TRIM INFLUENCE ON WATER RESISTANCE TO MOVEMENT OF SMALL PASSENGER SHIP MODEL

Abstract

During the passenger ships operation, significant trim changes with a constant displacement due to the movement of passengers are possible. As a rule, in the design of same ships, model tests are not carried out, and the calculations of the propulsion are made by the prototype or using methods based on serial tests. Resistance curves, calculated in this way, correspond to trim on an even keel, which can lead to errors in determining the required power, the achievable speed and the required parameters of the propulsion system. To determine this influence in the experimental basin of the Admiral Makarov State University of Maritime and Inland Shipping, the towing tests are carried out. Ship model has shape form and dimension ratios, typical for excursion ships of St. Petersburg: length to breadth ratio - 4.0, breadth to draft ratio - about 7.1, block coefficient - 0.57. The curves of the rest resistance coefficients are given for three sitting options - on an even keel, with trim to the bow and trim to the stern. The curves for the model on even keel and with trim to the stern almost coincide, and trim to the bow leads to an increase in the residual resistance coefficient by up to 1.0 ∙ 10-3. Tests are carried out in calm deep water conditions for Froude numbers from 0.14 to 0.35. It is shown that the effect of trim on resistance depends on the ship speed. When designing propulsion systems for small passenger ships, it is proposed to add an allowance to the values of the resistance coefficient in order to take into account possible trim changes.