Research

Title:	KonRo – Design and Optimization Tool for a CRP Propulsion Concept
Term:	2024 – 2026
Project manager:	Katrin Hellwig-Rieck
Funding:	Bundesministerium für Wirtschaft und Klimaschutz
Project administration:	EuroNorm GmbH
Reg.-No.:	49MF23104

Not only the energy savings but also improved maneuverability and, depending on the propulsion concept, a potential increase in safety compared to single propellers — due to the redundancy provided in case of a propeller failure — make the CRP an attractive option for main propulsion systems. The arrangement of the TWIN-CRP at the aft ship is identical to that of a single propeller. The application of CRP systems is primarily seen in specialized vessels, such as fishing vessels, research ships, and supply vessels.

Through its R&D project, the SVA aims to develop a reliable approach for the design and optimization of contra-rotating propellers with a dual-shaft system and minimal spacing between the two propellers. Based on CFD simulations, which will be validated through laboratory experiments during the project, the accuracy of performance predictions for ships equipped with the above-described CRP propulsion system is to be improved. To achieve this, the accuracy of numerical methods must be further improved for both design and off-design conditions. In the past, significant deviations were observed between measured and calculated open-water coefficients, particularly under high propeller loads and extremely small distances between the blades of the forward and aft propellers.

Since TWIN-CRP systems are still relatively new to the market, data collection and the associated insights into the behavior of TWIN-CRP systems under both design and off-design conditions are crucial. This will help evaluate the advantages and disadvantages of TWIN-CRP compared to a single propeller in ship operation. Initial studies on the behavior of a ship equipped with TWIN-CRP systems and independently controllable propellers during acceleration, braking, and stopping will lay the groundwork for further research.

With the concentric shafts, the shaft bearings represent one of the biggest mechanical challenges in TWIN-CRP systems. Particularly during maneuvering, significant forces may act on the bearings. Therefore, in the first step, the transverse forces (bearing forces) of the entire system under selected operating conditions will be determined through both model testing and numerical analysis.

Title:	BREWEL – Simulation of Ships with Breaking Waves
Term:	2023 – 2026
Project manager:	Lars Lübke
Funding:	Federal Ministry for Economic Affairs and Climate Action
Project administration:	EuroNorm GmbH
Reg.-No.:	49MF230052

The final performance forecast is made after the contract is signed, based on measurements. If the forecast uncertainty of the numerical methods exceeds the considered power reserves, costly measures or penalty clauses are hard to avoid. Therefore, a high level of forecast accuracy is crucial for competitiveness and must be guaranteed to the highest possible extent. For ships with breaking waves, larger discrepancies occur between the calculation results and the measured resistance values. The calculated power values can deviate from the measured values by up to 20%. These values are far outside the usual safety margins and expected ranges. Simulations conducted on other facilities have shown similar deviations. The calculations were performed using different RANSE solvers (Reynolds-averaged Navier-Stokes Equations) and company-specific settings, so a general error in the calculation methods can be assumed. Further investigations have shown that, for example, the trim position can be ruled out as a source of error. The cause of the error is considered to be the wave system with the breaking bow wave. It is assumed that the breaking bow wave is not correctly captured in the simulations, and as a result, the wave interferences between the bow and stern wave systems are also affected. As part of the research topic, the prognosis accuracy for ships with breaking waves is to be improved and integrated into the procedural guidelines of SVA Potsdam. To achieve this, resistance, wave patterns, and wake fields for different ships will be measured and made available for the validation of simulations. The focus of the numerical simulations will be on the necessary grid resolution, the inclusion of surface tension in the simulations, and the identification of differences between homogeneous and heterogeneous multiphase models. The calculations will be conducted using different RANSE solvers and meshing strategies.

Title:	ActiveRudder – Innovative Propulsion and Manoeuvering System
Term:	2023 – 2025
Project manager:	Rhena Klose
Funding:	Federal Ministry for Economic Affairs and Climate Action
Project administration:	EuroNorm GmbH
Reg.-No.:	49MF220139

The outlined boundary conditions highlight the necessity for the maritime industry to develop solutions for the anticipated retrofitting of existing fleets and the construction of new vessels. One solution is to develop an auxiliary propulsion system for ships that relies exclusively on alternative green energy sources, such as hydrogen-powered fuel cells, and is suitable for both retrofitting and new builds. This could involve installing a self-contained electric sub-network with onboard fuel cell(s) to power an active rudder. The propulsion capacity of the active rudder should be sufficient for ships to navigate canals, enter ports, and manoeuver there using this system alone, without relying on the main diesel engine. The energy source should also be designed to supply the ship’s onboard power network during these phases, allowing the diesel generators to be turned off as well. This would ensure that all CO2 emitters and low-frequency noise sources are deactivated, addressing not only exhaust emissions but also underwater noise, which is a growing focus of the IMO (International Maritime Organization). The active rudder is intended not only to significantly improve the ship’s maneuverability but also to provide redundancy in propulsion and steering through the independence of the energy source, thereby enhancing safety and functionality. During transit, the auxiliary propulsion system can be used as a booster, allowing the main diesel engine’s output to be reduced by this amount of power without compromising service speed. As part of the research topic, SVA contributes to this development with its expertise in fluid dynamics design of propulsion systems and their testing at the model scale. This contribution includes detailed investigations of flow patterns and noise generation. In addition to the fluid dynamic design of the auxiliary propulsion system, which consists of a rudder, active rudder propeller, and nozzle for various types of ships, the focus is on the hydrodynamic and hydroacoustic optimization of the entire system, which includes both the main propulsion and the active rudder. The system will be tested through extensive model trials (free-running, propulsion, maneuvering, cavitation tests, and acoustic measurements).

Title:	Impact of Skeg Alternatives on Resistance and Yaw Stability
Term:	2022 – 2025
Project Manager:	Erik Schomburg
Funding:	Federal Ministry for Economic Affairs and Climate Action
Project administration:	EuroNorm GmbH
Reg.-No.:	49MF220037

In this R&D topic, the aim is to demonstrate the impact of skeg alternatives, such as fixed fins and/or enlarged rudder areas, on resistance, power requirements, as well as rolling behavior and course stability. Power savings, particularly in alternative power supply systems such as batteries or fuel cells, lead to significant weight, space, and cost reductions due to the scalable nature of storage systems. Since the proposed alternatives are not expected to involve significantly higher construction effort but may result in cumulative weight and resistance effects, resistance-reducing measures are generally of great interest to shipyards and ship operators, especially in the context of rising fuel prices.

The project aims to develop replacement systems for skegs that provide the same yaw stability while reducing ship resistance. The development of these alternatives will be carried out using numerical flow simulations. Model tests will provide insights into power requirements, rolling behavior, and maneuvering characteristics with the replacement systems. The development will focus on two different types of twin-screw vessels, as these are considered to have the highest application potential. The fundamental assumption is that a fully submerged fin can generate greater lift for the same surface area compared to a hull-integrated skeg. This hypothesis will be tested within the scope of this research topic.