Scipedia: Collection of Papers on Computational Methods in Naval Architecture and Offshore Engineering

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

Julio García-Espinosa — Mon, 04 Nov 2019 20:13:06 +0100

A finite element method for the solution of the up-to-second-order wave diffraction-radiation problem in the time-domain is proposed. The solver has been verified against available analytical solutions, and validated against experimental data available for the HiPRWind semisubmersible platform (designed for floating wind turbines). To perform the validation, the wave diffraction-radiation solver is coupled to a body dynamics and mooring solvers in the time-domain. The HiPRWind movements and mooring forces have been compared for a large number of test cases, including decay tests, monochromatic waves, and bichromatic waves obtaining good agreement for both, body movements and mooring forces.

Seakeeping with the semi-Lagrangian particle finite element method

Julio García-Espinosa — Thu, 11 Apr 2019 19:11:02 +0200

The application of the semi-Lagrangian particle finite element method (SL–PFEM) for the seakeeping simulation of the wave adaptive modular vehicle under spray generating conditions is presented. The time integration of the Lagrangian advection is done using the explicit integration 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 accuracy. A preliminary proposal to overcome this limitation of the X-IVAS scheme for seakeeping simulations is presented.

A real-time decision support system for the adjustment of sailboat rigging

Julio García-Espinosa — Thu, 11 Apr 2019 19:08:02 +0200

The operational complexity and performance requirements of modern racing yachts demand the use of advanced applications, such as a decision support system (DSS) able to assist crew members during navigation. In this article, the authors describe a near-time computational solver as the main piece of a DSS which analyses and monitors the behaviour of sails and rigging. The solver is made up of two different interconnected tools: an iterative FluidStructure Interaction algorithm and an advanced Wireless Sensor Network to monitor rigging. The real-time DSS quantifies crew manoeuvres in physical terms, which are reproduced by a simulation program. It can be used in the design phase of sailing yachts and as an aid for realtime boat performance optimisation and accident prevention. This novel DSS is a useful tool for navigation, especially in races.

An unstructured finite element solver for ship hydrodynamics problems

Julio García-Espinosa — Wed, 10 Apr 2019 22:07:03 +0200

A stabilized semi-implicit fractional step algorithm based on the ﬁnite element method for solving ship wave problems using unstructured meshes is presented. The stabilized gov-erning equations for the viscous incompressible ﬂuid and the free surface are derived at a differential level via a ﬁnite calculus procedure. This allows us to obtain a stabilized numerical solution scheme. Some particular aspects of the problem solution, such as the mesh updating procedure and the transom stern treatment, are presented. Examples of the efﬁciency of the semi-implicit algorithm for the analysis of ship hydrodynamics problems are presented.

A finite element method for fluid-structure interaction with surface waves using a finite calculus formulation

Julio García-Espinosa — Wed, 10 Apr 2019 21:26:41 +0200

A stabilized semi-implicit fractional step finite element method (FEM) for solving coupled fluid-structure interaction problems involving free surface waves is presented. The stabilized governing equations for the viscous incompressible fluid and the free surface are derived at a differential level via a finite calculus (FIC) procedure. A mesh updating technique based on solving a fictitious elastic problem on the moving mesh is described. Examples of the efficiency of the stabilized semi-implicit algorithm for the analysis of fluid-structure interaction problems in totally or partially submerged bodies is presented.

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

Julio García-Espinosa — Mon, 09 Jul 2018 12:56:02 +0200

In this work a finite element method (FEM) 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 (SLI); and the second one based on the Streamline-Upwind Petrov-Galerking (SUPG) stabilization. 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.

A time-domain finite element method for seakeeping and wave resistance problems

Borja Servan Camas — Wed, 21 Mar 2018 13:21:02 +0100

The objective of this thesis is the research on numerical algorithms to develop numerical tools to simulate seakeeping problems as well as wave resistance problems of ships and floating structures.
The first tool developed is a wave diffraction-radiation solver. It is based on the finite element method (FEM) in order to solve the Laplace equation, as well as numerical schemes based on FEM, streamline integration, and finite difference method tailored for solving the free surface boundary condition.
It has been developed numerical tools to solve solid body dynamics of multibody systems with body links across them. This tool has been integrated with the wave diffraction-radiation solver to solve wave-body interaction problems.
Also it has been tailored coupling algorithms with other numerical tools in order to solve multi-physics problems. In particular, it has been performed coupling with a MEF structural solver to solve fluid-structure interaction problems, with a mooring solver, and with a solver capable of simulating internal flows in tanks to solve couple seakeeping-sloshing problems.
Numerical simulations have been carried out to validate and verify the developed algorithms, as well as to analyze case studies in the areas of marine engineering, offshore engineering, and offshore renewable energy.

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

José Enrique Gutiérrez Romero — Wed, 22 Feb 2017 18:47:11 +0100

The complexity of the dynamic behaviour 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 time-domain model for solving the dynamics of floating marine devices, subjected to non-linear environmental loads and paying special attention on the mooring dynamics. First, the formulation of the hydrodynamic approach for solving the wave-floater interaction is introduced. Second, the solver of the mooring dynamics, based on a non-linear Finite Element Method approach, is presented. Third, a procedure for coupling the hydrodynamic along with other external loads, with the floating structure and mooring dynamics is described. Fourth, some validation examples and comparisons among different mooring approaches are presented. Fifth, an analysis of the OC3 floating wind turbine concept is performed to study the influence of different mooring models, the effects of non-linear waves on the platform, and the tension in the mooring system. The dynamic mooring model along with the second-order wave model produce realistic simulations of the floating wind turbine performance.

Time domain simulation of coupled sloshing–seakeeping problems by SPH–FEM coupling

Jonathan Colom Cobb — Wed, 22 Feb 2017 11:56:02 +0100

The aim of this work is to carry out numerical simulations in the time domain of seakeeping problems taking into account internal flow in tanks, including sloshing. To this aim, a Smooth Particle Hydrodynamics (SPH) solver for simulating internal flows in tanks is coupled in the time domain to a Finite Element Method (FEM) diffraction-radiation solver developed for seakeeping problems. Validations are carried out comparing against available experimental data. Good agreement between obtained numerical results and experimental data is found.

A computational model for the evaluation of the spray generation of a Wave Adaptive Modular Vessel

Julio García-Espinosa — Thu, 22 Dec 2016 21:04:18 +0100

This paper presents part of the work done within the project 'Advanced Numerical Simulation and Performance Evaluation of WAM-V® in Spray Generating Conditions' developed by the International Center for Numerical Methods in Engineering (CIMNE) under Navy Grant N62909-12-1-7101 issued by the Office of Naval Research Global. One of the primary goals of that project was the development of a computational model for simulation of the Wave Adaptive Modular Vessel (WAM-V®) under spray generating conditions. For this purpose, a Semi-Lagrangian Particle Finite Element Method (SL-PFEM) has been applied. This is the latest development within the framework of the so-called Particle Finite Element Method (PFEM), using the X-IVAS (eXplicit Integration along the Velocity and Acceleration Streamlines) scheme. In this paper we demonstrate the applicability of the SL-PFEM using the X-IVAS scheme for the simulation of the Wave Adaptive Modular Vehicle under spray generating conditions.

Computer Programming of free GUIs for the Analysis of the Behaviour of Marine Structures

José Enrique Gutiérrez Romero — Wed, 23 Nov 2016 15:04:06 +0100

This work presents the development of two free Graphical User Interfaces (GUI), called ''FASTLognoter'' and ''MorisonForm'', both focused on the analysis of the behaviour of offshore structures, especially of offshore wind turbines. The first one is related to the aeroelastic analysis of wind turbines, and the second is concerned with the seakeeping of marine structures. The development of these tools has been carried out using a powerful software called ''Lognoter''. This tool is free software for Knowledge Management in Technology (KMT), which integrates computer programming for allowing the development of GUIs. These GUIs give an open platform for conducting a parametric study of the structural and dynamic behaviour of marine structures. Their coupling permits the user to set a suitable way to evaluate new concepts in marine structures. Finally, an application for the intensive analysis of offshore wind turbines is shown.

A FEM fluid-structure interaction algorithm for analysis of the seal dynamics of a Surface-Effect Ship

Julio García-Espinosa — Mon, 23 May 2016 17:02:02 +0200

This paper shows the recent work of the authors in the development of a time-domain FEM model for evaluation of the seal dynamics of a surface effect ship. The fluid solver developed for this purpose, uses a potential flow approach along with a stream-line integration of the free surface. The paper focuses on the free surface-structure algorithm that has been developed to allow the simulation of the complex and highly dynamic behavior of the seals in the interface between the air cushion, and the water.

The developed fluid-structure interaction solver is based, on one side, on an implicit iteration algorithm, communicating pressure forces and displacements of the seals at memory level and, on the other side, on an innovative wetting and drying scheme able to predict the water action on the seals. The stability of the iterative scheme is improved by means of relaxation, and the convergence is accelerated using Aitken’s method.

Several validations against experimental results have been carried out to demonstrate the developed algorithm.

Development of a decision support system for optimization of the performance of sailing yachts

Scipedia content — Thu, 13 Oct 2016 16:32:53 +0200

In this paper, the conception and design of a new monitoring system for a racing yachts rig is presented. The sensors developed are able to process the measured strain data, by applying artificial neural networks (ANN) algorithms, and then evaluate the load acting on an element and identify the direction of the action of that force. This way, it is possible to identify the actual operating conditions of the yacht rig. The required data for ANN training is generated from the results obtained from different finite element method (FEM) computational models of the device. Furthermore, during the design phase of the system, different experimental campaigns were carried out. The experimental tests were designed to serve as proof of concept, as well as to validate the different procedures used in the system development and application. The developed monitoring system is wireless, low-intrusive and easily adaptable to any yacht configuration. This work also presents the integration of the monitoring system into a coupled fluid-structure computation model for the sails and rig of a boat. The resulting system is an efficient tool for evaluating performance and decision support in the adjustment of a sailboat rig.

Accelerated 3D multi-body seakeeping simulations using unstructured finite elements

Julio García-Espinosa — Thu, 11 May 2017 21:00:43 +0200

Being capable of predicting seakeeping capabilities in the time domain is of great interest for the marine and offshore industry. However, most computer programs used in the industry work in the frequency domain, with the subsequent limitation in the accuracy of their model predictions. The main objective of this work is the development of a time domain solver based on the finite element method capable of solving multi-body seakeeping problems on unstructured meshes. In order to achieve such an objective, several techniques are combined: the use of an efficient algorithm for the free surface boundary conditions, the use of deflated conjugate gradients, and the use of a graphic processing unit for speeding up the linear solver. The results obtained results by the developed model showed good agreement with analytical solutions, experimental data for an actual offshore structure model, as well as numerical solutions obtained by other numerical method. Also, a simulation with sixteen floating bodies was carried out in a affordable CPU time, showing the potential of this approach for multi-body simulation.

ODDLS: A new unstructured mesh finite element method for the analysis of free surface flow problems

María Jesús Samper — Mon, 17 Dec 2018 12:38:22 +0100

This paper introduces a new stabilized finite element method based on the finite calculus (Comput. Methods Appl. Mech. Eng. 1998; 151:233–267) and arbitrary Lagrangian–Eulerian techniques (Comput. Methods Appl. Mech. Eng. 1998; 155:235–249) for the solution to free surface problems. The main innovation of this method is the application of an overlapping domain decomposition concept in the statement of the problem. The aim is to increase the accuracy in the capture of the free surface as well as in the resolution of the governing equations in the interface between the two fluids. Free surface capturing is based on the solution to a level set equation. The Navier–Stokes equations are solved using an iterative monolithic predictor–corrector algorithm (Encyclopedia of Computational Mechanics. Wiley: New York, 2004), where the correction step is based on imposing the divergence‐free condition in the velocity field by means of the solution to a scalar equation for the pressure. Examples of application of the ODDLS formulation (for overlapping domain decomposition level set) to the analysis of different free surface flow problems are presented. Copyright © 2008 John Wiley & Sons, Ltd.

CFD analysis of the roll movement of a container ship

María Jesús Samper — Wed, 20 Nov 2019 14:38:58 +0100

In the present work a novel approach has been developed for the resolution of this problem of analysis of the movement of roll of a ship. The methodology used for this is based on the modification of the differential equations of the fluid dynamics (RANSE equations), including the movement of the free surface, by applying the finite calculus method. The modified equations are solved using an implicit predictor-corrector scheme and the finite element method (FEM). This resolution scheme is considered optimal for these types of problems, both in accuracy and in calculation time. As an example, it should be noted that for typical problems (more than 1,000,000 finite elements) less than 4 hours of CPU are required to solve several cycles of ship movement (Pentium IV). This allows the analysis of an array of tests in a few days or even hours, having a computer network or sufficient computing power.