ReFRESCO plays major role in and designing Energy Saving


Figure 1


Figure 2


Using Computational Fluid Dynamics (CFD), new insights can be obtained into the working princi- ples of Energy Saving


Devices (ESDs), which all serve to increase the fuel efficiency of a ship. The advantages of using


ReFRESCO to study ESDs are explored in this article.


Bart Schuiling & Guilherme Vaz b.schuiling@marin.nl


14 report


T


he capability of simulating different moving objects, and their interac- tion in one calculation (applying


the so-called Sliding-Interfaces Technique), has increased the range of applications of the viscous-flow CFD code ReFRESCO. This new Sliding-Interfaces Technique enables MARIN to study and reveal the oldest, and perhaps the greatest mystery in the world of maritime propulsion: the reduction in fuel consumption when applying an ESD.


A short introduction to the world of ESDs The idea of saving energy by placing a device in front of the propeller was already published in 1949 by Van Lammeren but the first commercial ESD was probably the Mitsui Integrated Duct Propeller (MIDP) introduced in 1980. Although the working principles responsible for the energy saving were not completely understood, in a world controlled by the second oil crisis, the MIDP was a great success. Shortly afterwards, many other companies came with their own ESD designs. After the eighties, as the world economy recovered and oil prices dropped, interest in


ESDs diminished. However, with the current challenging world economy, increasing oil prices and the upcoming new EEDI regula- tions, an ESD giving a possible 5% power saving again becomes very attractive to many shipowners.


Advantages of CFD By using CFD, there is now the possibility to observe the effects of an ESD in a level of detail, which is im- possible using only model tests (Figure 1). Another advantage of CFD is that the evaluation of many design variations, with small geometrical changes, is more cost efficient compared to model testing. Perhaps, the greatest benefit of CFD is the possibility to evaluate the ESDs at full-scale Reynolds number. The performance of an ESD optimised during model tests, can be severely reduced at full scale. It has often proven difficult to measure the large gains in efficiency that were found in the model tests during a sea trial.


Since the possible gains of ESDs are in the order of 5%, CFD simulations have to be


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