Page 241 - Introduction to Naval Architecture

226 PROPULSION

The thrust power is the product of thrust and velocity and for the
same Froude number:

Correspondingly for torque it can be shown that:

The ratio of torques for geometrically similar propellers at the same
advance coefficient and Froude number will be as the fourth power of
the linear dimensions. That is:

Coefficients for presenting data
It has been shown that:

Substituting V^ = NDJ'm these expressions:

Non-dimensional coefficients for thrust and torque are:

The other parameter of concern is the propeller efficiency which can be
defined as the ratio of output to the input power. Thus:

Thrust and torque coefficients and efficiency when plotted against
advance coefficient produce plots as in Figure 9.13. Both thrust and