Numerical Analytic Technique For Bionic Fish Free Swimming And Motion Control

With the increasing exhaustion of the resources on land, the human beinghas to look to other places. Not only does the ocean take up 71% of the earthsurface which is a sure sign of enormous resources and minerals, it is also muchmore realistic and effective to turn to the ocean for help compared with otherplanets. Currently, the man-made submersible vehicle and the underwater robotdriven by conventional propulsive methods have such flaws as poor starting,acceleration and maneuverability and bad hidden performance. However, the fish isgreatly impressive as on the one hand it elegantly utilizes the fluid mechanics toobtain good coasting and motion ability, it also can use all the applicable power in theflow like the waves and vortex to improve the propulsion efficiency. As a result, thefish has enough reference value and guidelines for the research into the vehiclesabove. Just out of the objective, the 3D incompressible unsteady N-S equationis solved using the pseudo artificial compression method, and the issue of the carpand tuna free swimming is discussed, later the database concerning the carp and tunais established, and finally the motion control of the bionic fish is analysed.The main work concerned and the numerical simulation results comprisethe following aspects:First, based on the work done, a fish grid generation program is developed.With the program, any random streamlined shape fish body grid can beproduced knowing the fish shape before hand.Secondly, the database for the carp and tuna is established through the numericalsimulation and modification of the symbolic control parameters such as thefrequency,amplitude,wavelength and RE Number. Through the analysis of the fishforward swimming speed and force, the following characteristics can be found: (1) theeffect for the amplitude on the speed is apparent, when amplitude increases, the speed increases at the same rate and this is also true for the pressure force and friction whileits effect is limited on the thrust. (2) frequency has the same great influence on boththe speed and the force which is better and different from the amplitude. (3)Thewavelength plays a diversified role, the increase barely affects the quantity of thespeed and force. As for the speed, there is a staggering role, and the force, anadvancing role. It also takes up the role of coupling effect with the other controlparameters. (4) The RE Number has a positive effect on the speed, when RE increases,the fish swims faster while the increase rate gets slower gradually; when it comes tothe force, it is a little bit complicated as the thrust will get larger while the pressureforce and friction force will get smaller, and the friction force, further smaller.Finally, a deflection angle in combination with overset grid is proposed torealize the bionic motion control trace. Both the symbolic O shape trace and Sshape trace are well dealt with here. And the factors that influence its motiontrace are revealed. Through the simulation, it is found that the modification ofthe frequency and amplitude will effect its motion trace; it is also shown thatthe deflection angle can be altered to change the area the trace covers. It isdisclosed that the vortex ring that shed form the vortex wake is the fundamentalreason for the fish to swim forward or turn around.