A Methodological And Experimental Study Of T-foil Control Of Trimaran Hulls In Waves

Trimaran has better rapidity comparing with the monohull.However,large longitudinal movement during high speed navigation has become the bottleneck problem that restricts the development and application of this shipform.The active control system of T-foil operates on the bottom of the bow.It can timely adjust the attack angle according to ship's motion.The lift moment of counter movement is generated,which can effectively improve the seakeeping.The research on active control mainly includes the establishment of control method and the practical application of control system.In order to propose T-foil's active control system for trimaran,this paper focuses on the above.The framework of this paper is as follow:Firstly,the control theory of T-foil is expounded.Based on aerofoil theory,the mathematical model of T-foil is established and its lift performance is calculated.The governing equation is introduced by establishing the proportional relation between the angular motion of hull and the lift moment of T-foil.The solution method of each control parameter is presented.The governing equation is optimized,and the expression of the governing equation and the control variables of the swinging angle are analyzed when different angular motions are used as the control signal of the lifting moment.Secondly,by combining the governing equation with the time-domain boundary integral method,a time-domain calculation method for calculating the ship's motion under the control of active T-foil is obtained.In order to determine the best motion control signal,the attenuation effects for Wigley hull's motion by different control signal is compared.The result show the pitch angular velocity is the optimized signal for the T-foil's lifting moment control.Thus,the original governing equation is optimized,which provides guidance for the model test of active control.Thirdly,in order to verify the effectiveness of the control method,the embedded control program and device for T-foil active control model test are designed and developed,and T-foil active control system for model test is constructed.The real-time control of T-foil's swinging angle is realized.The model test of trimaran in regular and irregular waves is carried out.Heave,pitch and bow acceleration response of the fore-body trimaran in regular waves are measured.The attenuation effect of T-foil is verified by comparing the changes of motion parameters under active and passive control.The results show the active T-foil with the control signal of pitch angular velocity can reduce the naked model's heave by more than 50%,pitch angle and bow acceleration by 60%,and cut down the pitch and bow acceleration by 35%and heave by 29%comparing with the passive control under the higher sea state.The applicability of the method to the trimaran ship is verified.Moreover,it is also found that the fore-body trimran with active T-foil has better hydrodynamic performance under higher sea state.Finally,in order to prove the suppression effect of T-foil on the slamming pressure,the movement and slamming pressure of trimaran in severe sea conditions are calculated numerically by CFD.The result show that T-foil can reduce the slamming pressure at the bottom of cross deck by more than 40%.The above research results prove the effectiveness and practicability of the T-foil's active control system proposed in this paper,which can effectively suppress trimaran's heave and pitch and bow acceleration in the actual sea condition.