2) The EU Optiwise project was also highlighted in MARIN’s Report magazine 139 and published at the RINA Wind Propulsion Conference by Eggers and Kisjes.

1) https://www.offshore-energy.biz/wind-ship-propulsion-in-maritime-2024-was-a-year-to-remember/

Under the effect of ship speed and waves, the position and inclination of the model varies over time, therefore the winch actuation needed to be controlled by a real-time simulation in the loop using MARIN’s time domain software aNySim-XMF.

Roll motion reduction

The seakeeping tests were conducted in various wave conditions between sea state 5 and sea state 6. With a keen focus on safety and dynamic stability, the effect of wind propulsion on the ship’s seakeeping ability was obtained by repeating some of the conditions with the winch system either enabled or disabled. Such comparisons led to the interesting observation that in waves from the
stern-quarter, the wind propulsion reduces the roll motion and associated transverse accelerations significantly.

Similarly to the seakeeping tests, many manoeuvring tests were conducted with the winch system either enabled or disabled, and for multiple wind speeds from different directions. The measurements showed that the ship may experience a bigger speed loss in a turn, because the total resulting force of the rotors can at some time, increase the ship resistance, leading to a lower speed. The complete manoeuvring campaign led to a better understanding of what effect these rotor sails have on the ship during operations.

The towing tests in calm water were carried out to measure the hydrodynamic forces and propulsive characteristics of the vessel in a wind-assisted configuration. When deploying wind propulsion, the vessel will not sail straight ahead but at a drift angle, and it will also show some heel. Therefore, the measurements were conducted with the model set under fixed combinations of drift angle and heel.

Because of the large model size and the necessity to measure side forces, the usual towing setup was replaced by another one, which provided two connection points to the model. At each connection point the forces were measured, and some motions were allowed to obtain free model trim and sinkage. Comparing the forces and moments measured in the different combinations enabled MARIN to quantify the effect of drift or heel on the ship’s resistance and propulsive efficiency, among other things. Additionally, the measured forces, propeller rotation rates, thrust and torque were extrapolated to full scale so that they could be used later as input for a Velocity Prediction Programme, together with the predicted thrust from the rotors.

Rotor sails simulations

The first step quantified the forces and moments generated by the six Norsepower rotor sails in their intended arrangement on the ship. Simulations using MARIN’s RANS-CFD code ReFRESCO were conducted using a numerical model of the vessel, including the superstructure and the six rotors set under various combinations of wind speed and wind angles. By including all aspects of the ship’s geometry, the interactions between the different rotors and between the rotors, the hull and the superstructure, could be determined. The result of the simulations was further used by Deltamarin and Norsepower to refine their design, and as input for the seakeeping and manoeuvring model tests.

The µMMS is not only applicable for FOWT, but also for other small floaters and ships. The new measurement system makes it possible to accurately test small vessels, without the unwanted effect of the measurement cables.

For example, this year the Dutch Ministry of Infrastructure and Water Management contracted MARIN to investigate the dynamics that are involved in the capsizing of beam trawlers. The main goal of this project was to investigate the capsize risk in relation to fishing operations and the stability criteria.

Initially, we had planned to make a free sailing model for the tests that connects to the measurement system on the carriage. The combination of a small vessel and the high wave height in the tests resulted in a model weight of less than 100 kg. Given the small model size, low forces can have an impact on the rolling behaviour of the vessel. Therefore, to minimise the impact that the cables can have on the motions of the vessel, we minimised the number of sensors on board to the bare minimum. Additionally, we planned to use thinner cables than normal to reduce the weight even further.

The µMMS became available when we were designing the model. This offered the opportunity to make the model completely wireless and to measure more signals within the budget of the project. Without the measurement wires between the carriage and the model, the test setup was more versatile. No precautions were necessary to avoid interference from the measurement cables.

Extensive model test campaign

An extensive model test campaign started shortly afterwards. Besides the usual tests in fully motorised conditions (i.e. without the contribution of wind propulsion), a large number of towing, seakeeping and manoeuvring tests were performed in which the effect of wind propulsion was included.

MARIN was therefore delighted to contribute once more to ship decarbonisation when the Finnish ship design company Deltamarin contracted MARIN to conduct calculations and model tests to investigate the propulsive performance, seakeeping and manoeuvring capability of a wind-assisted RoRo design. This vessel is set to be delivered to Louis Dreyfus Armateurs and will transport airplane parts between Europe and North America.