ABSTRACT

For many years it has been best practice to validate results of numerical ship performance simulations against the results of towing tank experiments, both conducted at model-scale. While it is hardly possible to increase the scale of towing tanks considerably, with ever-increasing computational power, it became feasible to run numerical simulations in ship-scale. Thus, eliminating uncertainties arising from poorly predicted flow phenomena with models that are scale-sensitive and also from scaling up results to ship scale using empirical methods.

Unfortunately, to validate numerical ship scale results, the marine community was lacking high-quality experimental data measured on a suitable ship operating at sea under calm/measurable conditions. To overcome this, the Lloyd’s Register Ship Performance Group (LR) provided such experimental data by conducting sea trial measurements on a general cargo vessel to assess and develop the capabilities of numerical tools to increase the confidence in ship-scale Computational Fluid Dynamics (CFD).

Accordingly, this study presents the numerical validation of the LR ship-scale experimental data for hull resistance, propeller open water characteristics, self-propulsion predictions and propeller cavitation cases, all simulated in ship-scale conditions. The computations were performed blind, without knowing the experimental results, using a commercial Reynolds-Averaged Navier Stokes (RANS) solver with an implemented Volume of Fluid (VoF) model for the free surface prediction and the Schnerr-Sauer cavitation model for the prediction of the propeller cavitation. For the self- propulsion simulations, a sliding mesh approach was used for describing the rotational motion of the propeller. In order to establish the self-propulsion point, the ship speed was varied at a constant propeller rotation rate which was given as input by LR. The numerically predicted cavitation was compared to video recordings of the sea trial propeller cavitation patterns. The simulated cases compared very well to the experimental data for resistance, propeller open water, power and cavitation prediction.