ROLF is a program for calculating the rolling motion of a monohull ship in waves, particularly used for large roll angles. The rolling motion is simulated, meaning the calculation is performed in the time domain. The computational core of the module is based on the ideas of Söding and Kröger (Rolls program). However, the program used here has been completely rewritten according to current programming guidelines.
Pre-calculations are necessary for the application of ROLF, where transfer functions (here using the linear strip method UtStrip) as well as Pantocarenes in waves are computed. The Pantocarenes are calculated using UTHLANDE's proprietary programs.
There is the option to specify roll damping similar to STRIP. The roll damping of anti-rolling tanks is also taken into account. Furthermore, stabilizer fins with a nonlinear control and a nonlinear force model can be treated, as well as the flow in roll damping tanks (shallow water or U-tanks) can be calculated.
As a result, primarily time series for long- or short-crested waves, especially for roll angle, as well as deflections, velocities, and accelerations at any location, are output. Additionally, these quantities can be statistically evaluated. Loops over different encounter angles, ship speeds, and wave conditions can be calculated. Most results are presented in Cartesian diagrams.
The program finds its application when nonlinear effects are significant in motion: This occurs if the investigated roll angles are large (typically from 10 to 15 degrees onwards), if the hydrostatic restoring moment can no longer be suitably linearized even at small roll angles, or if the ship's lever arms between wave crest and trough vary greatly.