A semi-empirical model for ship speed loss prediction at head sea and its validation by full-scale measurements. (1st August 2020) - Lang, Xiao
Abstract: This paper proposes a semi-empirical model to estimate a ship's speed loss at head sea. In the model, the formulas to estimate a ship's added resistance due to waves have been further developed to better consider the ship hull forms, in addition to other main particulars. Based on the model experimental tests of 11 ships in regular head waves, the new formulas have more flexible forms and can better fit the test results than other similar models. In addition, this model proposes a significant wave height based correction factor multiplied to the conventional integration to compute wave resistance in irregular waves. This factor is supposed to consider the impact of coupled ship motions in high waves on a ship's added resistance due to waves. The model is validated by the full-scale measurement from two vessels, a PCTC and a chemical tanker. The encountered weather conditions along the sailing routes are extracted from the reanalysis metocean data. The results indicate that the proposed model can provide quite accurate predictions of ship speed loss in head sea operations. Highlights: A semi-empirical model is proposed to estimate a ship's speed loss at head sea. Formulas to estimate added resistance due to waves are further developed. A wave height related correction factor is proposed in irregular waves. The improved model is validated by experimental data in regular waves from 11 ships. The proposed speed loss prediction model is demonstrated by full-scale measurements.