PFEM scheme for solving the incompressible Navier–Stokes equations is presented. This scheme is based on the second-order velocity Verlet algorithm, which uses an explicit integration for the particle’s trajectory and an implicit integration for the velocity. The algorithm is completed with a predictor–multicorrector scheme for the integration of the velocity correction using the finite element method. A second-order projector based on least squares is used to transfer the intrinsic variable information from the particles to the background mesh, while a second-order interpolation scheme is used to transfer the accelerations from the mesh to the particles. Convergence analyses are carried out to assess the second-order convergence.Postprint (published version

Fully 3D ship hydroelasticity: Monolithic versus partitioned strategies for tight coupling

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 ReviewedPostprint (author's final draft

A time-domain second-order FEM model for the wave diffraction radiation problem. Validation with a semisubmersible platform

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