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Determining the EEDI “minimum propulsion power”, new paper
Recently, SSPA’s experts in seakeeping and ship performance in waves presented a new paper at an international conference, held by RINA (the Royal Institution of Naval Architects). A concise version of the presented paper and the results is available for download.
The introduction of EEDI (the Energy Efficiency Design Index) almost a decade ago, slow steaming and the wish to reduce bunkering costs have resulted in a trend to install less powerful engines in ships. To avoid vessels becoming underpowered and unsafe, IMO (the International Maritime Organization) published an interim guideline. SSPA used the KVLCC2 tanker as a case study and followed the guideline step by step to find the minimum engine size. Our experts used a combination of CFD (Computational Fluid Dynamics) and model tests.
The paper was presented by Frederik Gerhardt, PhD, during the conference “Influence of EEDI on Ship Design & Operation”. Held online 27th May 2020 by the Royal Institution of Naval Architects www.rina.org.uk/EEDI_2020
- “Results show that it is particularly important to determine the added resistance in waves correctly because it dominates the power prediction. Carefully conducted tests in SSPA’s large seakeeping basin are a good way to do this. From the investigation also becomes clear, that the selection of the ‘propulsive’ factors, particularly the thrust deduction factor t, has a significant influence on results”, says Dr Frederik Gerhardt, Senior Technical Specialist for seakeeping and ship performance in waves at SSPA.
About the paper
Title: Determining the EEDI “minimum propulsion power”
Authors: F. C. Gerhardt, M. Kjellberg, B. Korkmaz, K. Ljungqvist and A. Shiri, SSPA Sweden AB, Sweden.
Download
A concise version of the presented paper is available for download:
Determining the EEDI minimum propulsion power.pdf
Full paper incl. additional tables and figures available from: publications@rina.org.uk
About the authors
Frederik Gerhardt is the Senior Technical Specialist for seakeeping and ship performance in waves at SSPA Sweden AB. He is responsible for model tests in SSPA’s Maritime Dynamics Laboratory and is a member of the ITTC Seakeeping Committee.
Martin Kjellberg holds the position of Specialist in seakeeping and ship performance in waves at SSPA Sweden AB and is the main developer of SHIPFLOW MOTIONS at Flowtech International AB.
Burak Korkmaz is a specialist in hydrodynamic predictions and CFD at SSPA Sweden AB. He currently studies towards a PhD at Chalmers University of Technology.
Kasper Ljungqvist holds a position as Project Manager at SSPA Sweden AB. His main focus areas are calm water towing tank tests and hull form development.
Alex Shiri is Senior Researcher and Project manager at SSPA Sweden AB. His main focus is developing combined CFD and EFD methods for marine applications.
Photo
SSPA used the KVLCC2 tanker as a case study and followed the guideline step by step to find the minimum engine size. Our experts used a combination of CFD and model tests.
Research project: Predicting ship performance in waves
SSPA is now conducting a research project to increase the accuracy and efficiency of detecting added resistance in waves experimentally and numerically. More accurate and efficient numerical and experimental procedures will make it possible to cost-effectively predict overall ship performance in a seaway early during the design process and to avoid costly pitfalls.
fw – the unknown factor
Legislation on the EEDI requires the determination of a “weather factor” – fw – reflecting the percentage of its calm-water speed that a ship can maintain in Beaufort 6 and corresponding waves. The higher the fw value, the smaller the speed loss and the better the ship will perform in a seaway. But how do we determine this unknown fw factor, and how do we strike a balance between accuracy and costs? As a member of ITTC, SSPA is actively involved in developing guidelines.
A fair trial – how to obtain the correct EEDI
IMO recently passed a resolution on the Energy Efficiency Design Index (EEDI). This index is a measure of the amount of carbon dioxide a ship emits in relation to its cargo capacity and speed. A ship’s EEDI value must not exceed the allowable limit set by IMO. SSPA can help derive the hydrodynamic part of the EEDI value for new ships.
CFD/EFD Combined methods
SSPA leads the ITTC Specialist Committee on Combined CFD/EFD Methods. The purpose of the committee is to initiate and support the process of introducing combined CFD/EFD methods in ITTC’s procedures. By using the best combination, rather than viewing them as competing methods, we can deliver even better predictions. To facilitate the introduction in our community, the Committee has identified several research areas which need to be addressed.