General Goal:

The size and capacity of ships in general, and more specifically the size and capacity of container ships, increased dramatically over the last decades, leading to a higher air draft and much bigger impact of wind and wind loads. These wind effects on ships are traditionally assessed using very simplified semi-empirical methods, which can presently fall short due to both the increase in the ship’s dimensions and the augmented probability of harsh meteorological events.

The goal of the project is to investigate in detail the effects of wind on modern container ships moored in realistic, densely built harbour environments. The problem will be tackled by means of wind tunnel tests, CFD simulations and dynamic mooring analysis.

The end results of the project will be:

• a better understanding of the impact of the wind in a harbour environment;
• the development of high-fidelity models for the wind field;
• an improved technique to calculate the wind-induced forces on the moored ship and the loads on the mooring equipment.

Concrete objectives and criteria

The starting point of the EVERBLUE project will be the state-of-the-art knowledge concerning two main topics: the complex wind flow in a densely built harbour environment and the effects of wind on a moored container ship with different container stacking configurations. Based on this knowledge, the project will set up wind tunnel tests, performed in the biggest low speed wind tunnel of VKI, to investigate the wind flow in a highly built harbour and the effects of wind on a stationary container vessel.

The aim of this first phase is to run more than 200 different wind tunnel tests to acquire accurate and reliable experimental data to be used as a benchmark for the following phases and for future projects. The experimental test program will be based on a single container vessel, representative of the modern so-called Ultra Large Container Vessels (ULCS), and will include three different container stacking configurations. Three compositions of the surroundings will also be tested; a bare terminal, a terminal with container stacks and a terminal with storage tanks. For each case, five different wind speeds and a wide range of wind directions will be tested. For a selection of setups, PIV-measurements (Particle Image Velocimetry) will be carried out showing the velocity details in a 2D plane.

In the second phase, numerical simulations will be performed by means of Computational Fluid Dynamics (CFD) simulations. At first, the test cases explored in the previous (experimental) phase will be simulated, and the numerical simulation results will be validated with the experimental wind tunnel data. When the setup of the CFD simulations is validated, more numerical calculations will be performed for additional configurations which were not tested experimentally. CFD simulations will therefore expand the number of test cases, typically 5 to 10 extra cases will be selected, beyond investigated situations in the wind tunnel, and advanced techniques based on machine learning will be used to derive a reduced order model. The data of interest are mainly the wind forces and moments acting on the moored vessel, but also the precious additional insight concerning the flow pattern of wind around the harbour structures (tanks and container stacks) and the stacked containers on the vessel, as provided by CFD simulations.

Finally, in a third phase, the creation of the unique database from wind tunnel testing and CFD will be applied as input for Dynamic Mooring Analysis (DMA) simulations, for which MTD has an in-house developed state-of-the-art code. DMA simulations will assess the impact of different wind conditions on the complex dynamic system which includes the moored ship, mooring equipment and the specific terminal structure and mooring configuration. The final objective of this phase is the development of guidelines and recommendations to improve the efficiency and safety of mooring of ULCS and other ships with high air drafts.