Experimental and numerical study of the hydrodynamics of a flapping fin at zero speed

The flapping fins can be used as effective actuators of roll stabilizers at zero speed. They provide anti-roll torques to reduce the roll motion of ships in waves. The effects of roll amplitude, flapping frequency and aspect ratio on the hydrodynamic forces and moments at zero speed have been studied through experiments and numerical simulations. It is found that the forces and moments can be described using the added mass forces and damping forces respectively. Empirical formulas to calculate the forces and moments have been derived. The flapping frequency has no significant effects on the force coefficients and moment coefficients. The drag coefficients can be described by an exponential function of KC number, the added mass coefficients are the function of roll amplitude and aspect ratio due to the 3D flow separation.