Polar Diagrams

It is often useful to be able to plot seakeeping results in polar format. The polar plot takes the form of a circle, in which the radial axis denotes speed and the angle vector represents the wave direction. The irregular motions available for plotting are heave, surge, sway, pitch, roll and yaw, and total motions at particular locations specified in the input to the short term calculations.

Up to three different motions can be displayed together. Each motion has associated with it a critical value, with the resulting polar plot showing the allowable speed range over the complete heading rosette. The overall allowable range for a combination of motions is the intersection of the individual ranges.

The following diagram shows a typical polar plot, displaying heave (limiting value of 1m), surge (limit of 0.8m) and sway (limit of 0.8m).