Effect of sailing directions on the coupled motion and stability of trimaran in waves

Abstract

Coupled motion is an important factor that affects the safety and stability of ships sailing in waves, especially for rolling coupled with pitch motion. This paper simulates the motions of trimaran in waves and analyzes the motion characters. The open sourced CFD code OpenFOAM is used to predict the trimaran's motions in oblique head waves, oblique stern waves and beam waves. The grid convergence analysis and the comparison with experimental results are carried out to verify the numerical method. Focusing on the coupled motion characteristics and the stability of trimaran under different waves, a comparative analysis of the trimaran's motion state is made. The changing laws of coupled motion characteristics with different forward speed, wave steepness, wavelength and wave headings are studied. The results show that the trimaran has the largest coupled motion of rolling and pitch in the oblique head waves, but the motion is relatively regular and stable; the trimaran has a relatively poor performance in several wave conditions of oblique stern waves and beam waves. Some wave conditions are easily to cause the unstable rolling motion, especially in small wavelength conditions.