A PRACTICAL APPLICATION OF AIR LUBRICATION ON A SMALL HIGH SPEED BOAT

초록

The reduction of resistance with lubrication of an air cavity and the similarity relations involved are investigated with a series of towing tank tests on geometrically similar models. Three geometrically similar models of different size are tested in the towing tank of Seoul National University. The results indicate that an introduction of air cavity by artificially supplying air beneath the bottom of a model ship with a backward-facing step is effective for reduction of the model resistance. The lengths of air cavity and the required air flow rates, both of which are directly related to the effective wetted surface area and the overall energy saving are found to be dominated by the Froude number scaling. Both the traditional two-dimensional method and Telfer’s three-dimensional method seem to be applicable to the extension of the model resistances in the tested range if corrections are made to account the changes in the frictional resistance caused by the changes in the effective wetted surface area. Based on the findings obtained above, a small test boat of practical size is constructed and the effect of air cavity on the reduction of ship resistance is studied. The results will confirm the results found in the model tests and assure the practical applicability of the air cavity for the resistance reduction of a real ship.