Ship powering prediction from self-propulsion load varying tests

A method is presented for predicting full-scale ship powering performance from model load-varying test data. The method follows the recommendations for powering prediction of the Specialist Committee on Unconventional Propulsors of the 22nd IITC: specifically, that ship models fitted with unconventional propulsors should be tested as a unit and not broken down into component tests of hull, propulsor, rotor and stator components, and that extrapolation of full scale powering should be done using self propulsion load varying tests of the geometrically similar ship model and geometrically similar propulsor. Values of a form factor, a resistance and a thrust deduction fraction are found from an analysis of the under/overload tests. The full scale torque and thrust coefficients are estimated from the model propeller data in the behind condition. Results are presented for a conventional twin screw icebreaker for which self-propulsion data and full scale trials results were available. Comparisons are made between the results and an extrapolation done using the IITC 1978 method. The effects of using different friction lines are discussed and included in the analysis. A discussion of the choice of appropriate correlation coefficients is included.