Estimation of full-scale propeller torque and thrust using free-running model ship in waves

• Full-scale equivalent ship motion by the rudder effectiveness and speed correction.
• Effective inflow velocity to propeller (EIVP) in waves by torque/thrust identity.
• Estimation of the wave component in EIVP using measured model ship speed.
• Estimation of full-scale EIVP taking into account of scale effect on wake.
• Proposal of new free-running model ship test procedure incorporating engine model.

The authors propose a method to estimate full-scale propeller torque and thrust consisting of low-frequency and high-frequency components in waves by free-running model ship test. The duct fan auxiliary thruster (DFAT) (Tsukada et al., 2014 and Tsukada et al., 2013) and the rudder-effectiveness and speed correction (RSC) (Ueno and Tsukada, 2015; Suzuki et al., 2014 and Suzuki et al., 2015) ensure similar model ship motion to full-scale in wind and waves, where RSC controls the model ship propeller rate of revolution and the auxiliary thrust depending on instantaneous model ship speed. Analyzing wave component in the effective inflow velocity to propeller, the method estimates full-scale fluctuating propeller torque and thrust in waves. Trial application of the method exemplifies the property of full-scale fluctuating propeller torque and thrust comparing with those of a model ship.This method also makes it possible to incorporate into free-running model ship tests any engine model simulating interaction between propeller torque and engine torque.