Numerical Simulation And Experimental Research On Propulsion Of Bionic Hydrofoil

Due to the abundant resources contained with the marine space, the technical inputs for marine development are increasing gradually. A variety of complex engineering applications and underwater environment improve the requirements for the propulsive performance of underwater navigator. The traditional propellers have the disadvantage s of low efficiency, poor maneuvering performance, big noise and other shortcomings, which greatly limits their application in narrow, complex and dynamic environments. To overcome these shortcomings and meet the future needs of marine development and exploration, it is necessary to find more excellent new underwater propulsion. After millions of years of evolution, marine life acquired extraordinary underwater sports performance, so bionic propulsion becomes a research focus of underwater propulsion technology.The swimming creatures flap their fins or foils in symmetric or asymmetric forms, in which the propulsive efficiency of the symmetrical flapping is relatively higher than the asymmetric flapping and asymmetrical flapping may obtain a larger thrust or lift under certain conditions. In most engineering applications, flapping hydrofoil is free only in lateral movement so that this engineering is relatively easy to achieve because of the reducing of the freedom of movement, however, the bionic prototype do es not accurately reflect the motion of the observed object under this restriction.We adopt the numerical and experimental methods in the investigation of the bionic hydrofoils’ flapping motion. Firstly, we build the kinematics model of the flapping motion which has three degree of freedom based on the two degree of freedom motion which consist of heave and pitch motion s. We solve and simulate the flapping motion of bionic hydrofoils numerically with the software Fluent based on the three-dimensional unsteady and incompressible fluid equations, achieving the thrust, lift, torque and flow field structure generated in the flapping process of the bionic hydrofoils. Through analyzing the flow field generated in the process of hydrofoil flapping, we explain the propulsion mechanism of bionic hydrofoil. The results of the analysis prove that the high propulsive efficiency and big propulsion force are difficult to obtain at the same time. Secondly, we analyze the influence of the motion parameters and geometric par ameters on the hydrodynamic performance of the bionic hydrofoils. And then we employ the Response Surface Methodology to investigate the combined effects of the multiple motion parameters on the propulsive performance through which we achieve a polynomial prediction model which can provide reference on the design of future bionic propeller. At last, we design an economical and feasible experimental apparatus to simulate the bionic motion of the hydrofoils. The heave motion, pitch motion and the drag motion of the hydrofoil can be achieved by a servo control system. We use two pull/pressure sensors to obtain the real time propulsive force and lift force generated in the process of the foil flapping. Our experimental apparatus provide an verification support o n the numerical simulation investigations in hydrodynamic performance and flow field structure generated in the flapping process of bionic hydrofoils.