In marine engineering,appendages such as fin stabilizers and/or T-foils are made to rotate and to reduce the motion of ships.Research on the hydrodynamics of ships fitted with active appendages has significantly impro...In marine engineering,appendages such as fin stabilizers and/or T-foils are made to rotate and to reduce the motion of ships.Research on the hydrodynamics of ships fitted with active appendages has significantly improved the design and control of such ships.However,most studies focus on fixed rather than rotating appendages,thereby ignoring the hydrodynamic unsteadiness of active appendages.To enhance the reliability and precision of the numerical simulations,we propose the use of overlapping grids for simulating advanced catamarans fitted with a pair of rotating T-foils under each bow.The fundamental purpose of the overlapping grid technique is to realize information exchange via regional overlap sharing in each subdomain of the computing domain,instead of using the method of boundary sharing,thus greatly alleviating the difficulty of generating the subdomain grid;moreover,the technique guarantees the quality of the subdomain grid.Within the main computational domain,a subdomain was allocated to accommodate the T-foil.Overlapping meshes near the interface between the two domains enable information flow during the simulation;the overlapping grids are updated at every iteration step because the subdomain rotates.The instantaneous trim and sinkage responses of the catamaran to the T-foil rotation were reproduced.From the moment the active T-foil stopped moving,there was no change in the ship’s sailing attitude,indicating that the response was in real time.By comparing with EFD data,the numerical results showed reasonable agreement,indicating the feasibility and effectiveness of the technique in simulating the hydrodynamics of ships fitted with active appendages.展开更多
A novel type of control law was adopted to reduce the vertical acceleration of a fast ferry as well as the motion sickness incidence suffered by the passengers onboard by means of a submerged T-foil.Considering the sy...A novel type of control law was adopted to reduce the vertical acceleration of a fast ferry as well as the motion sickness incidence suffered by the passengers onboard by means of a submerged T-foil.Considering the system changing characteristics under high disturbances,a model-free approach was adopted.In addition,an upgraded proportional-derivative(PD)controller with correction terms resulting from a fast-online estimation of the system dynamics was designed.The overall controller,known as intelligent PD(i-PD)controller,was tested,and the obtained results were compared with those of a classic PD controller.The controllers were also tested in a changing environment and at different operating velocities.The results confirmed the effectiveness of the i-PD controller to smooth the motions with low computational cost control schemes.Furthermore,thanks to ability of the i-PD controller to continually update the estimated dynamics of the system,it showed a better reduction in both vertical motions and the seasickness level of the passengers with the needed robustness under external disturbances and system changing parameters.展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.51509053)
文摘In marine engineering,appendages such as fin stabilizers and/or T-foils are made to rotate and to reduce the motion of ships.Research on the hydrodynamics of ships fitted with active appendages has significantly improved the design and control of such ships.However,most studies focus on fixed rather than rotating appendages,thereby ignoring the hydrodynamic unsteadiness of active appendages.To enhance the reliability and precision of the numerical simulations,we propose the use of overlapping grids for simulating advanced catamarans fitted with a pair of rotating T-foils under each bow.The fundamental purpose of the overlapping grid technique is to realize information exchange via regional overlap sharing in each subdomain of the computing domain,instead of using the method of boundary sharing,thus greatly alleviating the difficulty of generating the subdomain grid;moreover,the technique guarantees the quality of the subdomain grid.Within the main computational domain,a subdomain was allocated to accommodate the T-foil.Overlapping meshes near the interface between the two domains enable information flow during the simulation;the overlapping grids are updated at every iteration step because the subdomain rotates.The instantaneous trim and sinkage responses of the catamaran to the T-foil rotation were reproduced.From the moment the active T-foil stopped moving,there was no change in the ship’s sailing attitude,indicating that the response was in real time.By comparing with EFD data,the numerical results showed reasonable agreement,indicating the feasibility and effectiveness of the technique in simulating the hydrodynamics of ships fitted with active appendages.
文摘A novel type of control law was adopted to reduce the vertical acceleration of a fast ferry as well as the motion sickness incidence suffered by the passengers onboard by means of a submerged T-foil.Considering the system changing characteristics under high disturbances,a model-free approach was adopted.In addition,an upgraded proportional-derivative(PD)controller with correction terms resulting from a fast-online estimation of the system dynamics was designed.The overall controller,known as intelligent PD(i-PD)controller,was tested,and the obtained results were compared with those of a classic PD controller.The controllers were also tested in a changing environment and at different operating velocities.The results confirmed the effectiveness of the i-PD controller to smooth the motions with low computational cost control schemes.Furthermore,thanks to ability of the i-PD controller to continually update the estimated dynamics of the system,it showed a better reduction in both vertical motions and the seasickness level of the passengers with the needed robustness under external disturbances and system changing parameters.
