Modelling of Propeller

The propeller is modelled by employing the regression equations of the Wageningen B-Series data, References 26, for estimation of KT and KQ for both the 4- and 5-bladed B-Series propellers given by:

where and are the regression coefficients of and respectively. Where is the expanded area, is the disc area of the propeller, P is the propeller pitch, D is the propeller diameter and J is the advance ratio.

In straight-ahead motion, the flow to the propeller is affected by the presence of the hull in front of the propeller. As a result, the flow to the propeller will be reduced due to the wake distribution. When the ship starts to drift and/or turn the flow-pattern at the stern will be changed and the flow to the propeller will take certain angle of attack which depends on the ship particulars, stern shape and type of motion. The effect of sway and yaw on the wake has been studied experimentally and reported in References 27. The wake at the propeller disc is given as a function of the transverse velocity at the propeller disc.

where is the non-dimensional transverse velocity at the propeller disc and is given by:

is the non-dimensional position of the propeller from midships, is the mean wake fraction in straight ahead motion, and is the mean wake fraction when the ship drifts and turns at the same time. Where is the non-dimensional transverse velocity of the ship and is the non-dimensional yaw rate of the ship.