Evaluation of Resistance, Sinkage and Trim, Self Propulsion and Wave Pattern Predictions

Kapitel i bok, 2014

In Chap. 2 results in several areas are discussed. Resistance predictions were requested for all three hulls and there is a large number of submissions. It is found that for grid sizes larger than 3M cells all submissions are within 4 % of the measured data. The mean comparison error (data-simulation) is only −0.1 % and the mean standard deviation is 2.1 % of the data value, excluding self-propelled cases for which the error is larger. There is no discernible effect of the turbulence model; two equation models work as well as the more advanced ones. Sinkage and trim exhibit large comparison errors for the smallest Froude numbers, but this is likely to be due to measurement inaccuracies. For Froude numbers above 0.2 the mean comparison error is around 4 % and the standard deviation 8–10 %. Self-propulsion results are reported with real operating propellers as well as modeled ones. For KT and KQ the mean comparison errors are 0.6 and − 2.6 % resp. The standard deviations are 7.0 and 6.0 % resp. Comparing actual and modeled propellers it is seen that the actual propeller has a much smaller mean standard deviation. For KT it is half, and for KQ it is only 1/3 of that of the modeled propeller. There is no clear advantage when it comes to comparison error, however. In general, the wave contour on the hull and at the wave cut closest to the hull is well predicted. Further away from the hull the results differ considerably between the methods. The best submissions for all three hulls capture all the features of the waves out to the edge of the measured region.