A Tension Leg Platform supporting a wind turbine was tested in combined waves, wind and current in the Offshore Basin of MARIN. The wind turbine loads were simulated in two ways for these tests. Firstly, the wind turbine was modelled by a physical wind turbine following the approach of performance scaling. This approach intends to scale down the wind, the wind turbine inertia, the rotation speed of the rotor according to Froude’s scaling laws while it keeps the thrust that is representative of the considered wind turbine. The Marin Stock Wind Turbine (MSWT) was used in these tests. Secondly, the wind turbine was replaced by a system actuating the wind turbine loads in which the aerodynamic loads are calculated by a numerical code and applied through a system of winches to a frame mounted on the floater. Lift and drag coefficients of the blades of the MSWT were used by the computer program during these tests. The TLP was tested with both techniques for the same environmental conditions. Tests were done in waves, wind and current with the two techniques in the same basin, enabling an objective comparison of these two methods. The experimental results of both methods are analyzed and compared to each other in this study.

No abstract

Breaking waves have been studied for many decades and are still of interest as these waves contribute significantly to the dynamics and loading of offshore structures. In current MARIN research this awareness has led to the setup of an experiment to determine the kinematics of breaking waves using Particle Image Velocimetry (PIV). The purpose of the measurement campaign is to determine the evolution of the kinematics of breaking focussed waves. In addition to the PIV measurements in waves, small scale wave-in-deck impact load measurements on a fixed deck box were carried out in the same wave conditions. To investigate the link between wave kinematics and wave-in-deck impact loads, simplified loading models for estimating horizontal deck impact loads were applied and compared to the measured impact loads. In this paper, the comparison of the model test data to estimated loads is presented.

Breaking waves have been a popular research area among scientists and engineers since they present a strongly nonlinear and turbulent phenomenon. When these waves encounter an offshore or coastal structure, they exert significant amount of loads and stresses, which may result in a catastrophic consequence. Therefore, it is of utmost importance to study breaking waves and associated phenomena. Inspired by this need, in a recent MARIN experiment kinematics of breaking waves were measured with Particle Image Velocimetry (PIV). Among different types of breaking waves, spilling breakers were selected in this initial campaign. First, a summary of the measurement results will be given. These results will then be used for validation of a Computational Fluid Dynamics (CFD) tool. In numerical simulations two methods were followed in order to reproduce the focused wave: in the first method, the CFD tool was coupled to a nonlinear wave model, and in the second method an iterative scheme was used with the CFD tool. Results from these methods were then compared with the measurements.

In this paper, the operability of an Offshore Service Vessel (OSV) is looked into for different heading orientations of the vessel. Traditionally, the OSV heading orientation has been into the predominant current direction to prevent large beam current forces and thruster utility. However, such an orientation can lead to unfavourable wave headings which can cause large first order motions making it difficult to operate the gangway on board the vessel. Hydrodynamic time domain simulations were run for 1-year of hindcast weather data from an operational wind farm site in the Netherlands for different OSV heading orientations. The results of the simulations can be used to optimize the OSV heading strategy and increase uptime, reduce waiting time and energy loss associated to this waiting time.