EEXI Vref estimation in the absence of Sea trial or model test data

One of our clients approached us with a unique problem. A handy size bulk carrier in their fleet built in the early 2000s had no records of sea trials or model tests. While checking EEXI compliance using empirically calculated reference speed at 75% MCR, the required Engine Power Limitation (EPL) was high and unpractical.

The way out decided was a CFD analysis to ascertain a realistic reference speed of the vessel. To make matters worse, the Owners were not aware of any sister vessel or a similar vessel. The propeller geometry and open water characteristics were not available as well.

SEDS has access to a large database of vessels through its parent firm. With appropriate permissions in place, the engineers went through the records and zeroed in on the best match to be used as a similar vessel as defined in IACS Rec. 173.

The procedure requires CFD analysis of both vessels (similar vessel and target vessel) at multiple speeds and power settings to generate speed-power curves. Good match was observed between the CFD analysis and the model tests/sea trial report. The scope was completed with a detailed report which was approved by DNV (Classification Society).

CFD analysis gave an improvement of the reference speed by more than a knot (from empirical calculation), which was discussed with the Class and agreed as realistic – to the delight of our client.

 

Wave elevation of the target vessel

Y+ of the target vessel

 

~ SEDS CFD Team