Pitch and heave control of SWATH using passive fins

SWATH vessels are inherently more prone to large pitching motions as compared with mono-hulls due to the characteristic slender water-plane area design feature. The use of canard fins ie., forward fixed fins, for pitch reduction has been attempted in the past with varying degrees of success. In the initial years, Lewandowski [3] established the efficiency through systematic experimental testing when these types of fins are deployed. This work reports the application of computational (CFD) modeling and simulation for the similar SWATH form, and comparison of data for verification of the results. The results suggest that damping of pitch motion by canard fins can be obtained and the use of fixed after stabilizer fins, help in good improvement of pitch and heave stabilization. In the present study CFD tool with k - ϵ turbulent model has been used to analyze the response behavior of SWATH. The results obtained as drag, steady running trim moment and sinkage without fins, moving at constant speed, which is free to heave with other motions restricted, are validated with experiments done by Lewandowski for calm water condition. The sensitive analysis of canard fin for ship moving at constant speed, is performed to obtain effect on lift coefficient when attached to the hull. The response in calm water and regular waves, with fixed stabilizer fin at a given angle of orientation combined with canard fin at suitable angle shows significant platform stabilization.