Bend Torsion Coupling Vibration Analysis Of Catamaran

In recent years, the proportion of catamaran is increasing in both civil and military ship market. The shape, structure, stress state, and the force relationship between structure and fluid are very different from the mono-hull, so the traditional calculation method and empirical formula is not directly applicable to the catamaran. Ship vibration prediction is the important content of the structural design, especially when the catamaran is used for marine scientific research projects, structure vibration will affect the measurement accuracy, so we should pay extra attention to shock noise reduction in the early stages of design.Vertical vibration is the most common one in several vibration modes of the hull girder, in addition to this, torsional vibration is sometimes more prominent for the structural form of catamaran. Based on this, this paper is to study the vertical bending and torsion coupling vibration form of the catamaran.The calculation methods of ship vibration characteristics include energy method, general program method (boundary element method and finite element method), empirical formula method, transfer matrix method and so on. Among these methods, the most widely used is general procedure method at present. Compared with other methods, this method can simulate the actual structure more accurately and get more accurate results, however, this method has large workload. In different design stages of the ship, it is considered that the precision demand, time and cost as well as some other factors should be taken into account to determine how to calculate the vibration characteristics of the ship. Thus we simplify the catamaran with double beam model in this paper, using the Timoshenko beam theory and thin-walled bar theory to obtain the dynamic differential equation of the double beam model, at last using transfer matrix method to obtain the vibration characteristics of the catamaran. By contrast, calculate the vibration characteristics of the catamaran with three-dimensional finite element method. Relative difference of two methods is less than six percent. It shows that using transfer matrix method to calculate the vibration characteristics of the catamaran is feasible.