Research On Flow-Induced Vibration And Energy Harvesting Performance Of Oscillating Foil Downstream Of A Circular Cylinder

Flow-induced vibration(FIV)is one of the common physical phenomena with great significance in basic research and engineering practice.Utilizing flow-induced vibration to harvest clean energy has become an important research content.This paper proposes a system design using the tandem arrangement of a circular cylinder and an oscillating foil to achieve flow-induced vibration of the foil and harness energy from the inflow.The effect of main system parameters on the flow-induced vibration characteristics and energy harvesting performance of the oscillating foil is researched through numerical simulations.This paper verifies the vibration equation-solving program and simulation method used by establishing a two-dimensional single circular cylinder model.By comparing the results with experimental values and other numerical simulation results,it is found that the trend of amplitude response with reduced velocity change is in good agreement with experimental results,which verifies the accuracy and reliability of the custom program.On this basis,this paper researches flow-induced vibration and energy harvesting characteristics from four system parameters:spacing ratio,damping ratio,spring stiffness,and mass ratio.Firstly,the effect of the spacing ratio on flow-induced vibration and energy harvesting performance is studied,and six spacing ratios are selected for investigation within the range of incoming flow velocity U=1-10m/s.As the spacing ratio increases,the position of vortex shedding shifts from downstream of the oscillating foil to the gap between the cylinder and the foil.As the spacing ratio is relatively small,the oscillating foil is subjected to a stronger flow field effect,the amplitude response is larger and the corresponding frequency distribution is more complex at high reduced velocities.Then,based on the spacing ratio of 1.0,the working condition of energy capture is simulated by setting the harnessing damping ratio.The study found that when U~*≥22.85,the energy harvesting power increases with the increase of the harnessing damping ratio.The optimal harvesting efficiency under each harnessing damping ratio appeared in the"lock-in"region.The influence of spring stiffness and mass ratio is analyzed secondly.The increase of spring stiffness increases the area where the flow-induced vibration response of the oscillating foil transitions from vortex-induced vibration to galloping,the frequency response will have a complex frequency distribution at a small incoming flow velocity when the spring stiffness is high;and the energy harvesting increases with spring stiffness with U≥4m/s.Five different mass ratios are selected for simulation,and the results show that the oscillating foil with a smaller mass ratio could obtain larger amplitude and higher energy capture power at a high incoming flow velocity;and the vibration frequency distribution of the oscillating foil with a larger mass ratio is more regular when the velocity is higher.The highest energy harvesting efficiency appears in the velocity range where the vibration frequency is close to the natural frequency.The research in this paper demonstrates that the flow-induced vibration energy harvesting of the oscillating foil based on cylinder wake flow is a feasible clean energy harvesting method.The system can be started at a relatively flow velocity,and realizing the conversion of wind energy in a wide range of flow velocities which improves the efficiency of clean energy utilization;and providing a basis for the development and application of renewable energy harvesting equipment.