COMBINED EFD AND CFD APPROACH FOR FULL SCALE SHIP RESISTANCE PREDICTIONS USING THE FORM FACTOR

In this study, a comparison of the experimental full scale ship resistance extrapolation procedure using the ITTC'78 power prediction method with a newly proposed hybrid EFD/CFD approach has been performed for two benchmark ship hull geometries. For both hulls, resistance tests have been performed in the towing tank of HSVA at model scale. From these tests, experimental form factors have been determined according to Prohaska's approach. In addition, CFD simulations have been performed to determine a new numerical flat plate friction line as well as the frictional resistance for both hulls by double body CFD simulations in model and full scale. Based on these simulations, numerical form factors according to Hughes have been derived. Two different turbulence models, the k-. standard and the k-. SST, have been used to obtain the flat plate frictional resistance curve. It has been found that the mean difference between the numerical form factors obtained for model and full scale CFD simulations is 10.4% using the ITTC'57 correlation line. When using the newly established numerical friction line based on the k-. SST model, this mean difference is reduced to mean 6.4%. Based on the results, full scale resistance predictions were performed based on the different form factors that have been derived following the ITTC'78 method. Since no data from sea trials is available, the full scale resistance predictions for the two ship hulls were compared with the results of full scale CFD simulations. It was found that the extrapolation based on the form factor derived from the numerical friction line using the k-. SST shows a 3.1% deviation from the full scale CFD results, while a deviation of 7.1% was observed for the form factor based on the ITTC'57 line.