Numerical assessment of propeller-hull interaction and propeller hub effects for a twin screw vessel

A numerical study that addresses twin screw propulsion was conducted and results using the RANS solvers ‘FreSCo+’ and ‘Fluent’ were shared. In order to avoid potential problems on property rights we combined the DTMB (David Taylor Model Basin) model No. 5415 and the SVA (Potsdam Model Basin) propeller No. CPP 1304. The computational self-propulsion point was identified via a numerical implementation of the so-called ‘British Method’. In this particular case, linked to the hub dimensions of the chosen propeller, the detailed modelling of the propeller hub and the true resolution of its connection to the hull was rather important. The same view holds for the propeller open water test setup. For the latter case we learned that the comparison with uncorrected experimental thrust data could represent a better way to confirm the numerical results

Numerical investigation of the resistance of a zero‐emission full‐scale fast catamaran in shallow water

This paper numerically investigates the resistance at full-scale of a zero-emission, highspeed catamaran in both deep and shallow water, with the Froude number ranging from 0.2 to 0.8. The numerical methods are validated by two means: (a) Comparison with available model tests; (b) a blind validation using two different flow solvers. The resistance, sinkage, and trim of the catamaran, as well as the wave pattern, longitudinal wave cuts and crossflow fields, are examined. The total resistance curve in deep water shows a continuous increase with the Froude number, while in shallow water, a hump is witnessed near the critical speed. This difference is mainly caused by the pressure component of total resistance, which is significantly affected by the interaction between the wave systems created by the demihulls. The pressure resistance in deep water is maximised at a Froude number around 0.58, whereas the peak in shallow water is achieved near the critical speed (Froude number ≈ 0.3). Insight into the underlying physics is obtained by analysing the wave creation between the demihulls. Profoundly different wave patterns within the inner region are observed in deep and shallow water. Specifically, in deep water, both crests and troughs are generated and moved astern as the increase of the Froude number. The maximum pressure resistance is accomplished when the secondary trough is created at the stern, leading to the largest trim angle. In contrast, the catamaran generates a critical wave normal to the advance direction in shallow water, which significantly elevates the bow and creates the highest trim angle, as well as pressure resistance. Moreover, significant wave elevations are observed between the demihulls at supercritical speeds in shallow water, which may affect the decision for the location of the wet deck

TrAM - Transport : advanced and modular

Europe has taken a leading role in the international effort for a drastic reduction of greenhouse gas (GHG) emissions. Transport systems play a crucial role in this effort and the competition among the various transportation modes for the shrinkage of their environmental footprint, is mounting. Maintaining its focus on sustainability, Europe is seeking to produce transport solutions with a cost effective and environmentally friendly life cycle, integrated in its smart cities. This is what the H2020 funded project "TrAM-Transport: Advanced and Modular" aims to offer (https://tramproject.eu/). It is validating a concept for waterborne transport by implementing state-of-the-art "Industry 4.0" holistic ship design and production methods, for fully electrical vessels, operating at reasonably high speed in the vicinity of urban areas. The project will lead to significant lower construction costs and reduction in engineering hours for new zero emission fast vessels. Three different catamarans will be designed by implementing the developed methods, while one of them will be undergoing detailed design and physical model testing, prior to its construction and start of operation in Stavanger/Norway before the end of the TrAM project in 2022. The paper outlines the objectives, first R&D outcomes and the main challenges of the project

Medstraum : design and operation of the first zero-emission fast catamaran

The paper deals with the design, construction and the early operation of the worldwide 1 st battery driven high-speed catamaran passenger ferry MS Medstraum. The paper elaborates on unique issues of the design process, on the superior hydrodynamic performance, on the modular construction of vessel and on the land-based electrical/charging installation. MS Medstraum was built by Fjellstrand AS and was launched in early June 2022. After successful sea trials that superseded the expectations of designers, builders and operators, achieving a maximum speed of over 27 knots, it started operations in the Stavanger/Norway area in late September 2022. The prototype character of MS Medstraum led to its selection as “Ship of the Year 2022” at the major international maritime exhibition SMM 2022 (September 2022, Hamburg). The presented research is in the frame of the H2020 funded project “TrAM – Transport: Advanced and Modular” (www.tramproject.eu)

Ship-scale CFD benchmark study of a pre-swirl duct on KVLCC2

Installing an energy saving device such as a pre-swirl duct (PSD) is a major investment for a ship owner and prior to an order a reliable prediction of the energy savings is required. Currently there is no standard for how such a prediction is to be carried out, possible alternatives are both model-scale tests in towing tanks with associated scaling procedures, as well as methods based on computational fluid dynamics (CFD). This paper summarizes a CFD benchmark study comparing industrial state-of-the-art ship-scale CFD predictions of the power reduction through installation of a PSD, where the objective was to both obtain an indication on the reliability in this kind of prediction and to gain insight into how the computational procedure affects the results. It is a blind study, the KVLCC2, which the PSD is mounted on, has never been built and hence there is no ship-scale data available. The 10 participants conducted in total 22 different predictions of the power reduction with respect to a baseline case without PSD. The predicted power reductions are both positive and negative, on average 0.4%, with a standard deviation of 1.6%-units, when not considering two predictions based on model-scale CFD and two outliers associated with large uncertainties in the results. Among the variations present in computational procedure, two were found to significantly influence the predictions. First, a geometrically resolved propeller model applying sliding mesh interfaces is in average predicting a higher power reduction with the PSD compared to simplified propeller models. The second factor with notable influence on the power reduction prediction is the wake field prediction, which, besides numerical configuration, is affected by how hull roughness is considered

Berechnungsverfahren für das Seegangs- und Manövrierverhalten von Schiffen nach der RANSE Methode

Es wird ein Berechnungsverfahren fuer das Seegangs- und Manoevrierverhalten von Schiffen dargestellt. Das Verfahren beruht auf einer gekoppelten interativen Loesung der Bewegungsgleichung mit sechs Freiheitsgraden eines Koerpers mit RANSE, welche die turbulente Stroemung beschreibt. Die Ergebnisse zeigen eine gute Uebereinstimmung mit experimentellen Versuchen.In this work, a computation procedure for the prediction of motion of rigid bodies floating in viscous fluids and subjected to currents and waves is presented. The procedure is based on a coupled iterative solution of the 6-DOF rigid body motion equation and the RANSE, describing the turbulent fluid flow. The method is extented to more complex ship maneuvering applications and the comparison with experiments shows promising agreement

Design o combined propeller/stator propulsion system th special attention to scale effects

The design of a well performing pre-swirl stator (PSS) should strictly account for the full scale flow environment as met individually by each stator fin. In the European GRIP project an actual design has been delivered for a bulk carrier and was installed for trials. The results of the speed/power measurements could be compared to the trial data obtained 2 weeks earlier, when the stator was not mounted. The power gain with mounted stator was considerable. As the design was adapted to a computed full scale flow environment, the question arises whether such results could have been predicted prior by model tests performed with geometrical similar stator and propeller. For this purpose we analysed the model propulsion mode numerically. In summary the model scale analysis revealed considerable differences to the full scale setup, if the performance of the fins is compared individually. However in this numerical assessment of scale effects the overall decrease of power at the propeller showed only minor changes between model and full scale. The second question coming up after the trials have been completed addresses the propeller and its drop in RPM, an expected and forecasted result. Such an RPM change in itself will have a positive effect on the required power due to a reduction of viscous effects on torque. On the other hand due to requirements from the engine side it will usually be necessary to adapt the propeller geometry and compensate the RPM drop. It is investigated numerically, to what extent the required power will increase for such an RPM adapted propeller

Numerical and Experimental Optimization Study on a Fast, Zero Emission Catamaran

The present study focuses on the hydrodynamic hull form optimization of a zero emission, battery driven, fast catamaran vessel. A two-stage optimization procedure was implemented to identify in the first stage (global optimization) the optimum combination of a ship’s main dimensions and later on in the second stage (local optimization) the optimal ship hull form, minimizing the required propulsion power for the set operational specifications and design constraints. Numerical results of speed-power performance for a prototype catamaran, intended for operation in the Stavanger area (Norway), were verified by model experiments at Hamburgische Schiffbau Versuchsanstalt (HSVA), proving the feasibility of this innovative, zero emissions, waterborne urban transportation concept

Implementation of zero emission fast shortsea shipping and design of the Stavanger demonstrator

The paper describes the implementation of state-of-the-art “Industry 4.0” methods and tools, of a holistic ship design optimization and of modular production methods, as well as of advanced battery technologies in the development of an innovative, fully electrical, fast zero-emission catamaran for waterborne urban transport. The design of a fast catamaran passenger ferry prototype (Medstraum), planned for operation as a waterborne shuttle in the Stavanger/Norway area, and of a replicator for operation at the Thames River/London are elaborated, including on land infrastructural issues that are necessary for their operation. The presented research is in the frame of the H2020 funded project “TrAM—Transport: Advanced andModular” (www.tramproject.eu)