On two methods of determining the forced speed reduction due to the deck wetness

Two methods of calculation of the forced ship speed reduction due to the deck wetness because of the longitudinal motions in head seas have been compared. According to the first method, the standard frequency of the deck wetness occurrence is viewed as constant. However, the recommendations of different authors on the selection of the parameter vary significantly within this approach. Consequently, the traditional method does not show the actual conditions of the captain’s making a decision about the forced ship speed reduction. As opposed to the traditional method, in the second method the standard frequency of the deck wetness occurrence is found as a function of the ship speed and the wave intensity. The new approach, which is based on visual impression criterion, allows us to clarify the choice of standard frequency of deck wetness occurrence. It is assumed that the visual determination, which is assessed in the experiment as a high degree of the deck wetness, conditions, in which the captain makes a decision about the forced ship speed reduction.