PREDICTION OF MOTION CHARACTERISTICS ON SWATH TYPE FLOATING STRUCTURE USING TWO-DIMENSIONAL FRANK CLOSE-FIT TECHNIQUE

Abstract

The unique shape of SWATH which consists of two submerged hulls connected to the cross deck via slender struts has brought an excellent sea keeping quality. This makes an extensive study on the SWATH motion characteristics an important part in its design process. This paper describes the utilization of mathematical model to predict such vessel motions based on the Frank Close-Fit technique combined with the well-known 2-D strip theory. This technique was applied to compute the radiation, incident wave excitation and diffraction compo nents. These three components are then substituted into 5-DOF differential equations for SWATH motion in regular wave to attain its motion responses, namely sway, heave, roll, pitch, and yaw. SWATH motions were identified due to beam sea ( (90Ëš) quartering sea (I35Ëš) and head sea (180Ëš). The results of computation generally are in good agreement with experimental data. Certain discrepancies, especially in the peak value of roll motion are primarily brought about the absence of viscous damping. Slight discrepancies in the horizontal mode of motions, namely surge and yaw, are identified due to the harnesses effec. applied to the physical model. It may be concluded at this stage that the mathematical model is considered appropriate to be applied in the preliminary design of SWATH type vessels .