Computational Fluid Dynamics (CFD) plays a pivotal role in the maritime industry, offering precise speed-power estimates for vessels. At Normec Verifavia, we utilize CFD analysis to facilitate the accurate determination of a ship’s actual reference speed, crucial for EEXI compliance evaluations. This approach not only aligns with regulatory demands but also enables the effective evaluation of Energy Saving Devices (ESD) for retrofitting strategies, ensuring compliance with EEXI requirements.
CFD is a branch of Fluid dynamics that solves flow related problems using high powered computers to run on 3D models. It is based on the Navier-Strokes equation generally and the Reynolds- Averaged Navier Strokes (RANS) equation for turbulent flows.
CFD has widespread application in aerospace, oil & gas, automobile, marine sectors and many more. For ships, it is conducted during their concept & initial design stages to generate the speed – power curves. It is a powerful and economical tool when compared to conventional towing tanks.
One of the major parameters that affects the Attained EEXI in a powerful manner is the reference speed(vref) of the vessel. This is the speed of the Vessel for 75% MCR at EEXI draft condition and is obtained from the sea trials report of the vessel. The sea trial is conducted at the ballast draft condition for bulk carriers and container ships while their EEXI draft requirement is the summer load line and 70% deadweight condition, respectively. Under these conditions, where the required speed power curve is unavailable, the reference speed is calculated as per the formula given in the EEXI calculation guidelines (MEPC 333(76)), this formula is based on statistical data of ships of various types and has a 5% speed reduction margin. This leads to a higher EEXI number compared to EEXI number calculated using the actual reference speed.
The alternative to this formula is to estimate the Vref using numerical calculations such as CFD etc. and to calibrate the estimates with the speed trial reports. This will result in a more accurate and a favourable EEXI number.
Furthermore, CFD simulations can be used to predict ship specific speed-power curves for ESD (Energy Saving Devices) modification proposals. Energy saving devices that change the powering characteristics of a ship such as propeller ducts & modified bulbous bows need ship specific sea trials, towing tank tests or CFD reports that can support the impact of ESDs on the ship speed in EEXI calculations.
Structural & hull shape data is obtained.
3D Digital hull modal is generated.
CFD meshing is done for the 3D model and CFD Analysis is run.
Results are aggregated and a Test report is generated.
CFD (Computational Fluid Dynamics) uses computer simulations to analyze fluid flow around objects like ships. For EEXI, we use CFD to estimate a ship’s reference speed (vref) accurately, which is crucial for calculating EEXI. This approach offers better EEXI results by avoiding potential overestimation of OPL due to the usage of approximation formulas in the regulations.
Yes! CFD simulations can predict the impact of specific ESDs on your ship’s performance, helping you:
Contact Normec Verifavia today. We can discuss your specific needs and provide a customized solution to help you achieve EEXI compliance efficiently and cost-effectively.
