CFD Modelling coupled with Floating Structures and Mooring Dynamics for Offshore Renewable Energy Devices using the Proteus Simulation Toolkit

This is the author accepted manuscript. The final version is available from EWTEC via the link in this record.In this work, the coupling of novel opensource tools for simulating two-phase incompressible flow problems with fluid-structure interaction and mooring dynamics is presented. The open-source Computational Fluid Dynamics (CFD) toolkit Proteus is used for the simulations. Proteus solves the twophase Navier-Stokes equations using the Finite Element Method (FEM) and is fully coupled with an Arbitrary Lagrangian-Eulerian (ALE) formulation for mesh motion allowing solid body motion within the fluid domain. The multi-body dynamics solver, Chrono, is used for calculating rigid body motion and modelling dynamics of complex mooring systems. At each time step, Proteus computes the forces from the fluid acting on the rigid body necessary to find its displacement with Chrono which will be used as boundary conditions for mesh motion. Several verification and validation cases are presented here in order to prove the successful coupling between the two toolkits aforementioned. These test cases include wave sloshing in a tank, floating body dynamics under free and wave-induced motion for different degrees of freedom (DOFs), and mooring dynamics using beam element theory coupled with rigid body dynamics and collision detection. The successful validation of each component shows the potential of the coupled methodology to be used for assisting the design of offshore renewable energy devices.Support for this work was given by the Engineer Research and Development Center (ERDC) and HR Wallingford through the collaboration agreement (Contract No. W911NF-15-2-0110). The authors also acknowledge support for the IDCORE program from the Energy Technologies Institute and the Research Councils Energy Programme (grant number EP/J500847/)

Model test of the DTI-Floating wind concept

This study aims to de-risk the development of the Deep Turbine Installation-Floating (DTI-F) concept, a hybrid spar buoy-based floating offshore wind turbine with the novelty of being able to raise up and lower down the tower plus nacelle set. The paper presents the design and construction of a Froude-scaled model based on the DTI-F concept, the experimental testing configurations and conditions, and the instrumentation used to measure motions and loads. The test campaign included free decay and stiffness decay tests, along with regular and irregular wave testing. In addition to the hydrodynamic characterisation, the resonance properties of the system with different mooring configurations, i.e. three and four lines, and three lines with a delta connection, were investigated. We present the Response Amplitude Operators (RAOs) in all 6 degrees of freedom for two different mooring configurations. This work is the first step towards the calibration and performance improvement for existing numerical models of the DTI-F concept

Approach an autonomous vessel as a single robot with Robot Operating System in virtual environment

This project aims at developing an efficient simulation environment for the vessel navigation system. The design of the overall navigation system is described along with its application for the case study of an autonomous vessel. The UNITY and Robot Operating System were utilised as the virtual environment and the main control framework, respectively. By treating the autonomous vessel as a single robot, each part of the system was formulated to enhance the efficiency and visualisation in the development progresses for autonomous system. The virtual environment using UNITY overwhelms the space-time constraints in the testing stage. The navigation system combined with conventional navigation algorithms and a computer vision algorithm were implemented in the Robot Operating System. Hence, the navigation system was enhanced by an assistant object detection algorithm to be more active on fusing environment information. The excellence of the proposed object detection model was demonstrated with reliable performance with 94% mean Average Precision, which renders the model exhibiting visual sensibility in navigation. Overall, it is believed that this study can contribute to offering some insights into developing autonomous marine vessels

Transport telematic architecture of an electronic payment system for traditional merchant shipping

Wooden boats operating throughout an archipelagic country play an important role in connecting in particular remote areas and small islands. Those boats are deployed by traditional merchant shipping, also known as Pelra, abbreviated from Pelayaran Rakyat meaning Pelople's Shipping. They carry nearly all types of cargoes, and usually a family business. Efforts to alleviate its role are necessary, from various aspects. The duration of shipments of cargo by using Pelra ships is long, the impacts on the cashflow of many parties are immediately afected. The growth of internet usage open a window of opportunity to improve this situation, by introducing e-Payment system. This paper outlines this effort by applying the Intelligent Transpotation System (ITS) architecture. A Pelra route Surabaya-Bima serves a case study to investigate the viability of the e-payment. The study concludes that introduction of an e-payment system is promising

Code comparison of a NREL-FAST model of the Levenmouth wind turbine with the GH bladed commissioning results

This is the author accepted manuscript. The final version is available from ASME via the DOI in this record.This paper describes the process adopted to set up a FAST model to produce relevant design load cases (DLCs) for the Levenmouth (Samsung Heavy Industries - S7.0-171) demonstration foreshore wind turbine owned by the Offshore Renewable Energy Catapult (ORE Catapult). The paper does not take into account hydrodynamic forces. Existing literature has carried out FAST studies predominantly using reference turbines (e.g. NREL-5MW, DTU-10MW) instead of real prototype or commercial turbines. This paper presents the results for the Levenmouth wind turbine, a real, operating demonstration wind turbine. The paper explores and simulates the critical loads for the turbine, which will be very valuable validation case for industrial and academic use. Moreover, the Levenmouth wind turbine exhibits a new generation of extremely flexible blades that conflict with the previous approaches used by most common aero-elastic codes and makes this simulation a challenge. The study is divided into three steps. It starts with building the model and fine-tuning it until it matches the natural frequencies of the blades and tower. The second step encompasses the comparison of the commissioning results with the relevant NREL FAST simulations to match the dynamic behaviour of the turbine. The final step comprises a load comparison for the interface between the tower and transition piece, in order to validate the new aero-elastic model with the commissioning loads.This work is funded in part by Floating Wind Turbines Limited (FWT Ltd), and the Energy Technologies Institute (ETI); Research Councils UK (RCUK); Energy Programme for the Industrial Doctorate Centre for Offshore Renewable Energy (IDCORE) [grant number EP/J500847/1]

Baseline Design of the Deep Turbine Installation-Floating, a New Floating Wind Concept

This is the author accepted manuscript. The final version is available from ASME via the DOI in this recordThis paper presents the preliminary design of the Deep Turbine Installation-Floating (DTI-F) concept. The DTI-F concept is a hybrid spar buoy-based floating offshore substructure capable of supporting a 7MW wind turbine with the uniqueness of being able to raise and lower the tower and nacelle, which simplifies construction, installation, maintenance, and decommissioning. A relevant subset of design load cases (DLCs) derived from the International Electrotechnical Commission (ICE) standards is simulated with NREL-FAST software, and the aero-elastic loads are used for the structural assessment. The paper presents the principal dimensions and crucial hydrostatic and hydrodynamic properties. The floating platform with three different mooring configurations is designed using ANSYS AQWA software, and the design is validated with experiments in laboratory conditions. The paper evaluates the design regarding the natural frequencies and the stability of the platform for a chosen site off the Scottish coast. Further, a novel construction method, the materials chosen for the construction, and the installation and assembly processes are also outlined.Floating Wind Turbines Limited (FWT Ltd)Energy Technologies Institute (ETI)Engineering and Physical Sciences Research Council (EPSRC

CFD Modelling coupled with Floating Structures and Mooring Dynamics for Offshore Renewable Energy Devices using the Proteus Simulation Toolkit

With many countries showing a growing interest in offshore renewables, the development of floating support structures able to withstand extreme environmental loads is key to winning the race in offshore renewable energy deployment. Numerical modelling of these structures allows relatively inexpensive testing and selection of suitable designs. The research presented here focuses on the numerical analysis of the behaviour of different floating structure designs and the associated mooring dynamics under various wave conditions. Simulations are performed with Proteus, a relatively new and open-source computational fluid dynamics (CFD) software actively developed by the ERDC and HR Wallingford, using the Finite Element Method (FEM) to model two phase flows. In order to allow the simulation of moving bodies in Proteus, a mesh motion module has been developed. The mesh nodes in the fluid domain are moved using the equations of linear elastostatics while displacement of the nodes placed on the surface of the moving structure is imposed through boundary conditions (see Figure 1 for an illustrative example of the mesh motion for an oscillating floating body). The mesh motion is taken into account directly in the Navier-Stokes equation that are solved in the Eulerian frame. Using input forces and moments from the CFD solver, floating body and mooring dynamics are solved using the open source C++ library Project Chrono. This library allows a fully coupled simulation of rigid and flexible bodies with cable dynamics using FEM, where collision detection of the cables with structures is enabled using node clouds for seabed and other obstacles. Verification and validation of the coupled two-phase flow and body/moorings dynamics is conducted in this paper with the help of experimental data of floating bodies with varying constrains and degrees of freedom. Figure 2 shows results of one of the validation tests where the Response Amplitude Operator (RAO) was obtained with Proteus for the roll motion of a floating body under different wave loads and compared to experimental data [1] and to other numerical models [2]. Validating the model for these cases allows us to simulate with confidence more representational scenarios for offshore renewable energy devices using, for example, a selection of the following floating wind support structures: deep draught platforms (SPAR), tension-leg platforms (taut mooring), and semi-submersible (buoyancy stabilized)