Abstract

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.

Abstract

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.

Abstract

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.

Abstract

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 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, bichromatic, and irregular waves. Good agreement has been found for both, body movements and mooring forces.

Abstract

There is no question about the relevancy of the blue growth concept, as a long term strategy to support sustainable growth in the marine sector. One of the sectors that has a higher potential for sustainable growth in this field is the aquaculture. This work is focused on the development of a time domain hydrodynamic solver for analysis and assessment of floating fishing farms. The paper also presents a demonstration case based on typical configuration of fishing farms used in the Mediterranean Sea. It is composed by a set of individual circular fishing cages. Several arrangements of fishing cages are also analysed subject to wind waves and currents. Different fishing cages are used in the performed simulations: circular, square and hexagonal.

The influence of several configurations on fishing farm mooring behaviour in different sea states is studied. The analysis is focused in the dynamic behaviour of fishing cages. In particular mean drift and slow drift motions, including the second order-effects, will be studied, since they have important role on the behaviour of fishing farm in seaway. The results lead to final discussion about the best performance in fishing farm layout.

Abstract

The aim of this work is to be able to cope with complex sloshing-seakeeping problems in an effective manner. For this purpose, two different solvers will be integrated into one coupled tool to take advantage of their characteristics.

The Particle Finite Element Method is a versatile framework for the analysis of fluid-structure interaction problems. 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. This new scheme was named PFEM-2 and will be used in this work to solve the fluid dynamics (sloshing) inside the tanks.

The PFEM-2 will be coupled in the time domain with SeaFEM, a solver developed for seakeeping problems. SeaFEM solves the second-order diffraction-radiation equations by using the Finite Element Method (FEM) and will be used in this work to simulate the interaction between waves and a floating body.

The coupling of the two tools will be accomplished by using an effective coupling algorithm and a communication technique that allows simulations to be computed without affecting the global compute time and the accuracy of the solvers. This new tool has been validated against experimental benchmarks carried out in a model basin at model scale.

Abstract

A Wave Adaptive Modular Vessel (WAM-V®) is a new class of ship that uses inflatable flexible hulls to conform to the surface of the water. It is similar in design to a catamaran, in that it has a twin hull design and no keel. However, the superstructure is not rigidly attached to the hulls; it uses shock absorbers and ball joints to articulate the vessel, which allows WAM-V to conform to the surface of the water while mitigating the stresses transmitted to the structure. Moreover, the inflatable hulls help to absorb the high frequency wave-loads. These features allow WAM-V to travel efficiently with low wave resistance in rough seas, by surfing on top of the waves rather than cut through them.

The objective of the WAM-V is to be a lightweight watercraft capable of moving fast and efficiently on the surface of the sea. WAM-Vs are designed to allow for a variety of applications for either manned or unmanned operations and can be built in different lengths to match specific services.

This presentation shows part of the work done in 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. The scope of that project included the performance analysis of the WAM-V in waves, taking into account the flexibility of the ship hulls, using fluid-structure interaction computational models. However, the focus of this paper is one of the primary concerns of that project; the development of a computational model for simulation of the WAM-V under spray generating conditions. In this regards, the final goal was to develop and demonstrate a computational engineering solver that could be used to design strategies to reduce the spray generation of the vessel.

Abstract

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.