Page 47: of Offshore Engineer Magazine (May/Jun 2026)

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propulsion systems. Its position-holding capabilities were examined under extreme weather conditions: high winds, strong currents and effective wave heights of 2.5m and 3.2.

The results of the extensive simulations at DNV showed a signifcantly improved positioning accuracy thus reducing the overall DP footprint. This permits successful gangway landing operations even in rougher conditions, thus in- creasing the operational window of the vessel throughout the year. Furthermore, the implemented optimizations are expected to result in additional fuel savings: Thanks to the faster response time of the propulsion, the vessel can be

SRP-D with a quickly held in position with only minor corrections being propeller shaf necessary. This prevents major corrections in position hav- with an eight- ing to be made which would require more power. degree tilt.

98-Degree Tilted Propeller Shaf

Another independent study focused particularly on pro- pulsion effciency during thruster interactions. The research was carried out on a model of a CSOV equipped with a

Schottel SRP-D 98-degree thruster on starboard and a regu- lar 90-degree thruster on portside. The frst part of the study measured the interactions between propulsion unit and hull. It was found that the additional eight-degree down- ward tilt of the SRP-D propeller shaft could signifcantly reduce thrust losses, both for azimuth variations and thrust variations. For example, CSOVs with 98-degree thrusters experience only 10 percent thrust losses in transverse direc- tion, compared to 35 percent with 90-degree thrusters. The study showed that a key factor for the improved system per- formance is a reduced Coanda effect with the SRP-D. The second part of the research focused on propeller fow inter- actions. In this case, the additional eight-degree downward tilt is also benefcial: While 50 percent losses are observed when the 90-degree thruster is blowing the wake into the second thruster (in-line thrust losses), only 20 percent thrust losses occur with the 98-degree thruster, which therefore en- abled a higher remaining force during DP.

Thorsten Tillack, head of hydrodynamics and propeller design at Schottel, summarizes the resulting advantages: “Overall, the SRP-D signifcantly optimizes thrust yield and thrust distribution, since thruster-hull- and thruster- thruster-interactions are minimized. Consequently, the forbidden zones of the thrusters may be reduced, which leads to an additional increase of the DP performance for the vessel. Furthermore, the optimized thrust output is

Te 98-degree variant induced lower losses at the other expected to result in fuel savings. As a result, SOVs oper- ate much more effciently, extending their operating time thruster than the 90-degree variant and therefore enabled a higher remaining force during DP.

throughout the year.”

MAY/JUNE 2026 OFFSHORE ENGINEER 47