HAISHEN is a long-ranged and highly maneuverable AUV which has two operating modes： glider mode and flapping-foil propulsion mode. As part of the vehicle development, a three-dimensional mathematical model of the con...HAISHEN is a long-ranged and highly maneuverable AUV which has two operating modes： glider mode and flapping-foil propulsion mode. As part of the vehicle development, a three-dimensional mathematical model of the conceptual vehicle was developed on the assumption that HAISHEN has a rigid body with two independently controlled oscillating hydrofoils. A flapping-foil model was developed based on the work done by Georgiades et al. （2009）. Effect of controllable hydrofoils on the vehicle stable motion performance was studied theoretically. Finally, a dynamics simulation of the vehicle in both operating modes is created in this paper. The simulation demonstrates that： （1） in the glider mode, owing to the independent control of the pitch angle of each hydrofoil, HAISHEN travels faster and more efficiently and has a smaller turning radius than conventional fix-winged gliders; （2） in the flapping-foil propulsion mode, HAISHEN has a high maneuverability with a turning radius smaller than 15 m and a forward motion velocity about 1.8 m/s; （3） the vehicle is stable under all expected operating conditions.展开更多
The vortex formation and organization are the key to understand the intrinsic mechanism in flying and swimming in nature. The vortex wake of dual-flapping foils is numerically investigated using the immersed boundary ...The vortex formation and organization are the key to understand the intrinsic mechanism in flying and swimming in nature. The vortex wake of dual-flapping foils is numerically investigated using the immersed boundary method. Beside the deflection of the reversed von-Kármán vortex street, an interesting phenomenon, the deflection of the von-Kármán vortex street, is observed behind the dual-flapping foils. The deflected direction is not according to the initial direction of biplane’s flapping motion. And the deflection angle is related to the difference between upward and downward deflecting velocities.展开更多
The water environment of swimming fish in nature is always complex which includes various vortices and fluctuations. In order to study the interaction between the fish and its surrounding complex flow, the physical mo...The water environment of swimming fish in nature is always complex which includes various vortices and fluctuations. In order to study the interaction between the fish and its surrounding complex flow, the physical model with a D-section cylinder placed at the front of a flapping foil is employed. The D-section cylinder is used to produce vortices to contact with the foil as well as the vortices shed from the foil. According to the experimental work of Gopalkrishnan et al., there are three interaction modes between vortices shed from the cylinder and the flapping foil, which are expanding wake, destructive interaction and constructive interaction. Here in this article, three of those typical cases are picked up to reproduce the vortices interaction modes with the modified immersed boundary methods and their hydrodynamic performances are studied further. Results show that, for expanding wake mode and destructive interaction mode, the incoming vortices contact with the foil strongly, inducing relative low pressure domains at the leading-edge of the foil and enlarging the thrust of foils. For constructive mode, the foil slalom between the shed vortices from the D-section cylinder do not contact with them obviously and the foil＇s thrust is only enlarged a little.展开更多
The flapping foil based on bionics is a sort of simplified models which imitate the motion of wings or fins of fish or birds. In this paper, a universal kinematic model with three degrees of freedom is adopted and the...The flapping foil based on bionics is a sort of simplified models which imitate the motion of wings or fins of fish or birds. In this paper, a universal kinematic model with three degrees of freedom is adopted and the motion parallel to the flow direction is considered. The force coefficients, the torque coefficient, and the flow field characteristics are extracted and analyzed. Then the propulsive efficiency is calculated. The influence of the motion parameters on the hydrodynamic performance of the bionic foil is studied. The results show that the motion parameters play important roles in the hydrodynamic performance of the flapping foil. To validate the reliability of the numerical method used in this paper, an experiment platform is designed and verification experiments are carried out. Through the comparison, it is found that the numerical results compare well with the experimental results, to show that the adopted numerical method is reliable. The results of this paper provide a theoretical reference for the design of underwater vehicles based on the flapping propulsion.展开更多
文摘HAISHEN is a long-ranged and highly maneuverable AUV which has two operating modes： glider mode and flapping-foil propulsion mode. As part of the vehicle development, a three-dimensional mathematical model of the conceptual vehicle was developed on the assumption that HAISHEN has a rigid body with two independently controlled oscillating hydrofoils. A flapping-foil model was developed based on the work done by Georgiades et al. （2009）. Effect of controllable hydrofoils on the vehicle stable motion performance was studied theoretically. Finally, a dynamics simulation of the vehicle in both operating modes is created in this paper. The simulation demonstrates that： （1） in the glider mode, owing to the independent control of the pitch angle of each hydrofoil, HAISHEN travels faster and more efficiently and has a smaller turning radius than conventional fix-winged gliders; （2） in the flapping-foil propulsion mode, HAISHEN has a high maneuverability with a turning radius smaller than 15 m and a forward motion velocity about 1.8 m/s; （3） the vehicle is stable under all expected operating conditions.
文摘The vortex formation and organization are the key to understand the intrinsic mechanism in flying and swimming in nature. The vortex wake of dual-flapping foils is numerically investigated using the immersed boundary method. Beside the deflection of the reversed von-Kármán vortex street, an interesting phenomenon, the deflection of the von-Kármán vortex street, is observed behind the dual-flapping foils. The deflected direction is not according to the initial direction of biplane’s flapping motion. And the deflection angle is related to the difference between upward and downward deflecting velocities.
基金Project supported by the National Natural Science Foundation of China(Grant No.10872181)the National Key Basic Research Program of China(973 Program,Grant No.2009CB724303)the Fundamental Research Funds for the Central Universities(Grant No.2010QNA4015)
文摘The water environment of swimming fish in nature is always complex which includes various vortices and fluctuations. In order to study the interaction between the fish and its surrounding complex flow, the physical model with a D-section cylinder placed at the front of a flapping foil is employed. The D-section cylinder is used to produce vortices to contact with the foil as well as the vortices shed from the foil. According to the experimental work of Gopalkrishnan et al., there are three interaction modes between vortices shed from the cylinder and the flapping foil, which are expanding wake, destructive interaction and constructive interaction. Here in this article, three of those typical cases are picked up to reproduce the vortices interaction modes with the modified immersed boundary methods and their hydrodynamic performances are studied further. Results show that, for expanding wake mode and destructive interaction mode, the incoming vortices contact with the foil strongly, inducing relative low pressure domains at the leading-edge of the foil and enlarging the thrust of foils. For constructive mode, the foil slalom between the shed vortices from the D-section cylinder do not contact with them obviously and the foil＇s thrust is only enlarged a little.
基金Project supported by the National Natural Science Foundation of China(Grant No.50905040)
文摘The flapping foil based on bionics is a sort of simplified models which imitate the motion of wings or fins of fish or birds. In this paper, a universal kinematic model with three degrees of freedom is adopted and the motion parallel to the flow direction is considered. The force coefficients, the torque coefficient, and the flow field characteristics are extracted and analyzed. Then the propulsive efficiency is calculated. The influence of the motion parameters on the hydrodynamic performance of the bionic foil is studied. The results show that the motion parameters play important roles in the hydrodynamic performance of the flapping foil. To validate the reliability of the numerical method used in this paper, an experiment platform is designed and verification experiments are carried out. Through the comparison, it is found that the numerical results compare well with the experimental results, to show that the adopted numerical method is reliable. The results of this paper provide a theoretical reference for the design of underwater vehicles based on the flapping propulsion.
