Numerical research on control of longitudinal motion of ship in waves by T-foil

Abstract

[Objectives] A T-foil with an active control system can provide higher lift force and improve the seakeeping of a ship. It is necessary to calculate the anti-vertical motion effect with the different control signals.[Methods] The motion responses of the Wigley model in different wavelengths among three different Froude numbers are obtained via the slender body theory, and the lift force model of a T-foil is established. The torque control is used to obtain the governing equation of the T-foil's swing angle by analyzing the control signal. On the basis of calculating the motion of the Wigley model, the vertical motions of a ship with a T-foil in different control signals are calculated in time domain, and the attenuation effect with the three different control signals is compared. Finally the multi-signals hybrid control is studied preliminarily.[Results] The results show that the T-foil with torque control can reduce 32.43% of the heave and 57.62% of the pitch angle response extremum, and can provide a reduction of more than 61.17% in bow acceleration at peak response compared with a ship without a T-foil and with a high Froude number. The anti-vertical motion effect in the condition of Fr=0.3 is more obvious when the lift moment is controlled by the pitch angle signal, and as the speed of the ship increases, using the control signal of pitch angular velocity can obtain a lower vertical motion response.[Conclusions] In practical application the swinging angle of the T-foil can be controlled by different signals and control parameters at different speeds.

Keywords

• T-foil
• slender body theory
• longitudinal attenuation
• torque control