Scipedia: Presentations on Computational Methods in Naval Architecture and Offshore Engineering

REFORMULACI ´ON DE LA MEC ´ANICA DE FLUIDOS

javier Jenaro Mac-Lrnnan — Tue, 21 May 2024 10:06:02 +0200

Utilizando la metodología contenida en mi artículo Acción sobre un codo de una tubería, publicado en la Revista de Obras Públicas en el año 2004, se llega a unas ecuaciones diferenciales que gobiernan el movimiento de una nave desde su rodadura en pista hasta su flotación y ascenso en el aire., con unos resultados de fácil utilización,

Seakeeping analysis of monohull ships at preliminary design using artificial neural networks

José Enrique Gutiérrez Romero — Tue, 20 Jul 2021 15:09:02 +0200

Nowadays seakeeping is mostly analysed by means of model testing or numerical models. Both require of a significant amount of time and of the exact hull geometry, and this is why seakeeping is not taken into account at the early stages of ship design. Then, the main objective of this work is the development of a seakeeping prediction tool to be used in the early design. Hence this tool must be fast, accurate, and must not require the exact hull shape. To this end, an artificial intelligence (AI) algorithm has been developed. This algorithm is based on artificial neural networks (ANN) and only requires the ship coefficients of forms.

The methodology developed to obtain the predictive algorithm is presented as well as the database of ships used for training the ANN. The training data were generated using a seakeeping code based on the boundary element method (BEM). Also, the AI predictions are compared to the BEM results using both, ship shapes from the training database and from outside.

As a result it has been obtained an AI tool capable of predicting seakeeping almost instantly for a wide range of monohull merchant ships. And the difference in results, with respect to the BEM code used for the training, is lower than 5%.

Procedure to Calibrate Composite Materials by Serial/Parallel Mixing Theory

Joel Jurado Granados — Tue, 21 May 2019 14:20:03 +0200

The use of composite materials in the naval industry is a fact. Prove of it is composite materials are widely used in the marine industry (e.g. competition vessels and leisure boats), offshore industry and renewable energy industry. If engineers want to design reliable structures made of composites, the numerical tools have to be capable of accurately representing the behaviour of these materials, such as their high anisotropy and non-linear performance. Hence, a good model capable of taking into account the different failure modes of the laminates is required in order to reduce the uncertainty associated with the simulation of composite structures.
There are many models capable of simulating the elastic and specific non-linear behaviour of laminates, while also accounting for their anisotropic behaviour. However, few of them are capable to take into account most of the composites failure modes in a general way. This work proposes using one of them, the Serial/Parallel Mixing Theory (SP RoM) [1].
The main advantage of the SP RoM versus other formulations is that the composite performance is obtained from the mechanical properties of its constituent materials. Therefore, once these are calibrated, different composite configurations can be analysed without further calibrations. The Serial/Parallel Mixing Theory (S/P RoM) acts as a constitutive law manager of the constituent
materials, being capable of reproducing the composite performance in its linear and non-linear regime. In order to obtain the material parameters required by the formulation, this work proposes a set of different tests to obtain different loading conditions and failure modes. Then, a guideline to get the material parameters from the tests is given. Finally, the numerical results are compared with results obtained from an experimental campaign. These results show that, once all the material parameters are obtained for fibre and matrix, the formulation introduced is capable of representing all the failure modes of the composite for different loading conditions, as well as their failure strength.
This work is in the scope of FibreShip Project H2020 [2].

REFERENCES

[1] F. Rastellni, S. Oller, O. Salomon, E. Oñate Composite materials non-linear modelling for long fibre reinforced laminates: continuum basis, computational aspects and validations, Computers & Structures, 86 (9) (2008), pp. 879–896
[2] European Union’s Horizon 2020 research and innovation programme under grant agreement nº 723360 “Engineering, production and life-cycle management for the complete construction of large-length FIBRE-based SHIPs”. http://www.fibreship.eu/about

Fatigue Simulation of a fibre-glass ship

Joel Jurado Granados — Tue, 21 May 2019 14:28:02 +0200

The use of composite materials to build marine structures is a fact. Prove of it is the construction of offshore turbines, military vessels, composite risers, etc. However, the characterization of such structures under fatigue loads is not well understood, what implies a larger scantling and safety ratios of the structures. Hence, it is necessary to develop numerical tools in order to predict this failure mode.

The purpose of this work is to propose a numerical model for the analysis of the fatigue behaviour of marine structures made of composite laminates, which can be used to understand their behaviour in order to optimize them.

The formulation proposed to simulate the fatigue phenomena is based on the Serial/Parallel Rule of Mixtures (S/P RoM) and a fatigue damage model previously developed for metals. The SPRoM can be understood as a constitutive law manager that provides the elastic and non-linear response of the composite from the constitutive performance of its constituent materials. The fatigue damage model is based on the definition of a reduction function which takes into account the cyclic degradation of the materials, acting on strength and stiffness; this function accounts for the number of cycles, maximum stress and stress amplitude. These two formulations are coupled applying the fatigue damage model to both composite components, fibre and matrix.

Current work uses the numerical procedure developed to characterize fatigue in composites. The model is calibrated based on the assumption that the failure mechanism of longitudinal loaded UD laminates is fibre-driven, while the failure mechanism of transverse loaded UD laminates is matrix-driven.

The composite resulting from this calibration is used, afterwards, to predict the fatigue performance laminated composites with different stacking sequences. The structure chosen for this analysis is a substructure of a fibreglass vessel.

This work is in the scope of FibreShip Project H2020.

Tool development for fully coupled simulation of offshore wind turbine

José Enrique Gutiérrez Romero — Wed, 15 May 2019 09:06:18 +0200

Nowadays the marine renewable energies are getting an important role in the transformation of the energy model. And tools for predicting the performance of these new technologies are essential in their commercial development. An example of these are floating wind turbines (FWT), and this work presents the coupling and verification of a set of tools to carry out fully coupled simulation of FWTs. These tools are built on the seakeeping software SeaFEM [1, 2, 3, 4, 5] and on the aeroelastic simulator code FAST [6].

First, the basic features of each tools are explained. Second, a coupling strategy to assess the performance of FWTs is presented. Third, the results obtained coupling SeaFEM-FAST are used for an inter-code comparison against those obtained coupling Hydrodyn-FAST. Forth, an intensive analysis of a FWT based on the NREL 5 MW baseline is carried out taking into account the environmental conditions of the selected location. These coupled computations are carried out following the Design Load Cases proposed by IEC rules [7] to assess the Ultimate Limit State (ULS). Finally, some comparison and conclusions based on the obtained results are drawn.

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

Borja Servan Camas — Fri, 10 May 2019 17:43:02 +0200

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.

Thermo-mechanical analysis of laminated composites exposed to fire

Rafael Pacheco-Blazquez — Mon, 13 May 2019 01:38:02 +0200

This presentation introduces a numerical model for the thermo-mechanical analysis of laminated composite structures under the fire action. The coupling between the thermal and mechanical behaviour is considered in weak form (temperatures field modify mechanical properties but displacements field do not modify thermal properties). The thermal part of model is based on the approach presented in Henderson et al. (1985). This model takes into account the energy transfer processes of heat conduction, pyrolysis of the polymer matrix, and diffusion of decomposition gases. The mechanical behaviour of the composites is based on the serial/parallel mixing theory (Rastellini et al., 2008) which is modified to take into account the thermal degradation of the mechanical properties. Numerical results obtained with this model are compared with some experimental tests presented in the literature. Application of the developed model to the analysis of fire scenarios in composite ships is evaluated.

Advances in the simulation of ship navigation in ice

Jonathan Colom Cobb — Fri, 10 May 2019 19:23:40 +0200

Navigation in the arctic regions is becoming more usual as new navigations routes are being opened due to the retreatment of the ice. This means that ships will be navigating in brash ice, which is the accumulation of floating ice made up of blocks no larger than two meters across, bringing up new concerns on the interaction of ice locks with the ship. In this work, we tackle these concerns and present the advances towards the development of a computational model for simulation of this navigation condition including the interaction among the ship and the ice blocks.

It has been shown [1][2] to successfully simulate a wide variety of complex engineering problems, e.g. free-surface/multi-fluid flows with violent interface motions, multi-fluid mixing and buoyancy-driven segregation problems etc.

The latest development within the framework of the PFEM is the X-IVAS (eXplicit Integration along the Velocity and Acceleration Streamlines) scheme [2][3]. It is a semi-implicit scheme built over a Semi-Lagrangian (SL) formulation of the PFEM.

In this work, the SL-PFEM model has been coupled with a multibody dynamics solver, able to handle the interactions between thousands of bodies, representing the different ice blocks. The interaction between the fluid flow and the ice blocks is taking into account by enriching the finite element space at the boundaries of the different blocks.

This work is part of the research project NICESHIP sponsored by the U.S. Office of Naval Research under Grant N62909-16-1-2236.

Advances in the Simulation of Ship Navigation in Brash Ice

Julio García-Espinosa — Thu, 19 Jul 2018 22:55:52 +0200

Brash ice is the accumulation of floating ice made up of blocks no larger than two meters across. Navigation in brash ice is becoming more usual as new navigation routes are being opened in the Artic regions. This navigation brings new concerns regarding the interaction of ice blocks with the ship. This work presents recent advances towards the development of a computational model for simulation of this navigation condition including the interaction among the ship and the ice blocks.

The computational tool developed in this work is based on the coupling of a Semi-Lagrangian Particle Finite Element Method (SL-PFEM) with a multi rigid-body dynamics tool. The Particle Finite Element Method (Idelsohn et al. 2004) is a versatile framework for the analysis of fluid-structure interaction problems. The PFEM combines Lagrangian particle-based techniques with the advantage of the integral formulation of the Finite Element Method (FEM). It has been shown (Idelsohn et al. 2014 and Nadukandi et al. 2017) to successfully simulate a wide variety of complex engineering problems, e.g. free-surface/multi-fluid flows with violent interface motions, multi-fluid mixing and buoyancy-driven segregation problems etc.

The latest development within the framework of the PFEM is the X-IVAS (eXplicit Integration along the Velocity and Acceleration Streamlines) scheme. It is a semi-implicit scheme built over a Semi-Lagrangian (SL) formulation of the PFEM.

This work is part of the research project NICESHIP sponsored by the U.S. Office of Naval Research under Grant N62909-16-1-2236.

Advances in the Simulation of Ship Navigation in Ice

Julio García-Espinosa — Tue, 19 Jun 2018 00:03:03 +0200

This work is part of the research project NICESHIP sponsored by the U.S. Office of Naval Research under Grant N62909-16-1-2236.

Nonlinear Finite Element Analysis of Mooring Cables on Marine Structures

Julio García-Espinosa — Mon, 05 Mar 2018 21:33:13 +0100

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. This presentation introduces a new time-domain model for solving the dynamics of moored floating marine devices, specifically offshore wind turbines, subjected to non-linear environmental loads.

Different application examples are presented,including a GVA, and the OC3 and OC4 platforms.

Challenges on computational models for ship design and navigation: Ongoing projects at CIMNE MARINE

Julio García-Espinosa — Sat, 18 Nov 2017 17:03:45 +0100

This presentation shows the recent work of the CIMNE in the maritime transport field. It was given at the Conference on Computation and Big Data in Transport (CM3-2017) held in November 22 – 23, 2017.

Coupled wave-structure analysis for naval and offshore applications

Julio García-Espinosa — Tue, 08 Aug 2017 21:20:02 +0200

Wave-structure interaction is a topic of great interest in naval and offshore engineering. This interest is growing in the last years due to the boost given by the development of the marine renewable energy field. In this context the development of an efficient time-domain coupled waves-structure solver is a main request from the industry.

Up to date the numerical seakeeping simulation has been mostly carried out using the frequency domain. The reason might be that the computational cost of time domain simulations were too high and computational time was too large. Moreover assumptions like linear waves and the harmonic nature of water waves made the frequency domain to be the right choice. However nowadays computing capabilities make possible to carry out numerical simulations in the time domain in a reasonable time, with the advantage of making easier the introduction of non-linearities into the algorithm and therefore coupling with other phenomena.

This presentation shows the work of the authors in developing a time-domain unstructured Finite Element Method (FEM) algorithm for analysis of coupled wave-structure interaction. For this purpose, a new diffraction-radiation solver using the FEM was developed. The solver has been implemented in GPU, using CUDA architecture. The speed-up obtained ranges from 5 to 10 times compare to the implementation in a standard CPU with a conjugate gradient and ILU preconditioner.

The seakeeping analysis tool has been integrated within a coupled waves-structure analysis tool. The coupling algorithm is based on a partitioned iterative algorithm, using an interpolation library able to communicate pressure forces and displacements of the structure at memory level. Furthermore, an innovative wetting and drying scheme able to improve the evaluation of the water action on the structure.

The accuracy of the new seakeeping formulation for analysis of waves and floating structures interaction has been verified in different validation cases and practical applications.